含膏盐地层与矽卡岩型铁矿的关系:以湖北金山店铁矿为例  

The Relationship between the Evaporate and Skarn-Type Iron Deposit: A Case Study of the Jinshandian Iron Skarn Deposit in Hubei

作　　者：朱乔乔[1,2] 谢桂青[1,2] 王建[3] 李伟[3] 于炳飞[4] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]国土资源部成矿作用与资源评价重点实验室,北京100037 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]中国冶金地质总局中南地质勘查院,武汉430081

出　　处：《地质学报》2013年第9期1419-1429,共11页Acta Geologica Sinica

基　　金：国家重点基础研究计划"973"专题(编号2012CB416802);国土资源部公益性行业科研专项经费课题(编号200911007-18);中国地质调查局地质矿产调查项目(编号12123311035)共同资助的成果

摘　　要：含膏盐地层对金属矿床的形成起到了重要的作用。本文对金山店铁矿中的方柱石和硬石膏、石膏、黄铁矿开展研究,结果表明方柱石中Cl含量高达4%,硬石膏、石膏、黄铁矿δ^(34)S值分别为24.9‰~27.9‰(n=10)、27.5‰~28.4‰(n=2)和16.2‰~19.4‰(n=9),硬石膏和石膏δ^(34)S值总体上接近中三叠世地层沉积硬石膏的δ^(34)S值,而黄铁矿δ^(34)S值则明显偏离0值,暗示金山店铁矿成矿体系中的S主要来自于含膏盐地层。根据共生的硬石膏和黄铁矿矿物对S同位素组成平衡分馏方程计算出其"平衡温度"范围为563~728℃(n=6),高于硬石膏中流体包裹体均一温度。已有资料暗示在高温岩浆热液阶段或是更早的岩浆阶段,含膏盐地层中的膏盐矿物就已经大量加入金山店铁矿成矿体系之中。根据方柱石中Cl的含量估算出平衡流体中的盐度超过70%,高盐度流体具有萃取和搬运巨量铁质的能力,同时提高了硬石膏的溶解度。大量硬石膏加入成矿体系,提高了该体系的氧化性,为后期磁铁矿的形成提供了良好的条件。Evaporate, composed dominantly of varying proportions of halite, anhydrite and gypsum, has showed strong relationship with the ore-forming process, especially the magmatic-hydrothermal related deposit, but its detailed effect has not been studied. The Jinshandian iron skarn deposit has distinct minerals assemblages such as anhydrite, gypsum, pyrite and seapolite, which were resourced from evaporate. The ranges of ~34S values for evaporate related minerals are ＋16.2%0＋19.40/ooo for pyrite（n=9）, ＋24.9%0~ ＋27.9%0 for anhydrite （n=10） and ＋27.5~0＋28.4X0 （n=2） for gypsum. The latter two are close to the values of the strata of the Middle Triassic Series at the Middle Low Yangze River, suggesting that the evaporate has offered sulfur for the ore-forming system. Sulfate-sulfide mineral fractionation is consistent with an approach to isotopic equilibrium, and calculated temperatures for coexisting anhydrite-pyrite pairs （n=6） are 563~728~C, which is much more higher than the temperatures gotten from fluid inclusions. Existing data show that evaporate has joined in the ore-forming system at the stage of high temperate magmatic-hydrothermal or maybe more earlier. C1 content in scapolite is as high as 4%, indicated NaC1 equiv （~） of the fluid could have reached 70~. Dissolution of evaporate has the effect of increasing the salinity of the fluid, which enhanced the capacity of leaching and transporting iron and the solubility of anhydrite. With a large amount of anhydrite joining in the ore-forming system, the oxidation state of the system were changed obviously, which provided advantageous condition for the formation of magnetite ores.

关 键 词：含膏盐地层 成矿作用 矿物成分 矽卡岩型铁矿 

分 类 号：P618.31[天文地球—矿床学]