东天山星星峡‒红柳井地区二叠纪A型花岗质岩石成因及构造意义  

Petrogenesis and Tectonic Implications of A-Type Granitoids in the Xingxingxia-Hongliujing Area,Eastern Tianshan

作　　者：贺昕宇 方同辉[4] 杨自安[4] 杜海超[5] 刘海鹏[4] 王京 贾润幸[4] 郑文皓[4] He Xinyu;Fang Tonghui;Yang Zi’an;Du Haichao;Liu Haipeng;Wang Jing;Jia Runxing;Zheng Wenhao(Research Center for Petrogenesis and Mineralization of Granitoid Rocks,China Geological Survey,Wuhan 430205,China;School of Earth Sciences,Institute of Disater Prevention,Sanhe 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China;China Nonferrous Metals Resource Geological Survey,Beijing 100012,China;Geological Corpotation of China Gold Group,Beijing 100012,China)

机构地区：[1]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205 [2]防灾科技学院地球科学学院,河北三河065201 [3]河北省地震动力学重点实验室,河北三河065201 [4]有色金属矿产地质调查中心,北京100012 [5]中国黄金集团地质有限公司,北京100012

出　　处：《地球科学》2024年第9期3089-3105,共17页Earth Science

基　　金：中国地质调查局花岗岩成岩成矿地质研究中心开放基金(No.PM202306);河北省地震动力学重点实验室开放基金(No.FZ246101);国务院国有资产监督管理委员会项目(No.295031001000210001);中国地质调查局项目(No.DD20160011).

摘　　要：中亚造山带南缘的最终缝合时间目前还存在多种不同认识,而A型花岗岩能够为增生造山作用的终止时限提供关键约束.目前东天山南缘的A型花岗岩研究较为薄弱,本文以东天山星星峡‒红柳井地区新识别出的二长花岗岩、石英闪长岩和正长花岗岩3种二叠纪A型花岗质岩石为研究对象,进行了锆石U-Pb年代学、微量元素和岩石地球化学分析.所有二叠纪花岗质岩石都具有高硅(71.32%~76.35%)、富碱(Na_(2)O+K_(2)O=5.67%~9.18%)、弱过铝质(A/CNK=0.85~0.98)和铁质(FeOT/MgO=5.52~21.28)的特征.较为富集Pb、Hf、Zr、Sm,亏损P、Ti、Nb,Ga含量较高(18.2×10^(‒6)~31.1×10^(‒6)),Ga/Al>2.6.稀土元素总量较低(∑REE=77.67×10‒6~271.82×10^(‒6)),轻稀土较重稀土富集(LREE/HREE=2.82~16.26),其中二长花岗岩、正长花岗岩呈现出较明显的Eu负异常(δEu=0.16~0.84),石英闪长岩呈弱Eu负异常或正异常(δEu=0.85~1.20).二长花岗岩LA-ICP-MS锆石U-Pb年龄为(273.3±1.9)Ma和(273.4±3.4)Ma.A型花岗质岩石成岩物质主要来源于星星峡岩群,有少量的地幔物质贡献,二长花岗岩与正长花岗岩经历了斜长石分离结晶作用,而石英闪长岩斜长石分离结晶较弱.与正长花岗岩、石英闪长岩共生的二长花岗岩还经历了锆石分离结晶作用,锆石δEu负异常受氧逸度影响较大,独立产出的二长花岗岩还经历了榍石、磷灰石的分离结晶作用.在东天山地区307~284 Ma和273 Ma两期A型花岗岩分别形成于前缘挤压而后缘滞后拉张的背景以及后碰撞拉张环境.中亚造山带南缘的东段于~273 Ma已进入后碰撞伸展阶段,最终碰撞作用应早于273 Ma.Time of terminal accretion of the Central Asian Orogenic Belt(CAOB)is still controversial,and A-type granite in the southern margin of the CAOB can provide critical constraints on the termination of collision.However,the A-type granite in the southern margin of eastern Tianshan remains insufficiently studied.Three kinds of newly identified A-type granitoids,monzogranite,quartz diorite and syenogranite,were reported in this paper and zircon LA-ICP-MS U-Pb dating,trace elements as well as petrogeochemical analysis were conducted.All these granitoids are characterized by high SiO2(71.32%-76.35%),alkali(Na2O+K2O=5.67%-9.18%),being metaluminous(molar A/CNK=0.85-0.98)and ferroan(FeOT/MgO=5.52-21.28).The granitoids are enriched in Pb,Hf,Zr,Sm,but depleted in P,Ti,Nb,with high Ga value(18.2×10^(-6)-31.1×10^(-6))and Ga/Al>2.6.In addition,these granitoids haveΣREE of 77.67×10^(-6)-271.82×10^(-6),LREE/HREE of 2.82-16.26,(La/Yb)N of 1.80-21.89.Eu anomalies are obviously positive(δEu=0.16-0.84)for both Monzogranite and syenogranite but weakly negative or positive(δEu=0.85-1.20)for the quartz diorite.Monzogranite and syenogranite rather than quartz diorite experienced obvious crystalline fractionation of plagioclase.Monzogranite associated with syenogranite and quartz diorite was also subjected to fractional crystalization of zircon,while the independent one experienced separation of sphene and apatite.Zircon U-Pb dating of monzogranite yields crystallization ages of(273.3±1.9)Ma and(273.4±3.4)Ma.These geochemical features indicate that the primary magma of these A-type granitoids most likely originated from the Xingxingxia complex with minor mantle component,and underwent a fractional crystallization.There exist two distinguished ranges of 307-284 Ma and 273 Ma for A-type granitoids in the Tianshan Orogen,and the elder formed in partial extension environment during the compression period while the younger were emplaced in post-collision background.The eastern section of the southern CAOB had been in post-collision en

关 键 词：东天山 A型花岗岩 中亚造山带 中天山 星星峡 古亚洲洋 地球化学 岩石学. 

分 类 号：P581[天文地球—岩石学]