Distribution of trace elements in pyrite from carbonate-hosted sulfide deposits of southern British Columbia

Abstract

This paper combines petrography with in situ laser-ablation inductively coupled plasma mass spectrometry to document trace-element variations in pyrite (Py) from Mississippi Valley-type (MVT) and fracture-controlled replacement (FCR) deposits in the Kootenay Arc, British Columbia. Three generations of pyrite are Py 1, Py 2, and Py 3. Pyrite 1, the earliest (occurring in MVT deposits only), has higher Ag, Ba, Cu, Ge, Pb, Sb, Sr, Tl, and V than adjacent Py 3. It has higher Ag, Au, Ba, Cu, Ge, Pb, and Tl than Py 2. Pyrite 2 occurs in MVT and FCR deposits. Relative to FCR Py 2, MVT Py 2 is enriched in Co, Ni, Mo, Ba, Tl, and Pb and depleted in other elements. The FCR Py 2 has growth-related compositional banding, which is absent in MVT Py 2. The FCR Py 2 has Ag, Cu, Ga, Ge, In, Sn, and Zn enriched cores, intermediate Au- and As-rich bands, and Co- and Ni-rich rims. Pyrite 3, the latest occurring pyrite, present in MVT and FCR deposits, is enriched in Co and Ni near overgrowths or infillings of sphalerite. Variations in composition of Py reflect mineralogy, characteristics of ore-forming fluids, and differences in physicochemical conditions between MVT and FCR deposits at the time of ore deposition.