Indicadores de metamorfismo de bajo grado en el carbonífero de la Cuenca Central Asturiana

• Autores: Marcos Castro Rivas, Covadonga Brime Laca, J.A. Sáenz de Santa María, A.Mª. Gutiérrez
• Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 1, 3, 2000 (Ejemplar dedicado a: V Congreso Geológico de España (Alicante, 10-14 julio 2000)), págs. 219-222
• Idioma: español
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• Resumen

  • The Central Coal Basin (Cantabrian Zone) comprises mostly Westphalian sequences which developed in the external zone of the Variscan Orogen Belt. Sedimentation is thought to have occurred in a foreland basin in front of the developing mountain chain. Isovol maps show the highest volatile contents in the shouthern part o f the area. The isovols cut stratigraphic boundaries and structures, indicating that heating is a late event. Clay assemblages are dominated by illite with smaller amounts o f kaolinite, chlorite, pyrophyllite, paragonite and mixed-layers illite/smectite and paragonite/muscovite, across the entire coalfield. Illite crystallinity (1C) values in the Carboniferous sequence are in the range 0.635-0.257°20 for the air-dried mounts (77% of the values < 0.42°20), and within the range 0.539-0.251 °20 for the glycolated mounts (97% of the values < 0.42°2Q). Most of the values are therefore within the anchizone. These data are incompatible with previous correlations of coal rank/volatile matter and illite crystallinity. Discrepant 1C values are interpreted as a feature inherited from the source area.