Análisis petrográfico y geoquímico del intrusivo cerro totoral (La Joya) ubicado en la parroquia Las Lojas, cantón Daule
Fecha
2021-03
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Facultad de Ciencias Naturales. Universidad de Guayaquil
Resumen
El Cerro Totoral pertenece al intrusivo de Pascuales el cual aflora sobre la Formación Piñón, el Cerro San Enrique se encuentra cercano al Cerro Totoral, este estudio tiene como objetivo determinar la procedencia tectónica de estos cerros. Se recolectaron 22 muestras del Cerro Totoral y Cerro San Enrique debido a que la mayor parte de los afloramientos del Cerro Totoral están altamente meteorizados. Se seleccionaron 6 muestras para análisis macroscópico y petrográficos determinando sus porcentajes mineralógicos aplicando conteo modal, posteriormente ploteados en el diagrama de Streckeisen. En los análisis geoquímicos de las rocas se seleccionaron 3 muestras que fueron enviadas a laboratorio donde se realizó análisis multielemental por fusión con metaborato y espectrometría por emisión atómica y plasma; basados en óxidos mayores, elementos trazas y tierras raras (REE). Los resultados geoquímicos fueron ploteados en diferentes diagramas, mediante una hoja de cálculo CIPW determinando índices termodinámicos hipotéticos y asociación mineralógica. En el Cerro Totoral se identificó granodioritas y tonalitas con considerable contenido de plagioclasas alteradas a sericita y a clorita; en el Cerro San Enrique se identificó granitos correspondientes a una misma fuente magmática calcoalcalina procedentes de un ambiente geotectónico de tipo arco volcánico determinado por las relaciones Cr vs Y de los análisis geoquímicos.
The Cerro Totoral belongs to the intrusive Pascuales that outcrops in the Piñon Formation, Cerro San Enrique is located near to Cerro Totoral, the objective of this study is to determine the tectonic origin of these hills. Were collected 22 samples from Cerro Totoral and Cerro San Enrique because most of the outcrops of Cerro Totoral are highly weathered. Were selected 6 samples for macroscopic and petrographic analysis, determining their mineralogical percentages applying modal count, later plotted in the Streckeisen diagram. In the geochemical analysis of the rocks, were selected 3 samples that were sent to the laboratory where multielemental analysis was performed by fusion with metaborate and atomic and plasma emission spectrometry; based on major oxides, trace elements and rare earths (REE). The geochemical results were plotted in different diagrams, using a CIPW spreadsheet determining hypothetical thermodynamic indices and mineralogical association. In the Cerro Totoral were identified granodiorites and tonalites with considerable content of plagioclase altered to sericite and chlorite; in the La Joya sector, granites corresponding to the same calc-alkaline magmatic source were identified from a geotectonic environment of the volcanic arc type determined by the relationships Cr vs Y of the geochemical analyzes.
The Cerro Totoral belongs to the intrusive Pascuales that outcrops in the Piñon Formation, Cerro San Enrique is located near to Cerro Totoral, the objective of this study is to determine the tectonic origin of these hills. Were collected 22 samples from Cerro Totoral and Cerro San Enrique because most of the outcrops of Cerro Totoral are highly weathered. Were selected 6 samples for macroscopic and petrographic analysis, determining their mineralogical percentages applying modal count, later plotted in the Streckeisen diagram. In the geochemical analysis of the rocks, were selected 3 samples that were sent to the laboratory where multielemental analysis was performed by fusion with metaborate and atomic and plasma emission spectrometry; based on major oxides, trace elements and rare earths (REE). The geochemical results were plotted in different diagrams, using a CIPW spreadsheet determining hypothetical thermodynamic indices and mineralogical association. In the Cerro Totoral were identified granodiorites and tonalites with considerable content of plagioclase altered to sericite and chlorite; in the La Joya sector, granites corresponding to the same calc-alkaline magmatic source were identified from a geotectonic environment of the volcanic arc type determined by the relationships Cr vs Y of the geochemical analyzes.
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GRANODIORITA, TONALITA, ARCO VOLCÁNICO