Geology of the Kottas terrane, Heimefrontfjella (East Antarctica)

The Kottas Terrane is the northernmost crustal block in the Heimefrontfjella.
It is composed of juvenile Mesoproterozoic igneous rocks of calcalkaline
composition and minor sedimentary rocks, which underwent
amphibolite-facies metamorphism in late Mesoproterozoic times (Grenvillianage
orogeny). Whereas central Heimefrontfjella was strongly affected by the
East-African – Antarctic Orogeny in Late Neoproterzoic to Cambrian times,
the Kottas Terrane shows only a weak overprint at brittle/ductile transition
conditions, mostly manifested as northward-directed thrusts. The boundary
between the Kottas and Sivorg terranes of central Heimefrontfjella is marked
by the prominent Heimefront Shear Zone, which is exposed in two small
nunataks immediately south of the main massif of Kottasberge.