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

Abstract 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 basalt9s 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.