The seawater osmium isotope record of South China Sea; implications on its history and evolution

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Author(s): Marquez, Ren Thomas; Tejada, M. L. G.; Suzuki, K.; Peleo-Alampay, A.; Goto, K. T.
Author Affiliation(s): Primary:
University of the Philippines, Quezon City, Philippines
Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
University of the Philippines, Diliman, Philippines
Geological Survey of Japan, Tsukuba, Japan
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The South China Sea is the largest marginal basin in the world, and is located in the confluence of three major tectonic plates (Pacific-Philippine Sea, Indo-Australia, Eurasia). Its tectonic history and evolution throughout the Cenozoic has been the subject of much discussion with regards to its mechanism, timing, and relationship to neighboring geological features. We conduct the first Re-Os isotope study of the sedimentary records from cores recovered from ocean drilling (ODP-Ocean Drilling Program, and IODP-International Ocean Discovery Program) and Philippine oil drilling operations in order to investigate whether or not the basin's tectonic evolution will be reflected in the seawater Os isotope record. These cores represent the northwest and southeast conjugate margins of the SCS, and should have complementary records of the tectonic events in the basin. In addition, we also compare the Os isotope record for the SCS basin with global data in order to establish the connectivity of the SCS to the global ocean. At the northern margin, excursions to unradiogenic 187Os/188Os values of 0.37 and 0.31 during the start of seafloor spreading at ≈33 Ma are consistent with the effects from an increased flux of mantle-derived material. However, the negative excursion already found in the global ocean limits the interpretation of this excursion as being due to the local effects of spreading, and instead implies connectivity to global circulations up until pre-Oligocene. This connectivity is further confirmed by post-spreading values being consistent with measurements from previous global records across the Cenozoic. The southern conjugate margin has Middle Miocene 187Os/188Os values consistent with the global ocean record, but shows more unradiogenic values starting from the Late Miocene. The study explores the feasibility of this deviation being associated with differences in sedimentation history and post-spreading magmatic intrusions south of the relic spreading center in the East subbasin.
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; International Ocean Discovery Program; Isotope ratios; Isotopes; Metals; North Pacific; Northwest Pacific; Ocean Drilling Program; Os-187/Os-186; Os-188/Os-187; Osmium; Pacific Ocean; Platinum group; Radioactive isotopes; South China Sea; Stable isotopes; West Pacific
Record ID: 2018001745
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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