AlteraciĆ³n y mineralizaciĆ³n en sistema de vetas de minas Coca-Cola I y II
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2018
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es
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Universidad AndrƩs Bello
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Licencia CC
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Resumen
Las minas Coca-Cola I y II (382 kt @ 0.86 % Cu y 10 g/t Ag) corresponden a un depĆ³sito estratoligado de cobre con plata subordinada emplazado en rocas del CretĆ”cico Inferior de Chile central. La mineralizaciĆ³n presenta un control estratigrĆ”fico-estructural, cuya comprensiĆ³n es fundamental para aportar al modelo genĆ©tico del yacimiento. En este estudio se describe la mineralogĆa y consideraciones genĆ©ticas de las vetas mineralizadas mediante un muestreo de rocas de 4 vetas N35Ā°O y 4 vetas NS, a las que se realizĆ³ anĆ”lisis de microscopĆa Ć³ptica con luz polarizada y microscopĆa electrĆ³nica de barrido.
La mineralizaciĆ³n del yacimiento responde a un modelo de precipitaciĆ³n a partir de soluciones hidrotermales, con sucesivos pulsos de alteraciĆ³n-mineralizaciĆ³n, variaciones en las condiciones de estabilidad de estos y con un aumento gradual de la proporciĆ³n de cobre en los sulfuros y/o una disminuciĆ³n de la actividad del azufre en los fluidos mineralizadores con el tiempo. La plata podrĆa haber sido incorporada en los sulfuros segĆŗn su estructura cristalina, donde complejos clorurados con Ag habrĆan sido relativamente mĆ”s estables que los de Cu; o el sistema hidrotermal habrĆa tenido menos Ag que Cu disponible, explicando su condiciĆ³n subordinada.
Un pulso hidrotermal caliente y temprano, serĆa el responsable de asociaciones clinozoisita-cuarzo y granate-clinozoisita presentes en el yacimiento. Estas son consistentes con reacciones a 350Ā°-425Ā°C usuales en depĆ³sitos de tipo skarn, donde circulan fluidos de alta temperatura en las cercanĆas de cuerpos intrusivos reaccionando con rocas calcĆ”reas/con cemento calcĆ”reo. Es probable que fluidos de derivaciĆ³n magmĆ”tica transportaran metales generando la mineralizaciĆ³n; sin descartar que parte de Cu se haya originado a partir de la lixiviaciĆ³n de rocas de caja. La mezcla de fluidos hidrotermales habrĆa tenido un rol preponderante en la mineralizaciĆ³n del sistema de vetas de Coca-Cola, donde las estructuras habrĆan actuado como canales de migraciĆ³n de fluidos y albergado la mineralizaciĆ³n favorecidas por su curvatura y dinĆ”mica de extensiĆ³n.
The Coca-Cola I and II mines (381.9 kt @ 0.86 % Cu y 10.12 g/t Ag) are a stratabound copper deposit with subordinate silver emplaced in rocks of the Early Cretaceous of central Chile. The mineralization presents a stratigraphic-structural control, whose understanding is fundamental to contribute to the genetic model of the deposit. In this study, the mineralogy and the genetic considerations of mineralized veins were described by means of a sampling of rocks from 4 veins N35Ā°O and 4 veins NS, to which an analysis of optical microscopy with polarized light and scanning electron microscopy was carried out. The mineralization of the deposit responds to a model of precipitation from hydrothermal solutions, with successive pulses of alteration-mineralization, variations in the stability conditions of these and with a gradual increase of the proportion of copper in the sulfides and / or a decrease in the activity of the sulfur in the mineralizing fluids with time. The silver could have been incorporated into the sulfides according to its crystalline structure, where chloride complexes with Ag would have been relatively more stable than those of Cu; or the hydrothermal system would have had less Ag than Cu available, explaining its subordinate condition. A hot and early hydrothermal pulse would be responsible for clinozoisite-quartz and garnet-clinozoisite associations present in the structures of the deposit. These are consistent with reactions at 350 Ā° -425 Ā° C usual in skarn deposits, where high temperature fluids circulate near to the intrusive bodies reacting with calcareous rocks/ calcareous cement of rocks. It is probable that fluids of magmatic derivation transported metals generating the mineralization; without discarding that a part of Cu originated from the leaching of box rocks. The mixture of hydrothermal fluids has a preponderant role in the mineralization of the Coca-Cola vein system, where the structures would have acted as fluid migration channels and harbored the mineralization favored by their curvature and extension dynamics.
The Coca-Cola I and II mines (381.9 kt @ 0.86 % Cu y 10.12 g/t Ag) are a stratabound copper deposit with subordinate silver emplaced in rocks of the Early Cretaceous of central Chile. The mineralization presents a stratigraphic-structural control, whose understanding is fundamental to contribute to the genetic model of the deposit. In this study, the mineralogy and the genetic considerations of mineralized veins were described by means of a sampling of rocks from 4 veins N35Ā°O and 4 veins NS, to which an analysis of optical microscopy with polarized light and scanning electron microscopy was carried out. The mineralization of the deposit responds to a model of precipitation from hydrothermal solutions, with successive pulses of alteration-mineralization, variations in the stability conditions of these and with a gradual increase of the proportion of copper in the sulfides and / or a decrease in the activity of the sulfur in the mineralizing fluids with time. The silver could have been incorporated into the sulfides according to its crystalline structure, where chloride complexes with Ag would have been relatively more stable than those of Cu; or the hydrothermal system would have had less Ag than Cu available, explaining its subordinate condition. A hot and early hydrothermal pulse would be responsible for clinozoisite-quartz and garnet-clinozoisite associations present in the structures of the deposit. These are consistent with reactions at 350 Ā° -425 Ā° C usual in skarn deposits, where high temperature fluids circulate near to the intrusive bodies reacting with calcareous rocks/ calcareous cement of rocks. It is probable that fluids of magmatic derivation transported metals generating the mineralization; without discarding that a part of Cu originated from the leaching of box rocks. The mixture of hydrothermal fluids has a preponderant role in the mineralization of the Coca-Cola vein system, where the structures would have acted as fluid migration channels and harbored the mineralization favored by their curvature and extension dynamics.
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Tesis (GeĆ³logo)
Palabras clave
MineralogĆa, Investigaciones, Recursos Minerales, Chile