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大西洋洋中脊海底表层热液沉积物的铅同位素组成及其地质意义
引用本文:曾志刚,秦蕴珊,翟世奎.大西洋洋中脊海底表层热液沉积物的铅同位素组成及其地质意义[J].中国海洋大学学报(自然科学版),2001,31(1):103-109.
作者姓名:曾志刚  秦蕴珊  翟世奎
作者单位:1. 中国科学院海洋研究所,
2. 青岛海洋大学海洋地球科学学院,
基金项目:国家重点基础研究发展规划项目!(G2 0 0 0 0 46 70 3),东省自然科学基金课题!(Q98E0 2 139)资助
摘    要:新测得 TAG热液区中 6件海底表层热液沉积物样品的铅同位素组成 ,其变化范围不大 ,具有均一性的特征。在 Pb- Pb图解上 ,热液沉积物的铅同位素数据大多落在 MARB的铅同位素组成范围内 ,与大西洋沉积物和 Fe- Mn结核相比明显具较少的放射成因铅 ,反映其上部洋壳岩石为该区热液沉积物的形成提供了铅。对比研究表明 ,因不同地质 -构造环境中的海底热液区为热液沉积物形成提供物源的情况不同 ,是导致有沉积物覆盖洋中脊中热液沉积物的铅同位素组成与无沉积物覆盖洋中脊不同的主要原因。海底扩张中心的扩张速率与热液沉积物的铅同位素组成有一定的对应关系 ,但其并不是热液沉积物铅同位素组成的唯一控制因素

关 键 词:铅同位素组成  表层热液沉积物  TAG热液区
文章编号:1001-1862(2001)01-103-07
修稿时间:1999年6月3日

Lead Isotope Compositions of Seafloor Surface Hydrothermal Sediments in the TAG Hydrothermal Field of Mid Atlantic Ridge and its Geological Implications
Zeng Zhigang,Zhai Shikui,Qin Yunshan.Lead Isotope Compositions of Seafloor Surface Hydrothermal Sediments in the TAG Hydrothermal Field of Mid Atlantic Ridge and its Geological Implications[J].Periodical of Ocean University of China,2001,31(1):103-109.
Authors:Zeng Zhigang  Zhai Shikui  Qin Yunshan
Institution:Zeng Zhigang 1 Zhai Shikui 2 Qin Yunshan 1
Abstract:New data on lead isotope compositions of six seafloor surfacehydrothermal sediment samples from the TAG hydrothermal field h ave been obtained,the Pb isotopic ratios of TAG surface hydrothermal sediments are very homogeneous (206Pb/204Pb=18.218~18.343,with a mean of 18.283;207Pb/204Pb=15.408~15.522,with a mean of 15.486;208Pb/204Pb=37.583~37.938,with a mean of 37.817) a nd define a very small domain enclosed within the larger field of the Mid-Atlan tic Ridge basalts,and Pb isotopic compositions of the TAG surface hydrothermal sediments are clearly less radiogenic than those of Atlantic sediments or Fe-Mn crust,which suggests that the main source for Pb in the TAG surface hydrotherm al sediments is the upper ocean crustal rocks. It is mainly the different sources of the metals for the hydrothermal sediments from the different hydrothermal f ield in various geological environments,that result in the different lead isotope compositions of hydrothermal sediments between sediment-starved ridges and sediment-covered ridges. And in the sediment-starved ridges,the variations of lead isotope compositions for hydrothermal sediments between hydrothermal fields can be considerable,this agrees with the large variations in lead isotope compositions reported from mid-ocean ridge basalts,and our results further confir m previous studies by Andrieu et al. (1998) and Fouquet et al. (1995). On the other hand, the half rates of spreading have a corresponding relationship with the lead isotopic ratios of seafloor hydrothermal sediments, but it is clear that the spreading rate is not the only factor in controlling the lead isotope composi tions of hydrothermal sediments.
Keywords:lead isotopic composition  surface hydrothermal sediment  TAG hydrothermal field
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