巴颜喀拉地块当俄花岗岩体地球化学特征及锆石年龄  

Geochemical characteristics and zircon dating of Dang’e granites in the Bayanhar terrain

作　　者：邓金贤 冯平[1] 周云龙 彭健 齐兵德 邓良武 沙浩 DENG Jinxian;FENG Ping;ZHOU Yunlong;PENG Jian;QI Bingde;DENG Liangwu;SHA Hao(Brigade 283 of the nuclear industry geological survey in Sichuan province, Dazhou 635000, Sichuan, China)

机构地区：[1]四川省核工业地质局二八三大队

出　　处：《地质找矿论丛》2019年第2期242-248,共7页Contributions to Geology and Mineral Resources Research

基　　金：中国地质调查局项目(编号:121201011000150005-10)资助

摘　　要：巴颜喀拉地块夹持于昆南缝合带、金沙江缝合带及龙门山断裂带之间,出露了较多的花岗岩体。当俄花岗岩体的岩石地球化学特征表明,当俄岩体具有较高SiO2含量(w(SiO2)=65.78%~70.22%)、过铝质(A/CNK=1.58~1.95,>1.1)特征,属过铝质高钾钙碱性A型花岗岩;该岩体总体形成温度为700℃—800℃,总体形成压力为0.05GPa—0.2GPa,为低压高温环境;岩石具有Rb、Th强正异常,Ba、Nb、Sr、P、Ti强烈亏损,轻稀土强烈富集特征,且具有一定的负Eu异常,显示出有壳源的特征;花岗岩锆石SHRIMPU-Pb测年为211.9Ma±1.9Ma,表明岩浆侵位时代为中生代晚三叠世。当俄花岗岩体形成于碰撞造山后期地壳减薄环境中,属于印支晚期岩浆活动的产物。Bayanhar terrain is held by the Southern Kunlun suture and Jinshajiang suture and Longmenshan fault.There are many granite outcrops in the terrain and Dang’e granite body is one of them.Geochemical analysis shows that Dang’e granite body is characterized by higher SiO 2 contents(65.78%to 70.22%)and peraluminous(A/CNK=1.58 to 1.95>1.1)belonging to the peraluminous-high K calc-alkaline A-type granites.It is formed under the low pressure(0.05 GPa-0.2 GPa)and high temperature(700℃-800℃)environment with strong Rb,Th positive anomaly,strong Ba,Nb,Sr,P,Ti depletion,strong LREE enrichment and a certain negative Eu anomly.All this are the characteristic of the crustal source.The zircon SHRIMP U-Pb dating(211.9 Ma±1.9 Ma)indicates that emplacement age of the granite body is the Mesozoic Late Triassic Epoch.It is formed during the crust thinning of late to post orogenic collision,and is the product of late Indo-China magmatic activity.

关 键 词：巴颜喀拉地块 A型花岗岩 地球化学 SHRIMP锆石U-PB测年 碰撞造山后期 青海省 

分 类 号：P588.1[天文地球—岩石学]