山西五台山区王家会岩体的地质特征及构造意义

The Geological Features and Tectonic Significances of the Wangjiahui Rock in Wutai Mountains,Shanxi

在野外地质调查的基础上,采集了王家会岩体的新鲜样品,运用年代学和岩石地球化学的方法,对其岩体形成时期五台地区构造作用特征进行了研究。研究认为,五台山北麓王家会花岗岩体的形成经历了两次岩浆活动,并非前人所认为的该岩体是一次岩浆作用的产物;单颗粒锆石U-Pb年龄数据分别为2 517~2 520Ma和2 117~2 129Ma,相差约400Ma,分别为新太古代和早元古代;两次岩浆活动的岩浆物质均来源于玄武质初生地壳部分熔融,新太古代晚期的奥长花岗岩和花岗闪长岩形成于恒山微陆块和阜平微陆块陆-陆碰撞挤压的岛弧环境,早元古代的二长花岗岩形成于碰撞后的伸展拉张构造背景。王家会岩体深部岩石＂探针＂作用的研究揭示了五台地区在新太古代发生微陆块挤压碰撞、壳融岩浆活动的构造-岩浆特点,同时也揭示了在早元古代五台地区处于伸展拉张的构造作用特征。

Based on the geological survey,Wangjiahui rock fresh samples were collected and the method of chronology and geochemistry were used to study the tectonic action features of Wutai regions for its rock formation period.Studies suggest that,Wangjiahui rock located north of Wutai Mountain experienced two magmatisms,not as thought as only one magmatism.The dating of single-grained zircon U-Pb is 2 517~2 520 Ma and 2 117~2 129 Ma,which differ about 400 Ma,and are Neoarchean and Paleoproterozoic,respectively.The twice magma substances are derived from partial melting of basaltic newborn crust.Trondhjemite and granodiorite in late Archean are formed in island arc setting formed by the continent-continent collision beween Hengshan micro-continental blocks and Fuping micro-continental blocks.Monzogranite in Paleoproterozoic is formed in extensional structures after collision.The research of Wangjiahui rock deep rock＂probe＂reveals the characteristics of the microcontinent collision and Crustal melting magmatism occurred in the Wutai in late Archean,as well as the extensional structures in Paleoproterozoic.