- © 2014 Mineralogical Society of America
Arsenic is dispersed widely in nature and is the 47th most abundant element among the 88 known natural elements. The average crustal abundance is 1.5 ppm, with higher concentrations in reduced shales and coals. It is concentrated in many metal-bearing mineral deposits being a chalcophile element. It occurs in many metallic deposits including those of Cu, Ag, Au, Zn, Hg, U, Sn, Pb, Mo, W, Ni, Co and PGE. Arsenic is often more dispersed than ore minerals in those deposits and as such is a useful indicator in geochemical exploration (Boyle and Jonasson 1973; Hale 1981; Cohen and Bowell 2014). Consequently, elevated concentrations of As are common in mine waste and process waste from metal-bearing ores (Bowell et al. 1994, 2013; Thornton 1994; Craw and Pacheco 2002; Lazareva et al. 2002). In particular, As is the main element of environmental concern in most hardrock mines. In this chapter, we outline the principal occurrences of As at mine sites, and their environmental significance. As an example of the detailed controls on As geochemistry in mine waste we focus on the gold mines in New Zealand.
ARSENIC IN DIFFERENT MINERAL DEPOSIT TYPES
Many mines are significant point sources for As in the environment, and some mine sites have high concentrations of As locally, often exceeding 1% in ore or waste. For almost all of these mines, the As is a natural but undesirable component of the ore, and therefore the As is discarded with the rest of the mine wastes. Hence, mine wastes, especially mine tailings, are major repositories of As and have to be managed carefully.
Arsenic is an especially common constituent of sulfide-bearing mineral deposits, where As typically occurs either as separate As minerals (Table 1) or in solid solution …