HR: 0830h
AN: V21C-0528    [PDF]
TI: Global Climate Change Resulting From Voluminous Intrusive Basaltic Volcanism in Sedimentary Basins: the Methane Transport and Eruption Mechanisms
AU: * Svensen, H
EM: hsvensen@geo.uio.no
AF: Physics of Geological Processes, University of Oslo PO Box 1048 Blindern, Oslo, 0316 Norway
AU: Planke, S
EM: planke@vbpr.no
AF: Physics of Geological Processes, University of Oslo PO Box 1048 Blindern, Oslo, 0316 Norway
AU: Planke, S
EM: planke@vbpr.no
AF: Volcanic Basin Petroleum Research, Oslo Research Park, Oslo, 0349 Norway
AU: Jamtveit, B
EM: jamtveit@geo.uio.no
AF: Physics of Geological Processes, University of Oslo PO Box 1048 Blindern, Oslo, 0316 Norway
AU: Podladchikov, Y
AF: Physics of Geological Processes, University of Oslo PO Box 1048 Blindern, Oslo, 0316 Norway
AU: Rey, S S
EM: sebastian@vbpr.no
AF: Volcanic Basin Petroleum Research, Oslo Research Park, Oslo, 0349 Norway
AU: Malthe-S${\o}$renssen, A
EM: malthe@fys.uio.no
AF: Physics of Geological Processes, University of Oslo PO Box 1048 Blindern, Oslo, 0316 Norway
AB: The methane production potential in metamorphic aureoles surrounding voluminous sheet intrusions in sedimentary basins can be sufficiently large to trigger global climate change and mass extinctions. However, a causal relationship between global heating and greenhouse gasses formed by metamorphic reactions requires a mechanism for fast fluid transfer between the source region and the atmosphere. We propose that hydrothermal vent complexes may provide such fluid-migration pathways. These complexes consist of an upper crater-, dome- and eye-shaped part located at the paleosurface, and a lower cylindrical conduit zone connecting the upper part with the tip of a sill intrusion. Field evidence and numerical modelling shows that hydrothermal vent complexes are formed by explosive release of fluids and gasses, but also that the structures are commonly re-used for later slow fluid migration. The structure and formation of hydrothermal vent complexes are similar to mud volcanoes, whereas the pressure build-up mechanisms are different. We have identified $>$700 hydrothermal vent complexes on seismic data in the V${\o}$ring and M${\o}$re basins, and several hundred vent complexes are located onshore in the Karoo basin in South Africa. The diameter of the upper parts of the vent complexes range from several hundred meters to $>$10 km. More than 95${%}$ of the vent complexes in the V${\o}$ring and M${\o}$re basins are located near the Top Paloecene level, biostratigraphic dated as 55.0 to 55.8 m.y. in one borehole penetrating the upper part of a hydrothermal vent complex. This date corresponds to the onset of the initial Eocene thermal maximum (IETM). Similarly, the Karoo igneous event (about 183 Ma) correlates with the start of the Early Toacian anoxic event. The hydrothermal vent complexes in the Karoo basin are located at the paleosurface just below the extrusive cover. Several vent complexes are also located in the deep parts of the Karoo basin close to the organic-rich layers such as the Whitehill Fm., suggesting that they may have formed by explosive release of carbon-rich gasses.
UR: http://www.fys.uio.no/pgp
DE: 1620 Climate dynamics (3309)
DE: 8409 Atmospheric effects (0370)
DE: 8429 Lava rheology and morphology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting