安徽董岭花岗岩类的构造特征及侵位机制

安徽怀宁董岭花岗岩类底辟滑覆构造体系是长江中下游地域独特的构造形式。花岗岩底辟构造是在中生代华北地块与扬子地块碰撞背景下通过气球膨胀机制侵位至盖层内(燕山期),形成了围绕董岭几何中心的环状或半环状接触变质和韧性变形岩块。该花岗岩类其内部变形明显,岩相分带、分期清晰,围岩顶盖保存完好,围岩变质均匀,变形强烈,滑覆断层发育,糜棱岩典型等为特征,是一个罕见的盖层中花岗岩类底辟构造。后期在其北侧和东侧被月山—白子山冲断岩块所超覆。

STRUCTURAL CHARACTERISTICS AND EMPLACEMENT MECHANISM OF GRANITOID IN DONGLING, ANHUI, CHINA

The structural pattern exposed in the middlelower Yangtze River Vally is regardedas the sliding structural system of granitoid diapir which is widely distributed in Dongling, Huailin county of Anhui Province.The colloskm orogen between the North China and the Yangtze Massives resulted in partial melting of rocks in the lower crust (during Indosinian Ts) and formed the Mesozoic melted magma. As a result, the folding was transformed into fructuring in the foreland belt with collision compression (Yanshanian J3-K1), and the extensional fractures propagated up to the upper crust rapidly and the melted magma ascended to emplacement in the cover near the surface with a "balloning mechanism" under lateral compression by the intrusion of the magma bodies, thereby forming circular and hemicircular terrains with contact metamorphism and ductile deformation around Dongling. It is called the sliding structural system of the granitoid diapir of Dongling.It is characterized by a complete diapiric roof cover, clear inner deformation lithizone and stages of magma bodies, homogeneous, high grade metamorphism and intensive deformation in the country rocks, and well-developed sliding fault and mylonites, being a rare granitoid diapir in the cover. In the later period of Yanshan (K2), the diapiric system has been overlaid by the thrust blocks of Yueshan-Baizishan in the north and east parts.