Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663560
Title: Geochemical study of processes in granulite facies migmatites from Prydz Bay, eastern Antarctica
Author: Watt, Gordon Richard
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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Abstract:
Partial melting has been proposed as a mechanism for producing the low aH2O conditions characteristic of granulites, but the extent to which melts produced by water-undersaturated partial melting can be removed from granulite-facies migmatite complexes is less well understood. Three leucogneiss suites produced by water-undersaturated partial melting under high temperature, moderate pressure (6Kbar, 860°C), granulite-facies conditions have been distinguished on the basis of geochemistry and petrography. Type 1 Leucogneisses from the Brattstrand Bluffs coastline, eastern Antarctica, have near minimum-melt major element compositions (high SiO2, low Fe2O3, MgO) low Zr, Th and LREE concentrations, positive Eu anomalies and limited entrained residual material, suggesting efficient segregation of small melt volumes before equilibration with the source. The limited dissolution of accessory phases in water-undersaturated melts has led to a concentration of monazite and zircon and high LREE concentrations in melanosomes. Melting depleted the plagioclase component of the metapelite source rocks almost completely, producing melts with high Eu concentrations. Granitic melts formed under vapour-present conditions are unlikely to show such extreme LREE and HREE depletion or positive Eu anomalies, even at high degrees of partial melting. Type 2 Leucogneisses have high Fe2O3, MgO and TiO2 contents and were formed at higher degrees of melting than the Type 1 Leucogneisses. Consequently they were more viscous, less extractable and more likely to entrain restitic and peritectic phases as the metapelitic source rocks lost their coherence. Type 3 Leucogneisses have strongly enriched Zr, Th and LREE abundances, negative Eu anomalies, and Zr/Zr* and LREEt/LREEt* >1 resulting from preferential accessory phase entrainment.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.663560  DOI: Not available
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