多元稳定同位素组合示踪含膏盐地层参与湖北金山店矽卡岩型铁矿成矿作用  

Tracing Incursion of the Evaporites into Jinshandian Skarn Fe Deposit,Hubei Province,by Combination of Multiple Stable Isotopes

作　　者：朱乔乔[1,2] 李伟[1,2] 张志远[3] 韩颖霄[3] 王建 

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]河北省地矿局探矿技术研究院,河北燕郊065200

出　　处：《地质学报》2016年第2期361-375,共15页Acta Geologica Sinica

基　　金：国家重点基础研究计划973专题(2012CB416802);国土资源部公益性行业科研专项经费课题(201311136);中央级公益性科研院所基本科研业务费专项资金(K1203)联合资助

摘　　要：相比单一稳定同位素而言,多元稳定同位素组合的使用,能更有效地示踪成矿作用过程中流体的来源和演化。本文对已证明有含膏盐地层参与成矿作用的湖北金山店铁矿开展了碳-氧-硫等多元稳定同位素的研究。方解石碳氧同位素结果表明,金山店岩体与灰岩或白云岩之间发生了广泛的水岩反应,这些水岩作用是金山店铁矿蚀变矿化过程的一部分。与各阶段矿物平衡的流体氧同位素值变化范围较小,且表现出随温度降低具有规律性变化的特征:早期矽卡岩阶段氧同位素值在岩浆水范围内变化,磁铁矿阶段则明显富集重氧同位素,而成矿后的各阶段特别是石膏-方解石阶段,成矿流体明显富集轻氧同位素。这些特征暗示成矿之前流体以岩浆水为主,成矿作用发生时有一定含膏盐地层参与成矿,而成矿后大气水特征明显,即成矿流体具有多元混合的特征。硬石膏氧-硫同位素组合暗示成矿流体中具有明显富δ^(34)S-δ^(18)O流体成分的加入,这一流体可能为淋滤了地层中膏盐组分的岩浆水或循环的大气水。成矿阶段和成矿后的黄铁矿均富集重硫同位素,也暗示成矿流体中含膏盐地层组分的加入。多元稳定同位素组合的联合证据表明,金山店铁矿成矿流体具有多元混合的特点,成矿阶段含膏盐地层参与成矿作用特征明显,暗示含膏盐地层中的膏盐组分可能是被岩浆水或循环的大气水或二者的混合流体所淋滤而进入矽卡岩成矿体系的。Compared to single stable isotope tracer, the multip the origin and evolution of the ore-forming fluid. In t multiple stable isotopes, oxygen-sulfur-carbon included, stable isotopes were more effective in tracing contribution, we present a combination of different minerals from Jinshandian skarn Fe deposit, Hubei province, which been proved had experienced a significant incursion of evaporites into its skarn system. Carbon and oxygen isotope values of calcite indicate extensive water-rock reactions between Jinshandian pluton and limestone or dolomite, which was part of the alteration and mineralization process of the Jinshandian skarn Fe deposit. Oxygen isotope values of fluid equilibrium with minerals from different stages showed a narrow range, and exhibited a regularity variation as the decrease of temperature. It is clear that oxygen isotope values of the early skarn stage overlap within the range of magmatic water, and has markedly higher δ18O values during magnetite stage, and notable light δ18O values during post ore stages, especially in late calcite-gypsum stage. These features indicating a mixing of multiple fluid sources in Jinshandian hydrothermal system, with originally dominated by magmatic water during the pre-ore stage, followed by significant incursion of evaporite materials during the ore forming stage and notable influx of δ18 O-depleted meteoric water after ore formed. Oxygen and sulfur isotope values of anhydrite indicated incursion of heavy δ34S and δ18O enriched fluid, which was likely been the magmatic water or circulation of meteoric water with leached evaporite materials. Pyrite form magnetite stage and post-ore stage （anhydrite-pyrite stage） are both enriched in heavy δ34 S, also suggesting the incursion of evaporite materials. The study of multiple stable isotope shows a mixing of diverse fluids in Jinshandian hydrothermal system and notable influx of evaporite materials during the ore forming stage, indicating that incursion evaporites was probably as the way of leaching ev

关 键 词：含膏盐地层 成矿流体 多元同位素组合 多元混合 矽卡岩型铁矿 

分 类 号：P597[天文地球—地球化学] P618.31[天文地球—地质学]