PRELIMINARY T-T-X-SIGMA RECONSTRUCTION OF FLUID PALEOCIRCULATIONS IN THE MESOZOIC FORMATIONS OF THE MORTE-MERIE BOREHOLE (ARDECHE MARGIN, SOUTH-EAST BASIN OF FRANCE)

A preliminary investigation of trapped fluids in the MMI-borehole show s the following : (i) at the pre-rift stage, recrystallization of Tria ssic strata-bound sulphates by cold diluted fluids (T < 70 degrees C; continental waters, cf. BA-I) and emplacement of barytes (209 m); (ii) at the burial stage, in the Lower-Middle Triassic formations, fluid c irculations and mixing along strata, sometimes in marked thermal diseq uilibrium, and partial decrepitation of fluid inclusions in early sulp hates; in the Upper Trias-Lower Hettangian, Vertical influx of hot pul sating fluids (up to 170 degrees C), trapped in dolomite cracks, and h ydraulic fracturing; (iii) after the uplift, during the alpine orogene sis (Pyrenean phase?) opening of gypsum-filled horizontal tension crac ks and late sulphate crystallizations.