新疆阿吾拉勒西段流纹岩及其对该区岩石圈深部过程的约束  

Geochronology,geochemistry and petrogenesis of the Early Permian rhyolite and its constraints on the lithosphere deep processes of the Western Awulale,Xinjiang

作　　者：丁振信[1,2] 薛春纪[1,2] 赵晓波[1,2] 闫永红 亚夏尔.亚力坤 冯博[1,2] 罗晖[1,2] 俎波[1,2] 张祺[1,2] 代志杰 

机构地区：[1]地质过程与矿产资源国家重点实验室 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]中信矿业科技发展有限公司,北京100004

出　　处：《地学前缘》2014年第5期196-210,共15页Earth Science Frontiers

基　　金：国家自然科学基金项目(U1303292);国家科技支撑计划项目(2011BAB06B02);中国地质调查局地质大调查项目(1212011085069;121211220926)

摘　　要：西天山二叠纪的岩石圈深部过程是备受关注的地球动力学问题,新疆阿吾拉勒西段下二叠统流纹岩提供了理解这个问题的良好机会。阿吾拉勒西段流纹岩发育流纹构造、斑状结构,斑晶主要为条纹长石、斜长石和石英,长英质基质呈雏晶-微晶结构。岩石为富硅（66.97%～79.00%）、高钾（2.86%～11.07%）钙碱性、准铝质（A/CNK=0.91～0.99）岩浆系列。流纹岩富集U、Th和K等元素,明显亏损Nb、Ta、Eu、P等元素,显示εNd（t）正值（4.7～5.1）和低的初始锶比值（（87 Sr/86 Sr）i=0.705 1～0.705 6）,锆石饱和温度为818～909℃,幔源物质明显。与高分异I型花岗岩地球化学性质相似,岩浆可能起源于壳-幔边界早石炭世新生下地壳的部分熔融。流纹岩锆石U-Pb法测年获得（290.9±3.3）Ma和（296.3±3.1）Ma的早二叠世成岩年龄,岩浆的起源可能与北天山洋关闭之后洋壳岩石圈板块尾部断离导致软流圈物质和能量上涌并引起新生下地壳底部重熔等深部过程有关。The lithosphere deep processes of the Western Tianshan during the Early Permian is an important geodynamical issue that has attracted considerable attention. The study of rhyolite of the Lower Permian, which exposed in the west of the Awulale area, will provide us a rare opportunity to address this important issue. The rhyolites have typical fluxion structure with porphyritic texture. The rhyolite rocks are composed of perthite, plagioclase and quartz phenocrysts set in a groundmass of crystallite-microcrystalline structural felsic minerals. The rhyolites are characterized by high contents of SiQe （66. 97%- 79. 00%） and K2O（2. 86%- 11.07%）, and belonging to calc-alkaline and metaluminous （A/CNK= 0. 91 -0. 99） magma series, and displaying positive U, Th, and K anomalies, together with strong negative Nb, Ta, Eu, and P anomalies. These rocks show whole-rock εNd （t） value of ＋4. 7 to ＋5. 1, together with low 87 Sr/86 Sr）： of 0. 7051 to O. 7056 and zircon saturated temperature of 818 ℃to 909 ℃. The rhyolites are characterized by enrichment of mantle material and similarity with high fraetionated I-type granite. Therefore, the rhyolite magma is considered to have been derived from the partial melting of crust-mantle boundary of the Early Carboniferous Juvenile lower crust. Two rhyolite samples yielded zircon UPb ages of 290. 9±3.3 Ma and 296.3±3.1 Ma, which represent the eruption age of the Early Permian rhyolite magma. The origin of the rhyolite magma might be related to the deep remelting process of the Juvenile lower crust bottom during the upwelling of asthenosphere material and energy that resulted from the break off of the oceanic lithosphere plate tail that postdated the closure of the North Tianshan ocean.

关 键 词：流纹岩 二叠纪 岩石圈深部过程 阿吾拉勒西段 新疆西天山 

分 类 号：P588.141[天文地球—岩石学]