WANG Cui-zhi1、2, JUE Hong-hua3
（1. Zijin Mining College, Fuzhou University, Fuzhou 350108, China;
2. Fujian Key Laboratory of Mineral Resources, Fuzhou 350108,China;
3. .Department of Earth Sciences, SUN Yat-sen University, Guangzhou 510275, China）
Abstract: Alunite from Zijinshan gold-copper deposit is of different mineral characteristics in different parts of the volcanic mechanism. Mineralogical characteristics of alunite with different shapes and in different parts of the volcanic mechanism were studied by petrography, ore microscopy, scanning electron microscope, energy spectrum analysis, electron probe, X-ray power diffraction analysis and differential thermal analysis. Alunite was divided into three genetic types, which are the magmatic hydrothermal type, the magma steam type and the steam heating type. Alunite of different genetic types has different shapes. In the magmatic hydrothermal type, it is in scaly in alunite alterated granitoid rocks or in tabular, columnar intergrowth-with-Cu-sulphide in the ore body. In the magma steam type, it is in the shape of leaf blade in the upper part of the ore body. In the steam heating type, it is in powder near the water table. Alunite has many kinds of color, it is in rose color when intergrowth with Cu sulphides, and pink, red flesh and gray white in other types. Data of electron microprobe indicate that the chemical composition of alunite fromZijin gold-copper deposit is of characteristics with extremely low K and S and high Al in major elements and high Na, Ca, Ba, and Ti in trace elements compared with theoretical values, and high Na near the volcanic crater and low Na in the north-west ore belt. Cell parameters of alunite in different positions of the volcanic mechanism change regularly in north-west ore belt. Crystal cell parameters of alunite in different positions of the volcanic mechanism increase regularly along the north-west ore belt from where near the crater to far from it. Differential thermal analysis shows that endothermic valley of alunite near the crater is deeper. These characteristics indicate that alunite near the crater was formed at higher temperature, while far from the crater was formed at lower temperature. Its formation was related with latent volcanic activities.
Key words: Zijinshan; gold-copper deposit; alunite; chemical composition; cell parameter; differential thermal analysis
ACTA MINERALOGICA SINICA Vol. 33, No. 3, 2013, Page 329-336
