Ore Deposits of PH Flashcards
What geologic period marks the ore deposition in the Philippines?
From the Mesozoic to the Tertiary period.
What is the “Mobile Belt” in the context of the Philippines’ geologic history?
The main axial part of the archipelago that transitioned from a geosynclinal to a platform stage.
What are the main types of ore deposits in the Philippines?
Chromite
Massive pyritic
Pyrometasomatic
Porphyry copper
Gold-bearing vein
What are the two largest chromite deposits in the Philippines?
Masinloc and Acoje.
What distinguishes Masinloc chromite from Acoje chromite?
The high alumina content in Masinloc chromite suggests it is an earlier crystallate than Acoje.
What type of geological complex hosts the Masinloc and Acoje deposits?
The Masinloc and Acoje deposits are hosted within the Zambales Ophiolite Complex, located in western Luzon, Philippines.
This geological complex represents a fragment of oceanic lithosphere that was obducted onto the Philippine island arc system. The deposits are associated with ultramafic rocks, primarily dunite, harzburgite, and serpentinized peridotite, which are characteristic of ophiolite sequences.
Where are massive pyritic deposits like Bagacay, Barlo, and Hixbar found?
: In basement rocks beneath volcanic piles, within the volcanic pile, or at interfaces with sedimentary rocks.
What is the largest pyrometasomatic deposit in the Philippines, and what exotic metals does it contain?
The Larap deposit, containing uranium and cobalt.
How many porphyry copper deposits are known in the Philippines, and how many are mined?
As of 2013, the Philippines had at least 60 known porphyry copper deposits. At that time, only three of these deposits were actively being mined. Notable examples of porphyry copper-gold deposits in the Philippines include Didipio, Tampakan, Boyongan, Bayugo, King King, and Taysan.
These range in size from 20-200 million tons. 0.5% t0 0.8% Cu
What rocks are porphyry copper deposits in the Philippines associated with?
Porphyritic dacite and andesite facies of diorite complexes near the geographic and orogenic axis of the archipelago.
What are the main copper minerals in the Philippine porphyry copper deposits?
Chalcopyrite, with some deposits also containing magnetite, pyrite, molybdenite, gold, and silver.
What is unique about the Lepanto gold deposit?
It is an enargite-luzonite-telluride deposit localized at the intersection of an unconformity and a fault zone.
What type of gold deposits are found in the Baguio district?
Quartz-telluride-gold vein deposits.
Where are gold deposits in the Philippines often spatially related?
To centers of explosive volcanic activity.
What is the probable age of the “Basement Complex” and the geological event recorded.
Paleozoic Age. Mafic lava effusion and some gabbroic intrusion, followed by followed by accumulation of shales and graywackes with some carbonate rocks
What can be found on the outcrops of the Basement Complex
The Basement Complex is repre-
sented by widely distributed outcrops of gneiss, amphibolite, chlorite-epidote-mica schist, and meta- igneous rocks.
When was the geological map of the Philippines published?
1963
What are the Mobile Belt and Stable Region in Philippine geology?
Mobile Belt: Seismically active, characterized by Mesozoic and Tertiary igneous rocks, greater deformation, and volcanic debris-rich sediments.
Stable Region: Seismically inactive, minimal Tertiary igneous rocks, quartz-rich sedimentary rocks with simpler deformation.
What characterizes the Basement Complex of the Philippines?
Probable Paleozoic rocks, including mafic lava flows, gabbroic intrusions, shales, graywackes, and carbonate rocks.
What are the three geosynclinal basins of the Philippines?
Northern Basin: Mindoro, Marinduque, and northern Luzon.
Southern Basin: Southern Philippines (excluding Palawan).
Western Basin: Palawan, possibly extending to Borneo.
West Luzon Basin, the Sulu Sea arc-basin system, and the Luzon Central Valley.
Geosynclines are large accumulations of sedimentary rocks and sediments in continental margins or basins.
What is the thickness of the spilite-graywacke sequence?
Up to 5,000 meters.
What major geological feature is located in Zambales Province?
The Zambales Ultramafic Complex, the largest ultramafic complex, approximately 150 km long.
What volcanic activities occurred during late Miocene to Pliocene?
Intermittent andesitic eruptions followed by very explosive activity.
What were the two main periods of dioritic intrusion and orogeny in the Philippines?
Oligocene: First period of intrusion.
Middle Miocene: More extensive intrusions.
What is the relationship between diorite and andesite in Philippine geology?
They are closely associated and likely derived from the same magmas, often forming mutually intrusive dioritic complexes
What are the major structural features of the Philippines that contributes to the distributions of the ore deposits.
Philippine Deep Trench: Located east of Samar and Mindanao.
Philippine Fault: Extends from southeastern Mindanao to northern Luzon, branching into several segments.
During which geological period were most major epigenetic ore deposits formed?f
From Cretaceous to Pliocene.
What is the significance of diorite in Philippine ore deposits?
Many ore deposits are associated with dioritic rocks, although diorite alone does not guarantee ore presence.
What rocks host the Acoje chromite deposit and how does the associated rock differ from gabbros in refractory chromite ores?
Dunite and clinopyroxenite near a large mass of norite. It is olivine-deficient compared to gabbros
What shapes do the chromite ore bodies in Acoje take?
Tabular bodies and a cylindrical body with a carrot-shaped ore shoot at the center.
What are the average nickel and platinum contents in the sulfide mineralization?
Nickel averages 1%, and platinum averages less than 1 oz per ton.
What is the origin of chromite deposits in Acoje?
Early magmatic origin.
What minerals are associated with nickel and platinum in the Acoje mine?
Pyrrhotite, troilite, pentlandite, and violarite.
What indicates that the Masinloc deposit crystallized earlier than Acoje?
Higher Mg/Fe and Al/Cr ratios and greater olivine abundance compared to pyroxene.
What regional geological structure connects the Acoje and Masinloc deposits?
They are part of the same peridotite layer exposed in opposite limbs of a large synclinal structure.
What is the typical mineralogical composition of massive pyritic deposits?
They range from nearly pure pyrite to mixtures of pyrite, sphalerite, galena, and barite.
What is a distinguishing feature between massive ore and barren wall rock in pyritic deposits?
There are sharp contacts between the two, with evidence of wall rock replacement by ore minerals.
What alteration is commonly observed in the volcanic host rocks of massive pyritic deposits?
Extensive propylitization, with fine-grained silica often accompanying the ore.
What surface indicators are typically associated with massive pyritic deposits?
Prominent gossans, manganese, chert, pyritic carbonaceous shale, gypsum, and barite.
What types of host rocks are massive pyritic deposits commonly found in?
Cretaceous-Paleogene spilite and keratophyre, typically laid down as submarine piles, such as pillow lavas.
Where within volcanic piles are massive pyritic deposits commonly located?
In the uppermost parts of the piles, where they transition stratigraphically into sedimentary rock.
How do pyritic deposits differ from many other ore deposits in the Philippines in terms of geological association?
They are not closely associated with diorite but are instead found in volcanic rock piles.
What structural settings are massive pyritic deposits commonly associated with?
Zones of thrust faulting in uplifted folds.
Zones of thrust faulting in uplifted folds.
A gossan is an oxidized zone with iron oxides and hydroxides, marking the outcrop of sulfide-rich deposits.
Where is the Bagacay mine located?
In the center of Samar Island, operated by Marinduque Mining and Industrial Corporation.
When did the Bagacay mine begin operations
1956.
How much direct-shipping ore was produced from 1962–1966, and at what average copper grade?
57,080 dmt at 10% Cu.
What are the proven reserves of direct-shipping ore (as of June 30, 1967)?
391,200 dmt at 8.46% Cu.
How much milling-grade ore was produced from 1962–1966, and at what average copper grade?
995,732 dmt at 2.9% Cu.
What are the proven reserves of milling-grade ore (as of June 30, 1967)?
2,541,500 dmt at 2.65% Cu.
How much pyrite ore is present, and what is its sulfur content?
7,700,000 dmt at 38% S.
What are the components of the geologic column at the Bagacay mine?
Highly argillized rock (dacite with quartz crystals).
Dark, sub-silicic volcanic rock with jasper lenses.
Bedded tuff and tuff-breccia with copper-bearing coaly beds.
Reef limestone.
What is the largest orebody in the Bagacay mine, and what are its dimensions?
The Guila Guila orebody, ~500 m across, up to 50 m thick.
What are the vertical zones of the ore deposits?
Top: High-grade chalcopyrite-sphalerite-chalcocite ore with barite.
Middle: Milling-grade pyrite-chalcopyrite-sphalerite (?) ore.
Bottom: Pyrite ore.
What evidence suggests copper enrichment in the Bagacay mine?
Secondary copper enrichment in the top parts of orebodies.
The deposit is classified as a **“Kuroko”-type massive sulfide deposit, **characterized by significant concentrations of sulfide minerals. The primary ore minerals include sphalerite, chalcopyrite, and pyrite, with chalcopyrite being a major copper-bearing mineral.
How is copper present in coaly beds, and where is it found?
As chalcopyrite, replacing wood structure, and as chalcocite or black copper oxide, found in lower elevations near the “Main” massive pyritic orebody.
What faults are associated with the Bagacay mine?
A major thrust fault (mapped in 1963) and steeply dipping faults in pits, though no fault control of orebodies was recognized.
What is the copper and zinc content of 8-9% Cu ore (1964 data)?
~6% Zn.
How much high-grade copper ore was reported in 1969, and at what grade?
45,000 tons at 9.00% Cu.
What are pyrometasomatic deposits in the Philippines primarily mined for?
Iron Ore
What types of host rocks are common for pyrometasomatic deposits?
Limestone or other calcareous rocks near volcanic rocks.
What is the age range of the volcanic-sedimentary sequences hosting these philippine ore
deposits?
Cretaceous to Miocene.
Where are the ore deposits located in Larap?
Immediately below a thick sequence of volcanic rocks.
What type of rocks are associated with the Santa Ines deposits?
Calcareous rocks interspersed with andesite porphyry dikes, sills, or flows.
What is the characteristic association of dioritic rocks with pyrometasomatic deposits?
Dioritic rocks occur as sills, dikes, and stocks, often containing hornblende or pyroxene, and sometimes quartz.
What are the common ore minerals found in pyrometasomatic deposits?
Magnetite and, in some cases, hematite.
The mineralization at the Thanksgiving Mine.
Characterized by the presence of galena and hessite, among other minerals. Free gold occurs within pyrite and telluride minerals.
Where is the Hixbar Mine located?
Southeastern end of Luzon, Rapu-Rapu Island.
: What is the host rock in the Hixbar Mine’s geological setting?
The Hixbar Mine, located on Rapu Rapu Island in Albay Province, Philippines, is a gold-rich volcanogenic massive sulfide (VMS) deposit. The mineralization at the Hixbar Mine is hosted within metamorphosed volcanic rocks. Specifically, the ore occurs along the stratigraphic contact between metamorphosed mafic volcanics (chlorite-actinolite schists) and altered dacitic felsic volcanics (quartz-sericite-pyrite schists).
What are the main ore minerals in the Hixbar Mine?
Massive pyrite, chalcopyrite, sphalerite, and supergene chalcocite.
Which other deposits are similar to Hixbar, and what type do they resemble?
Bagacay and Barlo deposits resemble Japanese “Kuroko” deposits with sulfide zoning.
What processes contributed to ore formation at Hixbar Mine?
Submarine environment processes, including precipitation along structures beneath the sea floor and exhalative-sedimentary deposition at the sea floor.
Why is the Larap Mine notable?
It is the largest and oldest iron mine in the Philippines.
What is the host rock of the Larap deposit?
Marl in the upper part of the Lower Miocene Universal Formation.
What type of intrusive rocks are present at Larap Mine?
Syenite dikes and sills, part of the Neogene intrusive suite.
What are the stages of skarn development at Larap Mine?
1) Thermal metamorphism (diopside), 2) Metasomatism (scapolite), 3) Vein formation.
What metals are associated with Larap Mine ore?
Copper, molybdenum, gold, uranium, and cobalt (not recovered).
What processes contributed to ore formation at Larap Mine?
Replacement reactions, cavity filling, repeated fracturing, and heat from intrusions.
Where is the Thanksgiving Mine located?
About 4 km south of Baguio City along Kennon Road, in the Baguio District, northern Luzon, Philippines.
What is the average gold content of the ore in the Thanksgiving Mine?
Approximately 1 oz Au/ton.
What other metals were recovered at the Thanksgiving Mine?
Silver (Ag), Zinc (Zn), Cadmium (Cd), and Copper (Cu).
What are the major rock types found near the Thanksgiving Mine?
primarily hosted in l**imestone that has undergone metamorphism **and hydrothermal alteration to form skarn deposits. This alteration process occurs where volcanic and intrusive rocks interact with the limestone, creating a mineral-rich environment. Surrounding shales and siltstones also contribute to the geological setting, though they are less involved in the ore formation. These rocks are key in hosting valuable minerals such as gold, silver, copper, and zinc.
What is the main host rock for the ore deposits of the thanksgiving mine
Fossiliferous Tertiary limestone at or near its contact with a dike swarm.
What are the two types of ore found at the Thanksgiving Mine?
Skarn Ore: Contains sphalerite, chalcopyrite, pyrite, and skarn minerals like epidote, garnet, and calcite (~10% Zn, ½ oz Au/ton).
Sulfide Ore: Contains sphalerite and galena with gold in petzite and sylvanite (~1 oz Au/ton).
What controls the formation of skarn ore at the Thanksgiving Mine?
Steep limestone-igneous contact.
Fractures along the contact and into the limestone.
Solutional activity along fractures forming breccias.
What is unique about the Thanksgiving Mine compared to other deposits?
Its high gold content reflects its location within a major gold district, while ore solutions carry distinct chemical signatures.
What is a porphyry copper deposit?
A large, low-grade, epigenetic, hypogene copper deposit that can be mined by mass-mining methods.
What is the main source of copper in the Philippines?
Porphyry copper deposits.
How large are porphyry copper deposits in the Philippines?
Ranges from 20–200 million tons with 0.5–0.8% Cu.
Where are porphyry copper deposits typically located in the Philippines?
Near the geographic axis of the archipelago, on or near Tertiary geanticline axes, and adjacent to Tertiary dioritic complexes.
What rocks are associated with porphyry copper deposits?
ntrusive rocks: Dioritic complexes (phaneritic to aphanitic, porphyritic textures).
Adjacent wall rocks: Late Cretaceous to early Tertiary metavolcanic and metasedimentary rocks.
What forms do orebodies in porphyry copper deposits take?
Stockworks: Crude prisms, sometimes tabular.
Dips: Mostly steep, with some nearly flat (e.g., Marcopper, Marinduque).
Branching: Steep deposits may narrow or finger out into zones at depth.
Which alteration minerals are less closely associated with porhpyry cu ore?
Clay, epidote, chlorite, anhydrite, gypsum.
What are the common alteration minerals associated withporphyry cu ore?
Quartz, biotite, sericite.
Name other commercially significant minerals found in porphyry cu deposits.
Magnetite, pyrite, molybdenite, gold, silver.
What is the chief copper mineral in these porphyry copper deposits?
Chalcopyrite (with smaller amounts of bornite, which increases at depth in some deposits).
Where is the Atlas Mine located?
In central Cebu, Philippines, operated by Atlas Consolidated Mining and Development Corporation.
What is the copper grade and total reserves of the Atlas Mine?
217 million tons of 0.7% Cu ore, with recoverable gold, silver, magnetite, and pyrite.
What is the shape and structure of the Lutopan deposit?
A mushroom-shaped intrusive body with a steeply east-dipping “stem” (~200 x 600 m).
What are the major copper minerals in the Atlas Mine?
Chalcopyrite: Dominant everywhere.
Bornite: Found in the footwall diorite.
What alteration types are closely associated with ore mineralization on Atlas Mine
Chloritization
Silicification
Sericitization
Biotitization
What minerals are typical of the surrounding propylitic zone?
Epidote, montmorillonite, pyrophyllite, kaolinite, anhydrite, and gypsum.
What mining method is used at the Lutopan deposit?
Block-caving method with a cutoff grade of 0.5% Cu.
What alteration occurs near the contact of metavolcanics and pluton?
Biotitization, common with ore in these zones.
Where is the remarkable clustering of porphyry copper deposits found in the Mountain Province?
Along the Cordillera Central in northern Luzon, with at least four known deposits: Sto. Tomas II, Kennon, Sto. Niño, and Boneng.
How do the copper deposit sizes in the Mountain Province compare to those in the central Philippines?
They range from less than 20 million to about 50 million tons, whereas deposits in the central Philippines (Atlas, Sipalay, Marcopper) range from 90 to 217 million tons.
What are the main minerals recovered at the Sto. Tomas II mine?
Copper (0.7% Cu), magnetite, gold, and silver through a block-caving operation.
What is the geological setting of the Sto. Tomas II deposit?
The orebody is mostly in metavolcanics, with diorite intrusion forming a stockwork deposit controlled by faults (South, Middle, and North faults).
What alteration is closely associated with the ore in Sto. Tomas II?
Silicification, with biotite and sericite near the ore. Anhydrite and gypsum are abundant below the copper zone, and a pyrite-epidote-magnetite halo surrounds the orebody.
Where is the Sto. Niño deposit located, and which companies operate it?
Located 12 km north-northeast of Baguio, it is operated by Baguio Gold Mining Co. and Philex Mining Corp.
What rock types host the Sto. Niño deposit?
Tertiary felsic hypabyssal porphyries (quartz basalt to soda rhyolite), intruding a Cretaceous-Paleogene metamorphic complex.
What are the main ore minerals in the Sto. Niño deposit?
Chalcopyrite with minor bornite and molybdenite, occurring mainly in late quartz and calcite veins. Gold is also present in trace amounts.
What structural controls influence copper mineralization in Sto. Niño?
The ore is mainly in steep, narrow zones controlled by faults, with higher concentrations near the contact between volcanoclastic rocks and porphyries.
What is the proposed sequence of geologic events leading to mineralization at Sto. Niño?
Gabbroic magma intruded metamorphic rocks, followed by porphyry emplacement, faulting, and subsidence, which allowed mineralizing solutions to rise and deposit ore minerals along fractures.
What role do faults play in porphyry copper mineralization?
Faults create permeable pathways for hydrothermal fluids, allowing minerals like chalcopyrite, bornite, molybdenite, and gold to be deposited along fractures, often forming ‘horsetail’ fracture systems.
How do intrusive bodies contribute to ore deposition?
Magma intrusions along fault zones create fractures that act as channels for mineralizing solutions. The footwall is often the most mineralized due to structural favorability rather than lithology.
How do the fracture patterns differ between Sto. Tomas II and Sto. Niño?
Sto. Tomas II: ‘Horsetail’ fracture system with major faults guiding ore solutions.
Sto. Niño: Complex small thrust faults combined with steep fractures, forming due to a single compressive stress system.
How does fracture orientation indicate deposit depth?
Steeper fractures → Greater depth of formation.
Flatter fractures → Shallower deposits, often modified by erosion and continued faulting.
What exploration methods are effective for porphyry copper deposits?
Geochemical analysis (soil sampling, hydrothermal alteration mapping).
Structural fault analysis (predicting ore-bearing zones).
Identifying repeated faulting & intrusions, which indicate high mineralization potential.
What are the two main gold districts in Luzon, Philippines?
The Baguio District (Mountain Province) and the Paracale-Mambulao District (Camarines Norte).
What is the highest-grade gold mine in the Philippines?
The Thanksgiving Mine (Baguio) and Lepanto Mine (Northern Luzon).
What are the main minerals found in the Lepanto Mine?
Enargite and luzonite (copper), gold-silver tellurides, and tennantite (silver-bearing mineral).
What structural features control ore deposition in the Lepanto Mine?
A steep north-trending fault zone intersecting a south-dipping unconformity.
What rock types host the mineralization at Lepanto?
Dacitic pyroclastics, Cretaceous-Paleogene metavolcanics, and a Miocene trondhjemite pluton.
What are the major gold mines in the Baguio District?
Antamok Mine (north) and Acupan Mine (south).
What are the three main breccia types found in the Balatoc Plug near Acupan?
Old Breccia, Young Breccia (high-grade gold), and GW2 Breccia (quartz-filled fractures).
What mineral is associated with higher gold values in the Baguio District?
Rhodonite (a manganese silicate).
What is the geothermal gradient at the Balatoc Plug region?
1°C per 4.4 meters, with rock temperatures reaching 105°C at depth.
How do gold and copper deposits relate in Northern Luzon?
Gold-rich zones (Baguio) transition into copper-rich deposits (Sto. Tomas & Sto. Niño), showing mineral zoning trends.
What is the general strike direction of the Philippine Fault in the Baguio district?
About N15°W
Geological Map of the Philippines, 1963.
What are the common minerals found in Baguio district ore deposits?
Gold, pyrite, chalcopyrite, sphalerite, and galena in a quartz gangue.
What geological features suggest tectonic movement in the Baguio district?
The presence of mylonite, gouge, and breccia zones.
What are the four factors that control ore shoots in Baguio according to Gardner (1940)?
- Vein intersections
- Pre-mineralization faults intersected by younger faults
- Openings along irregular shear surfaces
- Solution barriers like serpentine
What epoch is the Baguio and Lepanto mineralization placed in?
Mio-Pliocene epoch
Gervasio and Fernandez, 1967.
What type of igneous activity was present before ore deposition in Acupan, Lepanto, and Sto. Niño mines?
Pyroclastic activity.
What are the five types of gold deposits in the Paracale-Mambulao district?
- Garnet-bornite
- Chalcopyrite-gold
- Pyrite-arsenopyrite
- Pyrite-gold
- Sulfide ores in granodiorite
Where is the Paracale-Gumaus mine located?
5 km east-northeast of José Panganiban.
What type of rock contains the most productive sulfide ores in Paracale?
Granodiorite.
What is a common feature linking mineralization in major Philippine ore deposits?
Association with intrusive, faulting, and volcanic activity.
