"Remobilization of Ni–Co–As and platinum-group elements by carbonate metasomatic alteration (listvenitization) of metaultramafic rocks from Dobšiná, Slovakia"

Abstract

: Hydrothermal processes are mainly responsible for the release and accumulation of metals and metalloids in rocks. In this work, we investigated the mineralogy and geochemistry of altered metaultramafic rocks (listvenites) that are spatially associated with Ni–Co ores near Dobšiná aiming to identify the sources of the elements in the hydrothermal Ni–Co-mineralization. Optical microscopy, electron microprobe analysis, and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used to correlate the mineralogy with the degree of rock alteration. The sulfides and silicates in the metaultramafic rocks host rare, tiny inclusions of cooperite (nominally PtS), sperrylite (PtAs 2 ), Pty–Pd–Ir–Te phase, and Pt–Au–Cr-alloy. The results show that the metaultramafic rocks were the source of Ni and Co and that platinum-group elements (PGE) were also leached and mobilized from the metaultramafic rocks. LA-ICP-MS scans show that the sulfarsenides in the metaultramafic rocks host submicrometer inclusions of PGE minerals but the hydrothermal Ni–Co sulfarsenides contain much less PGE’s. These observations document the limited mobility of the PGE’s. Changes in the sulfide mineralogy as a function of degree of alteration suggest that the fluids brought Fe and S, and probably a substantial amount of As whereas the metaultramafic rocks supplied Ni, Co, PGE, and perhaps also some As.