Evaluating the Kuunga Collisional Orogeny in Dronning Maud Land - progress and the future

Abstract

Geological research in SANAP from 2012 to 2016 has largely focussed on evaluating a hypothesis describing a large tectonic nappe collisional model for the amalgamation of Gondwana [1] termed the Kuunga Orogeny [2]. Structural studies in Straumsnutane, Sverdrupfjella and Gjelsvikfjella confirm widespread late top-to the SE directed deformation involving quartz veining, folding and faulting in Straumsntane, and folding, shearing and numerous phases of granitoid vein intrusion in Sverdrupfjella and Gjelsvikfjella. Strain analysis on the various structures indicate similar orientations for the diverse structures supporting the interpretation and correlation of the structures. Age constraints on the syn-tectonic granitoid vein intrusions indicate that they are mostly at least Cambrian at ~470-~505Ma (Rb/Sr and U/Pb SHRIMP zircon) and ~540Ma (Rb-Sr age) being indicated for the youngest two phases of intrusion. Structural interpretations suggest that the younger ~490Ma phase of deformation was compressional in nature whereas the ~s40Ma age of deformation was extensional. The whole rock major and trace element chemistry as well as radiogenic isotope data show differences which suggest that the youngest veins were sourced in older crust in contrast to the older vein phase which was sourced from more juvenile crust. The distribution of these veins may suggest the two granitoid were sourced from separate tectonic blocks within the mega-nappe structure. Radiogenic isotope studies on samples from the country rocks hosting the granitoid veins also show widely varying characteristics which show similar distributions to various crustal blocks within a broader Gondwana configuration. 40Ar/39Ar data from biotite and amphibole from samples from Kirwanveggan and Sverdrupfjella were obtained with a view to studying the uplift history of these areas. In Sverdrupfjella the ages are similar around ~500Ma with differences between biotite and amphibole ages being ~20-30Ma.These ages are similar to younger granitoid intrusion suggesting rapid uplift and cooling in Sverdrupfjella. Biotite ages in Kirwanveggan are similar to Sverdrupfjella except for the most southerly sample from Skappelnabben which shows a disturbed age of ~770Ma. In contrast in Kirwanveggan amphibole ages increase from NE to SW from ~500Ma to ~1200Ma suggesting a crustal gradient and differential heating and cooling related uplift. Suggestions for future research are made.