Precious Metal Exploration Potential in Peru
César E. Vidal, Cía. de Minas Buenaventura S.A.A.
Gold only and silver-rich gold deposits in South America are particularly abundant in the Peruvian portion of
the Andean Orogen.
Significant new discoveries have been made during the last decade in association with Cenozoic volcanic centres along the Western Cordillera.
The largest, economically relevant “grass-root” discoveries of this kind are found in
Yanacocha,
Pierina
and Alto Chicama;
all three mining district show high-sulphidation epithermal character with near-surface oxide overprinting and amenability for diluted cyanide leaching in heaps.
Ore grades are 1 to 3 ppm Au with 10 to 100 ppm Ag. Gold and silver-bearing minerals typically occur as submicroscopic particles in paragenetic association with early covellite with vuggy silica or with late acanthite, barite and chalcedonic silica in breccia matrix.
Hypogene sulphide minerals include enargite, covellite and calcosite; hydrothermal alteration is dominated by pyrophyllite and/or alunite. Genetic and spatial association is common with porphyry Cu (Mo, Au) systems.
Exploration potential remains untapped at
La Zanja,
Sipan,
Tantahuatay,
La Virgen,
Santa Rosa,
Quicay,
Marcapunta,
Ccorihuarmi,
Arcopunco,
Poracota,
Rescatada
and Aruntani.
Current production for this group of high-sulphidation, epithermal deposits is estimated at 5,000,000 oz Au per year with a 7,500,000 oz Ag by-product;
ore reserves are added up to 50,000,000 oz Au and 300,000,000 oz Ag.
Second in size and in rate of discovery are the high-grade vein deposits in the
Orcopampa,
Ares
and Arcata mining districts.
Gold deposits form in quartz, adularia +/- sericite vein clusters with open space infilling textures and only minor replacement.
Their low to intermediate sulphidation affinities are further defined by few percents of pyrite with traces of pyrrhothite, arsenopyrite and, in some cases, abundant late stage silver suphosalts; base metal sulphides tend to increase at depth with a decrease in precious metals.
Tellurides are rare, but form the dominant gold ore in the Chipmo area of Orcopampa and may have been overlooked in other occurrences.
Highly prospective minor examples of this category are
Los Pircos,
Salpo,
Machacala,
Pampa Andino,
Antapite,
Selene
and Pallancata
among others.
During 2005, 450,000 oz Au and 11,000,000 oz Ag were produced from this group of low-sulphidation, epithermal deposits. Ore reserves add up to 3,000,000 oz Au and 20,000,000 oz Ag.
March 2006
pdac.ca
pdac.ca
EXTRA CREDIT - MINE MAPS IN PERU (if someone has more
updated maps or maps of where CMM is - please post)
minerals.usgs.gov
eia.doe.gov
Order Maps
maps2anywhere.com
MapQuest
mapquest.com |
