HR: 1340h
AN: V43A-1554    [Abstracts]
TI: Magmatic Ultramafic Rock in Sulu Ultrahigh Pressure Metamorphic Belt: Depleted Oxygen isotope Evidence From Main Hole of Chinese Continental Scientific Drilling Project
AU: * Li, T
EM: litianf@ccsd.cn
AF: Key Laboratory for Continental Dynamics, Ministry of Land and Resources,. Institute of Geology, Chinese Academy of Geological Sciences, No. 26, Baiwanzhuang road, Beijing, 100037 China
AU: Rumble, D
EM: rumble@gl.ciw.edu
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, NW, Washington, DC, 20015 United States
AU: Yang, J
EM: yangjsui@ccsd.cn
AF: Key Laboratory for Continental Dynamics, Ministry of Land and Resources,. Institute of Geology, Chinese Academy of Geological Sciences, No. 26, Baiwanzhuang road, Beijing, 100037 China
AB: There are a lot of ultramafic bodies in Sulu ultrahigh pressure metamorphic belt and the research on the origin of these rock bodies has long been a hot topic. To identify if there is the ultramafic rocks that experienced shallow crustal process before subduction in this terrane, this study carried out oxygen extraction from mineral separates olivine, garnet and clinopyroxene of three peridotite samples between the depths 603.20~683.53 m of Chinese Continental Scientific Drilling (CCSD) bore hole using CO₂ laser fluorination system and isotope analysis by mass spectrometer. The results are as follows. δ ¹⁸O values of olivine are œ®3.31‰~œ®3.82‰, garnet œ®4.03‰~œ®4.10‰, and clinopyroxene œ®2.10‰ in average with larger error. The δ¹⁸O values of these mineral separates are comprehensively lower than typical mantle values. Combined with other evidences, it is indicated that the lowδ¹⁸O values of ultramafic rock in shallow crust level was got from cold meteoric water by interaction between it and the rock body and experienced afterwards subduction, UHPM, retrogressive metamorphism during exhumation etc together with wall-rocks. Theδ¹⁸O discrepancies between minerals are 0.394‰~0.791‰œ"Δgrt-olvœc, 1.933‰œ"Δgrt-cpxœc, -1.538‰œ"Δcpx-olvœc which demonstrate oxygen isotope partial equilibria between minerals and reflect isotope diffusion during retrogressive metamorphism. This is the first case that the ultramafic rocks possess ¹⁸O depleted character found in Sulu terrane. This result bears even more important continental dynamic meaning and proves that Sulu terrane is the eastward extension of Dabie terrane in respect of ultramafic rocks.
UR: http://ccsd.cn
DE: 1020 Composition of the continental crust
DE: 1031 Subduction zone processes (3060, 3613, 8170, 8413)
DE: 1038 Mantle processes (3621)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1065 Major and trace element geochemistry
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005