Geological studies in the Baalsrudfjellet nunatak between the Schirmacher Oasis and the Wohlthat Mountains to establish the continuation of the East African Orogen (EAO) in central Dronning Maud Land, East Antarctica

Abstract

The 600–660 Ma East African Orogen (EAO) granulites of the Mozambique Belt were correlated and extended into a coast marginal area of East Antarctica through the NNW–SSW-trending granulite-bearing Schirmacher Oasis. Tracing similarities in lithological association, granulite-facies metamorphism and geochronological data, the 640 Ma EAO was extended by another 110 km south of Schirmacher into the Humboldt Mountains in central Dronning Maud Land (cDML). Based on younger anorogenic magmatism east and west of the Humboldt Mountains, a 10–20 km-wide linear corridor of the EAO from the Schirmacher to the Humboldt Mountains was proposed.There are eight nunataks between Schirmacher and the Humboldt Mountains projected above the ice sheet. These nunataks are strategically placed because they represent the small (4–10 km2), isolated rock exposures in approximately 5000 km2 of ice-covered area. Baalsrudfjellet is one of these nunataks that is located at the easternmost margin of the proposed EAO corridor and represents a significant outcrop to validate the presence of the EAO between Schirmacher and the Humboldt Mountains. This study brings out a two-stage metamorphic evolution (c. 660–680 Ma and c. 580 Ma) with melt generation associated with the younger event. Geochronological constraints by monazite chemical dating from metapelites confirm and validate the continuation of the EAO in-between the Schirmacher Oasis and the Humboldt Mountains.Supplementary material: Monazite analyses, computed ages and age errors of three grains from the high- and low-melt metapelite are available at https://doi.org/10.6084/m9.figshare.c.3738362

Advances in Antarctic geoscience studies: Indian contributions

“…Sengupta, 1986a;Singh, 1986;Ravikant and Kundu,1998;D'Souza and Chakraborty, 2000;Rao et al, 2000), stretched to Gruber (Kaul et al.,1987), Petermann Ranges (Joshi et al, 1991;Joshi and Pant, 1995), Humboldt (Ravindra et al, 1991), Payer-Weyprecht and Skeids Mountains, (Bejarniya et al, 1995;D'Souza et al, 1995), Orvin-Conrad (Bejarniya et al, 1998), Muhlig-Hofmanfjella (D'Souza et al, 2006), and further to Stabben-Jutulsessen nunataks in Gjelsvkfjell Mountains (Dharwadkar et al, 2017), covering a vast region of Central Dronning Maud land of East Antarctica between 2°E and 15°E longitudes and extending up to the last southern exposures close to the Polar Plateau (Figure 2). Subsequent to the opening of yet another sector in Prydz Bay, the region encompassing Larsemann Hills and adjoining promontories was also covered by detailed structural and metamorphic mapping (Beg and Asthana, 2012;Nath et al, 2016;Roy, et al, 2017).…”

“…and others such as Austree and Midtre lying north of the Petermann ranges. These nunataks have been investigated by Kaul et al (1991), Roy et al (2017) and others, who have described the geology and petrography of the gneisses, basic granulites and quartz-syenite rocks exposed therein.…”

“…The oldest date obtained from monazite within the metapelite of ~584 Ma indicates that the area is part of EAO. Based on lithological, metamorphic, structural, geochronological similarities the EAO has been hypothesised to pass through the nunatak (Roy et al, 2017).…”

Recent Contribution to the Antarctic Gelology

“…The metapelite is represented by the mineral assemblage quartz + biotite + plagioclase + garnet + sillimanite. The peak metamorphism for metapelite is estimated at 635°C at 6-7Kbar assumed pressure (Roy et al, 2015b). Pyroxene granulite is one of the major rock types interbanded with the quartzofeldspathic gneiss.…”