山西省岚县袁家村铁建造的沉积相和形成条件分析

AN ANALYSIS OF THE SEDIMENTARY FACIES AND THE FORMATION CONDITION OF THE YUANJIACUN IRONFORMATION LANXIAN COUNTY SHANXI PROVINCE, CHINA

山西省岚县袁家村铁矿为产于下元古界吕梁群袁家村组的沉积变质层控铁矿。山西省地质局218地质队、区调队、岚县铁矿会战指挥部、215地质队等单位,先后在该区做了大量的地质工作,取得了很多的地质成果。我们在前人工作基础上,对9线以南铁建造的沉积相和形成条件开展了一些工作,提出了初浅的看法。谬误不当之处,希批评指正。

The Yuanjiacun iron ore deposit is a sedimentary-metamorphic deposit occurring in the Yuan-jiacunFormation.Luliang Group,of the early Proterozoicera.The Yuanjiacun Formation is an iron-bearing sedimentary rock series metamorphosed into greenschist facies. Its main rock types are metamorphic quartz sandstone, sericite phyllite, chlorite schist, ferriferous-siliceous and carbonate rocks. The thic-kness of the Formation is about 1479M,anb is divided into 3 sedimetary-minerogenic cycles. The iron ore is mainly occurred in the middle-lower part of the Formation.On th beasis of the main original iron minerals, the sebimentary iron-formation can be divibeb into oxide, silicate, carbonate and sulfide facies. The oxide facies consists of two main subfacies, one characterized by hematite and the other by magnetite, with the magnetite subfacies in dominance. Facies change in the iron-formation is clear.The iron-formation was deposited in a gulf-lagoon enviroment of a restricted basin. Most of the rocks were deposited under the condition of middle or low water kinetic energy. The iron material came not only from the terrigneous deposit, but also from sea floor volcanic emanation.lt was even possible that part of the iron material came from the ocean floor. The iron material was transported in the form of Fe (OH)3, Si (OH)4 colloiid and Fe++ solution.The orginal deposit was probably a mixture of inon-sillica gels, mineral particles anb volcanic material. The primary sediment had u nber-gone diagenetic anb greenschist facies metamorphism. The Yuanjiacun iron-formation may belong to the type of carbonate-shale-chert formation, similar to the Supeior ore deposit.