甘肃北山晚古生代基性岩墙群岩石成因及其构造意义  

Petrogenesis and Tectonic Significances of the Late Paleozoic Mafic Dykes in the Beishan Area in Gansu Province

作　　者：彭仁 张贵山[1,2] 邱红信 刘涛涛 樊新祥 赵吉昌 PENG Ren;ZHANG Gui-shan;QIU Hong-xin;LIU Tao-tao;FAN Xin-xiang;ZHAO Ji-chang(School of Earth Science and Resources,Chang’an University,Xi’an 710065,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,Ministry of Natural Resources,Xi’an 710065,China;Fourth Institute of Geological and Mineral Exploration of Gansu Provincial Bureau of Geology and Mineral Resources,Jiuquan Gansu 735000,China)

机构地区：[1]长安大学地球科学与资源学院,西安710065 [2]自然资源部岩浆作用成矿与找矿重点实验室,西安710065 [3]甘肃省地质矿产勘查开发局第四地质矿产勘查院,甘肃酒泉735000

出　　处：《矿物岩石地球化学通报》2020年第2期254-266,共13页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(41073027);中央高校基本科研业务费专项资金资助项目(310827172003);陕西省自然科学基础研究计划项目(2019JM-161)。

摘　　要：为探讨甘肃北山地区晚古生代基性岩墙群的岩石成因及其构造意义,对该岩墙群岩石进行了锆石U-Pb年龄测定和全岩地球化学分析。结果显示,辉绿岩中锆石U-Pb加权平均年龄为(285±4) Ma,属早二叠世;岩石富集轻稀土元素和大离子亲石元素(Rb、U、K、Pb),亏损高场强元素(Nb、Ta)。岩石成因分析表明,基性岩墙的岩浆源区为俯冲流体交代的岩石圈地幔,主要为含金云母尖晶石二辉橄榄岩,岩浆在运移和上升侵位过程中未受到明显的地壳混染作用。结合大地构造环境判别和区域研究资料认为,甘肃北山地区晚古生代基性岩墙群形成于板内伸展环境,本区域古洋盆于早泥盆世之前闭合。二叠纪岩浆活动带有俯冲消减信号表明,早期俯冲流体对岩石圈的交代作用仍制约着岩浆的地球化学特征。In order to probe the petrogenesis and tectonic significances of mafic dykes in the Beishan area in Gansu Province, petrogeochemical and LA-ICP-MS zircon U-Pb geochronological studies of the mafic dykes have been carried out in this paper. LA-ICP-MS U-Pb zircon analysis yield an age of(285±4) Ma for diabase, indicating its emplacement in Early Permian. The samples are rich in LREE and LILEs(Rb, U, K, Pb) and poor in HFSEs(Nb, Ta). The analysis of petrogenesis suggests that the mafic dykes could be derived from lithospheric mantle source, metasomatized by subduction-related fluid, which was mainly composed of the phlogpite and spinel-bearing lherzolite, and was not apparently contaminated by crustal materials during the magma migration, rising and emplacement. Combined with the related tectonic setting discrimination and regional research data, it is believed that the Late Paleozoic mafic dykes in the Beishan area were emplaced in an intraplate extensional setting and the ancient ocean basin of the area was closed earlier than the Early Devonian. The Permian magmatism has a subduction signal, indicating that the metasomation of early subduction fluids on the lithosphere still had constraint on geochemical characteristics of the magma.

关 键 词：甘肃北山 基性岩墙 地质年代学 地球化学 构造环境 

分 类 号：P588.124[天文地球—岩石学]