城步铺头黄铁矿床再研究

位于湖南中部的城步铺头黄铁矿床，是产于泥盆系基维特阶的层状矿床，1984年作者在本刊报导过这个矿床的沉积环境。根据新的资料，再次对它的成因进行研究。该矿床位于华南古大陆边缘裂谷系的北东向深水盆地中，含矿岩系由暗色的硅质岩-泥灰岩组成，矿体呈层状整合产出，以黄铁矿为主，硫同位素以富含32S为特点（δ34S＝-17．4‰～-30.10‰）。含矿岩系及矿石中，有机质含量较高（3％～5％），有机质类型为腐殖-腐泥混合类型，成熟度较高。矿石具致密块状及条带状构造，由大量草莓状黄铁矿组成，它们主要出现在致密块状矿石中。矿石及含矿围岩的稀土元素、微量元素组成，与现代大洋裂谷或隆起区中的热液沉积物的特征相似，表明它们具有相同的来源和成因，应属海底热液喷流沉积矿床，大量存在的有机质，对于矿床的形成也起了重要的作用。

Restudy on the Putou Pyrite Ore Deposit

The Putoupyrite ore deposit, formed in Givetian of Devonian, is a medium-scale stratiform deposit in Chengbu County of Hunan Province, China. The author reported its sedimentary environment in the present journal in 1984, and in this paper its genesis was discussed based on new data. This deposit is located in a N E deep water basin which developed in the rift system of the South China palaeocontinent margin. The ore-bearing section consists of dark siliceous rock and mar1. The ore beds are stratiform and conformably deposited in the synchronous strata. The ore is composed of only pyrite with massive and banded structures. The composition of sulfur isotope is rich in 32S, and its variation range is from -17.4‰ to -30.1‰. The ore-bearing rock and ore are rich in organic carbon, which is sapropel-humic type with higher maturity. Charateristics of the ore texture are widespread framboidal pyrite that consists of micrograined pyrite (d < 1μm) with different crystal forms and ordered or disordered structures, some framboidal pyrite appears massively with pyrite crystal in dense ores . Charateristics of REE and trace element s in the ore and hsted rocks, which conform with the mordern hydrothermal deposits of oceanic rift or rise in the pacific, suggested that their origin is the same. For this reason, the Putoupyrite deposit is a sedexore deposit and its abundant organic matter plays an important role in ore deposits.