Sources and composition of fluids associated with fluorite deposits of Asturias (N Spain)

Abstract

The fluorite deposits of Asturias (northern Iberian Peninsula) are hosted by rocks of Permo-Triassic and Palaeozoic age. Fluid inclusions in ore and gangue minerals show homogenization temperatures from 80 to 170°C and the presence of two types of fluids: an H20-NaCI low-salinity fluid «8 eq. wt% NaCI) and an H20-NaCI-CaCI2 fluid (7-13 wt% NaCI and 11-14 wt% CaCI2). The low salinity and the Cl/Br and NalBr ratios (CI/Brmolar 100-700and NalBr molar 20-700) are consistent with an evaporated sea water origin of this fluid. The other end-member of the mixture was highly saline brine with high Cl/Br and NalBr ratios (CI/Brmolar 700-13 000 and NalBrmolar 700-11 000) generated after dissolution of Triassic age evaporites.

Helium isotopic ratios in fluid inclusions from fluorite-rich Mississippi Valley-Type district of Asturias, northern Spain

“…According to García Iglesias and Loredo (1994) the local Permian volcanic rocks are enriched in fluorine and could have been a source of fluorine in the mineralizing fluids. The age of the Villabona deposit (185 ± 28 Ma; Sánchez et al, 2009) is consistent with a regional Early Jurassic hydrothermal event that appears to be coincident with the opening of the North Atlantic Ocean. Ore fluids that penetrated to mid-crust depths during extension and acquired fluorine from the contemporaneous alkaline volcanic and plutonic rocks would be expected to have an elevated 3 He/ 4 He ra-…”

“…The deposits share the mineralogical and geochemical characteristics of Mississippi Valley-type (MVT) ores and they have many similarities with other Mesozoic F-Ba (Zn-Pb) mineral deposits in Europe, such as the Massif Central, the North Pennine Orefield and the Southwest England (Sánchez et al, 2009).…”

Contribución de los isótopos de He al origen de los fluidos hidrotermales: aplicación al estudio de las mineralizaciones de fluorita de Asturias (N de España)

“…Sánchez,E. Vindel,et al Estudios Geol.,66 Sánchez et al, 2009. ) na, próxima al límite sur de la Cuenca Mesozoica constituida por materiales de edades comprendidas entre el Permotriásico hasta el Jurásico, que constituyen la cobertera Mesozoica.…”

“…Los sulfuros ( fig. 2b, c, d), principalmente pirita, marcasita y galena, precipitaron durante y con posterioridad a la fluorita (Sánchez et al, 2009). Estos yacimientos se pueden encuadrar en una tipología Mississippi Valley (MVT).…”

“…Estos yacimientos se pueden encuadrar en una tipología Mississippi Valley (MVT). Estudios previos (Sánchez et al, 2006, Cardellach et al, 2007, Sánchez et al, 2009) mediante la aplicación de distintos métodos analíti-cos, microtermometría, análisis de iones y metales en inclusiones fluidas, así como análisis de tierras raras, Sr e isótopos estables y radiogénicos han puesto de manifiesto que la fluorita y los minerales acompañantes se habrían formado por un proceso de mezcla entre al menos dos fluidos. (Muñoz et al, 2005;Sizaret et al, 2004), Los Peninos (Norte y Sur) en Inglaterra (Cann & Banks, 2001;Kendrick et al, 2002a), las de la zona de Schwarzwald, SO de Alemania (Pfaff et al, 2009) y la Cordillera Costero-Catalana (Piqué et al, 2008).…”