西天山博罗霍洛地区晚泥盆世岩体地球化学、U-Pb年代及Sr-Nd-Pb同位素特征及地质意义  

Geochemical,zircon U-Pb dating and Sr-Nd-Pb isotope characteristics for Late Devonian pluton of the Boluohuoluo area,West Tianshan and its geological implication

作　　者：高景刚[1] 李文渊[2] 高云霞[1] 张照伟[2] 周汝洪[3] 

机构地区：[1]长安大学地球科学与资源学院,西部矿产资源与地质工程教育部重点实验室,西安710054 [2]西安地质矿产研究所,西安710054 [3]新疆维吾尔自治区地质矿产勘查开发局,乌鲁木齐830000

出　　处：《岩石学报》2016年第5期1379-1390,共12页Acta Petrologica Sinica

基　　金：中国地质调查局工作项目(1212011085069、1212011121092、12120113078200)资助

摘　　要：西天山博罗霍洛地区位于伊犁地块和准噶尔板块之间的造山带内,自西向东圈定尼勒克河、艾木斯呆依、当本第二个达坂等3个泥盆纪岩体,是由角闪石黑云母花岗闪长岩、角闪石黑云母二长花岗岩构成复式岩体。岩体具有暗色矿物多,较低的SiO_2、相对高的Al_2O_3和碱总量,属准铝质-弱过铝质的钙碱性系列岩石。主量元素和微量元素总体特征一致,富集大离子亲石元素(Ba、Rb、K、Th),相对亏损高场强元素(Zr、Y、Yb),稀土配分曲线且与陆壳区花岗岩相似,暗示形成岩体的岩浆是地壳部分熔融形成。2个岩体的锶同位素初始值ISr和εNd(t)分别为0.7062~0.7091和-3.00^-1.24,tDM2介于1220~1363Ma之间,暗示岩浆源区可能来源于元古代复杂的基底的部分熔融。铅同位素特征显示壳幔混源的特点。对艾木斯呆依和当本第二达坂两岩体的锆石SHRIMP U-Pb测年结果表明,两岩体的形成年龄分别为368.2±2.2Ma和367.3±2.2Ma,指示其形成于晚泥盆世。结合区域地质背景,推测岩体的形成与古亚洲洋盆在晚志留世-晚泥盆世闭合造山过程有关,可能为碰撞造山阶段晚期增厚地壳熔融的产物。The Boluohuoluo area of West Tianshan is located in the orogen between Yili landmass and Junggar plate. From west to east,the three delineated Devonian pluton： Nilekeriver,Aimusidaiyi and the second Daban of Dangben respectively,constitute a complex massif that consist of hornblende biotite granodiorite and hornblende biotite monzonitic granite. The rock masses are characterized by high content of dark minerals,lower content of SiO_2,relatively high content of Al_2O_3 and total alkali,attributed to metaluminous-weakly peraluminous calc-alkalic rock series. Major element and trace element have the consistent general characteristics,which display enrichment of LILE（ Ba,Rb,K,Th）,depletion of HFSE（ Zr,Y,Yb） and similarity in the REE distribution curve of continental crust granite,and which suggest that the magma of the rock masses form from partial melting of crust.Initial Sr isotope values ISrand εNd（ t） of two rocks respectively are 0. 7062 ~ 0. 7091 and-3. 00 ^-1. 24,tDM2 is between 1220 ~1363Ma,which implies the magma source should have come from partial melting of complex Proterozoic base. The Pb isotope features imply characteristics of crust-mantle mixed-source. SHRIMP zircon U-Pb dating of Aimusidaiyi and the second Daban of Dangben indicate that the formation ages of the two rock masses are 368. 2 ± 2. 2Ma and 367. 3 ± 2. 2Ma respectively,shows that the rock masses have formed in the Late Devonian. Combined with regional background,it is speculated that the formation of rock masses is related to close orogenic processes of Paleo-Asian Ocean basin in Late Silurian to Late Devonian and the rock masses may be the products of partial melting of thicken crust in later collision orogenic period.

关 键 词：SHRIMP U-PB年代学 地球化学 SR-ND-PB同位素 西天山 新疆 

分 类 号：P588.121[天文地球—岩石学]