Cono Amarillo Project


The prospect is located in the high Andes of Region I, Tarapacá, to the south-east of the Salar El Huasco salt flat and 170 km to the east of the city of Iquique. It lies at an average elevation of 4300 meters above sea level. The central reference UTM coordinates are 7 753 000 N, 533 000 E.

It comprises 327 mining rights units that cover 3205 hectares located in the Pica District, Tamarugal Province, Tarapacá Region. Companies that hold mining rights in the surroundings of the prospect include Sociedad Minera Soledad y Cía. Minera Doña Inés de Collahuasi SCM.

Prospecto cono amarillo

Mineralization zone
The prospect is located on the western edge of the Andes, where the land rises to the east of the central Salar El Huasco depression. This area of volcanic underlying geology features a large proportion of andesitic and dacitic tuff in which morpho-structural features have been observed in bands running N-S, where epithermal processes have occurred. This hydrothermal action took place in the upper Tertiary to Quaternary periods (Neogene), as a result of alteration complexes from fossil geothermal systems, domes, stratovolcanoes, and craters.

The prospect features four alteration sectors:Cono Amarillo, La Hoya, Rinconada, and María lgnacia. These volcanic structures show different levels of erosion, with different alteration zones, and they have been interpreted as a partially eroded volcanic center probably dating back to the Upper Miocene – Pliocene. The volcanic structure is comprised of andesite lava and altered rhyodacitic to dacitic tuff, but the western area also includes dome complexes.
In the Cono Amarillo sector, the level of erosion has exposed a complex of dacitic tuff with epithermal alteration. This altered unit is partially covered by younger dacitic rocks that have resisted erosion and are scattered over the altered rock. The altered zones feature silicaceous bodies, porous silica bodies affected by intense acid leaching, hydrothermal breccia, vein breccia, and veins. Two vein structures and 10 centers of acid fumarole alteration have been identified.
The area known as La Hoya is a hydrographic basin with very little surface water where dacitic sub-volcanic intrusive bodies have been detected, located at the center of the basin and surrounded to the West with argillated tuff that includes lenticular silicaceous formations with internal brecciation, and mildly argillated dacite to the south.

The Rinconada area features a series of tuffs, dacites, and volcanic breccias affected by advanced argillic alteration, with areas that feature a core of rock completely destroyed by acid fumarole action, with abundant pyrite and sulfur, surrounded by an alunite-quartz zone, merging through to kaolin at the edge.
Finally, the María Ignacia area features 2 sub-parallel pyrite silicate veins cutting through tuff affected by alunite-quartz alteration and argillization.
The most significant gold mineralization was detected in the sector known as Cuerpo Principal, which is a lenticular acid leach formation with porous silica, surrounded by an alunite-quartz zone, merging through to kaolin at the outside. The gold is located at the center of the acid leach zone, and reaches peak values of up to 10.7 gr/t. Soundings drilled into the Cuerpo Principal formation indicate that the mineralization detected is a surface phenomenon.

Geological model
The epithermal model of Cono Amarillo, La Hoya, Rinconada, and María lgnacia is interpreted as an acid fumarole epithermal system, with a high level of exposure in the theoretical model of this type of deposit, and with different areas of activity varying in location for different time of formation, creating a number of silica bodies and vein structures that are independent of each other. The hydrothermal alteration present in the prospects may have been linked to a volcanic caldera, where point sources of acid leach solution originated with residual silica fragments, surrounded by alunite-quartz layers and, in the outermost regions, quartz clays. In this context, mineralization may occur as a result of hydrothermal processes that occupy existing channels, precipitating in veins or in a more diffuse manner.


Studies conducted
The prospect received basic exploration between 1985 and 1992; mapping studies are available (1:5000, 1:2000, 1:1000 scale), as well as geochemistry and trenches to establish the limits of anomalies, and diamond and reverse air drill surveys. A total of 36 drill surveys were conducted, with a total of 5000 meters in 4 campaigns, with depth varying between 60 and 150 meters. A further 1704 trench samples were taken.

Nearby deposits
No information exists to indicate the presence of deposits close to the prospect.

Geological potential
Results indicate low gold levels except in a lenticular lode exposed in trenches, with data from 4 exploratory boreholes indicating that this formation does not extend more than 20m. Available background information suggests that the total mass of the formation is 50 000 tons of ore with a grade of less than 2 g/t of gold, for possible artisanal mining in the Cuerpo Principal lode (40 Ha).


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