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Hokonui Formation Volcanic Vent

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.

 

Nickel laterite -View of Mvukwe Hill

A road-side stop on the Mazowe – Mutorashanga road to view the topography of the Great Dyke from the east side in the vicinity of Mvukwe hill. 
Note the following:
1. This stop is on the Miocene Post-African erosion surface, here a mature granitic plain and inselberg landscape on the east side of the Great Dyke.
2. To the west is Mvukwe hill (1752m) on the P5 and P6 Pyroxenites of the Pyroxenite Succession.

Isoclinally infolded remnant of amphibolite schists, intruded by unmetamorphosed Kamativi Dyke Swarm dolerite dyke

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.

Hokonui Formation Agglomerates

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.

 

Mutorashanga viewpoint

This stop in the axis of the Great Dyke provides panoramic views of the serpentinite terrain to the north and south and of the surrounding granite plain and inselberg landscape.
Note the following:
1. The viewpoint is situated on the Upper African Surface at a cliff-top elevation of ca. 1620m.

Shabani Gneiss - Runde River

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.

Mpinge section – Exposures of the Upper African Surface, Chikonyora hill

At this stop (in the axis of the Great Dyke towards the northern end of the Mpinge section) can be seen the principal regolith stratigraphy of the Upper African Surface exposed around and above old chromite workings on the southern slopes of Chikonyora hill (1729m). 
 
On the way, after the turn-off from the Mvurwi - Guruve tarred road, and to the right of the dirt road, look out for soil-mining areas and the mill and slimes dam of the old Mpinge eluvial chromite operation (1970s); also a good example of a butte (isolated hill with steep sides and a flat top similar to

Inyantue Formation paragneisses, and Pb claims near Elbas Mine

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.

Mtshingwe Dyke View

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.

 

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