0000000000429915
AUTHOR
Paul H.g.m. Dirks
The Chirwa dome: granite emplacement during late Archaean thrusting along the northeastern margin of the Zimbabwe craton
The Chirwa dome in northeast Zimbabwe is situated at the boundary between the Zimbabwe craton and Archaean gneisses of the Zambezi mobile belt. This circular granite intrusion has long been regarded as Archaean granite which was remobilized during Pan-African times and emplaced as a mantled gneiss dome into a Proterozoic metasedimentary sequence. Field mapping, structural work and new zircon dates indicate that the Chirwa dome and surrounding rocks underwent a very different history. The supracrustal sequence was deposited and moderately deformed between ~2613 and ~2601 Ma ago, as bracketed by a provenance date and an intrusive date, respectively. Shortly after deposition, the sequence was …
Late Archaean foreland basin deposits, Belingwe greenstone belt, Zimbabwe
Abstract The c. 2.65 Ga old sedimentary Cheshire Formation of the Belingwe greenstone belt (BDB), central Zimbabwe, has been studied in detail for the first time to shed some light on the much debated evolution of this classical belt. The Cheshire Formation rests sharply on a mafic volcanic unit (Zeederbergs Formation) and comprises a basal, eastward-sloping carbonate ramp sequence built of shallowing-upward, metre-scale sedimentary cycles. The cycles strongly resemble Proterozoic and Phanerozoic carbonate cycles and might have formed by small-scale eustatic sea level changes. The top of the carbonate ramp is represented by a karst surface. The carbonates are overlain by and grade laterally…
Exhumation of high-pressure granulites and the role of lower crustal advection in the North China Craton near Datong
Granulites in the Datong-Huai'an area of North China are characterized by high P-T assemblages (14 16 kbar, -9OOY) that underwent decompression cooling to -7 kbar and -800°C during a 250&2400 Ma tectonic event. Nearly all structures in the grantilites developed during the retrograde exhumation history, and can be subdivided into: (1) the stratigraphically lower, 'lower structural domain' that is characterized by complex folding with 55-10 km wide domes surrounded by concentric troughs, preserving concentric lineation patterns; and (2) the stratigraphically higher 'upper structural domain' that is characterized by a planar gneissic foliation, upright folds and a constant, shallowly SW-plungi…
Structural relations and PbPb zircon ages for the Makuti gneisses: evidence for a crustal-scale Pan-African shear zone in the Zambezi Belt, northwest Zimbabwe
Abstract The Makuti Group of northwest Zimbabwe is composed of mafic and intermediate biotite-rich gneisses interlayered with quartzofeldspathic gneisses of granitic composition, and minor sedimentary units. The gneisses have experienced a multi-staged metamorphic history, including an early high temperature-high pressure event and subsequent reworking at upper- to mid-amphibolite-facies conditions. They are positioned along the strongly deformed, southern margin of the east-west trending Zambezi Belt, and have been correlated with supracrustal gneiss units along the northern margin of the Zimbabwe Craton. The Makuti Group is characterised by an intensely developed gneissic layering and com…