Geochemical evidence for sundering of the West Mariana arc in miocene ash from the Parece Vela Basin |
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| Authors: | Russell J. Warner Martin F.J. Flower Kelvin S. Rodolfo |
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| Affiliation: | 1. Key Laboratory of Marine Geology and Environment & Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China;3. Radiogenic Isotope Laboratory, Centre for Microscopy and Microanalysis, The University of Queensland, Brisbane, Queensland 4072, Australia;4. Department of Earth Sciences, University of California Santa Barbara, Santa Barbara, CA 93106, United States;5. The Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China;6. School of Marine Sciences, Sun Yat-Sen University, Guang Zhou, 510275, China;1. CAS Key Lab of Marine Geology and Environment, Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;3. Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China;4. CAS Key Laboratory of Crust-Mantle Materials and Environments, University of Science and Technology of China, Hefei 230026, China;5. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;6. Centre for Pure and Applied Geology, University of Sindh, Jamshoro 76080, Pakistan;7. Geosciences Division, Mines and Geosciences Bureau Region VII (MGB-7), Mandaue 6014, Philippines;1. State Key Laboratory of Marine Geology, Tongji University, Shanghai, China;2. Depart. of Earth Ocean and Atmospheric Science and NHMFL, Florida State University, Tallahassee, USA;3. Isotropics Geochemistry Laboratory, School of Earth and Environmental Science, James Cook University, Townsville, Australia;4. Depart. of Earth & Atmospheric Sciences, University of Houston, Houston, USA;5. Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France;6. School of Earth and Environment, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand;7. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China;8. GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany;9. Kiel University, Institute of Geosciences, 24118 Kiel, Germany;1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China;2. School of Ocean and Earth Science, University of Southampton, NOC, Southampton, SO14 3ZH, UK;3. Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK;4. Institut für Mineralogie, Universität zu Köln, Germany;5. Department of Geology, Utah State University, Logan, UT, USA;6. School of Geosciences, University of South Florida, Tampa, FL, USA;7. Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France;8. Department of Earth and Environmental Sciences, University of Iowa, Iowa City, IA, USA;9. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, UK;1. Department of Earth and Environment, AHC5-394, Florida International University, Miami, FL 33199, USA;2. School of Earth, Ocean and Environment, University of South Carolina, 701 Sumter Street, EWSC617, Columbia, SC 29208, USA;3. Geological Survey of Japan/AIST, Central 7 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan;4. Research and Development Center for Ocean Drilling Science, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan;5. Institute of Earth Sciences, University of Lausanne, Geopolis, Lausanne 1015, Switzerland;6. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, United Kingdom;7. Research School of Earth Sciences, Australian National University, Canberra, ACT 2601, Australia |
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| Abstract: | Glass and mineral fragments from discrete volcanic ash layers were sampled from DSDP/IPOD Site 450 in the Parece Vela Basin, Philippine Sea and analyzed by electron microprobe. The ashes are interpreted as eruptive products of the adjacent West Mariana arc system between 25 and 14 Ma B.P., and have compositions between basaltic andesite and rhyolite, and rarely, boninite. ‘Continuous’ chemical trends appear to reflect mixing of mafic and silicic magmas. ‘Discontinuous’ trends between these end-members are relatively few, and are consistent with ‘liquid lines’ produced by fractional crystallization. Andesitic tephra become progressively richer in MgO and CaO through the middle Miocene, while boninite appears towards the end of the sequence, between 14 and 15 Ma B.P. Coeval rhyolitic glasses become richer in K2O and Na2O, with maximum concentrations at about 15 Ma B.P. Chronologic changes in fractionation type and composition of parent magmas are interpreted to reflect the subaerial volcanic evolution of the West Mariana arc. The appearance of boninite is believed to signal early stages of arc sundering, and corresponds temporally with regional uplift of the sea floor above the carbonate compensation depth, precursor to a new pulse of back-arc spreading. |
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