Mineralogical and geochemical characterization of waste rocks from a gold mine in northeastern Thailand: application for environmental impact protection

Abstract

Waste rocks from gold mining in northeastern Thailand are classified as sandstone, siltstone, gossan, skarn, skarn-sulfide, massive sulfide, diorite, and limestone/marble. Among these rocks, skarn-sulfide and massive sulfide rocks have the potential to generate acid mine drainage (AMD) because they contain significant amounts of sulfide minerals, i.e., pyrrhotite, pyrite, arsenopyrite, and chalcopyrite. Moreover, both sulfide rocks present high contents of As and Cu, which are caused by the occurrence of arsenopyrite and chalcopyrite, respectively. Another main concern is gossan contents, which are composed of goethite, hydrous ferric oxide (HFO), quartz, gypsum, and oxidized pyroxene. X-ray maps using electron probe micro-analysis (EPMA) indicate distribution of some toxic elements in Fe-oxyhydroxide minerals in the gossan waste rock. Arsenic (up to 1.37 wt.%) and copper (up to 0.60 wt.%) are found in goethite, HFO, and along the oxidized rim of pyroxene. Therefore, the gossan rock appears to be a source of As, Cu, and Mn. As a result, massive sulfide, skarn-sulfide, and gossan have the potential to cause environmental impacts, particularly AMD and toxic element contamination. Consequently, the massive sulfide and skarn-sulfide waste rocks should be protected from oxygen and water to avoid an oxidizing environment, whereas the gossan waste rocks should be protected from the formation of AMD to prevent heavy metal contamination.

Speciation, Fate and Transport, and Ecological Risks of Cu, Pb, and Zn in Tailings from Huogeqi Copper Mine, Inner Mongolia, China

“…AMD is drainage with a pH of 2.0 to 4.5 from mines and mine wastes [1]. Metalrich effluents and AMD, just like metals in dust and solid wastes, have become a serious environmental problem all over the world [2,3]. With introduction of AMD, metals are more easily dissolved to migrate into the surrounding water and soil [4,5].…”

Evaluation of Cleaner Production for Gold Mines Employing a Hybrid Multi-Criteria Decision Making Approach

“…In general, one ton of ore only contains a few grams of gold. Thus, in comparison with other types of ores, more waste residue may be produced during the gold mine's lifetime [4][5][6]. As the gold ore is mined by the drilling and blasting method, quantities of waste gas [7,8], such as dust and blasting fumes, are emitted into the sky.…”

Mineralogical and Chemical Characteristics of Gossan Waste Rocks from a Gold Mine in Northeastern Thailand

“…4) arsenopyrite when they react with oxygen and water [2]. The resulting secondary minerals generated include as Fe-oxyhydroxide (goethite: α-FeOOH), hydrous ferric oxide (HFO)), oxides (hematite: Fe 2 O 3 , magnetite: Fe 3 O 4 ), and oxy-sulfates (schwertmannite: Fe 8 O 8 (OH) 6 (SO 4 )•nH 2 O, jarosite: KFe 3 (SO 4 ) 2 (OH) 6 ) [2, [14][15][16][17][18], which are mineral compositions of the gossan rocks [1,3,5,[18][19][20].…”

“…The gossan rocks can adsorb toxic elements (including As, Cu, Cd, Fe, Hg, Mn, Pb and Zn) [1,3,18,20] that are possibly released during oxidizing process of the sulfide mining. On the other hand, these toxic elements are naturally attenuated by schwertmannite, K-jarosite and goethite via adsorption and co-precipitation [21].…”

“…Geologically, this area comprises sandstone, siltstone, limestone, granodiorite, skarn, massive sulfide/skarn-sulfide and gossan [7,20,23]. The gossan rocks have potential to carry heavy metals/metalloids such as arsenic (up to 810 mg kg -1 ), copper (up to 7,500 mg kg -1 ), lead (4-12 mg kg -1 ) and zinc (45-350 mg kg -1 ) [20]. They may be classified as ore-bearing or ore-barren gossan rocks [6][7]24].…”