Geología, alteración y mineralización en el sector de la Crucita, Combarbalá, Chile
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2020
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Universidad Andrés Bello
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El sector de La Crucita se ubica al este de Combarbalá, en la Región de Coquimbo, Chile; específicamente en la hoya hidrográfica del río Cogotí, a los pies del cerro Los Azules. Se emplaza en el borde occidental de la Sub-franja de Chile Central en la Cordillera Principal. Está compuesto por rocas volcano-sedimentarias pertenecientes a la formación Salamanca.
En este estudio, se definió un modelo genético del depósito mediante la confección del mapa geológico del sector La Crucita a escala 1:5.000, con sus respectivas secciones y de la mina La Crucita a escala 1:500.
El mapa geológico de superficie muestra la existencia de una veta de 0,5 metros de ancho promedio y una extensión de 800 metros. Estructuralmente se dispone en un arreglo segmentado, escalonado, de planos subverticales y subparalelos con rumbo preferente N 43° E, caracterizada por minerales negros de plata y oro junto con sulfuros (calcopirita y calcosina) y óxidos de cobre (atacamita, brochantita y malaquita), rodeada por una zona de alteración hidrotermal de intensidad pervasiva (silicificación, argilización y sericitización) a semipervasiva (clorita, calcita y epidota). El mapa de la mina muestra en detalle la geometría, la zonación de alteración las bandas mineralizadas que conforman la mena de la veta en profundidad.
En ambos mapas las estructuras presentan dos tendencias principales: las NNW que incluyen a los sistemas de fallas Carmela, Los Azules y transversales; las NE que comprenden a los sistemas de fallas La Crucita y Túnel, que son posteriores. En planta, las geometrías son similares a un modelo de cizalla Riedel, en donde la dirección principal se orienta con el rumbo NNW, favoreciendo la dilatación y la formación de vetas en la orientación NE.
La mineralogía de mena y ganga descrita permite definir a la veta La Crucita como una veta epitermal de baja sulfuración.
Los recursos asociados estimados para el área de estudio son 416.000 toneladas. La ley de cobre total es 1,75%, la de plata es 140,73 g/ton y la de oro es 3,54 g/ton.
En base al modelo propuesto, la veta La Crucita y la zona de intensa alteración hidrotermal, representan un mayor potencial en superficie y en profundidad.
La Crucita site is located east of Combarbalá, in the Coquimbo Region, Chile; at the Cogotí river basin and on the foot of Los Azules hill. Moreover, it is set on the western border of the Central Chile sub-belt on the Principal Cordillera. The volcanic-sedimentary deposits in the study area are correlated with Salamanca Formation. A genetic model of the deposit was defined in this research by making the geological map of La Crucita sector at a scale of 1: 5,000 and La Crucita mine map at a scale of 1: 500, with their respective sections. The geological map shows 0.5 meters width (average), and an extension of 800 meters vein. Structurally is arranged as a segmented, en-echelon stepping, with subvertical and preferred subparallel N 43 ° E attitude. The vein is characterized by silver and gold black minerals together with sulfides (chalcopyrite and chalcocite) and copper oxides (atacamite, brochantite and malachite). The structures are surrounded by a pervasive (silicification, argillic and sericitic) and less intense (chlorite, calcite and epitote) hydrothermal alteration. The mine map detailed the geometry, the alteration zonation and the ore veins bands in depth. The structures in both maps show two main trends: the NNW including Carmela, Los Azules and Transversal fault systems and the later NE La Crucita and Túnel fault systems. In plan view, geometries of the structures are alike a Riedel shear model, oriented in NNW main direction, accommodating dilation and formation of veins in NE trends. According to the described ore and gangue mineralogy, La Crucita vein is defined as a low sulphidation epithermal deposit. The associated resources for the study area are estimated in 416,000 tons with grades of 1.75% total copper, 140.73 g / t silver and 3.54 g / t gold. Based on the proposed model, La Crucita vein and the area of intense hydrothermal alteration represents a great potential at the surface and in depth.
La Crucita site is located east of Combarbalá, in the Coquimbo Region, Chile; at the Cogotí river basin and on the foot of Los Azules hill. Moreover, it is set on the western border of the Central Chile sub-belt on the Principal Cordillera. The volcanic-sedimentary deposits in the study area are correlated with Salamanca Formation. A genetic model of the deposit was defined in this research by making the geological map of La Crucita sector at a scale of 1: 5,000 and La Crucita mine map at a scale of 1: 500, with their respective sections. The geological map shows 0.5 meters width (average), and an extension of 800 meters vein. Structurally is arranged as a segmented, en-echelon stepping, with subvertical and preferred subparallel N 43 ° E attitude. The vein is characterized by silver and gold black minerals together with sulfides (chalcopyrite and chalcocite) and copper oxides (atacamite, brochantite and malachite). The structures are surrounded by a pervasive (silicification, argillic and sericitic) and less intense (chlorite, calcite and epitote) hydrothermal alteration. The mine map detailed the geometry, the alteration zonation and the ore veins bands in depth. The structures in both maps show two main trends: the NNW including Carmela, Los Azules and Transversal fault systems and the later NE La Crucita and Túnel fault systems. In plan view, geometries of the structures are alike a Riedel shear model, oriented in NNW main direction, accommodating dilation and formation of veins in NE trends. According to the described ore and gangue mineralogy, La Crucita vein is defined as a low sulphidation epithermal deposit. The associated resources for the study area are estimated in 416,000 tons with grades of 1.75% total copper, 140.73 g / t silver and 3.54 g / t gold. Based on the proposed model, La Crucita vein and the area of intense hydrothermal alteration represents a great potential at the surface and in depth.
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Tesis (Geología)
Palabras clave
Mineralización, Análisis de Riesgo, Coquimbo (Chile), Cobre, Oro y Plata, Depósitos Hidrotermales, Alteraciones Ecológicas