一个浅海裂谷盆地的古老热水沉积锰矿——以武陵山震旦纪锰矿为例

OLD HOT BRINE MANGANESE DEPOSITS IN A SHALLOW-SEA RIFT BASIN: AN EXAMPLE FROM THE SINIAN MANGANESE DEPOSITS IN THE WULING MOUNTAIN AREA

摘要:

在我国贵州省东北部、湖南省西北部和四川省东南隅交界地带的武陵山区,分布着许多锰矿床(点),这就是产于上元古宇震旦系著名的大塘坡式锰矿。60年代后期至今的20年间进行了大量普查勘探工作,获得了丰富的矿床地质资料。80年代初期,笔者曾对黔东及邻区大塘坡式锰矿进行了较系统的研究,于1985年发表了相应的专著。近年又对其作了深入研究,在本文中笔者将简要论述这类古老锰矿床的成因及其热水成矿作用模式。

Abstract:

There are a number of the Late Proterozoic manganese deposits in the Wuling Mountain area, South China. The deposits are confined largely to the sapropel-type carbonaceous shales of the Lower Sinian Datangpo Formation (ca. 700 Ma), and characterized by orientation, zonation and equidistance of their spatial distribution. The genetic model for the deposits may be compared with that for modern ocean-ridge manganese deposits, and their formation tend to be constrained by the factors such as basement nature, Sinian sedimentary cycles, depositional system and palaeotectonic settings of the basin. The mineralization model suggested by the author has offered an alternative explanation for the formation of the foregoing manganese deposits. During Early Siniam, the uplifting of the mantle and rifting of the crust allowed for superficial water to penetrate downwards along the faults or rifts, giving rise to a hot brine convective system. After having emplaced in the shallow-sea basin in the Wuling Mountain area, the ore-bearing hot brine from the hydrothermal system was subjected to biological and chemical processes, thus resulting in the formation of the manganese deposits in the study area.