Boletín de la Sociedad Geológica Mexicana Volumen 71, núm. 1, 2019, p. 139 ‒ 168 http://dx.doi.org/10.18268/BSGM2019v71n1a8

Ensayo geometalúrgico para la recuperación de oro de la zona de sulfuros primarios de la mina La Herradura, Sonora, México

Efrén Pérez-Segura^1*, Juan Miguel Romero-Valle ^1,2, Gabriela Orozco-Rivera³, Daniel Rosales-Suárez³, Rodrigo Martínez-Peñuñuri⁴ 

¹Departamento de Geología, Universidad de Sonora. Rosales y Bd. Luis Encinas. 83000 Hermosillo, Sonora, México.

²Gerencia de Proyectos Mineros, Zona Noroeste, Fresnillo, PLC., Caborca, Sonora, México.

³Centro de Investigación y Desarrollo Tecnológico Servicios Especializados Peñoles S.A. de C.V. Prolongación Comonfort 2050. Antigua Aduana Col. Luis Echeverría, 27300 Torreón, Coahuila, México.

⁴Laboratorio Tecnológico de Metalurgia LTM, S.A. de C.V. Carretera a Tecoripa km. 3.5 No. 351. Col. Parque Industrial, 83259, Hermosillo, Sonora, México.

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Abstract

La Herradura mine in Sonora is one of the most important gold districts in Mexico producing more than 5.5 million ounces of gold over 17 years. It is part of an orogenic gold deposits belt with a northwest-southeast direction for 300 km long and 50 kmwide. The mineralization consists of veins and quartz networks veinlets formed in a brittle-ductil geologic environment and it is hosted in Proterozoic quartz-feldspar gneisses. The ore bodies, defined by a 0.3 g/t Au cut-off grade, have tabular forms up to 1 km in length, 1 km in depth and 100 m in width. The visual control for mineralization is the abundance of quartz veins and veinlets, and a persistent sericitic hydrothermal alteration. Different techniques were used in this work with special focus on the Mineral Liberation Analizer (MLA) program to prove the possibility of predicting recoverable gold in the mine for the primary sulphide zone. Three geometallurgical zones (Zones A, B and C) were defined by ore composites and gravimetric concentrates from the same composites. Modal composition of the concentrates is quartz, feldspar and muscovite (sericite), and a metallic mineralogy of pyrite, sphalerite, galena, magnetite, gold and tellurides of gold and silver. Gold is identified as inclusions in pyrite or in gangue minerals like quartz, albite, orthoclase or ankerite, as well as coating pyrite crystals. The gold composition is electrum with 74 % Au and 26 % Ag; the presence of petzite (Ag₃AuTe₂) and stutzite (AgTe) were also identified. Recovery constants were calculated for each geometallurgical zone, which were introduced to the resource model of more than 14 million ounces of gold, indicating that error range in recoverable gold is less than 4 % for Zone A, 6 % for Zone C and 13 % for Zone B, in relation with gold recovery calculated with traditional methods. These results could be acceptable to applicate this methodology to La Herradura deposit. The most important error range in the Zone B is interpreted as due to a nugget effect, which isvery common in such mineral deposits. It is also concluded that the secondary milling process currently incorporated to the metallurgical plant is probably unnecessary, so its removal would result in a significant saving in energy and therefore in the economy of the mine. 

Keywords: La Herradura, gold, geometallurgy, Mineral Liberation Analizer, Sonora, Mexico.