Progress in the Gondwana Amalgamation and Correlation Project

Abstract

The focus of the project has been two fold namely comprising a study of the Jurassic dykes related to the breakup of Gondwana and a study of rocks and structured related to the amalgamation of Gondwana. The dyke study has provided detail on the varying orientation of dykes intruded and has also shown that the age of dyke emplacement occurred over a far wider range in time than previously thought extending from ~170Ma to 216Ma. The age range has implications for the inferred mechanism of Gondwana breakup whether tectonically driven or plume-magmatism driven. Studies of the paleomagnetic poles are also in progress. In addition to the Jurassic dykes, an older new dyke swarm of age ~720Ma has been identified in the Borgmassivet area. This dyke swarm has equivalents in Zimbabwe. The Gondwana amalgamation study has recognised a wide variation of magmatic activity of ages between ~520Ma to 480M with dominantly acidic compositions but including volumetrically limited basic compositions. Early magmatism around ~520Ma is extensional in nature with juvenile isotopic characteristics. In contrast granitic veins emplaced ~480-490Mashow syntectonic emplacement in a top to S and SE direction with the veins having evolved isotopic characteristics implying melt genesis from an older source at depth. Basement isotopic studies combined with published and new geochronology define at least two, potentially three distinct terranes, probably separated by tectonic boundaries. These boundaries can locally be correlated to aeromagnetic domains. An Ar-Ar study on the age of mica and amphibole focussing on the uplift history show that uplift and erosion up to ~530Ma was limited to Sverdrupfjella and Kirwanveggan and places limits on the areal extent Kuunga Orogeny. The various chemical and structural data collected are consistent with a tectonic nappe collisional model proposed in 2008 with collision between N. and S. Gondwana. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.