The Cambrian Magmatic Evolution in the Damara Belt, Namibia: Constraints from Garnet-Bearing Granites

Abstract

Garnet is a petrogenetic key indicator, common in igneous and medium- to high-pressure metamorphic rocks. It provides valuable constraints for pressure–temperature–time paths in orogenic belts and offers insight into magma generation, evolution, and crystallization. To investigate the timing and petrogenesis of biotite- and garnet-bearing granites and granodiorites from the Southern Central Zone (SCZ) of the Damara Orogen, Namibia, we integrate U–Pb geochronology, whole-rock geochemistry, mineral chemistry, and zircon Hf isotope analysis. Zircon and monazite U–Pb dating yielded 528–521 Ma, linking the crystallization of the biotite- and garnet-bearing granites to the peak metamorphic stages of the Damara Orogeny. Pronounced enrichment in light and depletion in heavy rare earth elements characterize the garnet-bearing granites. Combined with whole-rock geochemical data and negative zircon Hf values, these features identify the partial melting of ancient felsic gneisses within the Abbabis basement—as the origin of the parent magma of these granites. Major element characteristics suggest that garnet most likely formed before the granite crystallized, during the partial melting of the Abbabis basement. Thermobarometry yields 568–726°C and 3.8–5.0 kbar for the crystallization of these granites. The various garnet morphologies are interpreted to record locally variable pressure–temperature conditions during migmatization of the basement gneisses, documenting the complexity of midcrustal anatexis in the Husab region during the collision of the Kalahari and Congo cratons.