贵州道坨锰矿成矿时代及环境的Re-Os同位素证据  

Mineralization age and metallogenic environment of Daotuo manganese deposits in Guizhou: Evidence from Re-Os isotopes

作　　者：裴浩翔[1,2] 付勇 李超[4] 李延河[1,2] 安正泽[5] PEI HaoXiang FU Yong LI Chao LI YanHe AN ZhengZe(Institute of Mineral Resource, Chinese Academy of Geological Sciences, Beijing 100037, China MLR Key Laboratory of Metallogeny and Mineral Assessment, Beijing 100037, China College of Resource and Environmental Engineering, Guizhou University, Guiyang 550000, China National Research Center for Geoanalysis, Beijing 100037, China No. 103 Geological Party, Bureau of Geology and Mineral Exploration and Development of Guizhou Province, Tongren 554300, China)

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]国土资源部成矿作用与资源评价重点实验室,北京100037 [3]贵州大学资源与环境工程学院,贵阳550000 [4]国家地质实验测试中心,北京100037 [5]贵州省地质矿产勘查开发局一〇三地质大队,铜仁554300

出　　处：《科学通报》2017年第28期3346-3355,共10页Chinese Science Bulletin

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

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.The Neoproterozoic is a critical interval in Earth＇s history, having witnessed the breakup of supercontinent Rodinia, global glaciations （or the snowball Earth）, and the evolution of multicellular organisms. It is proposed that the breakup of Rodinia might have triggered the snowball Earth, while the termination of the Neoproterozoic global glaciations might have triggered the evolution of life in the Ediacaran Period. Two snowball Earth events, the Stur- tian （717-663 Ma） and the Marinoan （654-635 Ma） glaciations, were separated by an interglacial interval of-10 million years （663-654 Ma）. In South China, the Sturtian and Marinoan glacial deposits are represented by the Jiangkou and Nantuo Formations. The interglacial Datangpo Formation is characterized by widespread manganese （Mn） ore deposits, such the Datangpo and Xixibao in Guizhou, Minle in Hunan, and Xiushan in Chongqing, repre- senting the most important metallogenic period of Mn in China. The Daotuo Mn ore, a superlarge-scale deposit （approximately 200 million tons）, was first discovered in 2010 in northeastern Guizhou. It is hosted in a fault-bound depression system between the Yangtze block and the Jiangnan orogenic belt. The Mn ores were discovered in black shale of the Member I of the Datangpo Formation, and occur as rhodochrosite （MnCO3）. In order to constrain the age of Mn ores, here we report Re-Os isochron age of the ore-bearing black shale from the Member I of the Datangpo Formation. The Re-Os isochron age of the Member I black shale is 660.6±7.5 Ma, consistent with the zircon U-Pb age of the tuff layer from the base of the Datangpo Formation and other Re-Os isochron ages from other localities （such as Canada, Australia, Scotland, and Mongolia）. Furthermore, the initial value of 187Os/188Os from the Re-Os isochron age is 0.781, suggesting predominantly terrestrial input. Based on previous research, it is shown that during the Sturtian glaciation, under the influence of sea ice cover barrier and atmospheric mat

关 键 词：锰矿 大塘坡组 Re—Os同位素 冰期 

分 类 号：P597[天文地球—地球化学]