新疆阿尔泰铁矿成矿流体及成矿过程

Ore-forming Fluid and Metallogenic Process of Iron Deposit in Altay of Xinjiang

以新疆阿尔泰铁矿为研究对象,综述铁矿成矿背景,划分成因类型和成矿时期,对典型矿床地质特征进行描述,研究成矿流体的温度和盐度以及成矿流体来源,最后探讨构造演化与铁矿成矿作用。结果表明:铁矿成因类型可划分为火山岩型、矽卡岩型、伟晶岩型、与花岗岩有关的热液型、与基性岩体有关的钒钛磁铁矿型和砂矿型;矽卡岩矿床流体包裹体从矽卡岩阶段到退化蚀变阶段再到石英-硫化物-碳酸盐阶段的均一温度(从200℃～500℃到200℃～350℃,再到160℃～300℃)以及流体盐度(NaCleq)峰值(从4.5%～21.5%到3.5%～20.5%,再到1.5%～17.5%)逐渐降低;托莫尔特铁(锰)矿沉积期成矿流体以中低温(集中在160℃～300℃)、低盐度(主要集中在4%～9%和14%～20%)为特征;两棵树伟晶岩型铁矿成矿流体为中温(173℃～290℃)、低盐度(0.35%～16.05%);氢和氧同位素特征表明,火山沉积型铁矿沉积期成矿流体是海水与岩浆水的混合,矽卡岩阶段成矿流体主要为岩浆水,石英-硫化物-碳酸盐阶段成矿流体主要为大气降水,混合少量岩浆水,同时两棵树伟晶岩型铁矿成矿流体主要来源于岩浆水和大气降水的混合;碳和氧同位素表明,矽卡岩型铁矿成矿流体中碳主要来自深部岩浆,少量来自海相碳酸盐岩。

Based on the iron deposits in Altay of Xinjiang, the metallogenic setting of iron deposits were reviewed, the genetic types and mineralization period of iron deposits were divided, geological characteristics of typical deposits were described, the temperature and salinity of ore- forming fluid and its source were analyzed, and the tectonic evolution and metallogenesis were discussed. The results showed that the genetic types of iron deposits were dominantly volcanic rock, skarn, pegmatite, hydrothermal related with granite, V-Ti-magnetite related with basic massif and placer; homogenization temperatures of fluid inclusion in skarn type deposit from skarn to retrograde alteration until quartz-sulfide-carbonate stages gradually decreased from 200 ℃-500 ℃ to 200 ℃-350℃ until 160 ℃-300 ℃, and the peak of fluid salinities （NaCleq） also decreased from 4. 5%-21. 5% to 3. 5%-20. 5% until 1. 5%-17. 5%, respectively; ore-forming fluids in the sedimentation period of Tuomoerte iron（manganese） deposit were characterized by low-medium temperature（mainly 160 ℃-300 ℃） and low salinity（mainly 4%-9% and 14%- 20%）; ore-forming fluids in Liangkeshu iron deposit with pegmatite type were characterized by medium temperature（173 ℃-290 ℃） and low salinity（0.35%-16.05%）. Hydrogen and oxygen isotope compositions suggested that the ore-forming fluids in the sedimentation period of iron deposit with volcanic sedimentary type were mainly derived from the mixture of seawater and magmatic fluid; the ore-forming fluids in skarn and quartz-sulfide-carbonate stages were mainly derived from magmatic fluid and atmospheric precipitation mixed with a little of magmatic fluid, respectively; the ore-forming fluids in Liangkeshu iron deposit with pegmatite type were mainly derived from the mixture of magmatic fluid and atmospheric precipitation. Carbon and oxygen isotope compositions suggested that the carbon in the ore-forming fluids of iron deposits with skarn type was mainly derived from deep magmatic, and a little from marine carbonate rocks.