Microbial Sphalerite Formation in Carbonate-Hosted Zn-Pb Ores, Bleiberg, Austria: Micro- to Nanotextural and Sulfur Isotope Evidence

Abstract

This is especially true for some of the Irish (e.g., Navan) and Alpine (e.g., Bleiberg; Schroll, 1997) examples. One neglected aspect in the study of carbonate-hosted Pb-Zn deposits is the role of microbial processes in their formation, a topic that started to attract the general interest of economic geologists only recently (e.g., Southam and Saunders, 2005). Most evidence for the involvement of microorganisms in the formation of carbonate-hosted Pb-Zn deposits is based on sulfur isotopes. Strongly negative sulfur isotope compositions of sulfides are commonly regarded as evidence for BSR (e.g., Fallick et al., 2001; Bawden et al., 2003). Microtextural evidence for the involvement of bacteria in the mineralization process is rare. Sulfide microglobules interpreted as biogenic peloids have, however, been reported from carbonate-hosted Pb-Zn deposits in Ireland (Kucha, 1988; Kucha et al., 1990) and the Upper Silesian MVT deposits in Poland and Belgium (Kucha and Viaene, 1993). In this study we present nano-to macrotextural and sulfur isotope evidence supporting the hypothesis that microorganisms

Micro-textures and in situ sulfur isotopic analysis of spheroidal and zonal sulfides in the giant Jinding Zn–Pb deposit, Yunnan, China: Implications for biogenic processes

“…The roles of bacteria in the production of H 2 S and metallic mineralization have been extensively investigated, with depleted d 34 S values being one of the most compelling pieces of evidence (Kucha, 1988;Lichtner and Biino, 1992;Saunders and Swann, 1994;Saunders et al, 1997;Machel, 2001;Southam et al, 2001;Druschel et al, 2002;Bazylinski and Frankel, 2003;Bawden et al, 2003;Southam and Saunders, 2005;Kucha et al, 2005Kucha et al, , 2010Rainbow et al, 2006;Lengke and Southam, 2006;Barrie et al, 2009;Greenwood et al, 2013). The low d 34 S values of sulfides reported for the Jinding Zn-Pb deposit have invoked bacteria sulfate reduction (BSR) as an important mechanism for H 2 S production and mineralization (Bai et al, 1985;Zhang, 1991;Ye et al, 1992;Zhou and Zhou, 1992;Kyle and Li, 2002;Xue et al, 2007a;Tang et al, 2014).…”

“…8) and colloform sphalerite with cores of galena (Fig. 9), may have formed from either non-biogenic (Roedder, 1968;Fowler and L'Heureux, 1996) or biogenic processes (e.g., Kucha, 1988;Kucha et al, 2005Kucha et al, , 2010Saunders and Swann, 1994;Southam and Saunders, 2005). The zoned pyrite crystals and aggregates from Jinding (Figs.…”

“…1968; Kucha, 1988;Saunders and Swann, 1994;McKibben and Eldridge, 1995;Fowler and L'Heureux, 1996;Machel, 2001;Bazylinski and Frankel, 2003;Southam and Saunders, 2005;Kucha et al, 2005Kucha et al, , 2010Barrie et al, 2009). Many of these spheroidal textures, especially the colloform aggregates, have been interpreted to have resulted from inorganic processes, which were originally believed to indicate colloidal or gel-like solutions (Rogers, 1917), but were later re-interpreted to indicate high supersaturation, nucleation and growth rate (Roedder, 1968) or self-organization due to far-from-equilibrium conditions (Fowler and L'Heureux, 1996).…”

“…Many of these spheroidal textures, especially the colloform aggregates, have been interpreted to have resulted from inorganic processes, which were originally believed to indicate colloidal or gel-like solutions (Rogers, 1917), but were later re-interpreted to indicate high supersaturation, nucleation and growth rate (Roedder, 1968) or self-organization due to far-from-equilibrium conditions (Fowler and L'Heureux, 1996). On the other hand, some of these textures, including framboidal pyrite, peloidal or oolitic sphalerite and pyrite, as well as some colloform pyrite and sphalerite, have been related to bacterial activities (e.g., Kucha, 1988;Kucha et al, 1990Kucha et al, , 2005Kucha et al, , 2010Saunders and Swann, 1994;Southam and Saunders, 2005). The sulfate-reducing bacteria may have played a direct role in assembling sulfide minerals in spheroidal forms (e.g., Saunders and Swann, 1994;Kucha et al, 2005), or were indirectly involved in the shaping of the sulfide aggregates by creating extreme disequilibrium conditions (Southam and Saunders, 2005).…”

“…These peloid sulfides contain amido-acids considered to be characteristic of bacterial origin, and the core of the peloids is composed of randomly oriented bacterial sheaths with tabular phosphate, indicating a bacterial origin of the peloids (Kucha et al, 1990). Similarly, the carbonatesphalerite microglobules with a Zn-bearing dolomite core and a serrated sphalerite rim in the Bleiberg carbonate-hosted Zn-Pb deposit, Austria, have been interpreted as a biogenic origin (Kucha et al, 2010). The peloidal galena and sphalerite in Jinding (Fig.…”