HR: 14:15h
AN: V53D-03 INVITED    [Abstracts]
TI: Dufek Layered Mafic Intrusion and Basement Sill, Antarctica: Constraints on their Magma Sources Based on PGE Abundance Patterns, Nd-Sr-Pb Isotopic Ratios and Trace Element Modeling
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, SOEST, Honolulu, HI 96822, United States
AU: Bédard, J
EM: jbedard@nrcan.gc.ca
AF: Geological Survey of Canada, 490 de la Couronne, Quebec, PQ G1K 9A9, Canada
AU: Choi, S
EM: chois@kopri.re.kr
AF: Korea Polar Research Institute, 7-50 Songdo Techno Park Songdo-dong, Yeonsu-gu Incheon, 406-840, Korea, Republic of
AU: Andronikov, A V
EM: andron@umich.edu
AF: Univ. Michigan, Dept. Geological Sciences, Ann Arbor, MI 48109, United States
AU: Fleming, T
EM: fleming@southernct.edu
AF: SCSU, Dept. Earth Sciences, New Haven, CT 06515, United States
AU: Marsh, B D
EM: bmarsh@jhu.edu
AF: Johns Hopkins Univ., Dept. Earth & Planetary Sciences, Baltimore, MD 21218, United States
AB: The Dufek layered mafic intrusion in the Pensacola Mts. and Basement Sill in the Dry Valleys of southern McMurdo Sound are part of the Ferrar large igneous province (FLIP), emplaced in a Paleozoic mobile belt developed adjacent to the East Antarctic Craton during the Mid Jurassic. Zircon, baddeleyite and rutile U-Pb dating shows that emplacement occurred in a short amount of time at 184 ± 1 Ma, contemporaneously with fragmentation of the supercontinent Gondwanaland. Understanding the rapid production of copious amounts of magma in a short time is fundamental to understanding LIPs in general. Mantle plumes provide an attractive 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. However, plagioclase and pyroxene initial Sr, Nd and Pb isotopic ratios from the Dufek Intrusion and whole-rock samples from the Basement Sill do not resemble the isotopic signatures of lavas associated with South Atlantic hotspots which are closest to this body. Furthermore, PGE abundance patterns for the FLIP appear inconsistent with the plume interpretation. Extreme depletions in Os and Ir compared to the Ru, Pt and Pd abundances – with the Os/Ir ratios in the range of 0.1 to 0.3 for these samples compared to the more commonly observed values close to 1 – are atypical of plume-derived magmas and are more consistent with the alternative view that the FLIP resulted from the decompression of a fossil subduction zone along the Proto-Pacific margin of Gondwanaland, disaggregated by the rifting related to plate rearrangements that occurred during supercontinent break-up.
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1036 Magma chamber processes (3618)
DE: 1038 Mantle processes (3621)
DE: 1115 Radioisotope geochronology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting