نبذة مختصرة : International audience ; Research studies provide growing evidence for the presence of fluids within magmatic mineral systems of mafic-ultramafic composition, although these ore-forming magmas are generally considered volatile-poor. Here we summarise the results of two experimental studies that clarify the role of volatiles in the formation of magmatic sulphide ore deposits in mafic-ultramafic magmas: (i) interaction experiments simulating magmatic assimilation of sulfate and/or organic compounds (Iacono-Marziano et al. 2017); (ii) a more recent experimental study shedding light on previously unnoticed physical processes ensuing from the association between sulphide melt and fluid phase (Iacono-Marziano et al. 2022). The silicate melt composition used for both studies is similar to the parental melt of Noril'sk-Talnakh ore bearing intrusions in Polar Siberia, and the starting materials of the experiments were samples in Noril'sk region. Moreover, the experiments were conducted at magmatic conditions relevant to emplacement pressures and temperatures of Noril'sk-Talnakh intrusions. Experimental findings are therefore directly applicable to these world-class ores, suggesting that volatiles may have played a crucial role in their formation. Several other magmatic sulphide ores present evidence of the occurrence of a fluid phase during ore formation; hence the mechanisms illustrated by the experiments are likely to be more common than currently considered.
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