贵州瓮安陡山沱组磷块岩的稀土元素地球化学特征与沉积古环境  

REE GEOCHEMISTRY OF DOUSHANTUO PHOSPHORITES AND PALEOENVIRONMENTAL CHANGES IN WENG'AN AREA, SOUTH CHINA

作　　者：解启来[1] 陈多福[2] 漆亮[3] 陈先沛[2] 

机构地区：[1]石油大学(北京)盆地与油藏研究中心,北京102249 [2]中国科学院广州地球化学研究所,广东广州510640 [3]中国科学院地球化学研究所,贵州贵阳550002

出　　处：《矿物学报》2003年第4期289-295,共7页Acta Mineralogica Sinica

基　　金：国家重点基金项目(No.49833002);国家自然科学基金项目(批准号:40273032);中国科学院广州地球化学研究所知识创新项目(GIGCX 03 04)

摘　　要：晚元古代末的陡山沱期(550～600Ma)是地球历史生物、化学和气候变化的剧烈时期。通过对贵州瓮安陡山沱组磷矿的稀土元素研究,确定上矿层磷块岩的北美页岩标准化稀土模式具负Ce异常、轻和重稀土亏损及中稀土富集特征。下矿层磷块岩稀土模式为轻微负Ce异常、轻微的轻和重稀土亏损及中稀土富集。下矿层磷块岩的Ceanom 值为-0 065～-0 077,上矿层磷块岩的Ceanom 为-0 26～-0 291,表明瓮安磷矿沉积古环境从下矿层的还原条件转变为上矿层的氧化条件。这种南沱冰期之后的环境变化可能为瓮安动物群的大爆发提供了必要的条件。The Doushantuo period, ranging from 550 Ma to 600 Ma, represents a period in which drastic biological, biochemical and climatic changes took place in terminal Proterozoic in South China. REE characteristics of Doushantuo phosphorites indicate a pronounced paleoredox condition change from the lower to the upper ore bed when Weng'an fauna, most probably the earliest metazoan fauna, emerged. The North American Shale-normalized REE patterns in the upper phosphorite bed are characterized by Vendian-Early Cambrian phosphorite patterns, but in the lower phosphorite bed the REE patterns are different with less negative Ce anomalies and less LREE and HREE depletions. Doushantao phosphatic samples record a Ceanom from -0.077 to -0.065 in the lower bed and from -0.29 to -0.25 in the upper ore bed, suggesting that the marine depositional condition changed from anoxic in the lower ore bed to oxic in the upper ore bed. These paleoenvironmental changes soon after the Marinoan (Nantuo) glaciation may have provided necessary conditions for the pronounced blooming of Weng'an fauna.

关 键 词：稀土元素 地球化学特征 沉积 古环境 瓮安动物群 陡山沱组磷块岩 晚元古代末期 

分 类 号：P592[天文地球—地球化学] P618.130.1[天文地球—地质学]