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 two mining districts still in activity of the Yauli Dome area are Morococha to the northwest and San Cristobal-Andaychagua in the southern part of the Yauli Dome.
The southern portion of the Yauli Dome is the host of several vein-type and replacement mantles and bodies; including polymetallic deposits such as where Andaychagua, Carahuacra, San Cristobal and Ticlio are.
San Cristobal
Considered broadly, 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.
There are two types of deposits in the San Cristobal district, veins and mantos veins are roughly perpendicular to the axis of the Chumpe Anticline and mantos are emplaced along the Mitu volcanic rocks -Paria limestone contact.
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.
The San Cristobal Main Vein extends all the way along the San Cristobal fault, considering the Oyama-Triunfo Vein as its extension. The Siberia 1 Vein is located in the axial zone of the anticline.
Volcanic rocks in the area are fine to medium-grained with abundant quartz and plagioclase. Both limbs of the Chumpe Anticline show very different types of volcanic rocks. The northeast limb or Andaychagua side of the anticline has a variety of volcanic rocks which include andesites, basalt porphyries, tuffs, and dacites. The volcanic rocks on the southwest limb or San Cristobal side of the anticline are practically homogeneous throughout The most common type is described as a quartz latite porphyry.
Carahuacra
The Carahuacra deposit lies on the southwest flank of the Yauli anticline, formed by Tertiary folding. Manto ore, formed before the climax of the Andean orogeny, consists mainly of ferroan sphalerite and pyrite, with negligible chalcopyrite. These were later brecciated tectonically to form two zones of 'breccia ore'. The last phase of mineralization involved formation of epithermal cross veins with sphalerite, pyrite, galena, tetrahedrite, and jamesonite, and irregular cementation of fragments in the breccia ore by sphalerite-galena and pyrite-marcasite. Supergene alteration, particularly pronounced in the breccia zone, has formed ore much enriched in silver (native silver, argentite, pyrargyrite).
Ticlio
The Ticlio intrusion (Cu-Au) in the western part of the Morococha district displays a zoned mineralisation and alteration pattern. A core of high-density stockwork of quartz-magnetite±K-feldspar veins changes progressively to an outer zone of intense Kfeldspar alteration with a low-density of magnetite and quartzmagnetite veinlets that host small amounts of bornite and native Au inclusions in chalcopyrite. An outermost zone displays a strong pyrite-quartz-sericitic alteration and skarn mineralisation in adjacent Cretaceous carbonate rocks.
Andaychagua
Andaychagua Vein is one of the producers in the San Cristobal district, is one of the most important veins on the southeast side of the Chumpe intrusive. The vein lies on the northeast side of the Chumpe Anticline* About three and a half kilometers southeast of the San Cristobal Vein system* The Andaychagma Vein strikes N 30° E and dips 85° northwest* The vein can be traced on surface for about four kilometers, three of which are in Mitu volcanic rocks and one of which in Excelsior phyHites. The structure continues on surface across the axial zone to the southwest side of the Chumpe Anticline, but only as a fault structure without apparent mineralization. The Andaychagua Vein carries sphalerite, galena, and silver minerals.
Drilling campaigns
The 2023 and 2024 drilling campaigns aimed to enhance the geological certainty of mineral resources. Additionally, exploratory drilling sought to identify new economic resources and assess areas with promising geological and economic potential, thereby extending the longevity of the assets in the medium to long term.
In Andaychagua, efforts continued to increase the geological certainty of mining sectors by reclassifying indicated resources to measured and inferred to indicated. Additionally, new mineral resources with high grades of zinc, lead, and silver were incorporated in the extensions of the Salvadora Norte, Prosperidad Techo, Andaychagua, and Adriana bodies, as well as in the Barbara vein. Furthermore, economic mineralization with high silver content was confirmed in the Valentina vein, and the discovery of the Katherine vein with high grades of zinc, copper, and silver, as well as the Camila vein with high grades of zinc and silver were consolidated. Together, these new zones with economic mineralization ensure great operational performance in the coming years and the extension of the asset's life.
In San Cristóbal, drilling programs resulted in the incorporation of economic mineral resources in the lateral extensions and deepening of the Ramal Piso 722, 658, Split 658, Sheyla, and K veins, as the main contributors of zinc and silver mineralization. Additionally, the discovery of new polymetallic bodies and mantles, developed at the intersection of vein systems with the same structural pattern as the main veins (NE-SW orientation, Vein 658), and limestone rocks of the "Pucará Corridor," located immediately to the west and higher levels (above Level 810) of the current operating area, is being consolidated. Preliminary results show high grades of zinc and silver, generating a better operational outlook in the medium and long term.
In Carahuacra, mineral resources with high grades of zinc, lead, silver, and copper are consolidated in the mantles of the Principal and Paula systems, as well as in the eastern extension and deepening of the Lourdes vein. Additionally, the continuity of economic mineralization in the Jovencita mantle over Level 720, with high grades of zinc and silver, is confirmed.
In 2024, the deepening and eastern extension of the Lourdes vein, as well as the Lourdes gap, also showed an increase in economic mineralization below level 1020, with high grades of zinc and silver. Additionally, new resources were identified in the Mary Piso, Diana, and Teresa veins, confirming the continuity of economic mineralization in these structures.
In Ticlio, geological certainty is increased in the deepening of the Ramal Techo vein, and new economic resources are delineated over Cuerpo Reemplazamiento. Geochemical results record high grades of zinc, lead, and silver, ensuring the operational continuity of the Ticlio mine in the coming years. Additionally, exploration is being conducted in new areas with high geological potential near the operation, such as the Giuliana-Reina-Katti vein systems and large-tonnage polymetallic bodies.
In 2024, new areas with high geological potential near the operation have been explored, such as the Sherzone vein and polymetallic bodies (Ariana), with high expectations of consolidating their discovery in 2025.