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Palmeiropolis |
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Tocantins, Brazil |
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Zn Cu Pb Ag
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
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The Palmeirópolis Zn-Cu-Pb massive sulphide deposits are located in north-central Goias State, Brazil.
The host Palaeoproterozoic Palmeiropolis sequence is part of a north-east trending volcano-sedimentary belt situated along the western border of the major basic-ultrabasic intrusive bodies of the Goias Massif.
Zn-Cu-Pb massive sulphide deposits with underlying zones of hydrothermal alteration embracing stringer type Cu alteration are associated with a thick sequence of basic meta-volcanic rocks (now represented by amphibolites).
The host sequence and alteration in the immediate ore zone may be generalised as follows, from the base:
* Dark green, finely granular, hornblende-plagioclase amphibolite;
* Medium grained, garnet-biotite-amphibolite with pyrrhotite and pyrite developed in the foliation, and variable disseminated chalcopyrite within fractures. This zone may be around 5 m thick.
* Anthophyllite and biotite rock, with variable garnet and staurolite. It is medium grained, with a poorly developed foliation. Disseminated sulphides are found on fractures, largely near the contact with the massive sulphide body. These include chalcopyrite, sphalerite, pyrrhotite and pyrite. This interval may be around 10 to 15 m thick.
* Massive sulphides, which are approximately 2 to 3 m thick in the smaller C-1 and C-2 deposits. Predominantly composed of sphalerite, chalcopyrite, pyrrhotite, pyrite and galena, the massive sulphides are brecciated, and encompass fragments of the enclosing wall rock lithologies.
* Hangingwall amphibolite.
Reserves in the bodies outlined to date total around 5 Mt @ 4.3% Zn, 1.2% Cu, 0.7% Pb, 25 g/t Ag. The largest deposit, C-3, contains 2 Mt @ 4.05% Zn, 1.38% Cu, 0.28% Pb, while C-1 totals 0.75 Mt @ 5.2% Zn, 1.25% Cu, 1.38% Pb, and C-2 has 0.33 Mt @ 5.8% Zn, 0.46% Cu, 1.178% Pb.
The three known orebodies have a similar ore mineralogy, comprising pyrrhotite and pyrite with associated sphalerite, chalcopyrite and galena. Alteration zones formed by anthophyllite, biotite and cordierite-bearing rocks are apparently related to the massive sulphides. The orebodies are interpreted to have been modified by the deformation which accompanied metamorphism.
The preceding is drawn from Aruajo & Nilson (1988).
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1999.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Araujo S M 1999 - The Palmeiropolis volcanogenic massive sulfide deposit, Tocantins State: in Silva M G, Misi A (Ed.), 1999 Base Metal Deposits of Brazil CPRM, Brazil pp 64-74
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Araujo S M, Scott S D 1996 - Oxygen isotope composition of alteration zones of highly metamorphosed volcanogenic massive sulfide deposits: Geco, Canada, and Palmeiropolis, Brazil: in Econ. Geol. v91 pp 697-712
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