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Department of Geology, University of Pretoria, Pretoria, South Africa, 0002
Jurassic magmatism in Sverdrupfjella, western Dronning Maud Land, Antarctica, is manifested as saturated and undersaturated syenite intrusions and associated dykes which range in composition from dolerite and nepheline syenite to quartz-rich compositions. Dykes in the study area show two dominant orientations namely N-S and NE-SW. Faults and joints are oriented slightly north of east. In a Gondwana context, the NE dykes, which appear to be older (c. 200 Ma), are oriented approximately parallel to
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This 250-word extract was created in the absence of an abstract.
1 and perpendicular to 3 for the transpressional first stage of Gondwana break-up postulated by Cox in 1992. The N-S dykes and associated alkaline intrusions appear to be c. 170 Ma old and do not correlate with any of the stages of Cox. Faulting and jointing, which postdate the Tvora Syenite intrusion, appear to correlate with stage 2 of Cox indicating that this stage was amagmatic in Sverdrupfjella. Comparison of dolerite dyke compositions with those in a broader Gondwana context, shows that they have compositions typical of the ‘normal’ Karoo Province in southern Africa characterized by lower Zr, P2O5 and TiO2 contents and therefore are typical of dykes derived from Proterozoic metamorphic terrains.
