非洲中部新元古代Lufilian弧地区地质特征、成矿时代及构造演化历史

研究非洲中部新元古代Lufilian弧的地质矿产特征和构造演化历史,对深入了解前寒武纪地壳演化和成矿作用具有重要的意义。本文在系统收集Lufilian弧内地层、岩浆岩、变质、变形和成矿作用的基础上,对该带的构造演化历史进行了总结概括。研究表明:Lufilian弧基底为一条古元古代弧岩浆作用带,约880 Ma,Lufilian弧开始了早期的陆内裂谷作用,发育恩昌加花岗岩和早期基性岩浆作用,并沉积有罗安群地层。约765 Ma,裂谷作用演化至原始大洋裂谷阶段,罗安群沉积结束并开始沉积恩古巴群早期地层,在成岩期热液流体作用下形成了同沉积阶段铜钴、铀和铅锌矿化作用。至660 Ma左右,开始了早期的洋壳俯冲作用,并沉积有恩古巴群晚期碎屑地层。550 Ma左右,卡拉哈里克拉通与刚果克拉通发生陆-陆碰撞作用,在530 Ma左右,碰撞作用达到高峰阶段,而后期高温变质叠加作用持续到520 Ma左右,挤压作用晚阶段可能受莫桑比克洋闭合阶段近东西向远场挤压应力的影响,板块发生幕式折返作用,形成Hook岩基。约520～470 Ma,为变质岩石抬升冷却阶段。在同构造和构造后期,在变质热液流体作用下,早期矿物再次活化,在构造有利部位形成矿体。

Geological characteristics, tectonic evolution and metallogenic ages of the Neoproterozoic Lufilian arc in central Africa

This paper studies the geological characteristics and tectonic evolution of the Neoproterozoic Lufilian Arc in central Africa, focusing on the pre-Cambrian crustal evolution and its relation to mineralization. A systematic collection of data is made including strata, magmatic rocks, metamorphism and deformation events and mineralization. Research on these data suggests that the basement of the Lufilian Arc is an Paleoproterozoic magmatism zone. At about 880 Ma, when the intracontinental rifting started, Nchanga granite and the early mafic magmatism were developed, and Roan group began to deposit. At about 765 Ma, the rifting process evolved to the stage of a proto-ocean rift, the deposition of Roan Group ended and the early Nguba Group began to settle down. Under the influence of hydrothermal fluids in the diagenesis period, co-sediment copper, cobalt, uranium, lead and zinc mineralization occurred. At about 660 Ma, the early oceanic crust subduction started nad the late clastic strata of Nguba group began to deposit. At about 550 Ma, a continental collision between the Kalahari Craton and Congo craton started and reached its peak at about 530 Ma, with high-temperature metamorphism and superposition continuing until about 520 Ma. Later on, the subduction slab retreated by the influence of nearly E-W far-field compression stress during the closure of Mozambique Ccean and formed Hook Batholith. From 520 Ma to 470 Ma, metamorphic rocks were uplifted and cooled. Under the influence of metamorphic hydrothermal fluids in syn-and post-tectonic stages, previous mineralization was remobilized, forming ore bodies at favorable places of structures.