Aspects of Jurassic magmatism and faulting in western Dronning Maud Land, Antarctica: Implications for Gondwana break-up

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 σ₁ and perpendicular to σ₃ 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.