冕山地区基性岩墙年代学及地球化学特征  

Geochronology and Geochemistry of Basic Dykes in the Mianshan Region

作　　者：文龙[1] 朱兵[1] 鄢圣武[1] 白宪洲[1] 李名则[1] WEN Long;ZHU Bing;YAN Sheng-wu;BAI Xian-zhou;LI Ming-ze(Sichuan Institute of Geological Survey,Chengdu610081)

机构地区：[1]四川省地质调查院,成都610081

出　　处：《四川地质学报》2017年第4期535-541,共7页Acta Geologica Sichuan

基　　金：中国地质调查局龙门山-滇中成矿带通安和宁蒗地区地质矿产调查(编号:121201010000150016)

摘　　要：扬子西缘冕山地区发育大量基性岩墙,高精度LA-ICP-MS锆石U-Pb年代学研究表明,其侵位结晶于787~791Ma,属新元古代青白口纪岩浆活动产物。岩石地球化学研究表明,基性岩墙主量元素岩石具有高硅、高碱、富铁、低镁、偏铝质的特点,显示出拉斑玄武岩的特征。综合元素地球化学特征及构造环境判别研究表明,冕山地区基性岩墙形成于板内构造环境,是大陆地壳拉张、岩石圈减薄机制下上涌的软流圈地幔岩浆经历了不同程度的分离结晶和地壳部分混染作用而侵位的产物。Many diabase dykes are exposed in Mianshan area on the west margin of the Yangtze Block.Their zircon U-Pb dating shows that they were emplaced during787-791Ma which indicates that they may be considered as products of magmatism during Neoproterozoic Qingbaikou period.Petrogeochemistry of the dykes is characterized by enrichment in Si,Al,Fe,Th,La and Ce and depletion in Mg,Ta,Nb which is characteristic of tholeiite.The REE geochemistry is characterized by∑REE of46.86-128.44ppm with(La/Yb)N of1.62-4.07andδEu values of0.83-1.02which is similar to that of island arc basalt.These show that the dykes were derived from the asthenosphere mantle and emplaced in within-plate environment with partial crustal contamination under condition of continental crust extension and lithosphere thinning.

关 键 词：基性岩墙 锆石U-PB年代学 地球化学 冕山地区 

分 类 号：P584[天文地球—岩石学]