Mineralización y caracterización geometalúrgica de los pórfidos CU-AU de Perol-Chailhuagón, Minas Conga, Cajamarca, Perú

Abstract

Conga Project has two porphyry copper-gold deposits in reserve; Perol and Chailhuagon, with several other similar porphyry occurrences in the vicinity as resource (Amaro) and another with important mineral inventories (Huayramachay, Gentiles and Chasu). The Conga porphyry deposits are in the Cajamarca Region of Northern Peru, 25 km ENE of the Yanacocha mining district. These porphyry deposits are aligned NW-SE parallel with the Andean trend along the Hualgayoc-Michiquillay tectonic corridor (NW-SE) similar to others important porphyry deposits in the region as Cerro Corona, Michiquillay, Galeno and La Carpa that were formed during Early Miocene magmatic activity that intruded the thick sequence of folded Mesozoic platform sedimentary rocks. Perol and Chailhuagon are separated each other 4Km in NS direction and were generated as a multi-phase intrusive of Quartz Feldspar Porphyry with at least three stages of emplacement in each deposit. The early intrusions are the principal host and the source for the economic mineralization of copper and gold At Perol, phyllic alteration strongly overprints earlier potassic alteration as a result of the retrograde alteration. At Chailhuagón is preserved the strong potassic alteration, characteristic of the prograde alteration of the porphyritic systems The dominant structural feature at Perol is the NW, high angle and parallel faults system that control the emplacement of phreatic breccias. The principal structural features at Chailhuagon are parallel NS oriented and high angle faults that control the emplacement of Chailhuagon intrusives. Economic copper and gold mineralization is associated with intense quartz veining, with phyllic and potassic alteration at Perol and Chailhuagon respectively, and with copper sulfides disseminated (chalcopyrite, bornite, covelite, chalcocite, and digenite). At Perol, the phreatic breccias with skarn contain economic copper and gold mineralization and are enriched in zinc, lead and silver, besides elements as As, Sb and Bi, but there is a penalty if their grades are too high in the concentrate. At Chailhuagón the primary sulfide mineralization is predominant and the supergene sulfides are locally present but poorly developed. At Perol they are developed in significant quantities, commonly associated with the phyllic alteration where chalcopyrite is replaced by supergene chalcocite, digenite and/or covelite and where the pyrite is coated by these minerals. Mineralogic Ore Classification Matrices of primary and secondary copper sulfides were defined based on copper solubility assay ratios, sets of mineralogy study and the visual mineralogy description during the core logging. Mineralogic ore type models have been done strongly considering the geological models, defining Oxide, Supergene, Mixed and Primary sulfide zones.