地质科技情报2017，Vol.36Issue(4)：95-106,12.DOI:10.19509/j.cnki.dzkq.2017.0412
古海洋氧化还原地球化学指标研究新进展
New Progress on Geochemical Indicators of Ancient Oceanic Redox Condition
摘要
Abstract
Reconstruction of ancient oceanic redox conditions has been one of the hottest topics of the geosciences.Large numbers of proxies can be used to indicate the ancient marine sediments redox conditions.Geochemical and mineralogical methods were the primary means forancient ocean redox exploring.Previous studies mainly focused on a single indicators (e.g.,sedimentology,mineralogy,and geochemistry) unilateral study,lacking of systematic research.Uncertainties arose in using a single proxy for depositional oxidation reduction indicators which were affected by numerous factors.This paper mainly reviews the major elements (total organic carbon-TOC,molar ratio of organic carbon and phosphorus-Corg∶ P),redoxsensitive trace elements (U,V,Mo),pyrite type and framboid pyrite size distribution and isotopes (pyritic sulfur isotope-δ34 Spyrite,molybdenum isotopes-δ98Mo,uranium isotopes-δ238U),and the potential to distinguish euxinic,anoxic,suboxic and oxic conditions of water.In euxinic condition.,the concentrations of redox-sensitive trace elements and TOC are extensively enriched,with Mo enrichment larger than U (MoEF ＞UEF);high valued organic carbon and phosphorus molar ratio (Corg ∶ P);pyrite mainly consisting of framboid,yielding rarely euhedral crystals.The average grain size of framboid pyrite is less than 5 microns with small standard deviation,and δ34 Spyrite values were negative excursion and the δ98Mo values similar to the seawater isotope value (approximately + 2.3‰),δ238U values about + 0.2‰,higher than that in modern seawater (-0.41‰).Under oxic condition,with lower value of redox sensitive elements and TOC;and the molar ratio of the organic carbon and phosphorus (Corg ∶ P) also show low values;pyrite mainly consist of euhedral crystals,yielding few framboids with larger diameter,while δ34 Spyrite values exhibit positive excursions,with negative δ98 Mo values,-0.7‰,and δ238U values about-0.65‰.Under the anoxic and suboxic environments:various indicators were in the middle ranges of euxinic and oxic environments.The redox-sensitive elements and TOC enrichment show moderate concentration and U is more enriched compared to Mo (UEF＞ MoEF);with pyrite consisting of framboid and crystal,in large diametersand δ34 Spyrite,δ98Mo and δ238U between oxic and euxinic environment.Finally,this paper proposes that a variety of factors should be considered in the exploration of ancient ocean redox conditions.关键词
氧化还原/草莓状黄铁矿/微量元素/U同位素/Mo同位素/S同位素/古海洋Key words
redox/framboid pyrite/trace element/U isotope/Mo isotope/S isotope/ancient ocean分类
海洋学引用本文复制引用
张明亮,郭伟,沈俊,刘凯,周炼,冯庆来,雷勇..古海洋氧化还原地球化学指标研究新进展[J].地质科技情报,2017,36(4):95-106,12.基金项目
国家自然科学基金项目(41602022 （）
41402001 （）
41430101) （）
中央高校基本科研业务费专项资金资助项目(CUG160625) （CUG160625）
地质过程与矿产资源国家重点实验室科技部专项经费项目(MSFGPMR10) （MSFGPMR10）
中海油能源发展股份有限公司(GC2015ZC2622) （GC2015ZC2622）
