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Geology of the Palaeoproterozoic Daspoort Formation (Pretoria Group, Transvaal Supergroup), South AfricaBartman, R.D. (Reynard Dirk) January 2013 (has links)
This thesis examines the geology of the Daspoort Formation (Pretoria Group, Transvaal Supergroup) of
South Africa, with the accent on describing and interpreting its sedimentology. The Palaeoproterozoic
Daspoort Formation (c. 2.1‐2.2 Ga) forms part of the Pretoria Group on the Kaapvaal craton. This
sandstone‐ and quartzite‐dominated lithological formation covers an elliptical geographical area
stretching from the Botswana border in the west to the Drakensberg escarpment in the east, with its
northern limit in the Mokopane (Potgietersrus) area and Pretoria in the south; altered outliers are also
found in the overturned units of the Vredefort dome in the Potchefstroom area. Deposition of the
Daspoort Formation was in a postulated intracratonic basin which applies equally to the entire
Transvaal Supergroup succession in the Transvaal depository. Various characteristics from the
formation, such as sedimentary architectural elements (e.g., channel–fills etc.), maturity trends and
distribution of lithofacies assemblages across the preserved basin give insight into the developing
conditions during deposition and genesis of the Daspoort Formation. Subordinate evidence from basic
geochemistry, ripple mark data and optical microscope petrology studies support the sedimentary
setting inferred for this Palaeoproterozoic deposit. Fluvial and epeiric marine conditions prevailed
during the deposition of the Daspoort clastic sediments into the intracratonic basin. This shallow
epeiric sea was fed by fluvial influx, predominantly from the west when a transgressive regional
systems tract led to the filling of the basin, evolving into the deeper marine Silverton Formation
setting, laid down above the Daspoort. Transgression from the east (marine facies predominate) to the
west (fluvial facies) is supported by cyclical trends, palaeoenvironmental and palaeogeographical
interpretations. Accompanying poorly preserved microbial mat features contribute to the postulated
shallow marine environment envisaged for the eastern part of the basin whereas ripple marks and
grain size distribution support a fluvial setting for the west, with lithofacies assemblages accounting for
both areas’ depositional interpretation. / Dissertation (MSc)--University of Pretoria, 2013. / tm2014 / Geology / Unrestricted
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The Geology of the Rustenburg FaultBumby, Adam John January 1997 (has links)
The N.N.W.-S.S.E. striking Rustenburg Fault zone, in the western Transvaal Basin, South Africa,
has been mapped, in order to unravel its tectonic history. Thickness differences in the Daspoort
Formation of the Pretoria Group on opposite sides of the Fault suggest that the Fault was active
during Pretoria Group sedimentation, with normal faulting producing localised second-order basins
on the down-thrown side of the Fault.
In post-Pretoria Group times, but before the intrusion of the Bushveld Complex at -2050 Ma, the
area surrounding the Fault zone underwent two compressive events. The first was directed N.E.S.
W., producing S.E.-N.W. trending folds, and the second was directed N.W.-S.E., producing
N.E.-S.W. trending folds. The second set of folds refolded the first set to form typical transitional
Type 1-Type 2 interference folding, and this compression ultimately caused reactivation of the
Rustenburg Fault, so that dextral strike-slip movement displaced the Pretoria Group sediments by
up to 10.6 km.
The subsequent intrusion of the Bushveld Complex into the adjacent strata intensely recrystallised,
and often assimilated, the strata along the Fault zone. The fault rocks within the Fault zone were
also recrystallised, destroying any pre-existing tectonic fabric. Locally, the Fault zone has been
assimilated by the Bushveld Complex.
After the intrusion of the Bushveld Complex, little movement has occurred along the Fault,
especially where the Fault passes under areas occupied by the Bushveld Complex. It is thought
that the crystallisation of the Bushveld Complex has rheologically strengthened the neighbouring
strata, preventing them from being refaulted.
This model presented above is at variance with previous assumptions that continuous regional
extension during Pretoria Group sedimentation culminated in the intrusion of the Bushveld
Complex. / Dissertation (MSc)--University of Pretoria, 1997. / gm2015 / Mining Engineering / MSc / Unrestricted
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Metamorphism in the contact aureole of the eastern limb of the Bushveld complex, South AfricaMavimbela, Philane Knowledge January 2013 (has links)
The 2.06 to 2.054 Ga Bushveld Igneous Complex intruded into the sedimentary rocks of the Transvaal Supergroup and generated an extensive contact metamorphic aureole mainly developed in the upper Pretoria group. The studied samples represent the Silverton Daspoort and Timeball Hill formations and are divisible into garnet bearing hornfels (DY918, DY954 and DY956) and garnet-free staurolite-bearing metapelites (DY916, DY982 and DY987). The garnet-bearing hornfelses marks the garnet zone within the aureole and the garnet formation is controlled by different reactions forming from 490 to 630 0C. On the other hand, the garnet free staurolite-bearing Fe-Al rich metapelites define the staurolite zone restricted to the Timeball Hill formation. The recorded P-T conditions in G0 and G1 garnets of the DY954 hornfels imply that the two garnets formed under different conditions indicating two stages of metamorphism. However, the Lu-Hf isotope systematics of these garnets records a 2061 Ma age for all garnet porphyroblasts in both the DY918 and DY954 hornfelses, which support co-genetic garnet growth regardless of their stratigraphic positions. Therefore, the 2061 Ma garnet age denote the emplacement age of the Lower Zone and Critical Zone magmas which was synchronous with the extrusion of the Rooiberg Group volcanics. The fact that all analysed garnets do not record the 2059 – 2054 intrusion of the Main Zone and Upper Zone magmas probably means that the crystallisation temperatures of the later magma pulse was not significant enough to shift the Lu-Hf isotopic signatures. Euhedral staurolites are widespread within the Fe-Al rich metapelites with grain sizes of up 4mm; texturally the majority of them have been altered or overgrown by biotite and chloritoid. The alteration or of these staurolite porphyroblasts is due to isobaric cooling during uplift, and the St-Bt assemblage represent the peak equilibrium conditions and marks the upper stability limit of the Chl-Ctd assemblage. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Geology / unrestricted
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MachinariumVan Eeden, Heidi 09 December 2013 (has links)
Machinarium is an exploration of industrial bio-mechanical hybridity as part of the 21st Century paradigm.
The dissertation investigates the potential of industry as urban catalyst - a mechanism with which to regenerate urban environments and re-integrate socio-ecological systems.
In an attempt to redefine modern concepts of waste and mitigate the flood of pollution emanating from 20th century industrialisation, the investigation is contextually based in an ‘urban wasteland’ - which is re-programmed as part of a new industrial ecology. The dissertation therefore blurs present-day distinctions between ‘social’, ‘productive’ and ‘natural’ space, while at the same time placing focus on the global cultural dependence on waste.
If humankind is to survive the predicted crises of the our time, a 21st-century approach to design must shift the modern understanding of architecture as ‘machines for living in’ towards that of architecture as living machines.
Machinarium alludes to new ways of architectural place-making in a rapidly changing world. / Dissertation MArch(Prof)--University of Pretoria, 2014. / Architecture / MArch(Prof) / Unrestricted
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