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Ground magnetic surveys conducted in Suyoc, Mankayan, Benguet led to the delineation of features related to epithermal and porphyry copper targets in the area. High reduced to equator (RTE) anomalies are observed in areas with epithermal mineralization. The high RTE anomalies are attributed to hydrothermally altered rock with quartz veins. The previously recognized porphyry copper prospect in Palasaan (Mohong Hill) is characterized by low RTE anomaly surrounded by a high RTE anomaly. One explanation for this signature is the possible presence of a magnetic core and the destruction or absence of magnetite in the alteration haloes at the periphery of a porphyry prospect. Areas such as Mangga and Liten exhibit the same magnetic signatures. This distinct magnetic pattern coupled with observed alteration and mineralization signatures led to the interpretation of prospective blind porphyry deposits in these localities. Results of the study reveal the applicability of ground magnetic data in characterizing and extracting a potential area of mineralized zones at a regional scale. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Suyoc vein prospect is an intermediate sulfidation epithermal. • δD and δ18O compositions indicate typical late stage formation. • There is potential presence of cogenetic porphyry Cu and high sulfidation epithermal. The Suyoc prospect is an epithermal vein-type mineralization located at the southern part of the Mankayan Mineral District, Northern Luzon, Philippines. The prospect's epithermal veins are hosted in volcaniclastic rocks and conglomerate, which belong to the Late Oligocene to Early Miocene Balili Formation and the Middle to Late Miocene Suyoc Conglomerate, respectively. These veins are classified into three major types: quartz vein, quartz-sulfide vein, and quartz-carbonate vein. The quartz vein exhibits massive and cockade textures associated with pyrite + chalcopyrite. The quartz-sulfide vein consists of massive and comb quartz associated with pyrite + chalcopyrite + sphalerite. The quartz-carbonate vein has massive quartz associated with rhodochrosite and chalcopyrite + sphalerite + galena + Au/Ag ± bournonite. In addition, massive gypsum ± pyrite occurs as a minor vein-type. Fluid inclusion measurements in quartz from the three major vein-types revealed 230–250 °C formation temperatures and 1.0–3.5 wt. % NaCl equivalent salinity, which are values consistent with epithermal deposits. Quartz textures (e.g., massive, cockade, comb, crustiform) and dominance of liquid-rich fluid inclusions do not suggest that boiling is a primary mechanism of vein deposition. Possible mechanisms are inferred as meteoric water dilution based on homogenization versus salinity trend in quartz vein and presence of rhodochrosite in quartz-carbonate vein, and wall rock interaction based on FeS trend in sphalerite crystals of the quartz-carbonate vein. The presence of pyrite and chalcopyrite in the major vein-types and the FeS mole percent values (0.51 to 8.30) in quartz-carbonate vein indicate an intermediate sulfidation state. The alteration minerals illite, chlorite, pyrite and quartz indicate near-neutral pH condition. δ34S values, which vary from −1.1 to +3.9‰, suggest reduced condition when compared to the representative bulk δ34S value for the Mankayan Mineral District. The characteristics and conditions strongly indicate an intermediate sulfidation epithermal (ISE) style of mineralization. Moreover, the δD water (−63 to −66‰) and δ18O water (−3.9 to −1.1‰) values from the major vein-types suggest late stage formation in a magmatic-hydrothermal system similar to other ISE deposits in the Northern Luzon Segment (e.g., Victoria, Acupan and Antamok). Given these, the presence of the Suyoc ISE veins in the underexplored southern part of the Mankayan Mineral District implies potential presence of undiscovered cogenetic porphyry Cu and high sulfidation epithermal mineralization in the area. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition from barren to fertile geochemical signatures of arc magmas in the Baguio-Mankayan Mineral District is intimately linked with arc development and subduction dynamics. • Late Eocene barren magmas were generated in a thin nascent Luzon arc. • Middle Pliocene fertile magmas were formed from mixing of mafic and silicic melts associated with ridge subduction. • More hydrous conditions of Early Pleistocene fertile magmas are attributed to progressive crustal thickening and compression induced by ride subduction. The Baguio-Mankayan Mineral District (BMMD) in Northern Luzon, Philippines, is renowned for its world-class auriferous porphyry-Cu and epithermal deposits, which are associated with arc magmatism during the Pliocene-Pleistocene. One of the less studied areas in this region is in southern Mankayan, where the Suyoc epithermal prospect is located. New U-Pb zircon ages, combined with whole-rock and in-situ geochemical analyses of igneous rocks in the Suyoc area, revealed a shift from barren to fertile magmatic episodes in the BMMD. 1) Late Eocene (36.93–37.20 Ma) barren magmas generated in a thin, nascent Luzon arc, 2) Fertile Middle Pliocene (2.87–3.4 Ma) magmatism attributed to the mixing of primitive mafic and silicic crustal melts due to ridge subduction, and 3) Early Pleistocene (1.73 Ma) fertile magmatism associated with more hydrous melts due to progressive crustal thickening. The Late Eocene barren magmatism enhanced both source and intra-crustal conditions for the onset of younger fertile magmatic events via sub-arc modification and crustal addition/thickening. Furthermore, we consider the fertile Pliocene and Pleistocene magmatism in the BMMD as two separate events with different petrogenesis. Mafic-silicic interaction in the Pliocene was documented through core-rim analysis of amphiboles from the Pliocene Suyoc Diorite. On the other hand, the Pleistocene fertile magmatism, represented by the Bato Dacite Porphyry, showed geochemical signatures consistent with a thickened crust and also reflected higher magmatic H 2 O contents ranging from 6.3 to 7.8 wt%. [ABSTRACT FROM AUTHOR]