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湘西黑色岩系地球化学特征和成因意义
The Origin and Geochemical Characteristics of Upper Sinain_Lower Cambrian Black Shales in Western Hunan
  
中文关键词:黑色岩系 地球化学 缺氧环境 有机质 湘西
英文关键词:black shales,geochemistry,organic matter,anoxic environmlent,western Hunan
基金项目:国家自然科学基金重点资助项目(49132050)
作者单位
吴朝东  
杨承运  
陈其英  
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中文摘要:
       本文采用GC_MS、ICP_MS、形态硫分析、硫同位素、物相分析等方法综合研究了湘西晚震旦世-早寒武世黑色岩系的地球化学特征和形成条件。湘西黑色岩系以富有机质为特征,其来源为藻、菌类生物,形成于缺氧环境。缺氧标志包括有机碳、黄铁矿含量、硫同位素、稀土元素的分布、δU、DOP和生物标志物等参数。在黑色页岩中富集V、Ni、Mo等微量元素,并在局部地区形成具有工业价值的矿床。研究认为,生物、有机质对一些元素的吸收、络合作用是黑色岩系中富集多种元素的主要原因。稀土元素的分布和硫同位素的组成表明湘西黑色岩系形成于缺氧的陆架边缘浅海环境,海底热液活动为其提供了丰富的物质来源。
英文摘要:
      This paper deals with the formation conditions of black shales based on such analytical techniques as ICP_MS, GC_MS, isotope, organic carbon, element facies and micropetrology. Studies show that the Upper Sinian_Lower Cambrian black shales were formed in an anoxic environment, and the organic sources were algae and fungi (Thallophyta). The paper points out five geochemical indicators of anoxic environment. The organic matter, especially lipids, can be well preserved in an anoxic environment. Black shale is also an indicator of the oceanic anoxic event. During the slow degradation of organism, the organic matter absorbed and combined many elements. At the early diagenetic stage, the organic matter was decomposed, and some elements were remobilized. Hence the elements exhibit multi_stage enrichment and varied forms. The key factor is the adsorption of organism and the combination with the organic matter. The strata of Ni_Mo, coal stone, barite and phosphorite deposits are controlled by the change of sea level, and the ore_bearing sets are developed in the transgressive series and condensed sections. The black shales are characterized by high content of Ni, Mo and Mn, lower total REE, comparative enrichment of HREE, and negative Ce anomaly. Geochemical and REE features indicate that black shales were deposited in an epeiric sea environment.
吴朝东,杨承运,陈其英,1999,湘西黑色岩系地球化学特征和成因意义[J].岩石矿物学杂志,18(1):26~39.
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