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.