新疆南天山泥盆纪钙碱性侵入岩的形成时代、地球化学特征及构造意义  

Geochronology and geochemistry characteristics of the Devoniancalcium-alkaline intrusive rocks in Southern Tianshan and their tectonic implications

作　　者：贾晓亮 翟明国[3,4] 郭瑞清 尼加提.阿布都逊 秦切 JIA XiaoLiang ZHAI MingGuo GUO RuiQing NIJIATI Abuduxun QIN Qie(Xinjiang Research Center for Mineral Resources, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi＇ an 710069, China Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China School of Geology and Mining Engineering, Xinjiang University, Urumqi 830047, China Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China)

机构地区：[1]中国科学院新疆生态与地理研究所,新疆矿产资源研究中心,乌鲁木齐830011 [2]中国科学院新疆生态与地理研究所,荒漠与绿洲生态国家重点实验室,乌鲁木齐830011 [3]西北大学地质学系,大陆动力学国家重点实验室,西安710069 [4]中国科学院地质与地球物理研究所矿产资源重点实验室,北京100029 [5]新疆大学地质与矿业工程学院,乌鲁木齐830047 [6]中国地质科学院地质研究所,北京100037

出　　处：《岩石学报》2017年第10期3057-3075,共19页Acta Petrologica Sinica

基　　金：中国科学院"西部之光"人才培养引进计划(2016-QNXZ-B-14);"973"项目(2012CB4166006);国家自然科学基金项目(41502213)联合资助

摘　　要：南天山位于中亚造山带南部,塔里木盆地北缘。长期以来,有关其在古生代时期的演化规律、南天山古洋盆的俯冲方式、俯冲作用规模、持续时间及闭合时限等科学问题研究都是地学界的热点。本研究报道了出露于南天山造山带南缘(塔里木克拉通北缘)的咔拉吾勒及欧西达坂古生代钙碱性侵入岩的锆石U-Pb-Hf同位素及地球化学数据,其中咔拉吾勒细粒闪长岩、欧西达坂花岗闪长岩及钾长花岗岩的年龄分别为413.2±5.5Ma、407.3±5.1Ma及409.3±5.2Ma,都形成于早泥盆世。结合前人对研究区欧西达坂石英闪长岩的年代学(418.4±2.2Ma)及地球化学数据,确定了泥盆纪时期南天山南缘发育一套钙碱性的闪长岩-石英闪长岩-花岗闪长岩-花岗岩的岩石组合,各岩体表现出相近的时空分布及地球化学特征,判断各岩石应为同源岩浆结晶分异的产物。欧西达坂花岗闪长岩的锆石Lu-Hf同位素数据显示出较大范围的176Hf/177Hf比值(0.282185~0.282901)、εHf(t)值(-12.0~12.9)及t DM2模式年龄(573~2149Ma),体现出新老地壳物质混染的特征,指示其母岩浆为混合岩浆。结合各岩石富集大离子亲石元素(LILE)(如:Rb、Ba、Th、Sr),亏损高场强元素(HFSE)(如:Nb、Ta、Zr、Hf)及低Nb/Ta比值等特征,本研究推断该岩石组合为弧岩浆岩系列,其母岩浆可能产生于俯冲消减构造环境下新生玄武质岩浆与老陆壳重熔酸性岩浆的混合,并经历了一定的结晶分异而成岩。进一步的综合分析表明,南天山南缘古生代中期一系列岩浆活动的时代至少从晚奥陶世一直持续到晚石炭世-早二叠世,而南天山古洋盆至少于奥陶纪期间向北(伊犁-中天山地块)发生单向俯冲。晚奥陶世-泥盆纪期间,其东、西两段的俯冲极性或有所不同,西段或为持续的北向俯冲,东部地区为向南北双向俯冲,塔里木北缘在该侧转变为活动大陆边缘。本研究旨在为南天山造山�The Southern Tianshan Belt constitutes part of the Central Asian Orogenic Belt（CAOB）,located in the northern margin of the Tarim block and formed during the Paleozoic era.Over the past decade,our understanding of the tectonic evolution of Southern Tianshan Belt remains discordant,particularly to subduction polarity and closure timing of the Paleo-South Tianshan Oceans.In this study,through analysis of petrography,whole rock geochemistry,zircon U-Pb-Hf isotopes and previously study results in the Kalawule and Ouxidaban areas,we recognized Paleozoic calcium-alkaline intrusive suites where exposed in south margin of the Southern Tianshan Belt.The zircon U-Pb dating yield crystallization ages of 413.2±5.5 Ma for Kalawule diorite and 418.4±2.2 Ma,407.3±5.1 Ma,409.3±5.2 Ma for Ouxidaban quartz diorite,granodiorite,K-feldspar granite,respectively,revealing an Early Devonian magmatic event.Zircon Lu-Hf isotopes analysis of Ouxidaban granodiorite yield variable ^176 Hf/^177 Hf ratios ranging from 0.282185 to 0.282901 and εHf（t） values between -12.0 and 12.9 with two-stage Hf model ages varying from 573 Ma to 2149 Ma,reflecting that the rock was sourced from mixing compositions of both juvenile and recycling crustal material.Geochemical datas show that these rocks have close geochemical affinity with similar trace element and REE distribution patterns,indicating that they may experience crystallization differentiation of single parent magma.In addition,all these rocks are enriched in LILEs,such as Rb,Ba,Th,Sr,but relatively depleted in HFSEs,such as Nb,Ta,Zr,Hf,with low Nb/Ta ratios（〈17）,resembling the geochemical features of the plate convergence edge arc intrusive rocks.The parental magma of these rocks were likely generated by partial melting of mantle wedge facilitated by dehydration of the subducted slab,and accompanied by mixing of granitic/acid magma in melting processes.This magma has undergone the crystal fractionation process during late magmatism and finally formed the intermediate-acid rock s

关 键 词：新疆南天山 泥盆纪 钙碱性侵入岩 锆石U-Pb-Hf同位素 弧岩浆活动 构造演化 

分 类 号：P588.121[天文地球—岩石学] P588.122[天文地球—地质学]