非洲中部基巴拉造山带地质特征与资源潜力分析

Geological Characters and Resources Potential in the Kibaran Belt,Central Africa

中元古代基巴拉造山带主要由石英岩、变质泥岩和侵入的花岗质岩石构成。基巴拉带岩浆演化代表了一个完整的陆内裂谷演化旋回:地壳拉伸接受沉积,同时岩石圈减薄、软流圈上涌、镁铁-超镁铁质岩浆侵入上地壳形成一种双峰式岩浆岩;之后受挤压造山作用,岩浆侵入背斜核部,沉积层褶皱成山;中元古晚期-新元古早期含矿热液沿构造通道上升,在早期形成的花岗岩与基底或盖层的接触带内沉淀、富集成矿。基巴拉带内Cu-Ni矿化与镁铁-超镁铁质岩体密切相关,同时PGE-Au有较大的找矿潜力;锡石花岗岩是重要的含矿花岗岩,伟晶岩中多见Sn-W-Au、NbTa、Li、Be矿化;金多产于与锡石花岗岩有关的角砾岩型构造破碎带内。

The Mesoproterozoic Kibaran belt is composed of three distinct stratigraphic units, they are quartzites, metapelitic rocks and intrusive granitic rocks. Complete cycle of intra-continent rift magmatic evolution can be found in Kibaran, we propose the following. First of all, the crustal extension to receive deposits, at the same time, the lithospheric thinning and the asthenosphere upwelling, result in mafic-ultramafic magma invaded into upper crust and formed the bimodal magmatic rocks, after this, the collsion orogeny make the sediments folded and formed mountain, and then, magma invaded in the core of anticline. Then the hydrothermal orebearing liquids rose following the channel which formed at the tectonic event before, and deposited in the contact zone between the granite and basement or cove from Mesoproterozoic to early Neoproterozoic. The maficultramafic rocks in the Kibaran belt is very famous in Cu-Ni mineralization, and also have great potential of PGE-Au mineralization. Cassiterite-granite is a very important kind of ore-bearing granites, and the pegmatites are well known for their Sn-W-Au, Nb-Ta, Li, Be mineralization. Gold usually can be found in tectonic breccia type of fracture zones, and it is very close to cassiterite granite in genetic.