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El Toqui - Porvenir, Aserradero, Profunda, Dona Rosa, Mallin-Monica, San Antonio, Estatuas, Mallines

Argentina

Main commodities: Zn Au Ag Pb
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The El Toqui stratabound zinc-gold-lead-silver skarn-manto deposits are located ~1350 km south of Santiago and ~125 km north of the city of Coyhaique in Region XI, Aysen in central Chile (#Location: 45° 2' 7"S, 71° 56' 35"W).

The deposit comprises 10 separate, flat lying orebodies distributed over an area of 7 x 4 km, namely Porvenir, Aserradero, Mina Profunda, Doña Rosa, Mallin-Monica, San Antonio, Estatuas, Mallines, Concordia and Zuñiga-Antolin. The first six are virtually continuous with only narrow gaps and fault offsets separating them, whilst Estatuas is 1 km to the west, and the remaining three form a cluster 2.5 km to the north.

These deposits are located in the eastern foothills of the southern Patagonian Andes. They are hosted within a sequence of volcanic and volcano-sedimentary rocks that are the western equivalents of the continental scale Jurassic to Lower Cretaceous Chon Aike Large Igneous Province and are located in the overlap with the Andean Volcanic Arc. As such their composition is influenced by the arc magmatism and they have also been subjected to Late Cretaceous to Cenozoic deformation associated with the Andean Orogen. For detail of the setting and regional stratigraphy see the Southern Andes and Patagonia record.

The El Toqui deposits were formed by metasomatic and pervasive replacement of fossiliferous coquinoid limestone at the base of the Late Jurassic to Lower Cretaceous Toqui Formation that immediately overlies andesite, tuff and breccia of the Middle to Upper Jurassic Ibáñez Formation. Mineralisation replaces limestone at two stratigraphic levels within the 16 m thick host tuff-limestone unit, to produce the Main and Upper mantos that are 6 and 1.6 m thick respectively. The Main Manto is underlain by 6.5 m of calcareous sandstone, whilst the two mantos are separated by ~3 m of banded tuff. The remainder of the overlying Toqui Formation comprises >50 m of volcanic sandstone and >35 m of bedded ash tuff. Intrusive rocks include dacite, rhyolite and andesite dykes and sills. The mineralisation is in close proximity to sills of rhyolite.

Alteration is zoned and includes i). a proximal assemblages of garnet±clinopyroxene±amphibole accompanied by Fe, As, Au, Bi and Co mineralisation in the southern cluster and ii). an outer suite of epidote±chlorite±sericite and silica with associated Pb-Ag surrounding the northern cluster.

Within the main ore zones, mineralisation occurs as pyrrhotite, arsenopyrite, sphalerite, cobaltite, chalcopyrite, bismuthinite and native gold. Mineralisation was emplaced in two temporal pulses at 120 to 118 and 113 to 108 Ma respectively (U-Pb zircon). Mineral textures and paragenetic relationships suggest the main high grade skarn alteration and base metals preceded the introduction of precious metals. Native gold and electrum infill intra-crystalline fractures between the pre-existing base metal sulphides, but are cogenetic with bismuthinite, galena-bismuthinite and cobalt and closely associated with a strong amphibole alteration, particularly actinolite and hastingsite (Kakarieka, 2006; Bussey, Kakarieka and Meinert, 2007; Mrozek, 2016).

The total cluster of 10 deposits has an endowment of 20 Mt @ 8.2% Zn, 1.5 g/t Au (Bussey et al., 2010)

Published Ore Reserves and Mineral Resources (Laguna Gold Pty Ltd website, October, 2017) are:
  Mineral Resources
      Measured resources - 0.76 Mt @ 6.72% Zn, 0.16% Pb, 13.48 g/t Ag, 0.52 g/t Au;
      Indicated resources - 4.89 Mt @ 5.43% Zn, 0.33% Pb, 15.98 g/t Ag, 0.75 g/t Au;
      Measured + Indicated resources - 5.61 Mt @ 6.72% Zn, 0.31% Pb, 15.64 g/t Ag, 0.72 g/t Au;
      Inferred resources - 2.796 Mt @ 4.87% Zn, 0.47% Pb, 19.63 g/t Ag, 1.26 g/t Au;
  Ore Reserves - included in resources
      Proved reserves - 0.15 Mt @ 5.71% Zn, 0.13% Pb, 17.88 g/t Ag, 0.50 g/t Au;
      Probable reserves - 1.35 Mt @ 5.74% Zn, 0.22% Pb, 15.51 g/t Ag, 0.58 g/t Au;
      Total reserves - 1.51 Mt @ 5.77% Zn, 0.20% Pb, 15.88 g/t Ag, 0.58 g/t Au.

Production 2016 totalled 33 200 t Zn, 500 t Pb, 6.656 t Ag and 3.477 t Au (Laguna Gold Pty Ltd website, October, 2017)

The El Toqui mine has been in operation since 1983 and has a history of reserve replacement.

The most recent source geological information used to prepare this summary was dated: 2016.    
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.


El Toqui

  References & Additional Information

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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