Shabani Gneiss - Runde River
Grid Ref (WGS84 Lat/Long in decimal degrees)
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.