Recent post-750 Ma continental reconstructions constrain models for East African Orogeny formation and
also the scattered remnants of ~640 Ma granulites, whose genesis is controversial. One such Neoproterozoic granulite
belt is the Schirmacher Oasis in East Antarctica, isolated from the distinctly younger Pan-African orogen to the south in
the central Droning Maud Land. To ascertain the duration of granulite-facies events in these remnants, garnet Sm-Nd
and monazite and titanite U-Pb IDTIMS geochronology was carried out on a range of metamorphic rocks. Garnet
formation ages from a websterite enclave and gabbro were 660±48 Ma and 587±9 Ma respectively, and those from Stype granites were 598±4 Ma and 577±4 Ma. Monazites from metapelite and metaquartzite yielded lower intercept UPb ages of 629±3 Ma and 639±5 Ma, respectively. U-Pb titanite age from calcsilicate gneiss was 580±5 Ma. These
indicate peak metamorphism to have occurred between 640 and 630 Ma, followed by near isobaric cooling to ~580 Ma.
Though an origin as an exotic terrane from the East African Orogen cannot be discounted, from the present data there is
a greater likelihood that Mesoproterozoic microplate collision between Maud orogen and a northerly Lurio-Nampula
block resulted in formation of these granulite belt(s).
Additional Publication Details
USGS Numbered Series
Sm-Nd and U-Pb isotopic constraints for crustal evolution during Late Neoproterozic from rocks of the Schirmacher Oasis, East Antarctica: geodynamic development coeval with the East African Orogeny