AN UNUSUAL OCCURRENCE OF SYNCHYSITE-(Ce) IN AMYGDULES FROM THE ESTEREL VOLCANIC ROCKS, FRANCE: IMPLICATIONS FOR RARE-EARTH ELEMENT MOBILITY

Thierry Augé (1) , Laurent Bailly (1) , Guillaume Wille (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

Certain basaltic flows of the Permian volcanism in the Esterel (France) are enriched at their top and bottom in amygdules containing various minerals. Some of these amygdules appear to be particularly enriched in synchysite-(Ce), developed as fibrous aggregates together with chlorite and calcite. The rare earth element (REE) distribution pattern in individual amygdules appears very similar to that of the host basalt, suggesting that during the basalt's late hydrothermal evolution the REE were coherently remobilized and reprecipitated in the amygdules in the form of REE minerals. In such an environment, enriched in carbonate and F, the most stable REE mineral to crystallize from the hydrothermal solution was synchysite-(Ce), whose REE pattern has strong similarities to the host basalt.

Mots clés: alteration; amygdules basalts; calcite; carbonates; chemical composition; chlorite; chlorite group; crystal chemistry; electron probe data; Esterel; Europe; fluorides; France; halides; hydrothermal conditions; igneous rocks; metals mobility; occurrence rare earths; sheet silicates; silicates; solutions; synchysite; Var; volcanic rocks; Western Europe; Reyran River basin

Domaines: Sciences de la Terre

Thierry Augé, Laurent Bailly, Guillaume Wille. AN UNUSUAL OCCURRENCE OF SYNCHYSITE-(Ce) IN AMYGDULES FROM THE ESTEREL VOLCANIC ROCKS, FRANCE: IMPLICATIONS FOR RARE-EARTH ELEMENT MOBILITY. The Canadian Mineralogist, 2015, 52 (5), pp.837-856. ⟨10.3749/canmin.1400012⟩. ⟨hal-03670649⟩