晋北地区中元古代岩墙群的地球化学特征和大地构造背景

Geochemical characteristics and tectonic setting of Mesoproterozoic dyke swarms in northern Shanxi.

晋北地区发育大规模的中元古代北北西向岩墙群 ,未变形和未变质 ,是华北克拉通前寒武纪构造演化研究的最显著标志。根据本区岩墙群的岩石学和地球化学研究 ,这些岩墙群的岩石属于板内大陆裂谷玄武岩系列 ,形成于大陆裂谷拉张的构造环境。与东侧的燕辽—中条拗拉槽内的火山岩岩石化学对比分析 ,本区岩墙群的基性岩浆可能来自拗拉槽深部。这些基性岩浆从拗拉槽的深部向北西方向侵位于晋北地区先存的构造裂隙中形成了基性岩墙群。

A lot of Mesoproterozoic mafic dyke swarms develop in northern Shanxi, which are undeformed and unmetamorphosed as conspicurious marks in Precambrian tectonic evolution of North China Craton. These mafic dyke swarms emplaced quickly and their temperature was very high, about 1100 similar to 1200 degreesC. Based on the study of petrology and geochemistry of mafic dykes in this area, the dykes were formed in intraplate continental rift environment which was an extensional continental aulacogen. Comparing the geochemical analysis between the mafic dykes and volcanic rocks in Yanliao-Zhongtiao aulacogens, the mafic magma of dyke swarms maybe came from the deep bottom of aulacogens. The mafic magma emplaced northwestward into the pre-existed fractures in northern Shanxi to form the mafic: dyke swarms from the deep bottom of aulacogens.