The term Ntshuku Complex was introduced by van der Leeden (1994) in the Hutte Sauvage Lake area following fieldwork in the summer of 1983 (van der Leeden, 1984). The Ntshuku Complex was extended southward by Girard (1990a). A detailed petrochemical and geochemical study of the Ntshuku Complex was conducted as part of a bachelor’s thesis (Germain, 2017).

This unit is named after Ntshuku Ministuku Lake located in sheet 24A02.

The Ntshuku Complex consists of three units: 1) metavolcaniclastics, schist and augen gneiss, and quartz-feldspar porphyry, 2) amphibolite, and 3) marble and calcosilicate rocks. These three units are interstratified between each other on a scale ranging from centimetres to kilometres. Deformation within these units is variable; transition between foliated and mylonitic lithologies occurs gradually over a few decimetres to several metres. Description of units is largely taken from van der Leeden (1994) and Girard (1990a, b).

Unit pPnts1 corresponds to units C2a and C2b of van der Leeden (1994, 1995) and C-2 of Girard (1990a). The degree of deformation is usually very high, but there are centimetric to hectometric undeformed klippes where primary structures can still be discerned (Girard, 1990a). Regular and rhythmic bedding when not deformed becomes contorted and corrugated with increased deformation. In addition, deformation results in decreased crystal size and abundance, leaving room for mylonitic recrystallization in the form of veinlets. This unit is also characterized by alternating metric to decametric metavolcaniclastic and amphibolite layers. Meta-arkoses and a few chert beds are reported locally (Girard, 1990a).

Metavolcaniclastics are characterized by the presence of 5 to 60% eyes (crystals) or 1 to 40 mm white lithic fragments (lapillis) in a very fine to medium-grained greyish or cream-coloured matrix. Fragments larger than 64 mm are sparse. Rounded to subangular crystals are commonly deformed and stretched. Edges are commonly corroded and cut by metamorphic minerals of the matrix. They are mainly composed of plagioclase (andesine) associated with lower amounts of orthose, microcline and quartz. Centimetric bedding in metatuffs is marked by changes in crystal size and content. Lithic fragments are composed, in order of importance, of the perthitic orthose-plagioclase and plagioclase-quartz assemblages. There are also some fragments of dioritic composition. Since the matrix is fine grained, van der Leeden (1994) did not consider fragments to be of metamorphic origin. The protolith could be lapilli tuff, tuffaceous sandstone or polymictic pebble conglomeratic sandstone. The majority of metavolcaniclastics are dacitic, locally rhyodacitic or andesitic. They contain 4 to 25% ferromagnesian minerals, mainly brown or green biotite, and locally hornblende and garnet. Biotite defines foliation and is concentrated in laminae or in certain bands or beds. Secondary foliation, oriented 30° to 45° of the main foliation, and banding are usually observed. Hornblende locally forms small poikiloblasts stretched in foliation. Accessory minerals are abundant and include zoisite, muscovite, chlorite, allanite, sphene, opaque minerals and zircon. They usually form millimetric crystals concentrated in laminae. Plagioclase is commonly sericitized.

In places, metavolcaniclastics do not contain crystals. They are essentially quartzofeldspathic, hololeucocratic and light cream grey. Girard (1990a) also mentions the presence of phyllitic and graphitic beds in gradual contact with crystal metatuffs over a few decimetres. These phyllitic beds are friable, grey, brown or pinkish in fresh exposure. A rusty alteration patina is common. The rock consists of millimetric quartzitic or quartzofeldspathic microlithons alternating with phyllosilicate microlithons. The phyllitic fraction is mainly composed of muscovite-biotite associated with chlorite in minor amounts. Epidote and garnet are occasional. White mica alteration is commonly superimposed on this assemblage. Deformation is marked by banding recrystallization, a very well-developed schistosity and the presence of several generations of cleavages and crenulations. The protolith is thought to be primarily a volcaniclastic rock rich in ash and pelitic material. Graphitic beds are an extremely friable facies of mealy white rock having a rusty patina. They were observed near mineralized zones at the interface between amphibolites and crystal metatuffs. These rocks are composed of quartz bands, saussuritized residual feldspar, and micas (sericite, muscovite and fuschite).

Schists and augen gneiss are of pelitic or semi-pelitic composition. These fine-grained rocks are grey or light brown. Feldspar, quartz and lithic fragment eyes are 1 mm to 15 mm long, most forming diamonds 1 mm to 3 mm long. Van der Leeden (1994) interpreted a volcanic or detritic origin for these fragments based on the following arguments: 1) schists and gneiss are locally interstratified with metabasalt; and 2) eyes do not have the characteristics of metamorphic remobilization or boudinage. Beds are generally thin and laminations are locally observed. To the north of Ntshuku Ministuku Lake, a muscovite schist bed ~3 m thick contains numerous felsic lithic blocks reaching 15 cm long.

Finally, decimetric to metric layers of porphyritic (QFP) quartz monzodiorite are interstratified in other facies of unit pPnts1. The matrix is granoblastic, fine to very fine grained and grey. The rock contains 10 to 20% plagioclase phenocrystals (locally quartz and microcline) 0.5-1 cm long that form porphyroclasts in places. It contains ~25% ferromagnesian minerals (brown biotite and hornblende) with a preferential orientation defining foliation. Hornblende is present in the matrix, but also in poikilitic phenocrystals containing numerous inclusions of quartz, feldspar, sphene, biotite and zircon. Biotite forms small scattered flakes. Quartz monzodiorite consistently contains large allanite grains rimmed by epidote and sphene. Other accessory minerals are garnet, apatite and opaque minerals.