MICROANALYSIS OF PRIMARY FLUID INCLUSIONS IN HALITE - CONSTRAINTS FORAN EVAPORITIC SEDIMENTATION MODELING - APPLICATION TO THE MULHOUSE BASIN (FRANCE)

The chemistry of the waters from which the evaporitic minerals crystal lized in the lower part of the Salt IV unit of the Mulhouse Basin (Fra nce) has been investigated. The lithological and fluid inclusion data have been compared to the output data of the mass transfer program NEW EQUI which simulates the change in brine composition during its evapor ation advancement. The results show that the evolution of the composit ion of the brine is compatible with the calculated sequence of evapora tion of a parent water corresponding to a seawater modified by CaCl2-r ich hydrothermal water In the studied sequence fluid inclusion data pr ovide useful constraints for reconstructing the paleoenvironment contr olling the evaporitic sedimentation. They also provide data on the wat er stratification in the basin and on its connectivity with the open s ea, and important parameters controlling the productivity (possible so urces for the nutrients) and the preservation of organic matter in the sediment.