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Journal articles on the topic "Structural bushveld complex south africa"
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Bamisaiye, Oluwaseyi Adunola. "Geo-Spatial Mapping of the Western Bushveld Rustenburg Layered Suite (Rls) in South Africa." Journal of Geography and Geology 7, no. 4 (December 2, 2015): 88. http://dx.doi.org/10.5539/jgg.v7n4p88.
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Trend surface analysis (TSA) was used to investigate the structure and thickness variation pattern and to resolve trend and residual component of the structure contours and isopach maps of the Rustenburg Layered Suite (RLS) across the Bushveld Igneous Complex (BIC). The TSA technique was also employed in extracting meter scale structures from the regional structural trends. This enables small-scale structures that could only be picked through field mapping to be observed and scrupulously investigated. Variation in the structure and thickness was used in timing the development of some of the delineated structural features. This has helped to unravel the progressive development of structures within the RLS. The results indicate that present day structures shows slight changes in both regional and local trends throughout the stratigraphic sequence from the base of the Main Zone to the top of the Achaean floor. Structures around the gap areas are also highlighted. This paper represents the third of a three-part article in Trend Surface analysis of the three major limbs of the Bushveld Igneous Complex (BIC). This first part focused on the Northern Bushveld Complex, while the second part focused on the Eastern Bushveld Limbs.
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Clarke, Brendan, Ron Uken, and Jürgen Reinhardt. "Structural and compositional constraints on the emplacement of the Bushveld Complex, South Africa." Lithos 111, no. 1-2 (July 2009): 21–36. http://dx.doi.org/10.1016/j.lithos.2008.11.006.
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Nex, Paul A. M. "The structural setting of mineralisation on Tweefontein Hill, northern limb of the Bushveld Complex, South Africa." Applied Earth Science 114, no. 4 (December 2005): 243–51. http://dx.doi.org/10.1179/037174505x62901.
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Longridge, Luke, Roger L. Gibson, and Paul A. M. Nex. "Structural controls on melt segregation and migration related to the formation of the diapiric Schwerin Fold in the contact aureole of the Bushveld Complex, South Africa." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 100, no. 1-2 (March 2009): 61–76. http://dx.doi.org/10.1017/s1755691009016119.
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ABSTRACTPartial melting of metapelitic rocks beneath the mafic–ultramafic Rustenburg Layered Suite of the Bushveld Complex in the vicinity of the periclinal Schwerin Fold resulted in a structurally controlled distribution of granitic leucosomes in the upper metamorphic aureole. In the core of the pericline, subvertical structures facilitated the rise of buoyant leucosome through the aureole towards the contact with the Bushveld Complex, with leucosomes accumulating in en-echelon tension gashes. In a subhorizontal syn-metamorphic shear zone to the southeast of the pericline, leucosomes accumulated in subhorizontal dilational structural sites. The kinematics of this shear zone are consistent with slumping of material off the southeastern limb of the rising Schwerin pericline. The syndeformational timing of leucosome emplacement supports a syn-intrusive, density-driven origin for the Schwerin Fold. Modelling of the cooling of the Rustenburg Layered Suite and heating of the floor rocks using a multiple intrusion model indicates that temperatures above the solidus were maintained for >600,000 years up to 300 m from the contact, in agreement with rheological modelling of floor-rock diapirs that indicate growth rates on the order of 8 mm/year for the Schwerin Fold.
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Bamisaiye, O. A., P. G. Eriksson, J. L. Van Rooy, H. M. Brynard, S. Foya, A. Y. Billay, and V. Nxumalo. "Subsurface mapping of Rustenburg Layered Suite (RLS), Bushveld Complex, South Africa: Inferred structural features using borehole data and spatial analysis." Journal of African Earth Sciences 132 (August 2017): 139–67. http://dx.doi.org/10.1016/j.jafrearsci.2017.05.003.
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Cawthorn, R. G., K. L. Lundgaard, C. Tegner, and J. R. Wilson. "Lateral variations in plagioclase compositions, Main Zone, Bushveld Complex, South Africa: Evidence for slow mixing of magmas in basinal structures." Mineralogical Magazine 80, no. 2 (April 2016): 213–25. http://dx.doi.org/10.1180/minmag.2015.079.7.12.
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AbstractMany layered intrusions are considered to have been repeatedly inflated by magma additions, but rates of magma mixing relative to rates of layer accumulation are difficult to model. The nature of magma recharge through the interval including the Pyroxenite Marker (PM), Main Zone, Bushveld Complex, South Africa, is examined with regard to such processes. The plagioclase compositions (An value) in five previously published and three new profiles (presented here and focusing on the core compositions) that are at least 600 m in vertical extent and spread along a strike length of 110 km are evaluated. The compilation of the eight profiles shows the following trends. Upward reversals in compositions show considerable lateral as well as vertical variations. Lateral variations show a range in: (1) the minimum An value reached in each profile prior to the onset of magma recharge (An51 to An59); (2) the depth below the PM at which the minimum value is observed (50 to 575 m); (3) the An value close to the PM (An54 to An75); (4) the maximum value recorded above the PM (An63 to An76); (5) the height above the PM at which this maximum value is reached (0 to 300 m) – in all cases, the highest values of An occur at the northern end of the studied sections; and (6) the vertical extents over which the reversals occur range from 150 to over 600 m indicating very protracted magma additions and/or slow mixing. The PM terminates toward the south, and close to this termination the immediate footwall rocks to the PM change from north to south from gabbronorite to magnetite gabbronorite. A cross-section through these profiles defines two basins, with an intervening structural upwarp. The magma pulses that were added to produce very gradual and protracted reversals in mineral compositions through the PM interval ponded initially at the base of the northern basin, and did not homogenize the entire magma column. These added magmas did not overflow and have an effect on mineral compositions in the southern basin until after considerable replenishment and crystallization (including the PM) had taken place in the northern basin. We emphasize the prolonged period(s) of magma input and slow rate of vertical homogenization of the magma column during the formation of this sequence of as much as 400 m of the Main Zone.
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Uken, Ronald, and Michael K. Watkeys. "Diapirism initiated by the Bushveld Complex, South Africa." Geology 25, no. 8 (1997): 723. http://dx.doi.org/10.1130/0091-7613(1997)025<0723:dibtbc>2.3.co;2.
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Campbell, Geoff. "Exploration geophysics of the Bushveld Complex in South Africa." Leading Edge 30, no. 6 (June 2011): 622–38. http://dx.doi.org/10.1190/1.3599148.
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Perritt, Sam, and Mike Roberts. "Flexural-slip structures in the Bushveld Complex, South Africa?" Journal of Structural Geology 29, no. 9 (September 2007): 1422–29. http://dx.doi.org/10.1016/j.jsg.2007.06.008.
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Jones, M. Q. W. "Heat flow in the Bushveld Complex, South Africa: implications for upper mantle structure." South African Journal of Geology 120, no. 3 (September 1, 2017): 351–70. http://dx.doi.org/10.25131/gssajg.120.3.351.
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Abstract Geothermal measurements in South Africa since 1939 have resulted in a good coverage of heat flow observations. The Archaean Kaapvaal Craton, in the central part of South Africa, is the best-studied tectonic domain, with nearly 150 heat flow measurements. The greatest density of heat flow sites is in the Witwatersrand Basin goldfields, where geothermal data are essential for determining refrigeration requirements of deep (up to 4 km) gold mines; the average heat flow is 51 ± 6mWm-2. The Bushveld Complex north of the Witwatersrand Basin is an extensive 2.06 Ga ultramafic-felsic intrusive complex that hosts the world’s largest reserves of platinum. The deepest platinum mines reach ~2 km and the need for thermal information for mine refrigeration engineering has led to the generation of a substantial geothermal database. Nearly 1000 thermal conductivity measurements have been made on rocks constituting the Bushveld Complex, and borehole temperature measurements have been made throughout the Complex. The temperature at maximum rock-breaking depth (~2.5 km) is 70°C, approximately 30°C higher than the temperature at equivalent depth in the Witwatersrand Basin; the thermal gradient in the Bushveld Complex is approximately double that in the Witwatersrand Basin. The main reason for this is the low thermal conductivity of rocks overlying platinum mines. The Bushveld data also resulted in 31 new estimates for the heat flux through the Earth’s crust. The overall average value for the Bushveld, 47 ± 7 mW m-2, is the same, to within statistical error, as the Witwatersrand Basin average. The heat flow for platinum mining areas (45 mW m-2) and the heat flux into the floor of the Witwatersrand Basin (43 mW m-2) are typical of Archaean cratons world-wide. The temperature structure of the Kaapvaal lithosphere calculated from the Witwatersrand geothermal data is essentially the same as that derived from thermobarometric studies of Cretaceous kimberlite xenoliths. Both lines of evidence lead to an estimated heat flux of ~17 mW m-2 for the mantle below the Kaapvaal Craton. The estimated thermal thickness of the Kaapvaal lithosphere (235 km) is similar to that defined on the basis of seismic tomography and magnetotelluric studies. The lithosphere below the Bushveld Complex is not significantly hotter than that below the Witwatersrand Basin. This favours a chemical origin rather than a thermal origin for the upper mantle anomaly below the Bushveld Complex that has been identified by seismic tomography studies and magnetotelluric soundings.
Dissertations / Theses on the topic "Structural bushveld complex south africa"
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Curl, Edward Alexander 1972. "Parental magmas of the Bushveld Complex, South Africa." Monash University, Dept. of Earth Sciences, 2001. http://arrow.monash.edu.au/hdl/1959.1/9080.
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Everitt, Simon James. "Evolution of the UG2 unit, Bushveld Complex, South Africa : mineral composition and petrological evidence." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001573.
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Several disequilibrium textures are found to occur within the hanging wall and footwall of the UG2 chromitite layer of the Bushveld Complex, South Africa. These textures include plagioclase chadacrysts found included within orthopyroxene and clinopyroxene as well as the orthopyroxenes exhibiting round crystal boundaries that appear to be resorbed. Textures found within the UG2 stratigraphy such as linear boundaries and 120° triple junctions at interfaces of adjacent plagioclase or pyroxene grains also suggest that recrystallization has taken place. The presence of both disequilibrium textures and recrystallization textures would suggest that a complex emplacement history has occurred. Ideally, this would be expected to be manifested by minerals of the same type but which are texturally distinct showing different composition. However this has been found not to be the case; minerals that suggest disequilibrium textures show similar compositions to the minerals which appear to have formed in equilibrium. This is also the same for recrystallized crystals which show the same compositions as crystals that have not been recrystallized. For example tabular clinopyroxene, which has a compositional range of En 44.6 to En 50.5, is indistinguishable from clinopyroxene occuring as discontinuous rims, En 44.3-48.2, and as intergranular necking connecting primocrysts of orthopyroxene ( En 44.3-50.4). Similarly, plagioclase occurring as inclusions with An 66.3-76.0 is indistinguishable from plagioclase occurring as zoned or recrystallized interstitial grains ( An 69.0- An 77.4). Compositional variation has however, been found to be controlled to an extent by stratigraphy in that minerals show different compositions within one layer to the same minerals within another layer, consistent with an evolving magma composition. It is concluded therefore that while composition is not texturally controlled it is to an extent stratigraphy controlled and that the evidence collected within the study supports two models for the formation of chromite within the Bushveld complex. The evidence is consistent with a combination of the magma mixing model and magma injection model to account for the textures and compositional variations found within the study. The evidence may also show support for models involving late modification of minerals by magmatic fluids but not as prominently as for the models mentioned aboveMicrosoft� Word 2010
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Gwatinetsa, Demand. "Distribution of iron-titanium oxides in the vanadiferous main magnetite seam of the upper zone : Northern limb, Bushveld complex." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1013281.
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The main magnetite seam of the Upper Zone of the Rustenburg Layered Suite (SACS, 1980) on the Bushveld Complex is known to host the world‘s largest vanadium bearing titaniferous iron ores. The vanadiferous titanomagnetites, contain vanadium in sufficient concentrations (1.2 - 2.2 per cent V₂O₅) to be considered as resources and vanadium has been mined historically by a number of companies among them Anglo-American, Highveld Steel and Vanadium and VanMag Resources as well as currently by Evraz Highveld Steel and Vanadium Limited of South Africa. The titanomagnetites contain iron ore in the form of magnetite and titanium with concentrations averaging 50-75 per cent FeO and 12-21 per cent TiO₂. The titaniferous iron ores have been historically dismissed as a source of iron and titanium, due to the known difficulties of using iron ore with high titania content in blast furnaces. The economic potential for the extractability of the titaniferous magnetites lies in the capacity of the ores to be separated into iron rich and titanium rich concentrates usually through, crushing, grinding and magnetic separation. The separatability of iron oxides and titanium oxides, is dependent on the nature in which the titanium oxide occurs, with granular ilmenite being the most favourable since it can be separated from magnetite via magnetic separation. Titanium that occurs as finely exsolved lamellae or as iron-titanium oxides with low titania content such as ulvospinel render the potential recoverability of titanium poor. The Upper Zone vanadiferous titanomagnetites contain titanium in various forms varying from discrete granular ilmenite to finely exsolved lamellae as well as occurring as part of the minerals ulvospinel (Fe₂TiO₄) and titanomagnetite (a solid solution series between ulvospinel and magnetite) . Discrete ilmenite constitutes between 3-5 per cent by volume of the massive titanomagnetite ores, and between 5-10 per cent by volume of the magnetite-plagioclase cumulates with more than 50 per cent opaque oxide minerals. The purpose of this research was to investigate the mineralogical setting and distribution of the iron and titanium oxides within the magnetitite layers from top to bottom as well as spatially along a strike length of 2 000m to determine the potential for the titanium to be extracted from the titanomagnetite ores. The titanomagnetites of the Upper Zone of the Bushveld Complex with particular reference to the Northern Limb where this research was conducted contains titanium oxides as discrete ilmenite grains but in low concentrations whose potential for separate economic extraction will be challenging. The highest concentration of titanium in the magnetite ores is not contained in the granular ilmenite, but rather in ulvospinel and titanomagnetite as illustrated by the marked higher concentration of TiO₂ in the massive ores which contain less granular ilmenite in comparison to the disseminated ores which contain 3 to 8 percentage points higher granular ilmenite than the massive ores. On the scale of the main magnetite seam, the TiO₂ content increases with increasing stratigraphic height from being completely absent in the footwall anorthosite. The V₂2O₅ content also increases with stratigraphic height except for in one of the 3 boreholes where it drops with increasing height. The decrease or increase patterns are repeated in every seam. The titanomagnetites of the main magnetite seam display a variety of textures from coarse granular magnetite and ilmenite, to trellis ilmenite lamellae, intergranular ilmenite and magnesian spinels and fine exsolution lamellae of ulvospinel and ferro-magnesian spinels parallel to the magnetite cleavage. The bottom contact of the main magnetite seam is very sharp and there is no titanium or vanadium in the footwall barely 10cm below the contact. Chromium is present in the bottom of the 4 layers that constitute the main magnetite seam and it upwards decreases rapidly. In boreholes P21 and P55, there are slight reversals in the TiO₂ and V₂O₅ content towards the top of the magnetite seams.
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Sargeant, Fiona. "The seismic stratigraphy of the Bushveld Igneous Complex, South Africa." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250322.
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Mooney, David G. "An evaluation of small scale open cast mining of UG2 in the Bushveld complex." Thesis, Rhodes University, 1997. http://hdl.handle.net/10962/d1005555.
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The current weak state of the platinum market, as well as the large inventory of platinum group metals held by Russia, necessitates that the South African platinum mining industry must carefully evaluate the benefits and disadvantage of small-scale mining of shallow, open castable ore resources. Until the late 1980's, these resources were ignored due to the metallurgical complexities of treating oxidized ore, as well as the mind set that existed within the South African mining industry which militated against open cast mining in the Bushveld. During the latter part of the 1980's and early 1990's, advances in the metallurgical treatment of oxidized ore, specifically the UG2, as well as operational problems, created the impetus to begin the exploitation of these resources. Small-scale open cast mining has become viable due to the development of suitable mining methods that facilitate mining practices acceptable to the Department of Mineral and Energy Affairs, in terms of environmental legislation. Metallurgical advances and growing experience, especially with respect to the UG2, enables reasonable platinum group metals recovery from oxidized ore. The problems experienced in doing this can, and are being overcome. With growing public awareness of environmental issues, particularly related to the mining industry, the requirement to ensure that the small-scale open cast mine site is well managed is paramount. A methodology for the evaluation is presented along with a case study of a small-scale UG2 open cast pit. Evidence is presented that shows that these small-scale open cast mining operations are extremely profitable and require minimal capital expenditure. However, caution is advised when evaluating Merensky Reef open cast operations because of the problems that they present.
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Teigler, Bernd. "Mineralogy, petrology and geochemistry of the lower and lower critical zones, Northwestern Bushveld Complex." Thesis, Rhodes University, 1991. http://hdl.handle.net/10962/d1005590.
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This study of the lower part of the Rustenburg Layered Suite in the Western Bushveld Complex is based mainly on drill core samples from three localities, which are approximately 130 km apart. The NG-sequence, situated in the northwestern sector of the complex (Union Section, R.P.M.) extends from the floor of the complex to the base of the upper Critical Zone. The sequence is ca. 1800 m thick and it comprises mainly ultramafic cumulates, namely pyroxenites, olivine pyroxenites, harzburgites and dunites. Norites and anorthos ites are present only in minor proportion. Within the upper half of the NG-sequence ten prominent chromitite layers are correlated with the LGI MG4-interval. Correlation is also established between published sequences and the two other sequences studied, located 8 km and 55 km, respectively, east of Rustenburg. Whole-rock chemical data (major and trace elements), microprobe and Sr isotope data are presented. Petrographic studies provide modal analyses and measurements of grain size. All petrographic, mineralogical and other geochemical data point to an origin of the cumulates of the NG-sequence by crystallization from liquids of the U-type lineage and derivatives thereof. No evidence is found for the involvement of parental liquids with a distinctly different composition or crystallization order (A-liquids). However, subtle compositional variations of the parental liquids are evident in slight changes of the Cr content in orthopyroxene or in variations of Sr isotope ratio. The NG-sequence is characterized by intervals with reversed fractionation trends caused by repeated influxes of pristine magma (during periods of high magmatic activity) resulting in a high degree of rejuvenation. These intervals are overlain by others with a normal fractionation trend, interpreted as cumulates formed in periods with low or no magmatic activity, in which fractional crystallization controlled bulk composition of the evolving liquid. The Lower Zone in the NG-sequence is dominated by a progressive shift towards more primitive compositions, while in the Critical Zone fractionation was the major operating process in the magma chamber. However, during deposition of the pyroxenitic lower Critical Zone several replenishment events occurred, during which fresh Cr-rich magma was emplaced. Massive chromitite layers were deposited after mixing between the newly emplaced magma and the resident residual liquid shifted bulk compositions into the primary field of chrome-spinel. Cumulus plagioclase crystallized after bulk composition of the residual liquid was driven to the orthopyroxene plagioclase cotectic by continued fractional crystallization; this occurred once in the Lower Zone, yielding a single, thin norite layer, and again in the upper Critical Zone of the NG-sequence. A facies model is proposed based on the stratigraphic and compositional variations along strike in the Western Bushveld Complex. This model explains the variations by means of the position of the sequence with regard to a feeder system. The olivine- and orthopyroxene-rich, but plagioclase-poor NG-sequence represents the proximal facies, while the SF-sequence (poor in ferromagnesian phases, but plagioclase-rich) is developed as a distal facies, close to the Brits graben.
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Haikney, Susan Ann. "The nature of olivine-rich cumulate rocks of the lower critical and lower zones of the northwestern Bushveld Complex." Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005592.
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Boreholes NG1 and NG2 were drilled on the farm Nooitgedacht 406 KQ to intersect the lower Critical and lower Zones of the western Bushveld Complex. The aim of this study is to describe the textural features and chemical characteristics of the olivine-bearing rocks in the intersections, as determined by petrographic studies, XRF analysis and microprobe analysis. The olivine-bearing rocks are dunites, harzburgites and olivine pyroxenites. They comprise olivine and orthopyroxene, with minor chromite, clinopyroxene and plagioclase, and their textures vary between adcumulate, mesocumulate and poikilitic. The sequence intersected can be broadly correlated with that in the eastern Bushveld Complex. Of the whole-rock inter-element ratios, the MMF (MgO)/[MgO+FeO])ratio is the clearest indicator of cyclicity. The olivine-rich rocks are more primitive than the associated rocks, and seem to become more primitive with height in most intervals. The plagioclase in the olivine-bearing rocks is unusually sodic in corrposition, having a maximum Na₂0 content of 8.12%. A comparison of olivine and plagioclase compositions with those in other intrusions has revealed that the only other major intrusion with sodic plagioclase is the Kiglapait intrusion of Canada. In the Kiglapait intrusion the sodic plagioclase occurs in conjunction with fayalitic olivine as opposed to the forsteritic variety of this study. Chemical variations in the rocks sampled indicate that periodic replenishment of the magma from which the rocks crystallised must have occurred. In some of the olivine-bearing intervals where little fractionation is evident, replenishment seems to have been continuous. In other intervals fractionation appears to have continued uninterrupted for significant periods, prior to rejuvenation by fresh influxes of magma.
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Mitchell, Andrew Alexander. "The petrology, mineralogy and geochemistry of the main zone of the Bushveld Complex at Rustenburg Platinum Mines, Union Section." Thesis, Rhodes University, 1988. http://hdl.handle.net/10962/d1001563.
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Union Section of Rustenburg Patinum Mines is situated in the northwestern part of the Bushveld Complex, some twenty kilometres north of the Pilanesberg Alkaline Complex. The mining lease area covers a roughly triangular segment of Lower, Critical and Main Zone rocks, transgressed to the north and south by magnetite-bearing ferrogabbro of the Upper Zone. The Main Zone at Union Section is the focus of this study. The prime source of sample material for the study is the deep exploration borehole SK2, but additional, supplementary samples were collected on surface and underground, as well as from a second surface exploration borehole, SK4. In line with the recommendations of SACS (1980), the top of the Critical Zone, and therefore the base of the Main Zone, is taken to be the top of the Bastard Cyclic Unit. Sharpe (1985) suggested that the succession from the base of the Main is an isotopically separate entity Zone up to the Pyroxenite Marker from the rest of the Bushveld layered succession. This is not strictly true, as there is evidence that more than one parental magma was involved in the formation of this interval. It is, however, true that there are fundamental differences, particularly in isotopic makeup, between the Main Zone rocks below the pyroxenite Marker and those above (the latter having been assigned by Molyneux (1970) to subzone C of the Main Zone). Kruger et al. (1986, in press) suggested that the Pyroxenite Marker marks the base of the Upper Zone, and this convention is adhered to here. The implication of this is that the rocks which formerly constituted subzone C of the Main Zone are now considered part of the Upper Zone. The Main Zone rocks below the pyroxenite Marker were originally subdivided by Molyneux (1970) into two subzones, A and B. The results of the present study indicate that this subdivision is not justified. Instead, eight units have been distinguished in the Main Zone on geochemical, petrological and mineralogical bases. Each of these units is characterized by a coherent set, or progression, of chemical and petrological characteristics. The specific assignment of genetic connotations to these units has been deliberately avoided , at least until further studies of the Main Zone prove this to be justified. The demarcation of the eight units is illustrated in the composite diagram (Fig. 34) in the back pocket of this work, and the reasons for the subdivisions are listed in Table 6 (at the end of chapter 7 of this thesis). Until the late 1970's, it was thought that most layered cumulates formed by crystal settling (Wager and Brown, 1968). More recently, there has been a fundamental conceptual change, and many workers now believe that most cumulate rocks formed by in situ crystallization at the floor and walls of the magma chamber (McBirney and Noyes, 1979, Irvine, 1980a; Campbell, 1987). There is, however, some evidence for the physical separation of phases undergoing cotectic crystallization, particularly in the Upper Critical Zone and lower part of the Main Zone (Eales et al., 1986). This process, which has been alluded to in the past by various authors (Ferguson and Botha, 1963; Vermaak, 1976) involves the flotation of early-formed plagioclase crystals due to their positive bouyancy in tholeiitic liquids. The result is an apparent decoupling of the chemistry of pyroxene and plagioclase, as in unit IV of the Main Zone, where plagioclase becomes more anorthitic upwards, whilst pyroxene becomes more iron-rich. There is some substantial evidence, particularly in reversals in the strontium isotope initial ratio and the orthopyroxene Mg/(Mg+Fe) ratio , for multiple intrusion in the Main Zone. Although the largest and most important magma influx in the Main Zone was a high-R₀ aluminous tholeiite, as suggested by Sharpe (1985), the intrusive history of the Main Zone is believed to be far more complex than Sharpe (op. cit.) suggested. Significantly, there is strong evidence for small influxes of Upper Zone-type (Fe-rich tholeiite) magma in the upper reaches of the Main Zone. These are believed to be precursors to the major influx of Upper Zone-type magma at the pyroxenite Marker (Kruger et al, 1986, in press). The fate of intercumulus liquids in cumulate rocks has recently recieved substantial attention (Sparks et al., 1985; Morse, 1986; Barnes, 1986: Campbell, 1987). It is believed that the migration, or at least redistribution, of intercumulus liquids has played a vital role in modifying fractionation trends in the Main Zone. More importantly, the accumulation of late-stage intercumulus liquids is believed to be responsible for the formation of the Fe-rich ultramafic pegmatite bodies that interrupt the layered cumulates in borehole SK2Adobe Acrobat 9.53 Paper Capture Plug-in
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Koegelenberg, Corne. "Experimental evidence for sulphide magma percolation and evolution : relevant to the chromite bearing reefs of the Bushveld Complex." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20043.
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Thesis (MSc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Pt mineralization within the Bushveld Complex is strikingly focused on the chromitite reefs, despite these horizons being associated with low volumes of base metal sulphide relative to Pt grade. Partitioning of Pt (Dsil/sulp) from silicate magma into immiscible sulphide liquid appears unable to explain Pt concentrations in chromitite horizons, due to the mismatch that exists between very large R factor required and the relevant silicate rock volume. Consequently, in this experimental study we attempt to gain better insight into possible Pt grade enhancement processes that may occur with the Bushveld Complex (BC) sulphide magma. We investigate the wetting properties of sulphide melt relevant to chromite and silicate minerals, as this is a key parameter controlling sulphide liquid percolation through the cumulate pile. Additionally, we have investigated how fractionation of the sulphide liquid from mono-sulphide-solid-solution (Mss) crystals formed within the overlying melanorite might affect sulphide composition and Pt grades within the evolved sulphide melt. Two sets of experiments were conducted: Firstly, at 1 atm to investigate the phase relations between 900OC and 1150OC, within Pt-bearing sulphide magma relevant to the BC; Secondly, at 4 kbar, between 900OC to 1050OC, which investigated the downwards percolation of sulphide magma through several layers of silicate (melanorite) and chromitite. In addition, 1atm experiments were conducted within a chromite dominated chromite-sulphide mixture to test if interaction with chromite affects the sulphide system by ether adding or removing Fe2+. Primary observations are as follows: We found sulphide liquid to be extremely mobile, the median dihedral angles between sulphide melt and the minerals of chromitite and silicate layers are 11O and 33O respectively. This is far below the percolation threshold of 60O for natural geological systems. In silicate layers sulphide liquid forms vertical melt networks promoting percolation. In contrast, the extremely effective wetting of sulphide liquid in chromitites restricts sulphide percolation. Inter-granular capillary forces increase melt retention, thus chromitites serve as a reservoir for sulphide melt. Sulphide liquid preferentially leaches Fe2+ from chromite, increasing the Fe concentration of the sulphide liquid. The reacted chromite rims are enriched in spinel end-member. This addition of Fe2+ to the sulphide magma prompts crystallization Fe-rich Mss, decreasing the S-content of sulphide melt. This lowers Pt solubility and leads to the formation of Pt alloys within the chromitite layer. Eventually, Cu-rich sulphide melt escapes through the bottom of the chromitite layer. These observations appear directly applicable to the mineralized chromitite reefs of the Bushveld complex. We propose that sulphide magma, potentially injected from the mantle with new silicate magma injections, percolated through the silicate cumulate overlying the chromitite and crystallized a significant volume of Fe-Mss. Chromitite layers functioned as traps for percolating, evolved, Cu-, Ni- and Pt-rich sulphide liquids. This is supported by the common phenomenon that chromitites contain higher percentages of Ni, Cu and Pt relative to hanging wall silicate layers. When in contact with chromite, sulphide melt is forced to crystallize Mss as it leaches Fe2+ from the chromite, thereby further lowering the S-content of the melt. This results in precipitation, as Pt alloys, of a large proportion of the Pt dissolved in the sulphide melt. In combination, these processes explain why chromitite reefs in the Bushveld Complex have Pt/S ratios are up to an order of magnitude higher that adjacent melanorite layers.
AFRIKAANSE OPSOMMING: Pt mineralisasie in die Bosveld Kompleks is kenmerkend gefokus op die chromatiet riwwe, alhoewel die riwwe geassosieer is met lae volumes basismetaal sulfiedes relatief tot Pt graad. Verdeling van Pt (Dsil/sulp) vanaf silikaat magma in onmengbare sulfiedvloeistof is klaarblyklik onvoldoende om Pt konsentrasies in chromatiet lae te verduidelik, a.g.v. die wanverhouding wat bestaan tussen ‘n baie groot R-faktor wat benodig word en die relatiewe silikaat rots volumes. Gevolglik, in die eksperimentele studie probeer ons beter insig kry oor moontlike Pt graad verhogingsprosesse wat plaasvind in die BK sulfied magma. Ons ondersoek die benattingseienskappe van sulfied vloeistof relevant tot chromiet- en silikaat minerale, omdat dit die sleutel maatstaf is vir die beheer van sulfied vloeistof deursypeling deur die kumulaat opeenhoping. Addisioneel het ons ook ondersoek hoe die fraksionering van sulfied vloeistof vanaf MSS kristalle, gevorm binne die hangende melanoriet muur, moontlik die sulfied samestelling en Pt graad binne ontwikkelde sulfied smelt kan beïnvloed. Twee stelle van eksperimente is gedoen: Eerstens, by 1 atm om ondersoek in te stel oor fase verwantskappe tussen 900OC en 1150OC, binne ‘n Pt-verrykte sulfied magma samestelling relevant tot die BK; Tweedens, by 4 kbar, tussen 900OC tot 1050OC, wat die afwaartse deursypeling van sulfied magma deur veelvuldige lae van silikaat minerale en chromatiet. Addisionele 1 atm eksperimente is gedoen binne ‘n chromiet gedomineerde chromiet-sulfied mengsel, om te toets of interaksie met chromiet die sulfied sisteem affekteer deur Fe2+ te verwyder of by te dra. Primêre observasies is soos volg: Ons het bevind sulfiedsmelt is uiters mobiel, die mediaan dihedrale hoek tussen sulfiedsmelt en minerale van chromiet en silikaat lae is 11O en 33O onderskydelik. Dit is ver onder die deursypelings drumpel van 60O vir natuurlike geologiese stelsels. In silikaatlae vorm die sulfiedsmelt vertikale netwerke wat deursypeling bevorder. Inteendeel, uiters effektiewe benatting van sulfiedsmelt binne chromatiete vertraag sulfied deusypeling. Tussen kristal kapilêre kragte verhoog smelt retensie, dus dien chromatiete as ‘n opgaarmedium vir sulfiedsmelt. S oorversadigte sulfied vloeistof loogsif Fe2+ vanuit chromiet en veroorsaak ‘n verhoging in Fe-konsentraie. Die gereageerde chromiet buiterante is daarvolgens verryk in Cr-spinêl eind-ledemaat. Die addisionele byvoeging van Fe2+ aan sulfied magma veroorsaak die kristalisasie van Fe-ryke Mss en verlaag dus die S-konsentrasie van die sulfied smelt. Dit verlaag Pt oplosbaarheid en lei tot die formasie van Py allooie binne-in chromatiete. Ten einde, ontsnap Cu-ryke sulfied smelt deur die onderkant van die chromatiet lae. Die observasies is direk van toepassing op die gemineraliseerde chromatiet riwwe van die Bosveld Kompleks. Ons stel voor dat sulfied magma, potensiaal ingespuit vanuit die mantel saam nuwe inspuitings van silikaat magma, deur die hangende silikaat kumulaat bo chromatiet lae deurgesypel het en ‘n betekenisvolle volume Fe-Mss gekristalliseer het. Chromatiet lae het gefunksioneer as lokvalle vir afwaartsbewegende, ontwikkelde, Cu-, Ni-, en Pt-ryke sulfied vloeistowwe. Dit word ondersteun deur die algemene verskynsel dat chromatiete hoër persentasies van Ni, Cu en Pt relatief teenoor die hangende muur silikaat lae het. Wanneer sulfied smelt in kontak is met chromiet, word dit geforseer om Mss te kristalliseer soos Fe2+ geloogsif word, waarvolgens die smelt se S konsentrasie verder verlaag word. Dit veroorsaak die presipitasie, as Pt allooie, van groot proporsies opgeloste Pt vanuit sulfied smelt. Deur die prosesse te kombineer, kan dit moontlik verduidelik word hoekom chromatiet riwwe in die Bosveld Kompleks Pt/S verhoudings veel hoër is as aanrakende melanoriet lae.
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De, Klerk William Johan. "Petrogenesis of the upper critical zone in the Western Bushveld Complex with emphasis on the UG1 Footwall and Bastard units." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005598.
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This study is an account of the stratigraphic sequence, the petrography, mineralogy (microprobe investigations of orthopyroxene, clinopyroxene, olivine and plagioclase feldspar), and whole-rock major- and traceelement geochemistry of the silicate cumulates of the Upper Critical Zone in the western Bushveld Complex. Two parts of the study - an investigation of a 350m column incorporating the MG3 and UGI Footwall Units, and a comparison of two additional Upper Critical Zone profiles with a previously compiled profile between the UGI and Bastard Units - are focused on RPM Union Section in the northwestern sector of the Complex. The third part is a detailed vertical and lateral investigation of the Bastard Unit at the top of the Critical Zone, which draws on sampling and data compilation from seventeen profiles in the western limb of the Complex. The MG3 Unit (45m) is made up of a lower chromitite layer overlain by a norite-pyroxenite-anorthosite sequence while the UGlFW Unit (295m) is composed of a related series of lower chromitite layers (MG4) overlain by a pyroxenite-norite-anorthosite sequence capped by the UGI chromitite layer. These mafic cumulates display a distinctive pattern of oscillating cryptic variation in whole-rock Mg/(Mg+Fe), FeO/Ti0₂, Cr/Co and Ni/V ratios through the sequence. Sympathetic oscillations are recorded for compositions of orthopyroxene and plagioclase feldspar and eight subcycles are recognised through the UGlFW Unit. The entire sequence is characterised by the presence of small, spheroidal, embayed and irregularly shaped plagioclase grains which are poikilitically enclosed in cumulus orthopyroxene grains of both pyroxenites and norites. This texture is indicative of partial resorption of pre-existing feldspar primocrysts within the melt prior to their being incorporated into the host orthopyroxene grains. Textural, geochemical and isotopic data suggest that this sequence was built up by periodic additions of fresh, relatively primitive liquid into fractionated resident liquid, and subsequent mixing within the magma chamber. The Bastard Unit sequence, described in Chapter 4, is the last and most complete cyclic unit (c. 60m) of the Critical Zone, and its upper contact defines the boundary between the Critical and Main Zones of the Complex. This Unit can conveniently be sub-divided into a lower part, where orthopyroxene occurs as a cumulus phase, and the upper part which is composed entirely of anorthosite (Giant Mottled Anorthosite). The basal part of the Unit (≤ 18m) comprises a thin chromitite layer < O.5cm) overlain by a pyroxenite-melanorite-norite-leuconorite sequence. The basal pyroxenite is orthocumulate in character and rapidly gives way to norites and leuconorites. A distinct threefold subdivision emerges within the Giant Mottled Anorthosite which is predominantly an adcumulate which becomes orthocumulate in character at its top. Apart from minor deviations in thicknesses these lithologies are recorded over the entire strike-length covered in this study. Profiles of cryptic variation are compiled for orthopyroxene, plagioclase and whole-rock data and show that the Bastard Unit displays a characteristic pattern which is maintained throughout the western Bushveld Complex. A minor yet distinctive reversal in cryptic variation is revealed at a level which is stratigraphically variable within the lower Giant Mottled Anorthosite, and results in a double cuspate pattern. A remarkable feature of the basal Bastard pyroxenites is that although the modal proportion of mafic to felsic constituents varies systematically away from the northwestern sector, the Mg/(Mg+Fe) ratio of orthopyroxenes remains constant at 0.804 over a lateral strike distance of 171km. Within the upper part of the Unit the orthopyroxene is markedly Fe-rich and it is here that inverted primary pigeonite appears for the first time as a cumulus phase. In addition, K-feldspar, oscillatory zoned plagioclase grains and high levels of incompatible trace elements are noted at this level. On the basis of the data presented it is concluded that the Bastard Unit represents the crystallisation of a final, relatively large influx of hotter primitive liquid, with upper Critical Zone affinities, and subsequent mixing with a column of cooler (less dense) supernatant liquid which had in part hybridized with the overlying Main Zone magma. It is hypothesised that this new liquid was emplaced as a basal flow beneath supernatant liquid and that it initiated the deposition of mafic cumulates at its base. The supernatant liquid is interpreted as representing the fractionated residuum produced by crystallisation of earlier cyclic units, with plagioclase on the liquidus, and that it contained an abundance of small plagioclase primocrysts in suspension. Development of the Unit can be viewed as a two-stage process. In the lower half of the unit, chemical and physical parameters typical of the new magma dominated the crystallisation process, and resulted in cumulates very similar to other relatively complete Upper Critical Zone units. In the upper, leucocratic sequence, above a minor reversal, crystallisation was from a liquid which was the product of mixing of a minor pulse of primitive liquid with the reservoir of hybridized supernatant liquid. Although the Bastard Unit is not continuous around the entire Western limb of the Complex, it is concluded that it developed in a single, or connected, magma chamber and that its irruptive feeder zone was located in the proximal northwestern facies of the Complex.
Books on the topic "Structural bushveld complex south africa"
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Andreoni, Antonio, Pamela Mondliwa, Simon Roberts, and Fiona Tregenna, eds. Structural Transformation in South Africa. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192894311.001.0001.
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Taking South Africa as an important case study of the challenges of structural transformation, the book offers a new micro-meso level framework and evidence linking country-specific and global dynamics of change, with a focus on the current challenges and opportunities faced by middle-income countries. Detailed analyses of industry groupings and interests in South Africa reveal the complex set of interlocking country-specific factors which have hampered structural transformation over several decades, but also the emerging productive areas and opportunities for structural change. The structural transformation trajectory of South Africa presents a unique country case, given its industrial structure, concentration, and highly internationalized economy, as well as the objective of black economic empowerment. The book links these micro-meso dynamics to the global forces driving economic, institutional, and social change. These include digital industrialization, global value-chain consolidation, financialization, and environmental and other sustainability challenges which are reshaping structural transformation dynamics across middle-income countries like South Africa. While these new drivers of change are disrupting existing industries and interests in some areas, in others they are reinforcing existing trends and configurations of power. The book analyses the ways in which both the domestic and global drivers of structural transformation shape—and, in some cases, are shaped by—a country’s political settlement and its evolution. By focusing on the political economy of structural transformation, the book disentangles the specific dynamics underlying the South African experience of the middle-income country conundrum. In so doing, it brings to light the broader challenges faced by similar countries in achieving structural transformation via industrial policies.
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Cameron, Gregory Hugh *. A geochemical investigation into the origin of the upper critical zone of the eastern Bushveld complex, South Africa. 1988.
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Wood, Geoffrey. Employee Participation in Developing and Emerging Countries. Edited by Adrian Wilkinson, Paul J. Gollan, Mick Marchington, and David Lewin. Oxford University Press, 2010. http://dx.doi.org/10.1093/oxfordhb/9780199207268.003.0023.
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Work and employment relations vary not only according to individual strategic choices by managers, and actions and responses by employees, but also by the social and economic context. Development is a complex and multifaceted process of structural transformation, including economic and social changes. While a common distinction is often drawn between nations who have attained a degree of socio-economic development characterized by certain levels of income, productivity, investment, formal employment, technological deployment and a range of human capital indicators, the latter category is an extremely broad one in itself. It may encompass ‘emerging market’ nations such as Brazil and South Africa, and nations where economic activity centres around the production of unprocessed or semi-processed primary commodities, with only limited downstream industrial development. This article primarily focuses on this second category, although some attention is also devoted to the case of ‘emerging markets’.
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Bloxham, Donald, and A. Dirk Moses, eds. The Oxford Handbook of Genocide Studies. Oxford University Press, 2012. http://dx.doi.org/10.1093/oxfordhb/9780199232116.001.0001.
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The Oxford Handbook of Genocide Studies subjects both genocide and the discipline it has spawned to systematic, in-depth investigation. Genocide has scarred human societies since Antiquity. In the modern era, genocide has been a global phenomenon: from massacres in colonial America, Africa, and Australia to the Holocaust of European Jewry and mass death in Maoist China. In recent years, the discipline of genocide studies has developed to offer analysis and comprehension. Thirty-four articles chart genocide through the ages by taking regional, thematic, and disciplinary-specific approaches. Articles examine secessionist and political genocides in modern Asia. Others treat the violent dynamics of European colonialism in Africa, the complex ethnic geography of the Great Lakes region, and the structural instability of the continent's northern horn. South and North America receive detailed coverage, as do the Ottoman Empire, Nazi-occupied Europe, and post-communist Eastern Europe. Sustained attention is paid to themes like gender, memory, the state, culture, ethnic cleansing, military intervention, the United Nations, and prosecutions.
Book chapters on the topic "Structural bushveld complex south africa"
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Cawthorn, R. Grant. "The Bushveld Complex, South Africa." In Springer Geology, 517–87. Dordrecht: Springer Netherlands, 2015. http://dx.doi.org/10.1007/978-94-017-9652-1_12.
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Scoon, Roger N. "Skaergaard Intrusion, Greenland and Eastern Bushveld Complex, South Africa." In The Geotraveller, 353–74. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-54693-9_17.
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Viljoen, Fanus, Mike Knoper, Hariharan Rajesh, Derek Rose, and Tiaan Greeff. "Application of a Field Emission Mineral Liberation Analyser to the in Situ Study of Platinum-Group Element Mineralisation in the Merensky Reef of the Bushveld Complex, South Africa." In Proceedings of the 10th International Congress for Applied Mineralogy (ICAM), 757–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-27682-8_91.
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van Aswegen, G., D. Strydom, W. P. Colliston, H. E. Praekelt, A. E. Schoch, H. J. Blignault, B. J. V. Botha, and S. W. van der Merwe. "The structural-stratigraphic development of part of the Namaqua metamorphic complex, South Africa—An example of Proterozoic major thrust tectonics." In Proterozic Lithospheric Evolution, 207–16. Washington, D. C.: American Geophysical Union, 1987. http://dx.doi.org/10.1029/gd017p0207.
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Longridge, Luke, Roger L. Gibson, and Paul A. M. Nex. "Structural controls on melt segregation and migration related to the formation of the diapiric Schwerin Fold in the contact aureole of the Bushveld Complex, South Africa." In Sixth Hutton Symposium on The Origin of Granites and Related Rocks: Proceedings of a Symposium held in Stellenbosch, South Africa, 2- 6 July 2007. Geological Society of America, 2010. http://dx.doi.org/10.1130/2010.2472(05).
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Cramer, Christopher, and Shingie Chisoro-Dube. "The Industrialization of Freshness and Structural Transformation in South African Fruit Exports." In Structural Transformation in South Africa, 120–42. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192894311.003.0006.
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Economists have historically tended to identify industrial processes and technological sophistication with manufacturing, and not with agriculture. This chapter illustrates the substantial scope to apply sophisticated technologies and industrial processes necessary to shift resources out of low-productivity activities into higher-productivity activities, i.e. to generate ‘structural change’ in the production of ‘fresh’ agricultural export production. Leveraging the concept of the ‘industrialization of freshness’, this chapter uses evidence from South Africa’s fresh-fruit industry to show how advances in technology have been a key mechanism through which structural transformation towards high-value fruit has occurred in the industry. The chapter also shows how building capabilities to harness technological changes is necessary for increased market access through enabling producers to keep up with escalating quality standards; to comply with the many—and complex—sanitary and phytosanitary requirements; and to adapt to climate change. However, despite evidence of dynamism in fruit production, effective structural transformation in the South African fruit industry has been limited by widespread underinvestment in infrastructure—ports, rural internet capacity, water infrastructure, and technical capacity.
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Andreoni, Antonio, Pamela Mondliwa, Simon Roberts, and Fiona Tregenna. "Framing Structural Transformation in South Africa and Beyond." In Structural Transformation in South Africa, 1–27. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780192894311.003.0001.
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Structural transformation is a complex, long-term historical process entailing both structural change in the sectoral composition of an economy, as well as broader societal changes in the productive organizations, institutions, and political economy of a country. With a focus on South Africa as a middle-income country, this chapter advances a holistic and integrated perspective on the nature and dynamics of structural transformation and highlights a specific set of interlocking critical factors and dimensions. These are: the processes of learning and productive capabilities development and accumulation; technological change—digitalization, specifically—and its relationship with sustainability; power dynamics along global value chains (GVCs) and their relation to inequality; and finally, the political economy of development and the role of the state. Over the course of its democratic history, since 1994, South Africa has not undergone sustained and thoroughgoing structural transformation. Despite some areas of partial success, there has been premature deindustrialization, lack of sufficient development of the local production system alongside integration into GVCs, and persistent cross-cutting challenges of inclusiveness and sustainability. Here it is argued that the holistic and integrated framework developed by the authors can help in developing a policy approach towards effective and feasible packages of industrial policies for structural transformation.
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Robb, L. J., L. A. Freeman, and R. A. Armstrong. "Nature and longevity of hydrothermal fluid flow and mineralisation in granites of the Bushveld Complex, South Africa." In The Fourth Hutton Symposium on the Origin of Granites and Related Rocks. Geological Society of America, 2000. http://dx.doi.org/10.1130/0-8137-2350-7.269.
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Orme, Antony R. "The Tectonic Framework of South America." In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0008.
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Tectonism is the science of Earth movements and the rocks and structures involved therein. These movements build the structural framework that supports the stage on which surface processes, plants, animals and, most recently, people pursue their various roles under an atmospheric canopy. An appreciation of this tectonic framework is thus a desirable starting point for understanding the physical geography of South America, from its roots in the distant past through the many and varied changes that have shaped the landscapes visible today. Tectonic science recognizes that Earth’s lithosphere comprises rocks of varying density that mobilize as relatively rigid plates, some continental in origin, some oceanic, and some, like the South American plate, amalgams of both continental and oceanic rocks. These plates shift in response to deep-seated forces, such as convection in the upper mantle, and crustal forces involving push and pull mechanics between plates. Crustal motions, augmented by magmatism, erosion, and deposition, in turn generate complex three-dimensional patterns. Although plate architecture has changed over geologic time, Earth’s lithosphere is presently organized into seven major plates, including the South American plate, and numerous smaller plates and slivers. The crustal mobility implicit in plate tectonics often focuses more attention on plate margins than on plate interiors. In this respect, it is usual to distinguish between passive margins, where plates are rifting and diverging, and active margins, where plates are either converging or shearing laterally alongside one another. At passive or divergent margins, such as the present eastern margin of the South American plate, severe crustal deformation is rare but crustal flexuring (epeirogeny), faulting, and volcanism occur as plates shift away from spreading centers, such as the Mid-Atlantic Ridge, where new crust is forming. Despite this lack of severe postrift deformation, however, passive margins commonly involve the separation of highly deformed rocks and structures that were involved in the earlier assembly of continental plates, as shown by similar structural legacies in the facing continental margins of eastern South America and western Africa. At active convergent margins, mountain building (orogeny) commonly results from subduction of oceanic plates, collision of continental plates, or accretion of displaced terranes.
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Manzi, Shalene, Roger L. Gibson, and Asinne Tshibubudze. "Dynamics of collapse of an impact central uplift: Evidence from folds and faults in the collar of the Vredefort Dome, South Africa." In Large Meteorite Impacts and Planetary Evolution VI. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2550(27).
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ABSTRACT Structural analysis of overturned metasedimentary strata of the lower Witwatersrand Supergroup in the inner collar of the Vredefort Dome reveals the presence of tangential folds and faults associated with the 2.02 Ga impact. The folds are distinct from previously identified subradially oriented, vertical to plunging-inclined, gentle folds that are interpreted as the products of convergent flow (constriction) during the initial stages of central uplift formation. The tangential folds comprise disharmonic, open, asymmetric, horizontal to plunging-inclined anticline-syncline pairs with centripetally dipping axial planes and right-way-up intermediate limbs. They display centripetal-down vergence (anticline radially outward of the syncline) that is consistent with steep inward-directed shear of the overturned strata. We attribute this kinematic pattern to subvertical collapse of the Vredefort central uplift during the latter stages of crater modification. The folds are cut by pseudotachylite-bearing steep to vertical tangential faults that display center-down slip of <10 m up to ~150 m. Both the tangential folds and the faults suggest that the large-scale overturning of strata related to outward collapse of the Vredefort central uplift was accompanied by a component of inward-directed collapse via layer-parallel shearing and folding, followed by faulting. Subradially oriented faults with conjugate strike separations of 1–2 km in the NNE collar of the dome suggest penecontemporaneous tangential extension of the inner collar rocks. This evidence indicates that second-order structures in the metasedimentary collar of the Vredefort Dome preserve a complex, multistage record of evolving strain associated with both initial convergent and upward flow (constriction) related to central uplift rise and later divergent and downward flow (flattening) linked to its collapse, and that centripetally directed collapse features may be important components of the structural inventory of very large central uplifts.
Conference papers on the topic "Structural bushveld complex south africa"
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Letts, S., T. H. Torsvik, S. J. Webb, and L. D. Ashwal. "Palaeomagnetism of Mafic Dykes from the Eastern Bushveld Complex (South Africa)." In 8th SAGA Biennial Technical Meeting and Exhibition. European Association of Geoscientists & Engineers, 2003. http://dx.doi.org/10.3997/2214-4609-pdb.144.18.
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Sepato, O. "Wavelet Analysis of Density Data from the Bushveld Complex, South Africa." In 75th EAGE Conference and Exhibition incorporating SPE EUROPEC 2013. Netherlands: EAGE Publications BV, 2013. http://dx.doi.org/10.3997/2214-4609.20131064.
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Webb*, Susan J., Lewis D. Ashwal, Robert Trumbull, and Ilya Veksler. "ICDP Deep drilling and geophysical exploration of the Bushveld Complex, South Africa." In SEG Technical Program Expanded Abstracts 2014. Society of Exploration Geophysicists, 2014. http://dx.doi.org/10.1190/segam2014-1673.1.
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Manzi, M., A. Malehmir, and R. J. Durrheim. "3D Reflection Seismics for Deep Platinum Exploration in the Bushveld Complex, South Africa." In 2nd Conference on Geophysics for Mineral Exploration and Mining. Netherlands: EAGE Publications BV, 2018. http://dx.doi.org/10.3997/2214-4609.201802751.
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Manzi*, Musa, Raymond Durrheim, and Susan Webb. "3D seismic attributes for platinum exploration and mine planning in the Bushveld Complex (South Africa)." In International Geophysical Conference, Qingdao, China, 17-20 April 2017. Society of Exploration Geophysicists and Chinese Petroleum Society, 2017. http://dx.doi.org/10.1190/igc2017-169.
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Manzi, M., E. J. Hunt, and R. J. Durrheim. "3D Seismic Attributes to Enhance the Detection of Potholes and Subtle Faults, Bushveld Complex (South Africa)." In Fourth EAGE Exploration Workshop. Netherlands: EAGE Publications BV, 2017. http://dx.doi.org/10.3997/2214-4609.201700228.
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Boudreau, Alan E., Erin Benson, and James A. D. Connolly. "THE HYDROTHERMAL SYSTEM OF THE BUSHVELD COMPLEX, SOUTH AFRICA - AN ANALOG FOR SUBDUCTION ZONE HYDROTHERMAL SYSTEMS." In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-334325.
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Sehoole, L., M. Manzi, and S. Zhang. "Application of 3D seismic to Enhance Mapping of Potholes in the Western Bushveld Complex, South Africa." In 80th EAGE Conference and Exhibition 2018. Netherlands: EAGE Publications BV, 2018. http://dx.doi.org/10.3997/2214-4609.201801715.
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Webb, Susan, Grant Cawthorn, Lew Ashwal, Shawn Letts, and Trond Torsvik. "Size does matter: Towards a consistent 3D gravity and magnetic model of the Bushveld Complex, South Africa." In SEG Technical Program Expanded Abstracts 2006. Society of Exploration Geophysicists, 2006. http://dx.doi.org/10.1190/1.2370395.
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Dyan, Siyasanga, Steve Prevec, and Nicolas Tonnelier. "MODELLING THE ROLE OF CARBONATE ASSIMILATION ON THE STABILITY OF SPINELS: A FOCUS ON FLATREEF CHROMITES, BUSHVELD COMPLEX, SOUTH AFRICA." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-355594.
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