辽宁歪头山铁矿床两类矿石地球化学特征及其对成矿作用的制约

歪头山铁矿床是鞍山-本溪地区条带状铁建造（BIFs）的典型代表，并且有一定规模的富铁矿分布。本文主要报道了矿区内较贫铁矿石和较富铁矿石的地球化学特征，结果表明两类矿石既有一致性又存在差异性。一致性表现在：所有矿石主要由TFe2O3和SiO2组成，其他氧化物含量很少，结合微量元素和稀土元素特征，指示其为一种化学沉积岩，但受到了火山热液作用的影响；矿石的稀土元素总量很低，经太古界后平均澳大利亚页岩（PAAS）标准化后，呈现重稀土相对富集，轻稀土相对亏损的配分模式，都具有明显的Eu正异常，和比较高的Y/Ho比值，与热液相关的Cr、Co、Ni含量也相对较高，暗示其成矿物质来源于海底热液，同时具有海水的特征。差异性表现在：较富铁矿石具有明显的热液特征，并且K2O含量大于Na2O含量，某些微量元素组成也与混合花岗岩具有相似性，结合野外地质特征，暗示较富铁矿石可能是在较贫铁矿石的基础上受混合岩化热液作用形成的。

Geochemical characteristics of two types of iron ore from Waitoushan iron deposit,Liaoning province: constraints on ore-forming

The Waitoushan iron deposit is a typical deposit of banded iron formations(BIFs) in Anshan-Benxi area,and which has a certain size and high grade iron ore. Geochemical characteristic of iron ore from studied area are reported in this paper, the results reveal that both similarities and distinctions exist in leaner iron ore and higher grade iron ore. Here the similarities:All ores composed of TFe2O3 and SiO2, other oxidate is very low, combine with characteristics of trace and rare elments, suggest that the iron ore from Waitoushan iron deposit is a chemical sedimentary rock, and influenced by volcanic hydrothermal;The total concentrations of REE of iron ore is very low, the normalized by Post Archean Australian Shale(PAAS) REE+Y patterns display depletion of light REE relative to high REE, all have distinct Eu positive anomalies and high Y/Ho ratios. And it has higher concentrations of ferromagnesian trace elements relatively, such as Cr,Co and Ni. Trace and REE data suggest that iron is deep sea hydrothermal origin with seawater signatures. However,there are also some differences between them,compared with the leaner iron ore,the higher grade iron ore shows more distinct hydrothermal signatures.The contents of K2O is higher than Na2O, and some trace elments composition are also similar with granitization granite.Combining with field geological characteristics,those may suggest that the higher grade iron ore may be formed by leaner iron ore though activities of migmatization hydrothermal.