东秦岭-桐柏-大别山碰撞造山带北部早古生代变质火山岩系特征及其形成环境

东秦岭-桐柏-大别山碰撞造山带北部早古生代变质火山岩系具有与大洋拉斑玄武岩相似的岩石学、岩石化学及微量元素特征,与镁铁质、超镁铁质岩块、辉绿岩墙群以及变质的沉积岩断片共同构成蛇绿混杂岩带。它们原来形成在华北断块南部大陆边缘的早古生代边缘海盆地的洋壳上。这个边缘海盆地的产生与华南洋壳海域岩石圈断块在晚前寒武纪时期向北俯冲有关,是震旦纪古边缘海继续扩张的结果。在加里东末期到海西早期,扬子断块与华北断块发生碰撞,边缘海闭合。

THE CHARACTERISTICS OF THE METAVOLCANIC ROCK SERIES OF EARLY PALAEOZOIC ERA AND THE STRUCTURAL ENVIRONMENT OF THEIR GENESIS IN THE NORTHERN PART OF THE EAST QINLING-TONGBAI-DABIE COLLISION TYPE OROGENIC BELT

The primary rock of early Palaeozoic meta-volcanic rocks, which is located in the northern foot of the East Qinling-Tongbai-Dabie collision type orogenic belt, is oceanic tholeiite. After eruption, the lavas underwent regional metamorphism, so their petrological and mineralogical composition was changed. The characteristics of petrology, geochemistry and mineralogy show that they are similar to oceanic tholeiite. The meta-volcanic rocks, maficultramafic bodies, diabase dike groups and sedimentary rocks constitute the ophiolitic melange zone. The recta-volcanic rocks developed in a marginal-sea basin with oceanic crust at its base on south continental margin of North China Fault-Block. The formation of the marginal-sea basin would be related to the northward subduction of the lithospheric fault-block of South China with oceanic crustal sea areas at late pre-Cambrian and resulted from further extension of ancient marginal sea in the Sinian period. The marginal-sea basin was closed after collision between Yangze Fault-Block and North China Fault-Block at the end of Coledonian-early Hercynian orogeny.