阿尔泰造山带北段晚三叠世早期岩浆作用成因及其对构造体制转换的制约  

Petrogenesis and tectonic significance of the early Late Triassic magmatism of the northern Altaid orogenic belt

作　　者：赵端昌 蔺新望 陈宁 王星 张亚峰 郭岐明 ZHAO Duanchang;LIN Xinwang;CHEN Ning;WANG Xing;ZHANG Yafeng;GUO Qiming(Shaanxi Institute of Geological Survey,Xi’an 710068,Shaanxi,China;Shaanxi Mineral Resources and Geological Survey,Xi’an 710068,Shaanxi,China;Shaanxi Satellite Application Technology Center for Natural Resource,Xi’an 710068,Shaanxi,China)

机构地区：[1]陕西省地质调查院,陕西西安710068 [2]陕西省矿产地质调查中心,陕西西安710068 [3]自然资源陕西省卫星应用技术中心,陕西西安710068

出　　处：《地质通报》2022年第9期1563-1573,共11页Geological Bulletin of China

基　　金：新疆地勘基金中心项目《新疆富蕴县阿拉一带1:5万L45E003023、L45E003024、L45E004023、L45E004024、L46E004001五幅区域地质调查》(编号:A16-1-LQ01);陕西省地质调查规划研究中心(陕西省地质勘查基金中心)项目《陕西小秦岭成矿带石坡地区基础地质调查》(编号:61202110379)、《陕西省南秦岭成矿带佛坪隆起南缘茅坪地区基础地质调查》(编号:202102)。

摘　　要：对阿尔泰造山带北段南缘出露的塔尔萨依岩体二云母正长花岗岩进行了LA-ICP-MS锆石U-Pb定年,获得其^(206)Pb/^(238)U年龄加权平均值为235±2 Ma(MSWD=0.46),表明该花岗岩为晚三叠世早期岩浆活动的产物。全岩地球化学分析结果显示,塔尔萨依岩体的二云母正长花岗岩和二云母二长花岗岩均具有高硅、高钾、低镁、低钛特征,里特曼指数(σ)和铝饱和指数(A/CNK)分别大于2和1.1,为高钾钙碱性强过铝质花岗岩。此外,两类花岗岩均富集轻稀土元素和Rb、Th等微量元素,亏损高场强元素Nb、Ta、Yb和Y。其低的Mg#值、Cr和Ni含量,以及中等的CaO/Na_(2)O和低的Al_(2)O_(3)/TiO_(2)值,表明研究区花岗岩形成于同碰撞构造环境。结合前人已有研究成果,认为阿尔泰造山带三叠纪的构造体制转变在时空上存在差异,整体表现出东—中段由挤压环境进入伸展构造背景的时间较北部早的趋势。LA-ICP-MS zircon U-Pb dating for the two-mica syenogranite of Talsayi pluton in the southern margin of the northern Altaid orogenic belt yielded a ^(206)Pb/^(238)U age of 235±2 Ma(MSWD=0.46),which interpreted as product of the early Late-Triassic magmatic event.Whole-rock geochemical data show that two-mica syenogranite and two-mica monzogranite of the Talsayi pluton are characterized by high silicon and alkali,low titanium and magnesium,as well as large Rittmann Index and Aluminum Saturation Index(A/CNK)values.The lines of evidence indicate that the granitic rocks are classified into high potassium calc-alkaline peraluminous granitic series.In addition,the syenogranite and monzogranite are relatively enriched in light rare earth elements(LREE),as well as trace elements of Rb and Th,but depleted in high field-strength elements of Nb,Ta,Yb and Y,in addition,the granitic rocks show low values of magnesium and contents of Cr and Ni,and moderate values of CaO/Na_(2)O and low values of Al_(2)O_(3)/TiO_(2).These suggest that the Talsayi pluton in the southern margin of the northern Altaid orogenic belt were formed in the syn-collision tectonic environment.Combination with the previous studies,it is proposed that the transition of tectonic regime of the Altaid orogenic belt show spatiotemporal difference with characteristic of trending from east and central to north direction during Triassic era.

关 键 词：阿尔泰造山带北段 同碰撞构造环境 晚三叠世 强过铝质花岗岩 构造体制转变 

分 类 号：P534.51[天文地球—古生物学与地层学] P588.1[天文地球—地质学]