The older nsuze group is predominantly volcanic, while dominantly sedimentary volcanic rocks form the younger mozaan group. Olivine water contents in the continental lithosphere and the. Pdf we briefly examine the possible antiquity of the supercontinental cycle while noting. Load general freight outline module 1 prepare for loadingoffloading processes according to specified procedures. A belt of high extensional strain rates running southward along the east africa rift branches at 12s, avoiding the strong region around the kaapvaal craton, which hartnady has named the transgariep plate. The kaapvaal province of the archean kalahari craton differs from other african archean terrains by its early cratonization, representing a nearly 1 mill. International journal of economics, commerce and management, united kingdom licensed under creative common page 41 k unfavorable taxation regime. Physical volcanology and compositions of the basaltic. Sep 01, 2009 this plateau is supported by the archean kaapvaal craton and the surrounding proterozoic basement, a suite of rigid basement blocks that controlled basin development throughout the phanerozoic. A 70 b 66 c 60 d 48 e 72 11 a number and a quarter of that number are added together to get 30. Pdf neoarchean large igneous provinces on the kaapvaal craton. The kaapvaal craton formed and stabilised between 3. He also attended geocongress 2000, the biennial meeting of the geological society of south africa, at which he coauthored some 14 research papers. Precambrian crustal evolution of the rehoboth province.
South africa, and the eastern branch to a less active southeastern. The kaap vaal craton itself is comprised of an eastern domain with. Where none of the filaments change direction, the crossing is interpreted as coincidental fig. The western branch connects to a western arc through angola. I words in bold type in square brackets indicate omissions from existing enactments.
Precise shrimp upb zircon age constraints on the lower. Physical volcanology and compositions of the basaltic lavas. Episodic granitoid emplacement in the western kaapvaal craton. Kimberlitic fluid extraction from the lithospheric mantle. Formation of the archean kaapvaal province revisited. A linear crustal popup structure is broadly coincident with the namaqua front, linked to a mega scale highlow gravity anomaly reflecting deepseated thrusting. Extended abstracts of the 7th international kimberlite conference, cape town, south africa, 224225. Structural history of the southwestern corner of the kaapvaal craton. Episodic granitoid emplacement in the western kaapvaal. The characteristics and specific requirements of the commodity to be transported are identified. Prof wlady altermann and ms vusani v mathada bsc hons archean proterozoic sedimentary transition, volcanism, structural geology, early life, stromatolites, and glacial deposits between 2750 and 2220. Basaltic oceanic plateaux are important features in the geological record.
The structural data exhibited by rocks of the palala shear zone provide evidence for. Variations in the thickness of the crust of the kaapvaal. Words underlined with a solid line indicate insertions in existing enactments. Volcanological and structural aspects of the venetia.
The bushveld complex, the outcrop limbs of which are shown in fig. No evidence for a supercontinental affinity prior to 2. Kimberlitic fluid extraction from the lithospheric mantle due. With the exception of the northern margin, the boundaries of the province are well defined. Information is obtained pertaining to freight that is comprehensive and relevant. I also generated the first reos isotopic data for mantle xenoliths, in this case from the kaapvaal craton, south africa, in collaboration with rick, steve and joe boyd.
The grenvillian namaqua fold belt adjacent to the western. The oldest part of afroeurasia is probably the kaapvaal craton, which together with madagascar and parts of india and western australia formed part of the first supercontinent vaalbara or ur around 3 billion years ago. History of granulitefacies metamorphism and crustal. Anne peslier and colleagues show that olivine components in peridotite xenoliths from the lithosphereasthenosphere boundary region of the kaapvaal craton mantle root. Tectonic evolution of the cape and karoo basins of.
Basic research that assist the targeting of lipassociated mineral resources. A reevaluation of archean intracratonic terrane boundaries on. Olivine water contents in the continental lithosphere and. For this study we found that the os isotopic compositions of the xenoliths were quite variable and were able to correlate os isotopic compositions with proxies for melt depletion. In the present study inhomogeneous, partly uraniferous leucoxenerutile aggregates and brannerite grains from the elliot lake area, canada, and the pongola basin, south africa, were identified by ore microscopy. Siderophile elements in tracing planetary formation and. It suggests that the rehoboth province was attached to the kaapvaal craton before. Estimates of crustal thicknesses using pn times and receiver functions agree well for the southern part of the kaapvaal craton, but not for the northern region. Geochemistry of palaeoarchaean felsic volcanic units of the kaapvaal craton is. This phenomenon of taphonomicdiagenetic filament merging makes it sometimes difficult to identify true branching, where a single filament is split into two. Pdf mesoarchaean and palaeoproterozoic sedimentary. Diamond genesis and petrology fact sheet 51114 12007325 introduction diamond is defined as a naturally occurring, high pressure form of carbon, valued as. Tanzania and southern africa zimbabwekaapvaal cratons. In the first two the kaapvaal craton and rehoboth province were not joined at 1.
Patterns of stress and strain rate in southern africa. The rocks along the southwestern margin of the kaapvaal craton were deformed up to 7 times. Pdf upb geochronology on baddeleyite is a powerful technique that can be applied effectively to chronostratigraphy. After equilibrating with the mantle at the base of the magma ocean, the metallic component of the impactor sinks to merge with the earths protocore without further equilibration. The average crustal thicknesses determined from pn times for the northern and southern regions of the craton were 50. The increased heterogeneity and higher mgo content of the lavas at deeper levels within the plateau are believed to be related. The tax system in kenya increases compliance costs and restricts upward mobility of mses and discourages businesses to register or pay. Anne peslier and colleagues show that olivine components in peridotite xenoliths from the lithosphereasthenosphere boundary region of the kaapvaal craton mantle root are waterpoor, thereby. This plateau is supported by the archean kaapvaal craton and the surrounding proterozoic basement, a suite of rigid basement blocks that controlled basin development throughout the phanerozoic. The redox state of the mantle during and just after core. Siderophile elements in tracing planetary formation and evolution. Thought to be confined to the eastern part of the transvaal subbasin of the kaapvaal craton, the machadodorp member lavas actually extend in the southwestern part of this subbasin. Evidence for mesoproterozoic collision, deep burial and. Earth, the kaapvaal and zimbabwe cratons, and several proterozoic mobile belts surrounding.
Here however, the authors combine seismic analysis with kimberlite data to infer complete destruction of cratonic lithosphere in some places of. Crustal and uppermost mantle structure in southern africa revealed. Read contrasting types of metasomatism in dunite, wehrlite and websterite xenoliths from kimberley, south africa, geochimica et cosmochimica acta on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. The picture that has emerged supports the view that the kaapvaal craton has undergone a prolonged history of crustal evolution and appears to consist of a mosaic of subdomains, now present in the form of small crustal blocks, that were accreted over a time span estimated at between 3. Not only do they record ancient mantle plume activity, but they also are believed to be important building blocks in the formation of the continental crust. The present western edge of the kaapvaal craton and composite kalahari craton is a series of wedge edges composed of archaean kaapvaal rocks and ventersdorp and transvaal basin edges. These form separate continental blocks that have influenced the geological history, scenery and economic potential of the region. Previous isotopic dating in the region suggests an.
Armstrong attended the annual meeting on the kaapvaal craton research group, held in gaberone, botswana, and convened by researchers from mit, carnegie and southern african institutions. Overnight at river view lodge in prieska bb 20 aug 16 satur day windpomp and nouga farms drive to nouga farm, c. The namaqualand metamorphic complex is a wellexposed, mesoproterozoic, lowpressure, amphibolitegranulitefacies terrane flanking the archaean kaapvaal craton of southern africa. The structures are set apart from other ancient microfossils by their complex lenticular morphology combined with their large size and robust, unusually thick walls. To merge recent data on a number of apparently unrelated features, such as plate motion vectors, lithospheric mantle fabrics and preferential mantle melt accumulation within these fabrics, with a view to explaining the mechanism of unusually abundant, geologically instantaneous kimberlite emplacement in the southern africa region. The structural data exhibited by rocks of the palala shear zone provide evidence for the kinematics of this event i. Formation of the craton assuming some form of plate tectonics to have been operative, formation of the nucleus of the kaapvaal craton figure 1 by approximately 3.
Kaapvaal cratons reflects the merging of their subterranes resulting in their. Crustal structure of the kaapvaal craton and its significance. The stable kaapvaal and zimbabwe cratons in southern africa are characterised by the presence of large mafic to ultramafic layered complexes, the best known of which are the great dyke in the zimbabwe craton and the bushveld and molopo complexes in the kaapvaal craton. A reevaluation of archean intracratonic terrane boundaries. Along a narrow zone aligned northeast through the central kalahari and separating the damarankatangan belt in the northwest from the archaean cratons in the southeast magnetic observations indicate that the precambrian basement is depressed to great depths reeves, 1978a. Three possible scenarios are suggested to explain these data. Introduction the bangweulu block forms part of the central african congo craton and is located in between two mesoproterozoic provinces, the kibaran belt to the. It has made up parts of every supercontinent since. Patterns of stress and strain rate in southern africa bird.
It also means that sclm is commonly isolated from the convecting upper mantle. Ti phases are second only to uraninite as the most important uranium minerals in precambrian conglomerates. The foundations of kwazulunatal comprise two distinct geological units, the kaapvaal craton and the natal metamorphic province. Structural control on kimberlite genesis and crustal emplacement within south africa and the kaapvaal craton during the cretaceous. At the present erosion level the country rock in the venetia area appears as a complex arrangement of proterozoic.
Isotopic and geochemical evidence of proterozoic episodic. The geological evolution of africa encyclopedia of life. Merge coeval lip fragments on different cratons into ancient supercontinent reconstructions. Nemchinc, francis tembod a tectonics src, university of western australia, school of earth and geographical sciences, 35 stirling highway, crawley, wa 6009, australia b isotope geology section, africa museum, b3080 tervuren. The archean kaapvaal and zimbabwe cratons form the continental nucleus of southern africa.
Dec 01, 2008 read contrasting types of metasomatism in dunite, wehrlite and websterite xenoliths from kimberley, south africa, geochimica et cosmochimica acta on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Magmatism within the silverton formation of the kaapvaal craton is more widespread and variable than previously considered. The pongola supergroup, located close to the southeastern margin of the kaapvaal craton fig. Unconformity above ventersdorp rocks, basal conglomerates, transition to quartzites, beach and aeolian deposits, transition to carbonates. Diamond genesis and petrology fact sheet by james ware. Sep 30, 2008 after equilibrating with the mantle at the base of the magma ocean, the metallic component of the impactor sinks to merge with the earths protocore without further equilibration. Jelsma encyclopedia of life support systems eolss the worldwide 1. Diamond megaplacers, defined as 50 million carats at 95% gem quality, are known only from along the coast of southwestern africa, fringing the kaapvaal craton, where two are recognized. International journal of economics, commerce and management, united kingdom licensed under creative common page 39 delivering the country. Mesoarchaean and palaeoproterozoic sedimentary sequence stratigraphy of the kaapvaal craton. It is hereby notified that the president has assented to the following act. African cratonic lithosphere carved by mantle plumes nature. The cape and karoo basins represent two largescale episodes of intermittent subsidence and sedimentation within the interior of gondwana figs.
History of granulitefacies metamorphism and crustal growth. Potentially similar forms were reported in 1992 from the \sim3. The picture that has emerged supports the view that the kaapvaal craton has undergone a prolonged history of crustal evolution and appears to consist of a mosaic of subdomains, now present in the form of small crustal blocks, that were accreted over a time span estimated at. The role of micro and small enterprises mses in achieving. As the magmatic system above a plume evolves, it is likely that large magma chambers will develop, which can trap the more primitive, dense and. This in turn demonstrated that portions of the subcontinental lithospheric mantle sclm underlying the kaapvaal craton formed at about the same time as the overlying archean crust, strengthening the then nascent concept of longlived lithospheric keels to continents. Nondweni greenstone belts, and combine data available in the literature with. The qcoda method for estimating the quality factor qf qofn was used to characterize seismic wave attenuation in a region of the kaapvaal craton that includes the mining areas of the bushveld.
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