Pillow Lavas in Xenolith in Great Dyke
Pillow lavas in a greenstone xenolith in the upper levels of the Great Dyke
Atlas
View of Nyamaneche Hill, Horseshoe Section
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.
Structural features of Shamvaian Metasediments, Glendale
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.
Deweras Aeolianites
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).
Sinamwenda Meteorite Crater
200m diameter impact crater, in Karoo Sandstones, see attached field guide
View of The Upper and Lower African Surfaces, Mvurwi Section
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.
Ngulube Kimberlite, Mphoengs
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.
Ripple Creek Iron Ore Deposit
The Ripple Creek orebody lies near the base of the western limb of the Lannes Sedimentary Formation and is separated from the underlying lavas of the Ingwenya Formation only by a thin (± 5 metre) bed of felsitic shales and narrow lenticular horizons of dolomitic limestone.
The Ripple Creek iron ore deposit comprises the thickest portion of a long gossanous orebody that strikes northwest – southeast and forms a part of a 35km strike of gossanous rocks.
Hurungwe Gneiss
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
Traverse of Mvurwi Section of the Great Dyke to examine the Upper and Lower African Surfaces
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.
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