Transport Processes in the Fault Zones of the Crystalline Crust - A Conceptual Model for the Natural Flow, Discussed for the KTB Area -

HR: 0800h
AN: H11B-0293 [Abstracts]
TI: Transport Processes in the Fault Zones of the Crystalline Crust - A Conceptual Model for the Natural Flow, Discussed for the KTB Area -
AU: Grгle, W
EM: Werner.Graesle@dwd.de
AF: German Weather Service(DWD), Dr. Werner Graesle Deutscher Wetterdienst (DWD) FE12/AP03 - Assimilation & Modelle Kaiserleistr. 35, Offenbach, D-63067 Germany
AU: * Kessels, W
EM: w.kessels@gga-hannover.de
AF: Leibniz Institute for Applied Geosciences, Dr. Winfried Kessels Institut f〉 Geowissenschaftliche Gemeinschaftsaufgaben Stilleweg 2 30655 Hannover, Hannover, 30655 Germany
AB: To prove the geochemical and isotopic results of the scientific drilling test site KTB Oberpfalz a conceptual numerical model for the natural flow and transport process was build with the program FEFLOW. With the calculation we answered the question how it is possible that the isotopic components of the fluid recovered from the deep crystalline rock indicate a west - east fluid flow from a topographic lower sedimentary area to the higher hilly area of the KTB site. In particular CH$_4$ isotopic signature of the gas indicates the CH$_4$ is migrated from the western sedimentary formation into the crystalline formation. Large transport paths of sedimentary components in the crystalline rock with a high topography are investigated and postulated by different scientist world wide. To explain this phenomenon, the existence of a permanent, density driven flow with simultaneous dilution is suggested. Such a system explains fluid flow in the deep crust against the higher level of the groundwater surface. By means of a simple convection model it can be shown that the density driven dilution motor can create a more effective hydraulic potential than a motor driven by precipitation and the related hydraulic head of the groundwater surface. Furthermore, with common geothermal gradients, the geothermal convection motor is weak compared to the fluid density effects discussed here. The numerical calculation shows, that the density driven flow model escribed above is realistic and can produce in great depth hydraulic flow against the direction of the shallow groundwater flow. A coupled hydraulic - geothermal FE calculation was also done. The downward directed water flow in the fault zones produce here a cooling of $0.5\, ^\circ $C after a simulation time of 2000 a. This results agrees well with the observed temperatures. \textbf{References:} KESSELS W., W. GR\"ASLE (2002): Mineral Dilution and Shallow Groundwater Dynamics as Motor to Drive Fluid Migration in the Deep Crystalline Crust - Interpretation of Hydraulic Investigations From the 9101 m Super Deep German Continental Drillhole. - Fall Meeting of the AGU, 6.\,-\,10. Dec. 2002, San Francisco/California/USA, paper T21A 1081. GR\"ASLE W., W. KESSELS (2003): Three dimensional modelling of fluid movement and transport of fluid components in the SE1 and SE2 fault zones driven by processes on a regional scale - Hydraulic and tracer test interpretation regarding the stress coupling and the probability of the hydraulic induced shear failures and as technical support. - ICDP Kolloquium, 26.\,-\,28. March 2003, Mainz, 4 S.
UR: http://www.gga-hannover.de
DE: 8010 Fractures and faults
DE: 1899 General or miscellaneous
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 3210 Modeling
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting