HR: 1340h
AN: V43A-1566    [Abstracts]
TI: Fluid inclusions associated with exsolution quartz needles in omphacite of UHP eclogites from the main hole of Chinese continental scientific drilling project
AU: Zhang, Z
EM: zzm@ccsd.cn
AF: Institute of Geology, Chinese Academy of Geological Sciences, Baiwanzhuang Road No. 26, Beijing, BJ 100037 China
AU: Shen, K
EM: zzm@ccsd.org.cn
AF: Shandong Institute and Laboratory of Geological Sciences, Jinan, Jinan, SD 250013 China
AU: * Liou, J
EM: liou@pangea.Stanford.EDU
AF: Department of Geological and Environmental Sciences, Stanford University, Stanford, Stanford, CA CA94305 United States
AU: Xu, Z
EM: xuzhiqin@ccsd.org.cn
AF: Institute of Geology, Chinese Academy of Geological Sciences, Baiwanzhuang Road No. 26, Beijing, BJ 100037 China
AB: Abundant primary fluid inclusions are recognized in omphacite of ultrahigh-pressure (UHP) eclogites from the main hole of the Chinese Continental Scientific Drilling (CCSD), located at the southern Sulu orogenic belt. The eclogites consist of garnet, omphacite, coesite and rutile. Mineral and fluid inclusions are distributed alternatively and parallel to each other. The solid inclusions occur as needles with a length of 10~100 ŬIm and a width of 1~10 ŬIm whereas the fluid inclusions occur as tubes with the size varying from less then 3~5 ŬIm to greater then 50 ŬIm. The mineral inclusions were identified as quartz. Most fluid inclusions contain a gas bubble, a liquid phase and one to several solids. The liquid and gas phases are determined as H2O. The solid phases include halite, quartz and calcite, as well as opaque and unknown minerals. Some small thin-tubed fluid inclusions contain little or no solid and even without gas bubble; they contain dominantly water. The inclusion fluid was estimated to contain components in the system of NaCl-CaCl2-CO2-H2O-SiO2 with possibly trace Fe and Mg. We suggest that these fluid inclusions were conventional primary ones, and trapped during omphacite crystallization; upon decompression they acted as nucleation site for the crystallographically controlled precipitation of quartz from the omphacite matrix. Therefore the omphacite is considered to be one of the major fluid carriers during subduction of continental crust to mantle depths.
DE: 1043 Fluid and melt inclusion geochemistry
DE: 3654 Ultra-high pressure metamorphism
DE: 3660 Metamorphic petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005