岩石热液蚀变作用过程元素的活动性——河南祁雨沟金矿Ⅳ号岩体蚀变花岗斑岩的研究  

Element mobility during the fluid-rock hydrothermal alteration: Evidence from altered porphyritic granite in Ⅳ pipe of the Qiyugou gold deposit,Henan Province

作　　者：祁冬梅[1] 周汉文[1,2] 宫勇军[3] 熊索菲[3] 贾耽 张金 张旻玥[1] 

机构地区：[1]中国地质大学地球科学学院,武汉430074 [2]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074 [3]中国地质大学资源学院,武汉430074 [4]湖北省核工业地质局,孝感432099

出　　处：《岩石学报》2015年第9期2655-2673,共19页Acta Petrologica Sinica

基　　金：全国危机矿山接替资源找矿项目(20089939);国家自然科学基金项目(90814004)联合资助

摘　　要：本文以河南省祁雨沟金矿Ⅳ号角砾岩体不同中段(标高340m以上)的蚀变花岗斑岩角砾为研究对象,对其蚀变过程中主量、微量元素的活动性进行了深入探讨。通过与地表新鲜花岗斑岩的矿物学和地球化学对比显示,从深部到浅部的蚀变花岗斑岩角砾经历了早期钠长石化、中期钾长石化和晚期黄铁绢英岩化三个阶段的蚀变作用,元素的行为也发生了相应的变化,具有显著的正Eu异常,Zr、Hf富集而Nb、Ta、Y强烈亏损等特点。引发热液蚀变的流体体系是碱性的、浅成低温的和低硫的,迁入了大量的Mg、P和LOI,并将Mn、Co和Zn活化转移出体系。该流体的pH由最初的碱性逐渐向酸性转变,碱性流体将成矿元素Au、Cu、Pb、Zn和稀土元素活化转移至酸性介质中沉淀富集,因此钠长石化、钾长石化和黄铁绢英岩化蚀变作用可作为金矿床重要的找矿标志。The effects of hydrothermal alteration on major and trace element in porphyritic granite of the Ⅳ breccia pipe of Qiyugou gold deposits,Henan,were invested by statistically comparing the chemical compositions of altered drill cuttings（ taken above 340 m depth） with those of fresh rock outcrop samples. Based on mineralogical and geochemical studies,three successive alteration stages have been identified from the top down by time（ an early albitization,a middle K-feldsparization and a later pyritic-phyllic alterzation zone） with notable differences in major,REE and other trace elements behavior. Altered porphyritic granite show prominent positive Eu anomaly,whereas HFSE were mobiled as Zr, Hf were enriched and Nb, Ta, Y were significantly depleted. Therefore, the hydrothermal systems were alkalic,epithermal and low-sulphidation system,and a large proportion of Mg,P,LOI were externally supplied and Mn,Co,Zn were impoverished during these hydrothermal process,then the fluid turns out to be more acidic. The primal alkaline fluid tended to leach ore forming elements（ Au,Cu,Pb,Zn） and REEs,and precipitated them into acidic alteration zone,so the study of the mobility of elements during hydrothermal alteration of granitic porphyry may play an important role in ore exploration.

关 键 词：热液蚀变 浅成低温 低硫 祁雨沟金矿 河南 

分 类 号：P588.121[天文地球—岩石学]