洪镇变质核杂岩及其成矿意义

位于长江中下游地洼区中的洪镇地区出露了变形变质的元古界结晶基底,并伴有主动侵位的燕山期花岗岩。在结晶基底与侏罗系至第三系基本没有变形变质的“稳定盖层”之间的“活动盖层”中可划分出三个滑脱剥离系,它们分别山元古界与寒武系、泥盆系与石炭系、中三叠统月山组与铜头尖组三个主剥离断层及其上盘相关的正断层系组成。本区包括变质杂岩核、基底剥离断层、“活动盖层”和“稳定盖层”的构造组合。具有不同于科迪勒拉型变质核杂岩的结构特征,称之为陆内伸展型变质核杂岩。它表现出上地幔隆升和中,上地壳多层次拆离、减薄,并控制了燕山期中酸性岩浆岩体的侵位方式和层状多金属矿床的分布、形态和成矿机理。

GEOLOGICAL CHARACTERISTICS AND METALLOGENIC SIGNIFICANCE OF HONGZHENG METAMORPHIC CORE COMPLEXES, ANHUI

Strongly deformed and metamorphosed crystalline basementwith initially intrusive Yenshan granites are exposed in Hongzheng, Anhui. In mobiling covering strata (∈-T) three sliding systems consisting of primarny detachment faults and secondary normal faults can be subdivided: one between Proterozoic crystalline rocks and the Cambrian, the second between the Devonian and the Carboniferous, and the third between the Yenshan group (T_(my)) and the Tongtoujian group (T_(ma)). The tectonic style (assemblage of core, basement detachment faults, deformed covering strata and final nondeformed covering strata) which differs from typical Cordillera type metamorphic core complexes in geometry is called an intracontinent extension type. This state was caused by the upwelling of upper mantle, multilayer denudation, and thinning of the middle—upper crust. Overall, the Hongzheng metamorphic core complexes controlled the emplacement of magmatite and the mineralization of the accompanying stratiform ore deposits.