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Accha

Overview

The Accha area was acquired in 1994 by Southwestern Resources and was explored under option by Cominco Ltd. in 1996 and 1997 and by Savage Resources and its successor Pasminco between 1998 and 2001.

The property is located in the southern part of the Pucara sedimentary basin at an elevation of approximately 4,300 metres in the Altiplano. The Accha deposit is hosted by limestones of the Ferrobamba Formation of Cretaceous age with mineralization being of the zinc-lead oxide type. The mineralization, which is contained within folded limestones, outcrops over widths of five metres to 50 metres. Faults displace the mineralization and possibly truncate it in places. The zinc mineralization occurs primarily as smithsonite (zinc carbonate) and hemimorphite (zinc silicate).

Two historical resource estimates under the AUSIMM JORC standards were calculated for the Accha mineral deposit using different assumptions. In 1999 Kvaerner Metals ("Kvaerner"), under engagement to Savage, calculated an indicated mineral resource of approximately 7.0 million tonnes grading 8.9% zinc and an inferred mineral resource of 1.8 million tonnes grading 8.9% zinc. In 2000 Pasminco calculated an indicated mineral resource of approximately 3.8 million tonnes at 8.9% zinc and 1% lead and an inferred resource of 2.0 million tonnes grading 11.4% zinc and 1.9% lead under more conservative assumptions. These historical JORC resource estimates have not been reconciled to the mineral resource categories of NI 43-101. Zincore believes these historical estimates may be relevant, but has not done sufficient work to know if these historical resource estimates can be relied upon. Zincore is not treating these historical estimates as current mineral resources as defined in NI 43-101, and these estimates should not be relied upon.

All scientific and technical information about the Accha-Yanque property disclosed on this website is derived from the NI 43-101 referred to below and has been prepared by, or the preparation has been supervised by, Stewart Winter, P.Geo, the Qualified Person for the property. Mr. Winter is independent of Zincore Metals Inc. and is the author of the NI 43-101 compliant Technical Report titled "Accha-Yanque Zinc Belt Project, Department of Cusco, Peru", dated August 31, 2006 and filed on SEDAR.

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History

Three concessions in the Accha Area were acquired by Southwestern Resources in 1994. The Accha area is located on Cerro Titiminas, meaning “lead mine”. Initial work consisted of surface sampling and mapping which identified the Titiminas Zone, the Titiminas West Zone, the Titiminas North Zone, the Camp Zone and the Titiminas Southwest Zone. All zones consist of smithsonite and zinc silicate mineralization in carbonates.

In September 1995, an agreement was signed with Cominco granting Cominco the right to earn a 50% interest in the three concessions in the Accha area by producing a bankable feasibility study and by making cash payments of US$1.25 million. In 1995-1996, Cominco constructed a road to the Accha area and carried out a program of exploration including 900.7 metres of diamond drilling in five holes. This work established the continuity of the zinc-lead mineralization down dip and showed that there were several zones of zinc oxide mineralization. Cominco terminated the agreement in 1997.

In May 1998, an agreement was signed with Savage granting Savage the right to earn a 51% interest in the Accha concessions by spending US$5 million over a four-year period. Savage could earn a further 19% interest (total 70%) by funding a feasibility study and providing all financing guarantees. In 1999, Pasminco acquired Savage and in 2001, the agreement was terminated when Pasminco experienced financial difficulty. The most significant work on the Accha area, which consisted of trenching, reverse circulation drilling and diamond drilling was completed by Savage/Pasminco.

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Geology

The northern end of the Apurimac batholith forms a “U” shape, opening to the south with the Accha-Titiminas area being adjacent to the northern apex of the batholith.

The Ferrobamba limestones within the area are subdivided into five divisions based on lithology. At Accha, the basal micrite sequence grades up to the altered and mineralized package, which consists of crackled, brecciated limestones and locally a bituminous, laminated argillaceous sequence with pronounced polymictic hydraulic breccias. Mineralization is hosted within stratabound brecciated and laminated limestones associated with two major thrust faults known as the Main and Middle Thrust zones that envelope mineralization and consist of puggy and broken clay matrix supported breccias which are interpreted as tectonic in origin. The total thickness of the brecciated sequence varies from 50 metres to 100 metres, while individual breccia hosts are continuous over 5 metres to 20 metres downhole. The breccias are polymictic, consisting of angular-sub-rounded limestone clasts and rare quartzite. Breccias are mostly supported by a carbonate-clay matrix and are poorly sorted with little or no apparent grading. Unmineralized stratabound breccias are recognized at the same stratigraphic level up to several kilometers away from Accha. Although karstic brecciation is observed in the Accha area, it is now considered that the main bodies of breccia are of hydraulic origin caused by fluid over-pressuring focused along pre-existing faults.

The Transitional Sequence, a crackle-breccia alteration halo related to the thrust faults, is located approximately 50 metres to 100 metres above and below mineralization. The hangingwall mineralization consists of massive micritic limestones overlain by cherty nodular limestones and silty, marly, finely laminated limestones which form the uppermost part of the sequence. The Lower Tertiary Puno Group terrestrial conglomerates unconformably overlie the limestone sequence. Recent glacial tills have been recorded within the project area and overlie all units.

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Mineralization

All of the known areas of mineralization show very similar gossaniferous, zinc-lead oxide type mineralization.

The main minerals present in zinc oxide type deposits are:

  • Hemimorphite – Zn2 (OH)2 SiO3: 54.2% Zn
  • Smithsonite – Zn CO3: 52% Zn
  • Willemite – Zn2 SiO4: 63.2% Zn
  • Cerussite – Pb CO3: 77.5% Pb
  • Goethite – FeOOH
  • Limonite – Fe2O3
  • clay minerals

Originally, the Accha zinc-lead mineralization was considered to be of the Mississippi Valley Type (“MVT”) in which the original primary minerals were zinc and lead sulphides. The current gossaniferous material containing mainly oxides, carbonates and silicates was thought to have been produced by supergene – surface weathering – processes of the primary sulphides. However, as work on the mineralized zone progressed and comparisons were made to other similar zinc oxide type deposits, the MVT model was brought into question. It is now considered that the Accha-Yanque zinc mineralization is of the zinc oxide type as represented by the Skorpion deposit of Anglo American Corp. in Namibia and the Vazante deposit in Minas Gerais State, Brazil for example.

In the Accha area, gossans rich in zinc carbonates, silicates and oxides are exposed at surface over an area measuring about 300 metres by 100 metres. Drilling has indicated oxide mineralization up to 50 metres thick which is continuous across a strike length of 700 metres and to a depth of at least 500 metres below the surface and is open down dip to the west.

Accha is located close to the hinge of an anticlinal dome structure which plunges abruptly to the east at about 50 degrees, but more gently to the west. The southern limb of the anticline dips at about 55 degrees to the SSW, while the northern limb has been truncated and down-faulted by an east-trending fault system. Within the dome, mineralization appears to be restricted between two thrust zones and the mineralization appears to pinch out when the thrusts merge, suggesting a structural control to the mineralization.

Intrusive rocks are associated with zinc mineralization in some areas, mineralization is spatially associated with the Apurimac batholith and associated minor elements (arsenic, thorium, molybdenum and strontium) are typically considered to be related to granitoid rocks.

It is considered that the Accha mineralization occurs in breccias of probably both sedimentary and tectonic origin, that the mineralization is structurally controlled, that mineralization occurs mainly as oxides and carbonates and there is at least a spatial association with granitoid intrusive rocks. It may be that the zinc oxide-carbonate deposits were formed by oxide-rich hypogene hydrothermal fluids that had their source in or were produced by the Apurimac batholith.

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Metallurgy

Test work was completed for Pasminco by Lakefield Laboratories in both Chile and Canada, by Optimet labs, Adelaide, Australia and Metcon labs, Sydney, Australia. On behalf of Zincore, the same information was reviewed by a GTI – Matomo Joint Venture (GTI – MJV).

Mineral processing and metallurgical test work on the Accha-Titiminas Area mineralization consisted of sulphuric acid leaching (including zinc leach efficiency and acid consumption), treatment of silicate minerals, solvent extraction and electrowinning (SX/EW) (see note below), flotation of zinc oxides, heap leaching and dense media separation (DMS). The most appropriate processing option for the Project is considered to be the sulphuric acid/SX/EW route primarily because it is a proven technology at the Skorpion Zinc Project of Anglo American Corp. in Namibia and the work done on the Accha-Titiminas Area indicated that the conditions required for leaching are similar to those used for Skorpion. Additional work will be required, however, to determine the optimum approach. A final decision on the preferred option can only be made after due consideration of the relevant economic factors and upfront beneficiation benefits through flotation and/or DMS. No test work has been done on the Yanque mineralization, which appears to be very similar to that at Titiminas.

Note: SX/EW or solvent extraction and electrowinning is a mineral processing technique that refers to the recovery of a metal from an ore by means of acid leaching and organic extraction, combined with electro-chemical processes. The process involves leaching the material with a weak acid solution. This solution is recovered and then contacted with an organic solvent, referred to as the extractant, in the solvent extraction stage (SX). Here the metal (in this case zinc) is extracted away from the aqueous phase leaving behind most of the impurities that were in the leach solution. The zinc bearing organic phase is stripped of its zinc by contacting it with a strongly acidified aqueous solution at which time the zinc is moved to the aqueous phase while the organic phase is reconstituted in its hydrogen form. The metal-bearing aqueous phase is advanced to the electrowinning (EW) stage of the process while the barren organic phase is returned to the extraction stage of the process.

Maps and Images

Click here to view the related maps and images.

Click here to view the August 2007 Drill Hole Location Map.

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