山西五台山-恒山地区晚太古-早元古代若干关键地质问题的再认识:单颗粒锆石离子探针质谱年龄提出的地质制约

RECONSIDERATION OF SOME KEY GEOLOGICAL PROBLEMS OF LATE ARCHAEAN-EARLY PROTEROZOIC IN THE WUTAISHAN-HENGSHAN AREA:CONSTRAINTS FROM SHRIMP U-Pb ZIRCON DATA

大量准确度很高的单颗粒锆石迅谱 (SHRIMP)年代学数据表明 ,五台山 -恒山绿岩带形成于 2 50 0 Ma之前 ,五台山 -恒山绿岩带形成后即与较老的阜平块体拼合。因此 ,该过程中有大量火山 ,深成活动及变质作用 ,是一次重要的造山运动。在 1 80 0 Ma之前 ,本区还经历了一次明显的构造热事件 ,主要表现为在地壳较深水平上大规模的冲断作用 ,使原来为不同地壳水平的块体处于同一地壳水平。本文还对原五台群下部层位板峪口组和金岗库组的归属及铁堡不整合面提出了新的看法。

The new precise SHRIMP zircon dates obtained in this study indicate that the Wutaishan Hengshan greenstone belt formed at 2500 Ma ago, immediately after its formation the Wutaishan Hengshan greenstones had amalgamated with the older Fuping block. Therefore, there was intense tectonic, volcanic, plutonic, and metamorphic activities just before 2500 Ma, which was thought to be related to the major episode of plate tectonic activity in the area. There was also another obvious tectono thermal event at about 1800 Ma ago, during that time there was some big scale of thrusts occurred, along the thrusts some deep level of rock units was thrust up then juxtaposed with some high level of rock units. This paper has also stressed some key problems on the famous Tiebao unconformity and the stratigraphic division of the lower part of the Wutai Group, and presenting some new idea on both.