摘要
宁芜火山断陷盆地是长江中下游一个典型的黄铁矿化集中区,成矿作用与燕山晚期龙王山和大王山旋回火山侵入活动有关,黄铁矿床主要分布于盆地中部和东缘两条基底隆起带上。矿床硫同位素组成以数值分散富重硫为特征,类似于海水硫酸盐高温无机还原作用所形成的硫化物。矿床在空间上与中三叠统膏盐层关系密切,在时间上晚于该层成矿。本文认为,区内黄铁矿在成因上与石膏层有关。岩浆中的Fe^2+作为还原剂将CaSO_4还原为H_2S,为成矿提供丰富的硫源,故原始中间岩浆房相对膏盐层的空间位置,是控制富硫区与贫硫区的关键因素。据此进行矿床的成矿区划,并提出3个找矿有利地段。
Ningwu faulted volcanic basin is a typical pyrite-concentrated district in the areaalong lower and middle Yangzi River.The ore-forming processes are related to theintruso-extrusive activities of Longwangshan and Dawangshan volcanic cycles inYanshan Tectonic Epoch.The pyrite deposits are chiefly distributed along twobasement horsts on the centre and eastern margin of the basin,respectively.Pyriteisotopic composition is scattered and rich in ^(34)S,similar to that of sulfides originatedfrom high temperature inorganic reduction of seawater sulfate.The pyrite deposits,spacially,have close relations with middle Triassic gypsum-salt strata,andtemporarily,was formed later than it.It has been suggested in this paper that thepyrite deposits have close genetic connection to gypsum strata.The Fe^(2+) in magmas,as reductant,reduces CaSO_4 into H_2S,providing sufficient sulfur for pyitemineralitation.The key factors controlling sulfur-rich and sulfur-deficient districtsare the spacial positions of the half-way magma chambers relative to gypsum-saltstrata.According to the above observations,combined with the block tectonics of thebasin,the metallogenic subdivision of pyrite deposits is made,and three favourableore-prospecting targets are proposed.
