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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS017 Poster presentation 2387 Hydro-geothermal characters of the Moroccan Atlas Dr. Massimo Verdoya Dip.Te.Ris. Universit di Genova IASPEI Yassine Zarhloule, Abdenbi El Mandour, Paolo Chiozzi, Mimoun Boughriba, Abderrahim Lahrach The geological setting of northwestern Morocco is characterized to the west by the Maghrebide orogenic system, of Alpine age and referred as to the Rif domain, and to the east by the intra-continental Mesozoic-Cenozoic belt of the Middle Atlas. These ranges form the main recharge zones of deep water reservoirs. In the Middle Atlas there are several hydrogeological basins with minor shallow aquifers in the Plio-Quaternary terrains. A marly substratum separates the shallow groundwater from the deeper artesian aquifer, occurring in the high-permeability Liassic carbonatic sequences and extending throughout the region. The top of the carbonatic aquifer ranges from 200 to 1300 m depth, and water temperatures as higher as 50 C were recorded to about 500 m depth. Moreover, numerous springs with temperature larger than 40 C and a flow which may reach 40 l/s occur in this area. Geothermal data so far achieved, especially from deep exploration oil wells, point to an increase of terrestrial heat-flow density from the Rif to the Middle Atlas zone, from about 60 to more than 80 mW/m2, respectively. Possible explanations should be searched in the regional extensional tectonics which has affected this area in Plio-Quaternary times yielding intensive volcanic activity. The aim of this paper is to contribute to the hydro-geothermal characterization of northwestern Morocco by presenting results of measurements of rock thermo-physical properties and analyzing temperature data available from water wells reaching the Mesozoic terrains. A number of thermal conductivity measurements were carried out on a set of samples representative of the stratigraphic sequence of the Middle Atlas. The carbonatic lithotypes forming the deep aquifer show a relatively high thermal conductivity. Values range from 2.0- 3.1 W/(m K) in limestones to 4.6-5.0 W/(m K) in dolomites. Temperature depth profiles from boreholes characterized by upward flow of hot water fed by the carbonatic formation are available to 350-500 m depth. Temperature logs were analyzed by matching thermal data with models of vertical temperature distribution, which incorporate both heat and mass transfer. Thermo-hydraulic parameters were calculated from the coefficients of the advective models obtained by means of the least-square fitting method. The inferred temperature gradient above the advectively perturbed carbonatic formation exceeds 50 mK/m, thus locally boosting the heat-flow density to values larger than 100 mW/m2. Analytical modeling of heat and water transfer involved in the deep circulation was attempted along selected hydro-geological cross-sections. Several hypotheses of basal heat-flow density, porosity, aquifer thickness and water velocity were tested in order to fit the borehole thermal records. The results show that temperatures of the deep aquifer are compatible with a topographically driven flow in the carbonatic formations down to 600-1500 m depth, under conditions of enhanced geothermal gradient. Keywords: advection, deep aquifers

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS017 Poster presentation 2388 Time-dependent lithosphere thermal state in the Carpatho-Pannonian Area. a review based on heat flow data and modeling Dr. Crisan Demetrescu Natural Fields Institute of Geodynamics, Bucharest, Romania IASPEI Maria Tumanian The formation of the Carpahtians, their relationship with the foreland, as well as the present configuration and structure of the Carpatho-Pannonian area are the result of a long-term tectonic evolution of lithosphere under global and local forces. The evolution starts with the extensional regime of Triassic and Jurassic, includes the emplacement of Inner, Median and outer Dacides and of Transylvanides in Cretaceous, followed by the deposition of the post-tectonic cover in the Transylvanian and Pannonian domains, and ends in Neogene, with overthrusting of Moldavides in the Eastern Carpathians and the formation of Transylvanian and Pannonian basins as a result of compressional and, respectively, of extensional deformation of lithosphere. Episodes of volcanism accompany these processes. The paper reviews the time-dependent thermal effects of tectonic processes involving the entire lithosphere (pre-Miocene oceanic subduction and Miocene continental collision in the Eastern Carpathians, extension in the Pannonian basin) or only its upper part (flysch nappes formation in the Eastern Carphatians, Neogene volcanism, Neogene sedimentation and erosion in the main subsident areas, namely the Pannonian, Transylvanian and Focşani depressions), discussed the heat flux budget of the lithosphere based on surface heat flux data and tectonic processes modeling and attempts at obtaining a comprehensive image of the temperature field and rheological structure of the lithosphere in the study area. Keywords: heat flow, geodynamic processes, thermal structure

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