Publication: Caracterización mineralógica del Caolín de Golpejas (Salamanca)
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2021
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Sociedad Geológica de España.
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Abstract
En el presente trabajo se propone una sistemática de caracterización mineralógica a través de la aplicación de la espectrorradiometría de campo VNIR-SWIR (visible e infrarrojo cercano y de onda corta) para el estudio de caolines. La caracterización mineralógica de base ha sido la Difracción de Rayos X, de acuerdo con la rutina clásica de los estudios de minerales arcillosos. Como caso de estudio, se ha seleccionado el yacimiento de estaño de Golpejas (Salamanca). El yacimiento estannífero de Golpejas está constituido por varias láminas de un microgranito albítico que da lugar a estructuras más o menos circulares, cortando a los metasedimentos del Complejo Esquisto-Grauváquico en la Zona Centro-Ibérica. El emplazamiento tuvo lugar durante la fase extensional de la Orogenia Varisca y los procesos de greisenización y caolinitización hidrotermal aumentaron la concentración de Sn,Ta,Nb, y dieron lugar a la formación de la caolininita por alteración de los feldespatos primarios. Puesto que los minerales del grupo de la caolinita (caolinita,dickita y nacrita) presentan rasgos característicos y diferenciadores en el intervalo de longitudes de onda con la técnica propuesta (VNIR-SWIR), los espectros obtenidos junto con las técnicas clásicas de estudio de minerales arcillosos permiten la caracterización mineralógica del caolín de Golpejas (Salamanca).
In the present work, we propose a systematics of mineralogical characterization through field spectrometry VNIR-SWIR (visible, near-infrared and short-wave infrared) as well as the techniques most used for the identification and semiquantification of special clays. The basis of the mineralogical study has been X-ray diffraction, according to the classical routine of studies on clay minerals. As a case of study, the tin deposit of Golpejas (Salamanca) has been selected. The Golpejas tin deposit consists of several sheets of albite microgranite, more or less circular in shape, that intersect the metasediments of the schist-graywacke complex in the Iberian Zone. The emplazament took place during the extensional phase of Variscan Orogeny and the processes of greaseization and hydrothermal kaolinitization increased the concentration of Sn, Nb, Ta as well as kaolin. The albite leucogranite carrying the mineralization show a strong kaolinitization that occurred during the final phase of the mineralizing stage. As kaolinite group minerals (kaolinite, dickite and nacrite) have characteristic and differentiating features in the range of wavelenght studied with the proposed technique (VNIR-SWIR), the spectra obtained together with the classic clay mineral study techniques, allow us the mineralogical characterization of the Golpejas kaolin.
In the present work, we propose a systematics of mineralogical characterization through field spectrometry VNIR-SWIR (visible, near-infrared and short-wave infrared) as well as the techniques most used for the identification and semiquantification of special clays. The basis of the mineralogical study has been X-ray diffraction, according to the classical routine of studies on clay minerals. As a case of study, the tin deposit of Golpejas (Salamanca) has been selected. The Golpejas tin deposit consists of several sheets of albite microgranite, more or less circular in shape, that intersect the metasediments of the schist-graywacke complex in the Iberian Zone. The emplazament took place during the extensional phase of Variscan Orogeny and the processes of greaseization and hydrothermal kaolinitization increased the concentration of Sn, Nb, Ta as well as kaolin. The albite leucogranite carrying the mineralization show a strong kaolinitization that occurred during the final phase of the mineralizing stage. As kaolinite group minerals (kaolinite, dickite and nacrite) have characteristic and differentiating features in the range of wavelenght studied with the proposed technique (VNIR-SWIR), the spectra obtained together with the classic clay mineral study techniques, allow us the mineralogical characterization of the Golpejas kaolin.