Narrow, fine-grained pyroclastic layers show graded bedding and flame structures.
These give way to a thick sequence of agglomerates with the dominant clasts having a similar composition to the matrix. In thin section the clasts consist of albite phenocrysts set in a dirty saussuritic groundmass containing feldspar microlites and minute quartz grains. The clast margins are very fine-grained and almost opaque except for random feldspar microlites.
Palaeoproterozoic (ca. 2.03 Ga) granitoids (biotite granodiorite), with numerous biotite-rich schlieren, representing an Andean-type continental magmatic arc on the western edge of the Zimbabwe Craton (Master et al., 2013a,b).
The banded gneisses comprise alternating layers of an inequigranular intergrowth of quartz-plagioclase with minor untwinned microcline and accessory apatite, zircon and epidote, with a melanosome of finer grained biotite, partly altered to chlorite. The plagioclase is albite or oligoclase, showing mild sericitisation. The bands have a range of widths up to 200mm and show evidence of extreme ductility during several periods of deformation. The banding trends north-south and dips are steep.
Exposures of isoclinally folded Inyantue Formation paragneisses in the Inyantue River, near Elbas Pb Mine. The gneisses were interpreted as metamorphosed argillaceous sediments and greywackes Lockett, 1979a,b). These gneisses are also invaded by tourmaline-bearing muscovite pegmatites. Alongside the dirt track on the far side of the Inyantue River, there are prospecting pits dug for argentiferous galena, which was mined at the Elbas Mine some 2 km away.
The dominant feature of the view is the distant peak of the uppermost ironstone of the Bend Formation known as Mberengwa. The smaller “false” peak to west is one of the lower ironstones which cap the ultramafic to mafic lava sequence constituting the Bend Formation. The Peak marks the axis of a steeply plunging, NE trending syncline which affects all formations up to the lower parts of the Zeederbergs.
Above the Bend Formation is a locally developed conglomerate and agglomerate of the Koodoovale Formation, which is unconformably succeeded by the upper greenstones.
A road-side stop between Mvurwi and Guruve to view the ridge of Chikonyora hill from the west side.
Note the following:
1. This stop shows, in the distance, the (several tens of metres) thick, wooded silica cap of the Upper African Surface on the ca. 3km-long Chikonyora ridge with intermittently exposed cliffs of horizontally-fractured serpentinite at a lower elevation. The ridge is terminated at its northern end by the north northeast-trending, dextral Gurungwe fault.
Field Guide:-
Stromatolitic dolomites
Pillow lavas in a greenstone xenolith in the upper levels of the Great Dyke
