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.
There are 14 footprints of a large bipedal dinosaur in the dry bed of the Ntumbe (locally Mufuraninga) River in the Chewore Safari Area (Tim Broderick, 1985). A small trackway is 218cm long and consists of ten footprints set close to the midline. The average pace length is 24.6cm and average stride length 45.8cm. Height at hip is calculated at 22.5cm. The speed of the dinosaur was calculated at walking pace of ~1.98km/hour. A second theropod trackway (203cm long), the tracks are 7cm long and pace and stride lengths 39cm and 80cm, respectively.
Orpheus Mine lies in the Iron-formation of the western limb of the Redcliff Jaspilite Formation. The ore is a hard, dense, grey haematite enclosed by, and derived from, a finely banded grey and red Iron-formation. It is believed that the ore is of hypogene origin although supergene processes have not been ruled out. The ore has formed by the leaching of silica-rich bands and possible infilling of iron. Faulting of the Iron-formation and associated clastic sediments has taken place and separates the orebody from the nearby Beacon Tor deposit.
Within the Makuti Group there are garnet-clinopyroxene-hornblende gneisses (amphibolites) that contain lenses of eclogite having igneous (corona-textured) and metamorphic (garnet-omphacite) textural associations (Broderick, 1980, 1982; Dirks and Sithole, 1999). Dirks and Sithole (1999) found peak P-T conditions of metamorphism for the eclogites of c. 19 kb, 760 ± 25°C. The surrounding amphibolitic gneisses were metamorphosed under P-T conditions of 11 ± 1.5 kb, 730 ± 50°C.
3.6km past the Gweru river bridge, coming from Kwekwe, look out for large boulders of agglomerate rocks on both sides of the tarred road.
Together with amygdaloidal and porphyritic andesitic lavas, phyllites and cherts, these agglomerates form the Maliyami Formation of the Bulawayan Supergroup which in the Gweru-Vungu Valleys area represents the larger portion of the greenstone belt.
The dinosaur Massospondylusis abundant in the Mpandi Formation. It is imbedded in calcareous fine-grained sandstone. Animal fossils are only found in the Mpandi formation in this area. The picture shows the hind-end of the dinosaur. The dinasour is thought to have been carnivorous and capable of running fast on its two large hind legs. The fore limbs were relatively short and the hands had a grasping thumb and three fingers
Our understanding of the geology of Victoria Falls and surroundings is underpinned by the meticulous studies and exceptional field observational skills of a remarkable group of geologists. Initial geological field investigations were carried out by AJC Molyneux and GW Lamplugh in the early 1900’s. HB Maufe (in 1938) made exceptionally detailed descriptions and prescient interpretations of the Kalahari beds exposed in railway cuttings just south of Victoria Falls Station. Seventy-five years later, these are arguably still the best available records of these enigmatic sediments.