岩石矿物学杂志2012，Vol.31Issue(2)：191-211,21.
新疆西天山查岗诺尔铁矿床矿物学特征及其地质意义
Mineralogy of the Chagangnuoer iron deposit in Western Tianshan Mountains,Xinjiang, and its geological significance
摘要
Abstract
Located in the eastern Awulale metallogenic belt of Western Tianshan Mountains, the large-size Cha-gangnuoer iron deposit is hosted in andesitic volcaniclastic rocks or andesitic tuff of the Lower Carboniferous Da-halajunshan Formation, with a lenticular marble beneath the main ore body. The ore bodies occur as lamellar, stratoids and lenses, controlled by NW-, NWW- and NEE- striking faults and circular faults. Mineralizations occur along the fissures and fractures in the wall rocks. This ore deposit is composed of two major ore bodies, I. E., FeI and FeII. The FeI ore body strikes NE-SW, about 2 900 m in length, 63 m in average thickness, with Fe average grade of 36.87% and ore reserves of more than 190 million tons. Wall rock alterations includechiefly garnetization, actinolitization, chloritization, epidotization etc. Ore minerals consist mainly of magnetite and subordinated pyrite and chalcopyrite while gangue minerals are composed of garnet, actinolite, chlorite, epidote, tremolite, and calcite. Electron microprobe analyses show that the end member of garnet is andradite (Adr) with an average content of 61.58 %, grossularite (Grs) with an average content of 35.45 %, and alman-dite (Alm) with an average content of 2.48%. The composition of pyroxene is dominated by diopside (Di, 54.22% on average) and hedenbergite (Hd, 44.22% on average), with a small amount of johannsenite (Jo, less than 5.53%). Components of garnet and pyroxene are Adr37.97~97.89Grs0.19~57.21 (Aim + Sps)0.84~4.38, Di28.68~87.46Hd10.46~70.13.Jo0.24~5.53, which indicates that 0 characteristics of these two skam minerals are quite similar to those in calcic skam from the major large iron deposits, suggesting that they probably resulted from skarnization; (2) their wide and different compositions reveal that skarns were not formed under a wholly closed equilibrium condition. Epidote is rich in Al and Ca but poor in Fe and Mg, implying that Fe and Mg were separated from each other at the time when pyroxene was converted into epidote. The chemical compositions of magnetite are rich in Mg, Mn, Ca, Si but poor in Al, Ti, Ni, exhibiting a similar feature to those formed in calcic skarn iron deposits. In the Ca + Al + Mn versus Ti + V discriminant diagram showing spot analyses of magnetite and hematite, almost all data from the Chagangnuoer ore deposit fall into the region of the skarn type iron deposit. In addition, in the ternary plot of TiO2- Al2O3- MgO of magnetite, many data from the Chagangnuoer ore deposit tend to be seated in the sedimentary metamorphogenic and contact meatasomatic region while less data drop into magmatic mafic-ultramafic region. These two diagrams may suggest that the formation mechanism of magnetite from this ore deposit may be similar to that of magnetite from skam iron deposits. Combining the geological characteristics with the study of mineralogy, the authors hold that iron mineralization was related to skarnization, and that skarnization might have played an quite important role in the formation of the Chagangnuoer iron ore deposit.关键词
西天山/查岗诺尔/铁矿床/电子探针分析/矽卡岩/磁铁矿Key words
Western Tianshan/ Chagangnuoer/ iron deposit/ electron microprobe analysis/ skarn mineral/ magnetite分类
天文与地球科学引用本文复制引用
洪为,张作衡,赵军,王志华,李凤鸣,石福品,刘兴忠..新疆西天山查岗诺尔铁矿床矿物学特征及其地质意义[J].岩石矿物学杂志,2012,31(2):191-211,21.基金项目
国家重点基础研究发展计划(2012CB416803) （2012CB416803）
国家科技支撑计划(2011BAB06B02) （2011BAB06B02）
地质矿产调查评价项目(1212011085060) （1212011085060）
