Pillow lavas in a greenstone xenolith in the upper levels of the Great Dyke
A road-side stop between Mvurwi and Guruve to view Nyamaneche hill from the west side.
Note the following:
1. This stop shows, in the distance, Nyamaneche hill at the southern end of the Horseshoe section which is offset from the Mpinge section by the Gurungwe fault.
2. Nyamaneche hill is a rounded serpentinite massif with intermittently exposed cliffs at elevations of ca. 1640m beneath a tree-less silica cap of the Upper African Surface.
Where the main road crosses the Mazowe River, There is an excellent exposure of Shamviain metasediments (1a - S17.481002, E30.985577) The rocks, mainly a metagreywacke, show well developed foliations. Deformation increases in a northerly direction, to the sheared contact with the Glendale Pluton (not exposed) (1b - S17.480267, E 30.984390). It is a favourite site for teaching students to take basic structural measurments.
Large-scale planar crossbedded arkosic sandstones of the Deweras Group display small-scale features that are diagnostic of aeolianites, including em-scale inversely-graded ripple-cross-laminated "subcritically-climbing translatent strata" (Hunter, 1976), wedge-shaped massive grainflows (avalanche deposits), and pinstripe lamination. These are among the oldest authenticated aeolianites in the world (Master, 1995).
200m diameter impact crater, in Karoo Sandstones, see attached field guide
A road-side stop between Mvurwi and Guruve to view the topography of the Mvurwi section from the south side.
Note the following:
1. On the left is the markedly planar Lower African Surface dominated by a dissected mesa terrain at a cliff-top elevation of ca. 1525m.
The Ngulube kimberlite was discovered in 1998 by aeromagnetic survey by Debeers Zimbabwe. It is intruded into the Zimbabwean Archean craton a few kilometres from the Botswana border. Surface exposure of the kimberlite is poor, however, the central parts are presently exposed by trenching and shafts. Its mineralogy is typical of Group I kimberlites including abundant macrocrysts of olivine, picroilmenite, Cr-diopside, pyrope garnet; phenocrysts of olivine and microphenocrysts of spinel. Notably phlogopite is present though not abundant.
The Hurungwe Gneiss,ZMB13/8B, collected on the Karoi-Chirundu road is a biotite garnet granitic gneiss, containing quartz, K-feldspar, plagioclase, biotite, garnet. Biotite schlieren 2-4 mm wide help to define a gneissic foliation in the rock. The zircons have yielded ages of 2020.7 ± 6.6 Ma, which is regarded as the age of the intrusion (Master et al., 2015). No inherited zircons were found in this sample.
Stop 1 on attached field guide
A full-day, circular traverse of part of the Mvurwi section, principally to examine the heavily-eroded Upper African Surface towards the east and the better-preserved mesa terrain of the Lower African Surface towards the west. The route is ca. 6-7km long with a moderate ascent of ca. 300m at the start.