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... clasts indicate a genetic relationship with the pegmatite gabbro, they likely reflect a different pulse of magmatism. Based on the similar mineralogy of the albitite clast and the alkaline dike at Site 1277, we relate the 127 ± 4 Ma magmatism at Site 1070 with the contemporaneous alkaline event at S ...
... clasts indicate a genetic relationship with the pegmatite gabbro, they likely reflect a different pulse of magmatism. Based on the similar mineralogy of the albitite clast and the alkaline dike at Site 1277, we relate the 127 ± 4 Ma magmatism at Site 1070 with the contemporaneous alkaline event at S ...
Ocean Drilling Program Scientific Results Volume 124
... (this volume) demonstrated that the organic material at Site 767 is largely of terrestrial derivation, and they noted no change in the character of the organic material across the red/green clay boundary. Basement was encountered at 786 mbsf at Site 767 and 422 mbsf at Site 770. Tholeiitic pillow ba ...
... (this volume) demonstrated that the organic material at Site 767 is largely of terrestrial derivation, and they noted no change in the character of the organic material across the red/green clay boundary. Basement was encountered at 786 mbsf at Site 767 and 422 mbsf at Site 770. Tholeiitic pillow ba ...
The Hindu Kush Seismic Zone as a Paradigm
... whereby a narrow zone of ∼100-km-thick crust was exhumed vertically upward by horizontal contraction between two rigid blocks and subsequent erosion. Although nowhere on Earth today is the crust thicker than ∼75 km, heating during thermal equilibration of such a thick root would destroy any UHP rock ...
... whereby a narrow zone of ∼100-km-thick crust was exhumed vertically upward by horizontal contraction between two rigid blocks and subsequent erosion. Although nowhere on Earth today is the crust thicker than ∼75 km, heating during thermal equilibration of such a thick root would destroy any UHP rock ...
Differential preservation in the geologic record of intraoceanic arc
... preserved, in the translation from modern processes to the ancient record of intraoceanic arcs. Composition of accreted arc terranes differs as a function of arc–continent collision geometry. ‘Forwardfacing’ collision can accrete an oceanic arc on to either a passive or an active continental margin, ...
... preserved, in the translation from modern processes to the ancient record of intraoceanic arcs. Composition of accreted arc terranes differs as a function of arc–continent collision geometry. ‘Forwardfacing’ collision can accrete an oceanic arc on to either a passive or an active continental margin, ...
The Architecture, Chemistry, and Evolution of - Cin
... it extends onto the crust of the Alaska Peninsula. 2.4.3. Major continental arcs outside the Americas. Several post–Rodinia breakup (<700 Ma) continental arcs occur outside of the Americas. Older Precambrian arcs exist as well, but their preservation is poor due to subsequent orogenic reworking. Amo ...
... it extends onto the crust of the Alaska Peninsula. 2.4.3. Major continental arcs outside the Americas. Several post–Rodinia breakup (<700 Ma) continental arcs occur outside of the Americas. Older Precambrian arcs exist as well, but their preservation is poor due to subsequent orogenic reworking. Amo ...
deep sea drilling in the northern indian ocean
... and extrusive volcanic rocks represent the most recent snapshot of geological events. Beneath this cover, buried in sedimentary sections and the underlying crust, is a rich history of the waxing and waning of glaciers, the creation and aging of oceanic lithosphere, the evolution and extinction of mi ...
... and extrusive volcanic rocks represent the most recent snapshot of geological events. Beneath this cover, buried in sedimentary sections and the underlying crust, is a rich history of the waxing and waning of glaciers, the creation and aging of oceanic lithosphere, the evolution and extinction of mi ...
Seismological observations in Northwestern South America
... The cause of tectonic deformation in northwestern South America and its link to upper mantle structure and flow are debated. We use a combination of broadband and short period travel time seismic data for P-waves to show that observations are consistent with the presence of two subduction segments in ...
... The cause of tectonic deformation in northwestern South America and its link to upper mantle structure and flow are debated. We use a combination of broadband and short period travel time seismic data for P-waves to show that observations are consistent with the presence of two subduction segments in ...
Crustal contributions to arc magmatism in the Andes of Central Chile
... a single arc segment, beneath which the nature and age of the downgoing plate and the rate and geometry of subduction all appear to be nearly constant. In contrast, the thickness and average age of the continental crust markedly increase northward along the segment. Although the principal magma sour ...
... a single arc segment, beneath which the nature and age of the downgoing plate and the rate and geometry of subduction all appear to be nearly constant. In contrast, the thickness and average age of the continental crust markedly increase northward along the segment. Although the principal magma sour ...
Diapirs as the source of the sediment signature in arc lavas
... melt’ signature in arc lavas2–4 . Subduction zone thermal models that incorporate temperature- and stress-dependent viscosity5–8 produce slab-top temperatures above the fluid-saturated sediment solidus (>600–700 ◦ C at ≤3 GPa; refs 9,10), and H2 O/Ce and H2 O/K ratios in melt inclusions from arc lav ...
... melt’ signature in arc lavas2–4 . Subduction zone thermal models that incorporate temperature- and stress-dependent viscosity5–8 produce slab-top temperatures above the fluid-saturated sediment solidus (>600–700 ◦ C at ≤3 GPa; refs 9,10), and H2 O/Ce and H2 O/K ratios in melt inclusions from arc lav ...
The Architecture, Chemistry, and Evolution of Continental Magmatic
... it extends onto the crust of the Alaska Peninsula. 2.4.3. Major continental arcs outside the Americas. Several post–Rodinia breakup (<700 Ma) continental arcs occur outside of the Americas. Older Precambrian arcs exist as well, but their preservation is poor due to subsequent orogenic reworking. Amo ...
... it extends onto the crust of the Alaska Peninsula. 2.4.3. Major continental arcs outside the Americas. Several post–Rodinia breakup (<700 Ma) continental arcs occur outside of the Americas. Older Precambrian arcs exist as well, but their preservation is poor due to subsequent orogenic reworking. Amo ...
Southeast Asia`s changing palaeogeography
... with Cathaysian affinities suggesting an origin in Asia and may mark a subduction margin continuing south from East Asia at which ophiolitic, island arc and microcontinental crustal fragments were added during the Mesozoic. Southwest Borneo is interpreted here to be a continental block rifted from th ...
... with Cathaysian affinities suggesting an origin in Asia and may mark a subduction margin continuing south from East Asia at which ophiolitic, island arc and microcontinental crustal fragments were added during the Mesozoic. Southwest Borneo is interpreted here to be a continental block rifted from th ...
Ophiolites and Their Origins
... phiolites are suites of temporally and spatially associated ultramafic, mafic, and felsic rocks that are interpreted to be remnants of ancient oceanic crust and upper mantle. Ophiolites show significant variations in their internal structure, geochemical fingerprints, and emplacement mechanisms. The ...
... phiolites are suites of temporally and spatially associated ultramafic, mafic, and felsic rocks that are interpreted to be remnants of ancient oceanic crust and upper mantle. Ophiolites show significant variations in their internal structure, geochemical fingerprints, and emplacement mechanisms. The ...
Tectonic wedging along the rear of the offshore Taiwan accretionary
... strata in the vicinity of line EW9509.49. This feature may represent the western extent of the submerged portion of the island arc. To the west, the forearc basement dips smoothly to the west and may extend under the tectonic wedge, although the basement reflector is weak and not imaged beneath the ...
... strata in the vicinity of line EW9509.49. This feature may represent the western extent of the submerged portion of the island arc. To the west, the forearc basement dips smoothly to the west and may extend under the tectonic wedge, although the basement reflector is weak and not imaged beneath the ...
Crustal structure of the central Sunda margin at the onset of oblique
... exhibit a water depth of approximately 6750 m. The topography between the deformation front and an active backstop structure that was recognized around CDP 25 500 displays several distinct ridges and troughs in which small amounts of recent sediment are trapped. Landwards, a rough basement top (Fig. ...
... exhibit a water depth of approximately 6750 m. The topography between the deformation front and an active backstop structure that was recognized around CDP 25 500 displays several distinct ridges and troughs in which small amounts of recent sediment are trapped. Landwards, a rough basement top (Fig. ...
1 The tectonic agenda
... Plate tectonicscan only provide a useful description if the number of plates remains small; if large numbers of plates are needed to describe the behaviour of the lithosphere, then the description becomes sufficiently complicated to be rendered useless. Does plate tectonics provide a useful descript ...
... Plate tectonicscan only provide a useful description if the number of plates remains small; if large numbers of plates are needed to describe the behaviour of the lithosphere, then the description becomes sufficiently complicated to be rendered useless. Does plate tectonics provide a useful descript ...
EOCENE TECTONIC EVOLUTION OF NW MEXICO (SONORA and
... To restore the Baja-Borderland Block to its Eocene position taking into account the paleomagnetic data obtained on the Eocene Poway Formation of San Diego, the Baja-Borderland Block should be (a) moved some 1200 km south-west-wards along the eastern limit of the Baja-Borderland Block, bringing San D ...
... To restore the Baja-Borderland Block to its Eocene position taking into account the paleomagnetic data obtained on the Eocene Poway Formation of San Diego, the Baja-Borderland Block should be (a) moved some 1200 km south-west-wards along the eastern limit of the Baja-Borderland Block, bringing San D ...
Plate-kinematics and crustal dynamics of circum
... defining the western margins of the American plates in order to explain the well-known Triassic-Jurassic magmatic belt from at least California to Peru (Jaillard et al., 1990; Jones et al., 1995; Romeuf et al., 1997; Noble et al., 1997). In the Jurassic (Fig. 3), this west-facing arc system must als ...
... defining the western margins of the American plates in order to explain the well-known Triassic-Jurassic magmatic belt from at least California to Peru (Jaillard et al., 1990; Jones et al., 1995; Romeuf et al., 1997; Noble et al., 1997). In the Jurassic (Fig. 3), this west-facing arc system must als ...
Comparative Study of Quaternary Arc Volcanic Belts: Southern Chile
... the thickness of the crust is nearly 30 km (Fig. 7B). From north to south Tokachi, Hakkoda, Tamagawa, Onikobe, and Shirakawa erupted during the early Qua- ...
... the thickness of the crust is nearly 30 km (Fig. 7B). From north to south Tokachi, Hakkoda, Tamagawa, Onikobe, and Shirakawa erupted during the early Qua- ...
Alteration of the oceanic lithosphere and its implications for seafloor
... referred to as the “Penrose ophiolite model” or “Penrose-type crust”, defined during a Penrose conference and published in Geotimes in 1972. This model is generally applicable for crust formed at fast spreading ridges, such as the East Pacific Rise, where melt supply is able to keep up with extensio ...
... referred to as the “Penrose ophiolite model” or “Penrose-type crust”, defined during a Penrose conference and published in Geotimes in 1972. This model is generally applicable for crust formed at fast spreading ridges, such as the East Pacific Rise, where melt supply is able to keep up with extensio ...
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... of sources, migration upon which the requisite thermal flux is superimposed. If so, we can therr seek these conditions in the geologic record of sedimentary basins. PLATE INIEMCTIO}'IS are spherical caps, or arcuat.e slabs, The plates of plate tectonics of the earthts lithosphere which is thicker or ...
... of sources, migration upon which the requisite thermal flux is superimposed. If so, we can therr seek these conditions in the geologic record of sedimentary basins. PLATE INIEMCTIO}'IS are spherical caps, or arcuat.e slabs, The plates of plate tectonics of the earthts lithosphere which is thicker or ...
Summary of Research Projects John W. Shervais Department of Geology Professor and Head
... of the NSF “MARGINS” initiative. Quoting from the MARGINS program announcement: “At convergent margins, raw materials (sediments, oceanic crust and upper mantle) are fed into the "subduction factory" where many processes (including dewatering, metamorphism, melting) under changing physical and chemi ...
... of the NSF “MARGINS” initiative. Quoting from the MARGINS program announcement: “At convergent margins, raw materials (sediments, oceanic crust and upper mantle) are fed into the "subduction factory" where many processes (including dewatering, metamorphism, melting) under changing physical and chemi ...
A Geochemical Study of Crustal Plutonic Rocks from the Southern
... Professor Rosemary Hickey-Vargas, Major Professor Two suites of intermediate-felsic plutonic rocks were recovered by dredges RD63 and RD64 (R/V KK81-06-26) from the northern wall of the Mariana trench near Guam, which is located in the southern part of the Izu-Bonin-Mariana (IBM) island arc system. ...
... Professor Rosemary Hickey-Vargas, Major Professor Two suites of intermediate-felsic plutonic rocks were recovered by dredges RD63 and RD64 (R/V KK81-06-26) from the northern wall of the Mariana trench near Guam, which is located in the southern part of the Izu-Bonin-Mariana (IBM) island arc system. ...
Depleted lithosphere, cold, trapped asthenosphere, and frozen melt
... extensive volcanism and metamorphism. It is also unclear whether the subduction that resulted in the accretion of Chilenia was west-verging or east-verging [5,7], but more recent works [7,12] seem to prefer the former. This would imply that no subduction has occurred beneath the Cuyania/Precordiller ...
... extensive volcanism and metamorphism. It is also unclear whether the subduction that resulted in the accretion of Chilenia was west-verging or east-verging [5,7], but more recent works [7,12] seem to prefer the former. This would imply that no subduction has occurred beneath the Cuyania/Precordiller ...
PDF format - gemoc - Macquarie University
... Major, trace element and Re-Os isotopic data were obtained in situ from individual sulfide grains enclosed in concentrate-derived minerals from the Lac de Gras area, Slave craton, by electron microprobe, quadrupole laser ablation microprobe (LAM) ICPMS and multicollector LAM ICPMS, respectively. The ...
... Major, trace element and Re-Os isotopic data were obtained in situ from individual sulfide grains enclosed in concentrate-derived minerals from the Lac de Gras area, Slave craton, by electron microprobe, quadrupole laser ablation microprobe (LAM) ICPMS and multicollector LAM ICPMS, respectively. The ...
Izu-Bonin-Mariana Arc
The Izu-Bonin-Mariana (IBM) arc system is an outstanding example of a plate tectonic convergent boundary. IBM extends over 2800 km south from Tokyo, Japan, to beyond Guam, and includes the Izu Islands, Bonin Islands, and Mariana Islands; much more of the IBM arc system is submerged below sealevel. The IBM arc system lies along the eastern margin of the Philippine Sea Plate in the Western Pacific Ocean. It is most famous for being the site of the deepest gash in Earth's solid surface, the Challenger Deep in the Mariana Trench. The IBM arc system formed as a result of subduction of the western Pacific plate. The IBM arc system now subducts mid-Jurassic to Early Cretaceous lithosphere, with younger lithosphere in the north and older lithosphere in the south, including the oldest (~170 million years old, or Ma) oceanic crust. Subduction rates vary from ~2 cm (1 inch) per year in the south to 6 cm (~2.5 inches) in the north. The volcanic islands that comprise these island arcs are thought to have been formed from the release of volatiles (steam from trapped water, and other gases) being released from the subducted plate, as it reached sufficient depth for the temperature to cause release of these materials. The associated trenches are formed as the oldest (most western) part of the Pacific plate crust increases in density with age, and because of this process finally reaches its lowest point just as it subducts under the crust to the west of it.The IBM arc system is an excellent example of an intra-oceanic convergent margin (IOCM). IOCMs are built on oceanic crust and contrast fundamentally with island arc built on continental crust, such as Japan or the Andes. Because IOCM crust is thinner, denser, and more refractory than that beneath Andean-type margins, study of IOCM melts and fluids allows more confident assessment of mantle-to-crust fluxes and processes than is possible for Andean-type convergent margins. Because IOCMs are far removed from continents they are not affected by the large volume of alluvial and glacial sediments. The consequent thin sedimentary cover makes it much easier to study arc infrastructure and determine the mass and composition of subducted sediments. Active hydrothermal systems found on the submarine parts of IOCMs give us a chance to study how many of earth's important ore deposits formed.