HR: 17:45h
AN: V14C-08    [Abstracts]
TI: Basement Sill of the Jurassic Ferrar Large Igneous Province, Antarctica: Constraints from its PGE Abundance Patterns on Magma Source Characteristics and Crystallization Processes
AU: * Mukasa, S B
EM: mukasa@umich.edu
AF: Univ. Michigan, Dept. Geological Sciences, Ann Arbor, MI 48109 United States
AU: Ravizza, G
EM: ravizza@hawaii.edu
AF: Univ. Hawaii, Dept. Geology & Geophysics, Honolulu, HI 96822 United States
AU: B‚dard, J
EM: jbedard@nrcan.gc.ca
AF: Geological Survey of Canada, 490 de la Couronne, Quebec, PQ G1K 9A9 Canada
AU: Fleming, T
EM: flemingt1@southernct.edu
AF: Univ. Southern Connecticut, Dept. Earth Sciences, New Haven, CT 06515 United States
AU: Boudreau, A
EM: boudreau@duke.edu
AF: Duke Univ., Nicholas School of the Environment & Earth Sciences, Durham, NC 27708 United States
AU: Marsh, B D
EM: BMarsh@gibbs.eps.jhu.edu
AF: Johns Hopkins Univ., Dept. Earth & Planetary Sciences, Baltimore, MD 21218 United States
AB: The Basement Sill in the Dry Valleys of southern McMurdo Sound is part of a sill complex interconnected by dikes, emplaced in a Paleozoic mobile belt developed adjacent to the East Antarctic craton. This complex of sills is linked both geochemically and spatially to intrusive, hypabyssal and volcanic rocks of the Ferrar Magmatic Province (FMP), a Mid Jurassic a large igneous province (LIP) associated with fragmentation of the supercontinent Gondwanaland. All components of this LIP, including the Dufek intrusion, lavas and sills, were emplaced at 184 ń 1 Ma over the entire ~3,000-km length of the Transantarctic Mountains, based on zircon, baddeleyite and rutile U-Pb geochronology. Understanding the production of copious amounts of magma in a short amount of time is fundamental to understanding LIPs in general. Mantle plumes provide an attractive and plausible mechanism for generating short-duration, voluminous magmas in LIPs while at the same time providing a mechanism for the often concurrent break-up of supercontinents. For the FMP, however, this model has been challenged by proponents of the idea that melting resulted from the decompression of a fossil subduction zone along the Proto-Pacific margin of Gondwanaland, disaggregated by the rifting related to plate rearrangements during supercontinent break up. PGE abundance patterns, which are unique for different tectonic settings, are being generated to evaluate these two models. PGE data will also be used to evaluate magma chamber processes, such as development of layering - perhaps by crystal sorting - during which Pt and Pd should be strongly incompatible relative to Ir and Os under S-undersaturated conditions. In addition, fluid inclusions in orthopyroxene and plagioclase primocrysts, and studies of halogens in apatite (Boudreau, pers. comm.) suggest that magmas reached volatile saturation in the Basement Sill. Volatile transfer process would be expected to impact the transport of PGE's and S, a model that will be tested by our data. One advantage the Basement Sill has over the much larger layered mafic intrusions, such as the Dufek intrusion of the same magmatic province, is superb preservation of primary igneous textures without the veil often cast over larger layered intrusions by subsolidus re-equilibration.
DE: 3618 Magma chamber processes (1036)
DE: 3625 Petrography, microstructures, and textures
DE: 8434 Magma migration and fragmentation
DE: 8439 Physics and chemistry of magma bodies
DE: 8450 Planetary volcanism (5480, 6063, 8148)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005