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Rubi Project, Peru
The Rubi project is an early stage exploration property hosting several areas of low-sulphidation epithermal veins of probably mid-Miocene age. Gold and silver mineralization is present in at least four known areas called the Minas Rubi, Virgin de Chapi and San Andres areas, which occur along a nine kilometer-long corridor, south to north respectively. The property represents Radius's first acquisition in Peru.
Location and access
The property is located some 400 km south-east of Lima in the Department of Ayacucho, south-central Peru. The claims are within 2 km of the Nazca-Cusco highway, some 16 km east of the town of Puquio. Access within the claims is good via numerous dirt tracks. Minas Rubi was a former producing Au-Ag mine in the 1980's and 1990's and was held by Banco Minero for 15 years, Hochschild won the property by auction in 2005 and Exploraciones Andinas recently acquired the property from the former.
Work Program
A comprehensive three month exploration program was undertaken which incorporated regional scale mapping over the property, and prospect-scale mapping in the Minas Rubi, San Andres, Minas Chapi and San Sebastien areas, including rehabilitation of underground tunnels at Rubi and underground channel sampling. A total of 594 rock channel samples were taken and analyzed for Fire Assay gold and multi-element ICP at Chemex Laboratories in Lima. Silver values over 100 g/t were also tested for Fire Assay. Assays for the Minas Rubi area have been received and are reported on the accompanying maps below.
Regional Geology and Alteration
Sedimentary rocks of Mesozoic age correspond to the Arcurquina Formation, which are overlain by Tertiary volcanic rocks of Paleogene to Pleistocene age and classified as the Puquio, Grupo Tacaza and Barroso Formations.
Locally a total of 8 geological units were mapped on the property (see geological map). In terms of hydrothermal alteration, four types were mapped consisting of silicification, argillic (illite-chlorite), propylitic (epidote-chlorite) and quartz-calcite-manganese related to fissure-type vein mineralization at Minas Rubi.
Three systems of faults were mapped on the property. A system of regional N-S and NW-SE trending faults affect the west side of the property and preserve a sequence of agglomerates and andesites that host the Minas Rubi mineralization. In the central part of the property and south of Minas Chapi, a NE-SW fault controls the Esperanza Au-Ag vein and an associated hydrothermal breccia with opaline silica. Local E-W faults are important in controlling mineralization at San Andres and the Rio Azul vein at Minas Rubi.
Mineralization
Mineralization is present as gold-silver bearing quartz-calcite veins of low sulphidation affinity. Generally in the San Andres and Chapi areas, veins are quartz-dominated with anomalous base metal values seen as argentite, arsenopyrite, chalcopyrite and minor sphalerite. Oxidation has affected the veins by only several meters. In the Minas Rubi area, the main target area, a more robust series of quartz-calcite veins shows a deep oxidation profile to approximately 80m depth, undoubtedly controlled by regional N-S faulting. Secondary mineralization as hydrothermal breccia bodies were mapped south-east of Minas Chapi and San Sebastien Areas, and as isolated areas of silicification and oxidation north and east of San Andres.
Minas Rubi
This was a former producing Au-Ag mine in the 1980's and 1990's and was held by Banco Minero for 15 years. Mineralization at Rubi is a set of NNW and E-W trending veins, observed as underground workings, pits and surface vein occurrences on a rounded hill. Some were mined commercially via a series of underground adits. Gold-silver mineralization is associated with quartz-carbonate veins and breccias, with veins on surface reaching widths of several metres. Host rocks are a sequence of andesite porphyries of Paleocene age. Alteration in wall rock andesites is as weak propylitic observed as secondary chlorite and epidote. Mineralization on surface and underground appears mainly as oxide, and the mine operated a flotation and vat-leach operation.
Work by Radius comprised re-habilitation of old adits, detailed mapping and sampling. Local geology at Minas Rubi comprises flat lying andesitic agglomerates underlain by andesitic flows. The principle structure exploited at Minas Rubi was the Rica Chorla Vein, a 010-020 trending calcite-quartz vein. The structure shows widths up to 3m on surface with important values in gold and silver, and can be traced for ~400m. Previous results from surface sampling gave values up to 20.8 g/t Au and 356 g/t Ag over 2m. Work identified a series of parallel structures and several new veins (Charo, Shirley) which were mapped and sampled. Two structural trends are evident: a north-south system of faults controlling the majority of the veins at Rubi; and the preservation (graben block) of the oxidized portion of the veins with the horst block to the west exposing the limestones of the Arcurquina Formation and a series of local east-west faults (Rio Azul vein). Four principle veins were noted that occur in an area approximately 1000m x 500m, namely Rica Chola-Claudia, Charo, Shirley, and Rio Azul.
A total of 222 surface rock chip channel samples were taken and 49 underground samples. Results are illustrated in the attached figure. Best results in Au and Ag are concentrated in the northern part of the property along the Chorla Rica vein and associated structures. Gold grades from trace up to 12.4 g/t Au and 663 g/t Ag were received and average around 1 - 2 meters in width. Samples taken underground in old re-habilitated adits showed a continuation of gold and silver mineralization from surface. The near-surface strongly oxidized parts of the Chirulin and Rio Azul veins were formerly exploited by Banco Minero and recently by informal miners. All samples are anomalous in zinc, copper and lead.
The Chorla Rica vein has a general N-S orientation and dips an average of 43 degrees east. Vein widths vary from 0.75-3m on average. Gangue mineralogy consists of principally quartz-calcite and manganese oxides. Locally bladed quartz pseudomorphs after calcite were noted. Other veins mapped showed similar widths, an example being the Charo vein, reaches widths of up to 6m and averages <1m, traceable for ~200m on surface. Several kilometers of veins were mapped and sampled and show a deep oxidation profile at least 70m in depth. The deep oxidation profile seen in the Minas Rubi area is not seen elsewhere on the property and is thought due to local preservation of an uplifted block by the N-S faulting immediately west of the mine area.
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Maps
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