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©2005 Society of Economic Geologists, Inc. Economic Geology 100th Anniversary Volume pp. 891–930 Supplement to Tectonic Setting, Geology, and Gold and Copper Mineralization in Cenozoic Magmatic Arcs of Southeast Asia and the West Pacific STEVE GARWIN, ROBERT HALL, AND YASUSHI WATANABE (Note: Figure and table numbers correspond to those cited in the printed part of the paper) APPENDIX 1 Descriptions of the Geologic Settings and Mineral Deposit Styles for Major Cenozoic Magmatic Arcs of Southeast Asia and the West Pacific Southwestern Kuril intrusions and domes of the Miocene bimodal assemblage. The host rocks of these deposits are Cretaceous to Paleogene sedimentary rocks and Miocene sedimentary and volcanic rocks. These deposits occur mainly as gold-bearing quartzadularia veins in the east-northeasterly strike-slip faults, whereas some of them are disseminated in the host rocks (Watanabe, 1995). The timing of the epithermal gold mineralization ranges from 14 to 4 Ma, with a hiatus from 12 to 8 Ma, which corresponds to the period of the backarc basin volcanism. A few 3 to 1.5 Ma low-sulfidation gold deposits are also located near the present andesitic volcanic front (Yahata et al., 1999). Representative deposits in northeast Hokkaido are Konomai (73.2 t Au, 1,243 t Ag), Sanru (6.7 t Au, 46.4 t Ag), and Itomuka (3,086 t Hg). Small volcanic islands in the middle and northeastern parts of the Kuril arc have not been well explored. The middle and northeastern parts contain polymetallic base metal vein-type prospects of middle and late Miocene age, which are associated with intrusive rocks (Ishihara, 1994). Geologic setting: The Miocene to Recent Kuril magmatic arc extends approximately 2,200 km from the northeastern Kamchatka peninsula to southwestern Hokkaido, where it connects to the Aleutian and northeastern Japan arcs, respectively (Fig. 11; Table 1). The southwestern portion of the Kuril arc is associated with the Kuril backarc basin, which formed before the middle Miocene, due to northeast-southwest rifting (Baranov et al., 2002). The basement rocks of the southwestern Kuril arc consist of a Mesozoic accretionary complex with a cover of Cretaceous and Paleogene sedimentary rocks. Eocene to middle Miocene ilmenite-series granitoids intrude the basement rocks (Ishihara et al., 1998). The volcanism of the southwestern Kuril arc has changed from middle Miocene andesitic activity to middle to late Miocene bimodal basalt and rhyolite, including a period from 12 to 8 Ma with basalt-only volcanism. The andesitic and bimodal volcanic activity migrated trenchward during the middle Miocene (Watanabe, 1995). The middle to late Miocene bimodal and basalt-only volcanism occurred mainly in a northsouth–trending graben perpendicular to the arc trend (Watanabe, 1995). The basalts of the Miocene bimodal assemblage changed from island-arc type at 13 to 11 Ma to backarc basin basalt at 9 to 7 Ma and again changed into island-arc type at 5 to 4 Ma (Ikeda et al., 2000). Since the Pliocene, bimodal volcanism in the backarc has disappeared and andesitic volcanic activity at the volcanic front has become dominant. This Plio-Pleistocene activity was associated with formation of calderas several to ten kilometers in diameter, which erupted large amounts of felsic ignimbrite (Ikeda, 1991). East-northeasterly trending right-lateral strike-slip faults were active during the late middle Miocene nearby the volcanic front of the southwestern Kuril arc due to oblique subduction of the Pacific plate (Watanabe, 1995). This fault movement led to the westward migration and collision of the Kuril forearc sliver with the northeastern Japan arc at southern Hokkaido, forming the present concave joint between the Kuril and northeastern Japan arcs (Kimura et al., 1983). Mineral deposit styles: More than 40 low-sulfidation epithermal gold and mercury deposits and prospects are distributed in northeast Hokkaido at the southwestern Kuril arc (Fig. 11, App. 2). They are associated mainly with rhyolitic Japan (northeastern and southwestern) Geologic setting: The Japan arc extends approximately 1,800 km from southwest Hokkaido to north Kyushu, where it connects to the Kuril and Ryukyu arcs, respectively (Fig. 11; Table 1). The arc has a concave configuration toward the Pacific Ocean, consisting of a north-trending northeast segment and east-trending southwest segment. Presently these segments are bounded by a major fault zone (ItoigawaShizuoka tectonic line), which also marks the boundary between the North American and Eurasian plates (Uyeda, 1991). The Izu-Bonin arc is connected with the Japan arc near the joint between the northeast and southwest segments, and the Pacific and Philippine Sea plates subduct beneath the northeast and southwest segments, respectively. The basement rocks of the Japan arc consist of continental blocks of Permian-Triassic gneiss (the Hida belt, central Japan) and high pressure-temperature schist, and a Jurassic accretionary complex (Isozaki, 1997a, b). Mesozoic and Paleogene I-type granitoids related to oceanic plate subduction intruded into these basement rocks (Ishihara and Sasaki, 1991). The Japan arc was a part of the Eurasian continent until latest Oligocene but was separated from the continent due to backarc spreading mainly along the Japan and Yamato basins during the early Miocene, with about 60º clockwise 1 2 and counterclockwise rotation of the southwest and northeast segments, respectively (Otofuji et al., 1985; Hoshi and Takahashi, 1999). Since the early Miocene, arc volcanism has been active in both segments. This volcanism is divided into rift-related activity including bimodal volcanism of basalt and rhyolite in the backarc during the early-middle Miocene and subduction-related andesite-dacite activity during the late Miocene, Pliocene, and Quaternary (Tsuchiya, 1990, Nakajima et al., 1995; Kimura et al., 2003). Rift-related basaltic activity occurred during the Plio-Pleistocene in northern Kyushu, at the western end of the southwest segment of the Japan arc. This rifting is related to the backarc spreading along the Okinawa trough (Kamata and Kodama, 1999). The tectonic regime of the northeast segment of the arc since the Miocene has changed from early to middle Miocene extension, characterized by arc-parallel normal faulting with rifted basins, to late Pliocene to Quaternary shortening with arc-parallel thrusting and folding, through a late Miocene to early Pliocene transitional regime without significant tectonic deformation (Sato, 1994). The middle Miocene rifting and related bimodal volcanism is best developed in the middle part of the northeast segment. Bimodal volcanism is not clear or mixed with andesite-dacite volcanism in the northern and southern margins of the northeast segment, where the Okhotsk continental block and the Izu-Bonin arc have collided with the Japan arc during the middle Miocene, respectively (Kimura et al., 1983; Amano, 1991. East-northeasterly trending rightlateral strike-slip faulting occurred during the Pliocene in the northern part of the northeast segment due to the westward migration of the frontal Kuril arc (Watanabe, 1990). Significant faulting and folding have not been recognized in the southwest segment of the Japan arc during the Miocene and Pliocene. Since the latest Pliocene, east-trending rightlateral strike-slip faulting has occurred along the Median tectonic line and other tectonic zones, as well as thrusting along the north-northwest–trending Itoigawa-Shizuoka tectonic ine. These tectonic movements are ascribed to the oblique subduction of the Philippine Sea plate beneath the southwest segment of the Japan arc (Itoh et al., 2002) and convergence between the North American and Eurasian plates (Uyeda, 1991), respectively. Mineral deposit styles: Metallic mineral deposits of the Japan arc include middle Miocene Cu-Pb-Zn (-Ag-Au) Kuroko deposits and late Miocene to Pleistocene Cu-Pb-Zn and Au-Ag epithermal deposits (Fig 10; Watanabe, 2002). About 70 Kuroko deposits, including massive gypsum and barite deposits, have been discovered in the 800-km-long northeast segment of the Japan arc (Sato, 1974). These deposits are associated with monogenetic rhyolite volcanism of the middle Miocene backarc bimodal assemblage in a submarine environment. In spite of the wide distribution of the Kuroko deposits in the northeast segment, economic deposits are limited to the middle part of the segment. In particular, productive Kuroko deposits cluster in submarine calderas in the Hokuroku district. Representative deposits in the Hokuroku district are Hanaoka (0.96 Mt Cu, 1.3 Mt Zn, 0.3 Mt Pb), Shakanai (0.1 Mt Cu, 0.3 Mt Zn, 0.1 Mt Pb), Kosaka (0.6 Mt Cu, 1.7 Mt Zn, 0.4 Mt Pb; Ohmoto et al., 1983), and the gold-rich Nurukawa deposit (6.8 t Au, 123 t Ag + Zn + Pb + Cu). 0361-0128/98/000/000-00 $6.00 Some Kuroko-type gypsum deposits are distributed in the backarc in the southwest segment of the Japan arc (Sato, 1974). An Re-Os age of the Wanibuchi deposit in the southwest segment, 18.4 ± 0.6 Ma (Terakado, 2001), is older than the range of ages (15.4–12.4 Ma; Sawai and Itaya, 1993) for Kuroko mineralization in the northeast segment, suggesting that Kuroko-style settings occurred slightly earlier in the southwest segment than in the northeast segment of the Japan arc. Some middle (or early) Miocene epithermal Au-Ag deposits occur in the northeast segment of the Japan arc and are related to felsic volcanism (Watanabe, 2002). These include the Sado deposit (72.7 t Au, 2,278 t Ag), which has characteristics of an intermediate-sulfidation type. Because different sets of mineralization ages, 24.4 to 22.1 Ma (Ministry of International Trade and Industry, 1987a) and 14.5 to 13.4 Ma (Shikazono and Tsunakawa, 1982), are reported for the deposit, the relationship between the Kuroko and epithermal mineralization is not clear. Late Miocene to Pleistocene Cu-Pb-Zn-Ag epithermal and Au-Ag epithermal deposits are mainly distributed in the northeast segments of the Japan arc, associated with calc-alkaline andesite-dacite volcanism in a terrestrial environment. These deposits are mostly of vein type and hosted by transtensional faults. Although there are numerous mineral prospects of late Miocene age, economic deposits were mainly formed during the Pliocene or Pleistocene in an arc setting (Watanabe, 2002). Epithermal deposits during this period are classified into intermediate- or high-sulfidation types, but the high-sulfidation deposits are small (Watanabe, 2002). Representative deposits are the Chitose intermediate-sulfidation (18 t Au, 83 t Ag), Teine high- and intermediate-sulfidation (9 t Au, 130 t Ag), Toyoha polymetallic epithermal (1.8 Mt Zn, 0.5 Mt Pb, 3,000 t Ag, 10 t Au), Takatama intermediate-sulfidation (28.7 t Au, 280 t Ag), and Ashio xenothermal (0.6 Mt Cu) deposits. An epithermal gold province occurs in northern Kyushu, where backarc rifting along the Okinawa trough has extended into the arc. The province contains about 20 low-sulfidation deposits of Plio-Pleistocene age, associated with intermediate to felsic volcanism in and around the Beppu-Shimabara graben (Sawai and Nagao, 2003). These include the Taio deposit (36.0 t Au, 137 t Ag). Izu-Bonin Geologic setting: The north-trending Izu-Bonin arc extends approximately 1,200 km from the Izu peninsula of Honshu Island to the Iwo-jima Islands at 25º N and 142º E in the Pacific Ocean (Fig. 11; Table 1). This magmatic arc is situated along the eastern margin of the Philippine Sea plate due to northwestward subduction of the Pacific plate. It connects to the Japan arc in the north and the Mariana arc in the south. Rift grabens exist in the backarc of the central portion of the Izu-Bonin, and the Ogasawara plateau on the Pacific plate is being subducted beneath the southern margin of the arc (Tamaki, 1985). This arc was located farther southwest relative to Japan when Cenozoic arc magmatism commenced in the middle Eocene, and then the arc moved northeast in response to clockwise rotation and backarc spreading of the Philippine Sea plate (Seno and Maruyama, 1984; Hall et al., 1995). The 2 3 arc probably reached its present position by the middle Miocene and has collided and accreted to the Japan arc at its northern end in the Izu peninsula (Amano, 1991; Takahashi and Saito, 1997). However, some workers (e.g., Hall, 2002) suggest this collision took place as late as the Pliocene. This accretion is inferred to have increased the coupling force between the arc and subducting Pacific plate (Okino et al., 1999). Two stages of arc rifting are recognized, including middle Miocene and latest Pliocene to Quaternary. The middle Miocene rifting occurred in the northern part of the backarc with north-northwest–trending rift axes, which were truncated by northeast transform faults (Yamazaki and Yuasa, 1998). The latest Pliocene to Quaternary rifting is manifested in the central part of the arc by several grabens with northtrending axes located behind the volcanic front (Taylor, 1992). The oldest island-arc rocks in the Izu-Bonin arc are middle Eocene (49–48 Ma) island-arc tholeiite and boninite series basalt to rhyolite. This volcanism continued for more than 10 m.y. and was followed by tholeiitic and calc-alkaline volcanism, which occurred along the arc until 27 Ma. Arc volcanism became inactive during 23 to 20 Ma, when backarc spreading in the Shikoku basin was active. Middle Miocene to Holocene Izu-Bonin frontal arc volcanism is bimodal (basalt and rhyolitedacite; Taylor, 1992), whereas calc-alkaline andesite and dacite characterized the backarc from 12.5 to 2.9 Ma (Ishizuka et al., 1998). Post-2.8 Ma backarc volcanism consists of clinopyroxene-olivine basalt associated with rifting (Ishizuka et al., 1998). The tectonic regime of the Izu-Bonin arc has been extensional, characterized by several stages of normal faulting at least since the Oligocene, except along its northern margin, where the arc has collided with the Japan arc. Accretion of several microcontinental blocks since the middle Miocene has rotated the central part of the Japan arc. This accretion also formed an accretionary prism and thrusts in the Japan forearc (Mazzotti et al., 2002). The Izu block, accreted to the Japan arc at about 1 Ma (Amano, 1991), contains northwesttrending right-lateral and north-northeast–trending left-lateral strike-slip faults that localize epithermal gold deposits. Mineral deposit styles: Metallic mineral deposits along the Izu-Bonin arc include Kuroko and epithermal deposits (Fig. 11). Kuroko-style submarine hydrothermal mineralization is presently recognized at Myojin Knoll, Myojinsho, and in the Sumisu rift of the Izu-Bonin arc (Glasby, 2000). The gold-rich Cu-Zn-Pb Sunrise deposit at Myojin Knoll is estimated to have 9 million tons (Mt) of mineralized material (Iizasa et al., 1999). Epithermal Au-Ag deposits are located in the Izu peninsula at the northern end of the Izu-Bonin arc. These include Seigoshi (16.0 Au, 511 Ag), Toi (12.1 t Au; 94 t Ag), Mochikoshi (4.9 t Au, 104 t Ag), and others. These deposits consist of northwest- or north-northeast–trending, gold-bearing adularia-quartz veins oriented subparallel to regional strike-slip faults. These veins have characteristics of an intermediate- or low-sulfidation type. Mineralization ages vary from 2.5 to 1.4 Ma, which corresponds to a period of bimodal volcanism of basalt and rhyolite-dacite, as well as andesitic volcanism (Ministry of International Trade and Industry, 1987b). (Figs. 2, 10; Table 1). The arc consists of the Ryukyu trench, forearc islands, an active volcanic belt, and the Okinawa trough in the backarc. The Ryukyu arc is related to westward subduction of the Philippine Sea plate beneath the Eurasian plate at a velocity of 6 to 7 cm/yr (Shinjo, 1999). The basement rocks consist of Permian to Cretaceous sedimentary or serpentinite mélange, including blocks of limestone and metamorphic rocks, and Cretaceous to Paleogene sedimentary rocks. These basement rocks are overlain by late Cenozoic sedimentary rocks. Middle to late Miocene ilmenite-series and magnetite-series granitoids intruded the forearc and backarc sides of the northern part of the arc, respectively. This intrusive activity was followed by Pliocene and Quaternary calc-alkaline andesite volcanism, which is associated with rhyolite and dacite in the backarc (Karakida et al., 1992). Paleomagnetic data (Kodama et al., 1995) and locations determined from Global Positioning System (GPS) data (Nishimura et al., 1999) for the northern part of the arc indicate that the forearc has rotated counterclockwise with respect to the backarc part since 2 Ma, resulting in easttrending extension along the Kagoshima graben in south Kyushu. In the central and southern part of the arc, middle and late Miocene high Mg andesite and basalt occur with calc-alkaline andesite (Shinjo, 1999). Since the latest Pliocene, backarc spreading began in the Okinawa trough (Sibuet et al., 1998), which is characterized by bimodal volcanism of basalt and rhyolite (Shinjo and Kato, 2000), seafloor hydrothermal activity and Kuroko-style mineralization (Marumo and Hattori, 1999). Near Taiwan, the arc is characterized by Eocene pyroclastic rocks and andesite flows, Miocene marine siliciclastic rocks and an active submarine volcano (Hutchison, 1989). Northern Taiwan lies at the junction between the Ryukyu and Luzon arcs, where these two arcs started colliding at 10 Ma (Teng, 1996). In this region, Plio-Pleistocene centers of magmatism (2.8–0.2 Ma; Chung et al., 1995) have migrated westward, in part, initiated by the westerly encroachment of the Ryukyu trench and the southwestward opening of the Okinawa trough (Teng et al., 1992). Backarc extension in the Pleistocene led to the emplacement of andesitic to dacitic hypabyssal plugs and flows, dated in the Chinkuashih region at 1.3 to 0.9 Ma (Tan, 1991; Wang et al., 1999). The volcanic rocks overlie a Miocene marine sedimentary rock sequence, similar to that exposed in the Ryukyu arc to the northeast. Mineral deposit styles: The southern Kyushu epithermal gold province in the northern Ryukyu arc contains Plio-Pleistocene low-sulfidation deposits, represented by Hishikari (260 t Au, 208 t Ag), Yamagano, (28.4 t Au, 28.3 t Ag), and Okuchi (22.2 t Au, 17.0 t Ag) with a few high-sulfidation deposits, such as Akeshi (8.9 t Au, 4.7 t Ag), Kasuga (8.8 t Au, 5.0 t Ag), and Iwato (8.1 t Au, 13.7 t Ag), and the Kushikino intermediate-sulfidation deposit (55.9 t Au, 477 t Ag; Fig. 11; Izawa and Watanabe, 2001). These deposits cluster on the western side of the Kagoshima graben (Izawa and Urashima, 1987). Epithermal gold mineralization in the province started with Pliocene high- and intermediate-sulfidation deposits in the west of the province (Kushikino, 3.7–3.4 Ma; Kasuga. 5.5–5.3 Ma; Iwato, 4.7–4.2 Ma, and Akeshi, 3.7 Ma) and has extended eastward with time to form Pleistocene low-sulfidation deposits (Okuchi, 1.6–1.2 Ma; Hishikari, 1.1–0.7 Ma; Ryukyu Geologic setting: The Ryukyu arc extends approximately 1,200 km from southern Kyushu Island in Japan to Taiwan 0361-0128/98/000/000-00 $6.00 3 4 Sudo et al., 2003). This eastward expansion of the metallogenic province followed an eastward shift of the Ryukyu volcanic front and is probably related to the counterclockwise rotation of Kyushu Island (Izawa and Watanabe, 2001). The Kushikino intermediate-sulfidation deposit is associated with an andesitic polygenetic volcano (Izawa and Zeng, 2001), whereas low-sulfidation deposits are associated with rhyolitic or dacitic monogenetic volcanic activity in the backarc (Miyashita, 1975). Magmatic activity related to the high-sulfidation deposits has not been clarified, although these deposits are hosted by late Miocene to early Pliocene andesitic volcanic rocks (Hedenquist et al., 1994). The low-sulfidation deposits in the metallogenic province are composed mostly of adularia-quartz veins with alteration halos of sericite-chlorite at depth and quartz-smectite ± kaolinite near the surface in widespread chlorite or smectite-zeolite alteration zones (Izawa and Urashima, 1987). High-sulfidation deposits are characterized by replacement ores hosted by residual quartz and quartz-alunite-dickite (or kaolinite) alteration zones (Hedenquist et al., 1994). The Chinkuashih high-sulfidation Au-Cu district in northeastern Taiwan has produced more than 92 t Au (Fig. 2, App. 2; Tan, 1991). Orebodies consist of enargite-gold vein systems, hydrothermal breccia pipes, and replacement bodies, which are spatially and temporally associated with Pleistocene dacitic hypabyssal intrusions. Host rocks include the dacitic intrusions and Miocene calcareous and carbonaceous sandstones and shales. Bonanza grades have been reported from many of these orebodies, but in more recent years mine grades averaged approximately 3 g/t Au. The majority of the past production was from the 2-km-long Penshan-Hsumei vein system in the central portion of the district. The Chiufen-Wutanshan intermediate-sulfidation vein system occurs about 1 km west of the high-sulfidation deposits and produced 29 t Au (Tan, 1991). The Tatun district, located 30 km west of Chinkuashih, is characterized by one high-sulfidation system, which was prospected for gold and copper in the past (Yen, 1971). The Neogene component of the arc includes andesitic flows, tuffs, and volcaniclastic rocks. The Mount Pinatubo stratovolcano forms part of the Quaternary portion of the western Luzon arc. Older portions of the arc occur in the Luzon Central Cordillera and include Eocene (?) to Miocene basaltic to andesitic volcanic breccias, volcaniclastic rocks, limestones, shales, and conglomerates (United Nations Development Program, 1987a; Metal Mining Agency of Japan, 1979). In the Central Cordillera, several phases of diorite to tonalite intrusions and their hypabyssal equivalents were emplaced from the early Miocene through the Pliocene (Metal Mining Agency of Japan, 1979, 1983; United Nations Development Program, 1987a; Garcia, 1991). The Kias Creek dike complex in Baguio (Mitchell and Leach, 1991) includes pyroxenehornblende-phyric diabases, lamprophyres, and appinites that contain amphibolite xenoliths of inferred arc basement origin (Paddy Waters, writ. commun., 2004). Three of these dikes indicate Ar-Ar ages that range from 4.6 to 4.0 Ma (Paddy Waters, writ. commun., 2004). Mineralized diatreme breccias are associated with the emplacement of the Balatoc plug in the Baguio district. This magmatism is dated at 1.0 Ma (Metal Mining Agency of Japan, 1983; Cooke et al., 1996). The pre- and postmineralization Plio-Pleistocene quartz diorite and dacite intrusions and diatreme-related pyroclastic rocks in the Mankayan district span the periods 2.2 to 1.8 and 1.2 to 0.9 Ma, respectively (Arribas et al., 1995; Hedenquist et al, 1998). Plio-Pleistocene ages are reported for mineralized diorite intrusions at Sto. Thomas II (Sillitoe, 1989; Baluda and Galapan, 1993) and Black Mountain (Waters, 2004) near Baguio, and at Tawi-Tawi (Wolfe, 1981) in the southeastern portion of the Central Cordillera. Mineral deposit styles: Porphyry copper-gold deposits and related high- and intermediate-sulfidation epithermal systems are abundant in the Luzon Central Cordillera and western Luzon arcs (Fig. 13, App. 3). These deposits are predominantly centered about Neogene to Pleistocene quartz diorite-diorite intrusions hosted by coeval volcanic suites. The Central Cordillera hosts the intermediate-sulfidation gold lode systems of Acupan, Antamok, and Itogon, and the Sto. Thomas II porphyry in the Baguio district, where an estimated 800 t Au have been produced (Mitchell and Balce, 1990). In Acupan, several major gold-bearing quartz vein systems, 0.65 Ma in age (Cooke et al., 1996), occur adjacent to and within the Pleistocene Balatoc diatreme and comprise sheeted veins, stockworks, and the high-grade “GW” breccia bodies (Cooke and Bloom, 1990). The Itogon intermediatesulfidation gold-bearing quartz vein deposit occurs along the eastern periphery of the Balatoc diatreme and is the eastward extension of the Acupan system. The total length of the combined deposits approximates 4 km. In Antamok, major quartz vein systems and associated stockworks are hosted by andesitic agglomerate and intercalated lava flows. Emplacement of the Antamok and Acupan-Itogon vein systems was controlled by tensional fractures developed along regional east-northeast– and northwest-trending conjugate strike-slip faults (Fernandez and Damasco, 1979). The average global grades of these three deposits are inferred to range from 4 to 6 g/t Au, which includes past production from high-grade (>10 g/t Au) lodes. Luzon Geologic setting: The Luzon arc, as defined in this paper, represents a composite arc system that extends 1,200 km southward from the Coastal Range of southeastern Taiwan through the volcanic islands north of Luzon, the Luzon Central Cordillera, and the Western Luzon arc, terminating in the vicinity of southern Marinduque Island (Fig. 12; Table 1; Cardwell et al, 1980; Bureau of Mines and Geo-Sciences, 1982; Mitchell and Leach, 1991). The arc has been active from the Oligocene to the present and is presently underlain by an east-dipping Benioff zone related to the Manila trench (Divis, 1980). The subduction of the Scarborough Seamounts beneath northern Luzon during the Plio-Pleistocene probably led to extinction of volcanism in the Central Cordillera and the volcanic islands north of Luzon from ~4 to 2 Ma and eastward migration of magmatism from ~2 Ma to the Holocene (Fig. 7; Yang et al., 1996). Cretaceous ophiolitic basement is exposed in the Zambales region of the western Luzon arc. The United Nations (United Nations Development Program, 1987b) infers a similar sequence to form the foundation for the Central Cordillera. 0361-0128/98/000/000-00 $6.00 4 5 The Lepanto high-sulfidation enargite-gold deposit, the Victoria and Teresa intermediate-sulfidation vein systems, and the Far South East and Guinaoang porphyry deposits occur in the nearby Mankayan district, which contains a minimum of 700 t Au in combined past production and current resources. There is a clear genetic association between porphyry and epithermal styles of mineralization in Mankayan. The Far South East porphyry formed below and coeval to Lepanto at 1.4 to 1.3 Ma, both deposits associated with the emplacement of quartz diorite porphyry; the Victoria vein system formed at ~1.15 Ma, as the hydrothermal system waned (Hedenquist et al, 1998, 2001). At Lepanto, residual quartz alteration of dacitic wall rocks host east-trending enargite-gold branch veins and stratiform lodes localized around the intersection of the steeply dipping northwest-striking Lepanto fault and the gently dipping unconformable base of a Pliocene dacitic pyroclastic sequence. The dacitic rocks form part of the Mankayan diatreme-dome complex (Garcia, 1991; Baker, 1992). The Victoria gold-base metal-quartz vein system is located <1 km southwest of Far South East, at a similar level to Lepanto. The veins average 7.3 g/t Au and form an east-trending tensional array localized by right-lateral movement on mine-scale strike-slip faults (Claveria et al., 1999). The Teresa intermediate-sulfidation gold deposit, discovered in 2002, lies to the southwest of Victoria and extends south to the Nayak vein system. It contains an estimated resource of 7.3 Mt at ~5.3 g/t Au (Waters, 2004). Both the Mankayan and Baguio districts occur in zones of structural complexity near major north-northwest–trending fault splays of the sinistral strike-slip Philippine fault (Fig. 13). The gold-rich Dizon copper porphyry deposit in the Zambales region and the Tayson copper-gold porphyry deposit in the Batangas area occur in the western Luzon arc. Both porphyry deposits are located in Miocene to Pliocene windows in Quaternary volcanic cover. The Chimei copper-gold porphyry system in the Coastal Range in eastern Taiwan is inferred to lie in the northern extension of the Luzon arc. Early Miocene ages (22 and 19 Ma) are indicated for andesite from the Chimei porphyry deposit (Chen, 1975, in Hutchison, 1989). Mineral deposit styles: This K alkaline province includes the Didipio district on the southeastern margin of the Palali intrusion and the Isabella district within the Cordon syenite complex (Fig. 13). Significant resources occur in the Dinkidi copper-gold porphyry deposit (120 t Au, 0.5 Mt Cu) in Didipio and the Marian intermediate-sulfidation epithermal gold mine and nearby porphyry copper-gold system in Isabella. Dinkidi is hosted by a composite monzonite stock that has been intruded by a highly mineralized syenite pegmatite dike, which forms a gold-rich (5–15 g/t Au) core (Wolfe et al., 1999). The spatial extent of quartz stockwork veins and flanking feldspar-destructive sericitic and argillic alteration zones for the deposit is more restricted than recorded in the calc-alkaline porphyry systems elsewhere in Luzon. The Runruno intermediate-sulfidation gold deposit and the Pao high-sulfidation enargite-gold occurrence (Kavalieris and Gonzalez, 1990) are also located in the Cordon arc. Philippine Geologic setting: The Philippine arc (Cardwell et al., 1980) or the Pacific Cordillera extends more than 1,000 km from Camarines in southern Luzon to the Pujada peninsula in southeastern Mindanao (Fig. 12; Table 1). The arc occurs close to the sinistral Philippine fault. Geologic basement to the arc consists of Cretaceous ultramafic rocks and Paleogene andesitic volcanic, volcaniclastic, marine siliciclastic, and carbonate rocks (Bureau of Mines and Geo-Sciences, 1982). The arc includes segments that have been active at different times between the Oligocene and Quaternary (Divis, 1980; United Nations Development Program, 1987b). Oligocene-Miocene basaltic breccias and turbidites are overlain by Neogene andesitic to dacitic volcaniclastic rocks, lavas, and calcareous siliciclastic rock units in northeastern Mindanao (United Nations Development Program, 1987b). A foliated to massive trondjhemite dome (Paracale granodiorite of Frost, 1959), Miocene diorite and andesite porphyry, and Pliocene dacite porphyry occur in Camarines (United Nations Development Program, 1987c). The diorite and andesite porphyry intrusions in the Leyte, Surigao, Co-O, and Masara areas of east Mindanao are Miocene in age (Mitchell and Leach, 1991). Miocene andesitic volcanic rocks, volcaniclastic rocks, and intrusions also characterize the Leyte sector of the arc. In eastern Mindanao, late Pliocene to Quaternary andesitic volcanoes, associated eruptive products and porphyritic stocks occur near Surigao and Lake Leonard in the Masara region (Mitchell and Leach, 1991; Sajona et al., 1997). Pleistocene to Recent (active) volcanoes characterize arc portions in Camarines, southeastern Luzon, and Leyte (Divis, 1980). The Philippine arc presently lies above a west-dipping Benioff zone related to the Philippine trench. However, pre-Pliocene arc magmatism is not related to subduction at this trench, as the trench is a young feature (Hamilton, 1979) and the subducting slab only reaches depths of 150 to 250 km (Gudmundsson and Sambridge, 1998). The source of this pre-Pliocene magmatism is probably related to eastdirected subduction on the west side of the Philippines. However, the subduction history in the Philippines is complex and most likely involved the formation of small intraPhilippines ocean basins within an overall strike-slip zone. Cordon Geologic setting: Surface exposures of alkaline igneous rocks in north-central Luzon define two discrete regions, the Cordon syenite complex and the Palali intrusion, which lie at the southern end of the Cagayan rift basin. The basement to the Cagayan basin consists of Cretaceous to Paleogene calcalkaline plutonic, volcanic, and volcaniclastic rocks (Table 1). K alkaline magmatism occurred in the late Oligocene and early Miocene, as indicated by K-Ar ages of ~25 Ma for the Cordon Syenite Complex (Knittel, 1983) and 25 to 17 Ma for the Palali intrusion (Metal Mining Agency of Japan, 1977). The emplacement of these intrusive complexes may be related to intraplate magmatism initiated by subduction beneath Luzon, as expressed by Divis (1983) and Knittel and Cundari (1990), but there is no agreement as to the polarity. Other possible sources of the alkaline magmatism include delayed partial melting of a relict subduction slab, as postulated for southeastern Papua New Guinea by Johnson et al. (1978) and Smith and Milsom (1984) or intra-arc extension. 0361-0128/98/000/000-00 $6.00 5 6 The present Philippine fault is mechanically linked to Pliocene to Recent subduction along the Philippine trench, but the Philippine fault predates this subduction, which implies a complex plate boundary during the Neogene. The geology of the islands indicates a long history of strike-slip faulting (Rutland, 1968; Karig et al., 1986). Mineral deposit styles: The gold districts of Paracale, Sta Elena-Tabas, and Nalesbitan in the Camarines Norte, and Surigao, Masara, and the Diwalwal-Compestela areas in eastern Mindanao are characteristic of the gold districts in the Philippine arc (Fig. 13). Several historic intermediate-sulfidation lodes in the Paracale area (e.g., Longos mine) occur along the contact between the Paracale trondjhemite and serpentinized ultramafics (Frost, 1959). Gold in the Paracale and Sta Elena-Tabas areas are associated with intermediate-sulfidation lodes (United Nations Development Program, 1987c), which contain tellurides at Exciban (James and Fuchs, 1990), and the Larap (Mantanlang) porphyry Cu-Mo-Au deposit (Sillitoe and Gappe, 1984). Nalesbitan is a small high-sulfidation gold deposit hosted by andesitic volcanic rocks (Sillitoe et al., 1990). In central Samar, Kuroko-type massive sulfide deposits at the Bagacay mine and Sulat deposit contain significant gold in addition to copper and silver (Bureau of Mines and Geo-Sciences, 1986). Gold deposits and prospects in eastern Mindanao consist of intermediate-sulfidation lode and stockwork styles (Placer, Co-O, Diwalwal-Compestela, and Masara), disseminated sedimentary rock-hosted and replacement styles (Siana and Hijo), and porphyry Cu-Au deposits (Boyongan, Kingking, Amacan, and Mapula). Descriptions of the majority of these deposits are included in Mitchell and Leach (1991), with the exception of Boyongan and Bayugo, which were recently discovered near Surigao. The Boyungan deposit is hosted by a K silicate altered, calc-alkaline dioriteporphyry composite stock emplaced within a sequence of Neogene(?) andesite, pyroclastic rocks, and basaltic flows (Josef, 2002). The deposit is concealed beneath a more than 50-m-thick, postmineralization cover sequence of Quaternary andesitic flows, laharic breccia, tuff, mudstone, and conglomerate. The Boyungan and Bayugo porphyry systems formed at ~2.6 to 2.3 Ma, approximately coeval to the development of the Siana sedimentary rock-hosted deposit (Waters, 2004). Boyongan is inferred to have been uplifted during the late Pliocene-Pleistocene and to have formed a prominent topographic high, on the basis of an unusually deep supergene oxidation profile that extends 300 to 500 m beneath the base of the Quaternary cover rock sequence (Josef, 2002; Waters, 2004). This relationship indicates that shortly after Boyongan formed, it was uplifted by at least 1 km in the Plio-Pleistocene to partly expose the K silicate-altered core of the system and then downdropped as much as 500 m in a pull-apart basin, developed by movement along strands of the sinistral Philippine fault system, prior to Quaternary volcanism, which concealed and preserved the deposit. In northeastern Mindanao, the westward-younging and progressive compositional changes of intrusive centers from ~4.5 Ma to Recent (Sajona et al., 1997), and the formations of porphyry deposits at ~2.5 Ma, could be related to west-directed subduction, if initated at 6 to 5.5 Ma (Paddy Waters, writ. commun., 2004). 0361-0128/98/000/000-00 $6.00 Masbate-Negros Geologic setting: This arc assemblage consists of two overlapping arcs of different ages. The combined arc system extends 400 km and includes eastern Panay (Fig. 12; Table 1). The arc system is terminated against the Philippine fault in the north and abuts the Sulu-Zamboanga arc to the south. Cretaceous basement includes marine sedimentary rocks and pillow basalts, exposed in southeast Negros (Hamilton, 1979) and serpentinized ultramafic rocks in northeastern Masbate (Mitchell and Leach, 1991). In the older western arc, Eocene to Oligocene andesitic to dacitic volcanic and clastic rocks host a Miocene dacitic diatreme complex at Bulawan in southwest Negros and middle Miocene dioritic intrusions in northeast Masbate (Mitchell and Leach, 1991). In the younger eastern arc, middle Miocene to Pliocene andesite flow breccias, volcaniclastic rocks and conglomerates are overlain by late Pliocene andesitic volcanic rocks and Quaternary andesite to basalt stratovolcanoes (Bureau of Mines and Geo-Sciences, 1982; United Nations Development Program, 1987d). The two arcs are the product of subduction beneath Negros but the polarity of the older arc is not clear; it has been interpreted to be situated above a west- (Sajona et al., 1997) or east-dipping (Holloway, 1982; Hall, 2002) subduction zone. The younger arc is probably the product of east-dipping subduction at the Negros trench, which currently appears to be inactive or almost so (Cardwell et al., 1980) and associated with a slab that extends to a depth of about 100 km (Gudmundsson and Sambridge, 1998). Mineral deposit styles: The western Masbate-Negros arc contains the Masbate intermediate-sulfidation stockwork gold mine (62 t Au, Aroroy district) in northeastern Masbate, and the Bulawan intermediate-sulfidation gold deposit and goldpoor Sipalay and Hinobaan porphyry Cu ± Mo deposits in southwest Negros (Fig. 13; Sillitoe and Gappe, 1984). Approximately 40 t Au were exploited from underground lode mines in the Aroroy district prior to World War II (Mitchell and Leach, 1991). Open-pit reserves established in 1980 averaged 2.3g/t Au. Gold mineralization is associated with Miocene andesite to dacite clastic rocks at Masbate and a similar-aged dacitic diatreme complex at Bulawan (Mitchell and Leach, 1991; Philex, 1995). In contrast, the gold-poor porphyry systems are considered to be Eocene to Oligocene in age (Bureau of Mines and Geo-Sciences, 1986; Singer et al., 2002). The eastern Masbate-Negros arc includes geothermal areas and several andesite-hosted silica bodies, which are inferred to represent the upper levels of high-sulfidation epithermal systems (United Nations Development Program, 1987d). There may be potential for concealed porphyry-style mineralization at depth. Pliocene(?) conglomerates with pyriticquartz and acid-sulfate–altered clasts indicate a minimum age for the high-sulfidation systems in southeast Negros (Mitchell and Balce, 1990). Sulu-Zamboanga Geologic setting: This arc extends approximately 400 km westward from the Semporna peninsula in eastern Sabah through the Sulu archipelago to the Zamboanga peninsula, where it is truncated by the western Cotobato and the 6 7 Masbate-Negros arc systems (Fig. 12; Table 1). The Zamboanga peninsula can be subdivided into two segments by the Sindangan-Cotobato-Daguma lineament (Cotabato fault zone of Pubellier et al., 1991, and Rohrlach et al., 1999), which has been interpreted as the accretionary boundary between the Cotabato island arc to the northeast and a continental fragment to the southwest (Jimenez et al., 2002). The juxtaposition of these two terranes commenced in the middle Miocene, with collision still active today, according to Rangin et al. (1999). The source of the interpreted continental fragment is not clear nor is its existence documented conclusively. Pre-Tertiary granitoids and metasedimentary rocks form the basement in the southwestern part, and Cretaceous serpentinized ultramafic rocks and metasedimentary rocks comprise the basement in the northeastern part, of the Zamboanga peninsula (Hamilton, 1979; Jimenez et al., 2002). The Sulu and Zamboanga sectors of the arc are composed generally of Neogene to Quaternary andesitic volcanics and sedimentary rocks. Plio-Pleistocene subaerially erupted andesitic volcanic rocks and hypabyssal intrusions occur in the northeastern part of Zamboanga, with Miocene marine siliciclastic and carbonate rocks covering much of southwestern Zamboanga; the suture between the two terranes is marked by a Neogene mélange complex (Jimenez et al., 2002). In the Semporna and Dent peninsulas of Sabah there are Neogene calc-alkaline and K-rich calc-alkaline basalts, andesites, and dacites above a Cretaceous to Paleogene basement of chert, basalts and ultramafic rocks (Kirk, 1968; Hutchison, 1989; Yan, 1990; Chiang, 2002). Arc activity terminated in the late Pliocene and intraplate basalts were erupted in the Pleistocene at a number of small centers. Chiang (2002) suggests that geochemical variation in the Mio-Pliocene volcanic rocks indicates northwest-directed subduction. The change to intraplate basic magmatism during the Pleistocene indicates sampling of a new and different mantle source. The polarity of subduction is not clear because there is no significant seismicity beneath the Sulu arc. Older northwestdipping subduction of the Celebes Sea is suggested to have reversed to southeast-dipping subduction of the Sulu Sea on the north side of the Sulu arc, which remained active until the late Pleistocene (Hamilton, 1979; Hutchison, 1989) due to collision of the Cagayan volcanic arc and Palawan (Rangin et al., 1990). However, in Sabah, where the Sulu arc can be traced onshore into the Dent-Semporna arc, there is no evidence for southeast-directed subduction on the north side of the arc. Hall and Wilson (2000) and Hall (2002) suggested that after the Cagayan arc collision, the Celebes Sea began subducting in a northwest direction beneath the south side of the Sulu arc and this interpretation is favored by geochemical evidence from Sabah (Chiang, 2002). Mineral deposit styles: Gold systems are localized in the Zamboanga and Semporna segments of the arc (Figs. 12–13), but no large deposits have been found. Gold occurrences include alluvial deposits, small-scale mining centers, and several prospects. In Zamboanga, more than 12 precious and base metal deposits and prospects of Neogene to Pleistocene age occur proximal to the Cotabato fault zone (Jimenez et al., 2002). These mineralized systems include intermediate-sulfidation veins and stockworks (e.g., Sibutad), porphyry copper prospects (e.g., Labangan), and gold-rich volcanic-associated 0361-0128/98/000/000-00 $6.00 massive sulfide deposits (e.g., Canatuan and Malusok). Host rocks include intermediate volcanic and volcaniclastic rocks and coeval intrusions for the porphyry and epithermal styles of deposits and siliciclastic sedimentary rocks and schists for the massive sulfide deposits. The Sibutad epithermal vein system is the largest gold resource discovered to date (23 t Au) and contains hydrothermal breccia bodies, silica sinter deposits, and alteration types indicative of shallow- to near-surface development during the Pleistocene (Jimenez et al., 2002). In the Semporna peninsula, a high-sulfidation system at Nagos and intermediate-sulfidation quartz-gold lodes at Bt. Mantri are hosted by andesite to dacite volcanic and volcaniclastic rocks and hypabyssal plugs of inferred Pliocene age (Kirk, 1968; Yan, 1990). Mineralization styles in both Nagos and Bt. Mantri are interpreted by Yan (1990) to have developed in the upper levels of epithermal systems. Cotabato-Central Mindanao Geologic setting: This section describes two arcs, the Cotabato arc to the southwest and the Central Mindanao arc to the northeast (Fig. 12; Table 1). In southern Mindanao, the boundary between these two arcs is marked by the Cotabato fault zone. The Cotabato arc includes the Daguma and Sarangani regions and is inferred to be the northern extension of the Sangihe arc. The Cotabato fault zone has been interpreted as the onshore extension of the Molucca Sea collision zone (Pubellier et al., 1991), but there is no evidence in Mindanao for the northward continuation of the Halmahera arc, and the Molucca Sea collision zone may terminate at the Cotabato fault, which acted as a strike-slip fault during the Neogene (Hall, 1996, 2002). Toward the northwest, this fault zone is obscured by a sequence of Quaternary flood basalts, basalt to dacite stratovolcanoes, and the Cotabato sedimentary basin. The Central Mindanao arc is poorly defined, however, the arc is bound by the Cotabato fault and the Cotabato basin to the southwest and the Agusan-Davao trough to the east. The combined arc assemblage extends more than 350 km in a northerly direction across southwest and central Mindanao. In the Cotabato arc, Paleogene metavolcanic and metasedimentary rocks are overlain by Miocene marine clastic and carbonate rocks and intruded by an early to middle Miocene diorite batholith and andesite to dacite hypabyssal stocks (Bureau of Mines and Geo-Sciences, 1982). Plio-Pleistocene andesitic flows, pyroclastic rocks and intrusions, and limited Quaternary dacite-andesite volcanic rocks characterize the northwestern and southeastern portions of the onshore part of the arc. The Central Mindanao arc contains a sequence of Oligocene to middle Miocene basalts, volcaniclastic and carbonate rocks, and late Miocene andesite to basalt volcanic and marine clastic rocks locally intruded by Neogene diorites (Bureau of Mines and Geo-Sciences, 1982; Sajona et al., 1997). Active Quaternary basaltic and lesser andesitic volcanoes and their eruptive products cover much of the region. The central portion of Central Mindanao is underlain by fault-bound slivers of Cretaceous (?) ultramafic rocks (Sajona et al., 1997). The Cotobato trench is characterized by a shallow, northeast-dipping Benioff zone, which is inferred to have developed in recent times (Cardwell et al., 1980; Hutchison, 1989) and is 7 8 not related to pre-Quaternary arc development. The east-dipping Molucca slab, which extends to about 600 km beneath Mindanao, is inferred to have played a major role in Neogene magmatism in both the Cotobato and Central Mindanao arcs. The Cotobato arc may continue to the north as the MasbateNegros arc, however, reconstruction of a continuous volcanoplutonic arc across the Sulu-Zamboanga arc is uncertain. Mineral deposit styles: The southern portion of the Cotobato arc includes porphyry Cu-Au, skarn and epithermal gold occurrences and prospects associated with Neogene dioritic stocks to hypabyssal dacite porphyry bodies and diatremes locally (Fig. 13; Sillitoe and Gappe, 1984). The Tampakan highsulfidation epithermal and/or porphyry Cu-Au deposit (270 t Au, 6.8 Mt Cu) occurs within the eroded flanks of a Pliocene (?) andesitic stratovolcano that lies unconformably on a northerly trending ramp anticline in the hanging wall to a regional east-directed thrust fault (Rohrlach et al., 1999). A synmineralization diorite porphyry dike is dated at 3.2 Ma (U/Pb by laser ablation ICP-MS; R. Loucks, pers. commun., 2002). Enargite-bearing, high-sulfidation mineralization and advanced argillic alteration overprints the porphyry system from surface to depths of about 500 m, with relict K silicate alteration zones present at 600 m below surface (Rohrlach et al., 1999). Small-scale mining centers are located at T’boli in South Cotobato, Tampakan in the Sarangani Range, and elsewhere in southern Mindanao. Gold is recovered from intermediate-sulfidation quartz veins hosted by Miocene volcanic and volcaniclastic sequences. Mitchell and Leach (1991) cited widespread epithermal mineralization in the Sarangani Range, which lies in the southeastern part of the Cotobato arc. Small-scale mining near Bukidnon is associated with narrow quartz veins hosted in phyllites and ultramafic rocks (Mitchell and Leach, 1991). The relationship of these veins to the Central Mindanao arc, if any, is unclear. the northern portion of the Sangihe arc through the northern arm of Sulawesi and into the neck of Sulawesi, where it ends in the sinistral Palu fault (Fig. 14; Table 1; Hamilton, 1979). The western portion of the arc overlies Sundaland continental crust and Cretaceous to Eocene metamorphic rocks, which are intruded by late Miocene to Pliocene granitoids (Kavalieris et al., 1992). These rocks are overlain unconformably by Eocene to Oligocene marine basalt to andesite and sedimentary rocks that form part of an oceanic arc to the east of the Marisa region (Carlile et al., 1990; Kavalieris et al., 1992). Geochemical and isotopic data from northwestern Sulawesi support the inferred transition from continental- to oceanic-arc settings from west to east and indicate the presence of an underthrust fragment of the Australian continent that extends from the western edge of North Sulawesi through the northern and central parts of west Sulawesi (Elburg et al., 2003). The early to middle Miocene portion of the arc consists of andesitic to dacitic volcanic and volcaniclastic rocks and sedimentary rocks intruded by diorite, quartz diorite, granodiorite, and their subvolcanic porphyritic equivalents in the Gorontalo, Kotamobagu, and south Sangihe areas (Carlile et al., 1990; Kavalieris et al., 1992). A Pliocene rhyodacitic pyroclastic sequence and flow dome complex characterizes the Gunung Pani area in Marisa (Kavalieris et al., 1990; Pearson and Caira, 1999). Quaternary andesitic stratovolcanoes define the arc from north of the Kotamobagu area through Sangihe Island. Major northwesterly trending faults influence the distribution of volcanic and sedimentary rock successions in north Sulawesi. The movement along these faults is oblique-slip, with arc-parallel extension indicated by the progressive down-tothe north movement of the fault blocks located north of Kotamabagu (Carlile et al., 1990). Mineral deposit styles: Gold and copper deposits in the north Sulawesi-Sangihe arc commonly lie <10 to 20 km from major northwesterly trending arc-transverse oblique-slip faults (Figs. 8, 14). Many of these deposits are hosted by early to middle Miocene andesitic volcanic rocks intruded by hypabyssal intrusions. West of Marisa, the western sector of the arc has a continental affinity and is characterized by alluvial gold derived from small orogenic lodes hosted by metamorphic basement (Kavalieris et al., 1992). The Gunung Pani disseminated and stockwork intermediate-sulfidation gold deposit (41 t Au) is controlled by north-northeast– and northeast-oriented faults in a rhyodacitic dome complex built upon continental basement along the margin of Sundaland (Kavalieris et al., 1990). The deposit is 3.3 to 3.1 m.y. old (Ar-Ar; Pearson and Caira, 1999) with gold contained in siliceous limonitic and quartz-adularia lined fractures and mosaic quartz breccias (Carlile et al., 1990; Kavalieris et al., 1990). The Gorontalo region hosts porphyry copper-gold deposits in the Tombulilato district, the Bolangitang intermediate-sulfidation epithermal prospect, and the Motombato high-sulfidation epithermal system and contains >140 t gold and substantial copper resources (App. 4). These Pliocene systems (2.9–2.4 Ma; Perello, 1994) are hosted by Miocene volcanic rocks and overlying dacite to rhyolite, which are intruded by quartz diorite stocks (Lowder and Dow, 1978). The Tombulilato district lies ~10 to 20 km from a major northwesterly oriented, arc-transverse dextral-fault zone (Pearson and Caira, 1999). Other Philippine arcs Additional Cenozoic magmatic arcs of the Philippines include the Oligocene arcs of the Sierra Madre in central Luzon and the northeast Luzon-Polillo-Catanduanes in eastern Luzon (Fig. 12; Mitchell and Leach, 1991). Epithermal veins, porphyry copper, skarn, and gold-bearing massive sulfide prospects and alluvial gold workings occur in the East Rizal region of the Sierra Madre arc. Gold-bearing, Besshi-type massive sulfide prospects exist in eastern Bicol and small epithermal veins characterize prospects in Catanduanes Island. In central Cebu, quartz-diorite porphyry intrusions, volcanic and volcaniclastic rocks of probable Cretaceous age host the gold-bearing Atlas porphyry Cu-Mo deposits (Sillitoe and Gappe, 1984). Cretaceous quartz diorite bodies also occur in Bohol, but these intrusions lack significant mineralization (Bureau of Mines and Geo-Sciences, 1982). Miocene andesitic volcanics occur on both islands and may be linked via a paleoarc system. Alternatively, the Bohol arc may extend north beneath northwestern Leyte, as proposed by Mitchell and Leach (1991). North Sulawesi-Sangihe Geologic setting: The Miocene to Recent North SulawesiSangihe magmatic arc extends approximately 1,200 km from 0361-0128/98/000/000-00 $6.00 8 9 In the Kotamobagu region, intermediate-sulfidation stockwork veins in andesitic volcanic and volcaniclastic rocks at Lanut, Mintu, and Doup, and silicified middle Miocene limestone at Lobongan in the Ratatotok district, support smallscale mining activities. The north- to northeast-trending intermediate-sulfidation vein systems at Lanut and nearby high-sulfidation lodes lie within a northwesterly corridor of mineral prospects that extends more than 30 km across the hinge portion of north Sulawesi. The Toka Tindung intermediate-sulfidation vein system (2.4 Ma; Moyle et al., 1997) in northeastern Sulawesi is overlain by a Quaternary ash cover. Host rocks consist of Neogene andesitic volcanic and volcaniclastic rocks that overlie siliciclastic sedimentary rocks. The main Toka Tindung and satellite deposits (35 t Au) form a series of en echelon, north-trending lodes that lie in a northwest-oriented structural corridor (Wake et al., 1996). The sedimentary rock-hosted Mesel gold deposit in the Ratatotok district (62 t Au) has many similarities to Carlintype gold deposits in Nevada (Turner et al., 1994; Garwin et al., 1995). In Mesel, most of the ore is controlled by steeply dipping faults and is hosted in a decalcified, dolomitized, and silicified middle Miocene carbonate sequence adjacent to, and beneath, a premineralization, porphyritic andesite laccolithic intrusion. The Taware porphyry Cu-Au prospect and the Bawone-Binebase high-sulfidation system on south Sangihe Island are inferred to be of Miocene age (Carlile et al., 1990). Neogene diorite to granodiorite bodies intrude the volcanic rock sequences and are associated with porphyry Cu-Au(Mo) prospects on Bacan Island and gold prospects in the northern part of the western arm of Halmahera Island. Volcanic activity has ceased at the southern end of the arc, and the active volcanic arc moved west during the Pliocene (Hall et al., 1988b) and is now built on the western margin of the Neogene arc. Mineral deposit styles: A porphyry Cu-Au prospect occurs at Kaputusan on Bacan Island, where it is associated with anomalous molybdenum and bismuth (Fig. 14; van Leeuwen, 1994). This small resource is centered in a Neogene quartz diorite intrusion in pre-Miocene volcanic host rocks (Carlile and Mitchell, 1994; Malaihollo and Hall, 1996). The Gosowong intermediate-sulfidation bonanza vein system in the northwestern arm of Halmahera Island contains nearly 27 t of gold at an average grade of 27 g/t (Olberg et al., 1999). The steeply east dipping vein lies adjacent to a northwest-trending fault (Research Information Unit, 1997) that forms part of a major northwest-oriented topographic lineament that extends through the western arm of Halmahera. The deposit is hosted by a Neogene sequence of andesitic to dacitic volcanic rocks and subordinate volcaniclastic rocks. The age of mineralization is constrained to lie between 2.9 to 2.4 Ma (Olberg et al., 1999). The recently discovered Kencana and Toguraci intermediate-sulfidation vein systems lie 1 km south and 2 km southwest of Gosowong, respectively. Kencana, the larger of the two deposits, contains 70 t of gold at an average grade of 41 g/t in a quartz vein breccia (indicated plus inferred categories; Mining News, 2004). Kencana is hosted by a northwest-trending, 35° to 55° northeast-dipping, fault within a sequence of andesitic volcanic and volcaniclastic rocks (IAGI, 2004). Other mineralization in the area includes intermediate-sulfidation epithermal and porphyry styles (Olberg et al., 1999). Small intermediate-sulfidation veins occur on Obi Island, hosted in part by andesitic peperites (N. White, writ. commun., 2004). Halmahera Geologic setting: This Neogene to Recent arc sweeps across the western arm of the Halmahera Islands and includes Bacan and Obi Islands (Fig. 14; Table 1). The modern arc extends 400 km from near the Philippine trench to the western extension of the Sorong fault. The basement to the arc consists primarily of Cretaceous-Paleocene ophiolite in Halmahera, Bacan, and Obi (Hall et al., 1991), although there are Mesozoic and probable Precambrian gneiss and schist exposed on Bacan (Hamilton, 1979; Malaihollo and Hall, 1996). The Halmahera region has a long history of arc activity. The ophiolitic basement was formed in an intra-oceanic arc (Ballantyne, 1992) and is overlain in Halmahera and Obi by products of a Late Cretaceous arc and in Halmahera, Bacan, and Obi by an Eocene to Oligocene arc (Hall et al., 1988a, b, 1995; Ali and Hall, 1995; Malaihollo and Hall, 1996). These arcs formed as the result of subduction at the margin of the Philippine Sea plate in an intra-oceanic setting, and arc activity was terminated between the late Oligocene and early Miocene by collision with the north Australian margin (Hall, 1996). During the middle Miocene, there was little or no arc activity and platform carbonates were deposited over a large area and arc activity resumed in the late middle Miocene. All these rocks form the basement to the Neogene Halmahera arc, which was active from about 11 Ma between Obi in the south and Morotai at the north end of the island chain (Baker and Malaihollo, 1996). The active arc shows geochemical evidence of a continental crustal contribution to magmas on Bacan (Morris et al., 1983) and a similar contribution can be identified in the Neogene lavas on Bacan (Forde, 1997), which indicates movement of Australian continental fragments along strands of the Sorong fault, as first suggested by Hamilton (1979). 0361-0128/98/000/000-00 $6.00 Medial New Guinea Geologic setting: New Guinea can be divided into four major structural-stratigraphic belts, from south to north: (1) the stable northern margin of the Australian craton (Fly platform), (2) Papuan fold belt, (3) New Guinea mobile belt, and (4) allochthonous Paleogene volcanic island arcs accreted in the Miocene (Fig. 15; Dow, 1977; Hamilton, 1979; Pigram and Davies, 1987; Rogerson and McKee, 1990; Hall, 2002). The suture zones between the accreted island arcs and mobile belts are typically marked by craton-directed overthrusts of Paleogene ophiolite and mélange (Dow, 1977; Hamilton, 1979). The late Miocene to Pleistocene medial Irian Jaya magmatic arc of Carlile and Mitchell (1994) lies within the Papuan fold belt, where south-directed compressional tectonics have led to localized deformation, crustal thickening, and block uplift during the Plio-Pleistocene to Recent (Hamilton, 1979; Weiland and Cloos, 1996; Hill and Raza, 1999). The medial New Guinea magmatic belt, as defined in this paper, extends more than 1,500 km along the central crest of New Guinea, includes the Quaternary stratovolcanoes near Bosavi, and continues to the southeast through the Owen Stanley thrust belt to the Papuan peninsula and nearby 9 10 D’Entrecasteaux Islands (Dow, 1977; Rogerson and McKee, 1990; McDowell et al., 1996). The basement consists of a thick sequence of Paleozoic sedimentary rocks in Irian Jaya and Paleozoic metamorphic rocks and Permo-Triassic granite overlain by Mesozoic siliciclastic rocks in Papua New Guinea (Hamilton, 1979; Dow and Sukamto, 1984; Pigram and Davies, 1987; Hill and Raza, 1999). The late Miocene to Pleistocene high K calc-alkaline to K alkaline intrusions (e.g., intrusive complexes at Porgera, Grasberg, and Ok Tedi; McDowell et al., 1996) in the Central Ranges of New Guinea do not overlie a well-defined Benioff zone and lack coeval subaerial volcanic rocks. However, this paucity of volcanic rocks may in part reflect the extensive uplift and erosion of the region (e.g., average exhumation rates of ~0.7–1.7 mm/yr since the mid-Pliocene; Weiland and Cloos, 1996). The distribution of these intrusions coincides with the margins of uplifted basement blocks adjacent to north-northeast– to northeast-trending lineaments defined by faults, volcanoes, and drainage patterns (e.g., Grasberg, Ok Tedi, Porgera, Bosavi, Murray, and Bulolo lineaments; Fig. 15; Davies, 1991; Corbett, 1994; Fischer and Warburton, 1996; Hill et al., 2002; Pubellier and Ego, 2002). These lineaments parallel the structural trend of basement rocks, as inferred from aeromagnetic data (The Australian Petroleum Company Proprietary, 1961) and locally define boundaries to domains of differing structural styles in the Papuan fold belt (e.g., Ok Tedi; Mason, 1994, 1996). These relationships have led Hill et al. (2002) and others to infer the localization of intrusions at high crustal levels along dilatent segments of reactivated, orogen-parallel extensional Mesozoic basement faults near intersections with south-directed frontal thrusts. In contrast, there is no clear relationship between thrust faults and the Pliocene (3.2–2.8 Ma) calc-alkaline intrusions that occur south of the Sorong fault system in the Bird’s Head at Aisasjur, Papua (Paddy Waters, writ. commun., 2004). The southward migration of K-rich magmatism and related mineralization follows the southward progression of fold and thrust belt deformation (Davies, 1991), with intrusion-related mineral deposits forming in zones of major uplift at the intersection between frontal thrusts and orogen-transverse strikeslip (transfer) fault zones (Hill et al, 2002). The source of the K-rich magmas is ambiguous. Favored possibilities include delayed partial melting of the mantle modified by previous (?Cretaceous) subduction beneath the continental margin, prior to the accretion of allochthonous arc terranes in the mid-Miocene (Johnson et al., 1978) and asthenospheric upwelling due to the docking of arc terranes transported from the east (McDowell et al., 1996). The results of mantle tomographic imaging support the existence of ancient subduction slabs within the mantle beneath New Guinea (Hall and Spakman, 2002). Mineral deposit styles: This belt contains the Carstenz district, which includes the Grasberg porphyry Cu-Au deposit, the Ertsberg Cu-Au skarn complex, and a gold-rich skarn at Wabu. Grasberg contains a resource of 4,000 Mt at 0.64 g/t Au (2,560 t) and 0.6 percent Cu (24 Mt; Figs. 14–15, App. 4; van Leeuwen, 1994). The proven and probable reserve of the combined open-pit and underground deposits totals 1950 t of gold (year-end 1998; Widodo et al., 1999). The deposit is hosted by Pliocene diorite to monzonite stocks (3.3–2.7 Ma) and an andesite-diorite diatreme complex (MacDonald and 0361-0128/98/000/000-00 $6.00 Arnold, 1994). The main Grasberg intrusion cooled extremely rapidly, as indicated by nearly identical ages determined by Re-Os (2.9 ± 0.3 Ma on sulfide), Ar-Ar (3.33 ± 0.12–3.01 ± 0.06 Ma on biotite), and (U-Th)/He (3.1–2.9 ± 0.1 Ma on apatite), which supports the interpretation that the intrusive complex was emplaced within ~1 km of the paleosurface (Weiland and Cloos, 1996; McInnes et al., 2004). The Grasberg complex occurs about the intersection of northeasttrending, sinistral strike-slip fault systems with steeply northeast dipping reverse faults (MacDonald and Arnold, 1994) in the hanging wall to a major frontal thrust (Hill et al, 2002). The vertical ore distribution exceeds 1,500 m. The Pleistocene (1.2 Ma) Ok Tedi porphyry Cu-Au system (441 t Au, 4.5 Mt Cu; App. 5) is centered on monzonite porphyry stocks and breccia dikes, emplaced in Middle to Late Cretaceous siltstone and sandstone (Rush and Seegers, 1990). Lenses of copper-gold-magnetite and sulfide skarn locally occur within this rock sequence. The vertical distribution of ore exceeds 600 m, including an oxidized gold-rich cap that formed an annulus to the quartz stockwork core of the deposit in the leached cap, prior to mining (Rush and Seegers, 1990). Ok Tedi occurs in the core of a west-trending doubly plunging anticline in the hanging wall to a major frontal thrust that lies along a major northeast-trending basement fault inferred from the distribution of regional-scale folds and PlioPleistocene intrusions (Mason, 1996; Mason and Ord, 1999). Ok Tedi is the largest porphyry-skarn complex of several systems that formed in the Star Mountains contemporaneous to Plio-Pleistocene thrust faulting (Arnold and Griffin, 1978). The Ertsberg skarn complex, 2 km southeast of the Grasberg porphyry deposit, includes the Ertsberg, Ertsberg East, Intermediate, and Deep ore zones, DOM, and Big Gossan copper-gold skarn deposits. Combined past production and present reserves in the Ertsberg skarn deposits exceed 140 t of gold and 3.8 Mt of copper (Mertig et al., 1994; van Leeuwen, 1994). The majority of the gold and copper resources are hosted in the Erstberg East (Intermediate and Deep ore zones) orebody (189 t Au, 2.4 Mt Cu) in one of the largest Cu-bearing magnesian skarns in the world (Mertig et al., 1994; Coutts et al., 1999). The skarns are hosted within or adjacent to the Pliocene Ertsberg intrusion (3.1–2.6 Ma; Mertig et al., 1994; Meinert et al., 1997). The subsurface, Kucing Liar magnetite-copper-gold skarn, about 500 m southwest of the Grasberg intrusive complex, contains more than 450 t Au (Widodo et al., 1999). The protolith lithologies for the Ertsberg skarns consist of a basal dolomitic unit and an upper limestone sequence of early Tertiary age (New Guinea Group Limestone; Mertig et al., 1994). The Wabu Ridge gold skarn in the Hitalipa district, 35 km north of Grasberg-Erstberg, contains a geologic resource of more than 250 t Au and occurs along the margin of a late Miocene to early Pliocene K alkaline intrusive-extrusive complex (6.6–5.2 Ma; O’Connor et al., 1999). The deposit is hosted by an Oligocene sequence of limestone and calcareous siltstone in a south-vergent anticline-thrust fault complex, close to the intersection of a northeast-trending sinistral strike-slip fault (O’Connor et al., 1999). The Porgera mine in the New Guinea Highlands contains two major stages of gold mineralization, early intermediatesulfidation type within the open-pit (premine reserve: 54 Mt 10 11 5.8 g/t Au) and late high-grade ?low-sulfidation type in zone VII, which lies along the Roamane fault at a depth of 200 to 500 m beneath surface (premine reserve: 5.9 Mt at 27 g/t Au; Handley and Bradshaw, 1986; Handley and Henry, 1990; Richards and Kerrich, 1993; Sillitoe and Hedenquist, 2003). Both stages of mineralization are related to the 6.0 ± 0.3 Ma emplacement of the mafic (diorite-gabbro) sodic-alkalic Porgera Intrusive Complex within Jurassic carbonaceous siltstones and Cretaceous calcareous shales (Handley and Henry, 1990; Richards, 1990; Richards and McDougall, 1990). The early stage consists of disseminated pyrite and quartz-carbonate-base metal sulfide veins and associated sericite-carbonate alteration; the later stage consists of quartz-roscoelite (Vbearing sericite)-adularia veins and breccias with native gold and minor pyrite and Au-Ag telluride minerals (Handley and Bradshaw, 1986; Ronacher et al., 1999). The presence of magnetite-chalcopyrite-pyrrhotite and biotite-actinolite-anhydrite in the early-stage assemblage at more than 1,000 m below zone VII (Ronacher et al., 1999) provides a potential link to porphyry-style mineralization at depth. The duration of the hydrothermal system, including both early and late stages of mineralization, is ~100,000 yrs, as constrained by the 40 Ar/39Ar laser dating method (Ronacher et al., 2002). Intermediate-sulfidation gold systems occur at Hidden Valley, Kerimenge, Hamata, and Wau in the Wau-Bulolo graben (Carswell, 1990; Hutton et al., 1990; Nelson et al., 1990; Denwer and Mowat, 1998). This graben is an intra-arc rift basin formed in the Pliocene as a result of movement along inferred northeast-trending strike-slip faults in a basement of Cretaceous to Paleogene schist and phyllite (Owen Stanley Metamorphics) that was intruded by the mid-Miocene Morobe Granodiorite (Lowenstein, 1982; Dekker et al., 1990; Corbett, 1994). The deposits are typically associated with faults and late-stage breccia bodies and diatremes related to mid-Pliocene dacite to andesite porphyry intrusions (e.g., Edie Porphyry; Carswell, 1990). The common ore type consists of quartz-carbonate-base metal sulfide veins and related sericite-quartz-pyrite alteration. These systems contain more than 190 t Au at grades that range from 1.0 to 3.7 g/t Au. The ore mineralogy and paragenetic sequence of events at the Pliocene Umuna lode, Misima Island (77 t Au) is similar to those described for the deposits of the Bulolo graben (Lewis and Wilson, 1990; Appleby et al., 1996). At Umuna, pyritic quartz and quartz-carbonate veins fill a steeply dipping fault zone in greenschist facies metamorphic rocks (Lewis and Wilson, 1990). The Plio-Pleistocene Gameta and Wapola intermediate-sulfidation gold deposits (4.2 t Au) on Fergusson Island share characteristics with the style of mineralization at Misima (Appleby et al., 1996). Gameta and Wapola are localized along gently to moderately dipping detachment faults related to metamorphic core complexes that place Cretaceous or older ultramafic rocks of the Solomon Sea plate on pre-Cretaceous gneiss and amphibolite of the Australian craton (McNeil, 1990; Chapple and Ibil, 1998). Pliocene granodioritic plutons form the core to the domal uplifts. The core complexes are inferred to have formed from late Pliocene to Recent time in response to isostatic uplift of subducted sialic continental crust through overlying, obducted oceanic crust and rifting due to the westerly propagation of the Woodlark basin spreading center (Chapple and Ibil, 1998). 0361-0128/98/000/000-00 $6.00 The Pliocene Tolukuma intermediate-sulfidation quartzadularia-carbonate vein system, 100 km north of Port Moresby, is high grade (1.5 Mt at 13.8 g/t Au). The deposit is associated with phreatomagmatic breccias in the hanging wall of a normal fault that juxtaposes andesitic volcanic rocks against footwall Owen Stanley Metamorphics (Semple et al., 1998). Maramuni Geologic setting: The Maramuni arc forms a belt of Miocene calc-alkaline, intermediate to mafic volcanic and intrusive rocks that extends ~1,000 km across the southwestern margin of the New Guinea mobile belt from near the Irian Jaya border to 100 km southeast of Port Moresby (Fig. 15; Table 1; Page, 1976; Dow, 1977; Rogerson and McKee, 1990; McDowell et al., 1996; Hill and Raza, 1999). Arc magmatism is inferred to be related to the subduction of the Solomon Sea beneath the Papuan Peninsula and eastern New Guinea, following the early to mid-Miocene collision of the Ontong Java plateau with the Melanesian arc and the southwestward jump in subduction zones, from the Melanesian to the Marumuni trench (Cullen and Pigott, 1989; Hill and Raza, 1999; Hall, 2002). The basement to the arc includes pre-Triassic metavolcanic rocks and granite in the Papuan fold belt (Papuan province) and variably metamorphosed, latest Cretaceous to Paleogene mélange and ophiolite in the New Guinea and Owen Stanley thrust belts (Solomon province; Hamilton, 1979; Pigram and Davies, 1987; Rogerson and McKee, 1990). The arc has been exhumed at least 3 to 4 km mainly from 8 to 5 Ma, due to the late Miocene collision of the FinisterreAdelbert (Melanesian) arc, which caused regional uplift of northern Papua New Guinea (Crowhurst et al., 1996). This exhumation exposed mid-Miocene batholiths east of the Bosavi lineament, including the Bismark (17–13 Ma), Maramuni Diorite (15–10 Ma), Akuna (17–15 Ma) and Morobe Granodiorite (14–12 Ma) intrusive complexes (Page and McDougall, 1972; Page, 1976; Lowenstein, 1982; Hall et al., 1990). The margins of these batholiths serve as the locus for the emplacement of late Miocene porphyries and related copper-gold mineralization (e.g., Yandera porphyry; Watmuff, 1978). Mineral deposit styles: Middle to late Miocene Cu-Au porphyry and skarn mineralization styles are associated with diorite to granodiorite porphyritic intrusions in the Marumuni arc (Fig. 15). The subeconomic Frieda River porphyry system developed between 13.6 and 11.5 Ma and has a mean K/Ar age of 11.9 Ma (Whalen et al., 1982). The major orebodies, Horse-Ivaal and Koki, are centered on small, elongate calc-alkaline microdiorite stocks (<1.5 km in length), cut by latestage andesite porphyry and postmineralization trachyandesite dikes (Hall et al, 1990). The estimated depth of emplacement of the porphyry complex is 1.5 to 2 km beneath paleosurface (Hall et al., 1990). The Nena high-sulfidation Cu-Au deposit, 7 km northwest of Frieda, formed contemporaneously with the Frieda porphyry deposits (Hall et al., 1990). The deposit is hosted by a middle Miocene sequence of andesitic lapilli tuff, directly beneath an andesitic lava unit (Bainbridge et al., 1998). Hypogene covellite, stibnoluzonite, and luzonite-enargite are the primary ore minerals hosted by residual quartz alteration. The deposit formed at a similar 11 12 structural-stratigraphic level to the porphyry deposits with ore distributed over a vertical extent of ~300 m (Bainbridge et al., 1998). The Frieda and Nena deposits lie along the northeast-trending zone of faults and intrusions that extend southwest through Ok Tedi, which Bainbridge et al. (1998) suggested represents a basement fault that has localized the southwestward migration of magmatism from mid-Miocene at Frieda to Pleistocene at Ok Tedi. The middle Miocene Wafi porphyry and coeval high-sulfidation system contains in excess of 107 t Au and 1.3 Mt Cu (Tau-Loi and Andrew, 1998). The Wafi deposits are hosted by siliciclastic rocks of the Owen Stanley Metamorphics, intruded by diorite to dacite porphyry stocks, adjacent to two major northeast-trending faults (Ercig et al., 1991; Tau-Loi and Andrew, 1998). The porphyry system is centered on a diorite stock, less than 300 m in diameter, concealed beneath a leached cap of residual quartz and is extensively overprinted by advanced argillic alteration that extends to ~450 m beneath surface; the relict potassic zone is preserved at ~600-m depth. The depth of porphyry-style mineralization exceeds 900 m. Several enargite-bearing residual quartz-hosted gold zones occur near fault intersections with the margin of the 1.0 by 0.6 km Wafi diatreme (Ercig et al., 1991; Tau-Loi and Andrew, 1998). Secondary K-feldspar in the potassic zone of the porphyry deposit indicates a K/Ar date of 14 Ma, whereas, alunite from the advanced argillic zone returns a K/Ar date of 13 Ma (Tau-Loi and Andrew, 1998). A subeconomic porphyry Cu-Au system is associated with mid- to late Miocene dacitic to dioritic stocks at Yandera (9–7 Ma; Watmuff, 1978) and a small gold skarn occurs adjacent to the Elandora andesite to granodiorite porphyry (late Miocene?) at Mount Victor in Kainantu (Abiari et al., 1990). At Mount Victor, the causal Elandora porphyries are localized along the margins of the mid-Miocene Akuna batholith and Cretaceous Mount Victor Granodiorite (Abiari et al., 1990). The origin of the shoshonitic K alkaline Tabar-Feni Island chain, which lies approximately 400 km above the New Britain subduction slab, is less evident. However, Pliocene to Recent magmatism in this arc could originate from subduction modified mantle and be related to north-trending rifting of the outer Melanesian arc during the opening of the Bismarck Sea, which commenced at ~3.5 Ma (Johnson, 1979; Wallace et al., 1983; McInnes and Cameron, 1994). A subarc mantle source to Lihir Island magmatism is supported by the similarity between 187Os/188Os values from samples of gold ore and related intrusions from the Ladolam deposit and the present-day mantle (187Os/188Os value of 0.1217), as sampled from xenoliths collected from a nearby sea-floor volcano (McInnes et al., 1999). The geologic basement to the Melanesian arc is not exposed but is inferred to be pre-Eocene oceanic crust (Hall, 2002) The oldest rocks exposed include Eocene calc-alkaline pillow lavas, volcaniclastic rocks, minor limestone, and rare gabbroic intrusions (Dow, 1977; Rogerson and McKee, 1990). The northwest-trending faults that extend across eastern New Britain, New Hanover, and southern New Ireland Islands are inferred to link to offshore transform faults that separate northeast-oriented spreading ridges in the Bismarck Sea (Falvey and Pritchard, 1982; Rogerson and McKee, 1990). North-trending horst blocks form the foundation for the Islands of the Tabar-Feni chain and localize Pliocene to recent volcanism on Lihir Island (Moyle et al., 1990). On Bougainville Island, northwest-trending faults and lineaments localize the distribution of Pleistocene to Recent volcanoes, where more than 1,200 m of uplift has occurred since the early Miocene (Clark, 1990). Mineral deposit styles: The Melanesian arc hosts early Miocene (25–22 Ma) Cu-Au porphyry (±skarn) prospects, such as Esis, Plesyumi, and Kulu (Hine and Mason, 1978; Hine et al., 1978; Titley, 1978) and the Wild Dog high-sulfidation deposit (Lindley, 1990) on New Britain, and the Legusulum porphyry prospect on New Ireland (Fig. 15; Rogerson and McKee, 1990; Singer et al., 2002). The Arie and Mount Kren porphyry systems on Manus Island are middle Miocene (15–13 Ma; Singer et al., 2002). The Arie deposit is the largest of all the Miocene systems (165 Mt at 0.32% Cu) and is related to diorite porphyry and breccia bodies hosted by basaltic to andesitic volcanic and volcaniclastic rocks (Singer et al., 2002). The Pliocene (3.4 Ma) Panguna copper-gold porphyry deposit (768 t Au, 6.4 Mt Cu) on Bougainville Island is centered on a series of diorite, quartz diorite, and granodiorite stocks localized along the margin of a premineralization (~5–4 Ma) quartz diorite pluton (Clark, 1990). The following description is based on that of Clark (1990). Intrusive breccia pipes in the surrounding andesitic volcanic sequence and along intrusive contacts host high-grade ore (>1.0 g/t Au and 1.0% Cu). Mapped faults and regional lineaments defined from sidelooking airborne radar indicate two populations: west-northwest trends, which correspond to the elongate dimensions of synmineralization diorite stock and related dikes, and northeast trends, which parallel late-stage pebble dikes and postmineralization (1.6 Ma) andesite dikes. The deposit extends from surface to a depth of ~650 m. The Pleistocene (~0.3 Ma) Ladolam gold deposit (1,378 t Au) on Lihir Island lies in the floor of the K alkaline Quaternary Melanesian (inner and outer) Geologic setting: The calc-alkaline Melanesian arc, as described in this paper, from west to southeast, includes the accreted portions of the Finisterre-Adelbert arcs in northeastern New Guinea and New Britain Island (inner Melanesian arc) and the Manus, New Ireland, and Bougainville Islands (outer Melanesian arc; Fig. 15; Table 1), which corresponds to the Finisterre province of Rogerson and McKee (1990). The Melanesian arc represents the northerly continuation of the Solomon arc, which began development in the Eocene to early Oligocene in response to southwest-directed subduction of the Pacific plate (Falvey and Pritchard, 1982; Hall, 2002). The collision of the Ontong Java plateau in the early Miocene jammed the Melanesian trench with a general hiatus in arc magmatism from the mid- to late Miocene until northeast-directed subduction was established beneath the New Britain trench in the earliest Pliocene (~6 Ma; Hall, 2002). Magmatism continues through to the present. The configuration of the arc system is largely due to the modification of the mid-Oligocene arc by westerly transport of the inner Melanesian arc toward New Guinea, which led to accretion of the Finisterre-Adelbert terranes in the late Miocene (Pigram and Davies, 1987; Crowhurst et al., 1996; Hall, 2002). 0361-0128/98/000/000-00 $6.00 12 13 Luise caldera, in the hanging wall of a north-northeast–trending normal fault (Moyle et al., 1990; Carman, 1995, 2003). Three major styles of hydrothermal alteration are evident. Early porphyry-style potassic (biotite-orthoclase-albite-anhydrite) and propylitic (calcite-chlorite-K-feldspar-albite-Kmica) alteration types are overprinted by transitional epithermal adularia and late epithermal silicic, argillic, and advanced argillic alteration styles (Carman, 2003). The superposition of these types of alteration and a range of K/Ar dates obtained from hydrothermal minerals (1.0–0.2 Ma for biotite, Kfeldspar, and illite, and 0.15 Ma for alunite) led Moyle et al. (1990) and Carman (1995) to call upon catastrophic sector collapse of the Luise stratovolcano (present rim elevation of ~700 m) and the telescoping of the hydrothermal system from porphyry to epithermal conditions at ~0.3 Ma. The gold in the deposit is mostly contained in epithermal, pyrite-marcasite-arsenopyrite breccia and quartz-calcite vein ore types that typically extend from near sea level to 200 m below (Moyle et al., 1990; Carman, 2003). Sillitoe and Hedenquist (2003) interpret the epithermal event at Ladolam to be low sulfidation, on the basis of the extensional back-arc setting and alkaline host rocks. about 4 to 3 Ma as a result of collision between the arc and the Australian margin in Timor (Carter et al., 1976). Clastic and carbonate sedimentary rocks are intercalated with the volcanic sequences of both generations of arc. The Neogene arc is characterized by calc-alkaline andesitic to dacitic volcanic rocks and their intrusive equivalents in Sumatra, and basaltic to andesitic volcanic rocks and intrusions of calc-alkaline and tholeiitic affinities in the Java–Flores and east Banda sectors (Hamilton, 1979; Hutchison, 1989; Soerja-Atmadja et al., 1994). Dacitic to rhyolitic suites occur locally and are particularly abundant in the Alor, Wetar, and Romang sectors. Quaternary basaltic to dacitic, and locally rhyolitic, volcanic products cover older volcanic rocks throughout much of the arc. Mineral deposit styles: The arc is characterized by intermediate-sulfidation vein systems at Mangani, Salida, Lebong Tandai/Donok, and Lampung in Sumatra and also in West Java (Fig. 14, App. 4). The geologic basement to Sumatra and western Java consists of Sundaland continental crust, where no direct link between the intermediate-sulfidation deposits and coeval intrusions is apparent. Nearly 80 t Au was produced from high-grade lodes (~15 g/t Au) in Lebong Tandai and Lebong Donok in the Bengkulu district by the Dutch prior to 1941 (Kavalieris, 1988; van Leeuwen, 1994). Lebong Tandai is hosted by Miocene andesitic volcanic rocks and Lebong Donok occurs in Miocene carbonaceous shale associated with the brecciated margins of a competent dacite intrusion (Kavalieris, 1988). The Tandai lode is localized along a steeply dipping east-west fault system, which is offset by northeast- and northwest-oriented strike-slip faults (Jobson et al., 1994). Tandai, Donok, and Rawas, to the east, occur within 20 to 30 km of the Sumatra fault near major east- and northeast-trending arc-transverse faults. At Miwah in Aceh, northern Sumatra, a high-sulfidation system is hosted by north-trending, tensional fracture zones in andesitic to dacitic volcanic rocks, intruded by a Pliocene rhyodacite within 25 km of the Sumatra fault (Williamson and Fleming, 1995). The Tangse porphyry Cu-(Mo) prospect occurs 40 km to the northwest of Miwah and is hosted by a middle to late Miocene plutonic complex (van Leeuwen et al., 1987). At Martabe, east of Sibolga and south of Lake Toba, recently discovered disseminated high-sulfidation deposits are hosted by multistage phreatomagmatic breccias and dacitic flow dome complexes localized by extensional faults adjacent to a strand of the Sumatra fault (Levet et al., 2003; Sutopo et al., 2003). Early, texture-destructive, residual quartz alteration zones are tabular and partly controlled by the moderate dips of local breccia units and underlying porphyritic andesite adjacent to steeply dipping dilational faults. This style of advanced argillic alteration serves as preparation for subsequent gold depositional events. Gold is associated with late-stage fracture- and breccia-controlled enargite-luzonite mineralization and, to a lesser extent, earlier, intermediate-sulfidation chalcedony veins (Levet et al., 2003). More than five deposits occur over a 7-km strike length, the largest of which, Purnama, has a resource of 116 t Au. Gunung Pongkor (103 t Au at 17.1 g/t Au) in western Java is a low sulfide intermediate-sulfidation bonanza vein system hosted by Miocene andesitic tuffs and breccias and a subvolcanic andesite intrusion (Basuki et al., 1994). The Pongkor Sunda-Banda Geologic setting: This Eocene to Recent arc extends nearly 4,000 km from northwestern Sumatra through Java and terminates in the Banda Island group of eastern Indonesia (Fig. 14; Table 1). The basement to the arc varies from Mesozoic to late Paleozoic platform sedimentary rocks deposited on continental crust that are intruded by two mica granites in Sumatra, through Cretaceous to Tertiary melange and ophiolite in central and eastern Java, to oceanic crust in the Banda arc (Hamilton, 1979). An Eocene to early Miocene calc-alkaline arc, the “Old Andesites” of van Bemmelen (1949), extends through Sumatra and Java and continues eastward toward the Banda arc. The dextral Sumatra fault follows the arc and is inferred by Hamilton (1979) to have been active since the late Oligocene; more recent work indicates the fault became active during the Miocene (McCarthy and Elders, 1997). Although the term “Old Andesites” has given the impression that the arc is andesitic, and such rocks are the most obvious arc products, dacitic rocks are widespread, as minor intrusions, lavas, and pyroclastic and ash deposits. The dacitic rocks have been overlooked because they have commonly been reworked into sedimentary sequences (Smyth et al., 2003) but show that arc activity began in the Eocene in Java. Arc activity ceased, or significantly declined, in the early Miocene and there was widespread deposition of sedimentary rocks, especially carbonates, between Java and Sumba. Arc activity resumed in the late middle Miocene, and a middle Miocene to Recent magmatic arc is built on older sedimentary and volcanic rocks in most of the Sunda-Banda arc, and in Java lies to the north of the axis of the older arc. The volcanic arc has propagated east into the Banda region since about 12 Ma; the volcanic rocks east of Sumbawa are less than 9 Ma old and the volcanoes become progressively younger eastward (Abbott and Chamalaun, 1981; Honthaas et al., 1998). Volcanism continues to the present day, although Banda arc volcanic activity ceased in the Wetar region at 0361-0128/98/000/000-00 $6.00 13 14 vein system consists of four main northwesterly trending veins that define a northeast-oriented corridor. This corridor extends through the Bayah dome to the southwest, where it controls the distribution of several vein systems in the historic Cikotok mining district. The host rocks in the Bayah dome consist of Pliocene volcanic and clastic sequences, which locally are intruded by premineralization porphyritic dacite stocks. Individual lodes are hosted by steeply dipping north-northeast- and north-northwest–trending faults. The northerly orientation and dilational character of these lodes are consistent with their development as a response to north-directed subduction in this sector of the arc. The age of intermediate-sulfidation vein mineralization obtained from adularia is 8.5 Ma, which differs from the 2.1 to 1.5 Ma ages determined for other epithermal lode systems in the region (Marcoux and Milesi, 1994). The style of mineralization changes to the east. In the Lombok–Sumbawa portion of the arc, which is underlain by oceanic crust, high-sulfidation epithermal and porphyry CuAu deposits and prospects are present. The Batu Hijau porphyry copper-gold deposit in southwest Sumbawa contains more than 366 t Au and 4.8 Mt Cu (Clode et al., 1999) and occurs in an uplifted crustal block, which has been exhumed about 2 km since the mid-Pliocene (Garwin, 2002a). Mineralization is genetically related to three stages of Neogene tonalite porphyry intrusions emplaced in quartz diorite and andesitic volcaniclastic wall rocks. The tonalite porphyry complex was emplaced over a span of ~100,000 yrs at ~3.7 Ma (Fletcher et al., 2000; Garwin, 2002a; McInnes et al., 2004). A late mineralization diatreme occurs about 2 km northwest of Batu Hijau. The deposit occurs in the central portion of a district characterized by several porphyry centers, peripheral intermediate-sulfidation vein systems, and distal, sedimentary rock-hosted replacement-style mineralization (Meldrum et al., 1994; Irianto and Clark, 1995; Garwin, 2002a). Local controls include the intersections of northeast- and northwesttrending fault zones with the margins of premineralization quartz diorite plutons. Enargite-gold veins at Elang, 60 km east of Batu Hijau, occur close to a porphyry copper-gold system, which formed at ~2.7 Ma (Maula and Levet, 1996; Garwin, 2000). Batu Hijau and Elang occur within 20 to 30 km of a major left-lateral oblique-slip fault zone that controls the distribution of Miocene volcano-sedimentary units, Pliocene intrusions, and the present coastline of Sumbawa. Base metal-rich, intermediate-sulfidation epithermal barite and quartz vein prospects are hosted in andesitic to dacitic volcanic rocks and intercalated sedimentary rocks in the West Flores, East Lomblen-Pantar, Wetar, and Romang regions of the Banda arc. In Romang, vein-style mineralization is localized in a dilational zone along a west-northwest–trending dextral strike-slip fault corridor (Garwin and Herryansjah, 1992). Local jasperoid replacing reefal limestone characterizes several prospects in the Flores-Romang sector of the arc (e.g., localities in Rinca Island, West Flores, and south Romang). At Wetar, Au-Ag barite deposits (23 t Au) represent a submarine exhalative system in a sea-floor caldera setting similar to the Kuroko deposits in Japan (Sewell and Wheatley, 1994). Gold-silver mineralization occurs in stratiform barite sand units (exhalite), which are underlain by copper-rich massive pyrite-marcasite zones and quartz-pyrite stockworks 0361-0128/98/000/000-00 $6.00 hosted in argillically altered felsic volcanic breccias of Miocene age. Most of the copper is contained in enargite, which is atypical of volcanic-associated massive sulfide systems. The age of mineralization is believed to lie between 5 and 4 Ma (van Leeuwen, 1994; Sewell and Wheatley, 1994). The Wetar deposits were formed in north elongate extensional basins developed by the interaction of steeply dipping, north-northwest and north-northeast trending conjugate strike-slip faults inferred from the description of the geologic setting of the deposits in Sewell and Wheatley (1994). Central Kalimantan Geologic setting: The Paleogene to Miocene Central Kalimantan arc of Carlile and Mitchell (1994) extends approximately 1,200 km from western Sarawak, through northwest and central Kalimantan into northeastern Kalimantan (Fig. 14; Table 1). The trace of the arc disappears to the northeast, beneath the western onshore extension of the Neogene SuluZamboanga arc in the Semporna peninsula of Sabah. The basement to the arc is continental in western Kalimantan, where the oldest rocks exposed consist of late Paleozoic mica schists intruded by Triassic to Carboniferous and Cretaceous (Schwaner Massif) granites (Hamilton, 1979; Hutchison, 1989). In contrast, Late Cretaceous to Paleogene ophiolite, arc volcanic and sedimentary rocks comprise the basement to the arc in eastern Kalimantan and Sabah. In the Bau area of west Sarawak, Triassic andesitic arc volcanic rocks are overlain by Jurassic and Cretaceous marine carbonate and siliciclastic rock sequences interpreted by Hutchison (1989) to have been deposited along the marginal shelf of Sundaland. The arc is defined by the discontinuous distribution of erosional remnants of calc-alkaline andesitic, trachyandesitic, and local dacitic volcanic-plutonic centers, inferred to be associated with tonalite, granodiorite, and granite intrusions in western (Sintang intrusive suite) and northeastern (Long Lai intrusive suite) Kalimantan (Carlile and Mitchell, 1994). Arc activity is still poorly dated and may extend from the Eocene. Arc construction is related to south-directed subduction beneath the Rajang accretionary complex of northwest Borneo in the Oligocene to Miocene by Carlile and Mitchell (1994). Arc activity diminished after early Miocene collision between the continental crust of the South China Sea margin and the active margin of northern Borneo (Hutchison et al., 2000; Hall and Wilson, 2000). About ~1.3 km of exhumation from 25 to 23 Ma and the eastward shift of the Kutai basin sedimentation mark this tectono-magmatic event (Moss et al., 1998). The distribution of igneous rocks and middle to late Tertiary sedimentary basins indicates that northwest-trending arc-transverse faults played a role in arc tectonics and magmatism (Fig. 8). The sedimentary rocks of the Tertiary Kutei basin are locally intercalated with arc-related pyroclastic rocks in eastern Kalimantan. Hamilton (1979) inferred that the development of the Kutai basin is related to the rifting of the eastern margin of Sundaland and the drifting of western Sulawesi away from Kalimantan in the middle Tertiary. Chambers and Daley (1997) indicated initial rift-basin formation in the Eocene and subsequent basin development by load subsidence to Recent time. It is now clear that the separation of western Sulawesi and Kalimantan by rifting began in the Eocene, although it is still uncertain if there was ocean crust formation in the 14 15 Makassar Strait (Cloke et al., 1999). Plio-Pleistocene tholeiitic plateau flood-basalts form platforms in northwestern, north-central, and northeastern Kalimantan. Mineral deposit styles: A well-defined northeasterly trending belt of gold deposits and prospects extends approximately 500 km along the southeastern margin of the Oligocene to Miocene arc (Fig. 14). This central Kalimantan gold belt coincides with the margins of the Kutei and Barito basins along the eastern flanks of the Schwanner massif and the rifted margin of Sundaland. Andesitic volcanic rock-hosted, intermediate-sulfidation vein and stockwork mineral deposits occur along this belt. The styles of mineralization in these systems are discussed by Simmons and Browne (1990) for Mt. Muro, by Wake (1991) for Muyup, by Thompson et al. (1994) for Masupa Ria, and van Leeuwen (1994) for Mirah and the others. The Mt. Muro vein complex is the largest of these deposits (51 t Au). The complex lies close to the northwesttrending Trans Borneo shear of Hutchison (1989) and consists of more than 15 vein systems, most of which strike northwesterly and dip steeply. At Masupa Ria, intermediatesulfidation veins are superimposed on an early-stage high-sulfidation alteration system (Thompson et al., 1994). The Kelian intermediate-sulfidation deposit (179 t Au, van Leeuwen et al., 1990) is localized in a maar-diatreme complex, which contains multiple diatreme breccia pipes and latestage endogenous quartz-porphyry domes (Davies et al., 1999). The diatreme complex postdates subvolcanic andesite intrusions and a north-northeast–trending Eocene to Oligocene rhyolitic volcano-sedimentary sequence. The ore is hosted by a variety of breccia styles, which have undergone extensive hydrothermal alteration. Styles of mineralization include network veins and breccia and fracture filling by complex carbonate-quartz-pyrite-sphalerite-galena-gold/electrum. Limited K/Ar radiometric dating at Kelian indicates an early Miocene age for andesite intrusion (23 Ma) and sericite alteration (20 Ma; van Leeuwen et al., 1990). The deposit lies adjacent to the Kutei basin and along the rifted margin of Sundaland. Disseminated sedimentary rock-hosted gold deposits occur in the Bau district of western Sarawak (~40 t Au in past production, Wilford, 1955; Wolfenden, 1965). Gold is associated with carbonate and siliciclastic members of the Jurassic Bau Limestone in fault contact with the overlying Cretaceous Pedawan Shale. Pervasive silicification and extensive collapse breccias have developed close to the shale and/or limestone contact along the Tai Parit fault and adjacent to argillic-altered dacite porphyry dikes. Tai Parit marks the general intersection between a north-northeast–oriented belt of middle Miocene (13–10 Ma; Metal Mining Agency of Japan, 1985) dacite to granodiorite intrusions with the northeast-trending Bau anticline. Disseminated gold mineralization is associated with arsenopyrite in silicified shale at Jugan, approximately 10 km along trend, to the northeast. These sedimentary rockhosted deposits form part of a >300 km2 district, which also includes weak porphyry copper-style mineralization and previously mined Cu-Au skarns, auriferous mesothermal and epithermal polymetallic sulfide-veins, and disseminated mercury deposits (Schuh, 1993) Historic and recent alluvial gold mines are common in western and central Kalimantan. The placer gold is probably sourced from orogenic quartz lodes in crystalline basement 0361-0128/98/000/000-00 $6.00 and intermediate-sulfidation vein systems that have undergone supergene enrichment during weathering. A colloidal origin for the gold recovered from the Ampalit alluvial mine in Central Kalimantan has been inferred by Seeley and Senden (1994), on the basis of gold grain morphology and its fineness of 998. The delicate nature of the grain boundaries and the high fineness preclude mechanical transport from nearby epithermal veins, which commonly contain electrum (purity of <900 fine). Other Indonesian, Borneo, and Papua New Guinean arcs Several other late Cenozoic magmatic arcs are described by Carlile and Mitchell (1994), including the Miocene Northwest Borneo (Sarawak), the Neogene West Sulawesi, and Miocene Moon-Utawa arcs (Fig. 14). Although there is igneous activity in these regions, there are reasons to doubt that these arcs formed in subduction-related settings. The Miocene igneous rocks of Sarawak are too poorly known and dated to be confident of their origins. Recent work (Prouteau et al., 2001) suggests there are two suites: early Miocene arc volcanic rocks are the product of south-directed subduction north of Borneo and could be the equivalent of Paleogene rocks in Sabah (Hall and Wilson, 2000; Hutchison et al., 2001), whereas middle and late Miocene magmatic rocks are postcollisional and have some adakitic features (Prouteau et al., 2001). Neogene volcanic activity in western Sulawesi began at about 11 Ma and was probably not related to active subduction but rather to extension (Yuwono et al., 1988; Priadi et al., 1994; Polvé et al., 1997). Elburg and Foden (1998) described the rocks as syncollisional and isotopically enriched and relatively K rich, which they attribute to a contribution of subducted sediments. Neogene magmatic rocks are commonly high K and include shoshonites and leucitites. The trace element patterns in the lavas suggest subduction zone recycling, but they are most similar to rocks of postsubduction extensional environments, such as those of the southwetern United States (Macpherson and Hall, 2002). There was little volcanism in western New Guinea during the Neogene and no evidence of significant subduction. Seismically, there is a poorly defined slab beneath western New Guinea, which suggests a south-dipping subducted slab of little more than 100 km at the New Guinea trench. Tomographic images show no slab beneath western New Guinea (Spakman and Bijwaard, 1998; Hall and Spakman, 2002). As noted by Carlile and Mitchell (1994), Neogene volcanic rocks from Irian Jaya have been little explored and the midMiocene Moon-Utawa rocks have not been well studied. Other Miocene volcanic rocks in Irian Jaya have an unusual chemical character that is postcollisional and quite different from Neogene magmatic rocks in eastern New Guinea (Housh and McMahon 2000). Carlile and Mitchell (1994) postulated the existence of the Neogene Aceh arc in northernmost Sumatra, on the basis of the distribution of volcanic rocks of similar age and the citation of an offshore trench in Stephenson et al. (1982). However, this arc, if it exists at all, lacks a Benioff zone and a pronounced bathymetric trench, as indicated by satellite gravity data. It is more likely that the Aceh arc represents a young portion of the Sunda arc with magmatic activity localized along a west-northwest–trending arc-transverse fault zone. 15 16 Miocene to Pliocene calc-alkaline and alkaline volcanic rocks and granodiorite to monzonite intrusions (Dondo Suite) in the western arm and neck of Sulawesi do not host significant gold mineralization. However, significant gold deposits do occur at Awak Mas (26 t Au) and Palu (G. Hartshorn, pers. commun., 1999). Both deposits are located close to sinistral strike-slip faults of the Palu fault system. In Awak Mas, epi- to mesothermal quartz veins and stockworks are localized along shear zones in Cretaceous metasedimentary basement and near fault contacts with basalt (van Leeuwen, 1994). Gold occurs in pyritic quartz-albite-carbonate breccias, veins, and stockworks. The Ag/Au ratio of the deposit is less than one. The genetic relationship between mineralization and the Neogene magmatic arc, if any, is not clear. No significant gold prospects are known in the Northwest Borneo arc of Hutchison (1989). However, gold occurs in placers and minor quartz veins near dacitic pyroclastic rocks and flows of the Hose Mountains and the Usun Apau plateau (Kirk, 1968; Geological Survey of Malaysia, 1976). The Miocene andesitic volcanic rocks and dioritic intrusions in the “Bird’s Head” portion of the Moon arc in Irian Jaya are characterized by gold and base metal mineralization associated with quartz veins and stockworks (Carlile and Mitchell, 1994). No significant gold or copper prospects are documented for the Oligocene to Miocene volcanic arc rocks on Yapen Island, east of the Moon arc. The Mount Kinabalu pluton, satellite intrusions, and coeval andesitic-dacitic volcanic rocks in northwestern Sabah do not lie along a well-defined magmatic arc. The ages of the causal high K calc-alkaline adamellite pluton and apophyses range from 12.2 to 1.3 Ma (Kirk, 1968; Hutchison, 1989). However, the most probable age ranges from 7.0 to 6.4 Ma (App. 4; Bellon and Rangin, 1991; Imai, 2000). The pluton intrudes Paleogene sedimentary rocks of the Rajang accretionary prism to the inactive Northwest Borneo trench (Hutchison, 1989). A series of northwest-trending faults pass through Mount Kinabalu, forming a fault zone that extends through central Sabah to the Semporna peninsula (Kinabalu fault of Tokuyama and Yoshida, 1974). Basement rocks consist of greenschist- and amhibolite-facies schist and gneiss of Mesozoic (?) age. The Mamut Cu-Au deposit is centered on an apophysis to the Kinabalu pluton along the eastern flank of Mount Kinabalu. Porphyry-style mineralization occurs in and adjacent to an adamellite porphyry stock (7.0 Ma; Imai, 2000) cut by postmineralization granodiorite dikes in a sequence of weakly hornfelzed sandstone, mudstone, spillitc tuffs, and serpentinized peridotite. The host-rock sequence is inferred to have been tectonically emplaced in the early to middle Miocene (Kosaka and Wakita, 1978). Woodlark Island in Papua New Guinea is a remnant of a Miocene island arc built upon Cretaceous (?)-Eocene tholeiitic, Solomon Sea floor basalt, which is inferred to have been obducted onto the Australian craton (Fig. 15; Russell and Finlayson, 1987; Russell, 1990). Intermediate-sulfidation gold deposits, Kulumadau, Boniavat, and Busai, are related to a porphyritic microdioritic pluton and monzonite dikes emplaced in high K calc-alkaline andesitic volcanic and volcaniclastic rocks of early to middle Miocene age (Russell, 1990). The ore assemblage at Kulumadau contains calcite ± quartz-pyrite-base metal sulfides in phreatic explosion breccias, in contrast to the 0361-0128/98/000/000-00 $6.00 ore assemblages at the Busi and Boniavat vein systems, which are more quartz rich and typically contain only minor base metal sulfides (Russell, 1990). The age of mineralization at Busai is dated as 12.3 Ma (Russell and Finlayson, 1987). Burman Geologic setting: The Neogene to Quaternary Burman magmatic arc includes an onshore portion in Myanmar, which extends ~1,200 km from the Jade mines in the north through Mount Popa and Pegu Yoma in the south, and an offshore chain of islands and seamounts in the Narcandam and Barren Island region of the Andaman Sea (Fig. 2; Table 1). The arc lies to the west of the dextral strike-slip Sagaing fault, which marks the boundary between the Burma continental block to the west and the Shan-Thai core of the Eurasian plate to the east (Hutchison, 1989). The onshore portion of the arc is calcalkaline to high K calc-alkaline, while the offshore sector is tholeiitic (Hutchison, 1989). A belt of alkaline to shoshonitic rocks, about 100 km to the east of the calc-alkaline arc, extends along the eastern side of the Sagaing fault and continues southward along the eastern shore of the Andaman Sea. The eastward increase in alkalinity is attributed to the waning stages of eastward subduction of the Indian plate beneath the Burma block during the transition to strike-slip movement associated with spreading in the Andaman Sea that began by ~10 Ma (Curray et al., 1979; Stephenson and Marshall, 1984). The Burman magmatic arc is associated with a poorly defined Benioff zone that extends to a depth of 200 km. The basement to the arc in the Banmauk region consists of Mesozoic phyllite, schist, gneiss, and amphibolite. Marine basalt, andesite, volcaniclastic rocks, and mudstone overlie the basement rocks and both sequences are intruded by the Cretaceous Kanzachaung granodiorite batholith (United Nations Development Program, 1978a). Eocene andesite sills and early Oligocene diorite to granodiorite stocks (e.g., Shangalon granodiorite), trachyte flows and dikes are overlain by Oligocene to Miocene mudstones and sandstones (United Nations Development Program, 1978a, b; Mitchell et al., 1999). This succession covers much of the western forearc and eastern backarc basins to the Burman arc. Late Miocene to Quaternary basalt and andesite are characteristic of the Mount Popa, Taungthonlon, and Monywa areas. Mineral deposit styles: Alluvial gold occurs at Mansi, to the west of the northern portion of the arc, and in the Jade Mines region to the north (Goosens, 1978; United Nations Development Program, 1978c). In the Banmauk region lode gold was recovered from pyritic quartz lodes hosted by Tertiary andesitic tuffs and breccias at Kyaukpazat (Goosens, 1978) and in granodiorite at Sadwin (United Nations Development Program, 1978c). The Shangalon porphyry Cu-Au prospect is hosted by quartz diorite along the margin of the Cretaceous granodiorite batholith, 80 km southwest of Banmauk. The Monywa high-sulfidation deposit occurs in an uplifted portion of the arc about 50 km north of Mount Popa. More than 4.5 Mt of copper occurs in hypogene chalcocite-bearing breccia bodies associated with hypabyssal dacitic intrusions, which indicate radiometric ages of 19 Ma at Letpadaung and 13 Ma at Kyisintaung (App. 6; Kyaw Win and Kirwin, 1998). The gold content of the copper ore is minor. The intermediate-sulfidation quartz veins that occur within 5 km of the 16 17 chalcocite orebodies contain low levels of gold and silver (Kyaw Win and Kirwin, 1998). In the Indawgyi region of the backarc basin, immediately west of the Sagaing fault, Miocene (?) sedimentary rockhosted gold mineralization at Kyaukpahto is localized in a decalcified and silicified calcareous arkosic sandstone sequence (Male Formation) of probable Eocene age (Ye Myint Swe, 1990; Mitchell et al., 1999). Hydrothermal alteration includes decalcification, silicification, and sericitic and argillic styles. Gold is associated with fine-grained pyrite and arsenopyrite in quartz veinlets and as disseminated framboidal grains in silicified and brecciated sandstone. The region hosts numerous primary and alluvial gold occurrences that are spatially related to a 100-km-long segment of the Sagaing fault. 0361-0128/98/000/000-00 $6.00 APPENDICES 2 to 6 Grade-Tonnage and Age Characteristics for Major Gold and Copper ± Gold Deposits in the Cenozoic Magmatic Arcs of Southeast Asia and the West Pacific In these appendices, the total size and contained gold and copper contents (metric tonnes), grades (g/t Au and % Cu) and age of formation (Ma) are reported for all major and some minor deposits. These contents include conservative resource figures for the deposits and combined reserves and/or resources and past production for the mines, except where indicated otherwise. The grade-tonnage characteristics and age relationships are illustrated in Figures 17 and 18 in the printed part of the paper. 17 LS LS LS LS IS EP-XE-PM NE Japan EP-PM NE Japan EP-PM HS-IS IS IS IS IS IS IS VMS VMS VMS VMS VMS XE-PM IS IS LS LS IS IS LS Konomai Sanru Kitano-o Hokuryu Ohgane 0361-0128/98/000/000-00 $6.00 Toyoha Osarizawa Hosokura Teine Sado Takatama Chitose Shizukari 18 Todoroki Koryu Nurukawa Hanaoka Kosaka Shakanai Yoichi Ashio Bajo Ohmori Taio Hoshino Seigoshi Rendaiji Toi Izu-Bonin Izu-Bonin Izu-Bonin SW Japan SW Japan SW Japan SW Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan NE Japan Kuril Kuril Kuril Kuril Style Deposit Magmatic arc Izu Izu Izu North Kyushu North Kyushu Chugoku North Kyushu Tohoku Southwest Hokkaido Southwest Hokkaido Tohoku Tohoku Tohoku Tohoku Southwest Hokkaido Southwest Hokkaido Southwest Hokkaido Tohoku Tohoku SW Hokkaido Tohoku Southwest Hokkaido Tohoku Southwest Hokkaido Northeast Hokkaido Northeast Hokkaido Northeast Hokkaido Northeast Hokkaido Region/district 1.3 0.6 1.3 5.7 24.9 1.0 41.8 27.9 8.7 1.1 1.6 2.9 15 1.4 20 28.5 0.4 0.3 11.4 0.9 0.5 2.5 2.3 1.05 Metric tonnes Cu (million t) (%) 300 Contained Cu (000s t) 9.3 4.0 10.8 6.3 0.12 615 6.8 0.1-0.2 960 0.4-0.7 600 0.3-2.0 100 9 7 14.5 10 5.1 7.5 0.35 0.15 5 8.2 6.4 7.4 5.9 Au (g/t) 12 3 14 3 13 1 36 3 7 6 8 23 29 77 11 3 7 4 2 2 73 7 3 Contained Au (t) Japan Mining Industry Association (1978) Japan Mining Industry Association (1978) Japan Mining Industry Association (1978) Yamada et al. (1988) Ohmoto et al. (1983) Ohmoto et al. (1983) Ohmoto et al. (1983) Past production only; Watanabe (2002) Shikazono (1986); Furukawa Mining Co. Ltd. (1981) Izawa and Watanabe (2001) Shikazono (1986) Japan Mining Industry Association (1978) Izawa and Watanabe (2001) Japan Mining Industry Association (1978) Japan Mining Industry Association (1978) Saito et al. (1967); Shikazono (1986) Shikazono (1986) Shikazono (1986); Saito et al. (1967) Sakai and Oba (1970) Watanabe (1995) Watanabe (1995) Shikazono (1986); Saito et al. (1967) Shikazono (1986); Saito et al. (1967) Shikazono (1986); Saito et al. (1967) Kanbara and Kumita (1990) Mineland Osarizawa (unpub. data) Shikazono (1986) Reference for Grade-tonnage data Plio-Pleistocene 1.5 (K/Ar) 1.8-0.7 (K/Ar) 2.8-2.5 (K/Ar) 4.6-3.9 (K/Ar) 1.1 (K/Ar) 3.6-2.9 (K/Ar) Miocene 3.1-2.1 (K/Ar) 1.2 (K/Ar) Middle Miocene Middle Miocene Middle Miocene Middle Miocene 12.3 (K/Ar) 2.4 (K/Ar) 7.7 (K/Ar) 3.5-3.3 (K/Ar) 24.1-22.1 (K/Ar) 14.5-13.4 (K/Ar) 4.4-4.0 (K/Ar) Miocene 5.8 (K/Ar) 2.9-0.5 (K/Ar) 11.4 (K/Ar) 13.7 (K/Ar) 12.9-12.2 (K/Ar) 12.4 (K/Ar) 7.7-7.4 (K/Ar) Age (Ma) (method) Grade-Tonnage and Age Charactersitics of Significant Gold and Copper Deposits in Cenozoic Magmatic Arcs of Japan and Taiwan Appendix 2 Sawai et al. (1998) and (2001) Hamasaki and Bunno (2002); Ministry of Internatinal Trade and Industry (1987b) Ministry of Internatinal Trade and Industry (1987b) Sawai et al. (2002) Sakota et al. (2000) Yuan et al. (1993) Sawai et al. (1992) Shimizu et al. (1998) Yamada et al. (1988) Ohmoto et al. (1983) Ohmoto et al. (1983) Ohmoto et al. (1983) Sawai and Itaya (1996) Watanabe (1991) Seki (1993) Sawai et al. (1992) Shikazono and Tsunakawa (1982) Sawai et al. (1992; Sawai and Itaya (1996) Ministry of International Trade and Industry (1987a), Shikazono and Tsunakawa (1982) Sawai et al. (1989) Hirai et al. (2000) Yahata et al. (1999) Yahata et al. (1999) Sugaki and Isobe (1985) Maeda (1996) Reference for age 18 0361-0128/98/000/000-00 $6.00 HS IS IS LS LS Iwato Kushikino Fuke Hishikari Yamagano 19 Ryukyu Ryukyu Ryukyu Ryukyu Ryukyu South Kyushu South Kyushu South Kyushu South Kyushu South Kyushu South Kyushu South Kyushu 1.6 5.5 1.6 8.3 0.9 3 20 0.2 0.8 0.6 Metric tonnes Cu (million t) (%) 13.6 47.3 17.4 6.7 9.8 3.1 4.6 12.2 6.4 Au (g/t) 119 Contained Cu (000s t) 22 260 28 3 56 8 9 9 92 2 5 Contained Au (t) Izawa et al. (2001) Murakami and Feebrey (2001) Japan Mining Industry Association (1978) Japan Mining Industry Association (1978) Izawa and Watanabe (2001) Hayashi (2001); Nakamura et al. (1994) Hayashi (2001) Tan (1991); Wang et al. (1999) Hayashi (2001) Japan Mining Industry Association (1978) Japan Mining Industry Association (1978) Reference for Grade-tonnage data 1.6-1.2 (K/Ar) 1.1-0.7 (K/Ar) 2.0-1.9 (K/Ar) 2.2-1.4 (K/Ar) 3.7-3.4 (K/Ar) 4.7-4.2 (K/Ar) 3.7 (K/Ar) 4.5 (K/Ar) 1.0 (Ar/Ar, K/Ar) 2.5 (K/Ar) Pio-Pleistocene Age (Ma) (method) Ministry of International Trade and Industry (2000) Sekine et al. (2002) Murakami and Feebrey (2001) Ministry of International Trade and Industry (2000) Izawa et al. (1984); Togashi and Shibata (1984) Izawa and Zeng (2001) Ministry of International Trade and Industry (1985) Izawa et al. (1984) Ministry of Internati0nal Trade and Industry (1987b) Ministry of International Trade and Industry (1987b) Wang et al. (1999) Reference for age Notes: Grade-tonnage data includes combined resources and past production; mineralization styles: HS = high-sulfidation epithermal, IS = intermediate-sulfidation epithermal, LS = low-sulfidation epithermal, PM = polymetallic, VMS = Kuroko-type massive sulfide, XE = xenothermal LS Ryukyu HS Akeshi Okuchi South Kyushu Ryukyu Ryukyu Taiwan Ryukyu Chinkuashih HS (Taiwan) Kasuga HS Izu Izu-Bonin Izu Region/district Yugashima LS Magmatic arc Izu-Bonin Style Mochikoshi LS Deposit Appendix 2 (Cont.) 19 Style3 0361-0128/98/000/000-00 $6.00 PO CGD PO CGD PO CGD San Fabian Santo Nino* Lobo* 20 PO CGD PO CGD PO CGD PO CGD PO CGD PO CGD PO CGD SK HS IS IS IS IS IS Black Mountain* Kenon South Gambang Suluakan (Worldwide) Botilao Ullman* Dilong/Hale Thanksgiving* Lepanto* Antamok* Itogon* Acupan* Victoria* Teresa2 Dizon* Tayson San Antonio PO CGD PO CGD PO CGD Batong Buhay* IS PO CGD Tawi-Tawi Batong Buhay* PO CGD PO CGD Guinaoang Sto Thomas II* PO CGD Far South East PO CGD Deposit1 Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Western Luzon Western Luzon Western Luzon Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordilerra Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Luzon Central Cordillera Magmatic arc Zambales Batangas Marinduque Northwest Luzon Mankayan Mankayan Baguio Baguio Baguio Mankayan Baguio Northwest Luzon Baguio Northwest Luzon Baguio Mankayan Baguio Baguio Bobok Northwest Luzon Baguio Baguio San Fabian Mankayan Baguio Mankayan Region/district 187 336 195 1 7.3 11 31.1 40.7 1.1 35 38 82 123 55.6 62 62 159 107 210 286 314 326 449 650 0.36 0.31 0.57 2.78 0.5 0.34 0.52 0.35 0.35 0.38 0.38 0.39 0.6 0.28 0.35 0.27 0.37 0.38 0.65 Metric tonnes Cu (million t) (%) 0.93 0.35 0.1 13.0 5.3 7.3 3.92 3.29 11.6 0.35 0.33 0.19 0.13 0.32 0.33 0.33 0.16 0.25 0.25 0.2 0.21 0.37 0.7 1.33 Au (g/t) 706 1042 1112 1131 175 129 426 431 195 236 236 620 642 588 1001 848 1206 1616 4225 Contained Cu (000s t) 182 118 20 13 39 80 97 122 315 134 13 12 13 16 16 18 20 20 25 27 53 57 66 121 314 865 Contained Au (t) 1.4-1.3 (K/Ar) 5.5 (K/Ar) 7 3.1-2.9 (Ar/Ar) 4.6(K/Ar) 7 1.5 (K/Ar) 20.6 3.5 (K/Ar) 1.5 (K/Ar) 1.4-1.3 (K/Ar) Age (Ma) 1.15 (?) Singer et al. (2002) 2.7 (K/Ar) Singer et al. (2002) 20.5 Sillitoe and Gappe (1984) TVI Pacific Inc.(1995) Waters (2004) B. Andam (pers. commun., 1996); Benquet Corp., (1994) (estimate) Itogon-Suyoc Mining Pleistocene(?) Incorporated (1993, 1994) (estimate) Bureau of Mines and 0.65 (K/Ar) Geo-Sciences (1986); Benquet Corp. (1995) (estimate) Claveria et al. (1999) 1.15 (K/Ar) Mitchell and Leach (1991) Claveria et al. (1999) Sillitoe and Gappe (1984) Sillitoe and Gappe (1984) Sillitoe and Gappe (1984) Sillitoe and Gappe (1984) Yumul (1980) Metal Mining Agency of Japan (1977) Sillitoe and Gappe (1984) Singer et al. (2002) TVI Pacific Inc. (1995) Sillitoe and Gappe(1984) Mining Journal (14 Oct. 1994) Research Information Unit (2002) Singer et al. (2002) Singer et al. (2002) Claveria et al. (1999) Reference for grade-tonnage data Grade-Tonnage and Age Charactersitics of Significant Gold and Copper Deposits in Cenozoic Magmatic Arcs of the Philippines Appendix 3 Sillitoe (1989) Singer et al. (2002) Inferred: Hedenquist et al. (2001) Hedenquist et al. (2001) Cooke et al. (1996) Inferred from Cooke et al. (1996) Hedenquist et al. (2001) Sillitoe (1989) Singer et al. (2002) Waters (2004) Singer et al. (2002) Singer et al. (2002) Singer et al. (2002) Sillitoe and Angeles (1985) Singer et al. (2002) Sillitoe (1989) Hedenquist et al. (2001) Reference for age 20 Philippines Philippines Philippines Philippines Philippines Philippines Philippines PO CGD PO CGD PO CGD PO CGD PO CGD PO CGM HS IS IS IS IS DS/IS VMS VMS PO CGD POCGD POCGD IS IS IS VMS PO CGD IS PO CGM PO CGM PO CGM Kingking Boyongun Bayugo Amacan * Mapula Larap (Matanlang) Nalesbitan * Placer* 0361-0128/98/000/000-00 $6.00 Longos Point* Masara* Co-o * Siana* 21 Sulat Rapu-Rapu Basay* Hinobaan Sipalay* Masbate* Bulawan* Sibutad Canatuan Tampakan T'Boli Lutopan* Biga * Carmen* Rapu-Rapu Negros Negros Negros Masbate Central Samar Central East Mindanao Surigao Masara Camarines Norte Surigao Camarines Norte Camarines Norte Camarines Norte Surigao Surigao Masara Masara Zambales Marinduque Isabela-Didipio Isabela-Didipio Isabela-Didipio Region/district Cebu Cebu Cebu Cotabato 533 395 390 2.4 21 2.3 900 14 7.1 262 440 807 14.5 32.5 0.9 4.8 3.9 3.2 39.9 0.5 0.43 0.43 1.85 0.75 1.23 0.44 0.41 0.47 0.61 0.35 0.37 0.4 116 78 65 7.6 0.35 0.6 0.41 0.52 0.4 0.43 400 250 20 177 124 55 27 Metric tonnes Cu (million t) (%) 0.31 0.25 0.24 5.5 1.12 2.23 0.3 2.9 2.54 0.29 0.14 0.05 4.25 0.62 7.3 5.42 8.65 12.0 1.63 0.4 1.23 0.40 0.36 0.6 0.6 0.6 0.12 1.0 0.24 1.04 Au (g/t) 2665 1699 1677 43 6750 87 1153 1804 3793 198 228 429 312 1447 1500 82 920 484 237 Contained Cu (000s t) 165 99 94 13 24 5 270 41 18 76 62 40 62 20 7 26 34 38 65 26 9 46 28 167 150 12 21 120 13 28 Contained Au (t) 2.1 (K/Ar) 15 (K/Ar) 23.2 (K/Ar) 25 (K/Ar) Age (Ma) 3.2 (U/Pb) Pleistocene 14.4 (K/Ar) ?30 (K/Ar) 17.5 ?30 (K/Ar) Late Miocene Miocene 2.6-2.3 (Ar/Ar) 4.3 (K/Ar) Pliocene 20.5 Pliocene Research Institute Unit (2002) Sillitoe and Gappe (1984) 108 (K/Ar) Sillitoe and Gappe (1984) Sillitoe and Gappe (1984) Sillitoe and Gappe (1984) United Nations Development Program (1992) Manila Mining Corporation (1993, 1994); Mitchell and Leach (1991) (estimate) United Nations Development Program (1992) Mitchell and Leach (1991); White et al. (1995) United Nations Development Program (1992) Bureau of Mines and Geo-Sciences (1986); Mitchell and Leach (1991) (estimate) Bureau of Mines and Geo-Sciences (1986) TVI-Pacific (2003b) Singer et al. (2002) Singer et al. (2002) Singer et al. (2002) Mitchell and Leach (1991) (estimate) Metals Economics Group (1994) Jimenez et al. (2002) TVI-Pacific (2003a) Rohrlach et al. (1999) Pliocene 2.6-2.3 (Ar/Ar) 2.6-2.3 (Ar/Ar) Sillitoe and Gappe (1984) Late Miocene Sillitoe and Gappe (1984) Late Miocene Sillitoe and Gappe (1984) Sillitoe and Gappe (1984) Singer et al. (2002) Singer et al. (2002) Research Information Unit (2002) Singer et al. (2002) Feebrey (2003) Reference for grade-tonnage data Walther et al. (1981) R. Loucks, pers. commun. (2002) Jimenez et al. (2002) Sillitoe (1989) Divis (1983) Singer et al. (2002) Divis (1983) Mitchell and Leach (1991) Mitchell and Leach (1991) Waters (2004) Sillitoe (1989) Sillitoe (1989) Singer et al. (2002) Sillitoe et al. (1990) Sillitoe (1989) Waters (2004) Waters (2004) Mitchell and Leach (1991) Mitchell and Leach (1991) Singer et al. (2002) Walther et al. (1981) Wolfe et al. (1999) Mitchell and Leach (1991) Reference for age Notes: Grade-tonnage data includes combined resources and past production 1 Present or historic mines are indicated by * 2 The Teresa gold reserve figure is not included in the endowment estimates quoted in the text or figures. 3 Mineralization styles: DS = disseminated sedimentary rock-hosted, HS = high-sulfidation epithermal, IS = intermediate-sulfidation epithermal, LS = low-sulfidation epithermal, PO CGD = porphyry copper-gold, PO CGM = porphyry copper-gold-molybdenum, SK = skarn, VMS = volcanic-associated massive sulfide Cebu Cebu Cebu Cotabato Sulu-Zamboanga Zamboanga Sulu-Zamboanga Zamboanga Cotabato Cotabato Masbate-Negros Negros Philippines Masbate-Negros Masbate-Negros Masbate-Negros Masbate-Negros Philippines Philippines Philippines Philippines Philippines Philippines Western Luzon Sierra Madre Cordon Cordon Cordon PO CGD PO CGD PO CGD PO CGD IS Pisumpan Tapian* Dinkidi Marian Runruno Magmatic arc Style3 Deposit1 Appendix 3 (Cont.) 21 0361-0128/98/000/000-00 $6.00 North Sulawesi North Sulawesi PO CGD PO CGD PO CGD PO CGD PO CGD HS IS IS IS IS IS Gn. Pani Toka Tindung Doup Lanut* Bolangitang Mesel Deposits* DS 22 SK Kucing Liar IS IS IS Gn. Pongkor* Lebong Tandai* Lebong Donok* Tangse Martabe DOM Ertsberg* Ertsberg East (IOZ/DOZ)* Big Gossan Wabu PO CGD Medial New Guinea Grasberg* (reserve) Sunda Sunda Sunda Medial New Guinea SK Medial New Guinea SK Medial New Guinea SK Medial New Guinea SK Medial New Guinea SK Medial New Guinea PO CMD Sunda HS Sunda IS IS IS PO CGD Halmahera Halmahera Halmahera Medial New Guinea PO CGD Halmahera North Sulawesi North Sulawesi North Sulawesi Gosowong* Kencana2* Toguraci* Grasberg* (resource) Kaputusan North Sulawesi North Sulawesi North Sulawesi North Sulawesi North Sulawesi North Sulawesi HS Bawone (Binebase) Cabang Kiri East Sungai Mak Kayubulan Ridge Bulagidun Tapadaa Motomboto North Sulawesi Sangihe Style3 Deposit1 Magmatic arc Bengkulu Bengkulu West Java Tangse Sibolga Carstenz 2.8 2.9 6.0 600 66.7 31 32.6 37 Carstenz Carstenz 210 117 320 1877 0.99 1.7 0.41 4000 70 9.7 -- 12 5.5 12.3 30 136 84 75 14.4 43 2 4.5 0.15 1.67 2.3 2.69 1.14 1.41 1.04 0.6 0.3 0.43 0.76 0.76 0.61 0.54 2.0 Metric tonnes Cu (million t) (%) Carstenz Carstenz Carstenz Carstenz Gosowong Gosowong Gosowong Carstenz Bacan Kotamobagu Gorontalo Kotamobagu Kotamobagu Kotamobagu Marissa Gorontalo Gorontalo Gorontalo Marissa Gorontalo Gorontalo Sangihe Region/district 15.5 14.3 17.1 1.74 0.42 0.8 1.02 0.9 2.16 1.41 1.04 27 41 27 0.64 0.21 6.45 1.6 2.80 2.85 1.35 0.58 0.39 0.33 0.68 0.08 1.5 1.37 Au (g/t) 900 518 750 995 2394 4512 19521 24000 210 585 638 570 88 232 40 Contained Cu (000s t) 43 41 103 116 13 26 38 189 253 451 1952 27 70 11 2560 15 63 11 19 15 35 41 79 33 25 10 3 3 6 Contained Au (t) van Leeuwen (1994) Levet et al. (2003); Sutopo et al. (2003) Basuki et al. (1994); van Leeuwen (1994) van Leeuwen (1994) van Leeuwen (1994) Widodo et al. (1999) Mertig et al. (1994) Widodo et al. (1999) Coutts et al. (1999) O'Connor et al. (1999) Widodo et al. (1999) (open pit and underground) Widodo et al. (1999) Olberg et al. (1999) Mining News, 2004 Intierra (2003) van Leeuwen (1994) van Leeuwen (1994) van Leeuwen (1994) van Leeuwen (1994) van Leeuwen (1994) van Leeuwen (1994) van Leeuwen (1994) van Leeuwen (1994) (approximate) van Leeuwen (1994); Carlile and Mitchell (1994) Gold Gazette Asian Edition (April 1999) van Leeuwen (1994) Research Information Unit (2002) Carlile and Mitchell (1994) (estimate only) Newmont Mining (1994) van Leeuwen (1994) Reference for grade-tonnage data Miocene 8.5 (K/Ar) 13-9 Pliocene(?) 3.1-2.6 (K/Ar) 3.1-2.6 (K/Ar) ~3 3.1-2.6 (K/Ar) 6.6-5.2 (K/Ar) ~3 3.3-2.7 (K/Ar) 2.9-2.4 (Ar/Ar) Pliocene Pliocene 3.3-2.7 (K/Ar) Late MiocenePliocene Neogene Neogene Neogene 2.4 (K/Ar) 3.3-3.1 (Ar/Ar) 2.9 (K/Ar) Late Pliocene 2.4 (K/Ar) 8.8 (K/Ar) 3.75 (K/Ar) 1.9 (K/Ar) Miocene Age (Ma) Grade-Tonnage and Age Charactersitics of Significant Gold and Copper Deposits in Cenozoic Magmatic Arcs of Indonesia and Borneo Appendix 4 Jobson et al. (1994) Mertig et al. (1994); McDowell et al. (1996) Mertig et al. (1994); McDowell et al. (1996) Mertig et al. (1994); McDowell et al. (1996) Mertig et al. (1994); McDowell et al. (1996) van Leeuwen (1994) B. K. Levet, pers. commun. (2003) Marcoux and Milesi (1994) O'Conner et al. (1999) Carlile and Mitchell (1994) Olberg et al. (1999) Olberg et al. (1999) Olberg et al. (1999) MacDonald and Arnold (1994); McDowell et al. (1996) MacDonald and Arnold (1994); McDowell et al. (1996) Widodo et al. (1999) Garwin et al. (1995) White et al. (1995) Carlile et al. (1990) Moyle et al (1997) Pearson and Caira (1999) Perello (1994) Perello (1994) Perello (1994) Lubis et al. (1994) Singer et al. (2002) Perello (1994) Carlile et al. (1990) Reference for age 22 IS IS IS IS PO CGD East Sunda PO CGD East Sunda IS Banda VMS-HS Banda IS IS IS IS DS Cibaliung Cikondang Mangani* Way Linggo Batu Hijau* Elang Soripesa Wetar Deposits* Kelian* 0361-0128/98/000/000-00 $6.00 Mount Muro* Mirah Masupa Ria Bau Deposits (Sarawak)* 23 Meratus 0.48 0.35 0.44 1.8 1.9 0.5 4.3 12.8 1.96 3.1 1.85 4.2 0.4 0.35 6.5 9.1 10.9 10.4 3.1 Au (g/t) 941 2100 7216 Contained Cu (000s t) 8 42 98 31 4 12 51 179 240 1 23 574 6 4 8 14 24 Contained Au (t) 3.7 (U/Pb)4 PlioPleistocene(?) Age (Ma) Research Information Unit (2002) van Leeuwen (1994) Cox (1992) (estimate includes Tai Parit and Jugan) Singer et al. (2002) Research Information Unit (2002) van Leeuwen (1994) Research Information Unit (1997) van Leeuwen (1994) 7.0 (K/Ar); 6.8-6.4 (K/Ar) 13-10 (K/Ar) 25 (K/Ar) Early Miocene(?) 20 (K/Ar) Maula and Levet (1996) 2.7 (U/Pb)4 Carlile and Mitchell (1994) van Leeuwen (1994) 5-4; 4.7 van Leeuwen (1994) Research Information Unit (2002) Clode et al. (1999) Research Information Unit (1997) Research Information Unit (2002) van Leeuwen (1994) Reference for grade-tonnage data Metal Mining Agency of Japan (1985) (on felsic intrusions) Imai (2000); Bellon and Rangin (1991) Thompson et al. (1994) Simmons and Browne (1990); Thompson et al. (1994) Sewell and Wheatley (1994); van Leeuwen (1994) van Leeuwen et al. (1990) Fletcher et al. (2000); Garwin (2000, 2002a) Garwin (2000) Marcoux and Milesi (1994) Reference for age Notes: Grade-tonnage data includes combined resources and past production, except for Grasberg, IOZ/DOZ, DOM, Big Gossan, Kucing Liar deposits, which include reserves as of December 1998 1 Present or historic mines are indicated by * 2 The Kencana resource figure is not included in the endowment estimates quoted in the text or figures 3 Mineralization styles: DS = disseminated sedimentary rock-hosted, HS = high-sulfidation epithermal, IS = intermediate-sulfidation epithermal, LS = low-sulfidation epithermal, PO CGD = porphyry copper-gold = PO CMD = porphyry copper-molybdenum, SK = skarn, VMS = volcanic-associated massive sulfide or exhalative 4 206Pb/238U ages of zircons using a sensitive high-mass resolution ion microprobe (SHRIMP II) MeratusSumatra 4.3 IS Sungai Keruh Central Sulawesi 22 Arc unrelated? IS Awak Mas 7.3 0.3 6.0 16.5 97 5.4 600 1640 0.9 0.41 0.7 1.3 7.8 Metric tonnes Cu (million t) (%) 196 Central Kalimantan Central Kalimantan Bau Central Kalimantan Central Kalimantan West Sumbawa East Sumbawa Wetar West Sumbawa Mangani Lampung West Java West Java Bengkulu Region/district Mamut (Sabah)* PO CGD Kinabalu Pluton Mamut-Nungok Central Kalimantan Central Kalimantan Central Kalimantan Central Kalimantan Central Kalimantan Sunda Sunda Sunda Sunda Sunda IS Rawas* Magmatic arc Style3 Deposit1 Appendix 4 (Cont.) 23 Style2 Magmatic arc or belt 0361-0128/98/000/000-00 $6.00 24 Inner Melanesian Inner Melanesian Inner Melanesian Inner Melanesian Inner Melanesian Outer Melanesian Bougainville Island 1397 Outer Melanesian Lihir Island 420 (Tabar-Feni arc) PO CGD PO CGD PO CGD HS HS PO CGD PO CGD PO CGD PO CGD HS PO CGD ?LS LS, PO CGD IS Freida River Wafi River Yandera Nena Wafi River Arie Plesyumi Esis Kulu Wild Dog (Mt. Sinivit) Panguna* Ladolam* Kabang Woodlark* 338 69 18 1060 100 1.5 0.46 0.32 0.42 1.63 0.52 1.3 0.4 0.54 0.64 3.7 1.4 0.55 3.28 5.83 0.1 0.81 2.6 0.31 0.6 13.8 3.1 2.3 1.9 3.7 1.0 1.38 2.1 5.8 0.6 0.1 0.63 Au (g/t) 6426 528 1420 1125 5512 1300 340 351 4480 Contained Cu (000s t) 10 6 768 1378 6 34 56 47 329 60 21 29 5 10 28 55 77 78 487 51 7 441 Contained Au (t) Russell (1990) Clark (1990) Lihir Gold (2003); Research Information Unit (2002) Christopher (2002) Lindley (1990) Hall et al. (1990) Tau-Loi and Andrew (1998) Watmuff (1978) Bainbridge et al. (1998) Tau-Loi and Andrew (1998) Singer et al. (2002) Semple et al. (1998) Denwer and Mowat (1998) Chapple and Ibil (1998) McNeil (1990) Carswell (1990) Hutton et al. (1990) Reference for age 4.2 (K/Ar) 5.9 (Ar-Ar) 4.4 1.6 (K/Ar) Chapple and Ibil (1998) 12.3 (K/Ar) <0.5 (K/Ar) 3.4 (K/Ar) 0.35-0.10 (K/Ar) Russell (1990); Russell and Finlayson (1987) Clark (1990) Moyle et al. (1990); Davies and Ballantyne (1987) Sillitoe (1989) 3.8-2.4 (K/Ar) Denwer and Mowat (1998); Page and McDougall (1972) Pliocene Langmead and McLeod (1990) 12 (K/Ar) Whalen et al. (1982) 14 (K/Ar) Tau-Loi and Andrew (1998) 7 Singer et al. (2002) 12 (K/Ar) Hall et al. (1990) 14 (K/Ar) Tau-Loi and Andrew (1998) 15 Singer et al. (2002) 25-24 (K/Ar) Titley (1978) 25 (K/Ar) Hine et al. (1978) 22 (K/Ar) Hine and Mason (1978) 23-22 Lindley (1990) Pleistocene 3.8-2.4 (K/Ar) Hutton et al. (1990); Page and McDougall (1972) 3.8-2.4 (K/Ar) Carswell (1990); Page and McDougall (1972) Pliocene McNeil (1990) Appleby et al. (1996) Nelson et al. (1990) Arnold and Griffin (1978) Dugmore and Leaman (1998) Ronacher et al. (2002) 1.2-1.1 (K/Ar) Page (1976) Age (Ma) (method) Lewis and Wilson (1990) 3.5 (K/Ar) Dugmore and Leaman (1998) Handley and Henry (1990) Nelson et al. (1990) Singer et al. (2002) Singer et al. (2002) Reference for grade-tonnage data Notes: Grade-tonnage data includes combined resources and past production 1 Present or historic mines are indicated by * 2 Mineralization styles: HS = high-sulfidation epithermal, IS = intermediate-sulfidation epithermal, LS = low-sulfidation epithermal, PO CGD = porphyry copper-gold = SK, skarn 2.6 4.0 Manus Island 165 New Britain Island New Britain Island New Britain Island New Britain Island 0.96 West Sepik Morobe Province West Sepik Morobe Province Central Province Outer Melanesian Ambitle island (Tabar-Feni arc) Neogene island Woodlark Island arc remnant Maramuni Maramuni Maramuni Medial New Guinea Maramuni Maramuni IS 9.2 2.3 5.3 Tolukuma* Morobe Province Fergusson Island Fergusson Island IS 55 Morobe Province Hamata 56 Misima Island IS 37 Morobe Province 7.5 84 Enga Province Morobe Province 85 Central Province Gameta Medial New Guinea Medial New Guinea Medial New Guinea Medial New Guinea 65 Western Province IS IS 700 Metric tonnes Cu (million t) (%) Western Province Region/district Wau (Edie Creek)* Wapolu* PO CGD, SK Medial New Guinea Star Mt.(Futik) PO CGD Medial New Guinea Mt. Bini PO CGD, IS Medial New Guinea Porgera* ?IS, LS Medial New Guinea Hidden Valley IS Medial New Guinea Umuna / IS Medial Misima* New Guinea Kerimenge IS Medial New Guinea Ok Tedi* Deposit1 Grade-Tonnage and Age Charactersitics of Significant Gold and Copper Deposits in Cenozoic Magmatic Arcs of Papua New Guinea Appendix 5 24 25 Burman backarc DS/IS KyaukpahtoIndawgyi 4 0.40 226 Burman arc HS Monywa 0.40 905 Monywa Burman arc HS Monywa* (Letpadaung) Monywa* (Kyisintaung) Kyaukpahto * 0361-0128/98/000/000-00 $6.00 Notes: Grade-tonnage data includes combined resources and past production 1 Present or historic mines are indicated by * 2 Mineralization styles: DS = disseminated sedimentary rock-hosted, HS = high-sulfidation epithermal, IS = intermediate-sulfidation epithermal Miocene(?) 3.81 905 3620 15 Minproc (1985) Ivanhoe Mines (2003) 13 (K/Ar) Kyaw Win and Kirwin (1998) Kyaw Win and Kirwin (1998) Mitchell et al. (1999) 19 (K/Ar) Ivanhoe Mines (2003) Age (Ma) Reference for grade-tonnage data Contained Au (t) Contained Cu (000s t) Au (g/t) Metric tonnes Cu (million t) (%) Region/district Magmatic arc Style2 Deposit1 Appendix 6 Grade-Tonnage and Age Charactersitics of Significant Gold and Copper Deposits Associated with the Burman Arc of Myanamar Reference for age REFERENCES Abbott, M.J., and Chamalaun, F.H., 1981, Geochronology of some Banda arc volcanics: Bandung, Geological Research and Development Centre Special Publication 2, p. 253–268. Abiari, T.B., Samuel, K., and Sie, A., 1990, Mount Victor gold deposit, Kainantu: Parkville, Victoria, Australasian Institute of Mining and Metallurgy Monograph Series 14, v. 2, p. 1725–1729. Ali, J.R., and Hall, R., 1995, Evolution of the boundary between the Philippine Sea plate and Australia: Palaeomagnetic evidence from eastern Indonesia: Tectonophysics, v. 251, p. 251–275. 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