摘要
福建省紫金山Cu-Au矿床是我国典型的高硫型浅成低温热液矿床,具有“上金下铜”的矿化分带特点,金矿主要产于潜水面以上的氧化带中,铜矿则主要分布于潜水面以下的原生带中,本文通过手标本、光学显微镜、XRD、FE-SEM以及EPMA等对金矿体中矿物和蚀变情况进行研究。结果表明,金矿体中地开石在多个蚀变过程都有产出,3种不同结构地开石的主要成分(Al_(2)O_(3)和SiO_(2))差异可能与矿物产出环境、结晶程度、粒径大小和晚期热液影响等有关。通过EPMA分析发现该金矿体内的绿泥石以铁斜绿泥石为主,平均结晶温度为166℃,并由镁铁质矿物在还原环境蚀变而成。绢云母和明矾石中w(K_(2)O)含量略低于理论值,这可能与晚期大气降水淋滤有关。载金矿物褐铁矿由以针铁矿、赤铁矿、石英和磁铁矿组成,以胶状结构为主,褐铁矿主要成分w(Fe_(2)O_(3))变化则可能是内部的含水矿物发生脱水导致。早期热液阶段形成大量低品位含Au的金属硫化物,而晚期则通过氧化淋滤对金进行二次富集,最终在表生氧化带中形成大储量的金矿床。
The Zijinshan Cu-Au deposit in Fujian Province is one of the typical high sulfidation epithermal deposits in China. It is characterized with the zoning of gold mineralization in the upper(shallower) level and copper mineralization in the lower level, as gold orebodies mainly occurred in the oxidation zone above the ancient underground water table,while copper orebodies mainly occurred in the primary zone below the ancient underground water table. In this paper, the mineralogical and alteration evolution characteristics of gold orebodies have been studied based on observation and analysis by using optical microscope, X-Ray Diffraction, Field Emission Scanning Electron Microscope(FE-SEM), and Electron Probe Microanalysis Analysis(EPMA). The results show that dickites occurred in multiple-stage alteration processes in the supergene oxidized gold orebodies. The difference of the main compositions(Al_(2)O_(3)and SiO_(2)) of three different structured dickites could be caused by the mineral-forming environment, crystalline degree, mineral particle size,and influence of the late-stage hydrothermal fluid. EPMA analyses found that the chlorite in gold orebodies belongs mainly to prochlorite, with the average crystallization temperature of 166℃. It was formed by the alteration of mafic minerals in the reduced environment. The relative slightly low w(K_(2)O) contents of sericite and alunite samples comparing to their respective theoretical values could be caused by the late-stage atmospheric water leaching. The gold-bearing limonite consists of goethite, hematite, magnetite, and quartz, with predominant colloidal structure. The variation of w(Fe_(2)O_(3)) contents in limonite samples may be caused by the dehydration of various water-bearing minerals enclosed in limonites. It is believed that the large reserve gold orebodies were formed in the supergene oxidation zone through the gold secondary enrichment resulted from the late-stage oxidation and meteoric water leaching of a large amount of low-grade Au-containing sulfide
作者
陈明勇
武丽艳
CHEN Ming-yong;WU Li-yan(State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;China University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《矿物学报》
CAS
CSCD
北大核心
2022年第3期329-342,共14页
Acta Mineralogica Sinica
基金
国家自然科学基金项目(编号:41773048)
“西部青年学者”项目类A类
国家重点研发计划(编号:2016YFC0600207)
中国科学院战略性先导科技专项(B类)(编号:XDB18030200)。
关键词
紫金山
金矿床
矿物特征
蚀变演化
Zijinshan
gold deposit
mineralogical characteristics
alteration evolution
