地质学报2018，Vol.92Issue(2)：298-312,15.
新疆西准噶尔北部和布克赛尔蛇绿混杂岩的厘定及其洋盆闭合时代限定
Determination of the Hebukesaier Ophiolitic Mélange in the Northern Part of West Junggar and its Tectonic Implications
摘要
Abstract
Detailed field work helped identify threedifferent assemblages of rocks occurring in the Hebukesaier ophiolitic mélange in the northern region of West Junggar.They are typical ophiolite unit mainly consists of metamorphic peridotite,gabbro,diabasic dike,basalt and chert;ocean island unit mainly consists of OIB,which coexists closely with silicolit,silica mudstone and limestone;and post-collision volcanic rock unit is mainly metarhyolite.Gabbro and diabase in ophiolite are characterized by slight enrichment or depletion in light rare earth elements and low (a/Yb)N ratios of 0.54～3.18,no obvious Eu anomalies,indicating that both are of E-MORB and N-MRB characteristic.The ocean island basalt shows relatively high contents of Al2O3 (3.66％～15.83％),TiO2 (2.62％～3.15％) and Na2O+K2O (5.71％～7％),and displays an obvious right-leaning pattern with a high content of rare earth elements.Metarhyolites exhibit relatively high SiO2 and K2O contents,and extremely low MgO,CaO and MnO contents,enrichment of incompatible elements (K,Rb,Th,U and Pb),obvious depletion of Sr,P and Ti,and weak depletions of Nb and Ta.Geochemical characteristics indicate that metarhyolites may be formed in a post-orogenic extension setting.LA-ICP-MS U-Pb dating on zircons from metarhyolite yieldes a weighted mean 206Pb/238U age of 435±2 Ma.Metarhyolites cut through or intruded different units of ophiolite (peridotite,diabase and basalt),suggesting that the Paleo-ocean basin of Hebukesaier ophiolite had been closed before late Early Silurian.关键词
蛇绿岩/洋岛玄武岩/流纹岩/西准噶尔/造山后伸展/侵位时代Key words
ophiolite/OIB/rhyolite/West Junggar/post-orogenic extension/emplacement age引用本文复制引用
杨亚琦,赵磊,徐芹芹,郑荣国,牛宝贵..新疆西准噶尔北部和布克赛尔蛇绿混杂岩的厘定及其洋盆闭合时代限定[J].地质学报,2018,92(2):298-312,15.基金项目
本文为国家自然科学基金项目(编号41572206和41202159)和中国地质调查项目(编号121201102000150009)资助的成果. （编号41572206和41202159）
