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Mineralization

Mineralized areas at Canasta Dorada

The Big Pit Area

The Big Pit area consists of a series of N-S trenches that expose Jurassic sedimentary rocks that have been intensely sheared, folded, cleaved, intruded, altered and mineralized along a brittle-ductile thrust fault zone. The mineralized zone is exposed for an apparent thickness of up to 35 m and appears to be thickening to the southwest under lithological and alluvial cover. This zone is open to the west and southwest and characterized by intense deformation, anastamosing shears and slip surfaces that appear to strike roughly N-S and dips very shallowly to the west, almost conformable with the attitude of the overlying sediments. Higher grades of gold mineralization (>1.0 gpt) are spatially associated with discontinuous dikes and sills of argillic altered felsic monzonite porphyry and in adjacent structural zones where the rocks are decalcified and silicified. These sills and thin dikes are generally concordant with bedding and along sub-horizontal shear zones, have minor iron oxides on fractures that are remarkably similar to fault-controlled sills and dikes observed in the nearby El Chanate gold deposit.

The sediments exposed in the Big Pit are pervasively altered and mineralized along bedding-parallel lenses and layers referred to as a “silica breccias” and at chemically reactive sites associated with argillized felsic intrusives (decalcification-silicification). The siltstones and phyllites are silicified and locally preserve the original layered texture with alternating dark and lighter bands ranging from tan to dark gray. The rocks are locally bleached and iron-stained due to oxidation of fine disseminated sulfides. Near the lowest levels of exposure within the thrust and gently-dipping structural zones, areas of dark-coloured, massive (not layered) silica-sulfide breccia have been observed that carry elevated gold values. In general, the sulfide content observed at Canasta Dorada is very low (<1%), but can range up to 5% locally.

In the Big Pit area, the mineralized low-angle structure has been explored in an area approximately 300 x 100 m, where drilling by Highvista and HDG shows there is a mineralized zone that is consistently between 10-12 m. This mineralized zone is characterized by the presence of grey quartz, strong zones of brecciation and silicification, with felsic intrusive dikes and sills (granodiorite-monzonite) that appear to have been emplaced along the low-angle structures and are deformed by younger faulting events. The primary low-angle structure typically occurs near the contact between siltstones and phyllites with overlying sandstones and in areas that are not strongly mineralized, shows black carbonaceous clay and breccias zones, with lenses of gabbroic or mafic dikes. It is common to observe large fragments of quartz veins and silicified rocks in a matrix of sheared siltstones that retain apparent bedding features.

The main control of the Canasta Big Pit deposit appears to be the low angle structure and the adjacent sheared and deformed rock units and gold mineralization occurs in the presence of grey and vuggy quartz, oxidized pyrite, silicification in the sediments, felsic dikes associates, and stockwork quartz veinlets.


Altered felsic porphyry dike with stockwork quartz veining in the Big Pit area.


Quartz vein fragments that are deformed and sheared along the fault plane (dashed line), exposed in the Big Pit area.


Quartz breccia block that has been deformed and sheared along the low-angle structure, red line outlines the block, exposed in the Big Pit area.

Las Quintas Area

Highvista has conducted detailed geologic mapping and sampling in a portion of the Las Quintas area, where low-angle structures are exposed along the range front, and locally form dip slopes to the southwest. During 2008, High Desert Gold conducted some preliminary investigations in the Las Quintas area, located approximately 7 km SW of the Big Pit area. This work was initiated to determine if the low-angle regional structures found in the Big Pit area projected through this portion of the property. Initial results from this work showed that there are very large (+50 m thick) low-angle structures in the area that locally contain up to 0.29 gpt Au, and identified high-angle structures with significant gold mineralization. The High Desert Gold work showed samples with gold values of up to 24.1 gpt from an old prospect pit on a quartz vein, 9.07 gpt from a 0.4m wide vein and 7.05 gpt from a 0.8m wide vein.


Stockwork veins cutting sheared and fractured phyllitic siltstones near the opening of an adit in the Caballos area. A sample taken vertically across this face contained 0.78 g/t Au.

Chanate North Area

In the Chanate North area, located approximately 3 km NW of the Chanate Pit, W-NW structures from the El Chanate Mine property appear to project onto the property in an area where there is little outcrop exposure except along the arroyos and washes. Rock chip samples collected by Highvista from this area during 2010 show gold values up to 2.13 g/t Au. The mineralization at El Chanate occurs primarily along the W-NW San Jose fault and where it intersects a low-angle structural fault zone that is an ideal host for gold mineralization. The El Chanate ore zone is characterized by abundant quartz veining parallel to the W-NW structural zone and in tensional quartz veins that strike to the northwest. In addition, there are erratically distributed arrays of high-angle quartz veins and sulfide hydrofractures that strike E-NE to E-W within this zone. Locally, fresh appearing andesites that at first appear to be post-mineral are cut by chalcedonic quartz veins and samples taken in these areas show anomalous values for gold. There is likely a mineralizing system in the Chanate North area, possibly similar to that being mined at the El Chanate Mine.


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