The outcrop shows a pavement of pillow lavas with spherulites, some patches of pillow breccia and a tuff band. The pillows are generally about 1-2m in cross-section and some 3-D exposures suggest lengths of 3-4m. The spherulites tend to be concentrically arranged, with some flow units consisting almost wholly of coalesced spherulites. In some pillows the spherulites appear to be located around cooling cracks.
Outcrop of Matuki Marble in the roadside cutting on the Zambezi escarpment
These are variegated inhomogeneous, polydeformed migmatitic gneisses, with leucocratic quartzo-feldspathic leucosomes and biotitic melanosomes. These migmatitic gneisses are the westernmost dated Archaean rocks of the Zimbabwe Craton. They have zircons which an age of ca. 2.71 Ga (Master et al., 2013a,b)- and they appear to be the source of the 2.7 Ga detrital zircons in the Malaputese Formation meta-arkoses (pink paragneisses), as well as the source of inherited zircons in the Palaeoproterozoic granites intruding the western Magondi Belt.
An outcrop interpreted as a volcanic vent is exposed in the bed of the Mtshingwe River. The outline of the “megabreccia” approximates to the river bed and finer-grained sulphidic tuffs occur along the regional strike to the north and south. However, detailed mapping has not been done. The clasts in the breccia of finer-grained, grey tuffaceous rocks (not unlike the surrounding tuffs) and larger fragments of tonalite which are lithologically and isotopically very similar to the Chingezi tonalite which intrudes the Hokonui Formation to the east.
At the sign that marks 40 km to Gwayi River, there is a roadcut exposure of isoclinally folded amphibolite and biotite schists which was mapped by Lockett (1979a), who regarded it as a tightly infolded remnant of the Malaputese supracrustal sequence, surrounded by basement granitoid gneisses. It may possibly be a large raft or xenolith, or even a roof pendant, of the Palaeoproterozoic post-Magondi biotite granodiorites that are found close by (Stop 8), containing numerous biotite-rich schlieren.
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.