Temporal constraints on genesis of the Caravia-Berbes fluorite deposits of Asturias, Spain, from paleomagnetism

- Paleomagnetism yields a 206 ± 8 Ma genesis age for Spain's Caravia-Berbes fluorite ores.
- Tectonically, 206 ± 8 Ma is co-eval with the initial opening of the Atlantic Ocean.
- Carboniferous host rocks near ore were remagnetized at 115 Ma in the Biscay rift event.

The Caravia-Berbes district is a major fluorite producing area in Europe. The fluorite occurs as mantos replacing breccio-conglomerates of the Middle Permian Caravia Formation and as veins and irregular replacive bodies in the unconformably underlying limestone of the Late Carboniferous Caliza de Montaña Formation. Paleomagnetic analyses were done using alternating field and thermal step demagnetization and saturation remanence methods. Ten sites (82 specimens) in massive and disseminated fluorite ore from the Emilio manto yielded a stable chemical remanent magnetization (CRM) in hematite inclusions with a direction of Decl. 20.1°, Incl. 67.3° (α95 = 6.1°). After correction for Neogene Pyrenean tilt, the manto's paleoinclination gives a CRM acquisition age of 206 ± 8 Ma that dates a major hydrothermal and ore emplacement event. The age is coeval with the onset of Pangea's break up as the Iberian microplate began to split from the Armorican terrane of Eurasia as part of the ocean-forming CAMP (Central Atlantic Magmatic Province) event. Another 11 sites (109 specimens) of silicified dolostone of the Caliza de Montaña Formation just below the Cueto L'Aspa manto yielded a stable CRM that resides in single and pseudosingle domain magnetite inclusions that has a direction of Decl. 328.7°, Incl. 76.6° (α95 = 4.9°). After Neogene tilt correction, the altered zone's paleopole gives a CRM acquisition age of 115 ± 3 Ma. This age shows that the western Cantabrian basin also underwent a major hydrothermal alteration and remagnetization event by fluid flow through steep re-activated faults when Iberia rotated 35 ± 2° away from Eurasia during Aptian-Albian time.