Deportment study of critical elements – The Ruwai Pb-Zn-Ag skarn deposit in Central Kalimantan, Indonesia, as a case study

The Ruwai Pb-Zn-Ag skarn deposit is located within the Schwaner Mountain Complex in Central Kalimantan, Indonesia. It is the largest polymetallic skarn deposit in Kalimantan with the resources is estimated up to 14.43 Mt. at 4.94 wt.% Zn, 3.28 wt.% Pb, 108.11 g/t Ag which hosted by Jurassic limestones of the Ketapang Complex and Cretaceous granitoids of Sukadana Complex. In order to study the complex mineralogy and deportment of critical-elements (Ag, Bi, Sb, In, Te, Cd) pulp samples from the main stages of the processing plant (Ball mill/feed, Pb concentrate, Zn concentrate, Pb scavenger, Zn scavenger, Fe screw, and tailings) as well as 66 core samples of Pb-Zn-Ag mineralization were obtained.

Preliminary results on the pulp samples from X-ray diffraction (XRD), X-ray fluorescence (XRF) and mineral liberation analysis (MLA) agree within analytical uncertainties. The data allows a preliminary assessment of the deportment and distribution of Ag and Bi in the skarn ores and processing products. Particularly, acanthite (Ag₂S) and freibergite ((Ag,Cu,Fe)₁₂(Sb,As)₄S₁₃) are likely to be important hosts of Ag, while Bi occurs within bismuthinite (Bi₂S₃) and native bismuth (Bi). For the core samples, µ-XRF measurements of slabs have so far provided a broad overview of elemental distribution within the samples, while XRD results indicate more complex mineralogical compositions than the pulp samples.

Further analytical work including electron probe microanalysis (EPMA) and laser ablation ICP-MS are planned for all samples to be also able to evaluate the resource potential of other critical elements of interest such as Sb, In, Te, Cd.