Regional geological investigation in Dronning Maud Land
Geological mapping and investigations of the mountain chain in Dronning Maud have been carried out during several Norwegian Antarctic Research Expeditions (NARE) over the last 30 years. Base on this work, the Norwegian Polar Institute has published a series of geological maps in the scale 1:100,000 and 1:150,000. The geological maps and the supplementary text cover the area between 0°35’W and 6°E, and include information on geomorphology, glaciology, flora and fauna. At present, the project focuses on covering the areas in DML, which are not covered by other countries' geological surveys. A compilation of a geological correlation map of entire Dronning Maud Land is planned.
In addition to collecting geological map data, petrological studies are undertaken in co-operation with national and foreign institutions. The high-grade continental crust exposed at the surface today in Dronning Maud Land, Antarctica, represents a deeply eroded section through the central part of a 600-500 Ma old mountain belt. Geochronology has demonstrated that the oldest rocks in Dronning Maud Land have suffered two episodes of deformation, high-temperature metamorphism and partial melting. The first event took place around 1150-1000 million years ago, whereas the younger deformation event is related to the ca. 500 Ma Pan-African orogeny. During the latter episode, large volumes of intrusive rocks intruded the high-grade and strongly deformed basement consisting of gneisses and migmatites. The igneous suite includes charnockites, granites and quartz syenites and several generations of dykes. Charnockites and granites occur with local gneissic overprint, while quartz-syenites are mostly post-kinematic.
Metamorphic studies of granulites and migmatites has revealed a tectonothermal evolution characterised by near-isothermal decompression. The exhumation path and extensional structures indicate rapid tectonic exhumation, which is most likely related to a late-orogenic collapsing phase of the Pan-African orogen.
Spectacular examples of fluid-rock interaction phenomena are widespread in central Dronning Maud Land. The fluid-rock interactions occur as well-developed alteration zones around granitic dikes, pegmatites and aplitic veins, which cross-cut anhydrous, dark colored granulites and quartz syenites. The alteration transforms the originally dark granulite facies rocks into light colored rocks, independent of lithological variability. The excellent exposure of the phenomenon in Dronning Maud Land provides an idea of how short term fracture-controlled fluid infiltration and related retrogression can affect extensive crustal volumes.
Deltakere
Prosjektleder: Synnøve Elvevold