内蒙古迪彦钦阿木斑岩钼矿床成矿流体的出溶、演化及对成矿的制约  

Fluid exsolution,evolution for the ore-controlling in Diyanqin’amu porphyry Mo deposit,Inner Mongolia

作　　者：崔凯 李腊梅 吴皓然 王兴源 王信 廉永 谢玉玲[1] CUI Kai;LI La-mei;WU Hao-ran;WANG Xing-yuan;WANG Xin;LIAN Yong;XIE Yu-ling(Civil and Resource Engineering School,University of Science and Technology Beijing,Beijing 100083,China;Institute of Mineral Recourses Research,China Metallurgical Geology Bureau,Beijing 101300,China;Xilin Gol League Shanjin Baiyin Hubu Mining Co.,Ltd.,Xilinhot 026316,China)

机构地区：[1]北京科技大学土木与资源工程学院,北京100083 [2]中国冶金地质总局矿产资源研究院,北京101300 [3]锡林郭勒盟山金白音呼布矿业有限公司,内蒙古锡林浩特026316

出　　处：《岩石矿物学杂志》2022年第6期1120-1134,共15页Acta Petrologica et Mineralogica

基　　金：山东黄金集团项目;中国地质调查局项目(DD12120113056700);中国冶金地质总局科技创新项目(CMGB202002)。

摘　　要：迪彦钦阿木钼矿床位于内蒙古东乌旗地区,矿区侵入岩不发育,主要为细粒正长岩和基性岩脉,矿体主要发育在侏罗纪火山岩中,少量发育在细粒正长岩中,主要矿化类型为细网脉状、脉状、浸染状,具有斑岩型矿化特征。矿区的细粒正长岩中可见含矿石英-钾长石囊团或由之构成中心相的热液脉体,是岩浆-流体转化过程的直接证据。本文在详细岩相学观察的基础上,对石英-钾长石囊团中主要组成矿物开展了阴极发光图像分析,对石英、萤石中流体包裹体开展了显微测温实验,并借助SEM/EDS、显微激光拉曼探针、LA-ICP-MS等手段对包裹体成分进行了系统分析,基于以上实验结果对岩浆流体的出溶过程、出溶流体特征及矿质沉淀机制进行了探讨。研究结果表明,矿区钼成矿与细粒正长岩岩浆出溶流体有关;富F和挥发分造成成矿岩浆具有低的固相线温度和较低的黏度,因此成矿岩浆可以沿断裂快速上侵到地壳浅部;岩浆上侵过程中的减压沸腾可能是流体出溶的主要机制;早期出溶流体为富F和富CO_(2)的中高温(227~457℃)、中低盐度[w(NaC_(leq))=0.3%~8.6%]流体,由于快速减压造成流体沸腾形成低盐度富CO_(2)的气相和高盐度液相,沸腾引起的CO_(2)逃逸可能是矿质沉淀的主要原因。The Diyanqin’amu Mo deposit is located in Dong Ujimqin Banner,Inner Mongolia.The barely exposed intrusive rocks in this deposit are mainly composed of fine-grained syenite and mafic dikes.The Mo mineralization predominantly occurs in Jurassic volcanic rocks with minor in fine-grained syenite veins,mainly including veinlet,vein and disseminated mineralization types.Ore-bearing quartz-potassium feldspar-fluorite miarolitic cavities or hydrothermal veins with these minerals in the center are identified in the fine-grained syenite,which are direct evidence for exsolution of magmatic fluids.In this study,based on detailed petrographic observation,we conducted cathodoluminescence imaging for main minerals in the quartz-potassium feldspar-fluorite miarolitic cavities,microthermometry for fluid inclusions in quartz and fluorite,and compositional analysis for fluid inclusions using SEM/EDS,LRM and LA-ICP-MS.On the basis of above analyses we discussed the process of fluid exsolution,features of initial ore-forming fluids and precipitation mechanism of ore minerals.Our results show that the Mo mineralization was genetically related to the magmatic fluids derived from fluid exsolution of the fine-grained syenite.Enriched fluorine and other volatiles decreased the solidus and viscosity of the ore-related magma,which enabled rapid upwelling of this melt to the shallow upper crust via faults.Rapid decompression during ascent was probably the major mechanism for fluid exsolution of magma.The initial magmatic fluids were F-and CO_(2)-riched fluids with medium-high temperature(227~457℃)and medium-low salinity[0.3%~8.6%,w(NaC_(leq))].The initial magmatic fluids separated into a CO_(2)-riched gas phase with low salinity and a liquid phase with high salinity owing to boiling caused by rapid decompression.Therefore,the escape of CO_(2)caused by boiling was probably the main reason for molybdenite precipitation.

关 键 词：迪彦钦阿木 流体包裹体 LA-ICP-MS 斑岩型钼矿床 流体出溶 

分 类 号：P611.1[天文地球—矿床学]