东秦岭地区“刘岭群”的重新划分

东秦岭地区原划为泥盆系的“刘岭群”被一条大型韧性推覆剪切带分为南北两个岩系,北部岩系为一套中浅变质的以杂砂岩为主,夹火山熔岩、火山碎屑岩和含陆缘砂碳酸盐岩的沉积-火山建造,其中紧闭、倒转、平卧褶皱和逆冲断层极为发育,沉积学特征及物源分析显示其为早古生代末-晚古生代初华北板块南缘活动大陆边缘沉积;南部岩系为一套由浅变质的粉砂岩、泥质岩、石英砂岩和碳酸盐岩组成的巨厚陆源碎屑沉积,发育东西向陡倾劈理及开阔对称褶皱组成的复式褶皱,沉积学特征和物源分析表明其为晚古生代初期扬子板块北缘沉积。“刘岭群”两岩系的岩性组合、沉积学特征、变质作用、构造变形期次、生物化石特征及形成的大地构造环境等方面的差异足以划分为不同的岩群,“刘岭群”应予解体。

THE REDIVISION OF LIULING GROUP IN EASTERN QINLING AREA OF CENTRAL CHINA

In eastern Qinling area, the Linting group can be divided into two lithological series by a large--scale ductile thrust shear zone of more than 100m wide and 200km long striking approximately E--W. North series is a sedimentary￣volcanic sequence,mainly composed of graywacke, volcanic lava, volcanic elastics and carbonitite which contains land-source sand, the metamorphic grade of which is low-middle. The closed, overturned and reclined folds and thrust faults are well developed. The sedimentary characteristics and provenance analysis indicates that it is the sedimentary rocks of the south active continental margin of North China plate from the last phase of early Paleozoic to the initial phase of late Paleozoic. South series is the ]and-source elastic sedimentary rocks with a great thickness, composed of low--grade metamorphic siltstone, polite, quartz sandstone and argillaceous carbonate with welldeveloped composite folds with steep dip axial planes, slaty cleavage and flow cleavage. The sedilnentrary characteristics and provenance analysis indicate that South Linting series formed in the north passive continental margin of Yangtze plate in the initial period of late Paleozoic. The two series have so many differences in rock formation, sedimemtary factes, metamorphism, deformation stage, fossil association and tectonic environment that they can be ascribed into two groups.