Die Flußspatlagerstätten Asturiens/Nordspanien und deren Genese

The fluorspar deposites described are located within the permotriasic basin of Western Asturias/Northern Spain. The block-faulted basin is bordered in the south by the Cantabrian Mountainrange, folded in Hercynian times. The fluorspar deposites overlie the strata of this paleozoic base and the fluorspar-layers dip gently to the North at 10 to 15?. They are related to the angular unconformity between the mostly eroded Paleozoic rocks and the overlying, mainly red, Permotriasic sediments. Volcanic rocks apear only in few places, where they are intercalating more ore less the upper parts of triasic strata, reddish shales of “Keuper” age. The occurrences fluorspar-layers are found mainly in the uneroded areas where the basal Permotriasic is still preserved on the old Permian land surface, underlain preserved on the old Permian land surface, underlain mostly by Devonian and lower Carboniferous limestones, marls and shales. A special rock type, a breccia between the foulded Paleozoic base and the unfolded Permotriasic sediments forms a marker horizon, thought to have originated from the fracturing of the underlaying Paleozoic rocks. The genesis of fluorspar and breccia is thought to be connected with the formation of a peneplain-like land surface and its repetated uplift and depression, i. e. repeated flooding by sea and subsequent emergence. Light-grey to reddisch sand- and siltstones as well as small pebble conglomerates were deposited in erosion channels and karst holes, sometimes extending through the breccia down into the massiv lower Carboniferous and Devonian base. It is in these sediments, that the fluorspar is found to produce dispersed or in massiv form sheet-like and flat-lying bodies as well as channel-like, occurrences. In areas of strong post, Permian tectonic movements the stratabound mineralisation were sometimes mobilized to form dike-like deposites. The morphological and petrological structure, e. g. the complete lack of primary zoning even in dike-like deposites, and the geological situation as a whole contradict the opinion of G.Einecke (1956) that these fluorspar deposites originated from hydrothermal solutions, emanating from plutonic or volcanic rocks. Geochemical investigations of soil samples and drill cores from Paleozoic rocks point to the origin of fluorine from Devonian and Carboniferous, rich in organisms (Coal-strata) and consisting of shales marls and limestones (or even older rocks) which were eroded and redeposited in Permian times.