Download MGB-7 Key Officials

BOHOL PROFILE-GENERAL GEOLOGY







The Alicia Schist which appears to be Cretaceous, is the lowest
formation in Bohol area and the Ubay Volcanics which appear to be
Paleocene are exposed in the eastern to northern Bohol. Both units were
accreted by the Cretaceous Boctol Serpentinite and they were intruded by the
Paleocene Talibon Diorite.
Formations deposited after Miocene occur extensively in southeastern
to western portions and is overlain by the Pliocene to Pleistocene Maribojoc
Limestone.
The Alicia Schist occurs as elongated shape in N-S trend in eastern
flank of Bohol Island and is accompanied by the Boctol serpentinite. The unit
consists of medium grade green schist and mica schist.
The unit generally trends N10-60 E, and dips northwest or southwest.
Fractures parallel to the schistosity are observed at exposures with less
deformation.
The Ubay Volcanics occurs at the northeastern part of Bohol Island,
and consists of Paleocene dacite, pyroxene andesite and basalt. Various kinds
of alteration and various grades of weathering are observed. The relationship
to other formations are not clear.
The Calape Limestone Corby, et al, (1951) and Arco (1962) described
Late Eocene Cameria bearing limestones which occurs the southeast of
Tubigon, northwestern Bohol Island. It is now known that these limestones
are not exposed but floated.
The Ilihan shale is described as steeply dipping unit with interbeds of
sandy tuffs and calcareous volcanic rubble beds, and occurs at Ilihan Sur.
Tubigon, the present study gives an Oligocene age to this unit based on
paleontrogical interpretation. (Yolanda, 1988).
BOHOLPROFILE-GENERAL GEOLOGY







The Wahig Limestone is white to light gray and massive to bedded limestone rich in
small orbitoids. This unit overlies unconformably the Ubay Volcanics which is exposed widely in
the central and northern parts of Bohol and covers the untruded Talibon Diorite, Arco (1962)
reported this unit as Upper Oligocene to Miocene. However, more recent dating of samples of
this unit placed the age as ranging from Early to Middle Miocene (possible Early Miocene) (E.G.
Sajona, et al. 1986).
The Carmen Formation is distributed mainly in the eastern part of Bohol occupying 30 to
40 percent of the total island area. This low dipping thick sedimentary sequence is essentially
composed of shale, sandstone, slabby to massive limestone, conglomerate, siltstone, marl and
some Tuffaceous and siliceous facies. Arco (1962) reported this formation to be Middle to Upper
Miocene. However, samples obtained during this survey yielded fossils from Early to Middle
Miocene. The conglomerate of this formation occurs around Dimiao, the southern coast and
along Tanguhay River.
At the northeastern part of the island, occasional coal lenses in association with
Tuffaceous sandstone are observed.
The Sierra Bullones Limestone is massive limestone mainly exposed in the southeastern
part of Bohol. The upper part of the formation consists of white tuffaces-calcareous siltstone,
shale and mark. The limestone is mainly composed of medium to thick coralline beds,
biocalcarenite beds and reefal limestone. This formation overlies the Carmen Formation
unconformably. Almost 95 percent of the whole Anda Peninsula, in the southeastern part of
Bohol is covered by this limestone and it’s absence on the western part suggests the tilting and
subsequent submerging of the southeastern part, during the Late Miocene.
The Maribojoc Limestone occurs extensively in the western part of Bohol. It is mainly
massive or lagoonal limestone and creamy to brownish yellow. It is also coralline, porous and in
places marly or agglomeratic. The rocks resembles the Carcar Formation of Cebu. Bedding
planes are generally flat though poorly bedded. It is more likely that it was formed either after the
deposition of the Sierra Bullones Limestone during Late Miocene, or after the Jagna Andesite
activity (E.G. Sajona, et al. 1986).
The Maribojoc Limestone overlies unconformably the Sierra Bullones Limestone. It was
dated Pliocene through fossil studies, but it is inferred that the deposition continued to Pleistocene
(E.G. Sajona, et al. 1986) and this long deposition period suggests that the environment of this
area was stable during this time.
Alluvium is composed of silts, sands and gravel and is confined in alluvial plains and
coastal parts.
CEBU PROFILE-GENERAL GEOLOGY




The oldest rock unit in Central Cebu is the Tunlob Schist which is
probably of Jurassic age. This consists of chloritic orthoschists and
micaceous paraschists belonging to the albite-epidote-amphibolite facies of
moderate grade metamorphism.
The Mananga Group of Cretaceous to Paleocene age, overlies the
Tunlob Schist. This consists of limestone, clastic sedimentary rocks,
andesitic to basaltic pyroclastics and lava, calcareous mudstone,
conglomerate and sandstone. The group includes the Pandan Formation
(Corby et al.), Cansi Volcanics and Tuburan Limestone(Santos Yñigo, 1951).
Unconformably overlying the Mananga Group are the late(?) Eocene to
early Miocene sedimentary formations consisting of the Lutak Hill
Formation, Cebu Formation and Malubog Formation. The Lutak Hill
formation is mainly limestone with basal sandstone containing Lepidocyclina
and Nummulites. An upper Orbitoidal limestone, a lower clastic unit with
coal measures and a basal conglomerate (Guindaruhan) comprise the Cebu
Formation. The Malubog Formation is composed of mudstone, shale and
occasional beds of conglomerate, limestone and coal.
Middle Miocene rock formations unconformably overlie the older
rocks. First in the sequence is the Luka Formation consisting of interbedded
sandstone and mudstone with conglomerate and limestone lenses. The Uling
Limestone comes next and is a generally hard, massive limestone but partly
porous and coralline. A pinkish to reddish colored facie occurs at places. At
the top of the sequence is the Toledo Formation consisting of thin to thick
bedded sandstone and shale with occasional lenses of conglomeratic
limestone and calcarenite.
CEBU PROFILE-GENERAL GEOLOGY







The Late Miocene Maingit Formation unconformably overlies the older
rocks. The formation is composed of granule to cobble conglomerate with
interbedded shale, sandstone, limestone and conglomeratic limestone in the
lower part.
Unconformably overlying the older formations is the Barili Formation of
Late Miocene to Early Pliocene age. This consists of a Lower Limestone
member which is generally light brown in color, hard, coralline and porous
and an Upper Marl member which is poorly bedded and slightly sandy.
The Plio-Pleistocene Carcar Formation occupies the flanks of the island.
It is a dominantly coralline limestone, poorly bedded to massive and partly
dolomitic.
The Quaternary Alluvium occupies the low lying areas and the river
banks. This consists of detrital materials made-up of silt, sand and gravel.
The Lutopan Diorite intrudes the Mananga Group at places which have
been postulated to have brought the mineralization of economic quantity and
quality in the Central Cebu area.
The Bulacao Andesite of Late Miocence age also occur at places. This
consists of porphyritic andesite and partly intrusive breccia.
Serpentinized ultramafic and mafic rocks occurs as diapiric intrusions
along the major faults.
ORIENTAL NEGROS PROFILE-GENERAL GEOLOGY






Negros Island is made up of volcanic and Sedimentary rocks of
Cretaceous to Pleistocene age. The Basak Formation is the oldest rock
formation in the island. This consists of mainly of basalt with intercalated
meta-sediments and grayish volcanic wackes (GOP, 1982). The Pagatban
Formation intrudes into the Basak formation. It consists of quztrz diorite and
diorite occurring in medium to coarse grained granular porphyries and very
coarse grained gabbro.
Unconformably overlying the above formations is the Dacong Cogon
Limestone of Early Miocene to Middle Miocene in age. Overlying this
formation is the Cantoray Formation of middle to late Miocene age. It is a
thick sequence of well bedded sandstone and shale with unsorted grains and
shell fragments with carbonaceous composition.
The middle Miocene Paghumayan Formation overlies the older rocks.
This is composed of andesite and clastic andesitic rocks and tuffaceous rocks.
The Talave Formation of late Pliocene age unconformably overlies the
older formations. It consits of an upper limestone and related facies and a
lower interbedded sandstone, siltstone and shale.
The Caliling Limestone Formation unconformably overlies the older
formations. It is of upper Pliocene to Pleistocene limestone sequence. This
limestone is usually massive to thin bedded, coralline to conglomeratic and
sometimes dolomitic with occasional lenses of tuff and bentonitic tuff
(Salvado and Buenavista, 1984).
Quaternary Volcanics and Quternary Alluvium overlie the older rocks.
The former occupies large areas in the southeastern portion of the island and
along the northwest most section of the province. The latter is found along
floodplains, beaches, rivers and riverbanks.
SIQUIJOR PROFILE-GENERAL GEOLOGY







The geology of Siquijor Area is composed of four formations namely, Kanglasog Volcanics,
Basac Formation, Siquijor Limestone and Alluvium (Sorem, et al., 1851)
The lowest Kanglasog Volcanics is composed of volcanics breccia, agglomerates and a small
number of volcanic flows and occurs as independent peaks of rugged, sharp crested ranges. It is
overlain unconformably by the Basac Formation which consists of the Middle to Upper Miocene
sequence of tuffaceous, calcareous and clastic materials. The formation constitutes undulating
foothills elongated towards the coast. The youngest formation is the gently dipping Siquijor
Limestone dated Upper Pliocene to Pleistocene and occurs as topographically flat-flying coastal
plane, sea eroded cliffs and various terraces.
The Kanglasog Volcanics occurs at higher parts of the island and the type locality of the unit
is Mt. Kanglasog. The unit is composed of volcanic breccias, agglomerates and a small amount of
volcanic flows. The breccias and agglomerates consist of basaltic to andesitic and angular to
subangular fragments which are amygdaloidal, vesicular and irregular in size. They are cemented
with Tuffaceous sandy matrix. In weathered parts of the unit, pale colored fragments are scattered in
reddish yellow clayey matrix. Steeply dipping tuff is partly observed in the unit. Dark gray to black
tuff exhibits ripple marks suggesting marine deposition. However, most of the tuff appears to have
been deposited subareally. A small amount of volcanic flow occurs localized and it consist of
amygdaloidal basalt filled with zeolite and calcite in the cavities. Secondary manganese minerals
which occur in fractures and at boundaries of the flows and quartz-calcite veinlets are also seen. This
formation is assigned to Oligocene and covered by the Basac Formation unconformably.
The Basac Formation is composed of two intertonguing members of limestone members of
limestone and shall. The limestone member which lies above the shale member is well exposed at the
type locality of Basac. It is hard, cavernous and creamy to buff colored when fresh and gray to almost
black on weathered surface. At the basal part of the limestone member, brecciated zones contain
pieces of volcanic or pyroclastic rocks, it’s diameter are no longer than one centimeter.
Lepoidocyclina (Nephrolepidina) smatrensis is present in the lower portion of the interbedded
member and it indicates Middle Miocene (R.B. Rovillos, Jr., et al. 1985).
The Siquijor Formation is considered to be the youngest formation in the island, which has
gently dipping beds.
This formation is considered with massive, hard cavernous and fossiliferous limestone and
shows creamy to pinkish color on fresh outcrops and pale gray to black on weathered surface. Clastic
limestones, particularly calcarenites, contain large amount of foraminiferas. Calcirudite consisting of
limestone clasts in a sandy matrix are noted in various localities.
Alluvium consists of mud, clay, silt, sand and gravel and is confined to the coastal parts and
lower stream valleys.
Mineral Resources by Province
Province
Metallic
Non-Metallic
Bohol
Gold, Silver,
Manganese, chromite,
nickel, copper
Guano, Phosphate rock,
limestone, clay, silica
sand
Cebu
Gold, silver, iron &
ferrous alloy, copper
Limestone, Gypsum,
clay,
bentonite/bentonitic
clay, silica, feldspar
Oriental Negros
Gold, silver, magnetite
beach sand, copper,
aluminum (bauxite)
Clay, gypsum,
limestone, silica, tuff,
phosphate rock/guano.
sulfur
Siquijor
Manganese
Guano, phosphate rock,
limestone
Mineral Resources of Cebu

I. Metallic Mineral Deposits
– A. Precious Metals

A.1 Gold
– Major by-product of copper in Atlas Mines in Toledo City, Cebu average 0.23
g/DMT, production 42,950 oz in 1991
– Other prospects in Bgys. Sigpit, Maypay & Cambang-ug Toledo City, Bgy.
Buanoy, Balamban, Bgy. Garing, Consolacion and Binaliw-Guadalupe area.

A.2 Silver
– By-product of copper in ACMDC, Lutopan, Toledo City, averages 2.05
g/DMT
– Other prospects in Maypay, Matugan and Mabini- Panoypoy
– B. Non-ferrous Metals

B.1 Copper
– ACMDC is the only copper producing mine in the region, occur in
disseminated porphyry copper mineralization, in chalcopyrite and bornite as
veinlets, stockworks or disseminations
– Other prospects in Bgys. Sinsin & Sudlon, Cebu City; Maypay & Matugan

B.2 Lead
– Prospect in Bgy. Mabinay, Cebu City, occur as galena vein
Mineral Resources of Cebu…..

II Non-Metallic Mineral Deposits
– A. Cement Raw Material

A.1 Limestone
– Carcar limestone is utilized as main raw material for cement
production, 2 existing cements, Taiheiyo in San Fernando &
Cemex in Naga, La Farge (inactive) in Danao City

A.2 Shale and Graywacke
– Low lime component in cement production- Naga and San
Fernando

A.3 Silica
– Silica component in cement production - Pinamungajan
Mineral Resources of Cebu…..

II. Non-Metallic Mineral Deposits
– B. Ceramic Material

B.1 Clay
– Red burning clay suitable in making potteries, bricks and roofing tiles.
Occur in deltaic floodplains and backswamp areas – Liloan, Bgy.
Valladolid, Carcar, Bgy. Guinsay, Danao, Bgy. Kotkot, Compostela,
Toledo, Talisay, Pinamungajan, Asturias

B.2 Bentonite/Bentonitic Clay
– Exploited in Bgy. La Mesa, Balamban and used in oil refining and
drilling. Result from chemical alteration of volcanic tuff

B.3 Silica
– Silica sand deposit in Bgys. Manguto, Bonbon and Duangan,
Pinamungajan. Used as additive in the manufacture of portland cement,
glass, cleanser and abrasives

B.4 Feldspar
– Used as constituent of glass, fired clay products and enamels – Bgy.
Mulao, Compostela and Bulcao, Cebu City
Mineral Resources of Cebu…..

II. Non-Metallic Mineral Deposits
– C. Structural & Building Materials

C.1 Marble
– Recrystallized calcareous rock, Naga, Toledo, Tuburan and Alegria.
Source –Uling Limestone & Cebu Orbitoid Limestone

C.2 Dimension Stone
– Quarried as blocks or large pieces. Pink limestone at Bgy. Uling,
Naga (Teresa Marble) and Mactan Stone

C.3 Sand & Gravel/Rock Aggregates
– Sand and gravel activities in Sapangdaku River in Toledo City,
Balamban River, Danao River and other major rivers outside
watershed reservations
– Mountain quarrying of rock aggregates in Naga, identified sources
in Balamban and Compostela-Liloan area

C.4 Stonecraft
– Mini-dimensions stones or thin tile/slabs. Raw materials from
Carcar and Barili Limestone Formations in Tabogon, Catmon,
Carmen, Dalaguete, Alcoy, Naga, Dumanjug, Alegria, Minglanilla
Mineral Resources of Cebu…..

II. Non-Metallic Mineral Deposits
– Fertilizer Mineral

Guano/Rock Phosphate
– Found extensively along caves and limestone deposits throughout
the island. Used mainly as fertilizer and feeds. Found in Toledo
City, Pinamungajan, Tuburan, Sogod, Tabogon, Carcar, Dumanjug,
Barili, Ronda, Dalaguete, Argao and Danao

Dolomite
– Occur as facies within the Pleistoxene Carcar Limestone. Largest
deposit and active mine of PMSC in Alcoy.
– Other deposits in Pardo, Talisay, Naga, Danao, Carmen, Catmon,
Asturias, Sogod, Compostela, Tabuelan, Aloguinsan, Dumanjug,
Sibonga, Badian, Oslob, Boljoon, Ronda and Dalaguete
– Used as animal feed, fertilizer, glass making, refractories, tile
making, paper and as building material
Mineral Resources of Bohol

I. Metallic Mineral Deposits
– A. Precious Metals

A.1 Gold/Silver
– Small scale mining ventures & gold panning activities in Tuba-tuba, Kauswagan,
Bonakan, Sto Nino, Cangmundo, San Vicente & Cantabugnay. Prospects in
Buenavista and Jetafe
– B. Iron and Ferro-Alloys

B.1 Manganese
– Associated with limestone & weathered volcanic rocks. Commercially mines in
Anda Peninsula in Guindulman & Anda. Several spotty deposits in Candijay, Duero,
Jagna and Buenavista. Used as ferro-alloy metals in steel making, dry batteries,
glass industry, paints, pigments, dyes and fertilizers

B.2 Chromite
– Prospect in Bgy. Bangwalog inside the Duero Watershed. Occur as veins or pods.
Use as chrome alloy, refractory

B.3 Nickel
– Prospects in Nagasnas Hill, Alicia and Boctol, Jagna in the Boctol Serpentinite. Use
in the manufacture of nickel steels & cast irons.
– C. Non-ferrous Metals

C.1 Copper
– Porphyry type & closely related to Talibon Diorite& Ubay Volcanics. Prospects in
Baas-Bagacay, Campacot, Buli, Bonakan
Mineral Resources of Bohol…..

II. Non-Metallic Mineral Deposits
– A. Fertilizer Mineral

A.1 Guano/Rock Phosphate
– Found extensively along caves and limestone deposits
throughout the island. Used mainly as fertilizer and feeds.
Found in Baclayon, Loboc, Sevilla, Lila, Valencia, Mabini,
Guindulman, Ubay, Bilar, Batuan, Carmen, Sierra Bullones,
Sikatuna, Corella, Maribojoc, Antequera, Sagbayan, Clarin,
Buenavista, San Isidro, Inabanga, Calape, Candijay, Tubigon,
Loon, Pilar & Balilihan,
Mineral Resources of Bohol…..

II. Non-Metallic Mineral Deposits
– B. Industrial & Manufacturing Minerals

B.1 Limestone
– Active limestone mine of PMSC in Garcia-Hernandez, used in the
metallurgical industry as fluxstone in furnaces, slag. It is also a good
source for agricultural lime to neutralize acidity of soils

B.2 Clay
– Red-burning clay in Jagna, Valencia, Alburquerque, Calape, Tubigon &
Talibon
– Siliceous clay in Catigbi-an, Buenavista
– White clay in Bagacay, Talibon, weathering of quartz diorite

B.3 Silica sand
– Deposits in northern Bohol in Ubay, Talibon, Bien Unido, Jetafe &
Buenavista. SW Bohol in Alburquerque & Loay. Additive in cement
production, glass & abrasives

B.4 Aggregates
– Source identified in volcanic rocks of northern Bohol
Mineral Resources of Negros Oriental

I. Metallic Mineral Deposits
– A. Precious Metals

A.1 Gold/Silver
– Prospects in hydrothermal alterations in Ayungon, Amlan & Siaton
– B. Iron and Ferro-Alloy Metals

B.1 Magnetite Beach Sand
– Reported deposits in Sta. Catalina, 1.0 to 31% magnetic fractions
– C. Non-ferrous Metals

C.1 Copper
– Abandoned copper mine of CDCP in Bgy. Maglinao, Basay, 0.14 to .56%
Cu. Prospects in Bgys Magting & tayawan, Bayawan and Bindoy
Mineral Resources of Negros Oriental….

II. Non-Metallic Mineral Deposits
– A. Ceramic Material

A.1 Clay
– Red burning clay suitable in making potteries, bricks and roofing tiles.
Occur in deltaic floodplains and backswamp areas – Sibulan,
Zamboangita & Manjuyod
– B. Structural & Building Materials

B.1 Sand & Gravel
– Active extraction along the rivers of Amlan, Ayungon, Bacong, Basay,
Dumaguete, La Libertad, Mabinay, Pamplona, San Jose, Sibulan, Siaton,
Bayawan and Sta. Catalina

B.2 Gypsum
– Occur as veins in Bgy. Dalaopan, Tayasan. Use as retarder in cement
production, plaster of Paris

B.3 Limestone
– Potential source for cement raw materials in Guihulngan, La libertad,
Bais and Basay.
Mineral Resources of Negros Oriental….

II. Non-Metallic Mineral Deposits
– C. Industrial & Manufacturing Materials

C.1 Silica
– Active mines in Bgy. Maaslom, Ayungon. Result from hydrothermal
alteration

C.2 Tuff
– Reported volcanic tuff deposits in Bgys Sab-ahan and Lonoy, Bais City
– D. Chemical Minerals

D.1 Phosphate Rock/Guano
– Deposits in Bgy. Binakayan, Guihulngan, Bgy. Tabod, Mabinay and
Villahermosa.

D.2 Sulfur
– Abandoned BCI Mines in Bgy. Abante & Jones, Pamplona
Mineral Resources of Siquijor

Metallic Mineral Deposit
– Manganese


Maria, Larena, Enrique Villanueva. Occur as beds, stringers,
scattered pebbles and boulders. Used as an alloy with iron in the
manufacture of special kind of steel
Non-Metallic Mineral Deposit
– Fertilizer Mineral

Guano and Rock Phosphate
– Bgy. Pisong, Maria, Bgy. Capalasanan, Lazi
– Limestone

Active mine of Lazi Bay in Lazi
– Sand and Gravel

Offshore sand near the coastline of Siquijor and San Juan