Papers by Marcela Barrera
EARTH SCIENCES RESEARCH JOURNAL, 2021
At El Chucho creek, located to the west of the Valle del Cauca department in Colombia, some hydro... more At El Chucho creek, located to the west of the Valle del Cauca department in Colombia, some hydrothermal alterations affecting the Buga Batholith rocks and dykes of porphyritic quartz-dioritic and tonalitic composition were identified. These lithological units host mineral occurrences of pyrite, chalcopyrite, and molybdenite that occur disseminated in the rocks or associated with quartz veinlets. The hydrothermal alterations identified were phyllic, propylitic, and, in minor quantity, potassic. The two firsts alterations' distribution is related to structures and pervasive, whereas the last one seems restricted to contact zones of porphyritic dykes on tonalite. Microthermometric data were acquired i) on quartz veinlets of 1 cm thick over a phyllic alteration zone, and ii) on quartz veinlet of 1 cm thick with chalcopyrite ± molybdenite and copper silicates, both veinlets cutting the phaneritic tonalite. Those data suggest that the mineralizing fluids have an aqueous-saline chemical system and were trapped under low volatile content. The microthermal data allowed authors to identify two mineralizing events. One of them of higher temperature, with homogenization temperatures between 275°C-480°C; as the second event is characterized by lower homogenization temperatures that range from 100°C to 139°C. Caracterización de eventos hidrotermales asociados con ocurrencias de minerales de cobre-molibdeno en la quebrada El Chucho, Cerrito, Valle del Cauca-Colombia En la quebrada El Chucho, localizada en el occidente del departamento del Valle del Cauca-Colombia, fueron identificadas alteraciones hidrotermales que afectan tanto a rocas tonalíticas del Batolito de Buga como a diques porfiríticos de composición cuarzo-diorítica y tonalítica. Estas unidades litológicas hospedan minerales como pirita, calcopirita y molibdenita que se presentan diseminados y en parte asociados con vetillas de cuarzo. Las alteraciones hidrotermales identificadas corresponden a fílica, propilítica y en menor medida potásica. La distribución de las dos primeras alteraciones está relacionada con estructuras o bien pueden presentarse de forma pervasiva en las rocas afectadas; mientras que la última parece estar restringida a las zonas de contacto de los diques porfiríticos con la tonalita del Batolito de Buga. Los datos de microtermometría se midieron i) en vetillas de cuarzo de 1 cm de espesor localizadas sobre zonas de alteración fílica y ii) en vetillas de cuarzo de 1 cm de espesor con calcopirita ± molibdenita y silicatos de cobre; ambas vetillas se encuentran cortando la tonalita fanerítica. Los datos microtermométricos sugieren que los fluidos mineralizantes tienen un sistema químico acuoso-salino y fueron atrapados bajo un régimen de bajo contenido volátil; además, la información microtermométrica permitió identificar dos eventos mineralizantes, uno de ellos de alta temperatura, cuyas temperaturas de homogenización varían entre 275°C-480°C y un segundo evento caracterizado por bajas temperaturas de homogenización que van desde 100°C a 139°C. RESUMEN Record Manuscript
RESUMEN En este trabajo se presenta la descripción petrográfica de secciones de núcleos (YAR-06, ... more RESUMEN En este trabajo se presenta la descripción petrográfica de secciones de núcleos (YAR-06, YAR-017 y YAR-019) pertenecientes al Sistema Porfirítico Yarumalito, con el objeto de identificar la litología y alteraciones hidrotermales asociadas con mineralizaciones de oro en este sistema, propiedad de Colombian Mines Corporatión, este proyecto se localiza a 4,3Km al sur del municipio de Valparaíso, Antioquia. La descripción de estas secciones se realiza mediante el análisis macroscópico de núcleos de perforación, petrografía y microscopia electrónica (SEM); petrográficamente los cuerpos hipoabisales corresponden a andesitas y dacítas con alteraciones potásica, propilítica, cuarzo-sericita y sericítica; estás alteraciones tienen distribución en halos de vetillas o al interior de estas y menormente se presenta con una distribución penetrativa. En las secciones analizadas, el pulso inicial corresponde pórfidos de composición andesítica, con alteraciones potásica, cuarzo-sericitica y propilítica, este pulso es seguido por pórfidos dacíticos que presenta las mismas alteraciones pero con una intensidad mayor y finalmente estos cuerpos hipoabisales son cortados por pequeños diques dacíticos cuya alteración principal es sericitica. La mineralogía de los pórfidos aporta datos sobre las etapas evolutivas del sistema, así por ejemplo se observa como el pulso inicial es más básico y progresivamente va pasando a composiciones moderadamente más félsicas; de igual manera ocurre con las texturas de estos cuerpos, que sugieren niveles de profundidad relativamente diferentes para los pulsos identificados; por otra parte las texturas secundarias y las alteraciones presentes indican una prominente interacción con fluidos de origen magmático-hidrotermal.
ABSTRACT This paper describes petrographically sections of drill core (YAR-06, YAR-017 and YAR-019) belonging to the Yarumalite Porphyritic System, in order to identify the lithology and hydrothermal alterations associated with gold mineralization in this system, owned of Colombian Mines Corporation, this project is located 4,3 Km south of the municipality of Valparaiso, Antioquia. The description of these sections bodies is made by the macroscopic analysis of drilling cores, optical petrography and electron microscopy (SEM); petrographically the hypoabisal bodies correspond to andesites and dacites with potassic, propylitic, quartz-sericite and serictic alterations; these alterations have distribution in halos of veins or to the interior of these and less occurs with a distribution pervasive in the rock. In the analyzed sections, the initial pulse corresponds to andesitic porphyries, with potassic, quartz-sericitic and propylitic alterations, this pulse is followed by dacitic porphyries that presents the same alterations but with a greater intensity and finally these hypoabisal bodies are cut by small dacitic dykes whose main alteration is sericitic. The mineralogy of the porphyries provides data on the evolutionary stages of the system, for example it is observed as the initial pulse is more basic and progressively goes to compositions moderately more felsic; similarly to the textures of these bodies, which suggest relatively different levels of depth for the identified pulses; on the other hand the secondary textures and hydrothermal alterations presents, suggest a prominent interaction with fluids of magmatic-hydrothermal origin.
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Papers by Marcela Barrera
ABSTRACT This paper describes petrographically sections of drill core (YAR-06, YAR-017 and YAR-019) belonging to the Yarumalite Porphyritic System, in order to identify the lithology and hydrothermal alterations associated with gold mineralization in this system, owned of Colombian Mines Corporation, this project is located 4,3 Km south of the municipality of Valparaiso, Antioquia. The description of these sections bodies is made by the macroscopic analysis of drilling cores, optical petrography and electron microscopy (SEM); petrographically the hypoabisal bodies correspond to andesites and dacites with potassic, propylitic, quartz-sericite and serictic alterations; these alterations have distribution in halos of veins or to the interior of these and less occurs with a distribution pervasive in the rock. In the analyzed sections, the initial pulse corresponds to andesitic porphyries, with potassic, quartz-sericitic and propylitic alterations, this pulse is followed by dacitic porphyries that presents the same alterations but with a greater intensity and finally these hypoabisal bodies are cut by small dacitic dykes whose main alteration is sericitic. The mineralogy of the porphyries provides data on the evolutionary stages of the system, for example it is observed as the initial pulse is more basic and progressively goes to compositions moderately more felsic; similarly to the textures of these bodies, which suggest relatively different levels of depth for the identified pulses; on the other hand the secondary textures and hydrothermal alterations presents, suggest a prominent interaction with fluids of magmatic-hydrothermal origin.
ABSTRACT This paper describes petrographically sections of drill core (YAR-06, YAR-017 and YAR-019) belonging to the Yarumalite Porphyritic System, in order to identify the lithology and hydrothermal alterations associated with gold mineralization in this system, owned of Colombian Mines Corporation, this project is located 4,3 Km south of the municipality of Valparaiso, Antioquia. The description of these sections bodies is made by the macroscopic analysis of drilling cores, optical petrography and electron microscopy (SEM); petrographically the hypoabisal bodies correspond to andesites and dacites with potassic, propylitic, quartz-sericite and serictic alterations; these alterations have distribution in halos of veins or to the interior of these and less occurs with a distribution pervasive in the rock. In the analyzed sections, the initial pulse corresponds to andesitic porphyries, with potassic, quartz-sericitic and propylitic alterations, this pulse is followed by dacitic porphyries that presents the same alterations but with a greater intensity and finally these hypoabisal bodies are cut by small dacitic dykes whose main alteration is sericitic. The mineralogy of the porphyries provides data on the evolutionary stages of the system, for example it is observed as the initial pulse is more basic and progressively goes to compositions moderately more felsic; similarly to the textures of these bodies, which suggest relatively different levels of depth for the identified pulses; on the other hand the secondary textures and hydrothermal alterations presents, suggest a prominent interaction with fluids of magmatic-hydrothermal origin.