Peruvian mining and quarrying company Norcobre, a subsidiary of Compañía Minera Lincuna, has purchased 100% of the shares of Contonga Minería, formerly owned by Empresa Minera Los Quenuales, a subsidiary of Glencore.
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Summary:
The Contonga area is associated with sedimentary rocks with sporadic presence of volcanic rocks, which were intruded by intrusive rocks. The sedimentary environment is composed of limestones, as well as metamorphic rocks associated with quartzites and shales of the Cretaceous.
The main sedimentary stratigraphic units are related to: the Celendín formation (gray limestone with intercalations of limonite and marl), Jumasha formation (light gray limestone with intercalations of gray shales), Pariatambo formation (gray bituminous limestone with dark brown marl), Chúlec formation (gray dolomitic limestone with sandstone, limonite and shale), Pariahuanca formation (gray limestone with a dirty appearance) and Goyllarisquizga group (related to the Chimú, Santa and Carhuaz formations).
The geological work carried out in the study area shows a sequence of sedimentary rocks of Cretaceous age, composed of the Goyllarisquizga and Celendín groups. The tectonism present in this sector produced a whole sequence of deformations of the sedimentary environments, generating synclines and anticlines, which generated weak zones for the present mineralization.
Locally, the Celendín formation is related to limestones with intercalations of marls, with a thickness of 350 meters, NW direction and dipping from 60 to 70° SW. The Jumasha formation, composed of gray limestones, with a thickness of 750 meters, NW direction. The Pariatambo formation composed of dolomitic limestones with a NW direction and dipping from 55 to 60° SW. The Chúlec formation, also associated with dolomitic limestones with intercalation of lutites, and a thickness of 200 meters, NW trend and dip of 50 to 55°.
The present mineralization is associated with bodies, mantles and breccia zones, associated with a polymetallic skarn type deposit. The mineralization is located in the contact zone of the intrusives (cusciferous porphyry) of Contonga and Taully.
The mineralization presents a typical alteration of skarn type deposits or contact metasomatism considering prograde (anhydrous) alterations and retrograde alterations. The prograde alterations are composed of green garnets and the retrograde alterations of epidotes, finally an external halo of marbled limestones.
One of the structures present in the Contonga deposit is the hydrothermal breccia of Zn, Pb, Ag and Cu, located in the intrusive contact with the sedimentary rock with the presence of clays and sericites.
The typical mineralization of these environments presents an endoskarn zone, a skarn zone and an exoskarn zone, where the mineral is located in different concentrations.
The endoskarn mineralization is associated with vein filling, with low intensity, associated with garnets and sulfides. In the case of the mineralization present in the skarn, it is associated with minerals of Zn, Pb and Cu (sphalerite, galena and chalcopyrite), as well as pyrite and pyrrhotite. The mineralization zone associated with the exoskarn is considered to be larger and deeper with a lower concentration of mineralization.
Also, the presence of subvertical and mantle-type structures, with breccia zones in a distal form. Potassic alterations are observed in deeper areas, which could be related to the final phases of mineralization present in this skarn-type system.