%0 Journal Article
%T The Yushugou-Tonghuashan ophiolites in Tianshan, Xinjiang, and their tectonic setting<br>新疆天山地区榆树沟-铜花山蛇绿岩特征和构造背景
%A XU XiangZhen
%A YANG JingSui
%A GUO GuoLin
%A LI TianFu
%A REN YuFeng
%A CHEN SongYong
%A <br>徐向珍
%A 杨经绥
%A 郭国林
%A 李天福
%A 任玉峰
%A 陈松永
%J 岩石学报
%D 2011
%I 
%X The Yushugou-Tonghuashan ophiolite, outcropped in the northern part of the southern Tianshan between Yili plate and Tarim plate, has tectonically broken into ultramafic rocks, cumulates and volcanic lavas. The ophiolite is chiefly composed of harzburgite, one kind of typical depleted peridotite. The olivines are forsterite (Fo is about 90), enstatite (En is about 90) and a few clinopyroxene. The accessory mineral chrome spinel bears the Cr#=Cr/(Cr+Al)×100 value of 16~28, the Mg#=(Mg+Fe)×100 value of 63~75, suggesting a low chromium and abyssal peridotite features. After the anhydration, the contents of MgO (38.84%~44.53%), Al2O3 (1.51%~3.63%) and CaO (0.42%~5.77%) of Yushugou ultramafic rocks are similar to the oceanic lherzolite. The Tonghuashan ultramafic rocks occurred in carbonatite bearing the LREE enrichment might be produced by certain subduction fluid alteration. The volcanic lavas occur widely here, in Yushugou is mainly basalt while in Tonghuashan is andesite and dacite. Most of the volcanic lavas have undergone the moderate greenschist seafloor hydrothermal alteration. REE contents of Tonghuashan basalt are higher that of Yushugou, REE patterns are LREE enrichment type. The trace element compositions of basalt indicate they may suffer from the fluid influence. There are three high-Mg volcanic rock samples, according to the various features like the extreme low SiO2 content (32%~36%), high MgO content (20.12%~28.50%) and the value of K2O+Na2O (0.06%~0.46%) less than 2%, which can be judged as picrite. The cumulate, generally locates in the ultramafic rocks or mafic lavas as small blocks, is mostly gabbro with less olivine pyroxenite and with significant alteration and structural deformation, which is similar to the basalt in composition and with two type LREE patterns including enriched and slightly depleted. According to the geochemical features, the Yushugou-Tonghuashan ophiolite was produced in Mid-Ocean Ridge (MOR) environment, with certain subduction fluid alteration and was associated with the generation of island-arc volcanic rocks.
%K Ultramafic rocks
%K Ophiolite
%K Yushugou
%K Tonghuashan
%K Tianshan Mountain<br>超镁铁岩
%K 蛇绿岩
%K 榆树沟
%K 铜花山
%K 天山
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=621CF755B1A341E5&jid=2013B5467E3054B1614CEC199353FCED&aid=19D40CFF4B361E3F362B134E19157A4F&yid=9377ED8094509821&vid=DB817633AA4F79B9&iid=CA4FD0336C81A37A&sid=6700D0D256586E73&eid=2B5DE8A23DCEED39&journal_id=1000-0569&journal_name=岩石学报&referenced_num=1&reference_num=32