Geochemical behavior of semimetals in natural sulfide liquids: Insights from the Zhdanov Ni-Cu sulfide deposit, Pechenga ore field, Russia

• The sulfide liquid of the Zhdanov Ni-Cu sulfide deposit in the Pechenga Ore Field, Russia, has extremely low in atomic Pt/As (0.03) and Pt/Te (0.04) ratios. • Pt is not sufficient to form Pt-As and Pt-Te complexes with As and Te. • As and Te occur as individual cations, anions, or neutral metallic species in the sulfide liquid, partitioning into pentlandite formed through a peritectic reaction at 870–800 °C. • As and Te are highly enriched in pentlandite compared to pyrrhotite. Recent studies have highlighted the significant role of semimetals (including As, Sn, Sb, Te, Bi) in influencing the behavior of platinum-group elements (PGE) in natural sulfide liquids and their distribution in base metal sulfides (BMS) within magmatic sulfide deposits. However, the detailed geochemical behavior of semimetals in natural sulfide liquids remains poorly understood. In this study, we employ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and scanning electron microscopy (SEM) to examine the occurrence and distribution of semimetals in Cu-poor massive ores from the Zhdanov Ni-Cu sulfide deposit in the Pechenga ore field, Russia. Mass balance calculations reveal that approximately 46% of As and 80% of Te occur as solid solutions within BMS, with the remainder primarily hosted in As- and Te-rich platinum group minerals (PGM) that crystallized either in sulfide liquids or in small immiscible droplets enriched in Pd, Pt and semimetals. The partition coefficients of As and Te between pentlandite and pyrrhotite are 16.0 and 28.6, respectively, indicating a strong enrichment of these elements in pentlandite. As and Te have a strong tendency to form complexes with Pt in sulfide liquids. However, the exceptionally low atomic Pt/As (approximately 0.03) and Pt/Te (approximately 0.04) ratios of the sulfide liquid at the Zhdanov deposit limit the development of Pt-As and Pt-Te complexes. Consequently, As and Te primarily exist as individual cations, anions, or neutral metallic species, partitioning into and being enriched in pentlandite formed through a peritectic reaction between monosulfide solid solution (MSS) and residual sulfide liquids.