Volcan Compañía Minera S.A.A. is a subsidiary of Glencore AG, which is a subsidiary of Glencore Plc., owner of 63% of common class A voting shares and an economic interest of 23%, excluding treasury shares.
Volcan Compañía Minera S.A.A. and its subsidiary companies engaged in the mining sector operate the mining unit of Yauli, which includes the San Cristobal underground mine.
In Q4 2022, Glencore commenced a process to dispose of its 23.3% economic interest in Volcan, which is ongoing. As a result, the carrying amounts of Volcan assets and liabilities as at 31 December 2023 and 31 December 2022 are classified as held for sale.
Summary:
The Yauli unit region shows mineralization related to polymetallic epithermal systems, replacement bodies and polymetallic vein systems, as well as porphyry mineralization and skarns, thus indicating the great potential of the area.
The Yauli Dome is the foremost structural feature of the San Cristobal region. This dome measures thirty kilometers by twenty kilometers. The long dimension strikes about N 40° W. The center of the Yauli Dome is formed by the Chumpe Anticline, the main structural feature of the San Cristobal area.
Mineralization in the San Cristobal mineral district is of two different types, namely veins and mantos. Veins are emplaced transverse to the axis of the Chumpe Anticline, whereas mantos are located on the limestone side of the Paria limestone Mitu volcanic rocks contact.
The axial zone of the Chumpe Anticline is intruded by a quartz monzonite intrusion and two major alaskite dikes parallel to the axis of the anticline.
San Antonio Mantos
The San Antonio mantos are located in the southeast end of the two-kilometer Carahuacra-San Antonio area. The general strike of the San Antonio mantos is N 30° W and their dip is between 60° and 85° southwest. The mantos contain sphalerite and galena as ore minerals. Outcrop of the mantos weather to a black color resulting from the presence of manganese oxides.
Toldorrumi Manto
About one kilometer southeast of the San Cristobal mine lies the Toldorrumi manto. A seven hundred-meter long low-grade manto exists on the Mitu volcanic rocks-Paria limestone contact. The area has two weak veins, the Catalina and the Polonia veins.
The San Cristobal Vein system is made up of two main mineral-bearing structures, the San Cristobal Main Vein and the Siberia 1 Vein. The Oyama-Triunfo Vein, which is located on the northeast limb of the anticline, appears to be an extension of the San Cristobal Main Vein. Both veins are separated on the surface by Chumpe lake and no underground workings exist below the area that permit a clear correlation.
Mineralization of the San Cristobal Main Vein is of three different types: tungsten mineralization alone, combined metals with tungsten, and combined metals without, tungsten.
There is a well-defined horizontal zoning in the mine from east to west consisting of a Tungsten zone located in the Dike Section, a Copper zone located in the Phyllite and Contact sections, and a Zinc zone located in the Volcanic Section.
Vertical zoning is less well-defined, probably because development has not gone deep enough to reveal it.
Paragenetic sequence in the San Cristobal Main Vein from oldest to youngest is: pyrite, wolframite, quartz, chalcopyrite, dark sphalerite, brown sphalerite, galena, carbonates, and marcasite.
The Prosperidad Vein, which is the structure dipping opposite to the San Cristobal Main Vein, is of particular interest for future exploration beyond the San Cristobal mine. Both structures tend to join in a zone below the Chumpe intrusive where the inferred source of ore-bearing solutions is located.
Alteration of wall rocks in the San Cristobal Main Vein is of three different types forming zones away from the vein which include the silicification, the sericitization-argillization, and the chloritization zones.
The source of mineralizing solutions or at least their main channel, is indicated by zoning relationships to be located 1,300 meters from the present surface in the area below the Chumpe intrusive. From this main channel, secondary channels invaded the whole structure in a dendritic pattern.
Lapping of late minerals over early minerals indicates ai change in temperature of the ore-bearing solutions due to a decrease of activity of the intrusion which generated the ore fluids.
Mineral assemblages, ore textures and alteration of wall rocks place the San Cristobal Main Vein in the mesothermal classification.
In 2022, at the San Cristóbal mine the results of the drilling programs made it possible to confirm the depth and lateral continuity of economic mineral resources: deepening of the Ramal Piso 722, 658, Split 658 and vein K, lateral continuity of veins 722, 658, San Cristóbal, San Cristobalito and discovery of secondary veins with high grades of zinc and silver.