Metallogeny of the Armorican Massif

Abstract

Successive metallogenic episodes, spread over several hundred million years in the Armorican Massif, can be related to the following major events (Chauris and Guigues 1969; Chauris 1980): The Cadomian orogeny (southward subduction under the old Icartian continent) with volcanosedimentary and hydrothermal-sedimentary formations (Brioverian polymetallic sulfide deposits), followed by granitic intrusions (cassiterite-wolframite-bearing mineralization). A shelf-forming period with deposition of sedimentary mineralization (Zr-Ti, Fe) followed by extension accompanied by volcanism (Silurian and Devonian polymetallic sulfide deposits). The Hercynian orogeny (northward subduction of the north Aquitaine plate followed by collision) evidenced by the intrusion of thick granitic belts (cassiterite-wolframite-bearing deposits). This was followed by intense fracturing (kaolin deposits) which was gradually replaced by other major fracturing episodes that may be interpreted as the distal impacts of Atlantic rifting on the old peneplaned Hercynian basement (Au, U, Sb, Pb-Zn-Ag, Ba).