Alturas – A Recent High Sulphidation Gold Discovery on the El Indio Belt, Chile
Kevin Creel, Senior Director Global Exploration, Barrick
Jose Antonio San Vicente, Principal Exploration Geologist Chile and Argentina, Barrick
The El Indio Belt, in the Andes of central – northern Chile, is home to some of the world's largest gold deposits including Veladero, Pascua-Lama, El Indio and Tambo deposits. Barrick’s land holdings encompass much of the prospective ground on the 140 kilometer long belt. The Alturas discovery was announced in 2015 and is located toward the southern limit of the belt. It resulted from a methodical exploration campaign that re-evaluated the belt. The Alturas project is in the advanced exploration stage and located about 30 kilometers south of the El Indio Mine, a significant past producer of gold.
The geological framework of the El Indio Belt comprises volcanic and coeval sub-volcanic rocks of Oligocene to early-middle Miocene age, which were deposited in an extensional volcano-tectonic basin bounded by north-south trending faults.
Host rocks in the project area include a basal andesite unit, a sequence of dacitic tuffs intercalated with dacitic flows covered by an andesitic to dacitic sequence interpreted as flows and domes. All units are cut by multiphase phreatomagmatic breccia and later hydrothermal breccia.
Alturas was discovered within a nine square kilometer area that displays typical high sulfidation alteration. Zonation is centered on hydrothermal fluid conduits focused along margins of breccia bodies, faults and lithological contacts. Alteration assemblages progressing from weak to intense are, 1) argillic (illite / smectite), 2) transitional (kaolinite-dickite-alunite and quartz-pyrophyllite-alunite at depth), and 3) advanced argillic (quartz-alunite and vuggy microcrystalline quartz). However, in the phreatomagmatic breccia complex, alteration intensity decreases from the margin inwards, leaving an argillic (illite-smectite) core at the center of the breccia, and quartz alunite to leach vuggy microcrystalline quartz along the breccia margins. Later silicification floods zones of vuggy quartz and partially replaces quartz-alunite zones.
Disseminated gold mineralization is associated with a favorable horizon between 4,800 m and 4,600 masl and silicification controlled by breccia margins and favorable dacitic host rocks. Mineralization intersected to date is mostly oxidized. Initial test work indicates that most mineralized material is amenable to heap leach. Mineralization remains is open in multiple directions. Exploration work is focused on defining full extents as well as testing additional nearby targets.
For more information please refer to Barrick Q1 Report 2015 http://www.barrick.com/files/quarterly-reports/2015/Barrick-First-Quarter-2015-Report.pdf and accompanying investor presentation http://www.barrick.com/files/presentation/2015/Barrick-2015-Q1-Webcast.pdf for additional information on the Alturas project.
Kevin Creel, Senior Director of Global Exploration, has been exploring with Barrick since 2005. Prior to joining Barrick, he filled various exploration and operational roles at Placer Dome, Newmont, BHP, and the U.S. Bureau of Mines. He is a prospector at heart and trained as an exploration geochemist, economic geologist and engineer at the Colorado School of Mines.