WU Tiantian1,2,3, SHEN Zhihui1,2,3*, QIU Yueqin1,2,3，ZHAO Honglong4
(1. College of Mining, Guizhou University, Guiyang 550025, China; 2. National & Local Joint Laboratory of Engineering for Effective Utilization of Regional Mineral Resources from Karst Areas, Guiyang 550025, China;
3. Guizhou Key Laboratory of Comprehensive Utilization of Non-metallic Mineral Resources, Guiyang 550025, China;
4. Analysis and Test Center, Guizhou Institute of Technology, Guiyang 550003, China.)
Abstract: In order to formulate reasonable gold extraction technology for recovering gold efficiently, the characteristics of gold-bearing minerals and gold occurrence state of a Carlin-type gold ore deposited in Guizhou Province, China, were investigated by using methods of optical microscopic identification, chemical analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron probe X-ray microanalysis (EPMA). The results show that the ore has gold grade of 4.30 g/t, w(S) and w(As) contents of 2.97% and 0.35%, respectively. S and As occurred mainly in -1 valence state, indicating that the ore is a primary gold ore. Granular, framboid, biological shaped, metasomatic, and banded structures are main structures of the gold ore. Main sulfides of the ore include arsenic-bearing pyrite and arsenopyrite, while main gangue minerals of the ore include quartz, carbonate minerals, and sericite. The arsenic-bearing pyrites are mostly associated with quartz and carbonate minerals, and a few of them were included in cryptocrystalline quartz and carbonaceous argillaceous minerals. Some of them are characterized with ring-shaped or curved biological remains. 94.88% of gold in the ore occurred in the form of inclusion gold. Arsenic-bearing pyrite is the main gold-bearing mineral, which contains 75.81% of gold in the ore. Au contents in different formed arsenic-bearing pyrites are decreased gradually from fine-granular one, bioclastic one, framboid one to coarse-grained one. In addition, there is no positive correlation between Au and S, Au and As. The gold occurred in forms of substituting ion in pyrite lattice and nano-particle inclusions in arsenic-containing pyrite grains, and it is generally disseminated unevenly and sparsely in the arsenic-containing pyrite. The research results can provide theoretical guidance for the formulation of pretreatment-gold leaching process for treating ores of the Carlin-type gold deposits in Guizhou or other regions. Furthermore, the effective oxidation or destruction of gold-bearing pyrite and quartz inclusions, and the prevention of gold secondary inclusion in the pretreatment process are conducive to improve the gold recovery.
Keywords: Carlin-type gold deposit; ore structure; gold-bearing mineral; embedded characteristics; occurrence state
