东天山觉罗塔格雅满苏花岗岩岩石学、地球化学特征及其板内构造意义  

Petrological and Geochemical Characteristics of the Yamansu Pluton in the Qoltag Area,East Tianshan Mountains and Their Intra-continental Tectonic Significance

作　　者：赵宏刚[1] 苏锐[1] 梁积伟[2] 金远新[1] 欧光习[1] 姜晓辉[1] ZHAO Honggang;SU Rui;LIANG Jiwei;JIN Yuanxin;OU Guangxi;JIANG Xiaohui(CNNC Key Laboratory on Geological Disposal of High-level Radioactive Waste,Beijing Research Institute of Uranium Geology,Beijing,100029;College of Earth Sciences and Resource,Chang＇an University,Xi＇an,710054)

机构地区：[1]中核集团高放废物地质处置重点实验室核工业北京地质研究院,北京100029 [2]长安大学地球科学与资源学院,西安710054

出　　处：《地质学报》2018年第9期1780-1802,共23页Acta Geologica Sinica

基　　金：国防科工局"核设施退役和三废治理"项目"我国高放废物地质处置新疆预选区选址和场址评价"资助成果

摘　　要：雅满苏花岗岩体由27个侵入体组成,按岩石谱系划分为三个岩相单元,归并为一个超单元,其为同一次岩浆熔融事件过程中曾经发生过三次岩浆侵入活动而形成的椭圆形的深成岩体。LA-ICP-MS锆石U-Pb定年结果表明,雅满苏岩体侵位于中三叠世(227~230Ma),为印支中期的产物。来自岩体的锆石原位Hf同位素测定结果表明,ε_(Hf)(t)值变化于7.7~11.5之间,二阶段Hf模式年龄(T_(DM2))变化于530~776Ma之间,表明其岩浆源区均为来源于亏损地幔的新生地壳岩石。该岩体总体富硅(SiO_2为70.73%~78.12%),富碱(K_2O+Na_2O为7.17%~8.53%),富钾(K_2O/Na_2O为1.1~1.89),而Ti、Ca、Fe和Mg含量较低,(K_2O+Na_2O)/Al_2O_3为0.75~0.91,A/CNK为0.98~1.03,属于高钾钙碱性花岗岩。总体上富集大离子亲石元素(LILE)K、Rb和高场强元素(HFSE)Th,但贫Hf、Zr、Sm、Y及Yb,稀土元素的球粒陨石标准化配分曲线呈右倾型,轻重稀土分馏大,轻稀土分异明显,而重稀土分异不显著,铕呈现弱负异常(δEu=0.38~0.74)。岩石学及地球化学特征研究表明,雅满苏岩体形成与幔源岩浆的内侵使得新元古代年轻的地壳物质发生部分熔融有关。岩浆侵入活动的动力来源于海西晚期至印支早期古特提斯洋向北俯冲和碰撞及随后的板内伸展作用。The Yamansu granite pluton consists of 27 intrusive rocks,which can be divided into three lithofacies units but belong to one superunit.The ellipse-shaped plutonic body was the product of three intrusive activities of the same magama.Zircon LA-ICP-MS U-Pb dating result shows that the Yamansu pluton intrusion occurred in the Middle Triassic between 227 Ma and 230 Ma and was the product of the Early Indosinnian Period.Zircon in-situ Hf isotopic composition analysis of the Yamansu pluton yielded theεHf（t）values between 7.7～11.5 and the two stage Hf mode age（TDM2）varying between 530～776 Ma,suggesting that the magma originated from depleted mantle-derived juvenile crustal rock.Geochemically,the pluton is characterized by the high contents of SiO2（70.73%～78.12%）and K2O＋Na2O（7.17%～8.53%）,the high ratios of K2O/Na2O（1.1～1.89）,and the low contents of Ti,Ca,Fe and Mg,with the ratios of（K2O＋Na2O）/Al2O3 varying between 0.75 and 0.91,and the ratios of A/CNK between 0.98 and 1.03.All these features indicate that the pluton belongs to high K calc-alkaline granite.The pluton is enrich in LILE（K,Rb）and HFSE（Th）but depleted in Hf,Zr,Sm,Y and Yb.The chondritenormalised REE distribution pattern of the Yamansu pluton displayed right skewed shapes,distinct fractionation between LREE and HREE,with slightly negative Eu anomalies（δEu=0.38～0.74）.The petrological and geochemical features of the Yamansu pluton indicate that the pluton originated from partial melting of Neoproterozoic new-born crust due to mantle magma intraplating.The magma intrusion was driven by northward subduction and collision of the Tethys Ocean from the Late Hercynian to Early Indosinian,and the subsequent intense intra-continental extention in the East Tianshan Mountains.

关 键 词：花岗岩 地球化学 印支期 板内伸展 雅满苏 东天山 

分 类 号：P588.121[天文地球—岩石学]