INVESTIGADORES
GUIDO Diego Martin
congresos y reuniones científicas
Título:
Ag-Pb-Bi minerals of the Pingüino In-bearing polymetallic epithermal deposit, Deseado Massif, Patagonia, Argentina
Autor/es:
JOVIC, S.; GUIDO, D.; LOPEZ, L.; PERMUY VIDAL, C.; RUIZ, R.; PAEZ, G.; MELGAREJO, J.; CRESPI, A.
Lugar:
Whistler
Reunión:
Conferencia; Geoscience for Discovery (SEG 2013) Conference; 2013
Institución organizadora:
SEG
Resumen:
The Deseado Massif, located in the Santa Cruz province in southern
Argentinean Patagonia, is an important Au-Ag producer with four mines in
operation, as well as an area of intense prospecting activity. This
metallogenic province is characterized by the presence of Upper Jurassic
low sulfidation epithermal deposits. Pingüino represents an atypical
deposit in the Deseado Massif, because of the presence of Lower Jurassic
polymetallic mineralization, that is characterized by complex sulfide
mineralogy and geochemical signature enriched in Zn, Ag, Pb, Au, Cu, Sn,
W, Bi and In. Due to the important Indium anomalies, Pingüino was
classified as an In-bearing polymetallic deposit similar to the Japan,
Bolivian and German deposits (Jovic et al., 2011). The Pingüino
polymetallic mineralization is characterized by the presence of massive
and banded sulfide veins and vein breccias up to 13 m in width. The ore
geochemistry indicates the presence of high values of Zn, Ag, Pb, Au,
Cu, Sn, W and Bi in the sulfide-rich veins (Jovic et al., 2011). Three
main stages were defined for the mineralization. The early stage (Ps1)
presents anomalous values of Au, Cu, In, Sn, W and Bi and is
characterized by a complex paragenesis, composed mainly of idiomorphic
pyrite crystals, zoned arsenopyrite, hübnerite and ferrokësterite
[Cu2(Fe,Zn)SnS4] replacing cassiterite, and is in turn replaced by
stannite [Cu2FeSnS4]. The second stage (Ps2) is characterized by a Zn,
Pb, Ag, In, Cd and Sb paragenesis, where Ps1 minerals were brecciated
and replaced mainly by banded sphalerite and galena. Grains of
hipidiomorphic tetrahedrite, freibergite argentotennantite and Pb-Ag
sulfosalts are present in this stage. Fluid inclusion studies indicate
homogenisation temperatures of 308°?327°C for Ps1 and 255°?312°C for
Ps2, and low to moderate salinities (2 to 5 eq.wt.% NaCl and 4 to 9
eq.wt.% NaCl, respectively; Jovic et al. 2011). A third stage of
mineralization (Ps3) was recognized only at microscopic scale,
characterized by an interbedding of botryoidal bands made up by Fe-poor
sphalerite and greenockite, with idiomorphic crystals of greenockite.
Within the complex sulfide mineralogy and mainly associated to the end
of the first mineralization stage, very fine-grained acicular and
prismatic minerals was found. In order to determine this minerals and
their composition optical microscopy and electron-microprobe microscopy
were done. The presence Ag-Bi, Ag-Pb-Bi, Pb-Bi sulfosalts were
determinate. The minerals are aramayoite [Ag3Sb2(Bi,Sb)S6], owyheeite
[Ag3Pb10Sb11S28], ourayite [Ag3Pb4Bi5S13], giessenite
[(Cu,Fe)2Ag26.4(Bi,Sb)19.6S57] and izoklakeite
[Pb26.4(Cu,Fe)2(Sb,Bi)19.6S57]. These specimens are very rare and are
typical from hydrothermal sulfide Sn-Ag and Pb-Zn ores. Generally, the
presence of Bi-Ag-Pb assemblage is related with relative high
temperature hydrothermal fluids; in the Pingüino deposit is associated
with temperatures between 308 and 328°C and Sn, W, Cu, Au and In, in the
Ps1. The presence of these minerals represents a new contribution to
the characterization of a new and atypical deposit type for the Au-Ag
Deseado Massif epithermal province.