BETCHAIDA D. PAYOT
University of the Philippines Diliman
Sex: Female
Education: Doctor of Philosophy in Geology, Kanazawa University Japan, 2009
Master of Science in Geology, University of the Philippines, 2006
Bachelor of Science in Geology, University of the Philippines, 2002
Field of Specialization:
Igneous Petrology and Geochemistry
Researches:
Article title: Bouguer Anomaly of Central Cebu, Philippines
Authors: Lt. Armada, Carla B. Dimalanta, Nathaniel Parcutela, Rurik Austria, Jenielyn Padrones, Betchaida Payot, Karlo L. Queaño, Graciano P. Yumul, Jr.
Publication title: Journal of Maps 16(2) 577-584, December 2020
Abstract:
Cebu Island in Central Philippines consists of a Cretaceous basement complex capped by mostly Tertiary sedimentary units. Recent mapping conducted in Central Cebu revealed limited exposures of lithologies, especially those comprising the basement complex. The gravity method was utilized to generate Bouguer anomaly maps for Central Cebu. These geophysical maps provide the first images of the subsurface extent of the basement units. A prominent nearly circular gravity anomaly high is consistently observed in the Bouguer anomaly maps coinciding with the location of dense basement and intrusive rocks. However, field mapping revealed the very limited surface exposure of these units. The gravity highs recognized in the residual anomaly maps may correspond to the larger extent of the intrusive units at depth. The broad gravity high observed in the regional anomaly map may define the extent of the subsurface distribution of the Cretaceous basement complex.
Full text link: https://tinyurl.com/y9grn454
Article title: Consumed tectonic plates in Southeast Asia: Markers from the Mesozoic to early Cenozoic stratigraphic units in the northern and central Philippines
Authors: Karlo L Queaño, Graciano P Yumul Jr, Edanjarlo J Marquez, Jillian A Gabo-Ratio, Betchaida D Payot, Carla B Dimalanta
Publication title: Journal of Asian Earth Sciences: X, September 2020
Abstract:
Tectonic reconstruction models of Southeast Asia all invoke in the early Cenozoic the collision of Mesozoic oceanic plates, which have been fragmented, consumed along subduction zones or emplaced onto the overriding plate. However, with marked variations in these models, we reinvestigate the tectonic evolutionary landscape of Southeast Asia through the lens of Philippine geology. In particular, we present revisions to the more recent models by adopting the unique approach of integrating data that we have gathered for the past 17 years from the Upper Mesozoic to Lower Cenozoic stratigraphic formations in northern and central Philippines. These formations, which resulted mainly from submarine mass transport processes, evolved in response to early arc-related processes of oblique subduction, frontal wedge deformation, terrane accretion and strike slip faulting. Additional key constraints for the revisions include: (1) the timing of early Cenozoic magmatism in eastern Luzon; (2) the spatial distribution of the Upper Mesozoic to Lower Cenozoic sedimentary formations with respect to other key features (e.g. distribution of Mesozoic ophiolite fragment and continent-derived rocks) in the Philippine arc; (3) the paleolatitudinal position of Luzon and surrounding regions and; (4) the movement of the surrounding plates since the Late Mesozoic. In revising previous models, a subduction zone (proto-East Luzon Trough) separating Benham Plateau and the Philippine arc was placed to explain the spatial distribution of Eocene arc-related formational units and Mesozoic ophiolite materials comprising the accretionary complex east of Luzon at ~40 Ma period. During this time, Luzon was modeled at the southern margin of the East Asia Sea or the proto-Philippine Sea Plate. Mesozoic ophiolitic complexes that line the eastern Philippine arc as well as the ophiolitic and pelagic limestone and chert fragments included in the arc-derived, Eocene formations in Luzon could very well be traces of the now consumed East Asia Sea-proto-Philippine Sea Plate. Within the same period, we modified the Palawan Microcontinental Block (PCB), positioned at the trailing edge of the proto-South China Sea to include the whole Mindoro island and the Romblon Island Group in Central Philippines. Pieces of the consumed Izanagi Plate, the proto-South China Sea and continental-derived sediments from Asia mainland are reflected in the Mesozoic metamorphic rocks and the Eocene sedimentary formation in western Mindoro. Finally, we model Cebu, Bohol and Negros islands in Central Philippines as being at the leading oceanic edge of the Indo-Australian Plate during the early Cenozoic. With the northward movement of the Indo-Australian plate and the trench roll back of the southern margins of the Philippine Sea Plate, the accretion of the Cretaceous arc-related rocks of Cebu, Bohol and Negros onto the Philippine arc by the end of Eocene or early Oligocene becomes a possibility.
Full text link: https://tinyurl.com/y9qscp5f
Article title: Mesozoic rock suites along western Philippines: Exposed proto-South China Sea fragments?
Authors: Graciano P Yumul Jr, Carla B Dimalanta, Jillian A Gabo-Ratio, Karlo L Queaño, Leo T Armada, Jenielyn T Padrones, Decibel V Faustino-Eslava, Betchaida D Payot, Edanjarlo J Marquez
Publication Title: Journal of Asian Earth Sciences: X, May 2020
Abstract:
An ancient oceanic crustal leading edge east of mainland Asia, the proto-South China Sea crust, must have existed during the Mesozoic based on tectonic reconstructions that accounted for the presence of subducted slabs in the lower mantle and the exposed oceanic lithospheric fragments strewn in the Philippine and Bornean regions. Along the western seaboard of the Philippine archipelago, numerous Mesozoic ophiolites and associated lithologies do not appear to be genetically associated with the younger Paleogene-Neogene ocean basins that currently surround the islands. New sedimentological, paleomagnetic, paleontological, and isotopic age data that we generated are presented here, in combination with our previous results and those of others, to reassess the geological make-up of the western Philippine island arc system. We believe that the oceanic lithospheric fragments, associated melanges, and sedimentary rocks in this region are exhumed slivers of the proto-South China Sea ocean plate.
Full text link: https://tinyurl.com/y92rnhgq
Article title: Melt-rock interaction in the subarc mantle: records from the plagioclase peridotites of the southern Palawan Ophiolite, Philippines
Authors: Florence Annette Labis, Betchaida D. Payot, Gabriel Theopilus Vinalay Valera, Julius Pasco, Jesley Mei A. Dycoco, Akihiro Tamura, Tomoaki Morishita, Shoji Arai
Publication title: International Geology Review, April 2020
Abstract:
The interaction between migrating melts and the upper mantle largely affects the composition of the ascending melt and residual peridotites. In island arcs, melt-rock interactions and products which involved highly depleted mantle peridotites are still largely undocumented despite their petrological importance. In this contribution, the petrographic and geochemical signatures of refractory and refertilized peridotites comprising the mantle section of the southern Palawan Ophiolite, Philippines are investigated. The peridotites are dominantly comprised of residual spinel harzburgites with minor dunite and plagioclase peridotites. Spinel harzburgites are similar to other highly depleted residual mantle materials of other suprasubduction zone ophiolites. Plagioclase peridotites, which are cut by gabbroic intrusions, preserve distinct petrological characteristics indicating melt-rock interaction. The melts preserved as gabbroic dikes have signatures transitional between mid-ocean ridge and island arc, and are comparable to back-arc basin lavas. We therefore propose that the plagioclase peridotites were formed due to the reaction between highly depleted mantle peridotites beneath an intraoceanic arc and migrating BABB-like magmas possibly during the incipient stages of back-arc rifting.
Article title: Petrogenesis of ultramafic-mafic clasts in the Dos Hermanos Mélange, Ilocos Norte: Insights to the evolution of western Luzon, Philippines
Authors: Julius Pasco, Jesley Mei A. Dycoco, Gabriel Theopilus Vinalay Valera, Betchaida D. Payot, John Dave B. Pillejera, Frances Aleksis Anika E. Uy, Lt. Armada, Carla B. Dimalanta
Publication title: Journal of Asian Earth Sciences 184, August 2019
Abstract:
The clasts of ophiolitic mélanges formed in orogenic margins reflect the tectonomagmatic history of a region and record the petrological signatures of oceanic lithospheres that interacted in the past. Exposed at the northwestern edge of Luzon, Philippines, the highly deformed Dos Hermanos Mélange (DHM) provides new insights on the complex history of western Luzon island. The DHM is a tectonic mélange composed predominantly of ultramafic-mafic clasts set in a sheared serpentinite matrix. The ultramafic clasts are mostly harzburgites with rare occurrences of lherzolite, dunite and chromitite. Petrographic (e.g. protogranular to equigranular texture) and geochemical characteristics (e.g. spinel Cr# = 0.17–0.60, olivine Fo content = 87–91) of the peridotites typify residual mantle peridotites which underwent low to moderately high degrees of partial melting. Mineral chemistry of some dunite and harzburgite samples (e.g. high spinel TiO2 = 0.01–0.64 wt%) further record subsequent modification of the depleted mantle material by arc-related processes (e.g. metasomatism). Most of the mafic clasts classify as gabbros and are composed of highly anorthitic plagioclase (An88–99) and Ti-poor pyroxenes which suggest derivation from arc-related melts. One troctolite clast, however, records the distinct petrographic (e.g. ophitic texture) and geochemical (e.g. low An content of plagioclase = 73–80) signatures of primitive MOR-related magma. These contrasting petrologic signatures in the ultramafic-mafic clasts of the DHM are similar to those observed in the crustal and mantle sections of the Eocene Zambales Ophiolite Complex (ZOC). This suggests that the DHM, like the ZOC, records the complex history of the convergence and emplacement of an ancient oceanic crust onto the Philippine Mobile Belt. Later tectonic processes in the region, which occurred after the emplacement of the ZOC, resulted to the extensive dissection and translation of ophiolitic blocks northwards transforming them into the DHM.
Article title: Petrographic and geochemical characterization of the crustal section of the Pujada Ophiolite, southeastern Mindanao, Philippines: Insights to the tectonic evolution of the northern Molucca Sea Collision Complex
Authors: Valerie Shayne V Olfindo, Betchaida D Payot, Gabriel Theophilus V Valera, Efren G Gadot Jr, Barbie Ross B Villaplaza, Kenichiro Tani, Carla B Dimalanta, Graciano P Yumul Jr.
Publication title: Journal of Asian Earth Sciences 184, October 2019
Abstract:
The Molucca Sea Collision Complex (MSCC) preserves the complex interaction between the Eurasian, Philippine Sea and the completely subducted Molucca Sea Plates. Petrological studies of obducted arc and ophiolitic materials in this region thus provide a unique opportunity to elucidate the tectono-magmatic evolution of the area. In this study, we present new petrographic and geochemical data on the crustal section of the Pujada Ophiolite which is extensively exposed in southeastern Mindanao, Philippines. Our work reveals that this ophiolite is a remnant of an oceanic lithosphere with backarc affinity. U-Pb dating of zircons from the isotropic gabbros further constrains the age of the Pujada Ophiolite to Late Cretaceous (90 Ma). This age is consistent with the inferred age of the proto-Molucca Sea Plate based on tectonic reconstructions and tomography. Exposed to the north of the Pujada Ophiolite and separated by a NE-SW trending thrust fault is the Iba Formation. This unit originally purported to be the carapace of the Pujada Ophiolite records an IA (island arc) affinity. The geochemical signature of the Iba Formation suggests derivation from an enriched mantle source affected by slab-derived components related to the East Mindanao-Halmahera Arc. We therefore interpret the Pujada Ophiolite as a trapped fragment of the proto-Molucca Sea Plate that was thrust onto the Halmahera Arc possibly during the waning stages of the collision between the Sangihe and Halmahera Arcs.
Article title: An evolving subduction-related magmatic system in the Masara Gold District, Eastern Mindanao, Philippines
Authors: Alfred Elmer Buena, Barbie Ross B Villaplaza, Betchaida D Payot, Jillian Aira S Gabo-Ratio, Noelynna T Ramos, Decibel V Faustino-Eslava, Karlo L Queaño, Carla B Dimalanta, Jenielyn T Padrones, Kenichiro Tani, Walter W Brown, Graciano P Yumul Jr
Publication title: Journal of Asian Earth Sciences: X, June 2019
Abstract:
The Masara Gold District in Eastern Mindanao, Philippines, is one of the most prolific gold provinces in the Philippines. Recent district-scale mineral exploration makes it possible to undertake geologic and geochemical studies and thus to yield better insights about the mineralization environment of the Masara Gold District. In the Masara Gold District, mineralization is hosted in andesitic rocks and multiple stocks of diorite intrusions. New U-Pb and whole rock K-Ar age dating of these host rocks reveal Eocene to Plio-Pleistocene ages for the magmatic suites. A new lithologic unit is proposed to accommodate the composite diorite phases associated with mineralization. Major and trace element geochemistry of these host rocks show that the Eocene magmatic suite exhibits a tholeiitic character while the diorite and subvolcanic andesite pulses of the Miocene are calc-alkaline in composition. Adakitic rocks were emplaced during the Late Miocene and Plio-Pleistocene. Mineralization in eastern Mindanao is associated with several intrusive events formed during the Oligocene to the Pliocene. The majority of these mineralization events is associated with calc-alkaline magmatic suites. Based on this study, epithermal gold mineralization in the Masara Gold District is closely related to the Late Miocene magmatic rocks which exhibit calc-alkaline and adakitic signatures.
Full text link: https://tinyurl.com/ybgutyyx
Article title: Characterization of the proto-Philippine Sea Plate: Evidence from the emplaced oceanic lithospheric fragments along eastern Philippines
Authors: Carla B Dimalanta, Decibel V Faustino-Eslava, Jillian Aira S Gabo-Ratio, Edanjarlo J Marquez, Jenielyn T Padrones, Betchaida D Payot, Karlo L Queano, Noelynna T Ramos, Graciano P Yumul Jr
Publication title: Geoscience Frontiers 11(1): 3-21, February 2019
Abstract:
The proto-Philippine Sea Plate (pPSP) has been proposed by several authors to account for the origin of the Mesozoic supra-subduction ophiolites along the Philippine archipelago. In this paper, a comprehensive review of the ophiolites in the eastern portion of the Philippines is undertaken. Available data on the geology, ages and geochemical signatures of the oceanic lithospheric fragments in Luzon (Isabela, Lagonoy in Camarines Norte, and Rapu-Rapu island), Central Philippines (Samar, Tacloban, Malitbog and Southeast Bohol), and eastern Mindanao (Dinagat and Pujada) are presented. Characteristics of the Halmahera Ophiolite to the south of the Philippines are also reviewed for comparison. Nearly all of the crust-mantle sequences preserved along the eastern Philippines share Early to Late Cretaceous ages. The geochemical signatures of mantle and crustal sections reflect both mid-oceanic ridge and supra-subduction signatures. Although paleomagnetic information is currently limited to the Samar Ophiolite, results indicate a near-equatorial Mesozoic supra-subduction zone origin. In general, correlation of the crust-mantle sequences along the eastern edge of the Philippines reveal that they likely are fragments of the Mesozoic pPSP. © 2019 China University of Geosciences (Beijing) and Peking University.
Full text link: https://tinyurl.com/yaoyou7o
Article title: Petrologic nature of the active subarc crust-mantle boundary: Mixed magmatic-metasomatic processes recorded in xenoliths from Sabtang island, Luzon arc
Authors: Gabriel Theophilus V Valera, Betchaida D Payot, Shoji Arai, Miyuki Takeuchi, Satoko Ishimaru, Akihiro Tamura
Publication title: Journal of Volcanology and Geothermal Research 374, pp80-99, April 2019
Abstract:
Some arc magmas reside in the uppermost mantle and the lower crust. Their deep-seated behavior determines the composition of magmas that erupt at the surface. Mafic-ultramafic xenoliths newly found in Sabtang island, Batanes group of islands of the Luzon arc record subarc processes. The xenolith suite is comprised mainly of dunites, orthopyroxenites, clinopyroxenites, hornblendites, and gabbros, all hosted in basaltic to andesitic lavas. Petrographic characteristics suggest the metasomatic formation of orthopyroxenites and hornblendites from dunites and clinopyroxenites, respectively. The apparently primary minerals are homogeneous in composition. Olivine is relatively magnesian (Fo 82–90 ) and chromian spinel is rich in Cr# (=Cr/[Cr + Al], around 0.7) in dunites. Clinopyroxene is relatively magnesian (Mg# = Mg/[Mg + Fe ²⁺ ] = 0.73–0.93) in clinopyroxenites and gabbros, and plagioclase is highly anorthitic (An 89–98 ) in the gabbros. The primary mineral assemblage reflects crystallization of olivine and spinel followed by clinopyroxene all occurring in the uppermost mantle and lower crust of the Luzon arc. The orthopyroxenes and amphiboles were metasomatically produced at the expense of olivine and clinopyroxene, respectively. Clinopyroxene in the xenoliths is in equilibrium with the magmas that formed the Sabtang volcanics. They have relatively elevated contents of large-ion lithophile elements and light-rare-earth elements, which suggest derivation from an enriched mantle. The Sabtang xenoliths evidence the very active modification of the subarc mantle-crust boundary zone by mantle-derived magmas and slab-derived melts/fluids so that the mineral assemblage of the resultant rocks is similar to that of the predominant recent magma.
Article title: Slab rollback and microcontinent subduction in the evolution of the Zambales Ophiolite Complex (Philippines): A review
Authors: Graciano P Yumul Jr, Carla B Dimalanta, Ricky C Salapare, Karlo L Queano, Decibel V Faustino-Eslava, Edanjarlo J Marquez, Noelynna T Ramos, Betchaida D Payot, Juan Miguel R Guotana, Jillian Aira S Gabo-Ratio, Leo T Armada, Jenielyn T Padrones, Keisuke Ishida, Shigeyuki Suzuki
Publication title: Geoscience Frontiers 11(1):23-26, February 2019
Abstract:
New radiolarian ages show that the island arc-related Acoje block of the Zambales Ophiolite Complex is possibly of Late Jurassic to Early Cretaceous age. Radiometric dating of its plutonic and volcanic-hypabyssal rocks yielded middle Eocene ages. On the other hand, the paleontological dating of the sedimentary carapace of the transitional mid-ocean ridge – island arc affiliated Coto block of the ophiolite complex, together with isotopic age datings of its dikes and mafic cumulate rocks, also yielded Eocene ages. This offers the possibility that the Zambales Ophiolite Complex could have: (1) evolved from a Mesozoic arc (Acoje block) that split to form a Cenozoic back-arc basin (Coto block), (2) through faulting, structurally juxtaposed a Mesozoic oceanic crust with a younger Cenozoic lithospheric fragment or (3) through the interplay of slab rollback, slab break-off and, at a later time, collision with a microcontinent fragment, caused the formation of an island arc-related ophiolite block (Acoje) that migrated trench-ward resulting into the generation of a back-arc basin (Coto block) with a limited subduction signature. This Meso-Cenozoic ophiolite complex is compared with the other oceanic lithosphere fragments along the western seaboard of the Philippines in the context of their evolution in terms of their recognized environments of generation. © 2019 China University of Geosciences (Beijing) and Peking University
Full text link: https://tinyurl.com/yd3r8ozr
Article title: Mantle Evolution from Ocean to Arc: The Record in Spinel Peridotite Xenoliths in Mt. Pinatubo, Philippines
Authors: Betchaida D Payot, Shoji Arai, Masako Yoshikawa, Akihiro Tamura, Mitsuru Okuno, Danikko John V Rivera
Publication title: Minerals 8(11): pp515 November 2018
Abstract:
A suite of peridotite xenoliths were collected from lahar flow deposits located close to the summit of Mt. Pinatubo. Spinel harzburgite is the most dominant lithology among dunites, pyroxenites and websterites. A rare spinel lherzolite xenolith (P12-7) is also present in this suite. The spinel lherzolite has well-preserved protogranular texture with very minimal presence of secondary amphibole, low Cr# in the chromian spinel, and depleted and hump shaped patterns of chondrite-normalized rare earth element (REE) patterns for the clinopyroxenes. In contrast, the spinel harzburgites contain abundant secondary amphiboles and orthopyroxenes, higher Cr# in the spinel, and slightly elevated patterns for the chondrite-normalized REE patterns for the amphiboles. The spinel lherzolite also exhibits higher olivine Fo content for a given spinel Cr# compared to the spinel harzburgites. The spinel lherzolite is interpreted as a typical residue from partial melting of abyssal peridotites whereas the spinel harzburgites may have formed via partial melting with subsequent modification during the influx of fluids in the mantle wedge. Our results suggest that fragments of MOR-derived lithosphere exist in the mantle wedge beneath the Philippine island arc. This work provides evidence for the conversion of abyssal to arc peridotites in the mantle wedge.
Full text link: https://tinyurl.com/ycsw6hqv
Article title: Aqueous fluids and sedimentary melts as agents for mantle wedge metasomatism, as inferred from peridotite xenoliths at Pinatubo and Iraya volcanoes, Luzon arc, Philippines
Authors: Masako Yoshikawa, Akihiro Tamura, Shoji Arai, Tatsuhiko Kawamoto, Betchaida D Payot, Danikko John Rivera, Ericson B Bariso, Ma Hannah T Mirabueno, Mitsuru Okuno, Tetsuo Kobayashi
Publication title: Lithos 262: 355-368, October 2017
Abstract:
Mantle xenoliths entrained in subduction-zone magmas often record metasomatic signature of the mantle wedge. Such xenoliths occur in magmas from Iraya and Pinatubo volcanoes, located at the volcanic front of the Luzon arc in the Philippines. In this study, we present the major element compositions of the main minerals, trace element abundances in pyroxenes and amphiboles, and Nd–Sr isotopic compositions of amphiboles in the peridotite xenoliths form Pinatubo volcano. These data indicate enrichment in fluid-mobile elements, such as Rb, Ba, U, Pb, and Sr, and Nd-Sr isotopic ratios relative to those of mantle. The results are considered in terms of mixing of asthenospheric mantle and subducting oceanic crustal components. The enrichments observed in the Pinatubo mantle xenoliths are much less pronounced than those reported for the Iraya mantle xenoliths. This disparity suggests differences in the metasomatic agents contributing to the two suites; i.e., aqueous fluids infiltrated the mantle wedge beneath the Pinatubo volcano, whereas aqueous fluids and sediment-derived melts infiltrated the mantle wedge beneath the Iraya volcano.
Article title: Alteration and lithogeochemistry in the Masara Gold District, Eastern Mindanao, Philippines, as tools for exploration targeting
Authors: Barbie Ross B Villaplaza, Alfred Elmer Buena, Nichole Anthony D Pacle, Betchaida D Payot, Jillian Aira S Gabo-Ratio, Noelynna T Ramos, Carla B Dimalanta, Decibel V Faustino-Eslava, Karlo L Queaño, Graciano P Yumul Jr, Kotaro Yonezu
Publication title: Ore Geology Reviews 91: 530-540, September 2017
Abstract:
The intermediate to low sulfidation epithermal gold deposit in Masara, Compostela Valley, Eastern Mindanao, Philippines, is associated with a diorite porphyry from the Late Miocene Lamingag Intrusive Complex. Detailed mineralogical investigation of the host rocks in the deposit reveals five major alteration zones and at least two mineralizing events. A potassic alteration zone characterized by stockwork magnetite veins, secondary biotite and magnetite and an early-stage chlorite-sericite alteration composed of quartz+chlorite+illite+sericite+pyrite±biotite±magnetite±calcite assemblages are interpreted to be linked with an earlier porphyry copper system in the area. These were overprinted by late-stage chlorite-sericite alteration consisting of quartz+chlorite+illite+sericite+pyrite±adularia±magnetite±epidote and sericite assemblages which generally contain quartz+illite+sericite+pyrite. These alteration overprints are inferred to be related to a younger low to intermediate-sulfidation epithermal gold mineralization which involved near-neutral fluids. Advanced argillic alteration comprising quartz+kaolinite+magnetite+dickite±illite±calcite was also observed in the area. Isocon analysis shows that alteration zones associated with epithermal mineralization are generally characterized by enrichment in SiO2 and K2O and depletion of CaO and Na2O as well as additions of Au, Cu, Zn and Pb. Pearce Element Ratio (PER) analysis indicates high degrees of sericitization in the altered diorite porphyry, tuff and quartz diorite units. At least three major alteration centers are defined based on the spatial distribution of the Alteration Index of surface samples calculated from the PER analysis. The results of this study support the use of whole-rock geochemistry as a complement to traditional techniques in exploration geochemistry.
Article title: Petrological and geochemical characteristics of the Samar Ophiolite ultramafic section: implications on the origins of the ophiolites in Samar and Leyte islands, Philippines
Authors: JMR Guotana, BD Payot, CB Dimalanta, NT Ramos, DV Faustino-Eslava, KL Queaño, GP Yumul Jr
Publication title: International Geology Review 60(30):1-17, July 2017
Abstract:
Cretaceous ophiolites and ophiolitic fragments occur in the Samar and Leyte islands in eastern central Philippines. The Samar Ophiolite is a complete crust–mantle sequence exposed in southern Samar, whereas the Tacloban and Malitbog ophiolite complexes are, respectively, located in the northeastern and southwestern portions of the nearby Leyte island. Despite the close proximity of these islands, the genetic relationship of these ophiolites and ophiolitic complexes, if any, remains to be elucidated. We present here new petrographic and geochemical data on the harzburgites and dunites of the ultramafic section of the Samar Ophiolite. These mantle peridotites are highly depleted residues which have low modal pyroxene content, high spinel Cr# (=0.62–0.79), and slightly enriched light rare earth element abundance with depletion in Zr and Ti. Such characteristics are typical of supra-subduction zone peridotites and strongly contrast with the abyssal signatures of the Tacloban and Malitbog ophiolite complexes. The absence of a structure between these adjacent ophiolite fragments initially hints that they form a single oceanic crust. However, with our new results, we suggest other possible mechanisms that could explain the relationship of these ophiolites.
Article title: Petrography and geochemistry of Cenozoic sedimentary sequences of the southern Samar Island, Philippines: Clues to the unroofing history of an ancient subduction zone
Authors: Nichole Anthony D Pacle, Carla B Dimalanta, Noelynna T Ramos, Betchaida D Payot, Decibel V Faustino-Eslava, Karlo L Queaño, Graciano P Yumul Jr
Publication title: Journal of Asian Earth Sciences 142: 3-19, August 2016
Abstract:
The Cenozoic sedimentary sequences of southern Samar Island in eastern Philippines were examined to understand the unroofing history of an ancient arc terrane. Petrographic and geochemical data reveal varying degrees of inputs from the ophiolite basement and differences in modal compositions. The sedimentary units are mostly made up of lithic fragments. The Late Oligocene to Early Miocene Daram Formation contains more chert and volcanic fragments whereas the Late Miocene to Early Pliocene Catbalogan Formation is dominantly composed of ultramafic components. These variances are correspondingly reflected in the geochemical signatures of these two sedimentary formations. The Catbalogan Formation clastic rocks have higher volatile-free MgO and Fe2O3 values (average: 8.4% for both oxides) compared to the Daram Formation samples (average: 5.1 and 6.3%, respectively). Geochemical variations are also reflected in the Co, Cr and Ni values: the Catbalogan Formation samples reflect higher concentrations (Co: 15-57 ppm; Cr: 231-1094 ppm; Ni: 84-484 ppm) compared to the Daram Formation samples (Co: 24-32 ppm; Cr: 234-418 ppm; Ni: 212-323 ppm). These observations suggest that the Daram Formation eroded and transported more of the crustal portions of the ophiolite, while the younger Catbalogan Formation represents a later exhumation and subsequent erosion of the ultramafic section. An oceanic island arc (OIA) setting is proposed for the two formations based on several tectonic discrimination diagrams (e.g. Th-La-Sc, La vs. Th). The OIA signature is further supported by their smooth chondrite-normalized rare earth element (REE) patterns with no obvious Eu anomaly as well as LREE enrichment which are typical of sediments deposited in OIA setting. Based on the dominantly ophiolitic provenance of the Daram and Catbalogan Formations, the post-emplacement history of the nearby Samar Ophiolite is constrained during the Late Oligocene to Early Pliocene period.
Article title: Arc and backarc geochemical signatures of the proto-Philippine Sea Plate: Insights from the petrography and geochemistry of the Samar Ophiolite volcanic section
Authors: Juan Miguel R Guotana, Betchaida D Payot, Carla B Dimalanta, Noelynna T Ramos, Decibel V Faustino-Eslava, Karlo L Queaño, Graciano P Yumul Jr
Publication title: Journal of Asian Earth Sciences 142: 77-92, July 2016
Abstract:
Remnants of a Cretaceous lithosphere are found at the peripheries of the West Philippine Basin. These Mesozoic fragments preserve arc affinity and include the Amami Plateau, the East Halmahera Ophiolite and the ophiolites along the eastern margin of the Philippine archipelago. The eastern margin of the Philippines is composed of Early to Late Cretaceous ophiolites and ophiolitic complexes that exhibit strong subduction imprints. The early Late Cretaceous Samar Ophiolite in the central Philippines forms part of this eastern belt. Recent surveys in southern Samar revealed the presence of peridotites, gabbros, and massive and pillowed flows of the Samar Ophiolite. Major, trace and rare earth element signatures of the volcanic rock samples indicate moderate to strong subduction-related influences and formation in an island arc setting. In contrast to other similarly-aged ophiolites along the eastern margin of the archipelago, those to the north of Samar Island exhibit weak to almost mid-oceanic ridge characteristics. These differences in the geochemical signatures of the ophiolites and ophiolitic complexes along eastern Philippines require a re-evaluation of a previous model suggesting that these ophiolites originated from a single oceanic lithosphere, possibly the proto-Philippine Sea Plate.
Article title: Adakitic rocks in the Masara gold-silver mine, Compostela Valley, Mindanao, Philippines: Different places, varying mechanisms?
Authors: Graciano P Yumul Jr, Walter W Brown, Carla B Dimalanta, Carlito A Ausa, Decibel V Faustino-Eslava, Betchaida D Payot, Noelynna T Ramos, Adrian Nicol L Lizada, Alfred Elmer Buena, Barbie Ross B Villaplaza, Pearlyn C Manalo, Karlo L Queaño, Juan Miguel R Guotana, Nichole Anthony D Pacle
Publication title: Journal of Asian Earth Sciences 142:45-55, June 2016
Abstract:
The presence of adakites has been used as an indicator for the occurrence of gold mineralization in many mineral prospecting works. Traditionally, the unique geodynamic controls to adakite formation, particularly the high temperature gradient and other slab-melting requirements, have been taken as key elements that must be present during their formation. However, several studies have suggested alternative mechanisms. This paper presents fractional crystallization as the most viable mechanism for the generation of adakitic rocks in the Masara gold-silver mine in Eastern Mindanao, Philippines. Furthermore, this paper also argues that the occurrence of adakitic rocks does not necessarily indicate the presence of mineralization. Depending on the scale, their occurrence may be an exploration marker at a regional or district level, but at the mine-level, other more localized parameters will have to be considered.
Article title: Geochemical and Geophysical Characteristics of the Balud Ophiolitic Complex (BOC), Masbate Island, Philippines: Implications for its Generation, Evolution and Emplacement
Authors: Pearlyn C Manalo, Carla B Dimalanta, Decibel V Faustino-Eslava, Betchaida D Payot, Noelynna T Ramos, Karlo L Queaño, Americus DC Perez, Graciano P Yumul Jr
Publication title: Terrestrial, Atmospheric & Oceanic Sciences 26 (6), December 2015
Abstract:
This paper presents the first field, geochemical and geophysical information on the recently recognized Early Cretaceous Balud Ophiolitic Complex (BOC) in the island of Masbate in the Central Philippines. Mapping of the western limb of the island revealed that only the upper crustal section of the BOC is exposed in this area. Geochemically, the pillow basalts are characterized by transitional mid-oceanic ridge basalt-island arc tholeiitic compositions. Gravity surveys yielded low Bouguer anomaly values that are consistent with the highly dismembered nature of the BOC. Short wavelength, high amplitude magnetic anomalies registered across the study area are attributed to shallow magnetic sources. This is taken to support the model that the ophiolitic complex occurs as thin crustal slivers that are not deeply-rooted in the mantle. Comparing BOC with other ophiolites in the Central Philippines, such as those in the islands of Sibuyan, Leyte and Bohol, suggests the possibility of a common or contiguous source for similarly-aged and geochemically composed crust-mantle sequences in the region.
Full text link: https://tinyurl.com/y9mr6qdh
Article title: Paleomagnetism of the Samar Ophiolite: Implications for the Cretaceous sub-equatorial position of the Philippine island arc
Authors: Hertz G Balmater, Pearlyn C Manalo, Decibel V Faustino-Eslava, Karlo L Queaño, Carla B Dimalanta, Juan Miguel R Guotana, Noelynna T Ramos, Betchaida D Payot, Graciano P Yumul Jr
Publication title: Tectonophysics: 664, October 2015
Abstract:
Samar island in the eastern part of Central Philippines is underlain by a complete ophiolite suite, the Samar Ophiolite. We present the first geochronological and paleomagnetic data for the Samar Ophiolite. Whole rock K-Ar dating of two basalt samples yielded an age of 100.2 ± 2.7 Ma and 97.9 ± 2.8 Ma. Thirteen sites in four localities yielded characteristic remanent magnetization with in situ direction of D = 340°, I = - 24°, k = 15, α95 = 11° and tilt-corrected direction of D = 342°, I = - 27°, k = 15, α95 = 11°. These values suggest that the ophiolitic basement rocks of Samar formed in the Late Cretaceous at a paleolatitude of 14°S ± 6°. The paleolatitude is several degrees south of the sub-equatorial positions calculated for the three other Mesozoic ophiolites of the Philippine Mobile Belt (PMB) whose paleomagnetism had been previously studied. The PMB ophiolites in eastern and central Philippines share a common age, geochemistry and paleolatitude with the Halmahera Ophiolite, suggesting that they originated from a Mesozoic supra-subduction zone that spanned a few degrees north of the equator to around 15°S.
Article title: Podiform chromitite formation in a low-Cr/high-Al system: An example from the Southwest Indian Ridge (SWIR)
Authors: Betchaida D Payot, Shoji Arai, Henry JB Dick, Natsue Abe, Yuji Ichiyama
Publication title: Mineralogy and Petrology 108(4): 533-549, August 2013
Abstract:
Recent reassessment of abyssal peridotites obtained during the dredging of the oblique supersegment and the easternmost subsection of the Southwest Indian Ridge by the R/V Knorr Cruise 162 and the R/V Yokosuka YK98-07 revealed the occurrence of dunites containing podiform chromitites and dunites with variable chromite concentration closely associated with lherzolite and harzburgite. The size of the chromitite pods varies from a few mm to 2 cm in width. Chromites in the podifom chromitites have very low Cr# (=0.22–0.23) and low TiO2 (<0.17 wt%). They are almost free of silicate inclusions except for a few euhedral sulfide grains which occur far from cracks and lamellae and are considered primary in origin. The lherzolite which possibly represents the wallrock hosting the dunites with podiform chromitites also show low spinel Cr#(=0.16) and low Cr# in the clinopyroxenes (=0.09–0.10) and orthopyroxenes (=0.07–0.09). The small size of the SWIR podiform chromitites is strongly controlled by the low Cr/Al available in the wallrock and the invading melt. The presence of sulfide inclusions and the absence of PGEs further attest to the low Cr/Al (i.e. low refractoriness) in the system involved in the genesis of the SWIR podiform chromitites. Lastly, the discovery of podiform chromitites in the SWIR implies that the formation of podiform chromitite at mid-oceanic ridges, regardless of its spreading rate, is highly possible.
Full text link: https://tinyurl.com/ycsxqnjc
Article title: Textural Evidence for the Chromite-Oversaturated Character of the Melt Involved in Podiform Chromitite Formation
Authors: Betchaida D Payot, Shoji Arai, Rodolfo A Tamayo Jr, Graciano P Yumul Jr
Publication title: Resource Geology 63(3): 313-319, July 2013
Abstract:
Well-preserved oval-shaped dunite clots occur within the exceptionally fresh massive podiform chromitites from the Coto Block of the Zambales Ophiolite Complex, the Philippines. The dunite/chromitite boundary shows an interlocking texture; olivine inclusions in chromites in the podiform chromitites show the same optical extinction with larger adjacent olivines in the dunite clots. This texture was formed by the reaction between chromite-oversaturated melt and its dunite inclusions. The existence of such type of melt was previously only hypothesized to explain the origin of layered and podiform chromitites but is now confirmed by this discovery.
Full text link: https://tinyurl.com/y9s8mvwm
Article title: Lithospheric mantle connection of clinopyroxene inclusions in chromites from the Archean Nuasahi ultramafic-mafic complex (India)
Authors: Sisir Mondal, Shoji Arai, Betchaida D. Payot, Akihiro Tamura
Conference title: GOLDSCHMIDT 2013, Florence Italy
Abstract: No abstract
Article title: Petrographical and geochemical characteristics of the sheeted dyke-gabbro transition zone in ODP/IODP Hole 1256D
Authors: Marie Phyton, Lyderic France, Benedicte Abily, Natsue Abe, J. C. Alt, Marguerite Godard, Benoit Ildefonse, Jurgen Koepke, M. D. Kurtz, R. Oizumi, B. D. Payot
Conference title: EGU General Assembly 2012
Abstract:
During IODP Expedition 335, high grade granoblastic hornfels were extensively recovered as drilling cuttings at the gabbro-sheeted dyke transition zone of ODP Hole 1256D (East Pacific Rise, 6°44.163'N, 91°56.061'W). This lithology probably results from high-temperature metamorphism of previously hydrothermally altered diabases and/or basalts; the heat source likely stems from the melt lens located at the top of the magmatic chambers imaged along present-day fast-spreading ridges. This lithology, associated with gabbroic bodies, characterises the transition zone between the sheeted dyke complex and the uppermost gabbroic section, and represents the interface between magmatic and hydrothermal convecting systems in an oceanic crust formed at fast-spreading ridges. In this study, 14 samples from the junk basket (cuttings) and 2 samples from cores obtained during Expedition 335 were observed and analysed. The petrological and chemical characteristics of 5 granoblastic samples collected during Expedition 312 at the root of the sheeted dyke complex and between two gabbroic horizons were also acquired for comparison. Samples collected during IODP Expedition 335 are mainly fine grained oxide grabbronorites composed of two pyroxenes, plagioclases and oxides (ilmenite, magnetite) with more or less amphiboles, sulphides, quartz and accessory minerals. Orthopyroxene Shape (roundish or anhedral), the amount of oxide inclusions in clinopyroxene and plagioclase morphology (laths or triple-junction mosaic) indicate various recrystallisation degrees. Plagioclases show a strong zoning in the less recrystallised samples, which tend to disappear with increasing recrystallisation degree. Samples show usually low alteration (less than 10%) with moderate transformation of pyroxenes into talc or actinolite. Samples from Expedition 312 show finer grains, higher degree of alteration (up to 30%), and weaker recrystallisation. They are mainly composed of plagioclases, amphibole and oxides (ilmenite, magnetite) with more or less pyroxenes, quartz and alteration phases. Samples from the higher stratigraphic level (root of the sheeted dyke complex above the shallowest gabbro) are virtually free of pyroxenes while the strongly recrystallised samples from the bottom of the hole (i.e. closer to the gabbroic section) contain only episodic amphibole and are rich in pyroxenes. The composition of plagioclase ranges from An12 to An85, with higher anorthite contents observed in the most recrystallised samples. Pyroxenes composition ranges from Wo37En46Fs17 to Wo46En38Fs16 for Cpx and Wo4En59Fs37 to Wo2En65Fs33 for Opx, and does not show any significant variation with the recrystallisation degree. Temperatures of recrystallisation were estimated between 902 and 980°C using the two-pyroxenes geothermometer. Heating and probable partial melting resulting from magmatic activity below hydrothermally altered sheeted dyke complex would lead to metamorphism and recrystallisation associated with light elements migration. This process would lead to variations in the modal composition of the rock and in the chemical composition of the minerals stable in hydrothermal and magmatic conditions.
Article title: IODP expedition 335: deep sampling in ODP hole 1256D
Authors: Damon AH Teagle, Benoit Ildefonse, Henry J. B. Dick, Daisuke Endo, E. C. Ferre, Lyderic France, Marguerite Godard, Gilles Guerin, Michelle Harris, Yoom-Mi Kim, Juergen H. Koepke, Mark Kurz, Peter Blum, Johan Lissenberg, Sumyo Miyashita, Antony Morris, Ryo Oizumi, Betchaida D. Payot
Publication title: Scientific Drilling 13: 28-34 April 2012
Abstract:
Observations of the gabbroic layers of untectonized ocean crust are essential to test theoretical models of the accretion of new crust at mid-ocean ridges. Integrated Ocean Drilling Program (IODP) Expedition 335 ("Superfast Spreading Rate Crust 4") returned to Ocean Drilling Program (ODP) Hole 1256D with the intention of deepening this reference penetration of intact ocean crust a significant distance (~350 m) into cumulate gabbros. Three earlier cruises to Hole 1256D (ODP 206, IODP 309/312) have drilled through the sediments, lavas, and dikes and 100 m into a complex dike-gabbro transition zone. Operations on IODP Expedition 335 proved challenging throughout, with almost three weeks spent re-opening and securing unstable sections of the hole. When coring commenced, the comprehensive destruction of the coring bit required further remedial operations to remove junk and huge volumes of accumulated drill cuttings. Hole-cleaning operations using junk baskets were successful, and they recovered large irregular samples that document a hitherto unseen sequence of evolving geological conditions and the intimate coupling between temporally and spatially intercalated intrusive, hydrothermal, contact-metamorphic, partial melting, and retrogressive processes. Hole 1256D is now clean of junk, and it has been thoroughly cleared of the drill cuttings that hampered operations during this and previous expeditions. At the end of Expedition 335, we briefly resumed coring before undertaking cementing operations to secure problematic intervals. To ensure the greatest scientific return from the huge efforts to stabilize this primary ocean lithosphere reference site, it would be prudent to resume the deepening of Hole 1256D in the nearest possible future while it is open to full depth.
Full text link: https://tinyurl.com/ydxnuc82
Article title: A chromian spinel-oversaturated melt for podiform chromitite formation: Evidence from well-preserved dunite clots in massive podiform chromitites in the Coto Block, Zambales Ophiolite Complex, Philippines
Authors: BD Payot, S Arai, RA Tamayo Jr, GP Yumul Jr
Publication Title: EGUGA pp5858, April 2012
Abstract:
Oval-shaped dunite clots occur within massive podiform chromitites in the Coto Block of the Zambales Ophiolite Complex, Philippines. The size of the well-preserved dunite clots ranges from 3-4 cm in length and 1.5-2 cm in width. These dunite clots are composed mainly of olivine, spinel and very minor amounts of serpentine. Olivines are mostly subhedral and coarse-grained reaching up to 3 mm across. Compared to the spinels in the massive podiform chromitites, the dark brown spinels in dunite are anhedral to subhedral and are generally smaller (<0.5 mm). The massive podiform chromitites hosting the dunite clots are primarily composed of spinel (95%) with olivine, plagioclase, serpentine and chlorite as the interstitial silicate matrix (5%). The reddish brown spinels are subhedral to euhedral and are coarse-grained reaching up to 5 mm across. The contact between the massive podiform chromitites and the dunite is very ragged and irregular. Near the contact, rounded to lobate olivine grains (<0.5 mm in diameter) occur as inclusions within the spinels in the massive podiform chromitites. These olivine inclusions show the same/continuous optical extinction as the adjacent and large olivines in the dunite. The Cr# of chromian spinel in the dunite clots and the massive podiform chromitites falls within a very narrow range (Cr#=0.42-0.52). However, the Cr# of the chromian spinel in the dunite clots (Cr#=0.47-0.52) is slightly higher than the massive podiform chromitites (Cr#=0.46-0.0.48). The former similarly shows higher Fe3+ content than the latter. TiO2 content of the chromian spinels in the dunite clots and the massive podiform chromitites is generally low (<0.11 wt%). Olivines in the dunite clots show slightly lower Fo content (=93-95) than the olivines in the interstices of the massive podiform chromitites (=95-96). The former similarly have lower NiO contents (=0.40-0.59 wt%) compared to the latter (=0.50-0.84 wt%). The occurrence of the well-preserved dunite clots in the massive podiform chromitites possibly provide us with evidence to indicate the chromian spinel-oversaturated character of the melt involved in the formation of podiform chromitite. The existence of such type of melt was only hypothesized by Irvine (1977) based on the interpretation of stratiform chromitite genesis.
Article title: Abyssal harzburgite veined by silica-oversaturated melt in the Sibuyan Ultramafics, Romblon, Central Philippines
Authors: Betchaida D Payot, Shoji Arai, Rodolfo A Tamayo Jr
Publication title: Journal of Mineralogical and Petrological Sciences 106(3): 175-180, June 2011
Abstract:
Thin discordant gabbronorite veins (~0.5 mm to 3 cm in width) occur within remarkably fresh harzburgite boulders of the Sibuyan Ultrarnafics. The harzburgite host rock displays protogranular to porphyroclastic textures and is dominantly composed of olivine. orthopyroxene with minor amounts of clinopyroxene, spinel and am-plubole. The mineral chemistry of the harzburgite is comparable to depleted abyssal perklotites as shown by the Fo content of the ohvine (= 90-91) and Cr# of the spinel (= 0.40-0.52). The gabbronorites are coarse-grained adcumulates and comprised of orthopyroxene, plagioclase and amphibole. Plagioclase hi the gabbronorites shows high An content whereas both oithopyroxene and amphibole show variable Mg# almost similar to reported values from arc gabbros. The contact between the harzburgite and the gabbronorite veins is demarcated by the foimation of secondary orthopyroxene with low Cr2O3 and CaO contents. Clinopyroxetie in the harzbur-gite shows strong enrichment in light rare earth elements (LREEs). Amphibole rimming the clinopyroxene in the harzburgite has similar patterns as the clinopyroxene but with much higher REE abundance. The amphibole in the gabbronorites also shows enrichment in LREEs, Rb, Ba and Ti. We propose that the harzburgite-gab-bronorite occurrence in the Sibuyan Ultrarnafics is a product of mantle-melt reaction. The metasornatic agent is a silicate melt enriched in Si, Cr, Fe and LREEs. At a bigger scale, the harzburgite-gabbionoiite connection observed in the Sibuyan Ultramafics possibly documents early stage modification and conversion of abyssal peri-dotites to ophiolitic peridotites by SSZ-related melts.
Full text link: https://tinyurl.com/ybaanaf9
Article title: Unusual ultra-depleted dunite from Sibuyan Island (the Philippines): A residue for ultra-depleted MORB?
Authors: Betchaida D Payot, Shoji Arai, Akihiro Tamura, Satoko Ishimaru, Rodolfo A Tamayo Jr
Publication title: Journal of mineralogical and petrological sciences, January 2010
Abstract:
Ultra-depleted dunites from the Sibuyan Island, Romblon (Central Philippines) are primarily composed of olivine, orthopyroxene (<5%), trace clinopyroxene and chromian spinel and are totally free of hydrous Minerals and plagioclase. Mineral chemistry shows very refractory compositions (olivine Fo = 92-94; spinel Cr# > 0.75). Rare clinopyroxene preserved in the Ultra-depleted dunites is anhedral and interstitial to olivine grains. They are neither subsolidus exsolution products from orthopyroxene nor metasomatic in origin. Clinopyroxene has high Mg# = 0.94-0.97 and low Al2O3 Contents (<0.85 wt%). They are also very depleted in trace elements with only selected heavy rare earth elements detected during the LA-ICP-MS analysis. Light to middle REEs and LILEs were hardly detected, which is indicative of the very depleted character of the melt that precipitated the clinopyroxene. The calculated melts in equilibrium with the clinopyroxene have heavy REE contents similar to olivine-hosted ultra-depleted melts of MORB affinity from the East Pacific Rise and the Mid-Atlantic Ridge. The formation of the Sibuyan Ultra-depleted dunites is being attributed to extremely high degree of dry melting below a mid-oceanic ridge.
Full text link: https://tinyurl.com/yccvm9fj
Article title: What underlies the Philippine island arc? Clues from the Calaton Hill, Tablas island, Romblon (Central Philippines)
Authors: BD Payot, S Arai, RA Tamayo Jr, GP Yumul Jr.
Publication title: Journal of Asian Earth Sciences 36 (4-5): 371-389, October 2009
Abstract:
We report here for the first time the occurrence of a high-temperature metamorphic/plutonic complex (amphibolites, metagabbros, hornblende pyroxenites and hornblendites) in Calaton Hill, Tablas island, Romblon, Central Philippines. The mineral assemblages and relic magmatic textures in these rocks imply apparent derivation from arc-related protoliths. Major element and trace element data are also comparable to those of gabbroic rocks in arc-related setting. Subsolidus re-equilibration under granulite to amphibolite facies is documented by the triple junctions between mineral phases in the different lithologies, the recrystallization of plagioclase and the presence of coronas around olivine with mineral assemblage of orthopyroxene + amphibole ± green spinel. The formation of hornblendite and the pervasive occurrence of amphiboles in the different lithologies are being attributed to the infiltration of a younger hydrous arc magma which also caused metamorphism and hybridization on the surrounding rocks. The characteristics of the Calaton Hill samples are comparable with those of the well-studied xenoliths from Ichinomegata, NE Honshu arc, Japan. We therefore interpret the Calaton Hill metamorphic/plutonic complex as representative of the lower crust underlying the Philippine island arc.
Article title: Geology and Hydrothermal Alteration of the Low Sulfidation
Authors: Betchaida D Payot, Victor B Maglambayan, Carla B Dimalanta, Graciano P Yumul, Rodolfo A Tamayo, Toshihiko Matsuda, Shigeyuki Suzuki, Herve Bellon
Publication title: Resource Geology 55(3): 155-162, November 2008
Abstract:
The Pantingan Gold System (PGS) is a vein-type epithermal prospect exposed within the summit caldera of Mount Mariveles, Bagac, Bataan (Luzon), Philippines. It consists of nine major veins, eight of which trend NW-WNW and distributed in an en echelon array. The eastern tips of these veins appear to terminate near the NE-NNE trending Vein 1, which is located in the easternmost portion of the prospect. Metal assay results on vein and wall rock samples indicate concentrations of 0.01 to 1.1 g/ton Au, trace to 34 g/ton Ag and 0.003 to 0.02 % Cu. Andesite lava flow deposits host the PGS. Potassium-Argon isotopic dating of these andesites yields a narrow age range of 0.88± 0.13 to 1.13 ± 0.17 Ma. The surface exposures of the veins (up to 5 m wide) are encountered at different levels between 590–740 masl. These commonly display a massive texture although banding prominently occurs in Vein 1. The veins consist of gray to cream-colored crystalline and chalcedonic quartz and amorphous silica. Pyrite is the most ubiquitous sulfide mineral. It occurs either as fine-grained disseminations and aggregates in quartz or as infillings in vugs. Calcite, marcasite and bornite are also occasionally noted in the deposit. The prospect shows silicic, argillic, propylitic and advanced argillic alteration zones. Silicic and argillic alterations are confined in the immediate wall rocks of the quartz veins. Argillic alteration grades to a propylitic zone farther away from the veins. The advanced argillic alteration zone, indicated by a suite of acidic clay minerals that include kaolin-ite, dickite, pyrophyllite and alunite, might have been imprinted during the late stages of gold deposition. As a whole, the PGS displays geological and mineralogical features typical of gold mineralization in a low sulfidation, epithermal environment. It is also representative of a young, tectonically undisturbed gold deposit.
Article title: Metasomatic interactions between slab-derived melts and depleted mantle: Insights from xenoliths within Monglo adakite (Luzon arc, Philippines)
Authors: M Grégoire, Sébastien Jégo, RC Maury, Mireille Polvé, B Payot, RA Tamayo Jr, GP Yumul Jr
Publication title: Lithos 103 (3-4): 415-430, July 2008
Abstract:
The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous supra-subduction zone ophiolitic complex located within the Luzon arc crust. Spinel-bearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibole-rich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it.
Full text link: https://tinyurl.com/ya4vxkg7
Article title: Behavior of Major and Trace Elements during Ore Deposition: Example from the Low‐Sulfidation Pantingan Gold System, Mount Mariveles, Bataan, Philippines
Authors: Betchaida D Payot, Rodolfo A Tamayo Jr, Victor B Maglambayan, Carla B Dimalanta, Graciano P Yumul Jr, Shigeyuki Suzuki, Mei‐Fu Zhou
Publication title: Resource geology 57 (2): 180-196, June 2007
Abstract:
The evaluation of the relatively fresh host rock and altered rock samples associated with the Pantingan Gold System exposed in Mount Mariveles, Bataan yield several notable observations that are useful in pinpointing potential gold pathfinder elements. Geochemical and petrologic analysis showed that the altered rocks can be subdivided into rocks that underwent propylitic alteration (group 1), argillized rocks with silica contents similar to those of the fresh host rocks (group 2), argillized but not strongly silicified rocks (group 3) and argillized and strongly silicified rocks (group 4). Selected element ratio patterns in the altered rocks and gold concentrations in gold-bearing quartz veins vary between the rock groups. Moreover, mass balance calculation also reflected the geochemical observations pertaining to the gains and losses of SiO2, Fe2O3+ MgO, CaO + Na2O and K2O, which are believed to be chemical reactions (i.e. breakdown of plagioclase, silica inundation or leaching, sulfide and calcite formation) caused by the influx of hydrothermal fluids.
Article title: Temporal Geochemical Evolution of Neogene Magmatism in the Baguio Gold–Copper Mining District (Northern Luzon, Philippines)
Authors: Mireille Polvé, Rene C Maury, Sebastien Jego, Hervé Bellon, Ahmed Margoum, Graciano P Yumul Jr, Betchaida D Payot, Rodolfo A Tamayo Jr, Joseph Cotten
Publication title: Resource Geology 57(2): 197-218, June 2007
Abstract:
Baguio, in the Central Cordillera of Northern Luzon, is a district that displays porphyry copper and epithermal gold mineralization, associated with Early Miocene–Pliocene–Quaternary calc-alkaline and adakitic intrusions. Systematic sampling, K-Ar dating, major and trace elements, and Sr, Nd, Pb isotopic analyses of fresh magmatic rocks indicate three magmatic pulses: an Early Miocene phase (21.2–18.7 Ma), a Middle–Late Miocene phase (15.3–8 Ma) and finally a Pliocene–Quaternary event (3–1 Ma). The first phase emplaced evolved calc-alkaline magmas, essentially within the Agno Batholith complex, and is thought to be related to the westward-dipping subduction of the West Philippine Basin. After a quiescence period during which the Kennon limestone was deposited, magmatic activity resumed at 15.3 Ma, in connection with the start of the subduction of the South China Sea along the Manila Trench. It emplaced first petrogenetically related and relatively unradiogenic low-K calc-alkaline lavas and intermediate adakites. Temporal geochemical patterns observed from 15.3 to 1 Ma include progressive enrichment in K and other large ion lithophile elements, increase in radiogenic Sr and Pb and corresponding decrease in radiogenic Nd. These features are thought to reflect the progressive addition to the Luzon arc mantle wedge of incompatible elements largely inherited from South China Sea sediments. The origin of the long quiescence period, from 8 to 3 Ma, remains problematic. It might represent a local consequence of the docking of the Zambales ophiolitic terrane to Northern Luzon. Then, magmatic activity resumed at 3 Ma, emplacing chemically diversified rocks ranging from low K to high K and including a large proportion of adakites, especially during the Quaternary (dacitic plugs). The authors tentatively relate this diversity to the development of a slab tear linked with the subduction of the fossil South China Sea ridge beneath the Baguio area.
Full text link: https://tinyurl.com/yc2smofh
Article title: The oceanic substratum of Northern Luzon: Evidence from xenoliths within Monglo adakite (the Philippines)
Authors: Betchaida D Payot, Sebastien Jego, Rene C Maury, Mireille Polve, Michel Gregoire, Georges Ceuleneer, Rodolfo A Tamayo Jr, Graciano P Yumul Jr, Herve Bellon, Joseph Cotten
Publication title: Island Arc 16(2): 276-290, February 2007
Abstract:
A 8.65 Ma adakitic intrusive sheet exposed near Monglo village in the Baguio District of Northern Luzon contains a suite of ultramafic and mafic xenoliths including in order of abundance: spinel dunites showing typical mantle-related textures, mineral and bulk rock compositions, and serpentinites derived from them; amphibole-rich gabbros displaying incompatible element patterns similar to those of flat or moderately enriched back-arc basin basalt magmas; and amphibolites derived from metabasalts and/or metagabbros of identical affinity. A single quartz diorite xenolith carrying a similar subduction-related geochemical signature has also been sampled. One amphibolite xenolith provided a whole-rock K-Ar age of 115.6 Ma (Barremian). We attribute the origin of this suite to the sampling by ascending adakitic magmas of a Lower Cretaceous ophiolitic complex located at a depth within the 30-35 km thick Luzon crust. It could represent an equivalent of the Isabela-Aurora and Pugo-Lepanto ophiolitic massifs exposed in Northern Luzon.
Full text link: https://tinyurl.com/ycrzxrme
Article title: Geology and Hydrothermal Alteration of the Low Sulfidation Pantingan Gold System, Mount Mariveles, Bataan (Luzon), Philippines
Authors: Betchaida D Payot, Victor B Maglambayan, Carla B Dimalanta, Graciano P Yumul, Rodolfo A Tamayo, Toshihiko Matsuda, Shigeyuki Suzuki, Herve Bellon
Publication title: Resource Geology 55(3): 155-162, January 2005
Abstract:
The Pantingan Gold System (PGS) is a vein-type epithermal prospect exposed within the summit caldera of Mount Mariveles, Bagac, Bataan (Luzon), Philippines. It consists of nine major veins, eight of which trend NW-WNW and distributed in an en echelon array. The eastern tips of these veins appear to terminate near the NE-NNE trending Vein 1, which is located in the easternmost portion of the prospect. Metal assay results on vein and wall rock samples indicate concentrations of 0.01 to 1.1 g/ton Au, trace to 34 g/ton Ag and 0.003 to 0.02 % Cu. Andesite lava flow deposits host the PGS. Potassium-Argon isotopic dating of these andesites yields a narrow age range of 0.88 +/- 0.13 to 1.13 +/- 0.17 Ma. The surface exposures of the veins (up to 5 m wide) are encountered at different levels between 590-740 masl. These commonly display a massive texture although banding prominently occurs in Vein 1. The veins consist of gray to cream-colored crystalline and chalcedonic quartz and amorphous silica. Pyrite is the most ubiquitous sulfide mineral. It occurs either as fine-grained disseminations and aggregates in quartz or as infillings in vugs. Calcite, marcasite and bornite are also occasionally noted in the deposit. The prospect shows silicic, argillic, propylitic and advanced argillic alteration zones. Silicic and argillic alterations are confined in the immediate wall rocks of the quartz veins. Argillic alteration grades to a propylitic zone farther away from the veins. The advanced argillic alteration zone, indicated by a suite of acidic clay minerals that include kaolinite, dickite, pyrophyllite and alunite, might have been imprinted during the late stages of gold deposition. As a whole, the PGS displays geological and mineralogical features typical of gold mineralization in a low sulfidation, epithermal environment. It is also representative of a young, tectonically undisturbed gold deposit.