沉积学报2026，Vol.44Issue(3)：903-920,18.DOI:10.14027/j.issn.1000-0550.2024.126
鄂尔多斯盆地Toarcian大洋缺氧事件时期菱铁矿的成因及其地质意义
Lacustrine Siderite Formation in the Ordos Basin,North China:Insights into the Lower Jurassic Toarcian Oceanic Anoxic Event
摘要
Abstract
[Objective]The widespread siderites in the marine strata of the Toarcian Oceanic Anoxic Event(T-OAE)are believed to have resulted from a low sulfate concentration and increased terrestrial iron supply.Similar large amounts of siderite have also been reported in paleolakes in the same period.However,the mechanism of lacus-trine siderite development and its connection with the T-OAE remain unexplored,but is crucial to a better compre-hension of lacustrine biogeochemical cycling in the early Toarcian.[Methods]Mineralogical and carbon isotope geo-chemical analyses were performed on siderite samples from the lacustrine Anya section of the Ordos paleolake.The sources of iron and carbon,as well as the sedimentary environment,were investigated by integrating major and trace element data,which allowed exploration of the formation mechanism of siderites during the T-OAE period of climatic change.[Results]The coexistence of pyrites and siderites was observed by scanning electron microscopy(SEM).The value of inorganic carbon isotopes(δ13Ccarb)varies from-11.25‰ to+16.32‰,and the organic carbon isotope(δ13Corg)value ranges between-32.03‰ and+14.33‰.Light rare earth elements(REEs)are enriched and heavy REEs are depleted,with Eu anomalies ranging from 0.69 to 0.85.[Conclusions]The iron in the Anya siderites is derived from terrestrial inputs;the carbon included HCO3-produced by methanogenesis,as well as carbon released by organic matter decomposition and aerobic methane oxidation,either bacterially in the suboxic zone or archaeally below the oxic-anoxic interface immediately after methane production.The pore fluids during siderite formation were a suboxic to anoxic environment.During the T-OAE,intensified continental weathering and increased surface runoff transported abundant Fe2+ions into basin lakes whose widespread anoxia,abundant organic matter and low sulfate concentrations created favorable conditions for extensive siderite deposition.关键词
鄂尔多斯盆地/菱铁矿/成因机制/下侏罗统/缺氧事件Key words
Ordos Basin/siderite/formation mechanism/Lower Jurassic/anoxic event分类
天文与地球科学引用本文复制引用
陈杨,金鑫,黄一舟,张云望,陈俞超,王琴,时志强..鄂尔多斯盆地Toarcian大洋缺氧事件时期菱铁矿的成因及其地质意义[J].沉积学报,2026,44(3):903-920,18.基金项目
成都理工大学珠峰科学研究计划(2020ZF11414) Mount Everest Scientific Research Plan,No.2020ZF11414 （2020ZF11414）
