东昆仑沟里地区早古生代花岗岩的岩石成因与地质意义:来自U-Pb年代学和岩石地球化学的约束  

PETROGENESIS AND GEOLOGICAL IMPLICATIONS OF EARLY PALEOZOIC GOULI GRANITE IN EAST KUNLUN:CONSTRAINTS FROM U-Pb GEOCHRONOLOGY AND PETROGEOCHEMISTRY

作　　者：刘忠媛 闫东东 赵涵[1,2] 龚婷婷[1,2] 熊富浩[1,3] Liu Zhongyuan;Yan Dongdong;Zhao Han;Gong Tingting;Xiong Fuhao(College of Earth Science,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation of Ministry of Natural Resources,Chengdu,Sichuan 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]成都理工大学,自然资源部构造成矿成藏重点实验室,四川成都610059 [3]成都理工大学,油气藏地质及开发工程国家重点实验室,四川成都610059

出　　处：《矿物岩石》2022年第3期7-19,共13页Mineralogy and Petrology

基　　金：国家自然科学基金(项目批准号:41602049);成都理工大学珠峰科学研究计划(项目编号:2021ZF11412)。

摘　　要：东昆仑造山带早古生代花岗岩记录了原特提斯造山作用过程,是反演区域构造演化的重要岩石探针。本次研究以东昆仑沟里地区花岗岩为研究对象,对其开展岩石成因和构造背景的研究。LA-ICP-MS锆石U-Pb年代学研究揭示沟里地区花岗岩的结晶年龄为424.7±2Ma,形成于晚志留世。岩石具有高SiO_(2)(65.33%~75.35%)、Al_(2)O_(3)(12.4%~16.57%)、全碱含量(Na_(2)O+K_(2)O:6.58%~8.58%)及FeOT(1.43%~4.45%)的特征,其Mg#值为15.33~29.00,A/CNK值为0.97~1.00,属于高钾钙碱性准铝质岩石。岩石具有较高的稀土总量(ΣREE=335.0×10^(-6)~432.3×10^(-6)),富集轻稀土且具有明显的Eu负异常(δEu=0.07~0.77)。岩石具有较高的10000*Ga/Al值(3.07~3.62)、高场强元素含量(Zr+Nb+Ce+Y=400×10^(-6)~606×10^(-6))和锆石饱和温度(800~857℃),属于典型的A型花岗岩。岩石具有轻微富集的Sr-Nd同位素组成((^(87)Sr/^(86)Sr)_(i)=0.711755~0.835342,ε_(Nd)(t)=-2.4~-4.3),且岩石具低Ce/Pb(0.19~7.72)、Nb/U(2.92~7.79)和Sm/Nd比值(0.51~1.04),表明岩浆起源于上地壳的部分熔融。综合研究表明,沟里地区晚志留世花岗岩属于A2型花岗岩,指示东昆仑造山带东段和西段经历了同步的原特提斯域造山作用过程,均于晚志留世进入了碰撞后伸展阶段。In this paper,the petrogenesis and tectonic setting of the Early Paleozoic granites in the Gouli area of east Kunlun are studied to reveal the magmatic activity during the proto-Tethyan orogeny and unravel the tectonic evolution of the area.LA-ICP-MS zircon U-Pb geochronology reveals that the granite in Gouli area has a crystallization age of 424.7±2.0Ma and was formed in the Late Silurian.Geochemical analysis shows that the Gouli granite has high contents of SiO_(2)(65.33%-75.35%),Al_(2)O_(3)(12.4%-16.57%),total alkali(Na_(2)O+K_(2)O:6.58%-8.58%)and FeO^(T)(1.43%-4.45%).Mg^(#) values of the granite range from 15.33to 29.00,and the A/CNK values range from 0.97to 1.00.The rocks have highΣREE(335.0×10^(-6)-432.3×10^(-6)),rich in LREE,with obvious negative Eu anomaly(δEu=0.07-0.77).The high 10000*Ga/Al value(3.07-3.62),high field strength element(Zr+Nb+Ce+Y)content in the range of 400×10^(-6)-606×10^(-6),and zircon saturation temperature in the range of 800-857℃indicate that the Gouli granite belongs to typical A-type granites.The slightly enriched Sr-Nd isotopic composition((^(87)Sr/^(86)Sr)_(i)=0.711755-0.835342,ε_(Nd)(t)=-2.4to-4.3),low ratios of Ce/Pb(0.19-7.72),Nb/U(2.92-7.79)and Sm/Nd(0.51-1.04),indicate that the magma was originated from partial melting of the upper crust.It is proposed that the late Silurian granites in Gouli area belong to A2type granites,and the eastern and western parts of the East Kunlun orogenic belt underwent the synchronous proto-Tethyan orogenic process and entered the post-collision extension stage in the late Silurian.

关 键 词：A型花岗岩 晚志留世 碰撞后伸展 原特提斯 东昆仑 

分 类 号：P581[天文地球—岩石学] P588.12.1[天文地球—地质学]