Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005 Geothermal Potential of the Cordillera Region, Philippines Michael S. Pastor, Rogelio A. del Rosario, Jr. and Ramon F. Papasin Geothermal and Coal Resources Development Division, Energy Resource Development Bureau, Department of Energy, Energy Center, Merritt Road, Fort Bonifacio, Taguig, M. M., Philippines [email protected], [email protected], [email protected] Keywords: Cordillera, resource potential landlocked as shown in Figure 1. It is bounded in the North by the Provinces of Ilocos Norte and Cagayan; the South by ABSTRACT the Provinces of Nueva Vizacaya and Ecija; the East by the Provinces of Isabela and Cagayan; and the West by the Geothermal remains one of the most promising potential of Provinces of Pangasinan, La Union and Ilocos Sur. energy source in the Philippines as it ranks second to the United States of America in installed geothermal electric 120 122 capacity. Its favorable tectonic setting being situated in the N BABUYAN CHANNEL Pacific “ring of fire” has endowed her with a large number ILOCOS NORTE of geothermal areas widely distributed throughout the PROVINCIAL CAPITAL country. Laoag Kabugao APAYAO CAGAYAN 18 The Cordillera Administrative Region (CAR) in Northern Luzon is considered as one of the potential areas for future Tuguegarao Vigan Bangued geothermal development. It has vast resources of ABRA Tabuk indigenous energy that includes geothermal energy, which KALINGA can be tapped for power and/or non-power applications. Ilagan Bontoc Based on the Philippine Energy Plan for 2004-2013, the ILOCOS MT. PROVINCE Region possesses the highest estimated geothermal resource SUR ISABELA potential in the island of Luzon. Identified geothermal Lagawe San IFUGAO areas with potential for development in CAR include Fernando LA BENGUET Cabarroguis Daklan and Buguias in Benguet, Batong Buhay in Kalinga, UNION Bayombong Baguio City Tinoc in Ifugao, and Mainit in Mountain Province. These Lingayen NUEVA QUIRINO areas belong to the Luzon Central Cordillera Volcanic Belt Gulf VIZCAYA consisting of non-active volcanoes hosting several 16 Lingayen AURORA geothermal resources. Except for Daklan, exploration of PANGASINAN these areas has not been completed in detail. Further Baler BALER exploration of these prospect areas is recommended to NUEVA ECIJA BAY Z Tarlac A Cabanatuan define precisely their resource potential. M TARLAC B A Iba L E S 1. INTRODUCTION PAMPANGA Q Polillo Is. BULACAN U San Fernando E Geothermal remains to be the most promising potential of Z Malolos O energy source, as the Philippines ranks second as a user of N BATAAN MANILA geothermal energy for power generation, surpassed only by Balanga MANILA RIZAL BAY the United States. Presently, the total geothermal power LAMON BAY generating capacity is 1931 MWe accounting for 15% of 50 10 30 20 10 0 50 100 LOCATION MAP the total installed generating capacity nationwide. KILOMETERS The Cordillera Region is considered as one of the potential areas for future geothermal development. Identified Figure 1: Location Map of Cordillera geothermal areas in CAR include Daklan and Buguias in Benguet, Batong-Buhay in Kalinga, and Mainit in 1.2 Climate and Vegetation Mountain Province. Based on the PEP for 2004-2013, a Most of the moderately elevated to low areas are maximum total of 590 MWe geothermal energy potential moderately vegetated. The high-elevated areas are covered estimates are available in the Region. by thick vegetation. The region’s climate generally falls under Type III and IV, which are characterized by a This paper summarizes the geothermal potential of the pronounced dry and wet season. Relatively dry season Region based on previous and recent studies made by the occurs from November to April while the remaining months Philippine Department of Energy (PDOE) and other private are wet with the heaviest downpour observed during the companies. The purpose of which is to assess what works months of August and September. still need to be done in the area and also serve as an investment package for interested potential investors. 1.3Topography and Drainage 1.1 Location and Boundaries Dubbed as the "Watershed Cradle of the Philippines", the Cordillera has a mountainous topography characterized by The Cordillera Administrative Region is prinicipally towering peaks, plateaus and intermittent patches of composed of the provinces of Abra, Benguet, Ifugao, valleys. The complexity of the overall topography of the Mountain Province, Kalinga and Apayao. The Region is area resulted from a combination of intermittent uplifts and 1 Pastor et al. erosion which started during the Miocene and continued to volcanic flows with locally intercalated chert, marble and Pliocene and Quaternary times clastic sedimentary rocks. Bordering these rocks are folded Neogene volcaniclastics and sedimentary rocks. The Region is drained mainly by Abra River in Abra, Agno and Bued Rivers in Benguet and Baguio City, Magat River Masses of Late Miocene diorite-granodiorite plutons, in Ifugao and Apayao, Chico and Pamplona Rivers in elongated along the north-south direction, dominate the Kalinga-Apayao and the Chico and Abra Rivers in Mt. core of the Cordillera as shown in Figure 2. These plutons Province. The down cutting and dissecting action of these discordantly intruded the above rock sequences and are rivers and their tributaries contributed to the generally steep responsible for some ore mineralization in the region. The topographic relief of the area. The result is a vigorous and known geothermal areas in the region associated with rugged terrain where deeply incised valleys, steep river Quaternary volcanism are Batong-Buhay in Kalinga, Mainit gradients and steep slopes. in Bontoc, and Daklan, Buguias, Itogon in Benguet. 2. REGIONAL GEOLOGY 3. DISTRIBUTION OF GEOTHERMAL AREAS Luzon Cordillera is a north south trending geanticlinal The Philippine archipelago is a complex assemblage of mountain chain in the northern part of Luzon. This island arcs, which has been accreting between two opposing mountain chain resulted primarily from a Miocene orogenic major tectonic plates – the Eurasian and the Philippine Sea event accentuated physiographically by a much later Plio- Plate. The subduction zones have generated a discontinuous Pleistocene orogeny and tectonism (Pulanco, 1971). The belt of Pliocene to Quaternary volcanoes which extends arcuate island of Luzon lies between the Manila Trench and throughout the length of the Philippines, from Northern the Philippine Trench, a two oppositely dipping subduction Luzon to Southern Mindanao. zones responsible for the orogenic and tectonic development of the Central Cordillera since Miocene time. Many authors, through years of Philippine geothermal energy exploration, development and production agree that The Central Cordillera is cut by the northern branch of the the present geothermal systems are related to volcanism, Philippine Fault which split into four main branches plutonism and tectonism. According to Datuin and (Ringenbach et al, 1990) shown in Figure 2. These are the Troncales (1987), many of the potential geothermal Tebbo Fault, the Tuba Fault, the Pugo Fault, and the Dalton resource areas in the Philippines are related to young Fault. volcanoes; along Philippine Shear System or its nearby branch faults and some are localized along the fringes of large intra-Miocene silicic batholiths. N t l Geothermal areas in CAR which include Acupan, Daklan, u a A F E o and Buguias in Benguet, Batong Buhay in Kalinga, Tinoc S a g LAOAG g N in Ifugao, and Mainit in Mountain Province belong to the A o - r n SOLSONA t a h A g Luzon Central Cordillera Volcanic Belt. This belt consists i C N I V o r H d i of heavy concentrations of active and non-active volcanoes. C l l e r a Most of the potential geothermal prospects in CAR are F a u H l T t related to the Plio-Quaternary volcanic centers of andesite t U l O u a S to dacite composition which are related and connected to F VIGAN r e v the North Cordillera Quartz Diorite Complex straddling the i R a r central region of Northern Luzon. b A n i s 4. DESCRIPTION OF PROSPECT AREAS a B BUTAC Hot springs abound in the Cordillera Region. Several of S a these thermal areas possess the potential for geothermal n n t J l a u a u y development. Location of the different thermal areas in the n a a F F a u o ag Region is shown in Figure 3. lt a C C p a o a H s P t a u l g T o BAGUIO 4.1 Abra h F t r CITY l u a u s u a t l t F Several thermal areas were identified in the province. They T u n T Intrusives b o e Lingayen a t l are located in the Municipalities of Pilar, Danglas, Boliney, F b Gulf b a Da o Recent Basin Deposits u lt Sal-lapadan, Bucloc and Tubo. Thermal manifestation F a u Strike-Slip Faults C lt consists essentially of warm to hot springs occurring along e n t ra Thrust Faults - visible l fractures. The springs have discharge temperatures ranging on seismic profiles o Va ll from 38 - 67 C and of neutral pH. The more impressive of ey 20 km Ba which is in Boliney, Sal-lapadan and Tubo with measured sin Philippine Fault o temperatures of >50 C. The rest are warm seepages with measured temperatures of <50 oC. From 1994 up to 1999, the Department of Energy (DOE) conducted preliminary Figure2:Regional Geology (Adapted from Ringenbach, survey of the thermal manifestations in the province 1990) consisting of water sampling and reconnaissance geological The oldest rocks in the region are the undifferentiated mapping. metamorphic rocks which are considered part of the Pre- Jurassic Philippine Basement Complex. Overlying this are The geology and chemistry of thermal waters in Boliney, the more widespread, undifferentiated, partly Sal-lapadan, Bucloc and Tubo prospect areas indicate a low metamorphosed Cretaceous to Paleogene, ophiolitic temperature system associated with plutonic areas where residual heat remains in the intrusive bodies.