Summary

At the S margin and at the base of the Naukluft Nappes of the late Proterozoic-early Palaeozoic Damara Orogen in Namibia so-called ‘Unconformity Dolomites’ are developed along thrust planes of nappes and within imbricate structures. Micro-probe analyses, phase-petrological relationships of the unusual mineral composition of the ‘Dolomite’, the salinity and composition of fluid inclusions as well as other geochemical data prove a saline origin of the ‘Unconformity Dolomite’. These data combined with observations on the relationship of deformation and mineral growth, calculated geothermal gradients and radiometric datings lead to the conception that the ‘Unconformity Dolomite’ is a hot saline intrusion which has already intruded a preexisting nappe pile. After intrusion and rapid crystallization, the rocks directly below the rigid dolomite plate acted as a thrust plane for last nappe movements which brought the Naukluft Nappes into their present position.