大别山的变质碰撞混杂岩——以东部为例

大别山是中国东部中朝大陆板块与扬子大陆板块之间的碰撞造山带。具有薄皮构造的性质。组成两个碰撞大陆之间的滑脱（冲断剪切）带的岩石就是碰撞混杂岩组合。大别山由于剥露较深,仰冲壳楔完全被剥蚀,超高压变质带大面积出露,识别出碰撞混杂岩组合是对大别山进行几何分析的必要步骤。大别山碰撞混杂岩组合可分为南北两部分。北部为条带状片麻岩-超镁铁岩组合,南部为云母斜长片麻岩-榴辉岩组合,这两个组合的大部分都经历过超高压变质作用。它们的共同特点是具有宏观的＂碎斑结构＂和混杂作用。罗田穹隆是造山过程中早期形成的双冲式背斜,最后在造山晚期因东西向缩短的叠加而形成穹隆。

METAMORPHIC COLLISIONAL M LANGE IN THE DABIE MOUNTAINS, EASTERN CHINA

The Dabie Mountains are a collisional orogen between Sino-Korean and Yangtze continents. It is characterized by thin-skin tectonics as revealed by the seismic reflection profile. The rocks forming a detachment （thrust shear） zone between the two collisional continents are collisional melanges. The detachment can only be defined by recognizing collisional melanges in the Dabie Mountains because the overriding wedge has been belt exposed extensively. completely removed by This is a necessary erosion and the ultrahigh-pressure （UHP） metamorphic step to perform a geometric analysis of the Dabie Mountains. The Dabie collisional melanges may be divided into two parts： the northern part consists of a banded gneiss-uhramafic rock assemblage and the southern part a mica plagiogneiss-eclogite assemblage. Both assemblages have mostly undergone UHP metamorphism. Their common features are the presence of ＂giant mortar texture＂ due to pervasive shearing and mixing of rocks from various tectonic settings. The so-called ＂Luotian dome＂ was a huge duplex anticline formed in the early stage of orogeny, which finally formed a dome formed by superimposed contraction in an east-west direction in the late stage of the orogeny.