东昆仑哈拉森地区花岗岩类岩石成因及地质意义  

Petrogenesis and Geological Implications of Granitoids from Halasen,East Kunlun

作　　者：何成 王力圆[3] 田立明[4] 徐净 He Cheng1,2, Wang Liyuan3, Tian Liming4 , Xu Jing5(1.Hubei Key Laboratory of Earthquake Early Warning, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China 2.Wuhan Institute of Earthquake Engineering Co., Ltd., Wuhan 430071, China 3.College of Zijin Mining, Fuzhou University, Fuzhou 350116, China 4.Geophysical and Geochemical Exploration Brigade of J iangxi, Nanchang 330201, China 5.Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, Chin)

机构地区：[1]中国地震局地震研究所,地震预警湖北省重点实验室,湖北武汉430071 [2]武汉地震工程研究院有限公司,湖北武汉430071 [3]福州大学紫金矿业学院,福建福州350116 [4]江西省地矿局物化探大队,江西南昌330201 [5]中国科学院地质与地球物理研究所,北京100029

出　　处：《地球科学》2018年第4期1207-1218,共12页Earth Science

基　　金：国家自然科学基金(No.41402098); 青藏高原矿产调查评价专项项目(No.1212011220664)

摘　　要：哈拉森地区位于东昆仑东段,分布着大量花岗岩,对其研究不仅有助于认识东昆仑造山带在晚古生代-早中生代的构造-岩浆演化历史,而且可以为东昆仑古特提斯洋俯冲时限及洋盆闭合时限提供约束.对区内花岗岩进行了岩石学、年代学以及岩石地球化学分析,结果表明哈拉森地区的钾长花岗岩和细粒二长花岗岩锆石LA-ICP-MS U-Pb年龄分别为239.2±1.7Ma(MSWD=0.19)和232.4±1.2Ma(MSWD=0.76),属中三叠世花岗质岩浆作用的产物.岩石主微量元素分析显示该地区花岗岩具有高硅铝、富碱和低钛特征,属于高钾钙碱性到钾玄岩系列的过铝质花岗岩,富集轻稀土元素(LREE)及K、Th、Rb等大离子亲石元素(LILE),明显亏损Nb、Ti、P、Ta等高场强元素(HFSE),具有非常明显的Eu负异常(δEu为0.27~0.65).哈拉森地区花岗岩具有高分异I型花岗岩的特征,是同碰撞背景下幔源岩浆与其诱发地壳物质熔融产生的长英质岩浆在地壳深部混合,随后这一混合岩浆又经过高程度的分异演化形成的,进一步证明东昆仑古特提斯洋的俯冲作用一直持续到早三叠世,至中三叠世才逐渐转入陆内碰撞造山阶段.A large amount of granites widely distributes in Halasen area in the East Kunlun Mountains.The study of the granites not only help us to understand the tectono-magmatic evolution history of East Kunlun orogenic belt in the Late Paleozoic and Early Mesozoic,but also provides constraints for the subduction and closed time limit of the Paleo-Tethys Ocean.In this paper,we constrain geochronology and petrogenesis of the Halasen granites by zircon U-Pb dating and geochemical analyses.The LA-ICP-MS U-Pb analyses show that the formation ages of K-feldspar granite and fine-grained monzogranite are 239.2±1.7 Ma（MSWD=0.19）and 232.4±1.2 Ma（MSWD =0.76）,respectively,which are the products of the Middle Triassic granitic magmatism.The geochemistry data show that granites are high-potassium calcalkaline-shoshonite,peraluminous rock which is characterized by high silicon and aluminum,enriched alkali,low titanium,as well as enriched light rare earth elements（LREE）and large ion lithophile elements（LILE,e.g.,K,Th and Rb）,and depleted in high field-strength elements（HFSE,e.g.,Nb,Ti,P,and Ta）with obvious Eu negative anomaly（the value ofδEu is between 0.27 and 0.65）.Halasen granites belong to highly fractionated I-type granite.It is suggested that the Halasen granites were most likely derived from parental magma by mixing of depleted mantle-derived magma and induced crustal-melted felsic magma in the deep crust,and then suffered further differentiation during magma ascent.The subduction of the East Kunlun PaleoTethys Ocean lasted to the Early Triassic,and the Middle Triassic witnessed the intracontinental collision.

关 键 词：花岗岩 地质年代学 地球化学 哈拉森 东昆仑 

分 类 号：P581[天文地球—岩石学]