地壳浅部(低温-低压条件下)卤水-安山质火山岩作用实验研究及其地质意义  

Experimental studies of interaction between brine and andesitic rocks at low temperature and pressure condition in shallow crust and geological implications

作　　者：李建平[1,3] 陈华勇 张婷[2,3] 张世涛[1] LI Jian-ping;CHEN Hua-yong;ZHANG Ting;ZHANG Shi-tao(Key Laboratory of Mineralogy and Metallogeny/Guangdong Provincial Key Laboratory of Mineral Physics and Materials,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;Key Laboratory of Petroleum Resources,Gansu Province/Key Laboratory of Petroleum Resources Research,Institute of Geology and Geophysics,Chinese Academy of Sciences,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室/广东省矿物物理与材料研究开发重点实验室,广东广州510640 [2]中国科学院油气资源研究重点实验室/甘肃省油气资源研究重点实验室,甘肃兰州730000 [3]中国科学院大学,北京100049

出　　处：《地球化学》2019年第5期468-482,共15页Geochimica

基　　金：中国科学院战略性先导科技专项(XDB1803206);国家杰出青年科学基金(41725009);国家自然科学基金(41702068)

摘　　要：水岩作用是影响地球岩石圈层质量平衡的重要过程,控制着围岩和流体中元素的迁移、重新分配以及物质组成的演化。本研究通过实验手段模拟地壳浅部(低温-低压条件下)火山围岩与含碱卤水的相互作用,来揭示围岩元素迁移、碱交代蚀变过程和流体的成矿潜力。实验结果显示,不同pH条件下产物具有不同的碱交代蚀变特征,碱性条件有利于岩石样品同时发生钾化和钠化蚀变,但前者占据主导,而酸性条件下则仅发生钾化蚀变。产物中主元素和成矿元素,如Cu、Fe、Zn、Mn和LREE等发生明显淋滤,该过程受温度和流体pH影响明显。随温度上升产物淋滤程度明显增强,相同温度不同pH条件下产物淋滤程度虽然处于同一数量级,但酸性条件下淋滤程度更加明显。实验结果表明,地壳浅部高温酸性卤水与(安山质)火山围岩作用,有利于形成富含Fe、Cu、Zn和Mn等元素的含矿流体,而低温碱性流体有利于富集和迁移LREE。本实验为揭示地壳浅部火山围岩与卤水的作用过程和元素迁移、富集机制,以及判断流体成矿潜力提供了有效证据。The fluid-rock interaction is a significant process that controls mass balance in Earth’s lithosphere,which also influences component migration,redistribution,and composition evolution of surrounding rocks and external fluids.To investigate the element migration,alkali metasomatism,and formation of external mineralization fluid,we employed an experimental technique to simulate the fluid-rock interactions that occur in shallow crust.The results indicate that alkali metasomatism characteristics varied at different pH conditions.The alkaline condition is favorable to both potassic and sodic alteration with products dominated by the former,while only potassic alteration was occurred under acidic condition.All major elements and some ore metals,such as Cu,Fe,Zn,Mn and LREE,in products were leached except for potassium.The leaching process was obviously affected by fluid temperature and pH,and the leaching rate increased with heating.The extent of element leaching in products is similar under the same temperature conditions with various fluid pH,while element leaching is more obvious under acidic condition.It can be inferred from the experimental results that high-temperature acidic brine interacted with andesitic rocks in shallow crust has a tendency to form ore-forming fluids rich in Fe,Cu,Zn and Mn.In contrast,low-temperature alkaline brine tends to leach and migrate LREE from country rocks.This experiment provides effective support for the fluid-rock interaction process,element migration mechanism,and formation of mineralization fluid in shallow crust.

关 键 词：地壳浅部 火山围岩 富碱卤水 元素淋滤 成矿指示 

分 类 号：P599[天文地球—地球化学]