新疆西天山智博铁矿床火山岩和侵入岩岩石地球化学  

Geochemistry of volcanic and intrusive rocks in Zhibo iron ore deposit of western Tianshan Mountains

作　　者：田敬佺 段士刚[3] 彭万林[2] 李明[2] 蒋宗胜[3] 严瑞[2] 

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]新疆地质矿产勘查开发局第三地质大队,新疆库尔勒841000 [3]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》2015年第1期119-138,共20页Mineral Deposits

基　　金：国家重点基础研究发展计划(编号:2012CB416803);地质矿产调查评价项目(编号:1212011085060;1212011090300);国家自然科学基金资助项目(编号:41203035)联合资助

摘　　要：新疆西天山阿吾拉勒山集中产出多个大、中型海相火山岩型富铁矿床,引起人们的广泛关注。这些铁矿的成因被认为与火山作用有关,但对其成岩成矿的大地构造背景尚不清楚。文章研究了智博铁矿区出露的火山岩和侵入岩的岩石学、岩石地球化学,尝试探讨该问题。智博铁矿体赋矿围岩为早石炭世大哈拉军山组玄武岩和安山岩,侵入岩有晚石炭世花岗岩、花岗岩脉和闪长岩脉。玄武岩和安山岩在构造环境判别图解中投影于火山弧范围内,在花岗岩类构造环境判别图解中,320 Ma的花岗岩脉和319 Ma的石英闪长岩投影于岛弧环境,304 Ma的花岗闪长岩则投影于同碰撞环境。结合前人研究成果,认为智博地区在早石炭世为岛弧环境,晚石炭世可能经历了岛弧俯冲向同碰撞环境的转变。玄武岩亏损Ta、Nb,相对亏损Th,富集Rb、U、Pb;安山岩亏损Ta、Nb,富集轻稀土元素和Rb、U、Th、Pb,结合Sr/Th-Th/Ce和Th-Ba/Th图解判别,推测智博铁矿床玄武岩和安山岩岩浆源区为受到了俯冲带流体交代的楔形地幔。A number of large and medium-sized submarine volcanics-hosted iron-rich ore deposits were discovered recently in the Awulale Mountain, western Tianshan Mountains. These iron ore deposits are considered to be genetically related to volcanism. However, the tectonic setting for the volcanism and iron mineralization remains uncluear. The Zhibo iron ore deposit is hosted in basalts and andesites of the Lower Carboniferous Dahalajunshan Formation. The volcanic rocks were intruded by Late Carboniferous granite, granitic dykes and dioritic dykes. Samples of basalt and andesite fall in volcanic arc region in the tectonic discrimination diagrams, whereas samples of granite, granitic dykes and dioritic dykes fall in volcanic arc and / or syn-collision environment in the tectonic discrimination diagram for granitoids. Combined with previous researches, this paper argues for an island arc setting in Early Carboniferous and a transition from island arc to collision in Late Carboniferous for the Zhibo deposit. Basalt samples are depleted in Ta and Nb, relatively depleted in Th, but eniched in Rb, U and Pb. Andesite samples are depleted in Ta and Nb, but enriched in light REE and Rb, U, Th and Pb. Combined with Sr / Th versus Th / Ce and Th versus Ba / Th diagrams and other geochemical data, the authors hold that the magma source for basalt and andesite was mantle wedge metasomatized by subduction-related aqueous fluids.

关 键 词：地球化学 海相火山岩型铁矿 大地构造环境 智博铁矿床 西天山 

分 类 号：P618.31[天文地球—矿床学]