“新余式”铁矿地质特征及其成因

GEOLOGICAL FEATURES AND ORIGIN OF THE XINYU TYPE IRON DEPOSITS

“新余式”铁矿是华南重要的铁矿类型之一,也是我国最年轻的硅-铁建造型铁矿之一。本文在系统的野外和空内调研基础上,阐述了其岩石学、岩石化学、副矿物、微量元素及矿石的组成、组构等特征。研究认为成矿物质来源于远源火山,其成矿作用为沉积的(后期受变质),因而确定其为一种“远火山-沉积变质铁矿”。

The Xinyu type iron deposits occur extensively in Guangxi, Jiangxi and Hunan, and extend continuously or discontinuously for about a thousand kilometers, serving as one of the important iron types in South China. Distributed in Caledonian geosynclinal system in South China, the iron deposits were formed between the two ice ages in Si(?)ian which are known to be 740-700 Ma.he iron formation consists of a series of metamorphosed volcanic-sedimentary rocks. Based on researches in such aspects as field and thin section observations, geochemical features, accessory minerals and minor element characters, it is considered that the rock-forming and ore-forming materials came mostly from volcanic activities, and this is supported by the disvovery of volcanic debris-shaped magnetite in the ores. Nevertheless, there exists a strict sequence of minerals in upward succession of specularite, magnetite→chlorite(biotite)→siderite→pyrite(pyrrhotite). This sequence indicates a perfect sedimentary differentiation. Therefore, the iron deposits of Xinyu type are believed to be volcanism-sedimentation in origin.