Major and trace element data for Damara granitoids distinguish three geochemically distinct granitoid groups, - crustal-melt granitoids, calc-alkaline granitoids and within-plate granitoids. The overwhelming majority of the Oamara granitoids are peraluminous crustal-melt leucogranites which have elevated ⁸⁷Sr/⁸⁶Sr ratios (> 0.710) and old model Nd ages (~ 2.0 Ga). Calc-alkaline diorites are metaluminous and have the lowest ⁸⁷Sr/⁸⁶Sr ratios (0.704 - 0.707) and model Nd ages (OM) in the range 1.1 -1.7 Ga. Within-plate granitoids are characterised by elevated high-field strength (HFS) abundances and have model Nd ages (OM) in the range 1.1 - 1.6 Ga. All Damara granitoids have model Nd ages (OM) older than about 1.0 Ga suggesting that intracrustal reworking was the dominant process and crustal growth was negligible. Damara granitoids define a hyperbola on an ∈ Sr vs. ∈ Nd diagram but cannot be modelled as simple binary mixtures between old continental crust and depleted mantle end-members. An episodic intracrustal remobilisation model is proposed to explain the hyperbola defined by granitoid data on an ∈ Sr vs. ∈ Nd diagram. Within the 10 km thick Damara metasedimentary pile ⁸⁷Sr/⁸⁶Sr ratios increase systematically with depth. This trend is accompanied by a decrease in ¹⁴³Nd/¹⁴⁴Nd ratios. Model Nd ages (CHUR) for the stratigraphically oldest Damara metasediments (Nosib Group) are about 2.0 Ga whereas the younger metasediments (Kuiseb Formation and Nama Group) have model Nd ages (CHUR) about 1.0 Ga reflecting sediment input from younger source terrains. The ratio of model ages (T^Nd_CHUR/T^Sr_BE) is used as an index of intracrustal reworking since it provides a measure of Rb/Sr fractionation (increases) relative to SmlNd fractionation. The older Damara metasediments (Nosib Group) have the highest model age ratios suggesting that their source terrains have suffered the largest amount of intracrustal reworking. However, the rate of intracrustal reworking was greatest in source terrains sampled by the younger Damara metasediments (Kuiseb Formation and Nama Group). This suggests that the rate of intracrustal reworking increased through time in the interval (2.0 - 1.0 Ga) in this segment of continental crust.

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The Central Zone (CZ) of the Damara belt in central Namibia is underlain by voluminous Pan-African granites and is host to numerous pegmatite occurrences, some of which have economic importance and have been mined extensively. This study discusses the occurrence, geometry, relative timing and emplacement mechanisms for the Usakos pegmatite field, located between the towns of Karibib and Usakos and within the core of the regional-scale Kranzberg syncline. Lithological mapping of the Kuiseb Formation in the core of the Kranzberg syncline identified four litho-units that form an up to 800 m thick succession of metaturbidites describing an overall coarsening upward trend. This coarsening upwards trend suggests sedimentation of the formation’s upper parts may have occurred during crustal convergence and basin closure between the Kalahari and Congo Cratons, rather than during continued spreading as previously thought. The Kranzberg syncline is a regional-scale NW verging, NE-SW trending, strongly non-cylindrical structure that consists of a moderately SE dipping, normal NW limb and a steep- to overturned SE limb. First- and lower-order folds show relatively consistent E - SE plunges at moderate angles and stretching lineations and boudinage of competent layers point to a fold-parallel stretch during folding. Folding is associated with a moderate- to steep SE dipping transecting foliation that shows a consistent anticlockwise rotation with respect to the axial plane of the fold. The transecting cleavage and a component of non-coaxial shear along the overturned limb suggest that folding was accomopanied by a dextral component of shear thought to be related to the SW-directed extrusion of the adjacent Usakos dome during regional NW-SE directed shortening. It is further suggested that the Kranzberg syncline evolved within the overall regional pattern of regional dome and syncline structures in the sCZ, and not as a forced fold in response to the formation of neighbouring dome structures. Based on cross-cutting relationships and deformation, four main generations of bedding-concordant sills and bedding-discordant pegmatite dykes were identified. Along the normal limb, shallowly-dipping sills dominate, highlighting the significance of bedding anisotropies for sheet propagation. Along the overturned limb, interconnected dyke and sill geometries co-exist. Here, pegmatite emplacement appears to have been influenced by (1) the regional strain, (2) differing wall rock rheologies; (3) the orientation of pre-existing anisotropies; and (4) driving melt pressures. Dykes within the Usakos pegmatite field formed within dilational sites, at high angles to the regional stretch, whereas sills formed at high angles to the regional shortening strain and in contractional sites. Where driving pressures for melt ascent were high enough, an interconnectivity of dykes and sills and subsequent melt transfer from contractional into dilational sites is developed. Where melt pressures dropped below a critical value pegmatites were arrested, thus preserving the ascent pathways of the melts. These complex intersecting melt pathways are developed throughout the Kranzberg syncline. This suggests the existence of fairly stable melt networks in the continental crust. This geometrical complexity also accounts for the stockwork-like structures observed in pegmatite fields. / AFRIKAANSE OPSOMMING: Die Sentrale Sone (CZ) van die Damara gordel in sentrale Namibië is onder lê deur volumineuse Pan-Afrikaanse graniete en speel gasheer vir talle pegmatiet voorkomste, waarvan party van ekonomiese belang is en is ekstensief ontgin. Hierdie studie bespreek die voorkoms, geometrie, relatiewe tydsberekening en inplasing meganismes vir die Usakos pegmatiet gebied, wat tussen die stede van Karibib en Usakos en wat binne die kern van die regionale-skaal Kranzberg sinklien geleë is. Litologiese kartering van die Kuiseb Formasie in die kern van die Kranzberg sinklien het vier lito-eenhede geidentifiseer. Hierdie eenhede, wat saam tot 'n 800 m dik opeenvolging van metaturbidiete vorm, beskryf ‘n algemene opwaartse vergrowwing neiging. Hierdie tendens dui aan dat sedimentasie van die Formasie se boonste dele tydens die aardkorst konvergensie en kom sluiting tussen die Kalahari en die Kongo kratons voorgekom het, eerder as in 'n oseaanvloerverbreiding omgewing soos voorheen gedink was. Die Kranzberg sinklien is 'n regionale-skaal struktuur met ‘n NW vergensie, ‘n NOSW koersing, wat sterk nie-silindries is en wat uit 'n matige SO helling, normale NW flank en 'n steil-tot omgeslaande SO flank bestaan. Eerste-en laer-orde plooie vertoon relatief konsekwent matige O - SO duikings en strek lineasies en boudinage van kompetent lae dui 'n plooi parallel strek tydens plooiing aan. Plooiing is geassosieer met 'n ongeveer aksiale planêre, matig- tot steil SO helling foliasie wat omstandig waargeneem word om 'n konsekwente antikloksgewyse rotasie met betrekking tot die aksiale vlak van die plooi te hê. Hierdie antikloksgewyse rotasie is ‘n bewyse vir 'n komponent van nie-koaksiale regse skuifskeur deur die omgekeerde flank en dui dit ook aan dat 'n regse komponent van skeer gedurend of na plooiing plaasgevind het. Daar is gedink dat die regse komponent van skeur in verband met die laterale, SW-gerig extrusie van die aangrensende Usakos koepel gedurende plaaslike NW-SO verkorting ontwikkel het. Dit is verder voorgestel dat die Kranzberg sinklien binne die totale patroon van plaaslike koepel en sinklien strukture in die sCZ geontwikkel het, en nie as 'n gedwonge plooi in reaksie op die formasie van die naburige koepel strukture (bv. Usakos koepel). Gebaseer op kruis-sny verhoudings en deformasie, was vier generasies van gelaagdheid-konkordant plate en gelaagdheid-diskordant pegmatiet dyke geïdentifiseer. In die normale flank, vlak-helling plate oorheers, wat die belangerikheid van die laagvlak-anisotropiese op plaat voortplanting beklemtoon. In die steil, omgekeerde flank, bestaan onderlinge verbinde dyk en plaat geometrië gelyktydig. Hier is pegmatiet inplasing blykbaar beïnvloed deur (1) die regionale span; (2) verskillende wandgesteentes reologië; (3) die oriëntasies van anisotropie (ie. gelaagdheid ); en (4) smeltsel druk. Dyke in die Usakos pegmatiet gebied het binne dilatasionele liggings, teen hoë hoeke aan die regionale strek gevorm, terwyl plate teen hoë hoeke aan die plaaslike verkorting span en in kontraksionele liggings gevorm het. Waar smeltsel druk hoog genoeg was, is 'n onderlinge verbinding van dyke en plate, en die daaropvolgende smeltsel oordrag van kontraksionele liggings na dilatasionele liggings behou. In teenstelling, waar smeltsel druk onder 'n kritieke waarde geval het, word die pegmatiete geblokeer, en dus kan die behoude smeltsel styging paaie waargeneem word. Hierdie snyende smeltsel geometrië, in beide kontraksionele en dilatasionele liggings dui aan dat redelik stabiele smeltsel netwerke in die kontinentale kors kan bestaan en verder kan en verklaar die algemene stokwerk-agtige strukture wat in pegmatiet velde van ander mid-korstige omgewings waargeneem word.

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2010. / ENGLISH SUMMARY: Regional mapping of the Stinkbank granite in the south Central Zone of the Damara Belt, focused on an area of ca. 150 km2 in the SW parts of the granite along well exposed sections of the Khan River to the SW of the town of Usakos. The granite forms part of the regionally widespread granite suite of Salem-type granites that intruded at ca. 550-540 Ma into amphibolite-facies rocks of the Damara Supergroup. The Stinkbank granite is intrusive into the regional-scale, NE-trending D2 Kransberg syncline, cored by schists of the Kuiseb Formation and surrounded by marble units of the Karibib Formation. The granite comprises three major lithotypes that have intruded in sequence. The earliest granites are represented by biotite-rich megacrystic granites, followed by leucocratic megacrystic granites and a final stage of voluminous, garnetiferous and tourmaline-bearing, medium-grained leucogranites. Contact relationships with the wall rocks are, for the most part, concordant, documenting the largely sheet-like geometry of the granites. Internal contacts between different granite phases are well preserved and indicate that the granites have intruded as shallowly-dipping, largely concordant sheets. Intrusive contact relationships and petrographic and geochemical characteristics indicate that each of the three major granite phases represented a distinct emplacement pulse. Successive emplacement of the granite sheets point to the assembly of the Stinkbank granite from the top down, with younger sheets intruding structurally below earlier emplaced granite sheets. This has created a pseudostratigraphy within the Stinkbank granite. The mapping of the internal contacts shows that the granite sheets were progressively folded into NE-trending, upright folds, parallel to D2 folds in the surrounding wall rocks. NE-trending magmatic and solid-state foliations in all granite phases are axial planar to the folds and underline the syntectonic emplacement of the Stinkbank granite during the D2 NW-SE subhorizontal shortening. Based on the intrusive relationships and the progressive deformation of granite phases, an intrusive sequence can be developed for the Stinkbank granite. The earliest granite phases were emplaced during the onset of the regional D2 deformation, parallel to the subhorizontal bedding. Continued granite sheeting led to the vertical growth of the sheet-like granite and bending of the wall rocks above the inflating granite sheets, leading to the laccolithic geometry of the SW parts iii of the Stinkbank granite. Progressive deformation, folding of the granite sheets and fold amplification resulted in fold interference patterns in the SW parts of the Stinkbank granite. The Stinkbank granite represents a mid-crustal granite with well-preserved granite sheeting that was assembled during regional deformation. Granite sheeting and progressive deformation illustrate the interplay between (1) regional strains, and (2) the orientation and presence of pre-existing wall-rock anisotropies (bedding) and their significance for the magmatic assembly and progressive deformation of the granite. / AFRIKAANSE OPSOMMING: Regionale kartering van die Stinkbank graniet in die suidelike Sentrale Sone (sSS) van die Damara Gordel. Die studie fokus op die area van ongeveer 150 km2 in die SW dele van die graniet, langs n goed blootgestelde seksie van die Khan Rivier, SW van Usakos. Die graniet vorm deel van n wydverspreide suite van Salem- tipe graniete wat tussen 550-540 Ma in die amfiboliet fasies gesteentes van die Damara Supregroep ingedring het. Die Stinkbank graniet kom voor in regionale –skaal , NE – neigende D2 Kransberg Sinklinorium, wat bestaan uit skis van die Kuiseb Formasie en marmer van die Karibib Formasie. Die graniet bestaan uit drie hoof fases wat in volgorde ingedring het. Die oudste graniet is die biotiet-ryke megakristiese graniet, gevolg deur die leukokratiese megakristiese graniet en laastens die leukograniet. Kontak verhoudings met die wandgesteentes is grootendeels konkordant en dit dui op die feit dat die graniet uit lae bestaan. Die interne kontakte tussen die verskillende graniete is goed preserveer en dui aan dat die graniete voorkom as vlak lêende lae. Kontakverhoudings, petrografie en geochemiese karakteristieke dui aan dat elk van die die drie tiepes graniet uniek is. Die volgorde van intrusie van die Stinkbank graniet het voorgekom van bo na onder. Dit het n “skyn-stratigrafie” tot gevolg gehad. Kartering van die interne kontakte tussen die graniete het getoon dat die graniet lae is deurentyds gevou na NE- neigende, regop voue, parallel aan die D2 voue in die omringende wandegesteentes. NE- neigende magmatiese en soliede stadium foliasies in al die graniete is asvlak planêr aan die voue en dui ook op die syn-tektoniese intrusie van die Stinkbank graniet gedurende die D2 , NW-SE subhorisontale verkorting. Intrusiewe verhoudings en die progressiewe deformasie van die graniet, dui dat n volgorde verkry kan word vir die Stinkbank graniet. Die oudste graniet fase het ingedring gedurende die begin van die streekse D2 deformasie, parallel aan die subhorisontale gelaagdheid. Aanhoudende graniet-lae intrusies het gely tot die groei van n laag-ryke graniet en die buiging van die omliggende wangesteentes om dit n lakoliet vorm te gee in die SW dele van die Stinkbank graniet. Progressiewe deformasie, vouing van graniet lae en vergroting van voue het tot vou-interferensie patrone in die SW dele van die Stinkbank graniet tot gevolg gehad. Die Stinkbank graniet stel n middel- kors graniet met goed gepreserveerde gelaagdheid, wat gedurende regional deformasie ingedring het, voor. Graniet lae en progressiewe deformasie illustreer die verhouding tussen (1) regionale spanning en (2) die orientasie en teenwoordigheid van voorafbestaande wandgesteente anisotropie (gelaagdheid) en hulle belangrikheid vir die opbou en deformasie van die graniet.

A thesis submitted to the Faculty of Science in fulfilment of the requirements for the degree of Doctor of Philosophy at the School of Geosciences University of the Witwatersrand, Johannesburg, 2017 / Namibia, the 6th largest producer of uranium globally, has produced uranium from Pan African granite-hosted (primary) deposits since 1976, and from palaeochannel deposits since 2007; exporting 3 472 tonnes U in 2016. The large granite-hosted deposits at the Husab Mine are expected to add over 5 700 tonnes U/year at peak, while three large primary-hosted deposits remain in various stages of development at Goanikontes, the Ida Dome, and Valencia. This study presents a comprehensive geological, geochemical and uranium mineralogical appraisal of four of the major primary-hosted uranium deposits, all situated within the southern Central Zone (sCZ) of the polydeformational (D1-D3) Damara Belt. The sCZ comprises highly deformed Neoproterozoic sediments, unconformably draped over rheologically competent granite-gneiss domes and inliers of a Palaeoproterozoic basement. A suite of fractionated sheeted leucogranites (SLGs) are a characteristic of the final stages of Orogenic deformation; while most SLGs appear to precede D3 deformation and metamorphism (ca. 510 Ma); most of the mineralised SLGs across the region invade reduced-facies sediments in pressure shadows formed in the hinges and limbs of upright D3 antiforms, proximal to basement inliers. A pre-existing, six-fold, alphabetised SLG classification scheme is revised and extended to categorise distinctive and consistent field and petrographic characteristics of the SLGs across the region. Discriminating SLG sub-types is less consistent in standard geochemical diagrams, except where high field-strength (HFS) and rare-earth elements (REE) are concerned. REE profiles in pre-D3 SLGs reflect abundances, or paucities, of characteristic accessory mineral assemblages; while REE profiles show relative REE enrichment, prominent REEfractionation and -ve Eu anomalies in the uraniferous SLGs, reflecting lower-percentage partial melts in the more uraniferous samples. The overwhelming majority of primary uranium mineralisation is in magmatic uraninite, followed by coffinite which predominate as a replacement phase of uraninite, and more rarely as solid solution with thorite. The refractory minerals betafite and brannerite are rare, but are locally abundant in discrete, magmatic textures within uraniferous SLGs of some deposits. Hydrated uranyl silicates predominate in the supergene portions of the orebodies across the region. An electron microprobe study presents the first comprehensive assessment of uraninite compositions in the region, while Husab deposit betafite and brannerite compositions allow for a well-rounded comparison with refractory minerals from the Rössing deposits. Key Words Primary Uranium, Granite, Orogenic, Damara, Namibia, Rare Earth Elements, Mineralisation, Fractionation, High-grade Metamorphism, Economic Geology, Mining, Processing, Uraninite, Coffinite, Etango, Goanikontes, Husab, Ida Dome, Rössing, Valencia / XL2018

The ENE trending Brandberg West - Goantagab Sn-W belt is located in the Southern Kaoko Zone of the northern coastal branch of the Damara Orogen. The lithologies in this area are turbiditic and consist of three schist units separated by two marble horizons, all of which are correlated with the Swakop Group. The formations are intensely folded by at least three episodes of which the first two are coaxial and resulted in prominent, approximately N-S trending, structures. Sn and Sn-W mineralization predominantly occurs as vein and replacement type mineralization. Vein type mineralization occurs as Brandberg West, Frans Prospect, Gamigab Prospect and the Goantagab Mining Area. The vein type mineralization is accompanied by intense alteration, consisting of greisenization, sericitization, hematitization and carbonatization. Replacement-type, hematite-cassiterite mineralization, occurs in the Goantagab Mining area in the marble close to, or at the schist marble contact. Intense ferruginous alteration of the marbles in this area, is associated with veins, which terminate against, or cross cut the marble. A regional metal zonation, ranging from Sn-W mineralization with minor sulphides at Brandberg West to Sn-sulphide mineralization at Goantagab can be detected. This metal zonation is attributed to the distance of the mineral locality from the source area, with Goantagab representing a distal and Brandberg West a proximal position relative to the source area. Structural, mineralogical and geological features of the mineralization in this area suggest that processes of ore genesis may be related to anorogenic magmatism of Karoo age.

La chronologie de la formation de la croûte continentale est débattue mais la plupart des modèles convergent sur le fait qu'une bonne partie de la croûte continentale présente à la surface de la Terre aujourd'hui est présente depuis le Protérozoïque (2,5 - 0, 54 Ga) et qu'elle a essentiellement subit un remaniement au cours d'orogénèses. L'uranium, qui est un élément incompatible, est un traceur de cette évolution depuis son fractionnement initial par fusion partielle du manteau jusqu'à son remaniement dans les niveaux crustaux supérieurs. La ceinture orogénique Néoprotérozoïque Pan-africaine (0,5 ± 0,1 Ga) du Damara en Namibie constitue une cible géologique pour tester les relations entre croissance / évolution crustale et métallogénie de l'uranium. Elle s'est formée suite à la collision des cratons archéens du Congo et du Kalahari (plaque subductante). Ce travail de thèse montre que l'évolution de la croute continentale de la ceinture du Damara durant l'orogènese Pan-africaine au Néoprotérozoïque se fait par remaniement de roches ayant été extraites du manteau depuis l'Archéen et que leur fusion partielle est le mécanisme prépondérant pour la minéralisation uranifère primaire associée à la cristallisation de granites intrusifs. Les granites in-situ issus de la fusion partielle des sédiments dans les niveaux crustaux supérieurs sont peu ou pas propices à de fortes concentrations d'uranium du fait 1) de la faible préconcentration de leur protolithes et 2) de leur migration relativement limitée. Les granites intrusifs minéralisés correspondent à des injections tardi- à post-collision (ca. 520 - 480 Ma dans la zone centrale) et sont liés aux phases de relaxation thermique et d'effondrement gravitaire subséquentes à l'épaississement crustal de l'orogène dans un contexte de convergence de plaques / The chronology of continental crust formation is debated but most models converge on the fact that much of the continental crust on the surface of the Earth is present since the Proterozoic (2.5 - 0, 54 Ga) and has essentially undergoes reworking during orogenesises. Uranium which is an incompatible element is a tracer of this crustal evolution, since its initial fractionation by partial melting of the mantle to its reworking in higher crustal levels. Neoproterozoic Pan-African (0.5 ± 0.1 Ga) orogenic belt of the Damara in Namibia is a good geological target to test the relationship between crustal growth and evolution and metallogeny of uranium. It was formed after the collision of the Archean cratons of Congo and Kalahari (subducting plate). This thesis shows that the evolution of the continental crust during the Neoproterozoic Damara Orogen is by reworking of Archaean to Neoproterozoic crustal domains and partial melting of rocks is the predominant mechanism for primary uranium mineralization associated with crystallization of intrusive granites derived from anatexis of paleo- to mesoproterozoic basement fragments. The intrusive granites issued from partial melting of sediments in the upper crustal levels are low or not favorable to high concentrations of uranium because of 1) the low preconcentration of their protoliths and 2) their relatively limited migration. The mineralized intrusive granites correspond to late- to post-collision injections (ca. 520-480 Ma in the central area) and are related to thermal relaxation phases and gravitational collapse subsequent to thickening in crustal orogen in a context of plates convergence

This study aims to analyse the links between patriarchy in the bible, the Damara culture, and the ecclesiological practices of the Evangelical Lutheran Church in Namibia (ELCN). Using empirical research (interviews) and socio-historical methodology, the study demonstrates how biblical patriarchy affects married Damara women and evaluates the consequent roles of women in the religious context of the church, in the light of the biblical and cultural patriarchy which Damara women are subjected to. / Thesis (M.Th.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The NE-trending South Central Zone of the Pan-African (ca. 550-500) Damara orogen in central Namibia exposes deeply eroded mid-crustal rocks, thought to represent the magmatic arc of the Damara orogen. Above average exposure of outcrop left unmodified by subsequent post-orogenic processes made it possible to study the internal architecture of a ca. 50km traverse, stretching from the continental suture-zone (between the Congo craton in the NW and the underplating Kalahari craton in the SE) at the Okahandja Lineament Zone, well into the leading edge of the Congo craton and into the magmatic-arc, the South Central Zone. This study considers and characterises the change in structural styles and strain intensities in rocks of the Damara Supergroup and intrusions, across the traverse between the towns of Otjimbingwe in the SE and Karibib in the NW. In the SE of the traverse in the Okahandja Lineament Zone, steep, upright, tightly folded D2 fabrics in meta-turbidites of the Tinkas and Kuiseb Formations record bulk NW-SE shortening and steep SW extrusion of rocks. Penetrative non-coaxial fabrics imply a high-angle collsion between the Congo and Kalahari cratons. This is in contrast to oblique collision described by a number of previous authors (e.g. Blaine (1977), Stanistreet et al. (1991), Tack & Bowden, 1999). A marked decrease in D2 strain, and the presence of the silisiclastic basal Nosib group suggests the presence of the underlying basement rocks and thus the leading edge of the Congo craton only a few km NW of the Okahandja lineament. 8km NW of the Okahandja lineament is a km-scale NW verging F1 nappe, cored by basement gneisses and refolded into a series of bi-vergent, doubly-plunging F2 folds, the Audawib fold complex. The nappe is interpreted to have formed along a retroshear during early continental collision (syn-D1, early-D2). Tectonically overprinted basement rocks are indicative of thermal weakening, that resulted in the development of thick-skinned tectonics. Intruded mainly to the NW of and around the aforementioned nappe are the areally extensive syn-D2 Salem-type granites. Salem-type granites are shallowly intruded below the nappe and have likely detached the F1 nappe from its root. NW of the Salem-type granites lies a basement window of ca. 15km2 surrounded by the lower formations of the Damara Supergroup. Sheared marbles and D1 (early D2) diorites along the basement contact indicate a shallow sheared detachment occurring just above the basement. Basement rocks (1) unaffected by Damaran (D1-D2) tectonism and (2) unconformably overlain by the Damara Supergroup are indicative of thin skin tectonics in this part of the South Central Zone, some 30km NW of the Okahandja Lineament zone. Intrusive rocks across the South Central Zone suggest that deformation in the NW ceased by 540 Ma, while deformation along the Okahandja Lineament continued until at least 520 Ma. iii Along the Okahandja lineament, high angle continental collision resulted in tight, co-axial folding and lateral extrusion of rocks along the continental backstop. The introduction of numerous late-D2 granites around the Okahandja Lineament Zone (such as the massive Donkerhuk granite) resulted in thermal weakening of the crust, helping to accommodate lateral extrusion. Thermal weakening of the basement allowed the development of thick-skinned tectonics and the formation of the Audwib nappe. In the NW, cooler, more rigid crust deformed very differently to those in the SE, through shallow shearing, thin skinned tectonics. Diachronous timing of the deformation in rocks in the NW and SE of the traverse is due in part to the rheologic difference between cooler rocks in the NW that had locked up to deformation, much earlier than thermally weakened ones in the SE at the plate collision margin, where tectonic stresses where greater. / AFRIKAANSE OPSOMMING: Die NE-strekkende Suid Sentral Sone van die Pan-Afikaanse (ca. 550-500) Damara gordel in sentraal Namibië stel diep gëerodeerde gesteentes van die middelkors blood wat die magmaties boog van die Damara orogeen verteenwoordig. Goeie dagsome, ongemodifiseer deur subsekwente naorogenises prosesse het dit moontlik gemaak om ‘n studie aan te pak van die interne argitektuur van ‘n omenby 50km opname wat strek van die kontinentale skeidings sone (tussen die Congo kraton in die NW en die onderplatende Kalahari kraton in die SE) by die Okahandja Lineament Sone, tot ver oor die die voorste punt van die Congo kraton in die magmatiese-boog, die Suid Sentral Sone. Hierdie studie neem in ag en karakteriseer die verandering in struktuur styl en drukvervormings (strain) intensiteit in klippe van die Damara Supergroep, tussen die dorpies Otjimbingwe in die SE en Karibib in die NW. In die SE van die traverse in die Okahandja lineament zone vind ’n mens styl, regop, styf gevoude D2 maaksels in die Tinkas en Kuiseb Formasies, wat bulk NW-SE verkortende en styl SW ekstrusie van rotse aandui. Deurdringende nie-coaksiale maaksels impliseer n hoë-hoek botsing tussen die Congo en Kalahari kratons. Dit is in teenstryding met skeefhoekige botsing wat voorgestel is deur verskeie vorige outeurs (e.g. Blaine (1977), Stanistreet et al. (1991), Tack & Bowden, 1999). ‘n Vermindering in D2 drukvervorming (strain) en die teenwoordigheid van van die silisiklastiese basale Nosib groep, stel die verteenwoordigehid van die onderliggende vloergesteentes voor en sodoende, dat die voorste punt van die onderliggende Congo kraton net ‘n paar kilomeer NW van die Okahandja Lineament onwikkel is. 8km NW van die Okahandja Lineamnet is daar ‘n km-skaalse NW neigende F1 dekbladvou gekern deur gneis van die vloer gesteentes en hervou is tot ‘n klomp, bi-neigende, iv dubbel duikende F2 plooie in wat vernoem word die Audawib vou kompleks. Die dekbladvou word geinterpriteer om te gevorm het vooraan a retro-verkuiwing, gedurende vreeë kontinentale botsing (syn-D1, vroeë-D2). Oorverskuifde en herververvormde vloer gesteentes is ‘n aanduideing van termale verswakking in die aarkors, wat gelei het tot “thick-skinned” tektoniek. Intrusiewe gesteenste om, en na die NW van die Audawib dekblad vou is die’ weidverspreide Salem-tipe graniet. Syn-D2 Salem-tipe graniete is vlak intrusief to onder die dekblad vou en het waarskynlik die F1 vou van sy wortel sone ontkoppel. NW van die Salem tipe graniete lê ‘n 15km2 groote venster in die vloer gesteentes in omring deur die onderste formasies van die Damara Supergroep. Verskuifde marmer sowel en D1 (vroee-D2) dioriet lae op die vloer gesteente se boonste kontak dui daarop dat hierdie boonste kontak verskeurings losmaakpunt is, ‘n tektoniese kontak. Vloergesteentes (1) ongeaffekteerde deur Damara (D1-D2) tektoniek en (2) onkonformeerbare kontak met oorliggende klippe van die Damara Supergroep is ‘n aanduding van “thin-skinned” tektoniek in die gedeelte van die Suid Sentral Sone 30km NW van die Okahandja Lineament Sone. Intrusiewe gesteentes gee aanduidings dat deformasie in die NW reeds ge-eeindig teen 540 Ma, terwyl vervorming in die Okahandja Lineament Sone nog aktief was tot minstens 520 Ma. Oor die Okahandja Lineament het die hoe-hoekige kontinentale botsing gelei tot stywe ko-aksiale plooing en laterale ekstrusie van gesteentes langs die kontinentale “backstop”. Die intrusie van verskeie laat-D2 grantiete (soos die masiewe Donkerhuk graniet) in die Okahandja lineament sone het gelei tot termale verswaking van die kors wat gehelp het om laterale ekstrusie van klippe te akkomodeer. Termale verswakking van vloer gesteentes het gelei tot die onwikkeling van “thickskinned” tektoniek en die vorming van die Audawib dekblad vou. In die NW, het koeler, stewiger gesteentes anders vervorm as daardies verder suid, deur vlak skeur-verkuiwings, “thin-skinned” tectonics. Nie-samelopende vervorming in gesteentes in die NW en SE van die opname is die gevolg van die rheologiese verskil tuseen die koeler gesteentes in die NW wat vroeer bestand geraak het teen vervorm as warmer gesteentes in die SE teenaan die botsings sone, waar tektoniese druk boonop groter was.

Digitized from microfiche to pdf. / Thesis (PhD(Agric) (Human and Animal Physiology))--University of Stellenbosch, 1998. / Please refer to full text.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy, Johannesburg 2014 / Namibia is renowned for its abundant mineral resources, a large proportion of which are hosted in the metasedimentary lithologies of the Damara Belt, the northeast-trending inland branch of the Neoproterozoic Pan-African Damara Orogen. Deposit types include late- to post-tectonic (~ 523 – 506 Ma) LCT (Li-Be, Sn-, and miarolitic gem-tourmalinebearing) pegmatites, and uraniferous pegmatitic sheeted leucogranites (SLGs), which have an NYF affinity. Fluid inclusion studies reveal that although mineralization differs between the different types of pegmatites located at different geographic locations, and by extension, different stratigraphic levels, the fluid inclusion assemblages present in these pegmatites are similar; thus different types of pegmatites are indistinguishable from each other based on their fluid inclusion assemblages. Thorough fluid inclusion petrography indicated that although fluid inclusions are abundant in the pegmatites, no primary fluid inclusions could be identified, and rather those studied are pseudosecondary and secondary. Fluid inclusions are aqueo-carbonic (± NaCl), carbonic, and aqueous. It is proposed that all of the pegmatites studied share a similar late-stage evolution, with fluids becoming less carbonic and less saline with the progression of crystallisation. Oxygen isotope ratios allow the discrimination of different pegmatites into two groups, Group A (Sn-, Li-Sn-, and gem-tourmaline-bearing LCT pegmatites), and Group B (Li-Bebearing LCT, and U-bearing NYF pegmatites). Group A pegmatites have O-isotope ratios ranging from 11 to 13 ‰ suggesting that they have an I-type affinity. These values are, however, elevated above those of typical I-type granites (7 - 9 ‰), indicating either a postemplacement low-temperature exchange with meteoric fluid, high-temperature hydrothermal exchange with δ18O country rocks during emplacement, or the derivation of these pegmatites from a non-pelitic/S-type metaigneous source. Group B pegmatites have higher δ18O ratios (δ18O = 15 - 16 ‰), indicative of their S-type affinity, and their derivation from metapelitic source rocks. δD values of all the pegmatites range from -40 ‰ to -90 ‰ indicating that the pegmatitic fluids are primary magmatic with a metamorphic fluid component. Trends in the trace element concentrations of both Group A and Group B pegmatites are very similar to each other, making the two groups indistinguishable from each other on this basis. The Damaran pegmatites also share similar geochemical trends with their country rocks. There is, however, no direct field evidence to suggest that the pegmatites were derived from the in situ anatexis of the country rocks. It is more likely that anatexis occurred some distance away from where the pegmatites were ultimately emplaced, and that the melts migrated and were finally emplaced in pre-existing structures, possibly formed during Damaran deformation. O-isotope and Ti-in-quartz geothermometry indicate that Damaran pegmatites can be subdivided into two groups based on their crystallisation temperatures. LCT pegmatites crystallised at temperatures ranging from ~ 450 - 550 ºC, while the NYF pegmatites crystallised at higher temperatures, ranging from 630 - 670 ºC. It is important to note that the subdivision of pegmatites in Groups A and B based on their O-isotope systematics does not correspond with their subdivision into the LCT and NYF pegmatite families according to their crystallisation temperatures. In addition to clarifying aspects of the emplacement and evolution of the Damaran pegmatites, this study points out that there are several discrepancies in the current classification schemes of pegmatites. It shows that in addition to the problems encountered when trying to distinguish between LCT and NYF pegmatites based on their mineralogy, they also cannot truly be distinguished from each other using their geochemical and isotopic characteristics, or their tectonic settings. It is tentatively proposed that crystallisation temperature be considered as an alternative or additional characteristic in the classification of pegmatites, and that it be considered on a regional scale rather than only in the evaluation of the highly evolved end-members of a pegmatite swarm.