HYDROCELL-II. Quantitative Erfassung hydrothermaler Konvektionszellen in der oberen ozeanischen Kruste Abschlussbericht

During research cruise SO-111 on RV SONNE (21.8 - 15.9.1996) reflexion and refraction seismic investigations as well as geothermal measurements were successfully completed on the eastern flank of the Juan de Fuca Ridge at about 48 N (Endeavour Segment). The geothermal measurements were concentrated on a young sedimentary basin at the Cobb Offset. The interpretation of the heat flow data shows an inverse correlation of heat flow and sediment thickness. This is a clear indication for the existence of an isothermal sediment basement boundary. At the eastern and western boundaries of the basin temperatures at the sediment basement boundary are depressed due to the influx of cold seawater in sediment-free outcrops. Extremely high heat flow at the eastern vulcanic ridge points to submarine hydrothermal outflow. The refraction studies on five ridge-parallel profiles from crustal ages of 0.5 to 1.8 ma in the area of the ODP-Leg 168 transect show a distinct increase of seismic velocity in Layer 2A with crustal age from 2.5 to 4.5 km/s with a 80 km long profile. This increase is in good agreement with refraction results from other ridge flanks. However the increase happens over a shorter time period as compared to other partially sediment covered ridge flanks. A possible explanation for this rapid increase are the high basement temperatures caused by the almost impermeable sedimentary seal of young and therefore hot crust. (orig.)Available from TIB Hannover: F99B169 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman