新疆阿尔泰巴特巴克布拉克铁矿床硫同位素和稀土元素地球化学特征及其意义

A study of S isotope and REE geochemistry of Batebakebulake iron deposit in Altay, Xinjiang, and their geological significance

新疆阿尔泰巴特巴克布拉克铁矿床赋存于上志留统下泥盆统康布铁堡组变质火山-沉积岩的矽卡岩中,矿体形态复杂,呈似层状、透镜状及不规则状分布。围岩斜长角闪岩、变粒岩和浅粒岩稀土元素配分模式为轻稀土元素相对富集的右倾型,与矿区英云闪长岩稀土元素配分模式相似;矿石和矽卡岩稀土元素配分模式多表现为重稀土元素相对富集的左倾型,综合了围岩和英云闪长岩二者的特征,表明它们之间有明显的成因联系。结合硫同位素特征(1.4‰~4.8‰)表明,成矿物质来源于基性火山岩(围岩)。矽卡岩为花岗质岩浆期后热液交代火山岩的产物,铁矿化是矽卡岩退化蚀变的产物,矿床形成于弱还原-氧化环境。

The Batebakebulake iron deposit in the Altay Orogenic Belt of Xinjiang is hosted in the metamorphosed volcano-sedimentary sequence of the Upper Silurian-Lower Devonian Kangbutiebao Formation.Orebodies occur as stratoid,lenticular and irregular forms,and their distribution is spatially associated with skarns.The REE geochemical characteristics show that the wall rocks(amphibolite,leptynite,leucoleptite)in the ore district have similar chondrite-normalized REE patterns which show enrichment of LREE,similar to those of the tonalite,suggesting that wall rocks have a clear genetic link with the tonalite.In addition,most of the ores and skarns have similar chondrite-normalized REE patterns which show enrichment of HREE.The δ34S values of sulfides range from 1.4‰to 4.8‰,with an average of 3.57‰.The S isotopic data,together with REE geochemical characteristics,indicate that the metallogenic material was derived from the basic volcanic rocks.The skarn probably resulted from the interaction of post-magmatic hydrothermal fluids with volcanic rocks,and the formation of magnetite was associated with the retrogressive metamorphism of the skarn.The deposit was formed in a weak reducingoxidizing environment.