【摘要】 通过对浙江长兴煤山D剖面二叠—三叠"金钉子"灰岩样品Re-Os同位素、主微量元素和有机碳测定,对不同层位灰岩的沉积环境进行了判别。通过分析灰岩主微量元素、有机碳与Re、Os含量的相关性,探索性地研究了灰岩中Re、Os富集机制。研究发现,灰岩中Re、Os的富集主要受氧化还原作用影响,Re只有在还原环境下,才会被灰岩中的有机物富集,此时灰岩中Re含量较高,适用于Re-Os同位素定年,而Re在氧化环境下很难被灰岩中有机质富集。Os在还原环境下同样被有机质富集,但氧化环境下,部分Os也可以被灰岩地层中含铁、铜等自生矿物吸附富集,含铁、铜等自生矿物Os同位素比值可以代表沉积时海水Os同位素特征。Re、Os在灰岩中的富集机制研究对于将Re-Os同位素应用于灰岩地层精确定年及古环境示踪具有重要意义。Re、Os在不同氧化还原条件下的富集差异导致了还原环境沉积的灰岩中187 Re/188 Os要大于氧化环境灰岩中187 Re/188 Os,灰岩中187 Re/188 Os变化对研究古海洋沉积氧化还原环境可能具有一定指示意义。更多还原

【Abstract】 As a powerful geochronometer,the Re-Os isotope system has been successfully used for precisely dating depositional age of limestone,however,the removal mechanisms of Re and Os from seawater are not yet fully understood.The major and trace elements,Re-Os isotopes and TOC of the limestone from the Permian-Triassic boundary interval of the global stratotype section and point(GSSP)at Meishan,Changxing,Zhejiang Province,have been used to contrain redox conditions of sedimentary environment.The study on the occurrence of Re and Os in the limestone demonstrates that Re occurs in the organic matter of limestone only under highly reducing conditions.Hence,Limestone can be targeted for Re-Os dating only under reducing conditions.In contrast,Os removal from seawater to limestone can be found under various redox conditions.Authigenic minerals under oxic environments can enrich some Os,Thus,a high 187 Re/188 Os ratio can occur only in reducing sediments.The Os isotope system of authigenic materials that occurs in an oxic matine environment can be used as a paleo-marine environmental tracer.更多还原