辽宁南芬露天铁矿床地球化学特征及其地质意义

Geochemical Characteristics and Geological Significance of Iron Deposit in Nanfen, Liaoning

辽宁南芬铁矿是中国乃至亚洲最大的露天开采铁矿。自1949年以来,辽宁南芬铁矿一直是本钢集团的主体矿山和高品位富矿的主要供应地。本文在总结辽宁南芬铁矿床成矿地质背景及矿床地质特征的基础上,对矿区内的磁铁石英岩的主量元素和稀土元素特征进行分析。通过主量元素和稀土元素相结合的方法,对铁矿成矿物质来源提出了有效制约。研究表明,条带状铁矿(BIF)的化学成分主要由T(Fe2O3)和SiO2组成,并且具有较低含量的Al2O3和TiO2。这一特征与鞍-本地区、山西五台山和冀东迁安地区铁矿一致,表明该BIF型铁矿是由极少碎屑物质加入的化学沉积岩。稀土元素的总量很低,经标准化后的稀土元素配分模式呈现轻稀土亏损、重稀土富集的特征,具有明显铕(Eu)正异常特征,说明该BIF的地球化学特征(REE)来源于火山热液和海水混合液。

The Nanfen iron deposit is the largest open-pit iron deposit not only in China but also in Asia. Since 1949, it has become the main mine to provide high grade iron for the Benxi Steel Iron Cooperation. This paper discusses the geological background of the mineralization the geological characteristics and the major and rare earth elements in the Nanfen iron deposit. The major and rare earth elements （REE） of banded iron formations are analyzed and it is shown that the average bulk compositions of banded oron formations （BIF） are rich in Fe and SiO2, but with very low Al2O3 and TiO2 contents, as consistent with the characteristics in Anshan-Benxi, Wutaishan and Qianshan. These chemical features show that they are chemical sediments of detrital input, with very low REE concentrations, with the shale-normalized REE patterns of distinct positive anomalies of Eu and the depletion of light REE relative to heavy REE. This demonstrates that the BIFs are the products of chemical sedimentions from the paleo-seawater with significant input of volcanic hydrothermal fluids.