ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    印度达尔瓦尔克拉通绿岩带BIF型铁矿地质特征及成因分析

    Geological Characters and Genesis Analysis of Greenstone-type BIF Iron Deposits in Dharwar Craton, India

    • 摘要: 印度铁矿储量约占全球的7%,矿石类型以前寒武纪BIF铁矿为主,其中产于绿岩带以及绿片岩相岩石中的BIF型铁矿是印度最重要的铁矿类型。南印度地盾达尔瓦尔克拉通发育众多绿岩带,绿岩带中发育大规模BIF铁矿,BIF铁矿属于不同的地层序列,有不同的岩石组合关系。笔者对吉德勒杜尔加绿岩带和库斯赫塔吉绿岩带BIF地球化学分析表明,根据Al2O3含量,BIF分为页岩BIF(Al2O3≥2%)和石英岩BIF(Al2O3≤2%),BIF呈石英氧化物相,碳酸盐相和硫化物相BIF主量和微量元素表明BIF为陆源碎屑沉积和火山碎屑沉积共同作用形成;稀土元素表明BIF铁矿呈Ce负异常和Eu正异常。达尔瓦尔克拉通测年数据表明,经过2.7~2.65 Ga和2.58~2.54 Ga两期主要的火山作用,2.7~2.6 Ga和2.58~2.52 Ga 2个阶段的大陆增生作用,形成了达尔瓦尔克拉通和绿岩带。BIF成矿来源上,AMOR的高温热液提供大量的Fe和SiO2,海洋中生物光合作用提供了O2,在化学沉积和碎屑沉积共同作用下,形成了BIF铁矿。

       

      Abstract: India takes up about 7% of iron ore reserves in the world, which is dominated by Precambrian BIF iron. In which, the BIF iron ores occurred within greenstone belt or green schist serve as the most important type of iron deposits in India. The greenstone belts were well developed in Dharwar Craton and South India Shield, where a lots of BIF iron deposits were developed in different strata sequences and rock association.The geochemical characters of BIF deposits in Chitradurga and Kushtagi greenstone belts have been analyzed and discussed in this paper. The results show that these BIFs can be classified into shaleand quartz BIFs by using the limit of 2% Al2O3 content. And these BIFs show three lithofacies, such as quartzoxide, carbonate or sulfides phases. The major and trace elements geochemistry show that these BIFs were formed by the joint action of terrigenous clastic and volcanic clastic sedimentary. The rare earth elements geochemistry shows that these BIFs have negative Ceanomalies and positive Eu anomalies.The dating data of Dharwarcraton suggest that two major volcanisms occurred in 2.7~2.65 Ga and 2.58~2.54 Ga, and two stages continental accretions happened in 2.7~2.6 Ga and 2.58~2.52 Ga, which caused the formation of Dharwarcraton and related greenstone belts. As for the ore-forming materials source of these BIFs deposits, the Feand SiO2 were came from the high-temperature hydrothermal of AMOR, the O2 was sourced from marine biological photosynthesis, and these BIF deposits were formed by the combined action of chemical and clastic sediments under this environment.

       

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