Metamorphic imprint of accretion and ridge subduction in the Pan‐African Damara Belt, Namibia

摘要: Ridge subduction is an inescapable plate tectonic process, but has only been documented in modern circum-Pacific environments and not yet recognized from suture zones associated with supercontinent assembly, likely because its imprint obliterated by later collision. The formation of the Pan-African Damara Belt central Namibia involved northward Khomas Sea underneath Congo Craton, prior to final suturing Kalahari Cratons. accretionary history preserved Southern Marginal Zones, which consist turbiditic metasedimentary intercalcated mafic rocks MORB affinity. Two localities Kuiseb Gaub canyons reveal that aluminous metapelites contain a fabric-defining assemblage fine-grained muscovite, chlorite, biotite, quartz graphite overprinted randomly oriented porphyroblasts poikiloblasts garnet, staurolite, kyanite biotite. Associated metamafic hornblende, epidote, rutile quartz, actinolite cores amphibole porphyroblasts. Metamorphic conditions for are estimated at ∼10 kbar 540–560 inline imageC, whereas peak metamorphism occurred 10–10.5 600 imageC. Consequently, these preserve two-stage prograde metamorphic history, where initial burial was followed relatively rapid, near-isobaric heating without attendant deformation conditions. We propose through underplating prism, before ridge opening slab window heated exceptional preservation tectono-thermal orogenic stage due soft, largely aborted collision characterized orogeny, can be attributed confined extent Sea.