贵州道坨锰矿成矿时代及环境的Re-Os同位素证据

发布时间：2018-04-17 20:20

本文选题：锰矿 + 大塘坡组　；参考：《科学通报》2017年Z2期

【摘要】：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.
[Abstract]:The Daotuo manganese deposit, which was discovered in 2010, is a very large marine sedimentary deposit. The ore-bearing strata are the black shale of the Datangpo formation of the South China series.The Re-Os isotopic isochron age of the first section of the Datangpo formation is 660.6 卤7.5Ma. this age is consistent with the zircon U-Pb age in the tuff intercalation at the bottom of the Datangpo formation.The metallogenic age of the Datangpo type manganese deposit and the end age of the Sturtian glacial age are further limited, and can be compared with the Re-Os isotopic age at the end of the global Sturtian glacial age.The initial ratio of Re-Os isochron dating is 0.781. Combined with previous studies, it is shown that the rapid increase of atmospheric oxygen content and the melting of terrestrial glaciers are associated with the Sturtian glacial age.Glacial meltwater carries land-based materials into the rift basin containing Mn~(2, which makes the oxygen content in the surface water of the basin increase rapidly, and a large number of living organisms are oxidized to MnO_2 and precipitated.After that, magnesite was formed in the reductive environment at the bottom of the basin with the burial and diagenesis of organic matter.
【作者单位】：中国地质科学院矿产资源研究所;国土资源部成矿作用与资源评价重点实验室;贵州大学资源与环境工程学院;国家地质实验测试中心;贵州省地质矿产勘查开发局一0三地质大队;
【基金】：国家自然科学基金(41472089) 中国地质调查局地质调查项目(DD20160346)资助
【分类号】：P597;P618.32

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