含水硅酸盐熔体中铜溶解度的实验研究  

An Experimental Study of the Solubility of Copper in Hydrous Silicate Melts

作　　者：刘星成[1,2,3] 许婷[1,2,3] 熊小林 李立 王煜[1,2] 邢长明 LIU Xingcheng;XU Ting;XIONG Xiaolin;LI Li;WANG Yu;XING Changming(State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,Guangdong,China;College of Earth and Planetary Sciences,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,同位素地球化学国家重点实验室,广东广州510640 [2]中国科学院深地科学卓越创新中心,广东广州510640 [3]中国科学院大学,北京100049

出　　处：《大地构造与成矿学》2022年第4期803-813,共11页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(42073057、41573053);中国科学院青年创新促进会项目(2019344)联合资助。

摘　　要：富Cu岩浆是形成大型-超大型斑岩型Cu矿床的有利条件,但形成富Cu岩浆的有利物理化学条件尚不清楚。为了制约温度、压力、熔体成分、氧逸度等因素对含水硅酸盐熔体中Cu溶解度的影响,本次研究采用Pt_(95)Cu(05)作为样品管,使用活塞圆筒装置开展了一系列高温高压实验。实验初始物成分涵盖镁铁质到长英质,实验温度范围为850~1250℃,压力范围为8~30 kbar,氧逸度范围约为FMQ-5~FMQ+5。实验结果表明长英质熔体中Cu溶解度主要受温度和熔体成分控制,受压力影响不明显。在相似氧逸度条件下,当温度从1250℃下降到850℃时,Cu溶解度降低了约两个数量级。在相同温度和相似氧逸度条件下,玄武质、安山质和英安质熔体中Cu溶解度差别较小。但当熔体演化为花岗质或流纹质熔体时,Cu溶解度骤降约一个数量级。因此,当中酸性岩浆演化到晚期,随着温度的降低和熔体成分变化,其运移Cu的能力会迅速降低,不利于富Cu岩浆的产生。在中酸性岩浆演化过程中,如果流体过晚出溶,将不利于形成富Cu流体,难以为大型矿床的形成提供足够的成矿元素。Cu-rich magma favors the formation of large-giant porphyry Cu deposits.However,the favorable physicochemical conditions for Cu-rich magma generation are not well constrained.In order to investigate the effects of temperature,pressure,melt composition,and oxygen fugacity on Cu solubility in hydrous silicate melts,we employed Pt_(95)Cu(05)alloy capsule with starting materials ranging from mafic to felsic glasses and performed experiments with piston-cylinder apparatus at 850-1250℃,8-30 kbar,and oxygen fugacity(fO_(2))in range of FMQ-5-FMQ+5.The result shows that the effects of temperature and melt composition are significant on Cu solubility in felsic melts,whereas the influence of pressure is limited.The Cu solubility decreases by about two orders of magnitude as temperature drops from 1250℃to 850℃at similar fO_(2)conditions.There is no substantial variation of Cu solubility in basaltic,andesitic,and dacitic melts at the same temperature and comparable fO_(2).Nevertheless,the Cu solubility in the more evolved magmas,such as granitic or rhyolitic melt,is lower by about one order of magnitude.Therefore,it can be inferred that the capacity of Cu transport of magma decreases rapidly in the late stage of magmatic processes.If the fluid saturation occurs too late,the generation of Cu-rich fluid will be largely hampered,which will low the potential for porphyry Cu mineralization.

关 键 词：铜溶解度 硅酸盐熔体 高温高压实验 斑岩型铜矿床 

分 类 号：P589.1[天文地球—岩石学]