江西新余式铁矿地质地球化学、Fe同位素特征及其地质意义

Abstract

本文对江西新余地区“新余式”铁矿成矿的区域地质背景、矿化地质条件特征、矿石共生组合特征和矿石主微量元素含量以及铁同位素进行了分析。认为该区铁成矿以化学沉积建造为主，同时伴有诸多陆源碎屑物加入，显示成矿物质来源多样，成矿环境复杂。铁同位素分析结果显然新余铁矿富集铁的重同位素的矿物相。各区段同位素值的差异性显示该区不同的氧化还原状态的演化变化状态。重铁同位素富集和Ce异常缺失等特征指示成矿期为低氧逸度环境，新余式铁建造形成于地球冰盖开始融化初期，冰川溶化后大量悬浮细碎屑物质的淡水加入，出现大量氢氧化铁和胶体SiO2先后或同时沉积，形成含铁硅建造，后来再遭受区域变质、挤压变形等地质作用，使氢氧化铁脱水和重结晶变成磁铁矿，胶体SiO2变成石英，原来的隐晶质的铁质燧石岩变成磁铁石英岩，形成现在的新余铁矿BIF标志层。 In this paper, the regional geological background, mineralization geological characteristics, ore symbiotic combination characteristics and main and trace element content and iron isotope of Xinyu type iron ore mineralization in Xinyu area of Jiangxi Province were analyzed. It shows that the iron ore deposits mainly composed of chemical deposition, accompanied by a number of terrestrial debris to join, which show that the mineral resources are diverse and the mineralization environment is complicated. Iron isotope analysis results are clearly enrichment of iron heavy isotope mineral phase. The difference in the isotopic values of each segment shows the evolutionary state of the redox state of the region. Heavy iron isotope enrichment and Ce anomaly and other characteristics indicate that the ore-forming period is a low-oxygen fugacity environment. The iron is formed at the beginning of the melting of the Earth’s ice sheet. At the beginning of the melting of the glacier, with the lots of fine clastic and freshwater, there are lots of colloidal ferric hydroxide and SiO2 deposited in succession or simultaneously to form formation of iron-containing silicon construction. After this, the formation subjected to regional metamorphism, deformation and other geological effects, the dehydration and recrystallization make Fe(OH)3 into magnetite, and colloid SiO2 into quartzite. Ultimately, the original aphanitic iron flint Shiyan transforms magnetite quartzite, finally, form the current Xinyu iron ore BIF marker layer.