安徽大别山蛇绿岩特征及其形成的大地构造环境

在安徽境内大别群中出露一系列镁铁质和超镁铁质岩体,属于“肢解的蛇绿岩”。与大别群建造应属同一造山期产物。它们可能在中元古代末期,因洋壳海域的岩石圈断块沿华北断块南部的大陆边缘的深海沟向北快速俯冲消减,遭到强烈挤压破碎而侵位到大别群不同构造层位中。

CHARACTERISTICS AND GEOTECTONIC ENVIRONMENT OF THE OPHIOLIT IN THE DABIE MOUNTAIN, ANHUI PROVINCE

Basic and uitrabasic rocks in the Dabie Group are exposed in the north of Dabie Mountain old fault-block uplift, Anhui Province. Lots of evidence show these basic and uitrabasic bodies were ophiolites, the relict fragments of oceanic crust. They evolved with the Dabie Group through one and the same orogenic movement.Because the ophiolitic bodies in this area had undergone intense structural deformation and metamorphism and later, extensive regipnal migmatization and lost their original features,it is very difficult to recove their original sequence. According to the present knowledge, the ophiolites can be clearly divided into the basal ultramafic complex and the mafic and ultramafic cumulates. The ophiolitic bodies are small, however, their numbers are great. They occur in the form of lens and are "the dismembered oghiolites".The ophiolitic zone is situated on the southern side of the Mozitan-Tongchen Deep-Seated Fracture deviding the Jinzhai-Huoshan Fault-Depression from the old fault-block uplift of the Dabie Mountain and extends nearly northwest-southeast in accordance with the regional tectonic lineament(schistosity) .The petrological and petrochemical features as well as the textural and structural characteristics of the ophiolitic bodies indicate that they are quite alike to the Alpine or the YaluZangbu ophiolites.Owing to the northward quick subduction of the oceanic lithosphere across the deep trench situated on: the southern margin of the North China Fault Block, the ophiolites were intensely compressed, crumbled aad emplaced onto different positions of the Dabie Group by the end of Middle Proterozoic.