Introduction
The Philippines is a significant contributor to global resources. Such resources include Cu, Cr, Ni, Fe, Mn and Au deposits, as well as other resources like coal, bauxite, and oil. In 2010, the Philippines produced 11 % of the global Ni supply. Additionally, the Philippines has the fourth largest copper reserves globally. The distribution of currently exploited mineral deposits in the Philippines is given in Figure 1. This impressive endowment of natural resources can be in part attributed to the tectonic regime of the region. What follows is an overview of the major natural resources of the Philippines and how they likely formed, as well as what clues such deposits may offer to the nature of tectonics in the region.
The Philippines is a significant contributor to global resources. Such resources include Cu, Cr, Ni, Fe, Mn and Au deposits, as well as other resources like coal, bauxite, and oil. In 2010, the Philippines produced 11 % of the global Ni supply. Additionally, the Philippines has the fourth largest copper reserves globally. The distribution of currently exploited mineral deposits in the Philippines is given in Figure 1. This impressive endowment of natural resources can be in part attributed to the tectonic regime of the region. What follows is an overview of the major natural resources of the Philippines and how they likely formed, as well as what clues such deposits may offer to the nature of tectonics in the region.
1. Porphyry & Epithermal Deposits: Cu-Au Mineralisation
Porphyry deposits are typically restricted to convergent tectonic regimes (Sillitoe, 2010) and so it comes as no surprise that the Philippines is host to many such deposits. How do these deposits form? Why are they associated with convergent boundaries? Porphyry deposits may be found in arcs because they are invariably associated with magmatic intrusions, and thus are useful clues in delineating the tectonic environment of formation (Sillitoe, 2010). The magmatic fluids produced from a crystallizing intrusion, in addition to other fluids (e.g. groundwater, percolating meteoric water) lead to distinct zones of alteration and mineralization around the intrusives (Sillitoe, 2010). Alteration suites, such as those shown in Figure 2, are identified by characteristic mineralogies and textures. In the Philippines, their presence thus corroborates evidence for the subduction of both the Philippine Sea Plate to the east and, broadly speaking, the Sunda Plate (i.e. the South China Sea) to the west. |
Models for the formation of porphyry deposits in the Philippines are much more complicated than the generalized case. Historically, models invoked arc reversals in the Luzon region (Cooke et al., 2011). More recent models identify two periods of mineralization associated with back-arc potassic intrusions (Cooke et al., 2011). In one case study at the Dinkidi deposit, petrologic and isotopic evidence indicated mineralisations were induced by fractionation and mafic underplating of a dioritic magma that enabled the emplacement of a vein network hosting significant copper and gold grades (Cooke et al., 2011). Yumul et al. (2002) note that Volcanogenic Massive Sulfide (VMS) deposits may also host Au mineralisation in the region, and could be the subject of future exploration.
A unique benefit of the Philippines' dynamic tectonic environment is the ability to study recently formed mineralizations. By collecting geochronological and geochemical data on these kinds of deposits, it may be possible to refine geologic models of their formation, such as the time frame of mineralization processes (Braxton et al., 2012). |
2. Nickel-Chromite-PGE Deposits
Most of the nickel and chromite deposits in the Philippines region are associated with ultramafics, which have arisen as a result of complex magma mixing and subduction-related mantle-melt interactions (Yumul et al., 2002). These deposits may also contain elevated levels of the Platinum Group Elements (PGEs). These ultramafic ophiolite complexes are thus of substantial economic interest. The deposits of interest for mining are the supra-subduction zone ophiolites (as opposed to mid ocean ridge ophiolites), since they have undergone generations of high-degrees of partial melting (Yumul et al., 2002). It is also noted that hydrothermal processes after the emplacement of the ophiolite complexes is partially responsible for the economic viability of these types of deposits (Yumul et al., 2002). The distribution of these types of deposits are shown in Figure 3. This style of mineralization is further characteristic of the regional tectonic regime, since ophiolite emplacement necessitates a convergent regime. |
3. Coal
According to the Philippines Department of Energy, most of the large coal deposits in the region are concentrated on Semirara Island, but there are other deposits throughout the nation. National reserves approximate 446*10^6 metric tons, of 2.37*10^9 metric tons of coal resource potential. Favorable conditions for the formation of coal include inter-arc basins, foreland basins, continental margin basins, and continental rifts (Horkel, 1990). However, coal-bearing basins in arc environments tend to be contaminated by the products pf volcanic eruptions, thus impacting the quality of deposits (Horkel, 1990). The Semirara Island deposit, which accounts for 92% of national production, is an isolated continental margin-type basin on the North Palawan Microcontinental Block (Horkel, 1990). The Panian open-pit coal mine on Semirara Island is featured in the aerial image from NASA at the top of this page.
According to the Philippines Department of Energy, most of the large coal deposits in the region are concentrated on Semirara Island, but there are other deposits throughout the nation. National reserves approximate 446*10^6 metric tons, of 2.37*10^9 metric tons of coal resource potential. Favorable conditions for the formation of coal include inter-arc basins, foreland basins, continental margin basins, and continental rifts (Horkel, 1990). However, coal-bearing basins in arc environments tend to be contaminated by the products pf volcanic eruptions, thus impacting the quality of deposits (Horkel, 1990). The Semirara Island deposit, which accounts for 92% of national production, is an isolated continental margin-type basin on the North Palawan Microcontinental Block (Horkel, 1990). The Panian open-pit coal mine on Semirara Island is featured in the aerial image from NASA at the top of this page.
4. Oil in the Philippines Region
According to the Central Intelligence Agency of the USA, the Philippines exported over 13,000 barrels per day in 2013. This number is dwarfed by the production of other nations, such as Canada, which exported over 3.2 million barrels per day in 2015.
According to the Central Intelligence Agency of the USA, the Philippines exported over 13,000 barrels per day in 2013. This number is dwarfed by the production of other nations, such as Canada, which exported over 3.2 million barrels per day in 2015.
5. Bauxite (Alumina) Deposits
Bauxite deposits are laterite soils from which most of the silica has been stripped by weathering, leaving an earthy rock comprised primarily of minerals such as gibbsite and boehmite (Mendoza, 2001). Given that physical and chemical weathering are more effective at tropical latitudes, it is easily understood why the Philippines would host these deposits as a function of the region's current geography, as a result of the tectonic evolution described on the "Tectonic History" page. Bauxite deposits are mined as a source of alumina, for the eventual smelting of aluminum metal (Mendoza, 2001). On Samar Island in the Philippines, the positive mineral prospects for bauxite deposits are estimated at over 149*10^6 MT at an estimated grade of 41.38% alumina (Mendoza, 2001).
Bauxite deposits are laterite soils from which most of the silica has been stripped by weathering, leaving an earthy rock comprised primarily of minerals such as gibbsite and boehmite (Mendoza, 2001). Given that physical and chemical weathering are more effective at tropical latitudes, it is easily understood why the Philippines would host these deposits as a function of the region's current geography, as a result of the tectonic evolution described on the "Tectonic History" page. Bauxite deposits are mined as a source of alumina, for the eventual smelting of aluminum metal (Mendoza, 2001). On Samar Island in the Philippines, the positive mineral prospects for bauxite deposits are estimated at over 149*10^6 MT at an estimated grade of 41.38% alumina (Mendoza, 2001).
References Cited:
Braxton, D.P., Cooke, D.R., Dunlap, J., Norman, M., Reiners, P., Stein, H., Waters, P. (2012). From crucible to graben in 2.3 Ma: A high-resolution geochronological study of porphyry life cycles, Boyongan-Bayugo copper-gold deposits, Philippines. Geology. V. 40. I. 5. Pp. 471 – 474. Doi: 10.1130/G33125.1.
Central Intelligence Agency. The World Factbook: Crude Oil Exports. Accessed at: https://www.cia.gov/library/publications/the-world-factbook/fields/2242.html. Accessed on: April 5, 2017.
Cooke, D.R., Hollings, P., Zhaoshan, C. (2011). Philippine Porphyry and Epithermal Deposits: An Introduction. Economic Geology. V. 106. No. 8. Pp. 1253-1256 DOI: 10.2113/econgeo.106.8.1253.
Divis, A.F. (2013) The Geology and Geochemistry of Philippine Porphyry Copper Deposits. The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands: Part 2. V.27.
GOVPH. Copper. http://industry.gov.ph/industry/copper/. Accessed: March 30th, 2017.
GOVPH Depart of Energy. Coal. https://www.doe.gov.ph/coal-0. Accessed: March 30, 2017.
Mendoza, H.D. (2001). Mineral Resource Assessment (MRA) of Samar Island. Samar Island Biodiversity Study. Accessed at: http://pdf.usaid.gov/pdf_docs/PNACQ235.pdf.
Natural Resource Governance Institute. http://www.resourcegovernance.org/our-work/country/philippines. Accessed: March 30th, 2017.
Philippine Statistics Authority. The Philippine Mineral Resources Accounts. http://nap.psa.gov.ph/peenra/results/mineral/default.asp. Accessed: March 30th, 2017.
Sillitoe, R.H. (2010). Porphyry Copper Systems. Economic Geology. DOI: 10.2113/gsecongeo.105.1.3.
Yumul, G.P., Dimalanta, C.B., Maglambayan, V.B., Tamayo, R.A. (2002). Mineralization Controls in Island Arc Settings: Insights from Philippine Metallic Deposits. Gondwana Research. V.6. No. 4. Pp. 767-776.
Braxton, D.P., Cooke, D.R., Dunlap, J., Norman, M., Reiners, P., Stein, H., Waters, P. (2012). From crucible to graben in 2.3 Ma: A high-resolution geochronological study of porphyry life cycles, Boyongan-Bayugo copper-gold deposits, Philippines. Geology. V. 40. I. 5. Pp. 471 – 474. Doi: 10.1130/G33125.1.
Central Intelligence Agency. The World Factbook: Crude Oil Exports. Accessed at: https://www.cia.gov/library/publications/the-world-factbook/fields/2242.html. Accessed on: April 5, 2017.
Cooke, D.R., Hollings, P., Zhaoshan, C. (2011). Philippine Porphyry and Epithermal Deposits: An Introduction. Economic Geology. V. 106. No. 8. Pp. 1253-1256 DOI: 10.2113/econgeo.106.8.1253.
Divis, A.F. (2013) The Geology and Geochemistry of Philippine Porphyry Copper Deposits. The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands: Part 2. V.27.
GOVPH. Copper. http://industry.gov.ph/industry/copper/. Accessed: March 30th, 2017.
GOVPH Depart of Energy. Coal. https://www.doe.gov.ph/coal-0. Accessed: March 30, 2017.
Mendoza, H.D. (2001). Mineral Resource Assessment (MRA) of Samar Island. Samar Island Biodiversity Study. Accessed at: http://pdf.usaid.gov/pdf_docs/PNACQ235.pdf.
Natural Resource Governance Institute. http://www.resourcegovernance.org/our-work/country/philippines. Accessed: March 30th, 2017.
Philippine Statistics Authority. The Philippine Mineral Resources Accounts. http://nap.psa.gov.ph/peenra/results/mineral/default.asp. Accessed: March 30th, 2017.
Sillitoe, R.H. (2010). Porphyry Copper Systems. Economic Geology. DOI: 10.2113/gsecongeo.105.1.3.
Yumul, G.P., Dimalanta, C.B., Maglambayan, V.B., Tamayo, R.A. (2002). Mineralization Controls in Island Arc Settings: Insights from Philippine Metallic Deposits. Gondwana Research. V.6. No. 4. Pp. 767-776.