东天山土屋-延东铜矿矿区晚志留世岩体的发现及构造意义  

Discovery of the Late Silurian granodiorite and its tectonic significance in the Tuwu-Yandong porphyry copper deposits,Dananhu-Tousuquan island arc,Eastern Tianshan

作　　者：肖兵[1,2] 陈华勇[1] 王云峰[1,2] 杨俊弢 

机构地区：[1]中国科学院广州地球化学研究所中国科学院矿物学与成矿学重点实验室,广东广州510640 [2]中国科学院大学,北京100049 [3]新疆地质矿产开发局第一地质大队,新疆昌吉831100

出　　处：《地学前缘》2015年第6期251-266,共16页Earth Science Frontiers

基　　金：国家重点基础研究发展计划"973"项目"新疆北部古弧盆体系成矿机理"(2014CB440802)

摘　　要：东天山大南湖—头苏泉岛弧带位于吐哈盆地南缘,是中亚造山带的重要组成部分,也是我国新疆地区最重要的成矿带之一,其形成时间和构造属性一直存在争议。本次研究首次在该岛弧带中最大的斑岩矿床土屋-延东铜矿区发现了晚志留世花岗闪长岩,并对其进行详细的岩石学、年代学、全岩元素地球化学和Sr-Nd-Hf同位素分析,探讨其岩浆来源和构造背景。LA-ICP-MS锆石U-Pb定年结果显示,该岩体成岩年龄为420 Ma左右,为晚志留世岩浆活动的产物。全岩元素地球化学研究结果表明,花岗闪长岩显示准铝质到弱过铝质,中等镁值和钙碱性系列的地球化学特征;微量元素方面则富集轻稀土（LREE）元素、大离子亲石元素（LILE：Rb,Ba,K）和地球化学性质活泼的不相容元素（U,Th,Pb）,相对亏损高场强元素（HFSE：Nb,Ta,Ti）。这些主微量元素地球化学特征均显示出岛弧岩浆岩的地球化学属性,其εNd（t）值为4.05-4.07,87 Sr/86Sr初始值为0.704 149-0.704 520,εHf（t）值为8.91-11.66。Sr-Nd-Hf同位素特征表明它们来源于新生地壳,没有受到明显的古老大陆地壳混染。晚志留世花岗闪长岩体的发现表明：大南湖—头苏泉岛弧带与其北部的哈尔里克岛弧带在早古生代可能属于同一大洋岛弧,并且与中部的卡拉塔格—小热泉子弧后（间）盆地构成统一的弧盆体系,该认识对解构东天山古生代弧盆体系演化具有较为重要的地质意义。The Dananhu-Tousuquan island belt,located along the southern margin of the Turpan-Hami basin,is an important part of the Central Asian Orogenic Belt and ranks one of the most important metallogenic belts in Xinjiang,NW China.However,its precise formation age and tectonic setting are still controversial.In this study,we identified for the first time a Late Silurian granodiorite in the largest Tuwu-Yandong porphyry Cu belt in this island belt.The zircon U-Pb dating indicated that the granodiorite was emplaced at about 420 Ma.The granodiorite is characterized by metaluminous to weakly peraluminous,medium Mg#values and calcalkaline compositions;it is enriched in light rare earth elements,Rb,Ba,K,U,Th,and Pb,and depleted in Nb,Ta and Ti;itsεNd（t）value is between 4.05 and 4.07,its ISr（t）value is between 0.704149 and 0.704520 and itsεHf（t）value is between 8.91 and 11.66.These geochemical data indicate that the magma that formed the granodiorite was produced through partial melting of juvenile crust under the setting of island arc without obvious contamination of ancient continental crust.The discovery of the Late Silurian granodiorite,combined with previous studies,shows that the Dananhu-Tousuquan island arc belt and the Harlik island arc belt belong to the same island arc in the Early Paleozoic and constructed an integrated arc-basin system with the KalatageXiaorequanzi back-arc basin.This knowledge is of great significance to the Late Paleozoic arc-basin evolution of the Eastern Tianshan Mountains.

关 键 词：东天山 大南湖—头苏泉 土屋-延东铜矿 早古生代 花岗闪长岩 

分 类 号：P588.12[天文地球—岩石学]