Early Cretaceous high-Mg adakites associated with Cu-Au mineralization in the Cebu Island,Central Philippines: Implication for partial melting of the paleo-Pacific Plate |
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| Institution: | 1. School of Earth Sciences and Engineering, Sun Yat–sen University, Guangzhou 510275, China;2. Guangdong Key Lab of Geodynamics and Geohazards, Guangzhou 510275, China;3. State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China;4. Department of Geological Sciences, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;5. Department of Applied Geology, Curtin University, Perth 6102, Australia;1. Southeast Asia Research Group, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK;2. GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW 2522, Australia;1. EarthByte Group, School of Geosciences, The University of Sydney, NSW 2006, Australia;2. Oil Search Limited, Sydney, NSW 2000, Australia;3. Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, USA;1. College of Earth Sciences, Jilin University, Changchun 130061, PR China;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China;3. Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, USA;4. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, PR China |
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| Abstract: | Early Cretaceous arc volcanic rocks, diorite intrusions and an associated large porphyry deposit occur in the Cebu Island, Central Philippines. In this paper, we studied the diorite porphyries associated with Cu-Au mineralization in the Kansi region, where Early Cretaceous arc volcanic rocks are widely distributed. Zircon U-Pb age reveals that the diorites were formed at ca. 110 Ma, close to the formation age of Lutopan diorites in the famous Atlas porphyry Cu-Au deposit (109–101 Ma), and younger than those of the arc volcanics in this region (126–118 Ma). The Kansi diorites and Lutopan diorites are both calc-alkaline high-Mg adakites with high Sr/Y ratios. Their major elements define similar variation trends in Harker diagrams, suggesting that they were probably generated from a uniform source but experienced different degree of partial melting or fractional crystallization. The Kansi diorites are characterized by LREE enrichment, HREE depletion, no Eu negative anomaly, with enrichment of Pb, Sr, Zr and Hf and depletion of Nb, Ta, and Ti. They are probably generated by the partial melting of subducted oceanic crust, followed by a certain degree of mantle interaction and crustal contamination. The highly depleted Sr-Nd-Pb-Hf isotopes of the Kansi diorites are close to the Amami Plateau basalt and tonalite, indicating the dominance of a Pacific-type MORB in the source. The Cu-Au mineralization-related Kansi diorites are characterized by high oxygen fugacities more than ΔFMQ +2, indicating quite a good potential for porphyry Cu-Au mineralization in the region. Finally, in our tectonic model, the successive generation of arc volcanic rocks and adakites in the Cebu Island are responses to the subduction and rollback of the paleo-Pacific Plate to the proto-Philippine Sea Plate (PSP) in the Early Cretaceous. |
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| Keywords: | Adakite Slab melting Porphyry Cu deposit Paleo-Pacific Plate subduction Cebu Island Central Philippines |
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