东北非努比亚地盾金矿成矿地质特征与找矿标志

Geological Characteristics and Prospecting Criteria of Gold deposits in Nubian Shield, NE Africa

东北非金矿的矿床类型、成矿条件与努比亚地盾演化密切相关。努比亚地盾金矿类型,按成因可分为两大类:一类是与造山带有关的韧性剪切带金矿,即造山型金矿;另一类是弧-弧拼合过程中形成的火山成因块状硫化物金矿,即VMS型铜-金矿。受韧性剪切带控制的造山型金矿形成于闭合-碰撞造山阶段,与弧-弧碰撞缝合带展布方向一致的北东向韧性剪切带为造山型金矿的主要控矿构造,该类型矿床规模以中小型为主。沿韧性剪切带成带分布的火山成因块状硫化物(VMS型)金矿床形成于洋壳俯冲-岛弧的形成阶段,其形成环境为岛弧裂谷或弧后裂谷环境,矿床规模以大型为主,成群分布于5个矿集区内。本文总结了该地区造山带型和VMS型金矿的主要特征,并依此提出在该地区寻找此两种类型金矿的找矿标志。

The types and metallogenic conditions of gold deposits in Northeast Africa are closely related to the evolution of the Nubian shield. Gold deposits in Nubian shield can be subdivided into two types according to their genesis: one is ductile shear zone gold deposits related to orogenic belts, i.e. orogenic gold deposits;the other is volcanic massive sulfide gold deposits formed during Arc-arc combination, i.e. VMS type copper-gold deposits. The orogenic gold deposits controlled by ductile shear zone were formed in the closed-collision orogenic stage. The NE-trending ductile shear zone, which is consistent with the distribution direction of Arc-arc collision suture zone, is the main ore-controlling structure of orogenic gold deposits. The scale of this type of gold deposits is mainly small and medium-sized. Volcanic massive sulphide type(VMS) gold deposits distributed along ductile shear zones were formed in the stage of oceanic crust subduction-island arc formation. They were formed in island-arc rift or back-arc rift environments. The deposits were mainly large-scale and distributed in clusters in five ore concentration areas. This paper summarizes the main characteristics of orogenic belt type and VMS type gold deposits in this area, and prospecting criteria for these two types of gold deposits are summarized as well.