Use of Fluid Inclusions for the Discrimination of Multi-Source Components and P-T-X Reconstruction in Geothermal Systems: Application

Abstract

Although geothermal systems would provide excellent materials for the description of major processes such as mixing, boiling, cooling, the studies have rarely been conducted in a similar way than for ancient systems, using a detailed petrography of fluid inclusions as a function of the mineral sequences and assemblages for a correct description of the evolution with time of trapped fluids. The application of fluid inclusion systematics to the Larderello field has shown that distinct fluid sources and fluid production mechanisms characterize the reservoir since a few million years. Several fluid components be used to discriminate the different processes such as Li chloride (considered in that case as a magmatic fluid component), and issued from the contact of C-rich sediments in the early stages of the activity, Ca and Mg chlorides attesting water-rock interactions in specific geologic formations of the reservoir. Fluid inclusions give local information on welldefined zones within the reservoir. Furthermore, they are the only direct information on paleofluids which have circulated through the rocks, and may yield very useful data on the P-T evolution with time of a given part of the field during pre-exploitation stages.