Petrogénesis de los afloramientos de la FM Piñón (Cretáceo), ubicados en el sector sur, Cerro La Germania, Provincia del Guayas
Fecha
2018
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Facultad de Ciencias Naturales. Universidad de Guayaquil
Resumen
El propósito del proyecto fue determinar la procedencia genética de los afloramientos del sector sur del “Cerro La Germania”, al norte de la ciudad de Guayaquil, los resultados se lograron a través de 21 muestras de roca fresca, las cuales fueron descritas macroscópicamente y microscópicamente. Se destinaron cuatro muestras para cortes de láminas delgadas y siete para análisis químico de roca total. La metodología se basó en la interpretación petrológica, junto con el análisis modal y relaciones de fenocristales versus masa fundamental, según el diagrama de
Strekeisen. Para determinar la química de las rocas, se realizó el análisis multielemental por fusión con metaborato y espectrometría por emisión atómica y plasma en los laboratorios Inspectorate Services Perú. Se obtuvieron 7 resultados para óxidos mayores y elementos traza, se emplearon diagramas: tipo Harker, ternarios de Total Alkalis Sílica, discriminación tectónica y clasificación química normativa CIPW; se determinaron índices termodinámicos hipotéticos. Se identificaron 2 grupos de rocas; correspondiente a basaltos porfiríticos con alteraciones cloríticas, sericíticas;
enriquecidos en hierro y magnesio, con porcentaje de sílice de hasta 53% y dacitas porfiríticas de composición ácida, de hasta 68% de sílice, ambas de series magmáticas toleíticos. Se identificaron 3 estructuras mineralizadas polimetálicas con alteración hidrotermal de baja temperatura. Para basaltos y dacitas, se interpretó un ambiente tectónico tipo E-MORB superior (enriquecido), con magma parental posiblemente contaminado por rocas corticales, originado por la interacción de una pluma de manto
The goal of the investigation was to determine the genetic origin of the outcrops of the south of "Cerro la Germania", to the north of the city of Guayaquil, the results were achieved through 21 samples of fresh rock, which were macroscopically described and Microscopically. Four samples were allocated for thin-blade cuts and seven for total rock chemical analysis. The methodology was based on the petrological interpretation, along with modal analysis and relationships of phenocrysts versus fundamental mass, according to the diagram of Strekeisen. To determine the chemistry of the Rocks, the Multielemental analysis was performed, by fusion with Metaborate and spectrometry by atomic emission and plasma in laboratories Inspectorate Services Perú. Seven results were obtained for major oxides and trace elements, diagrams were used: type Harker, ternary of Total alkalis silica, tectonic discrimination and normative chemical classification CIPW; hypothetical thermodynamic indices were determined. Two groups of rocks were identified, corresponding to basalts porphyry with sericite-chlorite alterations; enriched in iron and magnesium, with a percentage of silica up to 53% and dacite porphyritic of acid composition, of up to 68% of silica, of tholeiitic origin. Three polymetallic mineralized structures were identified with hydrothermal alteration, of temperature low. For basalts and dacites, it was interpreted a tectonic environment type E-MORB (enriched), with magmas associated to rocks cortical contamination, probably originated by the interaction of a feather of mantle.
The goal of the investigation was to determine the genetic origin of the outcrops of the south of "Cerro la Germania", to the north of the city of Guayaquil, the results were achieved through 21 samples of fresh rock, which were macroscopically described and Microscopically. Four samples were allocated for thin-blade cuts and seven for total rock chemical analysis. The methodology was based on the petrological interpretation, along with modal analysis and relationships of phenocrysts versus fundamental mass, according to the diagram of Strekeisen. To determine the chemistry of the Rocks, the Multielemental analysis was performed, by fusion with Metaborate and spectrometry by atomic emission and plasma in laboratories Inspectorate Services Perú. Seven results were obtained for major oxides and trace elements, diagrams were used: type Harker, ternary of Total alkalis silica, tectonic discrimination and normative chemical classification CIPW; hypothetical thermodynamic indices were determined. Two groups of rocks were identified, corresponding to basalts porphyry with sericite-chlorite alterations; enriched in iron and magnesium, with a percentage of silica up to 53% and dacite porphyritic of acid composition, of up to 68% of silica, of tholeiitic origin. Three polymetallic mineralized structures were identified with hydrothermal alteration, of temperature low. For basalts and dacites, it was interpreted a tectonic environment type E-MORB (enriched), with magmas associated to rocks cortical contamination, probably originated by the interaction of a feather of mantle.
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FORMACIÓN PIÑÓN, DISCRIMINACIÓN TECTÓNICA, E-MORB