Hydrothermal activity and core complex formation at the Arctic Mid-Ocean Ridge: An overview of preliminary results of the H2DEEP expedition to the southern Knipovich Ridge at 73N

HR: 09:20h
AN: OS41C-05 [Abstracts]
TI: Hydrothermal activity and core complex formation at the Arctic Mid-Ocean Ridge: An overview of preliminary results of the H2DEEP expedition to the southern Knipovich Ridge at 73N
AU: * Pedersen, R B
EM: rolf.pedersen@geo.uib.no
AF: Centre for geobiology, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: * Pedersen, R B
EM: rolf.pedersen@geo.uib.no
AF: Department of Earth Science, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Thorseth, I H
EM: ingunn.thorseth@geo.uib.no
AF: Centre for geobiology, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Thorseth, I H
EM: ingunn.thorseth@geo.uib.no
AF: Department of Earth Science, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Olson, E
EM: olson@ocean.washington.edu
AF: School of Oceanography , University of Washington, Box 357940, Seattle, WA 98195, United States
AU: Hellevang, H
EM: helge.hellevang@geo.uib.no
AF: Centre for geobiology, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Hellevang, H
EM: helge.hellevang@geo.uib.no
AF: Department of Earth Science, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Okland, I
EM: ingeborg.okland@geo.uib.no
AF: Centre for geobiology, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Okland, I
EM: ingeborg.okland@geo.uib.no
AF: Department of Earth Science, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Baumberger, T
EM: tamara.baumberger@erdw.ethz.ch
AF: ETH Zurich, Institute for Mineralogy and Petrology, Clausiusstrasse 25, Zürich, CH-8092, Switzerland
AU: Lilley, M
EM: lilley@u.washington.edu
AF: School of Oceanography , University of Washington, Box 357940, Seattle, WA 98195, United States
AU: Bruvoll, V
EM: vibeke.bruvoll@geo.uib.no
AF: Department of Earth Science, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Mjelde, R
EM: rolf.mjelde@geo.uib.no
AF: Department of Earth Science, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Haflidason, H
EM: haflidi.haflidason@geo.uib.no
AF: Centre for geobiology, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AU: Haflidason, H
EM: haflidi.haflidason@geo.uib.no
AF: Department of Earth Science, University of Bergen, Norway, Allegaten 41, Bergen, 5007, Norway
AB: The oblique spreading Mohns Ridge passes into the highly oblique spreading Knipovich Ridge through a near 90 degree bend in the ridge axis at 73-74N. Multibeam mapping of this area shows that a 30 km long axial volcanic ridge (AVR) with a 500m high summit occupy the rift valley floor in the central part of the bend where the axis is perpendicular to the spreading direction. The volcanic activity decreases northwards as the obliquity of the spreading increases and this is associated with an increase in the water depth from 2000-2500 m to 3000-3500 m. A hydrothermal plume was located at the eastern side of the AVR with methane values reaching 260 nmol/l and hydrogen values 53 nmol/l. These anomalies are associated with small positive temperature anomaly, but no significant particle anomaly could be detected. The rift valley in the area is partly filled with sediments derived from the nearby Bjornoya fan, and reflection seismic profiles across the ridge demonstrate that sediments thicknesses in the rift valley locally exceeds several hundred meters. Gravity cores of the upper 4 m of these sediments show multiple glass- and iron-rich laminas and layers, demonstrating that these sediments represent a record of hydrothermal and volcanic activity in the area. Seamounts at the western flank of the ridge extend to 600 m below sea level and are limited by low angle detachment faults to the east. A flat summit area suggests that one of the seamounts has been at or close to sea level. Gabbros, troctolites and serpentinites were sampled from the fault surfaces, demonstrating that lower crust and mantle rocks have been exhumed in the area, and bathymetry data indicates that this oceanic core complex cover an area of about 500 km2. A younger detachment fault appears to develop at the inner rift wall just west of the AVR. The rift valley sediments are affected by the faulting and the seismic stratigraphy of these sediments constrain the history of core complex formation.
DE: 1021 Composition of the oceanic crust
DE: 1032 Mid-oceanic ridge processes (3614, 8416)
DE: 1034 Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424)
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting