论文部分内容阅读
2010年发现的贵州道坨锰矿是一个超大型的海相沉积矿床,其含矿地层为南华系大塘坡组一段黑色页岩.对道坨锰矿大塘坡组一段含锰黑色页岩测定的Re-Os同位素等时线年龄为660.6±7.5 Ma,该年龄与前人测定的大塘坡组黑色页岩底部凝灰岩夹层中锆石U-Pb年龄在误差范围内一致,进一步限定了“大塘坡”式锰矿的成矿时代和Sturtian冰期的结束年龄,且可与全球Sturtian冰期结束的Re-Os同位素年龄进行对比.由Re-Os等时线年龄得到的~(187)Os/~(188)Os初始比值为0.781,结合前人的研究成果,说明在Sturtian冰期后伴随着大气氧含量的快速升高及陆地冰川的融化,冰川融水携带着陆源物质进入到含Mn~(2+)的裂谷盆地,使得盆地表层水体含氧量迅速增加,生物大量繁殖,Mn~(2+)被氧化为MnO_2而沉淀,之后在盆地底部还原环境中伴随着有机质的埋藏及成岩作用而最终形成菱锰矿.
The Tao Tuo manganese deposit in Guizhou Province, discovered in 2010, is an ultra-large marine sedimentary deposit, and the ore-bearing formation is a black shale in the Datangpo Formation of the Nanhua System. The Re-Os isotope isochron age is 660.6 ± 7.5 Ma, which is consistent with the U-Pb zircon age of the tuff intercalation at the bottom of the black shale in Datangpo Formation And the ending age of the Sturtian glacial period in the “Tongpo” manganese deposit and can be compared with the Re-Os isotopic ages at the end of the Sturtian ice age in the world. The ~ (187) Os / ~ (188) Os initial ratio of 0.781, combined with previous research results, indicating that after the Sturtian glacial period with the rapid increase of atmospheric oxygen content and the melting of terrestrial glaciers, +), The oxygen content in the surface water of the basin increased rapidly and the organism multiplied. Mn 2+ was oxidized to MnO 2 and precipitated. Subsequently, the organic matter buried and diagetted in the bottom of the basin under reducing environment The final formation of rhodochrosite.