The Sinclair Sequence in southern Namibia comprises largely undeformed and unmetamorphosed volcano-sedimentary successions which have been extensively invaded by high-level intrusions, including dyke swarms, of mafic to felsic character. The westernmost outcrops of the Sinclair Sequence form part of the Awasib Mountain terrain (AMT) and have undergone significant deformation and greenschist facies metamorphism. More intensely deformed and metamorphosed lithologies which underlie the Sinclair Sequence in the AMT are correlated with the Namaqualand Metamorphic Complex (NMC). This “basement” constitutes the initial stage of a continual crustal evolution from the Meso- to Neoproterozoic culminating in the development of the regionally extensive Sinclair Sequence. The development of the Sinclair Sequence took place in three major cycles, the AMT being accommodated lithostratigraphically within the second cycle but chronostratigraphically within the third cycle. Magmatism in the Sinclair Sequence was initiated at least as early as 1.2 Ga and is related to the initiation of subduction in response to continental collision between ∼ 1.3 and 1.2 Ga in an event which is widely represented by deformation and granitoid emplacement in the NMC. The oblique component and low angle of subduction resulted in both compressional (“ice-floe”) and tensional (pull-apart) tectonics, enabling preservation of high-level volcano-sedimentary successions in fault-bounded basins. Alternation of compression and tension enabled calc-alkaline mafic and felsic magmatism in the arc, while bimodal tholeiitic volcanism took place in a developing back-arc basin. Transcurrent movements resulted in slicing up and removal of part of the volcanic arc and accretionary complex.