The Falun supracrustal belt. Part 1: primary geochemical characteristics of proterozoic metavolcanics and granites

Abstract

The main lithostratigraphic units of the felsic supracrustal sequence of the Falun area are described. The > 100 km2, E-W trending synformal enclave is bordered to the N and S by co-magmatic Svecokarelian granites. The 4.5 km thick sequence comprises lower units of rhyolitic tuffs with minor mafic intercalations, passing up through felsic volcanics to the sulphide-bearing ore horizon. The primary geochemical characteristics of the felsic volcanics and the Svecokarelian granites are illustrated using multicationic classification diagrams. The results for 360 samples collected at ± 50 m intervals along 3 lithogeochemical traverses reveal primary lithogeochemical features which in the B-A classification of magmatic associations diagram (Debon & Le Fort, 1983) are considered to reflect a horizontal to positive aluminous trend for the Falun supracrustals. The Svecokarelian (early - to synorogenic) granites (urgranit) close to the supracrustal border also reveal a similar trend.