Structural characterization of ledge system and ore shoots from Cahinalito sector, El Guanaco mine, Antofagasta region, Chile

Abstract

The high sulfidation epithermal gold deposit El Guanaco is located in the Palaeocene-Lower Eocene metallogenic belt in the Antofagasta Region, northern Chile, 215 km SE of Antofagasta city. The deposit is characterized by a system of sub-parallel ledges made of vuggy silica and quartz enargite veins. In the Cachinalito sector, on the north western side of the ore deposit, the ledges system has a discontinuous linear morphology, with a general ENE-OSO orientation, consisting of many ledges segments that change abruptly in orientation, thickness, length and inclination. Grade analysis distribution, detailed mapping at deposit scale, and identification of individual structures (ledges) shows that one of the key factors in deposit genesis is the structural control. The structural analysis allowed visualizing the different segmentations within a general structure, considering the sizes, horizontal and vertical continuity, degree of connection between ledge segments of different orientations, as well as determining the orientations with greater development of mineralized structures. The distribution of the grades allowed to characterize and identify the ore shoots within the ledges, and to interpret the ascending pathways of the mineralizing fluids by dimensioning and separating the high- and low-grade mineralized sectors. This type of analysis and identification represents an important exploration tool and helps exploration and / or production drilling in this type of deposit.