尼新塔格铁矿床所属的西天山阿吾拉勒成矿带赋存有多个中-大型铁矿,近年来这些铁矿床的成因类型以及它们之间的联系已成为该地区的一个研究热点.为了探讨尼新塔格铁矿床的矿床成因并进一步揭示其成矿过程,本文对该矿床进行了系统的矿物学、岩石学、岩相学及地球化学研究.工程勘探资料显示该矿床赋矿围岩主要为下石炭统大哈拉军山组玄武粗面安山岩、粗面安山岩及安山质火山碎屑岩.根据对围岩蚀变、矿石组构、矿物共生组合的观察,将矿床的形成过程划分为矿浆期和热液期两个主要成矿期.稀土、微量元素地球化学特征显示尼新塔格铁矿区内的矿石与熔岩围岩具有同源性.岩相学及地球化学研究表明,成矿物质主要来源于岛弧环境下形成的玄武质岩浆.综合以上特征,认为尼新塔格铁矿床是由石炭纪岛弧环境下形成的玄武质岩浆分异演化的产物,在成因类型上应属火山岩型岩浆-热液复合成因磁铁矿矿床.
The Nixintage magnetic iron deposit is situated in the east Awulale metallogenic belt,western Tianshan Mountains,Xinjiang.Several large-sized and medium-sized iron deposits have been found in this belt,and their genetic types as well as the contact relationship between them have become problems of heated debate in this area.A series of systematic researches have been conducted to discuss the ore genesis.Stratigraphic study and drilling projects reveal that the orebodies are hosted in basaltic trachyandesite,trachyandesite and pyroclastic rocks of Lower Carboniferous Dahalajunshan Formation,which contain 3 main iron orebodies.They are all concealed orebodies and occur in bedded and stratoid forms.Ore structures mainly include disseminated type,brecciated type,massive type and striped type.The main ore mineral in the iron ore is magnetite,followed by hematite,with minor pyrite and limonite and occasional geikielite.The main altered minerals in the wall rocks include chlorite,epidote and carbonate.On the basis of the study of ore fabric and paragenetic association of minerals,the metallogenic stages of the Nixintage iron deposit can be divided into two periods:magmatic metallogenic period and hydrothermal period.The orebodies and their wall rocks have similar chondrite-normalized REE patterns and rich LREE.The orebodies and their wall rocks also have similar trace elements characteristics,relatively rich in Th as well as U and poor in Nb,Ta and Sr.REE and trace elements charactersitics show that they are homologous.The study of petrography demonstrates that orebodies and their wall rocks are products of a developed basaltic magma rather then the products of andesitic magma.The general negative anomalies of Nb,Ta in the orebodies as well as their wall rocks and the negative anomalies of Ti in the wall rocks show that the oreforming parental magma was probably the basaltic magma formed in an island-arc environment.In conclusion,the Nixintage magnetic iron deposit resulted from differential evolution of basaltic magm