幔壳运动及其成矿控矿作用——以小秦岭幔枝构造北矿带成矿控矿作用为例

Mantle-crust Movement and the Mineralization and Ore-controlling:A Study on Mineralization in the Northern Mantle-branch Structure Ore Belt of the Xiaoqinling Area

燕山运动中晚期,华北东部地区进入了以伸展构造为主的地幔热柱演化阶段,小秦岭矿集区形成了典型的幔枝构造体系。深源含矿流体通过地幔热柱—地幔亚柱—幔枝构造,迁移到幔枝构造有利构造部位集聚成矿。北矿带是小秦岭幔枝构造主要成矿区之一,进入燕山运动晚期,幔枝构造中断裂活动相当强烈,同时沿断裂形成了一系列大型—超大型金矿床,以及多金属矿床。在众多成矿控矿因素中,区域性断裂构造应是重要的主导性因素,它们不仅是成矿流体的运移通道,而且往往成为重要的成矿储矿有利空间。特别是近年来深部地质勘查发现,地表沿区域性主干断裂展布的若干个大中型金矿,在一定深度上其成矿蚀变构造带却是串连在一起的,整个沿断裂展布的若干个大—中型金矿统称为某某某超大型金矿。每个区域性深大断裂控制着一个超大型金矿带。其形成超大型金矿的过程可以概括为:强烈的岩浆—变质杂岩上涌(隆)→上部盖层向外拆离滑脱→幔枝构造逐渐形成→断裂构造体系由压扭性转变为张扭性→含矿流体沿断裂贯入→成矿物质冷却结晶→形成超大型金矿的模式。

In the middle and late period of Yanshan movement,the eastern part of North China entered the stage of mantle plume evolution dominated by extensional tectonics,and a typical mantle branch tectonic system was formed in the Xiaoqinling ore concentration area.The deep source ore-bearing fluid migrates through the mantle plume-sub mantle plume-mantle branch structure to the favorable structural position of the mantle branch structure to concentrate mineralization.The north ore belt is one of the main metallogenic areas of the Xiaoqinling mantle branch structure.In the late Yanshan movement,the mantle branch structure had a strong fracturing activity,and a series of large to super-large gold deposits and polymetallic deposits were formed along the fault.Among many ore forming and ore controlling factors,regional fault structure should be an important leading factor,which is not only the migration channel of ore-forming fluid but also an important favorable space for ore forming and ore storage.Especially in recent years,deep geological exploration has found that a number of large and medium-sized gold deposits distributed along the regional main fractures on the surface are connected in a certain depth with their metallogenic alteration structural belts.The whole number of large and medium-sized gold deposits distributed along the fractures are collectively referred to as a certain super-large gold deposit.Each regional deep fault controls a super large gold belt.The process of forming super large gold deposits can be summarized as follows:strong magmatic metamorphic complex upwelling(uplift) → upper cover detachment → gradual formation of mantle branch structure → fault structural system changing from compressional to tensional → ore-bearing fluid penetrating along the fault → cold crystallization of ore-forming materials → formation of super large gold deposits.