Abstract
Petrochronology with garnet and monazite was performed on refurbished metapelite samples from the Central Kaoko Zone (CKZ), the Western Kaoko Zone (WKZ) and the Orogenic Core Zone (OCZ). P-T path segments of garnet crystallisation were reconstructed by geothermobarometry based on continuous cation exchange and net transfer reactions. The oldest metamorphic monazite populations of 1490 ± 15 Ma and 635 ± 7 Ma occur enclosed in garnet porphyroblasts and signal Meso-Proterozoic and early Pan-African high-grade metamorphic events. According to the sample position next to a ~ 550 Ma granitoid gneiss, a monazite population at 552 ± 4 Ma may be assigned to a local contact metamorphism. In the WKZ and OCZ the further monazite age isochrones range from 546 ± 12 Ma to 532 ± 5 Ma, and in the CKZ from 528 ± 4 Ma to 502 ± 5 Ma. When interpreted in terms of metamorphic P-T paths and the stability field of monazite, the formation of these late Pan-African monazites are pre-, syn-, and postcrystalline to late Pan-African garnet blastesis. P-T conditions for Mg-rich garnet rims increase from E to W within the CKZ from 550 to 650 °C at 9 kbar. Maximal P-T conditions in the OCZ were 705 °C/7.9 kbar. Garnets in the WKZ display retrograde zonation trends with Mg-rich cores crystallising at 700 °C/4–6 kbar. In the westernmost WKZ sample the garnet core crystallised at 780 °C/7.4 kbar and could be of early Pan-African age. Monazite ages and geothermobarometry confirm results from isotope age dating methods.