HR: 0800h
AN: V11A-0363    [Abstracts]
TI: Saucer-shaped sills: occurrences, emplacement and implications
AU: Sørenssen, A
EM: anders.malthe-sorenssen@fys.uio.no
AF: Physics of Geological Processes - PGP University of Oslo, POBOX 1048 - Blindern, Oslo, 0316, Norway
AU: * Polteau, S
EM: polteau@fys.uio.no
AF: Physics of Geological Processes - PGP University of Oslo, POBOX 1048 - Blindern, Oslo, 0316, Norway
AU: Mazzini, A
EM: adriano.mazzini@fys.uio.no
AF: Physics of Geological Processes - PGP University of Oslo, POBOX 1048 - Blindern, Oslo, 0316, Norway
AU: Galland, O
EM: olivier.galland@fys.uio.no
AF: Physics of Geological Processes - PGP University of Oslo, POBOX 1048 - Blindern, Oslo, 0316, Norway
AU: Planke, S
EM: planke@vbpr.no
AF: VBPR, Forskningparken, Gaustadalléen 21, Oslo, 0349, Norway
AB: Magmatic sill intrusions commonly exhibit saucer geometries in undeformed sedimentary basins and volcanic rifted margins. Despite their broad occurrences, these saucer-shaped structures are poorly known. The aim of this contribution is to present an overview of the geological settings of saucer-shaped intrusions, present an updated emplacement model and to encourage their identification on Earth and on other planets. Saucer-shaped sills are intimately related to large igneous provinces associated with undeformed sedimentary basins (e.g. South Africa, Siberia, North Sea Basin…). These intrusions can act as water reservoirs (e.g. in the arid South African Karoo Basin) and affect oil maturation and migration pathways. The current emplacement models are based on the analysis of the intrusion geometry and their spatial relationships with potential feeders, not on the knowledge of magma flow directions. New anisotropy of magnetic susceptibility data suggests that saucer- shaped sills are emplaced radially and that the overburden influence the magnetic fabric. Additional analogue and numerical modeling show that saucer-shaped sills are generated by the interactions of a shallow fracture growing radially towards the free-surface and the overburden deformations. A correlation factor of 4-5 between the depth of emplacement and inner diameter exists for saucer-shaped sills. Saucer-shaped intrusions can develop in materials with totally different physical properties (i.e. elastic and Mohr-Coulomb materials) and therefore represent a fundamental geometry in natural systems. We also suggest that saucer-shaped sills should be recognized on extra-terrestrial planets with known intense volcanic activity (e.g. Mars and Venus).folk
UR: http://folk.uio.no/polteau
DE: 8434 Magma migration and fragmentation
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting