新疆西天山呼斯特杂岩体岩石学、锆石U-Pb年龄及Hf同位素特征  

Petrology,zircon U-Pb geochronology and Hf isotopes of the Husite complex in West Tianshan,Xinjiang

作　　者：章永梅[1] 张力强 高虎 李卫东 胡志军 万阈 袁鹏 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]武警黄金部队第四支队,辽阳111000 [3]中陕核工业集团地质调查院有限公司,西安710100 [4]新疆维吾尔自治区地质勘查基金项目管理中心,乌鲁木齐830000 [5]新疆地矿局第七地质大队,乌苏833000

出　　处：《岩石学报》2016年第6期1749-1769,共21页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41572062;41302064;U1303292);中央返还两权价款资金综合研究项目(Y15-1-LQ04);国家科技支撑计划项目(2011BAB06B02-02);高等学校博士学科点专项科研基金新教师类资助课题(20130022120016);中央高校基本科研业务费专项资金(2-9-2013-010)联合资助

摘　　要：呼斯特岩体是新疆西天山博罗科努岛弧带上的一个与矽卡岩成矿有关的复式杂岩体,由二长花岗岩、花岗闪长岩、正长花岗岩、花岗细晶岩、闪长玢岩、辉长岩和中基性包体等组成。本文对该岩体不同岩相岩石开展了岩石学、锆石LAICP-MS U-Pb同位素定年和Hf同位素研究,探讨岩石成因及构造意义。锆石U-Pb定年结果表明,正长花岗岩、闪长玢岩、花岗闪长岩和二长花岗岩加权平均年龄分别为380.2±4.6Ma、372.8±5.9Ma、367.7±4.5Ma和366.2±4.5Ma,岩体侵位时代为晚泥盆世,在大约15Myr期间,至少发生了3-4次岩浆侵入。在地球化学组成上,除辉长岩外,岩体为准铝质-弱过铝质、高钾钙碱性-低钾（拉斑）系列的I型花岗岩,轻重稀土分馏明显,具Eu负异常;富集Th、U,亏损Ba、P和高场强元素（如Nb、Ta、Zr、Ti）,为晚古生代北天山洋向南俯冲于伊犁地块背景下岩浆活动的产物。二长花岗岩锆石Hf同位素组成较为均一,εHf（t）值为1.3-3.0,二阶段Hf模式年龄为1171-1280Ma,远大于成岩年龄,说明原始岩浆从地幔分异后经历了较长时间的地壳滞留。研究认为,高钾中酸性岩（花岗岩、闪长玢岩和中基性包体）由元古代新生基性下地壳部分熔融而成,伴有受俯冲沉积物熔体交代的幔源岩浆混合。低钾花岗闪长岩高Sr、低Y和Yb,属O型埃达克岩,与同源的辉长岩一起由俯冲的大洋板片部分熔融形成,源岩为低钾的拉斑玄武岩。The Husite intrusion is one of the complexs related to skarn-type mineralization in the Boluokenu island arc belt of the West Tianshan,Xinjiang. It is composed of monzonitic granite,granodiorite,syenogranite,granitic aplite,dioritic porphyrite,gabbro and mafic microgranular enclaves. In this paper,we present new whole-rock data,U-Pb ages and Hf isotopic data for rocks from different lithofacies,in order to discuss the petrogenesis and tectonic setting of the complex. LA-ICP-MS U-Pb isotopic dating on zircons from syenogranite,dioritic porphyrite,granodiorite,and monzonitic granite yielded ages of 380. 2 ± 4. 6Ma,372. 8 ± 5. 9Ma,367. 7 ± 4. 5Ma and 366. 2 ± 4. 5Ma,respectively. During about 15 million years,there were three or four episodes of synchronous magmatism in Devonian. Geochemically,the granitic rocks are metaluminous to weakly peraluminous I-type granites of high potassium calc-alkaline to low potassium series. They are enriched in light rare-earth elements（ LREE）,Th and U with a negative Eu anomaly,and are depleted in high field strength elements（ e. g. Nb,Ta,Zr and Ti）,representing products of the southward subduction of the North Tianshan ocean under the Yili plate during Late Paleozoic. The εHf（ t） values of monzonitic granite are uniform,ranging from1. 3 to 3. 0. The two-stage Hf model ages（ tDM2= 1171 - 1280Ma） are much older than the intrusive time,indicating the parental magma had a long resident time within the crust after differentiation from the mantle. It is thus suggested that the intermediate to felsic rocks of high potassium series including granite,dioritic porphyrite and mafic microgranular enclaves were likely derived from partial melting of the Proterozoic juvenile mafic lower crust,with involvement of a mantle-derived magma interacted with subducted sediments.The granodiorite of low potassium series is characterized by high contents of Sr and low concentrations of Y and Yb,and belongs to Otype adakites. Both granodiorite and gabbro were derived from partial meltin

关 键 词：锆石U-PB年龄 HF同位素 呼斯特杂岩体 新疆西天山 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]