The Trompsburg Complex Revisited

The Trompsburg Complex is a roughly circular intrusion, with a diameter of almost 50 km, that forms a suboutcrop at a depth of approximately 450m near the town of Trompsburg in the Free State Province. Granitic rocks are present near the centre of the intrusion, but the greater part of the Complex consists of layered basic igneous rocks ranging from magnetites to gabbros, anorthosites and basic pegmatoids. The Complex was intruded into dolomites of probable Transvaal age and is unconformably overlain by Karoo sediments (Ortlepp, 1959).