高压—超高压变质岩外来^40Ar成因探讨  

Extraneous argon in HP-UHP metamorphic rock

作　　者：冯慧乐 王非[1,2] 师文贝[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]中国科学院青藏高原地球科学卓越创新中心,北京100101

出　　处：《地质科学》2016年第4期1261-1276,共16页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：中国科学院战略性先导科技专项（编号：XDB03020203）和国家自然科学基金优秀群体项目（编号：41521062）资助 致谢 感谢两位审稿人的审稿意见,基于他们的意见才使本文更加完善.

摘　　要：高压—超高压变质带是地球上重要的地质单元，特殊的形成环境使该类变质岩的矿物中常因含有外来^40Ar而^40Ar／^39Ar年龄偏老，制约了^40Ar／^39Ar年代学在此类岩石中的应用。本文探讨了氩在不同相中的溶解度与分配系数的差异，并着重论述了扩散参数与压力的关系及压力对岩体封闭性的影响，系统总结了高压—超高压变质矿物中外来^40Ar的形成机制。此外，随Fe/Mg、Si/Al、K等组分不同，氩在矿物中保存能力的某种规律性变化、离子孔隙度研究等也从理论上为研究氩的扩散和封闭行为提供了新的视角。在高压—超高压变质过程中多种因素共同作用，氩在这类矿物中的扩散更为复杂。对外来^40Ar形成机制的探讨对揭示高压—超高压变质结晶环境、岩体开放与否、不同矿物对氩保存能力等有重要的指示意义。Due to the special environment of High-ultrahigh pressure metamorphic belts that are important geological units in Earth,the ^40Ar/^39Ar dating of HP-UHP metamorphic rocks occasionally produce anomalously old ages attributed to extraneous ^40Ar, which would restrict the application of ^40Ar/^39Ar chronology in such regions. In this paper, we discuss the solubility and partition coefficient in different phase,especially the relationship between diffusion parameters and pressure and the influence of pressure to rock mass, and systematically summarize the mechanism of extraneous ^40Ar,in HP-UHP metamorphic rocks. We present the ability to preserve argon that is correlation with Fe/Mg,Si/Al,K and other components in mineral. In addition, ion porosity provides a new perspective to study the diffusion behavior of argon in theory. When multiple factors participate together in the process of high-ultrahigh pressure metamorphism,the argon diffusion behavior is more complicated. These are significant for revealing the environment of high-ultrahigh pressure metamorphism,judging the rocks open or closed,the Ar preserved ability of minerals and so on.

关 键 词：高压—超高压变质岩 ^40AR/^39AR 外来^40Ar 形成机制 

分 类 号：P597[天文地球—地球化学]