地学前缘 ›› 2009, Vol. 16 ›› Issue (1): 114-124.

• 论文 • 上一篇    下一篇

1 kbar、800 ℃下REE在富磷过铝质熔体/流体相间分配的实验研究

  

  1. 1中国科学院 地球化学研究所 地球深部物质与流体作用地球化学研究室, 贵州 贵阳 550002
    2中国科学院 研究生院, 北京 100049

  • 出版日期:2009-02-02 发布日期:2009-02-02
  • 作者简介:张辉 (1965—),男,研究员,博士生导师,实验地球化学专业。E-ail:zhanghui65@hotmail.com
  • 基金资助:

    国家重点基础研究发展计划“973”项目 (2007CB411303);科学技术部支撑计划“305”项目(2007BAB25B01);国家自然科学基金项目 (40673052,40273030)

An experimental study of REE partitioning between phosphorusrich peraluminous melt and coexisting aqueous fluid at 1 kbar and 800 ℃

  1. 1Laboratory for Study of the Earths Interior and Geofluids, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
    2Graduate School, Chinese Academy of Sciences, Beijing 100049, China

  • Online:2009-02-02 Published:2009-02-02

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摘要：

利用“RQV快速内冷淬火”(或称之为“外加热冷封式”)高温高压实验装置,实验研究了1 kbar、800 ℃条件下12个REE+Y在富磷过铝质熔体/含水流体相间的分配,并利用EMP、LAICPMS和ICPMS分析技术分别测定了实验初始物、实验产物玻璃中主要化学组成以及熔体相和流体相中REE含量。实验结果表明,REE元素 (La,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb和Lu)在流体/熔体相间的分配系数 (Dfluid/melt)在(01～199)×10-4范围,Dfluid/meltY在(02～78)×10-4范围,指示REE和Y强烈趋向于在熔体中富集。REE在流体/熔体相间的分配系数 (Dfluid/melt)与体系中P2O5含量变化呈近抛物线状分布,其最大值对应于残余熔体中w(P2O5)为144％处。REE在流体/熔体相间的分配系数 (Dfluid/melt)随REE的原子序数增大而逐渐降低,构成右倾的平滑曲线,总体上显示出DLREE>DMREE>DHREE的趋势。Y与Ho在流体/熔体相间分配系数的比值 (DY/DHo)约为1 (091～128),不随体系中P2O5变化而变化的特征。上述特征表明熔体流体作用不会导致YHo及REE间的分异,因此,可推断熔体流体作用过程不可能是过铝质岩浆体系中产生稀土“四重效应”机制。

关键词: 分配系数;熔体-体作用;富磷岩浆体系;高温高压实验

Abstract:

Abstract:  Fluidsaturated experiments were conducted to investigate the partitioning of 12 REE and Y between the phosphorusrich peraluminous melt and coexisting aqueous fluid at 1 kbar and 800 ℃All runs were conducted in coldseal RapidQuench pressure Vessels (RQV, a kind of “externally heated coldseal pressure vessels”) using water as a pressure medium for durations of 144 hoursThe major chemical compositions of the initial and runproduct glasses were determined by EMPA; REE contents of the initial and runproduct glasses were determined by LAICPMS; REE contents of aqueous fluids were analyzed by ICPMSIt shows that the partitioning coefficients of REE (including La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) between aqueous fluid and hydrous melt (Dfluid/melt) vary from 01×10-4 to 199×10-4, and Dfluid/meltY range from 02×10-4 to 78×10-4, indicating that REE and Y are preferentially partitioned into the hydrous meltsThe relationship of the fluidmelt partitioning coefficients of REEs to the phosphorus contents in the runproduct glasses shows a nearnormal distribution as the contents of P2O5increasing from 019 wt％ to 609 wt％, with the maximum Dfluid/melt corresponding to 144 wt％ of P2O5The fluidmelt REE partitioning coefficients decrease as increasing the atomic numbers of  REE from La to Lu, showing DLREE>DMREE>DHREEgenerallyThe ratios of DY to DHo show no obvious variations with increasing P2O5 contents in the runproduct glasses from 019 wt％ to 609 wt％, keeping a nearly constant value of ～1 (in the range of 091128)The experimental results demonstrate that the interaction of phosphorusrich peraluminous melt with coexisting aqueous fluid could not result in the fractionation between Y and Ho, and among the REEs.Therefore, it is implied that the meltfluid interaction cannot be a candidate for the mechanism of REE tetrad effect during the evolution of peraluminous magmatic system.

Key words:

Key words: partitioning coefficient; meltfluid interaction; phosphorusrich magmatic system; hightemperature and highpressure experiment

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