Abstract

ZAPPETTINI, Eduardo O; DALPONTE, Marcelo; SEGAL, Susana  and  COZZI, Guillermo. Mineralogía y aspectos genéticos del depósito volcanogénico submarino de Manganeso "La Casualidad", Cerro atraves, Neuquén. Rev. Asoc. Geol. Argent. [online]. 2012, vol.69, n.4, pp.544-555. ISSN 0004-4822.

La Casualidad ore deposit is characterized by manganiferous layers interbedded with limestones and tuffs of the Chachil formation (Pliensbachian). The identified mineralogy comprises carbonates (rhodochrosite, calcite), sulfates (barite, jarosite), silicates (tefroite, manganoan garnet, pennatite, serpentine -caryopillite-, nontronite, bementite), oxides (pyrolusite, spinels from the jacobsite-franklinite series, pyrophanite, hetaerolite, akhtenskite, nsutite, cryptomelane, coronadite, hematite, magnetite, jasper), sulfides (gersdorffite, sphalerite, galena, pyrite, chalcopyrite, greigite y possible alabandite) y sulfosalts (of the tennantite-tetrahedrite series) some of them recognized for the first time in Argentina. The mineralogy and geochemistry of the deposit suggest that it was formed under submarine hydrothermal conditions in an extensional paleomargin, through hydrothermal vents controled by synsedimentary faults in a hemipelagic setting with development of a carbonatic platform. Its genesis is related to the late rift stage of the Chachil depocenter, defined as a small extensional hemigraben active during the initial rifting of the Neuquen Basin. The presence of sulfides and manganoan garnets, as well as the relationship beween manganiferous layers and limestones suggest the possibility of finding of massive sulfide bodies in the proximities.

Keywords : Tefroite; Rhodochrosite; Akhtenskite; Pennantite; Bementite.

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