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This paper explores the interplay between people and a distinctive rural locality namely Vredefort Dome World Heritage Site, South Africa to inform spatial planning guidelines. A transdisciplinary, qualitative research methodology was followed. First, participants’ experiences in relation to the rural landscape were obtained using photographs, interviews and focus groups. Experiences related to physical and emotional safety, relaxation and tranquillity, hope and curiosity, and relational experiences with people and a divinity emerged. Drawing on these interactional experiences, participants (divided into multi-disciplinary groups) made visual collages of how to maintain the sense of place. Guidelines developed included two-dimensional site planning guidelines: (i) a sense of arrival; (ii) development zones; (iii) conservation zones; (iv) compatible land uses; (v) a low density, spatially dispersed development pattern and (vi) footpaths. Three-dimensional design guidelines included: (i) unity in style with a diversity of detail designs; (ii) restricted buildings sizes; (iii) building heights of maximum two storeys; (iv) specified building materials and (v) prescribed colour codes. The paper contributes to existing sense of place research by proposing an integrated, contextual and participatory approach as a possible way forward to make the sense(s) of place explicit by integrating these in spatial planning guidelines. [ABSTRACT FROM PUBLISHER]

We present a compositional and textural analysis of shock-induced microtextures in garnet porphyroblasts in migmatitic garnet-cordierite-biotite paragneisses from the centre of the Vredefort impact structure, South Africa. Detailed imaging and major element analysis of deformation features in, and adjacent to, the garnet porphyroblasts record a complex, heterogeneous distribution of shock effects at the microscale. As the most competent silicate mineral in the assemblage, with the highest Hugoniot Elastic Limit and a wide pressure-temperature stability field, the porphyroblastic garnet preserves a more diverse shock deformation response compared to minerals such as quartz and feldspar, which underwent more comprehensive shock metamorphism and subsequent annealing. The garnet porphyroblasts display pre-impact fractures that are overprinted by later intra-granular Hertzian and distinctive planar fractures associated with the impact event. Shock-induced strain localization occurred along internal slip planes and defects, including pre-existing fractures and inclusion boundaries in the garnet. Symplectitic (kelyphitic) coronas commonly enclose the garnet porphyroblasts, and inhabit intra-granular fractures. The kelyphite assemblage in fractures with open communication beyond garnet grain boundaries is characterized by orthopyroxene-cordierite-sapphirine. Conversely, the kelyphite assemblage in closed-off intra-granular fractures is highly variable, comprising spatially restricted combinations of a secondary garnet phase with a majoritic component, Al-rich orthopyroxene, sapphirine and cordierite. The impedance contrast between garnet porphyroblasts and their inclusions further facilitated the formation of shock-induced features (Al-rich orthopyroxene coronas). Together, the textural and mineralogical data suggest that these features provide a record of oscillatory shock perturbations initiated under confining pressure beneath the transient crater floor. This occurred as the shocked rock volume underwent post-shock expansion, forming the core of the central uplift, and was followed by variable textural re-equilibration. This study thus provides a microtextural and mineralogical perspective of the shock regime within confined crust immediately prior to and during central uplift formation. [ABSTRACT FROM AUTHOR]

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Lithic material recovered from excavations at Holkrans rock shelter, a late Holocene, Later Stone Age site in the Vredefort Dome, South Africa, indicates forager occupation from at least 2000 years ago, and culture contact with farmer groups in the centuries around 1500 AD. A technological analysis of cryptocrystalline silicate (CCS) cores and bladelets indicates marked change in knapping strategy between the pre-ceramic (PC) and ceramic (C) phases, with bipolar knapping of opaline prevalent in the C phase compared to a predominance of freehand knapping on dolomitic chert in the PC phase. The study demonstrates the usefulness of the technological approach as a tool in the study of contact-period LSA lithic assemblages in southern Africa. [ABSTRACT FROM AUTHOR]

Farm workers living in and around the Vredefort Dome World Heritage Site are some of the most vulnerable people in South Africa. Research by means of a case study with four participants from this group examined the following question: How do vulnerable people continue preaching the Word in this environment by ministering to other vulnerable people with the sermons that they have heard? The case study considered both the environment and the circumstances in which these participants live. This research aimed to establish what it means to preach to those who are vulnerable and how such preaching can be continued by the hearers. A case study by means of a qualitative empirical investigation called upon a few of the vulnerable hearers to speak. The findings included that the participants to this case study do not spread the sermons further on a regular basis, but they would be able to edify and encourage other vulnerable persons with it if needed. If they do talk to each other about the sermon directly after the worship service (like it was done during the interviews), their confidence to proclaim the message to other vulnerable people who do not participate in the worship services will increase. [ABSTRACT FROM AUTHOR]

Melting by impact heating is thought to have been a significant process in the modification of early planetary crusts; however, crustally derived melt bodies in ancient terrestrial crust are frequently presumed to be absent due to erosion. Here we demonstrate that in the central basement uplift of the 2.020 Ga Vredefort impact basin (South Africa), components of mafic impact melt have survived amid Archean gneiss as decimeter-scale dikes and lenses of variably foliated gabbronorite. Zircon microstructural, trace element, and isotopic analyses (U-Pb, Lu-Hf) of the gabbronorite reveal a dominant population of 2.02 Ga unshocked igneous zircon with apparent Ti-in-zircon temperatures of 800-900 °C, similar to those from the mafic sublayer of the Sudbury impact melt sheet. Highly negative subchondritic εHf values of 1.4 ± 1.1 to 7.9 ± 1.4 are consistent with a depleted mantle model age of ca. 3 Ga and gabbronorite derivation from the once superjacent Witwatersrand basin lithologies. The recrystallized igneous mineral textures and Archean felsic gneiss inclusions in the gabbronorite are attributable to the effects of emplacement and crater modification following ~20 km elevation of the central uplift. Long mistaken as preimpact basement, the setting and characteristics of the Vredefort gabbronorite may provide new benchmarks in the search for remnants of large cratering events and melt residua on Earth's cratons. [ABSTRACT FROM AUTHOR]

We have determined the major element composition, δ18O and δD values, and water content of impact-related granophyre, and pseudotachylite, from various Vredefort Dome localities, aiming to constrain the mechanism of melt formation and the relationship between pseudotachylite and granophyre. The granitoid gneisses and the pseudotachylites they host have almost identical average δD and δ18O values (-67 and 8.6%0, and -67 and 8.4%o, respectively). The water contents of the pseticlotachylites are extremely low, consistent with the isolation of the pseudotachylites from free water during and since their formation. There is a bimodal distribution of water content in pseudotachylites, with one group averaging 0.28 ± 0.03 weight % (n = 9) and the other 0.59 ± 0.06 weight % (n = 9). The Vredefort granophyre, which has been interpreted as the pooled product of impact melting, has average δD and δ 18O values of -69%0 and 7.6%0, respectively (n = 2) and also has a very low water content (10.23 weight %). Differences in major element and O-isotope composition between the granophyre and the pseudotachylites are not consistent with a simple relationship, but can be explained by a higher component of greenstone in the granophyre. A strong correlation between host and pseudotachylite δ18O values is consistent with a system where the melt composition is controlled by the immediate surroundings. The pseudotachylites with higher water content have slightly higher δ18O values (9.1 compared to 8.1%0). This is opposite to the relationship predicted if water content is related to the proportion of biotite entering the melt. It is possible, instead, that this relates to the incorporation of higher proportions of material altered at low temperature in the high-water group. [ABSTRACT FROM AUTHOR]

Spodumene pegmatites occur in the southeastern sector of the 2.02 Ga Vredefort impact structure in South Africa. Moser et al. (published in 2011) presented an isotope dilution - thermal ionization mass spectrometry (ID-TIMS) age of 1136 ± 47 Ma for these spodumene pegmatites. This discussion questions the reliability of this age. Field relations indicate that the spodumene pegmatites are not affected by the structural fabric that affected the host amphibolites. The crosscutting impact-related veins of pseudotachylitic breccia clearly argues a preimpact age for the spodumene pegmatites. The high-uranium content of one of the two zircons used by Moser et al. to obtain the age is correlated to the ∼1.1 Ga Pb-loss event, widely observed in different rocks within the Vredefort impact structure. [ABSTRACT FROM AUTHOR]

Abstract: The central Vredefort Impact Structure is characterised by impact melt rocks, known as the Vredefort Granophyre dikes, the mode of emplacement of which is not well known. Whole-rock and petrographic analyses of two dikes were conducted and compared to published geochemical data to elucidate the mode and timing of dike formation. The dikes are characterised by compositional and textural heterogeneity between, and within, individual dikes. Specifically, central dike portions are felsic and rich in wall rock fragments, whereas marginal dike phases are more mafic and fragment-poor. Collectively, this suggests that melt was derived from compositionally different parental melts and emplaced in at least two pulses. In addition, the chemical heterogeneity between fragment-rich and fragment-poor dike zones can be explained by variable assimilation of a mafic component, notably Ventersdorp basalt, at the base of the impact melt sheet, from which melt of the Granophyre dikes is derived. This scenario accounts for the mafic and fragment-poor character of melt emplaced first in the dikes and the more felsic and fragment-rich nature of melts of the following emplacement pulse, i.e., when the impact melt was less hot and thus less capable of digesting large quantities of (mafic) wall rock fragments. Differences in geometrical, textural, chemical and fragment characteristics between the Granophyre dikes and pseudotachylite bodies can be explained by the same process, i.e., impact melt drainage, but operating at different times after impact. [Copyright &y& Elsevier]

The aim of this study was to determine the effect of an adventure based experiential learning programme (AEP) in developing the life effectiveness of black high school learners. "Life Effectiveness" reflects the psychological and behavioural aspects of human functioning which determine the proficiency of a person in society. A total of eighty learners (forty boys and forty girls) aged between 12 and 17 years participated in this programme. They were categorized into an experimental (n = 40) and control group (n = 40). The experimental group participated in a five day AEP in the Vredefort Dome in the North-West Province. "The Life Effectiveness Questionnaire" (LEQ-H) was administered before, directly after and six months after the intervention programme to determine the immediate and long term effects of the AEP. Results for total life effectiveness for the short and long term for the experimental group indicated effect sizes of d = 0.03 and d = -0.03, respectively, while for the control group d = 0.12 and d = -0.06 was, respectively obtained. The intergroup results for the experimental and control categories, yielded overall medium effect sizes of d = 0.35 and d = 0.49 over the short and long term respectively, after comparing the adjusted means. The AEP promoted beneficial short and long term changes in the experimental group in contrast to the control category. [ABSTRACT FROM AUTHOR]

Given the substantial growth of whitewater rafting in the Vredefort Dome World Heritage Site (VDWHS), it quickly grew into an unregulated adventure tourism commodity. With the area being a World Heritage Site, concerns have arisen about the impact it could have on the environment, service quality and public safety. As a result, official regulation is certain to take over. In an attempt to demonstrate this industry's significance in terms of its economic, recreation and leisure-related value, this study set out to determine levels of client satisfaction with aspects concerning the operator's choice of pre-trip, transport and catering arrangements, sensitivity towards toilet and trash issues, interest in the preservation of the river's atmosphere, sharing information about the VDWHS and the standard of guiding and equipment used. Additionally, it was determined how important they rated this activity (whitewater rafting) as a reason for their visit to this area. Three hundred and seventy-seven (n=377) questionnaires were completed by the whitewater rafting clients (142 female and 233 male). Results indicated that between 70 and 90 percent of the clients indicated they were either very satisfied or extremely satisfied with all the applicable details. Of the 252 correct cases, 218 of the respondents had whitewater rafting as a reason for visiting this area, of which 60.6 percent rated it as most important. While the operators' professionalism and overall standard of guiding was highest in terms of satisfaction, it is recommended that more emphasis be placed on the preservation of the river's atmosphere as well as the utilization of the natural surroundings in terms of information and interpretation. It is concluded that only through a collaborative effort between the operators themselves and industry associations can this industry be protected, managed and used to its full potential. [ABSTRACT FROM AUTHOR]

The Vredefort Dome World Heritage Site, the largest, oldest and deepest eroded meteorite structure near the town of Parys (Free State Province), offers an almost unlimited range of outdoor and adventurous activities. This area is of exceptional value not only in terms of its geological, cultural and natural attributes, but also because of its recreational potential, which forms a large part of the local tourism industry. Being relatively close to densely populated areas like Johannesburg and Pretoria, whitewater rafting on the Vaal River quickly became most popular in terms of numbers of participants. Operators started to emerge on their own account and, as a result, a need emerged for an appropriate management strategy to protect the client, environment, operators, and to reduce and/or eliminate probabilities of loss. The aim of this study was therefore to develop a management tool. In collaboration with the whitewater rafting operators (n=11) operating on the Vaal River in the Vredefort Dome World Heritage Site, and three knowledgeable and key role players in this industry, the researchers created a self-structured questionnaire with closed and open-ended questions to obtain information about acceptable standards of whitewater rafting practice. The results reveal that not all participants cohere fully to the proposed guidelines. For sustainable adventure tourism, especially for this attraction, it is recommended that the Vredefort Dome World Heritage Site whitewater rafting operators should strive to adopt and apply these guidelines. Clients will continue to seek more challenging adventure experiences and, simultaneously, operators will need to become more professional and proficient. A further recommendation is also to create national standards for all commercial and private operations on South African rivers. [ABSTRACT FROM AUTHOR]

Abstract: Hypotheses proposed to explain the origin of pseudotachylite bodies formed during impact cratering include: (1) frictional heating, (2) shock loading, (3) decompression or (4) drainage of impact melt into target rocks. In order to differentiate among these processes, we conducted detailed geochemical and petrographic analysis of the matrices in pseudotachylitic veins and dikes and of their respective wall rocks. Our analyses indicate that the chemical compositions of matrices locally deviate significantly from their immediate wall rocks and that assimilation of wall rock has substantially modified the pseudotachylite matrix compositions in places. Variable magnitudes of assimilation can be explained by the surface area of wall rock or its fragments in contact with melt, as well as the initial temperature and cooling rate of the pseudotachylitic melt. Chemical trends observed can be explained either by admixture of an exotic melt component with immediate wall rock or by mixing of melts derived from local lithologies. Trends in the compositional deviation of centimetre to metre-wide pseudotachylite dikes from their immediate wall rocks are consistent with the presence of a primary melt component having granitoid composition akin to the average composition of Vredefort Granophyre dikes. Within veins, melt transport can be geochemically and petrographically traced for distances of centimetres to metres, with the direction of melt transport from larger pseudotachylite veins toward smaller ones and into apophyses. Sulphide and silicate mineralogy indicates that the initial temperature of pseudotachylitic melt must have been at least 1200–1700°C. Collectively, these characteristics point to an allochthonous origin of pseudotachylitic melt. We advocate the possibility that impact melt from the initially superheated impact melt sheet contributed to the formation of pseudotachylite bodies at Vredefort. [Copyright &y& Elsevier]

Environmental parameters such as temperature and rainfall influence the biology of amphibians and are likely to similarly influence the growth and prevalence of associated pathogens. Amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), causes an infectious disease, chytridiomycosis, in amphibians worldwide. Field studies on post-metamorphic anurans from tropical Australia have correlated increased prevalence with cool winter temperatures, but similar studies are lacking from Africa. We monitored the seasonality of amphibian chytrid in the Highveld of South Africa through microscopic examination of common river frog (Amietia angolensis) tadpoles over 12 months. Within the study area Bd was found to be widespread, but largely limited to riverine systems. The seasonal infection pattern was inconsistent with the findings of past studies, which showed that prevalence usually peaks during the cooler months of the year. This study indicates that infection levels increased during spring in the Grassland Biome, when temperatures favoured optimum thermal growth of the fungus and when streams reached minimum flow levels. [ABSTRACT FROM AUTHOR]

Integrated electron nanobeam (EBSD, CL, EDS) and isotopic measurements (U-Pb, (U-Th)/He) of zircon from the collar and centre of the 80 km wide central uplift of the 2020 ±3 Ma Vredefort impact structure reveal new shock features in a microstructural progression related to impact basin formation and degree of U-Pb age resetting: (1) planar fractures in {1K0} and {1K2} orientation during initial shock wave compression; (2) curviplanar fractures in {1K1} orientation, now annealed, which host glassy inclusions of partial melt of the host rock; (3) microtwin lamellae in an orientation of 65° about [110], attributed to shock wave rarefaction; (4) nucleation of impact-age crystallites, possibly on microtwins, during post-shock heating by impact melt; and (5) crystal-plastic deformation linked to crater modification of the core of the central uplift. Planar fracturing and microtwinning ≥20 GPa in 'cold shock' zircon in granitoid at a radial distance of 25 km failed to reset zircon age. Single-grain ID-TIMS data extend between pre-impact age of 2077 ±11 Ma and a secondary Pb-loss event at ca. 1.0 Ga - the latter reflecting Kibaran igneous activity between 1.110 and 1.021 Ga. Age resetting by the impact event operated in an ~15 km wide 'hot shock' zone of impact-elevated temperatures ≥700 °C at the core of the central uplift. Mechanisms include internal recrystallization, defect-accelerated Pb diffusion via shock microstructures and melt films, and late crystal-plastic deformation. Igneous zircons from a 2019 ±2 Ma foliated norite impact melt yield a mean (U-Th)/He date of 923 ±61 Ma, indicating exposure of the present surface after this time. Des mesures intégrées de faisceaux électroniques à l'échelle nano (EBSD, CL et EDS) et des mesures (isotopes de U-Pb, (U-Th)/He), sur des zircons provenant du col et du centre du soulèvement central de 80 km de large de la structure d'impact de Vredefort 2020 ±3 Ma, révèlent de nouvelles caractéristiques de choc dans une progression microstructurale reliée à la formation du bassin sous l'impact ainsi qu'au niveau du réajustement de l'âge déterminé par U-Pb : (1) des fractures planaires dans l'orientation {1K0} et {1K2} durant la compression par l'onde de choc initial; (2) des fractures curviplanaires dans l'orientation {1K1}, maintenant recuites, et qui contiennent des inclusions vitreuses de fusion partielle de la roche encaissante; (3) des lamelles de micro-macles selon une orientation de 65 ° environ à [110] attribuées à la décompression de l'onde de choc; (4) la nucléation des cristallites datant de l'impact, possiblement sur des micro-macles, durant l'échauffement après le choc par fusion d'impact et (5) la déformation plastique des cristaux reliée à la modification du cratère du noyau du soulèvement central. La fracturation planaire et le micro-maclage ≥20 GPa dans un zircon de « choc thermique froid » dans un granitoïde à une distance radiale de 25 km n'a pas permis de réajuster l'âge des zircons. Des données ID-TIMS sur des grains uniques se répartissent entre un âge pré-impact de 2077 ±11 Ma et un événement secondaire de perte de Pb vers 1,0 Ga - ce dernier étant le reflet de l'activité ignée de Kibaran entre 1,110 et 1,021 Ga. Le réajustement de l'âge par l'événement d'impact s'est effectué dans une zone d'environ 15 km de large de « choc chaud » de températures élevées causées par l'impact, soit ≥ 700  °C, au cœur du soulèvement central. Les mécanismes comprennent une recristallisation interne, la diffusion, accélérée par des irrégularités, du Pb à travers les microstructures de choc et des films de fusion et la déformation plastique tardive des cristaux. Des zircons ignés provenant de la fusion par impact d'une norite feuilletée datant de 2019 ±2 Ma ont donné une date (U-Th)/He moyenne de 923 ±61 Ma, indiquant une exposition de la présente surface après ce temps. [ABSTRACT FROM AUTHOR]

Surface water resources (the Vaal River and its tributaries) in the Vredefort Dome World Heritage Site (VDWHS), South Africa, have been over extended and future development will rely solely on groundwater. Hence, being at a critical point in the water balance, groundwater resources in the VDWHS require careful management and protection to ensure sustainability and equitable access. An assessment of the geohydrological character of the VDWHS was therefore done in order to develop a groundwater resource management plan. Five groundwater resource management units were delineated and resource measures for each management unit were developed based on physical and anthropogenic attributes. Due to the importance of groundwater in the VDWHS, it was determined that geohydrology should play a major role in the alignment of the environmental, spatial and statutory development frameworks, in order to ensure good governance. A geohydrological-based land use management guideline and spatial development framework was developed to optimize the integration between the water sector, the environmental sector and land use and spatial planning sector. It was concluded that a geohydrological assessment needs to form the basis of all future land use management and spatial planning activities in the VDWHS. [ABSTRACT FROM AUTHOR]

Abstract: Based on detailed structural mapping, geophysical information and structural consideration, we generated a 3D structural model of a segment of the Vredefort Dome. This model provides insight into the mechanism of mass transfer during central uplift formation of large impact structures. The model consists of geometrically and kinematically linked km-scale radial and concentric faults that affected the overturned limb of the rim syncline to the Vredefort Dome. The faults accomplished constrictional (centripetal) rock flow followed by radial spreading of uplifted and gravitationally unstable rocks in the crater centre. More specifically, concentric faults formed likely as normal faults during transient crater rim collapse, steepened and were transformed to reverse faults during central rock uplift and finally, were overturned during gravitational collapse of the central uplift. Radial faults, by contrast, formed at a later stage of convergent rock flow towards the crater centre and retained largely their orientation during central uplift formation. Displacement on individual faults is up to 2 km. Cumulative displacement, notably on concentric faults, can account for the large displacement magnitudes predicted by numerical models. [Copyright &y& Elsevier]

Abstract: Target rocks underlying the central portions of large terrestrial impact structures are characterized by the pervasive presence of fragment-rich pseudotachylite bodies. Debates regarding the formation of these bodies include the origin of pseudotachylitic melts, i.e., friction- versus shock-induced melting, melt mobility, causes of target rock fragmentation, and timing of fragmentation and melt emplacement with respect to stages of cratering. Comprehensive structural analysis of pre-impact mineral fabrics and properties of fragment-rich pseudotachylite in the Vredefort Dome suggests that melt is allochthonous and was emplaced at an advanced stage of cratering into tensional fracture zones within the crater floor. Both concentration of bending strains imparted on target rocks during central uplift formation and thermal stresses induced by the emplacement of allochthonous melt led to fragmentation of target rock. Tensional fracture zones formed in an overall dilational strain field towards the end of cratering, likely during collapse of the central uplift, and constitute low pressure zones, into which melt was forcefully drawn. Melt may have been drained from the overlying impact melt sheet or from sites within the crater floor and transported into fragment-rich dilation zones. Our field-based analysis failed to identify the presence of bona fide shear faults that could potentially have generated in situ frictional melts and fragments. Rather, target rock fragmentation and melt generation that resulted in fragment-rich pseudotachylite bodies are processes separated in space and time during cratering. [Copyright &y& Elsevier]

Since 1916 the Vredefort Dome, the erosional remnant of the central uplift of the Vredefort Impact Structure, has been known as the type locality for what has been known as "pseudotachylite", which can be investigated in this structure at various scales and in a range of different host lithologies. Pseudotachylite sensu stricto is generally regarded as the product of friction melting. The formation of such (or similar) melt breccias in impact structures- known as "pseudotachylitic breccias" - is highly controversial and has been ascribed alternatively to impact (shock compression) melting, friction melting, decompression melting, or various combinations of these processes. In order to contribute to the understanding of the processes that affect the target rock and result in the formation of central uplifts, in general, it is necessary to characterize the impact deformed rocks of the target as well as the impact-generated lithologies. The structures apparent in time rocks of the Vredefort Dome constitute relative time indicators for different stages of deformation during the impact event. Structural analysis of pseudotachylitic breccias and microfractures on a polished 3 x 1.5 m granite slab from a dimension stone quarry in the core of the Vredefort Dome, as well as orientation statistics for microfractures and pseudotachylitic breccias in a quarry in the northern part of the Vredefort Dome form the basis for this investigation. Two microfracture systems are apparent in the granite slab. Fractures of an older system either cross-cut pseudotachylitic breccia or terminate against it, seemingly depending on different cooling times of melt veins of different thickness, This first-formed fracture system is found mostly in the wall rocks to rite breccia veins and in their fragments, whereas a younger fracture system cross-cuts the pseudotachylitic breccias and the host rock. Unravelling the development of individual structural deformation features indicates that the various cross-cutting relationships between pseudotachylitic breccias and two generations of microfractures resulted from a sequence of four processes involving both deformation of the target rock and melt emplacement into the deformed host rock. The first microfracture generation was formed either pre- or syn-impact, pseudotachylitic breccia is syn-impact, and the second microfracture generation is either late-impact or post-impact in age. [ABSTRACT FROM AUTHOR]

Abstract: New paleomagnetic and rock magnetic results are presented for various pre-, syn- and post-impact lithologies from the region of the 2023±4Ma, originally ca. 250km diameter, Vredefort impact structure, on the Kaapvaal Craton of South Africa. After removal of a viscous remanent magnetization (VRM) component, the characteristic remanent magnetization (ChRM) component from 16 Vredefort Granophyre and pseudotachylitic (PT) breccia samples (D =18.3°, I =54.8°, α 95 =8.1°) was isolated and a paleomagnetic pole at 25.1°N and 43.5°E (A 95 =10.6°) obtained. Since, such a ChRM component was isolated also from the Archean Basement rocks of the Vredefort Dome, we consider its nature as a primary component of the impactites proven. The pole falls onto the Paleoproterozoic part of the apparent polar wander path of the Kaapvaal Craton. Rock magnetic analysis and scanning electron microscopy (SEM) revealed that the pseudotachylitic breccia and Granophyre samples contain two distinct magnetite phases: one ultra-small (micrometer-size), and one altered and larger (>50μm) phase. The ultra-small magnetite is interpreted as the carrier of the ChRM and the larger grains as the carriers of the VRM component. Additionally, rock magnetic and petrophysical data reveal unusually high Koenigsberger ratios (Q values) in all pre-impact lithologies, in some Vredefort impactite samples, and in the much younger (1.1Ga) Anna''s Rust Sheet (ARS) gabbro samples. As the high Q values, which had also been reported by previous studies of Vredefort lithologies, are now also seen in samples from the Johannesburg Dome, a direct link to the Vredefort impact can be ruled out. This is also supported by the hysteresis data of this study. As the observed magnetization is rather hard and shows multiple components of remanent magnetization, we exclude lightning as a cause for all observed high Q values (except in case of ARS gabbros). It is instead suggested that the cause of the high Q values could be related to the high temperatures of the rocks that were uplifted by the impact event from a mid-crustal original setting, and to fluid circulation within the two domes that made the rocks vulnerable to acquire high thermochemical remanence. Moreover, paleomagnetic analysis of the rocks around the ARS gabbro intrusion in the northern part of the Vredefort structure revealed the presence of either a shallow north or a shallow south direction, which is tentatively related to emplacement of the Umkondo large igneous province. Analysis of all rocks, including the Vredefort impactites, yields occasionally distinct great circle paths towards these shallow directions. A likely explanation for this overprint direction is the heating caused by now eroded ARS-type gabbro in the area, or by regional, ca. 1.1–1.0Ga orogenic effects. No evidence of Karoo-type (0.18Ga) overprint is seen. [Copyright &y& Elsevier]

Because of its recently acquired world heritage status and the anticipated influx of tourists into the area, the Vredefort Dome World Heritage Site in South Africa is currently experiencing pressure for development. Sudden and radical changes to the spatial environment may have a detrimental effect on local inhabitants who have a long history with the site and who have developed a strong place identity. Intangible aspects, such as the sense of place of an area, are currently not integrated in spatial planning in South Africa. This paper aims to explore personal and symbolic meanings, as part of the sense of place of local inhabitants in the Vredefort Dome World Heritage Site. An interdisciplinary and mixed-method research approach was followed in this study to explore and understand what constitutes a sense of place for local inhabitants in the area. In essence, the qualitative study revealed that inhabitants have a deep and personal relationship with and within the area, which contributes significantly to their sense of emotional security and a strong place identity. The quantitative study indicated how the unique relationship with the environment is concretised into spatial environmental characteristics, areas for development and conservation, and preferences and deficiencies in the built environment. In general, the research found a strong conservation-oriented attitude with regard to the natural rural character of the site, especially in the inner core. Basic guidelines in the form of a spatial planning framework, in which the sense of place is anchored, are proposed in order to strengthen the sense of place of the study area. [ABSTRACT FROM AUTHOR]

The Vredefort impact structure in South Africa is the largest and oldest remnant impact structure on Earth. Observations from above the crater reveal lower than average magnetic field intensities, but the rocks in the crater have been shown to possess much higher magnetic intensities than the regional average that varies on a centimeter scale. Various mechanisms, including the presence of single domain magnetite structures, have been proposed for this anomaly. Mössbauer spectroscopy has been applied to study the Fe-mineralogy of samples from near the centre of the Vredefort crater. Transmission Mössbauer measurements on bulk and microtomics sections of samples showed that the magnetic minerals were magnetite and hematite, and we suggest that oxidation of olivine during the impact is responsible for the magnetic properties of the rocks. [ABSTRACT FROM AUTHOR]

Similarity measures are becoming increasingly commonly used in comparison of multiple datasets from various sources. Semblance filtering compares two datasets on the basis of their phase, as a function of frequency. Semblance analysis based on the Fourier transform suffers from problems associated with that transform, in particular its assumption that the frequency content of the data must not change with time (for time-series data) or location (for data measured as a function of position). To overcome these problems, semblance is calculated here using the continuous wavelet transform. When calculated in this way, semblance analysis allows the local phase relationships between the two datasets to be studied as a function of both scale (or wavelength) and time. Semblance analysis is demonstrated on synthetic datasets and on gravity and aeromagnetic data from the Vredefort Dome, South Africa. Matlab source code is available from the IAMG server at www.iamg.org. [Copyright &y& Elsevier]

Abstract: While most impact craters are characterised by negative magnetic anomalies over their central regions, aeromagnetic surveys over the Vredefort meteorite impact crater reveal multiple concentric magnetic patterns with no significant anomaly at its centre. We performed ground magnetic surveys across a portion of a prominent negative magnetic anomaly that extends in a broad semicircular belt about half way into the basement floor of the crater. Magnetic anomalies defined by our data are most often negative and occur over a wide range of wavelengths. The longest wavelength negative anomaly coincides well with aeromagnetic data. We find that this feature is centred over the amphibolite to granulite metamorphic facies transition exposed in the basement floor. The transition zone is analogous to the Conrad discontinuity, observed at depths of about 20 km elsewhere in the Kaapvaal craton. Petrographic studies show a marked increase in the intensity of the impact-related thermal and shock metamorphism at this transition, which we explain by the focusing and defocusing of shock waves at a rheologic interface during impact. We therefore suggest that the magnetic signature at this boundary is caused by a combination of both thermal and shock effects related to the impact event. A numerical model of the long wavelength anomaly suggests that it is underlain by a body of coherently magnetised rock whose direction and intensity are similar to those found in pseudotachylites and impact melts that formed during impact. On the other hand, negative anomalies occurring over smaller (100 to 20 m) wavelengths often do not coincide with the surface geology. These features cannot be modeled using the same criteria as that for the long wavelength anomaly. [Copyright &y& Elsevier]

The Broodkop shear zone is an approximately 1 km-wide, vertical, northeasterly-trending, mylonitic shear zone that separates upper amphibolite- to granulite-facies gneisses (≥670°C, 4.5 to 5.5 kbar) from mid-greenschist-facies (∼400°C) greenstones in the southeastern part of the Vredefort dome. The mylonitic fabric transposes 3.09 to 3.08 Ga peak-metamorphic migmatitic structures but shows progressive overprinting of shear-related amphibolite-facies assemblages by greenschist-facies assemblages; indicating initiation of deformation close to the metamorphic peak and continued shearing during cooling. Shear-sense indicators are consistent with southeastern-side-up dip-slip movement. Removal of Late Archaean and Proterozoic rotation effects, particularly those associated with formation of the Vredefort dome, suggests that the shear zone formed as a shallowly northwesterly-dipping extensional feature associated with exhumation of the mid-crustal amphibolite-to-granulite-facies footwall rocks and transport of the greenschist-facies hanging wall rocks to the northwest. Several kilometres of throw along the shear zone is suggested by the juxtaposition of rocks with markedly different metamorphic grades. Assuming an initial shallow dip for the shear zone, this suggests in excess of 10 km of dip-slip movement, making the Broodkop shear zone a crustal-scale feature. The timing and geometry of the shear zone suggest that it may represent a mid-crustal manifestation of the rifting event that led to the deposition of bimodal volcanics and associated sediments of the 3074 ± 6 Ma Dominion Group. The Broodkop shear zone provides an appropriate mechanism to explain how these volcanics could be deposited unconformably on mid-crustal gneisses within only a few million years of the high-grade metamorphism. It provides a link between the final major pulse of greenstone-TTG formation in the core of the Vredefort dome and the initiation of a series of large sedimentary and volcanic basins that dominated the Late Archaean history of the Kaapvaal craton. [ABSTRACT FROM AUTHOR]

Identifying and dating large impact structures is challenging, as many of the traditional shock indicator phases can be modified by post-impact processes. Refractory accessory phases, such as zircon, while faithful recorders of shock wave passage, commonly respond with partial U-Pb age resetting during impact events. Titanite is an accessory phase with lower Pb closure temperature than many other robust chronometers, but its potential as indicator and chronometer of impact-related processes remains poorly constrained. In this study, we examined titanite grains from the Sudbury (Ontario, Canada) and Vredefort (South Africa) impact structures, combining quantitative microstructural and U-Pb dating techniques. Titanite grains from both craters host planar microstructures and microtwins that show a common twin-host disorientation relationship of 74° about <102>. In the Vredefort impact structure, the microtwins deformed internally and developed high- and low-angle grain boundaries that resulted in the growth of neoblastic crystallites. U-Pb isotopic dating of magmatic titanite grains with deformation microtwins from the Sudbury impact structure yielded a 207Pb/206Pb age of 1851 ± 12 Ma that records either the shock heating or the crater modification stage of the impact event. The titanite grains from the Vredefort impact structure yielded primarily pre-impact ages recording the cooling of the ultra-high-temperature Ventersdorp event, but domains with microtwins or planar microstructures show evidence of U-Pb isotopic disturbance. Despite that the identified microtwins are not diagnostic of shock-metamorphic processes, our contribution demonstrates that titanite has great potential to inform studies of the terrestrial impact crater record. [ABSTRACT FROM AUTHOR]