Journal articles: 'Geology structural south africa'

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McCourt, Stephen, and Dirk van Reenen. "Structural geology and tectonic setting of the Sutherland Greenstone Belt, Kaapvaal Craton, South Africa." Precambrian Research 55, no. 1-4 (March 1992): 93–110. http://dx.doi.org/10.1016/0301-9268(92)90017-i.

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Beach, Alastair, and Roric Smith. "Structural geometry and development of the Witwatersrand Basin, South Africa." Geological Society, London, Special Publications 272, no. 1 (2007): 533–42. http://dx.doi.org/10.1144/gsl.sp.2007.272.01.27.

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Smit, C. A., C. Roering, and D. D. van Reenen. "The structural framework of the southern margin of the Limpopo Belt, South Africa." Precambrian Research 55, no. 1-4 (March 1992): 51–67. http://dx.doi.org/10.1016/0301-9268(92)90014-f.

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Basson, I. J. "Structural overview of selected Group II kimberlite dyke arrays in South Africa: implications for kimberlite emplacement mechanisms." South African Journal of Geology 106, no. 4 (December 1, 2003): 375–94. http://dx.doi.org/10.2113/106.4.375.

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Heine, C., J. Zoethout, and R. D. Müller. "Kinematics of the South Atlantic rift." Solid Earth 4, no. 2 (August 1, 2013): 215–53. http://dx.doi.org/10.5194/se-4-215-2013.

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Abstract. The South Atlantic rift basin evolved as a branch of a large Jurassic–Cretaceous intraplate rift zone between the African and South American plates during the final break-up of western Gondwana. While the relative motions between South America and Africa for post-break-up times are well resolved, many issues pertaining to the fit reconstruction and particularly the relation between kinematics and lithosphere dynamics during pre-break-up remain unclear in currently published plate models. We have compiled and assimilated data from these intraplated rifts and constructed a revised plate kinematic model for the pre-break-up evolution of the South Atlantic. Based on structural restoration of the conjugate South Atlantic margins and intracontinental rift basins in Africa and South America, we achieve a tight-fit reconstruction which eliminates the need for previously inferred large intracontinental shear zones, in particular in Patagonian South America. By quantitatively accounting for crustal deformation in the Central and West African Rift Zones, we have been able to indirectly construct the kinematic history of the pre-break-up evolution of the conjugate west African–Brazilian margins. Our model suggests a causal link between changes in extension direction and velocity during continental extension and the generation of marginal structures such as the enigmatic pre-salt sag basin and the São Paulo High. We model an initial E–W-directed extension between South America and Africa (fixed in present-day position) at very low extensional velocities from 140 Ma until late Hauterivian times (≈126 Ma) when rift activity along in the equatorial Atlantic domain started to increase significantly. During this initial ≈14 Myr-long stretching episode the pre-salt basin width on the conjugate Brazilian and west African margins is generated. An intermediate stage between ≈126 Ma and base Aptian is characterised by strain localisation, rapid lithospheric weakening in the equatorial Atlantic domain, resulting in both progressively increasing extensional velocities as well as a significant rotation of the extension direction to NE–SW. From base Aptian onwards diachronous lithospheric break-up occurred along the central South Atlantic rift, first in the Sergipe–Alagoas/Rio Muni margin segment in the northernmost South Atlantic. Final break-up between South America and Africa occurred in the conjugate Santos–Benguela margin segment at around 113 Ma and in the equatorial Atlantic domain between the Ghanaian Ridge and the Piauí-Ceará margin at 103 Ma. We conclude that such a multi-velocity, multi-directional rift history exerts primary control on the evolution of these conjugate passive-margin systems and can explain the first-order tectonic structures along the South Atlantic and possibly other passive margins.

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Anhaeusser, C. R. "The geology and tectonic evolution of the northwest part of the Barberton Greenstone Belt, South Africa: A review." South African Journal of Geology 122, no. 4 (December 1, 2019): 421–54. http://dx.doi.org/10.25131/sajg.122.0033.

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AbstractFormations on the northwestern flank of the Barberton Greenstone Belt have hosted over 85% of all the gold recovered from the ca. 3550 to 3000 Ma Barberton Supergroup since early discoveries in 1872. This sector of the greenstone belt also happens to coincide with a complex tectonic architecture resulting from successive stages of folding and faulting superimposed onto a complex lithostratigraphy. Of particular importance has been the influence of two diapiric granitoid intrusions that caused added structural complexity following their emplacement ca. 3227 to 3250 Ma. Of these the larger Kaap Valley Pluton invaded the area north of present day Barberton town causing the separation of the greenstones into a northern arm (Jamestown Schist Belt) and a southern sector which remained attached to the main greenstone belt (Moodies Hills). The ballooning pluton produced vertical as well as horizontal flattening stresses, the latter reactivating earlier high-angle faults and resulting in subhorizontal strike-slip movements, particularly along the Barbrook Fault Zone, which acted as a right-lateral strike-slip fault. Formations north of this fault were buckled, following progressive deformation in the region known as the Sheba Hills, into major synclinal folds (Eureka and Ulundi Synclines) with folded axial planes that dip steeply to the south, southeast or east. The second granitoid intrusion (Stentor Pluton), which has been extensively modified by subsequent magmatic events, caused significant flattening of greenstone belt rocks in the northeastern part of the Barberton Greenstone Belt (Three Sisters region) as well as in other areas rimming the granitic body. Combined, the two plutons produced a wide range of interference and reactivated structures particularly affecting a triangular region extending from the Jamestown Schist Belt into the area occupied by the New Consort Gold Mine and areas to the east. This paper attempts to outline, in the simplest manner, the geological and structural evolution of the main gold-producing region of the Barberton Goldfield. The principal aim is therefore to highlight the structural influence of the diapiric plutonism and the manner in which the plutons contributed significantly to the horizontal reactivation of pre-existing regional faults, which in turn, resulted in the progressive deformation of a heterogeneous lithological terrane.

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Leprêtre, Rémi, Dominique Frizon de Lamotte, Violaine Combier, Oriol Gimeno-Vives, Geoffroy Mohn, and Rémi Eschard. "The Tell-Rif orogenic system (Morocco, Algeria, Tunisia) and the structural heritage of the southern Tethys margin." BSGF - Earth Sciences Bulletin 189, no. 2 (2018): 10. http://dx.doi.org/10.1051/bsgf/2018009.

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The Tell-Rif (Tell in Algeria and Tunisia; Rif in Morocco) is the orogenic system fringing to the south the West Mediterranean basins. This system comprises three major tectonic-palaeogeographic zones from north to south: (1) the internal zones (AlKaPeCa for Alboran, Kabylies, Peloritan, Calabria) originating from the former northern European margin of the Maghrebian Tethys, (2) the “Flyschs zone” regarded as the former cover of the oceanic domain and (3) the external zones, forming the former southern Maghrebian Tethys margin more or less inverted. The Tell-Rif is interpreted as the direct result of the progressive closure of the Maghrebian Tethys until the collision between AlKaPeCa and Africa and, subsequently, the propagation of the deformation within Africa. This gives a consistent explanation for the offshore Neogene geodynamics and most authors share this simple scenario. Nevertheless, the current geodynamic models do not completely integrate the Tell-Rif geology. Based on the analysis of surface and sub-surface data, we propose a reappraisal of its present-day geometry in terms of geodynamic evolution. We highlight its non-cylindrical nature resulting from both the Mesozoic inheritance and the conditions of the tectonic inversion. During the Early Jurassic, we emphasize the development of NE-SW basins preceding the establishment of an E-W transform corridor connecting the Central Atlantic Ocean with the Ligurian Tethys. The Maghrebian Tethys developed just after, as the result of the Late Jurassic-Early Cretaceous left-lateral spreading between Africa and Iberia. By the Late Cretaceous, the occurrence of several tectonic events is related to the progressive convergence convergence between the two continents. A major pre-Oligocene (pre-35 Ma) compressional event is recorded in the Tell-Rif system. The existence of HP-LT metamorphic rocks associated with fragments of mantle in the External Metamorphic Massifs of the Eastern Rif and Western Tell shows that, at that time, the western part of the North-African margin was involved in a subduction below a deep basin belonging to the Maghrebian Tethys. At the same time, the closure of the West Ligurian Tethys through east-verging subduction led to a shift of the subduction, which jumped to the other side of AlKaPeCa involving both East Ligurian and Maghrebian Tethys. Slab rollback led to the development of the Oligo-Miocene back-arc basins of the West-Mediterranean, reworking the previous West Ligurian Tethys suture. The docking of AlKaPeCa against Africa occurred during the Late Burdigalian (17 Ma). Subsequently, the slab tearing triggered westward and eastward lateral movements that are responsible for the formation of the Gibraltar and Tyrrhenian Arcs respectively. The exhumation of the External Metamorphic Massifs occurred through tectonic underplating during the westward translation of the Alboran Domain. It resulted in the formation of both foredeep and wedge-top basins younger and younger westward. The lack of these elements in the eastern part of the systems signs a different evolution dominated by frontal accretion. In the discussion, we precisely address the origin of the non-cylindrical behavior of the orogenic system and question the mechanisms explaining at large scale the phases of coupling/uncoupling between the major plates.

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Paton, Douglas A., David I. M. Macdonald, and John R. Underhill. "Applicability of thin or thick skinned structural models in a region of multiple inversion episodes; southern South Africa." Journal of Structural Geology 28, no. 11 (November 2006): 1933–47. http://dx.doi.org/10.1016/j.jsg.2006.07.002.

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Paton, Douglas A., and John R. Underhill. "Role of crustal anisotropy in modifying the structural and sedimentological evolution of extensional basins: the Gamtoos Basin, South Africa." Basin Research 16, no. 3 (September 2004): 339–59. http://dx.doi.org/10.1111/j.1365-2117.2004.00237.x.

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Manjoro, Munyaradzi. "Structural control of fluvial drainage in the western domain of the Cape Fold Belt, South Africa." Journal of African Earth Sciences 101 (January 2015): 350–59. http://dx.doi.org/10.1016/j.jafrearsci.2014.10.001.

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Basson, I. J., M. K. Watkeys, and D. Phillips. "Structural evolution and tectonic context of the Mfongosi Group, Natal thrust front, Tugela terrane, South Africa." Journal of African Earth Sciences 43, no. 4 (November 2005): 415–32. http://dx.doi.org/10.1016/j.jafrearsci.2005.09.003.

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Basson, I. J., S. A. J. Thomas, B. Stoch, C. J. Anthonissen, M.-J. McCall, J. Britz, S. Macgregor, et al. "The structural setting of mineralisation at Kolomela Mine, Northern Cape, South Africa, based on fully-constrained, implicit 3D modelling." Ore Geology Reviews 95 (April 2018): 306–24. http://dx.doi.org/10.1016/j.oregeorev.2018.02.032.

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Milner, Simon C., Anton P. Le Roex, and Ronald T. Watkins. "Rb-Sr age determinations of rocks from the Okenyenya igneous complex, northwestern Namibia." Geological Magazine 130, no. 3 (May 1993): 335–43. http://dx.doi.org/10.1017/s001675680002001x.

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AbstractThe Okenyenya igneous complex is one of a suite of intrusions which define a prominent northeast-trending linear feature in Damaraland, northwestern Namibia. Precise Rb–Sr internal isochron ages range from 128.6 ± 1 to 123.4 ± 1.4 Ma for the major phases of intrusion identified within the complex. The tholeiitic gabbros forming the outer rings of the complex, and the later alkali gabbros which form the central hills, cannot be distinguished in terms of Rb–Sr ages, although field relations clearly indicate the younger age of the latter. The intrusionsof nepheline-syenite and essexite comprising the mountain of Okenyenya Bergon the northern edge of the complex give ages of 123.4 ± 1.4 and 126.3 ± 1 Ma, respectively, and form the final major phase of intrusion. The ages obtained for early and late intrusive phases define a minimum magmatic ‘life-span’ of approximately 5 Ma for the complex. The determined age of the Okenyenya igneous complex (129–123 Ma), when taken together with the few reliable published ages for other Damaraland complexes (130–134 Ma), suggests that these sub-volcanic complexes were emplaced contemporaneously with the widespread Etendeka volcanics (˜ 130 Ma), and relate to magmatism associated with the breakup of southern Africa and South America with the opening of the South Atlantic Ocean. The linear distributionof intrusions in Damaraland is interpreted to be due to magmatism resultingfrom the upwelling Tristan plume being focused along a structural discontinuity between the Pan-African, Damaran terrain to the south, and Proterozoiccratonic basement to the north.

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Abu Sharib, A. S. A. A., J. Reinhardt, and S. McCourt. "Structural diversity within a thrust complex reflecting progressive overprinting during a protracted orogenic process of terrane accretion, Natal belt, South Africa." Journal of Structural Geology 142 (January 2021): 104231. http://dx.doi.org/10.1016/j.jsg.2020.104231.

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ZEH, ARMIN, REINER KLEMD, and JAY M. BARTON. "Petrological evolution in the roof of the high-grade metamorphic Central Zone of the Limpopo Belt, South Africa." Geological Magazine 142, no. 3 (May 2005): 229–40. http://dx.doi.org/10.1017/s001675680500052x.

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In this study we present new petrological results from the Endora Klippe in the Central Zone of the Limpopo Belt, which may result from horizontal tectonics during the Proterozoic at c. 2.0Ga. Microstructures, assemblages and garnet zonation patterns observed in metapelitic rocks provide evidence that the Endora Klippe rocks underwent a contemporaneous pressure–temperature increase from c. 600°C/5kbar to 650°C/6.5kbar. This is inferred by the use of conventional geothermobarometry and interpretations based on quantitative phase diagrams in the system MnO–(TiO2)–(CaO)–(Na2O)–K2O–MgO–Al2O3–SiO2–H2O. Thus, the petrological results indicate that this part of the Central Zone only underwent a medium-grade metamorphic overprint during a single orogenic event and was never affected by granulite-facies metamorphism, as reported from other parts of the Limpopo Belt. The inferred P–T path, in combination with previous structural and petrological results, leads to the conclusion that the area surrounding the Endora Klippe forms the roof zone of the c. 2.0Ga old granulite-facies rocks forming wide parts of the Limpopo Central Zone.

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Lowe, Donald R., Gary R. Byerly, Barbara L. Ransom, and Bruce W. Nocita. "Stratigraphic and sedimentological evidence bearing on structural repetition in early Archean rocks of the Barberton greenstone belt, South Africa." Precambrian Research 27, no. 1-3 (January 1985): 165–86. http://dx.doi.org/10.1016/0301-9268(85)90011-7.

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Neumann, Ilka, Karim Sami, and Ilka Neumann. "Structural influence on plume migration from a tailings dam in the West Rand, Republic of South Africa." Geological Society, London, Special Publications 198, no. 1 (2002): 337–46. http://dx.doi.org/10.1144/gsl.sp.2002.198.01.23.

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Oloo, Simon, Rob Lindsay, and Sam Mothilal. "Otta Seals and Gravseals as Low-Cost Surfacing Alternatives for Low-Volume Roads: Experiences in South Africa." Transportation Research Record: Journal of the Transportation Research Board 1819, no. 1 (January 2003): 338–42. http://dx.doi.org/10.3141/1819b-43.

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The geology of the northeastern part of the province of KwaZulu–Natal, South Africa, is predominantly alluvial with vast deposits of sands. Suitable gravel sources are hard to come by, which results in high graveling and regraveling costs brought about by long haul distances and accelerated gravel loss. Most gravel roads carry fewer than 500 vehicles per day of which less than 10% are heavy vehicles. The high cost of regraveling has led to consideration of upgrading such roads to surfaced standard, even though traffic volumes do not justify upgrading. Traditional chip seals are expensive and cannot be economically justified on roads that carry fewer than 500 vehicles per day. The KwaZulu–Natal Department of Transport is actively involved in efforts to identify cost-effective alternative surfacing products for low-volume roads. Field trials were conducted with Otta seals and Gravseals, which have been used successfully in other countries, as low-cost surfacing products for low-volume roads. The Otta seal is formed by placing graded aggregates on a relatively thick film of soft binder that, because of traffic and rolling, works its way through the aggregates. Gravseal consists of a special semipriming rubberized binder that is covered by a graded aggregate. Both Otta seals and Gravseals provide relatively flexible bituminous surfaces suitable for low-volume roads. Cost savings are derived mainly from the broad aggregate specifications, which allow for the use of marginal materials.

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Van Niekerk, Daniel, Ronald J. Pugmire, Mark S. Solum, Paul C. Painter, and Jonathan P. Mathews. "Structural characterization of vitrinite-rich and inertinite-rich Permian-aged South African bituminous coals." International Journal of Coal Geology 76, no. 4 (December 2008): 290–300. http://dx.doi.org/10.1016/j.coal.2008.08.014.

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Alchin, D. J., and W. J. Botha. "The structural/stratigraphic development of the Sishen South (Welgevonden) iron ore deposit, South Africa, as deduced from ground gravity data modelling." Applied Earth Science 115, no. 4 (December 2006): 174–86. http://dx.doi.org/10.1179/174327506x138940.

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Nkosi, Nomqhele Z., Musa S. D. Manzi, Oleg Brovko, and Raymond J. Durrheim. "3D seismic attributes for structural mapping and enhancement of deep gold mining: a case study from the West Wits Line goldfields, South Africa." Exploration Geophysics 49, no. 3 (June 2018): 345–62. http://dx.doi.org/10.1071/eg16058.

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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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DZIGGEL, A., S. KNIPFER, A. F. M. KISTERS, and F. M. MEYER. "P-T and structural evolution during exhumation of high-T, medium-P basement rocks in the Barberton Mountain Land, South Africa." Journal of Metamorphic Geology 24, no. 7 (July 24, 2006): 535–51. http://dx.doi.org/10.1111/j.1525-1314.2006.00653.x.

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Reimann, S., C. E. Heubeck, P. Fugmann, D. J. Janse van Rensburg, A. Zametzer, S. H. Serre, and T. B. Thomsen. "Syndepositional hydrothermalism selectively preserves records of one of the earliest benthic ecosystems, Moodies Group (3.22 Ga), Barberton Greenstone Belt, South Africa." South African Journal of Geology 124, no. 1 (March 1, 2021): 253–78. http://dx.doi.org/10.25131/sajg.124.0012.

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Abstract The ~3.22 Ga Moodies Group, Barberton Greenstone Belt (BGB), South Africa, provides a unique window into Archaean sedimentary, magmatic and ecological processes. In the central BGB, a regional mafic complex, consisting of a genetically related major mafic sill, a peperitic dyke stockwork, and extensive basaltic lava flows affected thick quartzose sandstones of the Moodies Group. We argue that epithermal hydrothermalism associated with this magmatic event occurred, at least in part, syndepositionally and in places destroyed, in other places preserved the abundant benthic microbial mats in terrestrial- and coastal-facies sandstone of this unit. We differentiate four principal types of hydrothermal alteration: (1) Sericitization resulted from ubiquitous feldspar breakdown; (2) iron-oxide alteration replaced the original matrix by fine-grained iron oxide; (3) silicification replaced matrix and most non-silica grains by microcrystalline silica and locally preserved kerogenous microbial mats; and (4) hydraulic fracturing at shallow depth brecciated consolidated Moodies Group sandstone and created closely spaced, randomly oriented fractures and quartz-filled veins. Because stockwork intrusion locally interacted with unconsolidated water-saturated sediment and because the dykes connect the sill with the mafic lava but also follow zones of structural weakness, we suggest that hydrothermalism associated with this magmatic event occurred syndepositionally but was also – within the resolution of radiometric age data – contemporaneous with tight regional folding. We conclude that microbial organisms in Paleoarchaean coastal (tidal, estuarine) environments may have been formerly widespread, possibly even abundant, but are nearly nowhere preserved because they were easily degradable. Preservation of Early Archaean microbial mats in a thermal aureole in the central BGB was controlled by the “just right” degree of heating and very early hydrothermal silicification.

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Brink, M. C., F. B. Waanders, A. A. Bisschoff, and N. C. Gay. "The Foch Thrust-Potchefstroom Fault structural system, Vredefort, South Africa: a model for impact-related tectonic movement over a pre-existing barrier." Journal of African Earth Sciences 30, no. 1 (January 2000): 99–117. http://dx.doi.org/10.1016/s0899-5362(00)00010-5.

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Gloyn-Jones, Jonathan, and Alexander Kisters. "Regional folding, low-angle thrusting and permeability networks: Structural controls of gold mineralization in the Hope reef at Fairview Mine, Barberton Greenstone Belt, South Africa." Ore Geology Reviews 102 (November 2018): 585–603. http://dx.doi.org/10.1016/j.oregeorev.2018.09.024.

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Aiyetan, Ayodeji Olatunji, and Dillip Kumar Das. "Evaluation of the Factors and Strategies for Water Infrastructure Project Delivery in South Africa." Infrastructures 6, no. 5 (April 23, 2021): 65. http://dx.doi.org/10.3390/infrastructures6050065.

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Infrastructure project delivery, specifically the delivery of water infrastructure projects, is a serious challenge in South Africa. Therefore, using the study context of water utility agencies in South Africa, the objective of this study was to examine the challenges that emanate from poor delivery and factors that cause poor delivery of water infrastructure projects in South Africa. Furthermore, it evaluated the various strategies that could enable improvement in water infrastructure project delivery. A survey research method constituting data obtained on the perceptions of relevant stakeholders and ordinal regression modeling were used for conducting the study. Findings suggest that delay in project completion, cost overruns, poor quality of work, poor fund utilization, and poor service delivery are the major challenges of the poor delivery of projects. The major factors that cause such challenges are linked to four aspects of the infrastructure projects such as project management, organization and management, construction and construction management, and sociopolitical. Six-pronged strategic measures, which include capacity building, the appointment of competent and skilled professionals, structuring review and monitoring processes, enhancing collaboration and communication among stakeholders, enabling accountability and transparency, and adopting participative leadership, can assist efficient water infrastructure project delivery in South Africa.

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Scholz, Christopher A., Donna J. Shillington, Lachlan J. M. Wright, Natalie Accardo, James B. Gaherty, and Patrick Chindandali. "Intrarift fault fabric, segmentation, and basin evolution of the Lake Malawi (Nyasa) Rift, East Africa." Geosphere 16, no. 5 (July 10, 2020): 1293–311. http://dx.doi.org/10.1130/ges02228.1.

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Abstract The Lake Malawi (Nyasa) Rift, in the East African Rift System (EARS), is an ideal modern analogue for the study of extensional tectonic systems in low strain rate settings. The seismically active rift contains the 700-m-deep Lake Malawi, one of the world’s oldest and largest freshwater lakes with one of the most diverse endemic faunal assemblages on Earth. Modern and reprocessed legacy multichannel seismic-reflection data are constrained by velocity information from a wide-angle seismic experiment to evaluate variability in extension, segmentation, and timing of fault development along the 550-km-long rift zone. Fault geometries and patterns of synrift sediment fills show that the Lake Malawi Rift is composed of three asymmetric rift segments, with intervening accommodation zone morphologies controlled by the degree of overlap between segment border faults. Most extension occurs on the basin border faults, and broadly distributed extension is only observed at one accommodation zone, where no border fault overlap is observed. Structural restorations indicate a weakly extended rift system (∼7 km), with diminishing values of extension and thinner rift fill from north to south, suggesting a progressively younger rift to the south. There is no evidence of diking, sill injection, or extrusives within the synrift fill of the Lake Malawi Rift, although the volcanic load of the Rungwe magmatic system north of the lake and related subsidence may explain the presence of anomalously thick synrift fill in the northernmost part of the lake. The thickest synrift depocenters (∼5.5 km) are confined to narrow 10- to 20-km-wide zones adjacent to each rift segment border fault, indicating concentration of strain on border faults rather than intrarift faults. Intrarift structures control axial sediment delivery in the North and Central rift segments, focusing sediment into confined areas resulting in localized overpressure and shale diapirs. The asymmetric, basement-controlled relief was established early in rift development. When overprinted with frequent high-amplitude hydroclimate fluctuations, which are well documented for this basin, the resulting highly variable landscape and lake morphometry through time likely impacted the diverse endemic faunas that evolved within the basin. New seismic-reflection data, augmented by wide-angle seismic data and age constraints from drill core, offer the most highly resolved 3D view to date of latest Cenozoic extensional deformation in East Africa and provide a foundation for hazards analysis, resource assessments, and constraining deformation in a low strain rate, magma-poor active rift.

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Creus, P. K., I. J. Basson, C. K. Koegelenberg, J. Ekkerd, P. J. H. de Graaf, M. Bester, and T. Mokele. "3D Fabric analysis of Venetia Mine, South Africa: Using structural measurements and implicitly-modelled surfaces for improved pit slope design and risk management." Journal of African Earth Sciences 155 (July 2019): 137–50. http://dx.doi.org/10.1016/j.jafrearsci.2019.04.009.

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Kurszlaukis, S. "Volcanological and structural aspects of the Venetia kimberlite cluster - a case study of South African kimberlite maar-diatreme volcanoes." South African Journal of Geology 106, no. 2-3 (September 1, 2003): 165–92. http://dx.doi.org/10.2113/106.2-3.165.

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Drabon, Nadja, Christoph E. Heubeck, and Donald R. Lowe. "Evolution of an Archean fan delta and its implications for the initiation of uplift and deformation in the Barberton greenstone belt, South Africa." Journal of Sedimentary Research 89, no. 9 (September 11, 2019): 849–74. http://dx.doi.org/10.2110/jsr.2019.46.

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ABSTRACT The 3.28 to 3.23 Ga Mapepe Formation in the Barberton greenstone belt, South Africa, marks the initiation of widespread tectonic uplift and deformation after nearly 300 million years of predominantly basaltic and komatiitic magmatism under largely anorogenic conditions. This rapid transition is recorded in the eastern Barite Valley area by the buildup of a fan delta. Well-exposed sections there reach about 450 m thick and can be divided (from base to top) into five informal members: Member 1 is dominated by mudstone with subordinate banded ferruginous chert and turbiditic sandstone representing a deep-water basinal environment. Member 2 is composed of siltstone and fine-grained sandstone reworked by currents to form laminated, cross-laminated, and low-angle cross-stratified sediments in an off-shore or possibly subtidal fan-delta-front setting. Member 3 overlies member 2 unconformably; it is composed of predominantly coarse-grained, cross-bedded sandstone interbedded with laminated mudstone deposited on shallow-subtidal to intertidal flats along the fringe of a small fan delta in which putative microbial mats covered low-energy upper tidal flats. Fan-delta sedimentation was subsequently overwhelmed by the influx of dacitic pyroclastic sediments of member 4. Orthochemical sedimentary rocks including barite, jaspilite, and chert deposited on top of this shallow-water bank. Mappable facies changes towards the northeast and southwest document the transition from bank top into major mass-transport deposits of fan-delta slope facies and then into basinal deposits. Subsequent relative sea-level rise resulted in the return to below-wave-base deposition of turbiditic sandstone, mudstone, and banded ferruginous chert of member 5. The lenticular geometry of units in cross section, mineralogical immaturity, and high variability in provenance of the coarse-grained units imply short-distance transport of sediment derived from strata of the underlying Onverwacht Group and from local penecontemporaneous dacitic volcanism. Throughout the greenstone belt, Mapepe rocks in several structural belts display fan deltas developed adjacent to small, local uplifts. While the cause of these uplifts has generally been associated with the initiation of geodynamically driven tectonic activity in the BGB, it is possible that a cluster of large meteorite impacts may have directly or indirectly triggered the crustal deformation.

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“Beraki, W. H., F. F. Bonavia, T. Getachew, R. Schmerold, and T. Tarekegn. "The Adola Fold and Thrust Belt, southern Ethiopia: a re-examination with implications for Pan-African evolution." Geological Magazine 126, no. 6 (November 1989): 647–57. http://dx.doi.org/10.1017/s0016756800006944.

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AbstractThe Adola Fold and Thrust Belt of Ethiopia is a late- Precambrian, north–south trending belt of volcanic-sedimentary and ophiolite–like units overlying ‘basement rocks’ (gneisses and granitic gneisses). Detailed structural analysis and data from microfabrics have documented two thrusting events (D1, D5) and three folding phases (F2, F3, F4). All deformations have affected both the rocks of the Adola Fold and Thrust Belt and the ‘older basement’. The structural history is recorded as follows: (1) formation of ductile shear zones (Dl); (2) progressive development of recumbent folds (F2); (3) a superimposed north-south trending, tight to isoclinal, upright penetrative folding phase (F3), which imparted the dominant structure of the region; (4) F3 was later gently affected, at right angles to F3, by the last folding event (F4). Metamorphic conditions during this deformational cycle reached highest greenschist to medium amphibolite facies conditions. Close to major thrust contacts imbrication produced metamorphic discontinuities. Marked retrograde metamorphism in narrow horizons indicates a continuation of minor movements along the major thrusts, postdating the metamorphic peak. Evidence of a second thrusting/faulting episode (D5) is only recorded at the mesoscale. This latter event was accompanied by very low to low grade metamorphic conditions. In accepting the previously reported age of 1030±40 Ma for the volcanic–sedimentary unit of the Adola Fold and Thrust Belt, and the interpretation of these units as an immature island arc, a possibly early Pan-African oceanic accretion is postulated.

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Déléris, J., A. Nédélec, E. Ferré, G. Gleizes, R. P. Ménot, C. K. Obasi, and J. L. Bouchez. "The Pan-African Toro Complex (northern Nigeria): magmatic interactions and structures in a bimodal intrusion." Geological Magazine 133, no. 5 (September 1996): 535–52. http://dx.doi.org/10.1017/s0016756800007822.

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AbstractThe Toro Complex is one of the Pan-African Older Granites of Nigeria, first described as a reversely zoned pluton made of a central dioritic mass surrounded by a broad granitic rim. It has been thoroughly reinvestigated both from the petrographic and structural points of view, with the help of systematic anisotropy of magnetic susceptibility (AMS) measurements. The granite main body is a hornblende–biotite porphyritic monzogranite characterized by an early submagmatic fabric displaying a concentric pattern of foliations and west plunging lineations (stage 1). This fabric is overprinted by a later one due to solid-state strain along north-south subvertical dextral shear zones (stage 2). In the vicinity of the diorite, an evengrained granite displays magmatic structures that are contemporaneous with this strike-slip event. The diorite–granite contact is a complex zone where field, petrographic and geochemical data enable recognition of the effects of mixing and mingling between a mafic and a felsic magma. Tonalites cropping out within this contact zone are interpreted as hybrid rocks. The reverse zonation of the diorite itself is also the result of some hybridization process. Magmatic interactions mainly resulted from in situ infiltration of granitic liquid into the dioritic mass. The detailed history of this bimodal intrusion began with the emplacement of the granitic magma acquiring a first stage fabric. Before full crystallization of the granitic core, intrusion of the dioritic magma permitted reheating of the granitic magma that then crystallized with specific structural characters. The second stage structures, whether characterized by magmatic fabric near the diorite or by solid-state strain features in north–south shear zones elsewhere in the granite, are related to late Pan-African dextral strike-slip tectonics in the basement of northern Nigeria. The bimodal Toro Complex is therefore considered as a late Pan-African syntectonic pluton.

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Pretorius, H. C. F., M. Tredoux, M. A. G. Andreoli, and P. D. Vermeulen. "A long term baseline and variability of natural radionuclides in groundwater at the Vaalputs low-level radioactive waste disposal facility, Namaqualand, South Africa: regional implications." South African Journal of Geology 123, no. 1 (March 1, 2020): 105–16. http://dx.doi.org/10.25131/sajg.123.0006.

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Abstract Vaalputs is the only South African nuclear waste disposal facility; it is licensed to dispose of low and intermediate level radioactive waste. Possible disposal of long-lived waste, potentially including spent fuel rods, prompted a study to establish a baseline of naturally-occurring radionuclides from the U and Th decay chains in the groundwater of Vaalputs. This baseline was created by investigating a dataset containing 25 years of analyses of the groundwater at the Vaalputs site. The behaviour over time, of 23 radionuclides in groundwater samples from 13 annually and three quarterly sampled boreholes, was evaluated and integrated in order to establish changing trends in the activities of radionuclides, the relative contributions of individual radionuclides to total radiation levels and how these were influenced by groundwater conditions. 238U levels showed a natural anomaly in the near-field of the disposal site that was attributed to the underlying basement rocks (granites) which are anomalously enriched in U. A set of duplicate samples from 2009 determined that the activity ratio of 234U/238U in the groundwater of Vaalputs is 4.1; this is ascribed to more rapid leaching of 234U relative to 238U, because of increased crystal structural damage around sites surrounding 234U atoms. High levels of 226Ra, unsupported by 238U, were found in groundwater from boreholes on the western side of the property: this groundwater yielded low values for 234U/238U, lower pH and stronger oxidizing conditions than groundwater from the rest of the area. The absence of overlying sedimentary rocks, which tend to ameliorate the effects of high radiation from granites by absorption, is suggested as the reason for the different geochemical conditions of the groundwater from boreholes in the west. This suggestion may apply to those boreholes elsewhere in Namaqualand with low published concentrations of 238U, but exceptionally high levels of α -and β-emitters. 232Th and its daughter radionuclides yielded radiation levels far below the guideline of 1 Bq.L-1 specified by the World Health Organization; this result is in line with the known low mobility of Th in groundwater systems.

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Albini, Paola, Fleur O. Strasser, and Nicolette S. Flint. "Earthquakes from 1820 to 1936 in Grahamstown and surroundings (Eastern Cape Province, South Africa)." Bulletin of Earthquake Engineering 12, no. 1 (February 2014): 45–78. http://dx.doi.org/10.1007/s10518-013-9562-0.

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Rekhiss, Farhat, Selma Mguidich, Jamel Oualiet, and Mohamed Moncef Turki. "Biphase metamorphism within the Jurassic-early Cretaceous series from the Djedeida range (northeastern Tunisia)." Bulletin de la Société Géologique de France 181, no. 3 (May 1, 2010): 259–68. http://dx.doi.org/10.2113/gssgfbull.181.3.259.

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Abstract Situated in the northern Tunisian “Diapir and dome zone” (Tunisian Atlas), the Djedeida hills consist of a south-dipping monoclinal series globally trending E-W. This pelitic-carbonate series latest Jurassic (Maiana Formation) to Early Cretaceous (Hamada and Seroula Formations) in age, exhibits clear mineralogical and structural transformations related to significant changes in pressure and/or temperature conditions. Structural and microstructural analysis allowed us to characterize the metamorphic pattern, and to discuss about the geodynamical context of its occurrence connected to the regional evolution. Deformation patterns mostly consist of two sets of ubiquitous fracture schistosities well-developped over the entire structure, as well as centimetric to metric folds systematically displayed by thin ferruginized layers. These field-observations, which are consistent with microscopic analysis, show evidences for the occurrence of two distinct deformational events successively affecting the area. Superposition of the two fabrics led to the development of a pervasive parallelepipedic chipping in the rock mass that is particularly obvious in the pelitic unit. Layer-parallel S1 and strongly oblique S2 schistosities are respectivelly associated with chlorite and illite cristallization. Neoformations of illite into chlorite former phases occur in relation with a simple shearing, which broadly characterizes the second event with evidences such as rotated phenoblasts (quartz and pyrite), chlorite sigmoidal deformation, and mica, calcite, feldspar growth into pressure shadow. These syn-tectonic mineralogical phases record a low-grade metamorphism evolving into the sequence from the anchizone to the epi-metamorphic facies. Based on structural and mineralogical criterions, this analysis allows us to conclude that the first event is consistent with an early stage metamorphism occurring within crustal-thinning conditions, thus likely to express the lower Mesozoic transtension which affected northern Africa as a consequence of the Te-thyan opening. The second event, suggesting a compressive context, is more probably associated to the Alpine convergence responsible for the Atlasic tectonics affecting the area at the Neogene time.

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Van Kranendonk, M. J., A. Kröner, E. Hegner, and J. Connelly. "Age, lithology and structural evolution of the c. 3.53 Ga Theespruit Formation in the Tjakastad area, southwestern Barberton Greenstone Belt, South Africa, with implications for Archaean tectonics." Chemical Geology 261, no. 1-2 (April 2009): 115–39. http://dx.doi.org/10.1016/j.chemgeo.2008.11.006.

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38

Polomé, L. G. B. T. "The application of the mise-a-la-masse electrical technique in Greenstone belt gold exploration." Exploration Geophysics 20, no. 2 (1989): 113. http://dx.doi.org/10.1071/eg989113.

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Most of the gold deposits in the Barberton Greenstone belt of South Africa are relatively small and in structurally complex geological areas.The mise-a-la-masse electrical technique, where a current electrode is earthed in a mineralised zone, was used on one of our exploration projects consisting of a sulphides/gold-bearing carbonaceous banded iron formation within a succession of mafic, ultramafic and sedimentary rocks. The technique was successful in delineating individual mineralised units within a broad lithological sequence. During the survey, electrical potential measurements were recorded on surface, in underground drives and in twenty five boreholes. Measurements were also repeated by earthing the mineralised zone in a number of boreholes. Major discontinuities were recognised within the ore zones and used to interpret geological structures. These were then used to define specific units for ore reserve calculations and the application of selected mining techniques.

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39

Michard, André, Abdelkader Mokhtari, Ahmed Chalouan, Omar Saddiqi, Philippe Rossi, and Ech-Cherki Rjimati. "New ophiolite slivers in the External Rif belt, and tentative restoration of a dual Tethyan suture in the western Maghrebides." Bulletin de la Société Géologique de France 185, no. 5 (May 1, 2014): 313–28. http://dx.doi.org/10.2113/gssgfbull.185.5.313.

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AbstractOphiolite slivers have been described recently in the core of the External zones of the Central Rif belt. The present work aims at illustrating new ophiolite slivers further east and discussing the structural position and tectonic emplacement of all these oceanic floor remnants. Their basement consists of gabbros previously dated at 166±3 Ma and their cover includes mafic breccias, micrites and radiolarites. These oceanic slivers are located within the Mesorif nappe stack at the bottom of the Senhadja nappe that roots beneath the Intrarif Ketama unit and was thrust over the more external Mesorif and Prerif units during the Cenozoic inversion of the North African paleomargin. These oceanic crust (OC) slivers belong to the same Mesorif suture zone as the Beni Malek serpentinites and Ait Amrâne metabasites from eastern Rif that also include marbles with ophiolitic clasts and derive from an ocean-continent transition (OCT) domain. After examination of the varied hypotheses that have been suggested to account for the emplacement of these units in the External Rif, we propose that obduction sampled an oceanic corridor opened between the Mesorif and Intrarif domains at the emplacement of the Rif Triassic evaporite basin. The Intrarif block should have been then separated from the African passive margin and connected with the Flysch domain south of the passive margin of the Alboran domain. The pre-collision structure of the Rif transect would involve two hyper-extended passive margins separated by a narrow oceanic transform fault corridor. Therefore the Tethys suture in the western Maghrebides would be split by the Intrarif block and would involve the Flysch zone in the north and the ophiolite bearing Mesorif suture zone in the south.

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Rigby, M. J., I. J. Basson, J. D. Kramers, P. Gräser, and P. K. Mavimbela. "The structural, metamorphic and temporal evolution of the country rocks surrounding Venetia Mine, Limpopo Belt, South Africa: Evidence for a single palaeoproterozoic tectono-metamorphic event with implications for a tectonic model." Precambrian Research 186, no. 1-4 (April 2011): 51–69. http://dx.doi.org/10.1016/j.precamres.2011.01.001.

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41

van Niekerk, H. S., and N. J. Beukes. "Revised definition/outline of the Kheis Terrane along the western margin of the Kaapvaal Craton and lithostratigraphy of the newly proposed Keis Supergroup." South African Journal of Geology 122, no. 2 (June 1, 2019): 187–220. http://dx.doi.org/10.25131/sajg.122.0014.

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Abstract The Kheis Province is situated between the Namaqua-Natal Province and the western margin of the Kaapvaal Craton in the Northern Cape Province of South Africa. It has been described as a thin-skinned fold and thrust belt formed between 1800 and 1700 Ma. The lithostratigraphic subdivision of the rock units comprising the Kheis Province has been a source of much controversy. From detailed study of aerial photography and satellite imagery, as well as field-based studies, the outcrop patterns in the Kheis Province and Kaaien Terrane were reinterpreted and a new stratigraphic subdivision is outlined here. It is proposed that the structural Kaaien Terrane and Kheis Province should be combined into the Kheis Terrane and that the rocks occurring in the Kheis Terrane should be grouped together to form the new Keis supergroup, with the basal metaconglomerate of the Mapedi/Gamagara Formation recognised as the regional unconformity between the Keis supergroup and the underlying rocks of the Transvaal Supergroup in the Griqualand West area. The Keis supergroup is subdivided from the base upwards into the Elim-, Olifantshoek-, Groblershoop- and Wilgenhoutsdrif groups. The basal Elim group is composed of the Mapedi/Gamagara- and Lucknow formations. It is overlain with a regional erosional unconformity by the Olifantshoek group, which is made up of the Neylan-, Hartley-, Volop- and Top Dog formations. The Olifantshoek group is conformably overlain by the Groblershoop group which is comprised of three upward coarsening successions:the Faanshoek- and Faansgeluk formations,the Maraisdraai- and Vuilnek formations andthe Opwag- and Skurweberg formations. The Groblershoop group is in turn erosively overlain by the rocks of the Wilgenhoutsdrif Group, which include the basal erosive Groot Drink formation which is overlain by the Zonderhuis- and Leerkrans formations. The lithologies of the Keis supergroup are in faulted contact with the rocks of the younger Areachap Group of the ~1200 Ma Namaqua-Natal Metamorphic Province.

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42

Tsakou Sonwa, Cyrille Stephane, Jan van Bever Donker, and Russell Bailie. "Polyphase Deformation of the High-Grade Metamorphic Rocks along the Neusspruit Shear Zone in the Kakamas Domain: Insights into the Processes during the Namaquan Orogeny at the Eastern Margin of the Namaqua Metamorphic Province, South Africa." Minerals 11, no. 7 (July 14, 2021): 759. http://dx.doi.org/10.3390/min11070759.

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The central part of the Namaqua Metamorphic Province was subjected to intense deformation under high-grade metamorphic conditions up to granulite facies, but also shows greenschist facies overprints denoting the metamorphic nature during the 1.2–1.0 Ga Namaquan Orogeny. This study examines the structural development of the central Kakamas Domain of the eastern Namaqua Metamorphic Province, which has not been extensively studied previously. The compressional orogenic phase is associated with D1 and D2 deformation events during which northeast–southwest-directed shortening resulted in southwest-directed thrusting illustrated by an intra-domain thrust and southwest-verging isoclinal folds. The post-tectonic Friersdale Charnockite of the Keimoes Suite is emplaced during the D3 deformation event. Late reactivation of the intra-domain thrust in the Kakamas Domain to form the Neusspruit Shear Zone during the D4 event is of a monoclinic nature and is described as a deeply rooted structure with shear direction towards the east. This structure, together with the more local Neusberg Thrust Fault, forms part of an intensely flattened narrow basin in the eastern Namaqua Metamorphic Province. Strain and vorticity indices suggest a transpressional shearing across the Neusspruit Shear Zone and adjacent regions probably initiated during the reactivation of the intra-domain thrust. The ~1.2 to 1.8 km-wide, northwest–southeast striking dextral-dominated Neusspruit Shear Zone constitutes a western regional boundary for the supracrustal Korannaland Group and is composed of steep, narrow zones of relatively high strain, characterised by ductile deformation and penetrative strain.

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Drury, S. A., and S. M. Berhe. "Accretion tectonics in northern Eritrea revealed by remotely sensed imagery." Geological Magazine 130, no. 2 (March 1993): 177–90. http://dx.doi.org/10.1017/s0016756800009845.

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AbstractNew details from remotely sensed images of the structure and disposition of broad lithological variations in the Pan-African of northern Eritrea are discussed in the context of accretionary tectonics. The recognition of major north-south structural discontinuities allows the area to be divided into three discrete terranes with apparently different histories of deformation and metamorphism, magmagenesis and sedimentation. The central Hagar Terrane is dominated by large ultramafic masses with a volcano-sedimentary layered sequence, and shows the effects of major sinistral transpression and lateral expulsion. It is bounded to the west by a major fault, the Barka suture, and abuts the older Barka Terrane that comprises metasediments with evidence for polyphase ductile deformation and pre-kinematic dyke emplacement. The Hagar Terrane is thrust against the eastern Nacfa Terrane, which is dominated by low-grade calc-alkaline metavolcanics and immature volcanoclastic sediments intruded by syn-kinematic plutons. These units are pre-dated by an earlier high-grade basement and post-dated by high-level unmetamorphosed silicic volcanics and redbed sediments. The complex is suggested to have been assembled by oblique accretion from the southeast after arc volcanism in the Nacfa Terrane and back-arc extension in the Hagar Terrane ended with the cease of subduction.

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Manzi, Musa S. D., Mark A. S. Gibson, Kim A. A. Hein, Nick King, and Raymond J. Durrheim. "Application of 3D seismic techniques to evaluate ore resources in the West Wits Line goldfield and portions of the West Rand goldfield, South Africa." GEOPHYSICS 77, no. 5 (September 1, 2012): WC163—WC171. http://dx.doi.org/10.1190/geo2012-0133.1.

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As expensive as 3D seismic reflection surveys are, their high cost is justified by improved imaging of certain ore horizons in some of the Witwatersrand basin gold mines. The merged historical 3D seismic reflection data acquired for Kloof and South Deep mines forms an integral part of their Ventersdorp Contact Reef mine planning and development programme. The recent advances in 3D seismic technology have motivated the reprocessing and reinterpretation of the old data sets using the latest algorithms, therefore significantly increasing the signal-to-noise ratio of the data. In particular, the prestack time migration technique has provided better stratigraphic and structural imaging in complex faulted areas, such as the Witwatersrand basin, relative to older poststack migration methods. Interpretation tools such as seismic attributes have been used to identify a number of subtle geologic structures that have direct impact on ore resource evaluation. Other improvements include more accurate mapping of the depths, dip, and strike of the key seismic horizons and auriferous reefs, yielding a better understanding of the interrelationship between fault activity and reef distribution, and the relative chronology of tectonic events. The 3D seismic data, when integrated with underground mapping and borehole data, provide better imaging and modeling of critical major fault systems and zones of reef loss. Many faults resolve as multifault segments that bound unmined blocks leading to the discovery and delineation of resources in faulted areas of the mines.

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45

Qiu, Longjun, Zhaoxi Chen, and Yalei Liu. "Recognition of the pre-salt regional structure of Kwanza basin, offshore in West Africa, derived from the satellite gravity data and seismic profiles." Journal of Geophysics and Engineering 17, no. 6 (September 25, 2020): 956–66. http://dx.doi.org/10.1093/jge/gxaa055.

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Abstract Kwanza basin, located on the west coast of Africa and the east side of the South Atlantic Ocean, has the potential for deep-water oil and gas exploration. Previous studies have shown that the pre-salt system within the area has high potential for oil and gas storage. However, due to the shielding effect of the evaporating salt rock during the Aptian period, the quality of seismic reflection profiles of the pre-salt layers is poor. This means that the pre-salt sequences, the main fault, the scale and distribution pattern of the rift are not clear. To clarify the pre-salt regional structure pattern and further guide pre-salt exploration, we carried out a series of analyses and target processing of seismic and gravity data. Further, combining other available geological and lithology data as well as a tectonic model, we put forward a new understanding of the pre-salt structure of Kwanza basin. The research shows that the Kwanza basin can be divided into three uplift belts below the salt layer, which are distributed in the NW–SE trending direction. The three key profiles illustrate the distribution of uplift and depression in detail. The explained structural highs distributed in the outer Kwanza basin may be related to oil and gas reservoir. This study could provide the geophysical basis for the re-interpretation of the pre-salt seismic sequence, the strategic selection of pre-salt oil and gas and the next exploration deployment.

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46

Gouws, R., and E. le Roux. "Design and heat flow analysis of a commercial energy efficient in-line water heating system." World Journal of Engineering 11, no. 3 (June 1, 2014): 239–46. http://dx.doi.org/10.1260/1708-5284.11.3.239.

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In this paper, the authors provide the design, heat flow analysis and pressure analysis of a commercial energy efficient in-line water heating system in South Africa. The designed commercial in-line water heating system captures the energy consumption, flow rate, temperature and pressure during operation and accordingly responds on these values to increase the energy efficiency of the system. The user is constantly aware of the energy consumption and cost during operation and can choose to switch to a more economical setting to conserve energy. A central processor with PID control was used to optimize the energy consumption of the in-line water heating system. An overview on the design and results of the heat flow analysis and pressure analysis are provided.

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Le Roy, Pascal, Claire Gracia-Garay, Pol Guennoc, Jean-François Bourillet, Jean-Yves Reynaud, Isabelle Thinon, Patrick Kervevan, Fabien Paquet, David Menier, and Cédric Bulois. "Cenozoic tectonics of the Western Approaches Channel basins and its control of local drainage systems." Bulletin de la Société Géologique de France 182, no. 5 (September 1, 2011): 451–63. http://dx.doi.org/10.2113/gssgfbull.182.5.451.

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Abstract The geology of the Channel Western Approaches is a key to understand the post-rift evolution of the NW European continental margin in relation with the Europe/Africa collision. Despite considerable evidence of Tertiary tectonic inversion throughout the Channel basin, the structures and amplitudes of the tectonic movements remain poorly documented across the French sector of the Western Approaches. The effect of the tectonic inversion for the evolution of the “Channel River”, the major system that flowed into the English Channel during the Plio-Quaternary eustatic lowstands, also needs to be clarified. Its drainage basin was larger than the present-day English Channel and constituted the source of terrigenous fluxes of the Armorican and Celtic deep sea fans. A lack of high-resolution seismic data motivated the implementation of the GEOMOC and GEOBREST cruises, whose main results are presented in this paper. The new observations highlight the diachronism and the contrast in amplitudes of the deformations involved in the inversion of the French Western Approaches. The tectonic inversion can be described in two stages: a paroxysmal Paleogene stage including two episodes, Eocene (probably Ypresian) and Oligocene, and a more moderate Neogene stage subdivided into Miocene and Pliocene episodes, driven by the reactivation of the same faults. The deformations along the North Iroise fault (NIF) located at the termination of the Medio-Manche fault produced forced folds in the sedimentary cover above the deeper faults. The tectonic inversion generated uplift of about 700 m of the mid-continental shelf south of the NIF. The isochron map of the reflectors bounding the identified seismic sequences clearly demonstrates a major structural control on the geometry of the Neogene deposits. First, the uplift of the eastern part of the Iroise basin during the upper Miocene favoured the onset of a broad submarine delta system that developed towards the subsiding NW outer shelf. The later evolution of the ’palaeovalley’ network corresponding to the western termination of the “Channel River” exhibits a ’bayonet’ pattern marked by a zigzagging pattern of valleys, with alternating segments orientated N040oE and N070oE, controlled by Neogene faulting. The palaeovalley network could have begun during Reurevian or Pre-Tiglian sea-level lowstands, which exposed the entire shelf below the shelf edge. The amplitude of the sea-level fall is assumed to have been magnified by uplift of the Iroise basin, followed by later tilting of the outer shelf, as observed in many other examples documented along the North Atlantic margins.

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Torremans, Koen, Philippe Muchez, and Manuel Sintubin. "Non-cylindrical parasitic folding and strain partitioning during the Pan-African Lufilian orogeny in the Chambishi–Nkana Basin, Central African Copperbelt." Solid Earth 9, no. 4 (August 10, 2018): 1011–33. http://dx.doi.org/10.5194/se-9-1011-2018.

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Abstract. A structural analysis has been carried out along the south-east margin of the Chambishi–Nkana Basin in the Central African Copperbelt, hosting the world-class copper and cobalt (Cu–Co) Nkana orebody. The geometrically complex structural architecture is interpreted to have been generated during a single NE–SW-oriented compressional event, clearly linked to the Pan-African Lufilian orogeny. This progressive deformation resulted primarily in asymmetric multiscale parasitic fold assemblages, characterised by non-cylindrical NW–SE-oriented periclinal folds that strongly interfere laterally, leading to fold linkage and bifurcation. The vergence and amplitude of these folds consistently reflect their position along an inclined limb of a NW-plunging megascale first-order fold. A clear relation is observed between the intensity of parasitic folding and the degree of shale content in the Copperbelt Orebody Member (COM), which hosts most of the ore. Differences in fold amplitude, wavelength and shape are explained by changes in mechanical stratigraphy caused by lateral lithofacies variation in ore-bearing horizons. In addition, strong differences in strain partitioning occur within the deforming basin, which is interpreted to be in part controlled by changes in mechanical anisotropy in the layered rock package. This work provides an essential backdrop to understand the influence of the Lufilian orogeny on metal mineralisation and (re-)mobilisation in the Copperbelt.

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Filho, Nelson Ribeiro, Cristiano Mendel Martins, and Renata de Sena Santos. "A NOVEL REGIONAL-RESIDUAL SEPARATION APPROACH FOR GRAVITY DATA THROUGH CRUSTAL MODELING." Revista Brasileira de Geofísica 36, no. 4 (December 21, 2018): 1. http://dx.doi.org/10.22564/rbgf.v36i4.1980.

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ABSTRACT. Gravity anomalies normally contain information of all sources beneath Earth’s surface. Once residual anomalies exhibit information about the main target, the knowledge of this specific residual signal is extremely important to interpretation. To find this signal, it’s necessary to perform regional-residual separation. We present here a new approach of separation by using gravity crustal modeling. We divide the surface in prisms, with density given by GEMMA. We calculate the regional signal, assuming Earth’s crust can be the source of observed anomaly. This methodology was applied on Barreirinhas basin-Brazil. Its formation is related to geologic events in South America-Africa break. Besides, the complex geology is the main obstacle on finding the residual anomaly. We compare our methodology with robust-polynomial fitting and spectral-analysis. They were not able to identify the residual anomaly. Main trouble relies on absence of crust information. Those kind of environment usually requires forward modeling and/or gravity inversion. On the other hand, our approach considers all crust’s parameters. Then the difficulty on choosing the residual no longer exists. The residual anomaly follows a geologic pattern. The crustal depocenter was mapped between structural faults. Therefore, our results satisfies the main expectation and are extremely linked to Barreirinhas basin’s geological background. We recommend this separation procedure, once Earth’s crustal model and gravity data are available for all planet.Keywords: Gravity modeling; GEMMA model; Barreirinhas basin; residual anomaly. RESUMO. Anomalias gravimétricas contêm informações de todas as fontes na superfície terrestre. Uma vez que anomalias residuais exibem informações sobre alvos principais, o conhecimento desse específico sinal residual é extremamente importante para interpretação. Para encontrá-lo, é necessário realizar separação regional-residual. Apresentamos aqui uma nova abordagem de separação utilizando a modelagem gravimétrica crustal. Discretizamos a superfície em prismas, com densidade fornecida pelo modelo GEMMA. Calculamos o sinal regional, assumindo que a crosta terrestre é a fonte da anomalia observada. Aplicamos esta metodologia na bacia de Barreirinhas - Brasil, que tem sua formação relacionada aos eventos geológicos de separação da América do Sul e África. Além disso, a complexidade geológica é considerada o principal obstáculo para encontrar esta anomalia residual. Comparamos nossa metodologia com Ajuste Polinomial Robusto e Análise Espectral. Essas técnicas não foram capazes de identificar a anomalia residual. O principal problema se dá pela ausência de informações acerca da crosta. Para esse ambiente, geralmente requer modelagem direta e/ou inversão geofísica. Por outro lado, nossa abordagem considera todos os parâmetros crustais e a dificuldade em escolher o residual deixa de existir. A anomalia residual apresenta um padrão geológico. O depocentro crustal foi mapeado entre falhas estruturais. Nossos resultados satisfazem a expectativa principal e estão extremamente ligados ao cenário geológico da bacia. Recomendamos este procedimento de separação, uma vez que os modelos crustais e dados gravimétricos estão disponíveis para todo o planeta.Palavras-chave: Modelagem gravimétrica; modelo GEMMA; bacia de Barreirinhas; anomalia residual

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Van Beukering, Chris, Pierre Hertzog, and Arthur James Swart. "Investigating thermal supplementation of an aquaponics system under severe climate conditions." World Journal of Engineering 18, no. 4 (January 25, 2021): 639–44. http://dx.doi.org/10.1108/wje-10-2020-0532.

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Purpose Climate change strains scarce water resources and food production infrastructure, necessitating establishment of sound scientific basis for operation of sustainable alternative food production methodologies - such as aquaponics, which promises high yield versus small footprint. In a climate (such as in Bloemfontein, South Africa) including temperatures below freezing, real-time aquaponics monitoring and control is necessary to mitigate thermal losses and to ensure sustainability of fish stock and bio-filter micro-organisms. The system thermal energy also needs sustainable supplementation during wintertime. This study/paper aims to address the problem of monitoring and controlling thermal energy in a medium sized aquaponics system, to ensure biological sustainability, especially during extreme cold weather events. Design/methodology/approach Required supplementation was determined and the aquaponics system described and quantified in terms of mass-flow power transfer by measuring loop differential temperature and flow rate. Cold front temperature data evaluation determined implementation suitability and -sustainability. Subsystem temperature contributions to the main reservoir, and their cumulative influence on the biological component, were considered. Findings Results indicate thermal supplementation enabled 1.3 °C temperature loss mitigation for a 42-kl water reservoir over a period of three days, offsetting severe system temperature decrease during a cold front event, and preventing organism mortality Originality/value Quantification of flow loop power transfer, and successful supplementation monitoring and control, demonstrates the approach and implementation merit in the Bloemfontein area. Wi-Fi-enabled online real-time data potentially facilitates incorporation into the concept of “Sustainable Smart Cities”.

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Journal articles on the topic 'Geology structural south africa'

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