INVESTIGADORES
LOPEZ Luciano
congresos y reuniones científicas
Título:
Ag-Pb-Bi minerals of the Pingüino In-bearing polymetallic epithermal deposit, Deseado Massif, Patagonia, Argentina
Autor/es:
JOVIC SEBASTIAN M; GUIDO DIEGO M; LÓPEZ LUCIANO; PERMUY VIDAL CONRADO; RUIZ REMIGIO; PÁEZ GERARDO N; MELGAREJO JOAN C; CRESPI ANNA R
Lugar:
Whistler
Reunión:
Conferencia; Geoscience for Discovery (SEG 2013) Conference; 2013
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.