Permian basalts and trachytes from Esterel (SE France): a transitional tholeiitic suite emplaced during lithosphere thinning

Geochemical (major, trace and rare earth elements) and isotopic (Nd-143/Nd- 144) compositions of lavas emplaced in the Esterel Massif (eastern Provence , France) at the end of the Permian allow to estimate the evolution of the continental lithosphere between the end of the Hercynian orogenesis and the beginning of the Tethyan rifting. Basalts from Agay basin and trachyte fro m Batterie des Liens belong to a transitional tholeiitic suite, characteriz ed by negative Nb and Ta anomalies (relative to N-MORB) and homogeneous eps ilon Nd-(T=250Ma) ratios, close to the Bulk Earth. This suggests that the b asalts from Agay basin and trachyte from Batterie des Lions derived from th e partial melting of a mantle contaminated by lower continental crust. Maur e Vieille trachytes differ from the differentiated rocks of the transitiona l suite by higher heavy rare earth abundances and epsilon Nd-(T=250 Ma) of +4/+5. These high eNd ratios suggest that the Maure Vieille traehytes could derive from the partial melting of a more depleted source, likely an asthe nospheric mantle. The isotopic compositions of the Permian lavas from Esterel suggest the thi nning (and perhaps the disparition) of the lithospheric mantle which is ass ociated at the surface with a NNW-SSE extension. The progressive change rec orded in Agay basin from a stretching regime to a strike-slip regime may be related to the end of the lithospheric thinning and of the Permian magmati sm.