甘肃北山草湖岩体二叠纪石英闪长岩地球化学、年代学及其地质意义  

Geochemistry,geochronology and geological implications of Permian quartz diorite from Caohu pluton in Beishan,Gansu

作　　者：赵海波 张倩 王红杰[2,3] 程龙 王鹏 ZHAO Haibo;ZHANG Qian;WANG Hongjie;CHENG Long;WANG Peng(Xining Center of Natural Resources Comprehensive Survey,CGS,Xining 810000,Qinghai,China;Zhengzhou Institute of Multipurpose Utilization of Mineral Resources,CAGS,Zhengzhou 450006,Henan,China;High Purity Quartz Resource Develop-ment and Utilization Engineering Technology Innovation Center,Ministry of Natural Resources,Zhengzhou 450006,Henan,China;Regional Geological Survey Academe of Shaanxi Geology and Mining Group Co.,Ltd.,Xianyang 712000,Shaanxi,China)

机构地区：[1]中国地质调查局西宁自然资源综合调查中心,青海西宁810000 [2]中国地质科学院郑州矿产综合利用研究所,河南郑州450006 [3]自然资源部高纯石英资源开发利用工程技术创新中心,河南郑州450006 [4]陕西地矿区研院有限公司,陕西咸阳712000

出　　处：《矿产勘查》2024年第8期1379-1390,共12页Mineral Exploration

基　　金：中国地质调查局项目(DD20242767、DD20190186、DD20221698);国家自然科学基金项目(42062006)联合资助。

摘　　要：北山地区在晚古生代—早中生代经历了碰撞造山作用,但前人对各时期构造环境归属存在不同认识,特别是北山地区何时由挤压环境进入伸展环境这一科学问题存在争议。北山草湖地区广泛发育的晚古生代侵入岩,为探讨该问题提供了研究机遇。LA-ICP-MS锆石U-Pb定年结果表明,石英闪长岩体的形成年龄为(276.3±3.0)Ma,为早二叠世晚期。岩石铝饱和指数(A/CNK值)小于1.05,具有准铝质、钙碱性特征,岩石富集轻稀土和大离子亲石元素(如Rb、Ba、Th和U),亏损高场强元素(如Nb和Ta),属于科迪勒拉I型花岗岩,岩浆可能来自后碰撞伸展环境下,岩石圈地幔岩浆作用导致增厚的敦煌地块北缘下地壳岩石部分熔融,并在上升过程中混染了下地壳物质所形成的壳幔混合成因的花岗岩,代表了北山地区南部在早二叠世晚期已处于伸展环境,为进一步约束北山地区古亚洲洋最终闭合提供依据。The Beishan region underwent collisional orogenesis during the Late Palaeozoic to Early Mesozoic,but previous scholars have held different views on the attribution of tectonic environments during these different geological periods.In particular,there is a contentious scientific debate about the precise timing of the transition from a compressional to an extensional environment in the Beishan region.The extensive development of Late Palaeozoic intrusive rocks in the Caohu area of the Beishan provides a research opportunity to explore this ques⁃tion.The LA-ICP-MS zircon U-Pb dating results indicate that the quartz diorite body was formed at(276.3±3.0)Ma,during late Early Permian.The rocks have an aluminium saturation index(A/CNK value)of less than 1.05,are quasi-aluminous and calc-alkaline in character,are enriched in light rare earths and large ionic lithophile ele⁃ments(e.g.Rb,Ba,Th and U)and deficient in high field strength elements(e.g.Nb and Ta),and are Cordil⁃lera I-type granites with magmas probably derived from a post-collisional extensional environment where lithospheric mantle magmatism led to thickening of the lower crust of the northern margin of the Dunhuang Massif.The granites are of mixed crustal-mantle origin and represent a late Early Permian extensional environment in the southern part of the Beishan area,where the magmas were partially melted and mixed with lower crustal material during uplift,providing a basis for further constraints on the eventual closure of the Palaeo-Asian Ocean in the Northern Mountains region.

关 键 词：石英闪长岩 I型花岗岩 后碰撞 甘肃北山 

分 类 号：P581[天文地球—岩石学]