| 华北中元古代陆表海氧化还原条件 |
| |
| 引用本文： | 汤冬杰,史晓颖,裴云鹏,蒋干清,赵贵生.华北中元古代陆表海氧化还原条件[J].古地理学报,2011,13(5):563-580. |
| |
| 作者姓名： | 汤冬杰 史晓颖 裴云鹏 蒋干清 赵贵生 |
| |
| 作者单位： | 1.中国地质大学(北京)地球科学与资源学院， 北京100083;2.中国地质大学(北京)地质过程与矿产资源国家重点实验室，北京100083;3.美国内华达大学地球科学系，美国拉斯维加斯，NV 89154-4010 |
| |
| 基金项目： | 国家自然科学基金项目(编号：40972022，40921062)及国家“973”项目(编号：2011CB808806)资助成果 |
| |
| 摘 要： | 文石海底沉淀是地球早期大气高CO2浓度、海洋贫氧条件下,CaCO3过饱和而直接沉淀于海底所形成的自生碳酸盐,可反映古海洋贫氧状态.对华北中元古界雾迷山组(ca 1.50～1.45 Ga)碳酸盐岩的研究发现:潮下带下部黑色纹层石由针状文石假晶等厚层与微生物席层交互堆叠而成；潮下带中部凝块石白云岩(A单元)主要由针状文石假...
|
| 关 键 词： | 中元古代 古海洋条件 文石海底沉淀 氧化还原敏感元素 华北地台 |
| 收稿时间： | 2011-04-25 |
Redox status of the Mesoproterozoic epeiric sea in North China |
| |
| Tang Dongjie,Shi Xiaoying,Pei Yunpeng,Jiang Ganqing,Zhao Guisheng.Redox status of the Mesoproterozoic epeiric sea in North China[J].Journal of Palaeogeography,2011,13(5):563-580. |
| |
| Authors: | Tang Dongjie Shi Xiaoying Pei Yunpeng Jiang Ganqing Zhao Guisheng |
| |
| Institution: | 1.School of the Earth Sciences and Resources，China University of Geosciences(Beijing)，Beijing100083;2.State Key Laboratory of Geological Processes and Mineral Resources，China University of Geosciences(Beijing)，Beijing100083;3.Department of Geosciences，University of Nevada，Las Vegas，NV 89154-4010，USA |
| |
| Abstract: | Marine authigenic aragonite crystal fans and isopachous cements are mainly formed in anoxic-dysoxic seawater or pore waters with oversaturated CaCO3 derived from bacterial sulfate reduction(BSR).Their presence can be used as a potential indicator for redox conditions of the depositional environment.Carbonate units from the Mesoproterozoic Wumishan Formation(ca.1.5～1.45 Ga)in North China Platform show that aragonite fans and cements are common in deep subtidal deposits，but decline in shallow subtidal and disappear in intertidal deposits.Particularly the biolaminites deposited from deep-subtidal environments are composed of submillimeter-scale dark-light couplets of microbial mat and isopachous aragonite.Microscopically，the isopachous aragonites are composed of fibrous crystals or fan-shaped aggregates，similar to those recognized from the Archean strata of South Africa.Carbonates commonly form shallowing-upward cycles with shallow subtidal facies(Unit A) at the base，intertidal facies(Unit B) in the middle and supratidal facies(Unit C) at the top.The shallow subtidal facies(Unit A)contain abundant thrombolites，in which meso-clots consist typically of fabrous or fan-shaped aragonite aggregates surrounding organic-rich nuclei or pyrite grains，but rarely with carbonates micritic grains.Intertidal facies(Unit B)are dominated by laminated dolostone with interbeds of grainstones or packstones.Aragonite fans and cements are present but not abundant.Most of the aragonites in this unit grow on mat fragments or previously formed minerals，either as isopachous，fan-shaped or as botryoidal aggregates that fill cavities.Supratidal facies(Unit C)consists of micritic dolostone with pseudomorphs of halite and desiccated microbial mats but no aragonite crystal fans or cements. Geochemical analysis shows that V/Th，Mo/Th and U/Th increase from Unit C to Unit A，suggesting progressive anoxic condition with increasing water depth.Our study shows that during deposition of the Wumishan Formation(ca.1.5～1.45 Ga)，the North China epeiric sea was likely anoxic below the fair-weather wave base，but the abundance of aragonite crystal fans and fibrous cements in deep-subtidal environments imply the availability of sulfate in shelf environments of the Mesoproterozoic epeiric sea. |
| |
| Keywords: | Mesoproterozoic palaeooceanographic conditions aragonite sea-floor precipitates redox sensitive elements North China Platform |
| 本文献已被 万方数据 等数据库收录！ |
| 点击此处可从《古地理学报》浏览原始摘要信息 |
| 点击此处可从《古地理学报》下载免费的PDF全文 |
