Yarrowita de la mina Santa Rita, Capillitas (Catamarca, Argentina)

YACIUK P; COLOMBO F; LECOMTE KL

Congreso; 14° MinMet y 5° PIMMA; 2023

Yarrowite from the Santa Rita mine, Capillitas (Catamarca, Argentina)Yarrowite, Cu9S8, has been found at La Argentina vein, Santa Rita mine, Capillitas (Catamarca, Argentina). It occurs at the Level Zero gallery, in a vein composed mainly by rhodochrosite (plus minor quartz), with abundant inclusions of galena and sphalerite. Other species present in the assemblage are pyrite, chalcopyrite, linarite, brochantite, and Fe and Mn oxi-hydroxides, with scarce otavite. This copper sulfide occurs as rims (up to 150 µm thick) on galena grains, and also as fillings in cleavage fractures, associated with pyromorphite. In plane polarized light yarrowite is pleochroic, with blue and blue-grey hues, reminiscent of covellite. Under crossed polarizers it displays a strong orange anisotropy. The average of two electron microprobe analyses (WDS mode) show (in wt.%): Cu 70.19, Ag 0.16, Fe 0.02, Zn 0.12, In 0.04, Pb 0.12, Bi 0.09, S 28.89, total 99.65. The empirical formula is (Cu9.34Zn0.02Ag0.01Pb0.01)9.38S7.62 (in atoms per formula unit, based on atoms = 17). Yarrowite was formed as a galena replacement by late Cu-bearing hydrothermal solutions, before the onset of more oxidizing conditions that led to the precipitation of Cu2+ and S6+-bearing minerals.