山西平顺地区矽卡岩型铁矿床地质特征及成矿物质来源探讨

Geological Characteristics of Skarn Iron Deposits and Their Mineralization Material Source in the Pingshun Area,Shanxi Province

山西平顺地区矽卡岩型铁矿主要产于燕山期中性侵入岩与中奥陶统碳酸岩地层接触带及其附近。矿化蚀变带明显,钠长石化是重要的找矿标志。北落峡ZK28-7钻孔岩芯样地球化学特征、黄铁矿(206Pb/204Pb=17.741～18.301,平均值17.993;207Pb/204Pb=15.433～15.551,平均值15.495)以及早期(206Pb/204Pb=17.859～18.474;207Pb/204Pb=15.429～15.431)和晚期侵入岩(206Pb/204Pb=17.959～18.223,平均值18.088;207Pb/204Pb=15.434～15.566,平均值15.536)的Pb同位素组成共同表明,除晚期中性侵入岩是磁铁矿的成矿母岩之外,还包括早期超基性-基性侵入岩,它也是磁铁矿形成的重要成矿母岩之一,其很可能是通过被晚期闪长岩同化交代,大量铁矿质进入了晚期闪长岩,经后期钠化蚀变,铁质析出,形成磁铁矿,间接的提供物质来源。

The skam-type iron deposits mainly occur in the contact zone between Yanshan intermediate rocks and Middle Ordovician carbonate rocks in the Ping Shun area of Shanxi Province. The mineralization and aheration show pronounced zoning, and albitization is an important ore-hunting indicator. The ^206 pb/^204 Pb and ^207 pb/^204 Pb ^206 pb/^204 Pb ratios of pyrite are in the ranges of 17,741 - 18,301 （ averaged 17. 993 ） and 15. 433 - 15.551 （ averaged 15.495） , respectively. The ^208pb/^204pb and ^207pb/^204pb ,^206pb/^204pb ration of early intrusive rocks samples are 17. 859 - 18. 474,and 15. 429 - 15. 431, respectively, while later intrusive rocks samples are 17. 959 - 18. 223 （ averaged 18. 088 ） , and 15. 434 - 15. 566 （ averaged 15. 536 ） , respectively. The Pb isotopic compositions of vasious kinds of samples from the deposit and the chemical composition of part ^7th hole＇ s core samples in Beiluoxia show that the ore material of megnetite originated from intermediate intrusive racks of the middle stage as well as uhramafic-mafie intrusive rocks of the early stage. Ultramaflc-mafic intrusive rocks are assimilated by intermediate rocks,leading to lots of iron entering the soldenite of late stage. The later sodic alteration caused iron precipitation and then formation of magnetite,which served as the material source for mineralization indirectly.