敦煌地块南缘晚三叠世花岗岩成岩时代与地质意义  

DIAGENETIC AGE OF LATE TRIASSIC GRANITE IN THE SOUTHERN MARGIN OF DUNHUANG BLOCK AND GEOLOGICAL SIGNIFICANCE

作　　者：路鹏飞 王玉玺[1] 张渊[1] 马国杰[1] 尤泽华 张兵兵[1] LU Peng-fei;WANG Yu-xi;ZHANG Yuan;MA Guo-jie;YOU Ze-hua;ZHANG Bing-bing(Geological Survey of Gansu Province,Lanzhou 730000,China)

机构地区：[1]甘肃省地质调查院,甘肃兰州730000

出　　处：《甘肃地质》2019年第3期18-25,共8页Gansu Geology

基　　金：甘肃省地质勘查基金项目“甘肃省阿克塞县多坝沟金多金属矿普查”(20151306);中国地质调查局地质调查项目“甘肃矿产资源国情调查前期准备(KD-[2019]-XZ-126)”。

摘　　要：敦煌地块处于一个特殊的大地构造位置,北接北山造山带,西北部接天山造山带,西南部接阿尔金造山带,东南部以阿尔金断裂与祁连造山带相隔。本文重点研究敦煌地块南缘克孜勒塔格二长花岗岩,在对岩体野外调查的基础上,结合锆石TIMS法U-Pb年龄测定结果,厘定了敦煌地块南缘相关岩石的形成时代。花岗岩成岩年龄和岩石地球化学研究显示,岩石具有高硅(SiO2=69.73%~76.40%)、贫镁(MgO=0.22%~0.48%,Mg#=38~40)的特征,A/NKC比值介于0.98~1.01,A/NK比值介于1.17~1.68,表明岩石为高钾钙准铝质二长花岗岩,属于I型花岗岩。克孜勒塔格二长花岗岩的热电离质谱法(TIMS)锆石U-Pb年龄为(216.2±0.4 Ma),表明其形成时代为晚三叠世。Sr-Nd同位素分析表明花岗岩可能为上地幔部分熔融形成的原始岩浆与地壳物质之间发生混合作用的产物,形成于晚三叠世碰撞造山阶段。Dunhuang block is located in a special geotectonic location,north of the Beishan orogenic belt,northwest of the Tianshan orogenic belt,southwest of the Aljin orogenic belt,southeast of the Aljin fault and Qilian orogenic belt separated.This paper focuses on the study of the Keziletag monzonitic granite on the southern margin of the Dunhuang massif.Based on the field investigation of the rock mass,the formation age of related rocks on the southern margin of the Dunhuang massif was determined based on the zircon TIMS U-Pb dating results.According to the study of diagenetic age of granite and petrogeochemistry,the rocks have high silicon(SiO2=69.73%~76.40%)and low magnesium(MgO=0.22%~0.48%,Mg#=38~40),A/NKC ratio is 0.98~1.01 and A/NK ratio is 1.17~1.68 in the rock,the rock mass,belongs to type I granite,is high potassium calc-alkaline quasi-aluminous monzonitic granite.The age of thermal ionization mass spectrometry(TIMS)U-Pb zircon of Kiziletag monzonitic granite is 216.2±0.4 Ma,that is late Triassic.Sr-Nd isotope analysis indicates that granite may be the product of mixing between the original magma formed by partial melting of upper mantle and crustal materials,which formed in the Late Triassic collision orogenic stage.

关 键 词：地球化学 二长花岗岩 晚三叠世 敦煌地块 克孜勒塔格 

分 类 号：P588.121[天文地球—岩石学]