大兴安岭甘南地区花岗岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及其地质意义  

LA-ICP-MS ZIRCON U-Pb DATING AND GEOCHEMISTRY OF THE GRANITES IN GANNAN AREA,DAXINGANLING MOUNTAINS:Geological Implication

作　　者：李晓海[1] 张海华[1] 李文博[1] 丁秋红[1] 张健[1] 陈树旺[1] LI Xiao-hai;ZHANG Hai-hua;LI Wen-bo;DING Qiu-hong;ZHANG Jian;CHEN Shu-wang(Shenyang Center of China Geological Survey,Shenyang 110034,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034

出　　处：《地质与资源》2023年第6期655-663,共9页Geology and Resources

基　　金：中国地质调查局项目“松辽盆地北部及外围石炭-二叠系油气地质调查”(DD20190097);“东北地区重要盆地多能源资源地质调查”(DD20221664).

摘　　要：通过对大兴安岭中北段甘南地区黑甘地1井钻遇的二云二长花岗岩进行LA-ICP-MS锆石U-Pb年代学和岩石地球化学研究,确定其形成时代、岩石成因,从而揭示区域构造背景.花岗岩的锆石呈半自形—自形,振荡生长环带明显.测年结果显示,二云二长花岗岩形成于161 Ma,为晚侏罗世早期岩浆事件的产物.地球化学分析结果显示,岩石具有高硅(SiO_(2)69.81%~74.3%)、富铝(Al_(2)O_(3)13.5%~16.8%)、贫铁(Fe_(2)O_(3)0.26%~0.6%)等特征,在化学成分上属于准铝质-弱过铝质系列.富集大离子亲石元素Rb、Ba、K和高场强元素Hf,贫Nb、Ta、Ti等高场强元素;相对富集轻稀土元素,亏损重稀土元素,为I型花岗岩.岩浆起源于新增生加厚陆壳物质的部分熔融.研究结果表明晚侏罗世早期二云二长花岗岩的形成与蒙古-鄂霍次克缝合带闭合过程中的陆-陆碰撞环境有关,其形成时代限定了蒙古-鄂霍次克洋在大兴安岭中北段甘南地区的闭合时代为晚侏罗世早期.The formation age and petrogenesis of the two-mica monzogranite drilled from HGD-1 well in Gannan area of central-northern Daxinganling Mountains are determined and the regional tectonic setting is revealed on the basis of LA-ICP-MS zircon U-Pb chronology and petrogeochemistry studies.The zircons in granite are subidiomorphic-idiomorphic,with obvious oscillatory growth zone.The dating results show that the two-mica monzogranite was formed at 161 Ma,which is the product of magmatic event in early Late Jurassic.Geochemical analysis results indicate that the granite is characterized by high Si(SiO_(2)69.81%-74.3%),rich Al(Al_(2)O_(3)13.5%-16.8%),and poor Fe(Fe_(2)O_(3)0.26%-0.6%),belonging to quasi aluminous-weak peraluminous series in terms of chemical composition,with enriched LILEs(Rb,Ba and K)and HFSE(Hf),and depleted HFSEs(Nb,Ta and Ti),and relatively enriched LREEs and depleted HREEs,which is of I-type granite.The magma originates from the partial melting of newly thickened continental crust material.The study results reveal that the formation of the early Late Jurassic two-mica monzogranite is related to the continent-continent collision environment during the closure progress of Mongol-Okhotsk suture zone,and its formation age restricts the closing time of Mongol-Okhotsk Ocean to the early Late Jurassic in Gannan area of central-northern Daxinganling Mountains.

关 键 词：晚侏罗世 二云二长花岗岩 锆石U-PB年龄 地球化学特征 蒙古-鄂霍次克洋 大兴安岭 

分 类 号：P597[天文地球—地球化学]