M.Sc. (Geology) / The Sishen Iron Ore Mine is situated in the Northern Cape Province at the northern extremity of the Maremane dome. The stratigraphy of the Sishen Iron Ore Mine consist of carbonate rocks of the Campbellrand Subgroup which are unconformably overlain by the Wolhaarkop Breccia. The Wolhaarkop Breccia grades upwards through a shaly unit into an succession of iron formation known as the Manganore Iron Formation. The positive correlation of the Manganore Iron Formation with the Asbesheuwels Subgroup, of which it represents the oxidized equivalent, assigns a collapse origin to the Wolhaarkop Breccia. The siliciclastic Gamagara Formation overlies the Manganore Iron Formation unconformably. The unconformity cuts through the Manganore stratigraphy into the carbonate rocks of the Campbellrand Subgroup. The Gamagara Formation consist of a basal unit of conglomerates and argillite of varying thickness in the form of stacked upward fining alluvial cycles. These are overlain by two well 'developed upward coarsening progradational shale to quartzite deltaic cycles. A massive argillite unit marks the upper contact of the Gamagara Formation with the overlying Makganyene and Ongeluk Formations. This unit represents a milonite along a thrust plane and the Ongeluk lava and parts of the Makganyene diamictite were thrusted over the Gamagara Formation which is a correlative of the Mapedi Formation of the 01ifantshoek Group...

M.Sc. (Geology) / Please refer to full text to view abstract

M.Sc. / Known outcrops of the supracrustal Mesoarchean Mozaan Group of the Pongola Supergroup occur in north-eastern Kwazulu-Natal and southern Mpumalanga in South Africa, and southern Swaziland. Outcrops of the Mozaan succession in Swaziland are preserved in the Ntungulu-Mahlangatsha and Kubuta-Mooihoek areas. The succession is composed of polymictic conglomerate, poorly sorted scour based quartzite, orthoquartzite, shale, iron-formation, polymictic diamictite and lava. In the Kubuta- Mooihoek area a 3000m thick succession is preserved and correlates almost bed for bed with that in the Hartland area in South Africa. The succession is preserved from the Dipka member of the Sinqeni Formation at the base to the Tobolsk lava at the top. The depositional environment ranges essentially between fluvial and marine with two distinct glaciogenic diamictite units and one unit of lava near the top of the succession. Seven unconformity bounded sequences are recognised in the succession and from these a relative sea-level curve could be constructed. Trace element geochemistry of the shale reveals that the source area was predominantly felsic with a mafic component probably derived from the uplifted pre-Pongola granitoids and Nsuze Group. The petrography of the quartzite in the succession suggests a change in provenance from a low-lying deeply weathered to uplifted moderately weathered source area higher up in the stratigraphy. Part of the tectonic uplift may have been associated with isostatic rebound related to melting of continental glaciers. The Tobolsk lava is a continental flood basalt also possibly related to a tectonic uplift event. There are indications of sediment recycling in the upper part of the succession where conglomerates are predominantly composed of chert clasts A pretectonic quartz porphyry sill, folded with the strata, provides an upper age limit of 2837±5 Ma for the deposition of the Mozaan Group. The Mooihoek granite (2824±6 Ma) that intrudes and deforms the synclinal structure along its eastern flank, provides an upper age limit of the folding event. This suggests that the deformation of the Mozaan succession took place in the intervening 13 Ma period between 2824 and 2837 Ma ago.

During 1963 an area was mapped around Sidbury, 23 miles south- west of Grahamstown. The object of the survey was to examine stratigraphic problems, which included the nature of a large occurrence of shale south of Alicedale in a region previously mapped as Witteberg, and the relationship between Silcrete and Calcrete. During the invest igation evidence of the existence of two, possibly three , major thrust-faults and of extensive overfolding to the south was discovered. There is reason to believe, that movement on the Zuurberg Fault was initiated in pre-Cretaceous times, and renewed in the early Cretaceous. The Silcrete is shown to be related to the pattern of presentday drainage. Stone implements found embedded in the Calcrete suggest that it is of Recent age.

M.Sc. (Geology) / Please refer to full text to view abstract

The provenance of the Neoarchaean Ventersdorp Supergroup and several age-related supracrustal successions was analysed to gain insight into the geotectonic evolution of the Kaapvaal Craton during the transition from the Archaean to Proterozoic Eras. The studied successions include, besides the siliciclastic formations of the Ventersdorp Supergroup, the upper Wolkberg and Buffelsfontein Groups, the Godwan Formation and the Schmidtsdrift Subgroup of the basal Transvaal Supergroup in Griqualand West. Petrographic, whole rock geochemical and Sm-Nd isotopic analyses were combined with SHRIMP U-Pb age dating of detrital zircons. Furthermore, Rb-Sr isotopic studies were carried out on carefully selected suites of samples from surface exposure or, wherever possible, on deep diamond drill core. The Ventersdorp Supergroup is an up to 5 km thick undeformed, only slightly metamorphosed volcano-sedimentary succession deposited on the Kaapvaal Craton between 2714 Ma and 2665 Ma. A lack of major time hiati to the underlying Mesoarchaean Witwatersrand Supergroup and covering Neoarchaean to Palaeoproterozoic Transvaal Supergroup render the Ventersdorp Supergroup very well suited for the investigation of the geotectonic evolution of the Kaapvaal Craton near the Archaean-Proterozoic boundary. This is supported by its excellent preservation, which also allowed detailed studies of sedimentological structures, such as seismites indicating Neoarchaean earthquakes. The provenance analyses carried out on the clastic formations of the Ventersdorp Supergroup point to a gradual change in tectonic evolution from typically Archaean to post-Archaean processes rather than a drastic, unique transition in the case of the Kaapvaal Craton. Texturally immature wackes of the Kameeldoorns Formation, representing the oldest clastic units of the Ventersdorp Supergroup, are derived mainly from Mesoarchaean source rocks, whereas the stratigraphically younger Bothaville Formation displays geochemical signatures comparable with Archaean trondhjemite-tonalite granodiorite-suites (TTGs), thus suggesting crustal addition in the so-called ‘Archaean-style’. The extension of provenance analyses to supracrustal successions that are tentatively correlated with the Bothaville Formation, revealed contributions from granitoid V sources that formed under post-Archaean and Archaean conditions. Furthermore, the geochemical data for all analysed formations support a passive margin setting. Arc settings, as indicated in some samples, are due to the input of less fractionated volcanic material that provides evidence of distal volcanism. Analyses of Nd-isotopic systematics and U-Pb ages of detrital zircons revealed a Mesoarchaean age for the source rocks of the formations. U-Pb age dating of detrital zircons of the Godwan Formation suggests that this formation is of Mesoarchaean age, and therefore not a correlative of the other Neoarchaean successions. Hence, the results suggest that the continental crust of the Kaapvaal Craton was thick enough since the Mesoarchaean (2.8 - 3.1 Ga) to allow long-term crustal recycling, and therefore modern plate tectonic processes could have operated earlier than on other well-studied cratonic blocks. During the Neoarchaean, however, crustal thickening of the Kaapvaal Craton took place by accretion of Archaean-style TTGs along the margins of the craton. Thus, Archaean and post-Archaean tectono-magmatic processes co-existed. Furthermore, the Neoarchaean supracrustal successions represent the first sedimentation events on an entirely stabilised and tectonically quiescent Kaapvaal Craton. Input from distal volcanic sources marks the last sign of volcanic activity prior to the craton-wide deposition of carbonate rocks of the Transvaal Supergroup. Geochronological data also imply a connection of the Neoarchaean Kaapvaal Craton to further cratonic blocks that may hold source rocks for the studied formations, as for some small age populations of older detrital zircons (ca. 3.1 - 3.4 Ga), no suitable source area could be identified on the Kaapvaal Craton itself. However, it seems unlikely that the Zimbabwe Craton was one of these cratonic blocks, because the Rb-Sr whole rock ages of all studied formations yield a model age of 2092 ± 55 Ma, which is thought to correspond to a craton-wide influence of the 2.05 Ga old Bushveld Igneous Complex on the Rb-Sr isotope systematics of all analysed clastic successions. This influence is apparently missing in the Southern and Central Marginal Zones of the Limpopo Belt, suggesting that the collision between the Kaapvaal and Zimbabwe Cratons only took place after the emplacement of the Bushveld Igneous Complex, i.e. after 2.05 Ga. / Dr. U. Zimmermann Prof. J. Gutzmer

The project area is situated within the Tugela Valley, located in the Northern Marginal Zone of the Natal Structural and Metamorphic Province, and this work outlines the different styles of gold mineralization found in the Tugela Valley. Two different styles have been recognized and both have economic significance:- 1) Epigenetic shear zone-hosted gold occurs in late-stage relatively undeformed thin quartz veins confined to shear zones, and is present in both the greenschist facies Natal Thrust Belt and the amphibolite facies Natal Nappe Complex. However the vast majority of these occurrences are concentrated within the thrust front (i.e. the Natal Thrust Belt). The gold grades (up to 7 g/t) and the hydrothermal alteration assemblages associated with the epigenetic deposits have been documented. 2) An as yet unrecognized occurrence of syngenetic gold mineralization is found associated with the sediment-hosted exhalative massive, to semi-massive, sulphides of the iThuma prospect, located within the amphibolite facies Natal Nappe Complex. Here gold (up to 3 g/t) is concentrated together with the main sulphide are, as well as some gold enrichment (230ppb) in the hydrothermally altered footwall feeder pipe. It is proposed that the epigenetic mineralization was formed as a consequence of the northward directed abduction of the major thrust slices of the Natal Nappe Complex. This increased the permeability of the rocks and provided channelways for the focussing of fluids. Deposition took place at the thrust front where metamorphic hydrothermal fluids interacted with meteoric water.

The Cape Supergroup (Sequence) comprises three groups, embracing a total of twenty-three formations, with a maximum combined thickness of approximately 8 km. The Table Mountain Group consists of medium-grained (occasionally fine- or coarse-grained), "clean", ultra-quartzose sandstone plus subordinate fine-grained, "dirty", subfeldspathic to feldspathic sandstone, mudrock, and rhythmitite. Average total thickness is about 3000 m. The Bokkeveld Group is composed of mudrock, rhythmitite and subordinate subfeldspathic to feldspathic sandstone (generally fine-grained and "dirty"), with a maximum total thickness of over 3000 m. The Witteberg Group comprises fine- to medium-grained ultra-quartzose sandstone, icaceous streaky rhythmitite, mudrock, and one thin diamictite unit; total thickness is about 1700 m. The strata belonging to the Cape Supergroup appear to have been largely deposited under marine conditions in environments ranging from outer shelf to beach. Deltaic deposits are,however, common in the upper part of the Bokkeveld Group and the Witteberg Group, while the main sandstone units in the upper third of the Table Mountain Group may have accumulated on a coastal alluvial plain. Deposition took place in a basin elongated in an east-west direction, with the palaeoslope inclined towards the south. Palaeocurrents were generally directed down the palaeoslope, but westerly 1 transport directions parallel to the palaeostrike and presumed shoreline are present in both the Table Mountain and Witteberg Groups. I The sedimentary rocks o~ the Karoo Sequence are subdivided into two groups (containing a total of eleven formations) and four ungrouped formations. Using the maximum thicknesses of the individual formations, a combined total thickness of about 12 km can be calculated. The sequence commences with the Dwyka Tillite, a 700-m-thick diamictite unit. The overlying Ecca Group consists of "varved" rhythmitite, dark, massive, fine- to very fine-grained ultra-lithofeldspathic sandstone and subordinate mudrock with a total thickness of 2000 - 3000 m. The Beaufort Group is composed of thick mudstone layers alternating with thinner fine-grained ultra-lithofeldspathic, lithofeldspathic and lithic sandstones, with the exception of the Katberg Formation which consists largely of sandstone. Fining-upward cycles are ubiquitous, while red mudstone is com~on, especially in the upper half of the group. A maximum thickness of about 6000 m was obtained in the East London area. The Molteno Formation Consists of up to 600 m of alternating fine- to coarse-grained sublithic sandstones (frequently pebbly) and grey mudstones, generally forming finingupward cycles. The Elliot Formation (up to 500 m thick) consists of red and grey mUdstones and subordinate fine-grained lithofeldspathic sandstones arranged in fining-upward cycles. The bulk of the Clarens Sandstone consists of very fine-grained massive (occasionally cross-bedded) sandstone, with a maximum thickness of 300 m. The Drakensberg Group, consisting of up to 1200 m of basalt with some pyroclastic intercalations near the base, caps the Karoo sedimentary succession. The deposition of the Dwyka Tillite by glacier action coincided with a major change from the generally shallow marine conditions which characterised the sedimentation of the Cape Supergroup (with the source area located on the craton to the north of the basin) to a deep linear trough receiving clastic sediments from a source area situated south and south-east of the basin. The Ecca Group,the lower half of which is characterised by the presence of "proximal" turbidite sandstones, records the gradual infilling of this basin, with deltaic conditions developing in the upper part of the group in the western half of the study area (i.e. in the Waterford Formation). The overlying strata were virtually all deposited under fluviatile conditions, the chief exceptions being a stratigraphic interval within the lower half of the Beaufort Group which appears to have formed in a large body of water, a~d the aeolian Clarens Sandstone. The fluviatile sediments were all deposite1 by rivers flowin~ towards the north and nort~-west, while the Clarens Sandstone was laid down by winds blowing from the west. The Ecca and Beaufort Group sandstones are characterised by a high rock fragment content with "felsit ic" gra ins being a prc;>minent constituent. This, together with the relative abundance of quartzfeldspar porphyry pebbles in the Katberg Sandstone unit (Beaufort Group) near East London, indicates that volcanic material probably formed a prominent part of the post-Dwyka Karoo provenance.

This dissertation is based largely on data that was accumulated during the execution of an exploration program by Iscor Ltd in the Northern Transvaal. The program included geological mapping, geophysical surveys and drilling, on Precambrian iron-formations in the Central Zone of the Limpopo Belt. The structure, stratigraphy, metamorphism, and economic importance of the magnetite quartzites and associated lithologies of the Moonlight prospect are discussed. The lithologies underlying the Moonlight prospect area consist of various pink- and grey-banded gneisses and pink granulite, together with a variety of metasedimentary supracrustal rock-types and concordant serpentinite bodies. The gneissic rock-types consist of chlorite-quartz-feldspar gneiss, chlorite-quartz-feldspar augen gneiss, hornblende-quartz-feldspar gneiss, biotite-quartz-feldspar gneiss, felsic and mafic granulite, and foliated amphibolite. The metasedimentary lithologies are represented by calc-silicates and marble, white quartz-feldspar granulite, magnetite quartzite, metaquartzite and garnet-bearing granulite and gneiss (metapelites). The concordant ultramafic bodies consist of serpentinite with lesser amphibolite, dunite, and chromitite. Intrusive pegmatites and diabase dykes are also present in the prospect area. Metamorphism reached granulite-facies, and more than one retrqgrade metamorphic event is recognized . Amphibolite-facies assemblages are present, but it is uncertain whether they represent another retrograde event . Polyphase deformation has produced intense and complex folding , resulting in irregular magnetite quartzite orebodies. The high metamorphic grades have resulted in medium- grained recrystallization of the magnetite-quartzites with a loss of prominent banding often associated with these rock-types . The magnetite quartzite occurs as three seperate but related ore zones, consisting of one or more ore-bands seperated by other lithologies. All three zones form poor outcrops and suboutcrops in a generally flat lying and sand covered area. · Although representing a low-grade iron ore (32% total Fe), the magnetite quartzite deposits at Moonlight are regarded as potentially viable due to the large opencast tonnages available at low stripping ratios, and the relatively cheap and easy beneficiation process needed to produce a magnetite concentrate with 69-70% total Fe.

Iron-formations are ferruginous sedimentary rocks which have their source from fumarolic activity associated with submarine volcanism, with deposition of iron as oxides, hydroxides, and hydrous oxide-silicate minerals in shallow and/or deep marine sedimentary systems. The Precambrian ironformations of southern Africa have a wide age range, but are more prominently developed before 1.SGa. These iron formations occur in greenstone belts of the Kaapvaal and Zimbabwean cratons, in the Limpopo mobile belt, in cratonic basins and in the Damara mobile belt. The Archaean-Proterozoic sedimentary basins and greenstone belts host iron ore deposits in iron-formation. Iron formations have a lengthy geological history. Most were subjected to intense, and on occasions repeated, tectonic and metamorphic episodes which also included metasomatic processes at times to produce supergene/hypogene high grade iron ores. Iron-formations may be enriched by diagenetic, and metamorphic processes to produce concentrating-grade ironformations. Uplift, weathering and denudation, have influenced the mineral association and composition of the ores, within which magnetite, haematite and goethite constitute the major ore minerals. The iron resources of the southern Africa region include the Sishen deposits, hosting to about 1200 Mt of high grade direct shipping ore, at >63% Fe. Deposits of Zimbabwe have more than 33 000 Mt of beneficiable iron-formation. The evaluation of an iron ore prospect involves many factors which must be individually assessed in order to arrive at an estimate of the probable profitability of the deposit. Many of these are geological and are inherent in the deposit itself. Other factors are inherent aspects of the environment in which the ore is formed. Although the geological character of the ore does not change, technological advances in the processing techniques may have a great effect on the cost of putting the ore into marketable form. Geochemical, geophysical and remote sensing methods would be used for regional exploration. Chip sampling and drilling are useful for detailed exploration. Purely geological exploration techniques are applicable on a prospect scale in the exploration of iron ore deposits. Regional exploration targeting should choose late Archaean greenstone belts containing oxide facies iron-formation or Early Proterozoic basins located at craton margins as they are both known to host high-grade haematite orebodies formed by supergene/hypogene enrichment. Most types of iron ore deposits in southern Africa are described and classified. An attempt is made to emphasize the major controls on mineralisation, in the hope that these may be applicable to exploration both in the southern African region and within analogous settings around the world.