Submitted by Andrew du Toit on Mon, 15/08/2016 - 10:58 | Last updated: Tue, 23/08/2016 - 13:21
Grid Ref (WGS84 Lat/Long in decimal degrees)
Turn north off Mazowe to Mutoroshanga Road and drive up to the transmission masts above Mutoroshanga
Great Dyke Erosion Surfaces
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. Remnants of this heavily dissected plateau can be recognised to the north and south in the form of (1) a broad, mesa-like upland, (2) discontinuous, eroded, cliff-like features made up of horizontally-fractured serpentinite, and (3) remnants of the overlying sheeted silica vein zone.
2. To the south is the resistant massif of the Pyroxenite Succession including Mvukwe hill (almost 150m higher than the Upper African Surface).
3. Note particularly the significantly higher elevation (ca. 350m) of the surrounding granite terrain (of the Post-African Surface) to the east than to the west and the eccentric disposition of the Upper African Surface relics mainly on the east side of the Great Dyke with Post-African valleys on the west side.
4. Directly to the north is the old Mutorashanga chromite mining area where high-grade chromite was extensively mined in narrow chromitite seams for many decades up to the 1980s. Also to be seen are signs of eluvial chromite mining and associated slimes dams on the flat, Post-African valley floors on the west side; these serpentinite soils contain ca. 1% Ni.
5. Dunites in this part of the Great Dyke are completely serpentinised at surface (i.e., without relict olivine) and to depths of up to 300m below the Post-African Surface.
1) Zimbabwe Geological Survey Bulletin 90 - The Erosion Surfaces of Zimbabwe, L.A Lister 1987. 2) Landscape Evolution, Regolith Formation and Nickel Laterite Develoment in the Northern part of the Great Dyke, Zimbabwe, M.D. Prendergast. South African Journal of Geology, v. 116, i. 2, p. 219-240, December 2013