湖北古城锰矿Fe同位素特征及其古环境意义  

Fe Isotope Characteristics of the Gucheng Manganese Ore Deposits in Hubei Province and Its Geological Implication

作　　者：张飞飞[1] 彭乾云[2] 朱祥坤[1] 闫斌[1] 李津[1] 程龙[3] 斯小华[3] 

机构地区：[1]中国地质科学院地质研究所,国土资源部同位素地质重点实验室,大陆构造与动力学国家重点实验室,北京100037 [2]贵州省地质矿产勘查开发局103地质大队,贵州铜仁554300 [3]中南冶金地质研究所,湖北宜昌443003

出　　处：《地质学报》2013年第9期1411-1418,共8页Acta Geologica Sinica

基　　金：国土资源公益性行业科研专项经费项目(编号201011027);地质调查项目(编号1212011121069);国家自然科学基金项目(编号)的成果

摘　　要：本文报导了湖北古城锰矿含锰层位中黄铁矿Fe同位素的研究结果,并利用黄铁矿Fe同位素对黄铁矿成因和大塘坡早期阶段沉积环境的氧化还原状态进行了制约。黄铁矿δ~56Fe值变化范围为-0.13‰^+0.54‰,平均值为+0.22‰,显示相对于当时海水(0^-0.5‰)明显富集Fe的重同位素。本文认为黄铁矿的Fe来自海水中Fe^(2+)部分氧化形成的Fe^(3+),这些Fe^(3+)在成岩过程中被全部还原,与细菌硫酸盐还原作用形成的H_2S结合最终以黄铁矿形式保存在沉积物中。大塘坡式锰矿含锰层位中黄铁矿Fe同位素特征表明,古城冰期(Sturtian冰期)结束之后,大塘坡早期阶段海洋深部已经开始氧化,但是并没有完全被氧化。This paper reported Fe isotope compositions for pyrite in the Mn-bearing series of the Gucheng manganese ore deposits in Hubei province. Fe isotope analysis was used to constraint processes for pyrite formation and sedimental environment during the early stage of Cyrogenian Datangpo Formation. Our results show 8 56Fe values range from --0. 13% to ＋0. 54% with a mean of 0. 22%, indicating those pyrites are enrichment in heavier Fe isotope relative to ambient seawater （8 S6Fe = 0 - 0. 5%）. We suppose partial oxidation of the initial ferrous iron to ferric iron and the following near-quantitative transformation of iron-oxide or iron-hydroxide into pyrite during diagenesis is responsible for the positive Fe isotopes values for those pyrites in the Mn-bearing series. Thus, it is suggested in this study that the deep ocean is gradually oxidized after Tiesi＇ao deglaciation, but is not totally oxidized.

关 键 词：古城 锰矿 黄铁矿 FE同位素 古环境 成冰系 

分 类 号：P618.32[天文地球—矿床学] P597[天文地球—地质学]