中国台湾国姓地区中新世海相菱铁矿结核成因——来自草莓状黄铁矿粒径和硫同位素的证据  

Genesis of siderite nodules in Miocene marine sediment in the Kuohsing area,Taiwan,China:Evidences from particle sizes and sulfur isotopes of pyrite framboids

作　　者：崔娜 王钦贤 贾子策[1] 陈成业 陈多福 CUI Na;WANG Qin-xian;JIA Zi-ce;CHEN Cheng-ye;CHEN Duo-fu(College of Marine Sciences,Shanghai Ocean University,Shanghai 201306,China;CAS Key Laboratory of Ocean and Marginal Sea Geology,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China)

机构地区：[1]上海海洋大学海洋科学学院,上海201306 [2]中国科学院广州地球化学研究所,边缘海与大洋地质重点实验室,广州510640

出　　处：《矿物岩石地球化学通报》2023年第6期1372-1379,共8页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(42172110)。

摘　　要：自生菱铁矿很好地记录了其形成时的地质信息及海洋中的生物地球化学过程,是示踪成岩作用带和氧化还原环境变化的绝佳载体。中国台湾国姓地区中新世猴洞坑组海相泥页岩中发育有大量自生菱铁矿结核,是次氧化带的产物。为进一步确认该菱铁矿形成时所处沉积环境的氧化还原状态和生物地球化学过程。本文对该区菱铁矿中保存完好的草莓状黄铁矿开展了粒径和硫同位素研究。结果显示,草莓状黄铁矿的粒径变化较大,平均粒径为9.23~11.55μm,最大粒径大于20μm,显示氧化-弱氧化的沉积环境特征;黄铁矿的δ^(34)S为-28.5‰~+3.1‰,平均值为-11.7‰,相较于海水(+21‰)富集轻的硫同位素,表明黄铁矿形成于相对开放的浅表层沉积物。黄铁矿的粒径分布规律和硫同位素特征均指示中国台湾国姓地区中新世海相菱铁矿形成于浅层弱氧化的次氧化带内。Authigenic siderite had well recorded the geological information of its formation and the biogeochemical processes in the ocean.It is an excellent carrier for tracing the diagenetic zone and the change of redox environments.A large number of authigenic siderite nodules found in the Miocene Houdongkeng formation marine muddy shale in the Kuohsing area of Taiwan,China are thought to be products of the sub-oxic zone.In order to further confirm the redox state and biogeochemical process of the sedimentary environment for the formation of siderite,in this paper,we have carried out a research of the particle sizes and sulfur isotopes of pyrite framboids which were well preserved in siderite nodules in the area.The results show that the pyrite framboids have particle sizes varying generally from 9.23μm to 11.55μm,with the maximum particle size of over 20μm,indicating that they were formed in the oxidized to weakly oxidized sedimentary environment.The pyrite framboids haveδ^(34)S values ranging from-28.5‰to+3.1‰,with an average value of-11.7‰,indicating that they are enriched in light sulfur isotope compared with the sea water(+21‰)and they were formed in a relatively open environment in shallow level of sediments.The size distribution regularity and sulfur isotopic characteristics of pyrite framboids further indicate that the Miocene marine siderite nodules were formed in the shallow and weakly oxidized sub-oxic zone in the Kuohsing area of Taiwan,China.

关 键 词：菱铁矿 黄铁矿粒径 硫同位素 台湾地区 

分 类 号：P593[天文地球—地球化学]