安徽姑山矿浆型铁矿床Fe同位素初步研究  

Preliminary Fe isotopic study of Gushan ore magma deposit in Anhui Province

作　　者：王跃[1] 朱祥坤[1] 毛景文[2] 程彦博[2] 

机构地区：[1]中国地质科学院地质研究所国土资源部同位素地质重点实验室,大陆构造与动力学国家重点实验室,北京100037 [2]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037

出　　处：《矿床地质》2014年第4期689-696,共8页Mineral Deposits

基　　金：国家自然科学基金项目(编号:41203006);国土资源公益性行业专项经费项目(编号:201011027;201311144);国家重点基础研究发展计划项目(编号:2012CB416806)联合资助

摘　　要：文章报道了宁芜矿集区内姑山矿浆型铁矿床中的铁氧化物、辉石闪长玢岩和赋矿围岩的Fe同位素组成,其δ57Fe的总体分布范围为-0.05‰～0.79‰.结果显示,姑山铁矿床的铁氧化物赤铁矿和镜铁矿均比硅酸盐岩浆结晶产物（辉石闪长岩）富集重的Fe同位素,并且硅酸盐岩浆的Fe同位素组成比已报道的火山岩的平均Fe同位素组成更富集轻的Fe同位素,表明在岩浆不混溶的过程中Fe同位素发生了分馏,富铁熔体相对富集重的Fe同位素,而硅酸盐熔体相对富集轻的Fe同位素;相对于赋矿地层（黄马青组石英砂岩）和辉石闪长玢岩,赤铁矿和镜铁矿更富集重的Fe同位素,围岩地层和闪长岩岩体则富集轻的Fe同位素.因此,姑山铁矿床的铁质不大可能来自于地层或闪长玢岩岩体,而主要来源于深部岩浆房.Fe isotope compositions of Fe-oxide minerals and pyroxene-diorite porphyry as well as ore-hosting wall rocks from the Gushan ore magma deposit in Anhui Province are reported in this paper. An overall variation in 357Fe values from - 0.05%0 to 0.799＇oo has been observed. Fe-oxide minerals have higher 357Fe values than pyroxene- diorite porphyry, whereas the pyroxene-diorite porphyry is slightly enriched in light iron isotopes relative to average Fe isotopic composition of igneous rocks reported both in China and abroad, indicating that Fe isotope fractionation occurred during the process of fluid immiscibility. Fe-rich melts are enriched in heavy Fe isotopes while Fe-poor silicate melts are enriched in light Fe isotopes. Moreover, Fe isotope compositions of Fe-oxide minerals, pyroxene-diorite porphyry and wall-rock are comparatively studied. Both pyroxene-diorite porphyry and wall rocks have lower 647Fe values than the Fe-oxide minerals, and the Fe isotopes distribution characteristics are consistent with melt immiscibility and also accordant with the basic theory of Fe isotopic fractionation, suggesting that the Fe in the Gushan iron deposit was most probably derived from deeper chamber rather than from strata and pyroxene-diorite porphyry. Field observations and Fe isotopic studies conducted by the authors strongly suggest that the main orebodies in the Gushan deposit were subjected to ore-magma type mineralization.

关 键 词：地球化学 FE同位素 岩浆不混溶 矿浆 姑山铁矿 

分 类 号：P618.31[天文地球—矿床学] P597[天文地球—地质学]