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Chorolque |
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Bolivia |
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Sn W
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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 Chorolque tin mine is located in the Altiplano of Bolivia, approximately 525 km SSE of the city of La Paz, 180 km SSW of Potosi and 100 km north of the Argentine border. It lies towards the southern end of the Bolivian/Andean tin belt.
For details of the tectonic, regional geological and metallogenic setting see the Central Andes and Bolivian Orocline, and the Andean Tin Belt records.
The Chorolque porphry tin deposit is related to a volcanic complex comprising a vent/stock which is around 1 km in diameter which has been strongly brecciated and a surrounding suite of crystal and pumice-rich ash flow tuffs dated at between 18.5 and 16 Ma, that cut and overlie folded Ordovician siliciclastics. The ash flow tuffs comprise around 50% phenocrysts and their broken fragments in a dense groundmass. The pumice lapilli are a few to a few tens of centimetres across and comprise about 30% of the tuff, with associated fine to medium grained crystals of quartz, feldspar and biotite with rare hornblende relics and accessory zircon, apatite and leucoxene.
A concentric pattern of alteration is centred on the volcanic vent which is interpreted to have channeled hydrothermal fluids into the overlying volcanic sequence. An intense quartz-tourmaline central zone within and above the volcanic vent area grades outwards into an annulus of tourmaline-sericitisate associated with stockwork like brecciation and porphyry style disseminations and veinlets of sulphides and cassiterite. This zone is in turn enveloped by an outer propylitic halo. Silicification is present with all alteration types, although it is most intense in the core of the system, progressively decreasing in degree outwards.
The central quartz-tourmaline core carries no disseminated or stockwork tin. It does however embrace an east-west striking, steeply (around 70°) dipping series of veins which represent the main mineralisation. The veins may also extend for up to 1000 m into the surrounding country rocks. Vein fill ranges from quartz-tourmaline-cassiterite in the core of the system, grading outwards into quartz-wolframite-pyrite and Bi-Ag-Pb-Cu-Zn mineralisation in the distal intervals.
Surrounding this core, within the 400 m wide sericite-tourmaline zone there is strong veinlet and diseminated sulphide mineralisation (carrying from 0.04 to 0.1% Sn over a 200 m width) in both the Tertiary volcanics and Palaeozoic sediments.
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2000.
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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Dietrich, A., Lehmann, B. and Wallianos, A., 2000 - Bulk rock and melt inclusion geochemistry of Bolivian Tin Porphyry systems: in Econ. Geol. v.95, pp. 313-326.
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