Lithostratigraphy of the Mesoproterozoic Yas-Schuitdrift Batholith, South Africa and Namibia

2020 ◽  
Vol 123 (3) ◽  
pp. 431-440
Author(s):  
C.A. Groenewald ◽  
P.H. Macey
Keyword(s):  
South Africa ◽  
Large Scale ◽  
Granulite Facies ◽  
Biotite Granite ◽  
Mafic Mineral ◽  
Alkali Granites ◽  
Augen Gneiss ◽  
Outer Perimeter ◽  
Dome Shape

Abstract The granitic and leucogranitic Yas and Schuitdrift Gneisses occur together as a large ovoid pre-tectonic batholith that crosses the Orange River border between South Africa and Namibia. They occur in the central parts of the Kakamas Domain in the Namaqua Sector of the Namaqua-Natal Metamorphic Province where they intrude, and are deformed together with, slightly older (~1.21 Ga) orthogneisses and granulite-facies metapelitic gneisses. The Yas Gneiss occurs mainly on the outer perimeter and northern parts of the batholith and comprises equigranular leucogranite gneiss and biotite granite augen orthogneiss, whereas the Schuitdrift biotite-hornblende augen gneiss is located at the centre and southern parts of the batholith. The batholith is strongly deformed with penetrative Namaqua-aged gneissic fabrics defined by grain-flattening of quartz and feldspar in the equigranular leucogneisses and aligned K-feldspar megacrysts in the augen gneisses. The gneissic fabric is refolded during a large-scale folding event that results in the dome-shape of the batholith and controls the present outcrop pattern of its various components. Flexure along the margins of the batholith refoliated the gneisses into a zone of mylonitic rocks. The Yas and Schuitdrift Gneisses have similar geochemistry and classify as alkali granites and alkali leucogranites. They are felsic (mean SiO2: 74.5 wt%) and potassic (mean K2O: 5.8 wt%) but have low MgO, CaO and Na2O, reflecting their low mafic mineral and plagioclase contents. The Schuitdrift Gneiss yielded U-Pb zircon ages of 1 191 ± 7 and 1 187 ± 6 Ma.

Lithostratigraphy of the Mesoproterozoic Twakputs Gneiss

2021 ◽  
Author(s):  
S. Doggart ◽  
P.H. Macey ◽  
D. Frei
Keyword(s):  
South Africa ◽  
Granulite Facies ◽  
Biotite Granite ◽  
Main Phase ◽  
Coarse Grained ◽  
Zircon Dating ◽  
Chemical Variability ◽  
Type Granite ◽  
Penetrative Foliation ◽  
Ubiquitous Presence

Abstract The Twakputs Gneiss is a garnetiferous, K-feldspar megacrystic, biotite granite-granodiorite orthogneiss. It represents a major unit in the Kakamas Domain of the Mesoproterozoic Namaqua-Natal Metamorphic Province extending about 250 km between Riemvasmaak in South Africa and Grünau in southern Namibia. The Twakputs Gneiss occurs as foliation-parallel, sheet-like bodies tightly infolded together with granulite-facies paragneisses into which it intrudes along with a variety of other pre-tectonic granite and leucogranite orthogneisses. These rocks were subsequently intruded by late-tectonic garnet-leucogranites, granites and charnockites. The Twakputs Gneiss is a distinctive unit characterised by large ovoid to elongate megacrysts of twinned perthitic K-feldspar, set in a coarse-grained matrix of garnet, biotite, quartz and feldspar. It contains a penetrative foliation defined by the alignment of K-feldspars and streaks of biotite that developed during the main phase D2 of the Namaqua Orogeny (~1.2 to 1.1 Ga). The foliation and an accompanying elongation lineation are more intensely developed along lithological contacts, especially at the margins of the mega-scale F3 domes and basins that refold the regional fabrics. U-Pb zircon dating of the Twakputs Gneiss has yielded concordia ages of between ~1192 and 1208 Ma. Whole-rock geochemistry shows consistent major, trace and REE elemental trends, and thus reflect chemical variability from a single fractionating magma. The Twakputs Gneiss has a granitic to granodiorite composition and is strongly peraluminous. The geochemistry and the ubiquitous presence of garnet and pelitic xenoliths indicate an S-type granite protolith. The Twakputs Gneiss is the most voluminous and widespread member of the Eendoorn Suite which comprises seven textural variants of garnetiferous, K-feldspar-megacrystic granitoid orthogneiss of the same age.

scholarly journals Seawater desalination as an option to alleviate water scarcity in South Africa: the need for a strategic approach to planning and environmental decision-making

2014 ◽  
Vol 4 (4) ◽  
pp. 287-293 ◽  
Author(s):  
G. O. Schreiner ◽  
R. C. van Ballegooyen ◽  
W. Osman
Keyword(s):  
South Africa ◽  
Water Policy ◽  
Large Scale ◽  
Water Security ◽  
Bulk Water ◽  
Policy Makers ◽  
Environmental Decision Making ◽  
Strategic Approach ◽  
Seawater Reverse Osmosis ◽  
National Water

In the last decade, seawater reverse osmosis (SWRO) has come to be seen by policy-makers as a novel technology that will significantly advance water security in South African coastal regions. Water purveyors, from the private sector, local/district municipalities and provincial authorities, are undertaking studies to explore the feasibility of SWRO to meet growing demand and relieve mounting pressure on current bulk water supply infrastructure. With this in mind, it is suggested that national strategic planning should be introduced to present the opportunities and constraints of the desalination option within the national water and energy policy. In absence of this, piece-meal decisions will be made at local authority levels and the construction of SWRO plants will be determined by regional circumstances (e.g. drought) as opposed to national water policy agenda. This paper explores the value of such a strategy by considering the drivers of SWRO in South Africa, the risk of unplanned large-scale SWRO implementation (with a focus on environmental impacts) and the initial steps that could be taken toward a Strategic Environmental Assessment for SWRO in South Africa.

Corporate Structure, Industrial Development, and Structural Change in South Africa

2021 ◽  
pp. 348-374
Author(s):  
Pamela Mondliwa ◽  
Simon Roberts
Keyword(s):  
South Africa ◽  
South African ◽  
Industrial Development ◽  
Large Scale ◽  
Economies Of Scale ◽  
Corporate Structure ◽  
Continuity And Change ◽  
Economic Concentration ◽  
And Control

The orientation of large corporations is at the heart of how countries develop. These firms make large-scale investments and realize economies of scale and scope, as well as make long-term commitments to the learning and research necessary to build capabilities required for industrial development. In many industries and sectors the large firms have key technologies, govern access to markets, and control material inputs which can shape the structure of an economy. The chapter reviews the changing corporate structure in South Africa focusing on the implications for industrial development, the evolving internationalization of South African businesses, and the political economy of economic policy. While the South African economy has remained highly concentrated, the corporate structure has altered in fundamental ways. The chapter identifies key elements of continuity and change to explain the implications of the continued high levels of economic concentration for the economy through the lens of the corporate structure.

Bombing Flies

2018 ◽  
pp. 223-246
Author(s):  
Clapperton Chakanetsa Mavhunga
Keyword(s):  
United States ◽  
South Africa ◽  
Organochlorine Pesticides ◽  
Large Scale ◽  
The United States ◽  
Ease Of Use ◽  
Technical Aspects ◽  
Aerial Spraying ◽  
And Performance ◽  
Ground Spraying

This chapter explores the use of aircraft to spray organochlorine pesticides (OCPs). It begins by tracing the origins of the practice in KwaZulu, South Africa, where ndege were adopted for pesticide spraying because of their ease of use, capacity for large-scale coverage, very few personnel required, and capability to reach mpukane habitats otherwise inaccessible by ground spraying. The second section examines the technical aspects of aerial spraying as an example of the extension of methods designed in the United States for agricultural or military purposes to deal with zvipukanana and with conditions for which they were not originally designed. In the final sections, the deployment and performance of first fixed-wing aircraft and then helicopters are closely examined.

Dynamics of collapse of an impact central uplift: Evidence from folds and faults in the collar of the Vredefort Dome, South Africa

2021 ◽  
Author(s):  
Shalene Manzi ◽  
Roger L. Gibson ◽  
Asinne Tshibubudze
Keyword(s):  
South Africa ◽  
Structural Analysis ◽  
Large Scale ◽  
Second Order ◽  
Upward Flow ◽  
Downward Flow ◽  
Kinematic Pattern ◽  
Central Uplift ◽  
Convergent Flow ◽  
Order Structures

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.

Proterozoic geological evolution of the northern Vestfold Hills, Antarctica

1991 ◽  
Vol 128 (4) ◽  
pp. 307-318 ◽  
Author(s):  
C. W. Passchier ◽  
R. F. Bekendam ◽  
J. D. Hoek ◽  
P. G. H. M. Dirks ◽  
H. de Boorder
Keyword(s):  
Large Scale ◽  
Structural Evolution ◽  
Shear Zones ◽  
Granulite Facies ◽  
Strike Slip ◽  
Amphibolite Facies ◽  
Tectonic Event ◽  
Vestfold Hills ◽  
Two Phases ◽  
Brittle Faulting

AbstractThe presence of polyphase shear zones transected by several suites of dolerite dykes in Archaean basement of the Vestfold Hills, East Antarctica, allows a detailed reconstruction of the local structural evolution. Archaean and early Proterozoic deformation at granulite facies conditions was followed by two phases of dolerite intrusion and mylonite generation in strike-slip zones at amphibolite facies conditions. A subsequent middle Proterozoic phase of brittle normal faulting led to the development of pseudotachylite, predating intrusion of the major swarm of dolerite dykes around 1250 Ma. During the later stages and following this event, pseudotachylite veins were reactivated as ductile, mylonitic thrusts under prograde conditions, culminating in amphibolite facies metamorphism around 1000–1100 Ma. This is possibly part of a large-scale tectonic event during which the Vestfold block was overthrust from the south. In a final phase of strike-slip deformation, several pulses of pseudotachylite-generating brittle faulting alternated with ductile reactivation of pseudotachylite.

scholarly journals Structure and Biodiversity of Rhodolith Seabeds: A Special Issue

Diversity ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 300 ◽  
Author(s):  
Fernando Tuya
Keyword(s):  
South Africa ◽  
Large Scale ◽  
Algal Species ◽  
Taxonomic Composition ◽  
High Latitudes ◽  
Decapod Crustaceans ◽  
Special Issue ◽  
Associated Fauna ◽  
Climate Fluctuations ◽  
Wide Range

Rhodolith seabeds function as ‘ecosystems engineers’, which globally provide a range of ‘ecosystem services’. However, knowledge on the structure, composition and distribution of rhodolith seabeds is still lacking. This Special Issue comprises six articles, addressing specific questions of rhodolith seabeds, and covering a wide range of topics. Two papers provide new large-scale information on the presence, structure and distribution of rhodolith beds at two southern hemisphere areas, in particular continental shelfs off South Africa and Brazil. Another two studies contributed to the discovery on new algal species from rhodolith beds, including Sporolithon franciscanum, a new rhodolith-forming species from Brazil, and the small benthic alga Schizocladia ischiensis. In terms of associated fauna, the taxonomic composition and patterns of abundance of decapod crustaceans are described in another article, including the description of a depth-partitioning in the abundance of juveniles and adults of the crab Nanocassiope melanodactylus. Rhodoliths are often present in fossilized deposits, so we can track changes in their presence with climate fluctuations. High temperatures during the Eocene and widespread oligotrophic conditions are finally connected with low abundances of rhodolith beds at mid and high latitudes, despite a larger presence at equatorial regions.

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