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Shalipayco - Resurgidora, Intermedios

Peru

Main commodities: Zn Ag Pb
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The Shalipayco zinc-lead-silver deposit is located within Junin Region of Peru, ~170 km NE of Lima and ~35 km SE of Cerro de Pasco.

The deposit is composed of several stratabound orebodies, the largest of which are Resurgidora and Intermedios, hosted within Upper Triassic Chambara Formation carbonate rocks of the Pucara group.

For details of the regional setting, see the separate Peruvian Andes Cu-Au Province record.

The setting of the host sequence commences with a basement of Neoproterozoic rocks of the Maraynioc metamorphic complex, which is composed of mica schists and gneiss. This is overlain by slates of the Ordovician Contaya Formation, and phyllites, slates and quartzites of the Silurian to Devonian Excelsior Group. The upper Paleozoic sequence comprises the Ambo Group continental clastic and the carbonate rocks of the Tarma and Copacabana Groups. These are overlain by the Upper Permian to Triassic Mitu Group molasse and then above an erosional unconformity by the host Pucara limestones and dolostones.

The host Pucara Group is of Norian to Pliensbachian age in the Upper Triassic to Lower Jurassic and was deposited on an extensive carbonate platform which was developed from the beginning of the Andean cycle on the western edge of the Brazilian Shield. It consists of thick dolostone sequences with partial pre-evaporitic features formed in peritidal environments. Carbonate sedimentary rocks of the Pucará Group represent a Palaeozoic transgression over the terrestrial molassic redbeds of the Mitu Group, and are overlain by recent cover of moraine, fluvioglacial, alluvial, lacustrine and fluvial sediments. Further east, in the central part of the Eastern Cordillera, intrusive stocks of Triassic to Jurassic granodiorites and monzogranites are developed. The principal structures are NW-SE faults and thrusts, such as the Ulcumayo-San Rafael Fault System, as well as folds corresponding to the Peruvian-Incaic phase.

The Pucara Group is divided into three principal formations: Chambará, Aramachay and Condorsinga. The, first of these, the Chambará Formation is the thickest and most extensive, and is the host to the stratabound mineralisation in Shalipayco. It is composed of a thin basal conglomerate, sandstone and basaltic andesite flows that fill erosion surfaces. These are followed by a thick sequence of dolostones with mudstone and wackestone, intercalated with dolomitic limestone and dark grey limestone with abundant chert nodules and fossiliferous cross-bedded limestones.

The lower unit of the overlying Aramachay Formation comprises black bituminous limestones with abundant clastic components and intercalated andesitic volcanic rocks, including flows, volcaniclastics, and pyroclastics; as well as pelitic sedimentary rocks with abundant organic matter. At Shalipayco, these units may be up to 40 m thick (Rosas and Fontboté, 1995). No mineralisation has been encountered within this unit at Shalipayco. Fossils indicate a Lower Jurassic, Hettangian-Sinemurian age.

The Condorsing Formation is exposed to the west of the deposit, where it has been subjected reverse faulting and thrusting which have reduced the degree of outcrop. It comprises packstone to grainstone limestones with abundant chert, with the base of the sequence essentially composed of limestone interbedded with dolomitic limestones, containing macrofossils, bioturbated limestone, and pseudomorphic carbonates after anhydrite nodules (Rosas and Fontboté, 1995). These fossils indicate a Jurassic age, Sinemurian age. No mineralisation has been recorded in this formation.

Mineralisation at Shalipayco comprises stratabound mantos and lenses that are subparallel to stratigraphy. Vein mineralisation (e.g., Veta Eddy) has also been identified within the deposit, although it is not included in the resources due to insufficient drill density and lack of structural interpretation. The principal mantos are Resurgidora, Intermedio, San Luis, Pucará and Virgencita. These mineralised bodies do not generally have extensive lateral continuity, with lengths that vary from 50 to 400 m and thicknesses averaging 1.50 m, although Intermedio and Resurgidora can persists over strike lengths of up to 3 and 4 km respectively, with thicknesses of as much as 18 m.

Mineralisation comprises sphalerite, galena and pyrite, with a gangue of marcasite, bravoíte, barite, dolomite, calcite, quartz and dolo-sparite. It occurs with a range of textures including rhythmites, replacements, collapse breccias, crackle breccias, mosaic breccias, veinlets and evaporitic textures. The zinc and lead content may locally be a high as 51% Zn and 17% Pb (e.g., in the Intermedio manto). Grades average 4.9% Zn and 0.5% Pb. The Zn/Pb ratio varies from 73.2 at Resurgidora to 304.6 at Intermedio Manto.

The paragenetic sequence has been defined for the deposit as follows:
Phase I – Diagenetic resulting in the formation of sparry carbonates replacing ooliths, as well as formation of pyrite-sphalerite + galena + coarse grain carbonates;
Phase II – Epigenetic, when low temperature solutions were generated and dolomite, sphalerite I, marcasite I, pyrite, and bravoíte were formed;
Phase III – Brecciation a hydraulic brecciation with later filling by sphalerite II, marcasite II, galena and carbonates (calcite);
Phase IV – Supergene Oxidation, with the formation of limonite.

Estimated Mineral Resources as of 30 June, 2017 (VM Holdings S.A., 2017) as reported in Robson et al. (2017), were:

  Measured Resource - 2.45 Mt @ 5.41% Zn, 0.42% Pb, 32.8 g/t Ag;
  Indicated Resource - 3.84 Mt @ 5.74% Zn, 0.44% Pb, 42.1 g/t Ag;
  Measured + Indicated Resource - 6.29 Mt @ 5.61% Zn, 0.43% Pb, 38.5 g/t Ag;
  Inferred Resource - 19.93 Mt @ 4.95% Zn, 0.47% Pb, 34.7 g/t Ag.

This summary was drawn from Robson, D.M., Carlsson, J.T., Altman, K.A. and Theben, S., 2017 - Technical report on the preliminary economic assessment of the Shalipayco Project, Junín Region, Peru; an NI 43-101 Technical Report prepared by Roscoe Postle Associates Inc. Canada, for VM Holding S.A. Luxembourg, 194p.

The most recent source geological information used to prepare this summary was dated: 2017.    
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.


  References & Additional Information
   Selected References:
de Oliveira, S.B., Johnson, C.A., Juliani, C., Monteiro, L.V.S., Leach, D.L. and Caran, M.G.N.,  2021 - Geology and genesis of the Shalipayco evaporite-related Mississippi Valleytype Zn-Pb deposit, Central Peru: 3D geological modeling and C-O-S-Sr isotope constraints: in    Mineralium Deposita   v.56, pp. 1543-1562.


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, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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