高压-超高压变质岩外来40Ar成因探讨

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。

Extraneous argon in HP-UHP metamorphic rock

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.