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Shabani Gneiss - Runde River

Grid Ref (WGS84 Lat/Long in decimal degrees)

-20.236396, 30.147367
Location: 
North on the Grand View Road which leaves the Zvishavane-Mashava Road some 2.5km east of the Runde Bridge to the old strip road and then 300m west to the old bridge. Best exposures are north of the bridge and extend to the Morton Hall weir.
Stratigraphy: 
Shabani Gneiss
Description: 

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. Pegmatites and felsic dykes of various ages are common, lying along the foliation or transgressing it.

 

The Shabani gneiss is exposed over a north-south trending area and has equivalents in the Mashava area to the east. At Mashava, greenstone remnants are more common and these are presumed to be infolded relics of the 3.5 Ga Sebakwian supracrustal event.

 

Age determinations on these rocks from the Zvishavane area are given in Table 2 of the overview on the CD.  The gneiss includes a wide variety of lithologies from the meso-scale banded types seen in the Runde River to mega banding on a 10-20m scale in underground development at Shabanie Mine and more homogeneous foliated leucotonalite beneath the Manjeri Type Section.

Further Reading: 
Chauvel, C., Dupré, B., Todt, W., Arndt, N.T. and Hofmann, A.W. (1983) Pd and Nd isotopic correlation in Archaean and Proterozoic greenstone belts. Eos (American Geophysical Union Transactions), 64, 330. Hall, R. (1983) B.Sc. Dissertation Project, University of Zimbabwe. Martin, A. (1978) The geology of the Belingwe-Shabani schist belt, Geological Survey of Rhodesia, Bulletin, 83. Nisbet, E.G., Bickle, M.J. and Martin, A. (1977) The mafic and ultramafic lavas of the Belingwe greenstone belt, Rhodesia, Journal of Petrology, 18, 521-66. Orpen, J.L., Bickle, M.J., Nisbet, E.G. and Martin, A. (1985) Belingwe Peak (1:100,000), Geological Survey of Zimbabwe. Scholey, S.P. (1989) M.Phil., Ph.D. Transfer Report, University of Southampton, U.K.
Author Credit: 
Tony Martin
Contributed: 
06/11/2014
Updated: 
06/11/2014