Palaeomagnetic dating of widespread remagnetization on the southeastern border of the French Massif Central and implications for fluid flow and Mississippi Valley-type mineralization

Bernard Henry (1) , Henri Rouvier (1, 2) , Maxime Le Goff (1) , David Leach , Jean-Claude Macquar (2) , Jacques Thibieroz (2) , Michael T. Lewchuk (1)

1 CNRS - Centre National de la Recherche Scientifique
2 UPCité - Université Paris Cité

Palaeomagnetic dating techniques have been applied to determine the age of fluid migration that produced the Mississippi Valley-type (MVT) Pb-Zn-Ba-F deposits in the Cévennes region of southern France. 15 sampling sites in two gently deformed areas around the Largentière and Croix-de-Pallières mines on the Cévennes border were selected for palaeomagnetic study. They yielded a very well-defined direction of remagnetization corresponding to an Early-Middle Eocene age. This remagnetization cannot be related to the formation of magnetite as a result of the transformation of smectite to illite because the latter has been well dated as a Mesozoic event. The magnetic overprint in this area is related to a chemical phenomenon during fluid migration. The age of remagnetization corresponds to a major uplift in the Pyrénées mountains, located to the south of the Cévennes. This implies that fluid migration occurred from the south to the north as a result of hydraulic head established in the Pyrénées orogenic belt during orogenesis and suggests that the MVT deposits in the Cévennes region formed from a gravity-driven fluid system as described by Garven & Freeze (1984a,b).

Mots clés: fluid migration; Massif Central; mineralization; palaeomagnetism

Domaines: Planète et Univers [physics]

Bernard Henry, Henri Rouvier, Maxime Le Goff, David Leach, Jean-Claude Macquar, et al.. Palaeomagnetic dating of widespread remagnetization on the southeastern border of the French Massif Central and implications for fluid flow and Mississippi Valley-type mineralization. Geophysical Journal International, 2001, 145, pp.368-380. ⟨10.1046/j.0956-540x.2001.01382.x⟩. ⟨insu-03597757⟩