斜长石中人工合成流体包裹体的实验研究  

Experimental Study on Fluid Inclusion Synthesis in Plagioclase

作　　者：杜俊 刘洪微[3] 常洪伦 DU Jun;LIU Hongwei;CHANG Honglun(Hebei Key Laboratory of Strategic Critical Mineral Resources,Hebei GEO University,Shijiazhuang,Hebei 050031,China;Key Laboratory of High-Temperature and High-Pressure Study of the Earth’s Interior,Chinese Academy of Sciences,Guiyang,Guizhou 550081,China;North China Engineering and Investigation Institute,Shijiazhuang,Hebei 050021,China)

机构地区：[1]河北地质大学河北省战略性关键矿产资源重点实验室,河北石家庄050031 [2]中国科学院地球内部物质高温高压重点实验室,贵州贵阳550081 [3]华北有色工程勘察院有限公司,河北石家庄050021

出　　处：《现代地质》2023年第6期1634-1643,共10页Geoscience

基　　金：国家重点研发计划项目“金成矿作用过程中的水-岩相互作用”(2016YFC0600104-3)。

摘　　要：天然斜长石流体包裹体被广泛应用于揭示各种地质作用及地质过程的研究,但关于这类包裹体的捕获机制及捕获后的变化、地质温压计等研究需要基于斜长石的人工合成流体包裹体研究的验证或修正。目前,以斜长石为寄主矿物的人工合成流体包裹体技术尚未见诸报道。本文基于传统的寄主矿物裂隙愈合方法,通过在寄主矿物的预处理、囊组装等方面的适当改进,在1~1.5 GPa、800~900℃的条件下,模拟俯冲带中玄武质洋壳发生脱挥发分反应的实验中,以斜长石为寄主矿物的流体包裹体被成功地合成。对合成的包裹体进行了详细的岩相学观察、激光拉曼光谱分析和显微测温分析,以及尝试性的单个流体包裹体的激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)分析,结果显示斜长石捕获了常温下呈富碳液相+富水液相的两相流体包裹体,捕获的流体具有H_(2)O+CO_(2)±CH_(4)±N_(2)的组成,流体盐度因加入初始标液不同而有变化,有Cu、Mo等被活化进入到流体中。实验展示了基于斜长石的人工合成流体包裹体技术在二氧化硅不饱和体系的高温高压模拟实验中的成功运用,其在地质流体和实验地球化学等地学研究领域有广阔的应用前景。Natural fluid inclusions hosted by plagioclase are widely used to reveal mechanism under various geo-logical processes and phenomena.However,the capturing mechanism and subsequent changes,as well as geothermobarometer of such inclusions require validation or modification based on the study of artificially synthesized fluid inclusions in plagioclase.There are no available reports on the technology for fluid inclusion synthesis with host mineral like plagioclase.According to the conventional host mineral fracture healing method,the fluid inclusions were successfully synthesized in host plagioclase through improving the pretreatment of the plagioclase,and capsule assembly in experiments simulating the devolatilization reaction of basaltic crust in the subduction zone under 1-1.5 GPa and 800-900℃.Detailed petrographic observations,laser Raman spectroscopic analysis,microthermometric analysis,and preliminary laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)analysis of individual fluid inclusions were performed on the synthesized inclusions.We revealed that the plagioclase captured two-phase fluid inclusions with a carbon-rich liquid phase and a water-rich liquid phase at room temperature.The captured fluids have compositions of H_(2)O+CO_(2)±CH_(4)±N_(2),with varying salinity depending on the initial fluid used.Additionally,elements such as Cu and Mo were activated and entered the fluid.The plagioclase-based synthesis technology was demonstrated by the successful application in the high-temperature and high-pressure simulation experiments of silica-undersaturated systems.We suggest that the technology of fluid inclusion synthesis in plagioclase bear broad applications in geoscience fields such as geo-fluids and experimental geochemistry in future.

关 键 词：人工合成流体包裹体 斜长石 高温高压 实验研究 实验地球化学 

分 类 号：P579[天文地球—矿物学] P599[天文地球—地质学]