Tuesday, 28 August 2007 - 2:50 PM
2.P1.D-5
Evolution of low-Ti and high-Ti rocks of the Jurassic Ferrar Large Igneous Province, Antarctica: Constraints from crystallisation experiments
Ricarda Hanemann and Lothar Viereck-Goette. Institut fuer Geowissenschaften, Friedrich-Schiller-Universitaet Jena, Burgweg 11, 07747 Jena, Germany
The Jurassic Ferrar large Igneous Province comprises two compositionally distinct magma series. In order to describe the differentiation history of these low-Ti and high-Ti series, equilibrium crystallisation experiments have been performed at 1100 deg C and 2 kbar in internally heated pressure vessels. The experiments were conducted under variable redox conditions and water activities using a chilled margin sample from a low-Ti sill in northern Victoria Land as starting material. The phase relations and phase compositions of the experimental products exhibit systematic variations with changing run conditions. Based on the comparison of the experimental results with the compositional differences analysed in the natural low-Ti and high-Ti rocks, a model is proposed after which the high-Ti magmas differentiated under lower oxygen fugacity and water activity at lower pressures compared to the low-Ti magmas.