HR: 1340h
AN: V23A-0679    [Abstracts]
TI: Using micro-isotopic approaches to evaluate the origin and emplacement mechanism of the Basement Sill, Dry Valleys, Antarctica
AU: * Davidson, J P
EM: j.p.davidson@durham.ac.uk
AF: University of Durham, Dept. of Earth Sciences, South Rd, Durham, DH1 3LE United Kingdom
AU: Jerram, D
EM:
AF: University of Durham, Dept. of Earth Sciences, South Rd, Durham, DH1 3LE United Kingdom
AU: Petford, N
EM: N.Pet@kingston.ac.uk
AF: Kingston University, Centre for Earth & Environmental Science Research, Penrhyn Road, Kingston-upon-Thames, KT1 2EE United Kingdom
AU: Marsh, B
EM: bmarsh1@jhu.edu
AF: Johns Hopkins University, K. Blaustein Dept. Earth & Planetary Sciences, 34th & Charles Streets, Baltimore, MD 21218 United States
AB: Isotopic fingerprinting of mineral phases in volcanic rocks has been successfully employed recently to track magma evolution and to identify populations from different sources. Integration of this approach with textural characterisation allows chemical evolution to be integrated with physical changes (growth, nucleation, mixing). In plutonic rocks this approach has been shown to be valid, despite the potential for isotopic re-equilibration during more protracted cooling than volcanic rocks. In fact, the degree of isotopic reequilibration can be used to constrain the cooling rate of the rock, which, in turn, relates to the emplacement history. At the Rum layered mafic intrusion, NW Scotland, isotopically distinct plagioclase cores and rims suggest relatively rapid cooling (at the scale of an individual layer) of the order 0.1°C per year, consistent with sill-like emplacement. The origin of isotopic variation is consistent with growth from a progressively contaminated magma prior to transport and deposition. The Basement Sill of the Dry Valleys Complex, Antarctica, contains an opx-rich tongue claimed to be emplaced as a crystal mush into a crystal-poor magmatic envelope. Given the broadly similar dimensions and compositions of the Rum Intrusion and Basement Sill we expect to be able to use micro-isotopic analyses of cumulus plagioclase crystals in the opx tongue to a) determine whether the magmatic source is the same as the rest of the sill, b) constrain the effects of contamination during crystal growth and emplacement and c) constrain cooling pathways
DE: 3618 Magma chamber processes (1036)
DE: 8434 Magma migration and fragmentation
DE: 8439 Physics and chemistry of magma bodies
DE: 9310 Antarctica (4207)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005