Bushveld Research Articles

Goldilocks or Plain Jane? The PGE metallogeny of the Bushveld LIP as recorded by the Rooiberg lavas

Goldilocks or Plain Jane? The PGE metallogeny of the Bushveld LIP as recorded by the Rooiberg lavas

In-vitro screening of Kalahari browse species for rumen methane mitigation

The nutritional value of browse foliage from the Thorny Kalahari Dune Bush veld of South Africa is not characterized. Most of this browse species is rich in tannin, but still palatable, and is consumed by ruminants during the dry season, as well as having a role to play in mitigating enteric methane emission from ruminants. In this study, the rumen methane mitigation potential of 19 browse species foliage collected from the Thorny Kalahari Dune Bush veld, was analyzed in terms of chemical composition, in vitro fermentation, digestibility and methane production. In vitro gas and methane production and organic matter digestibility (IVOMD) were determined by using rumen fluid collected, strained and anaerobically prepared. A semi-automated system was used to measure gas production (GP) from each browse species by incubating 400 mg samples in a shaking incubator at 39 °C with or without inclusion of 400 mg of polyethylene glycol (PEG). Data for all the parameters collected were statistically analyzed using the SAS (9.0) general linear model (GLM) procedure, and differences between foliage species were determined using Duncan’s multiple-range test. Acacia luederitziiand Monechma incanumshowed the best potential for decreasing methane production by up to 90 % after 48 h of incubation. The secondary components (mainly tannins) of the browse species appeared to have a significant effect on volatile fatty acids (VFA), methane and gas production as judged by the comparison of samples incubated with or without PEG inclusion. The substantial amount of crude protein (CP) content coupled with their anti-methanogenic effect during fermentation would make these browses a potential mitigation option for small scale farmers and pastoralists in sub-Sahara Africa. However, it is also very important that systematic and strategic supplementation in a mixed diet should be looked at as the way forward in terms of best utilization.

Chemical control of invasive Psidium guajava in Swaziland: A preliminary assessment of costs and efficacy

Psidium guajava (guava) is recognised as the third most important inva­sive alien plant species in the moist savanna biome of South Africa, Lesotho and Swaziland. The cost of initial clearing of alien plants reaches up to R3 000-00 per ha, therefore the application of correct control methods is essential for cost-effective reduction of the spread. The aim of this study was to test the cost effectiveness of applying various herbicides to guava in the Swaziland Sour Bushveld. Four plots were selected for standing plant treatments, five for cut stump treatments and two for controls. Within each of these plots, five sub-plots were randomly located and the number of plant stems, base diameter, maximum height, and crown diameter was recorded before application of the herbicides. Picloram, fluroxypyr, bromacil, tebuthiuron and imazapyr were used either alone or in combinations. Eleven months after herbicide application, the treated plants were measured again. Bromacil/tebuthiuron liquid soil application gave the best results in terms of cost (0.09 c/stem) for standing plant treatments. The picloram/fluroxypyr cut stump treatment (4.5% concentration) cost the least to apply (0.05 c/stem), and no resprouting was observed. Results from this study can be used as baseline figures for managers planning to control guava. Key words: Alien plant control, herbicides, picloram, fluroxypyr, bromacil, tebuthiuron, imzapyr.

After Africa: Finding Home Again: How I became interested in rangeland management

A llan Savory changed my life. But I didn't realize that until I stepped onto the tarmac of the San Francisco International Airport. As I walked to a 19-minute express flight to Sacramento after 2 days of travel from Johannesburg, South Africa, thoughts of the 2 months I spent in Africa played through my mind like an old film. I couldn't believe it was over. I'd spent a year and a half researching, saving, and planning to get myself to Africa for a Holistic Management internship. All this was because of a soft-spoken man who drank hot tea with lunch, who said graws, not and who over the course of an afternoon interview, planted the idea of healthy, sustainable land in my mind. As the heavy glass door pushed open and I filed out behind other travelers in a neat line to the little plane, I inhaled a deep breath of ocean air. California, at last. Home. But home had changed, too. After the open high veld (rangeland) that borders the Kalahari and the abundant bush veld (filled with impala, kudu, warthogs, mambas, and baboons) that I had walked through just days before, my Sierra Nevada mountain valley home appeared small and a little less alive. The permanent fences crisscrossing the valley stood out like weathered statues against the weak green of the early spring grass. The land looked totally occupied. Before Africa, I saw a picturesque landscape when I looked at the valley: tall grass, thick forests, abundant wildlife, and happy cows grazing the open meadows. But that was only a glance. When I got home I knew how to take a closer look. While studying Holistic Management in Author at age 5 w it a Author at age 5 with lamb.

Modification of cratonic lithosphere by major tectono-magmatic events: implications for the survival of Archaean cratons

The majority of the Sub-Cratonic Lithospheric Mantle (SCLM) has been shown to be of Archaean age (Pearson, 1999). This implies that the SCLM plays a fundamental control in stabilizing and preserving overlying continental crust and isolating significant volumes of mantle from the convecting asthenosphere (Jordan, 1988). It is clear from the consideration of accretion models that, over time, Archaean crust has been destroyed or modified by erosion and/or major tectono-magmatic events. Determining the processes that have modified the CLM is therefore fundamental to our understanding of the evolution of continental crust and the mantle. The aim of this project is to understand the factors/ processes that have led to the local preservation/destruction of Archaean continents. For this reason CLM xenoliths suites will be examined from two geodynamic settings that have been subjected to major tectono-magmatic events. One craton survives (Bushveld Province) while the other becomes rifted (Tanzania). In Kaapvaal craton, recent geophysical and petrological studies show a large anomaly beneath Premier, a region affected by 2.05 Ga Bushveld magmatism. The 1.2 Ga Premier pipe provides a natural probe of the mantle in this area. Later, Northern Tanzania xenoliths will be studied as they are from a region where an Archaean craton (Chesley et al., 1999) is actively rifting. These xenoliths will provide information on how SCLM is modified by magmatic and metasomatic events before a craton no longer acts as a stable continental core. To assess if differences between these two tectonic settings are the result of SCLM modification, we need to understand what percentage of the SCLM has been modified by what processes and the changes with time. Our approach consists of petrology, major and trace element, and multi-isotope studies related to detailed spatial sampling of mineral domains. Whole rock and Re-Os analyses will provide strong mass balance constraints on compositions and ages of the CLM at different depths. Petrology studies will allow calculation of pressure corrected xenoliths densities. Because P estimates can be used to constrain the depth of origin of xenoliths, we can therefore assess the extent to which the CLM has been modified at different depths and then model the predicted thermal and mechanical response of the craton. Whole rock and mineral compositional data will be presented from Premier, allowing an estimate of composition with depth. Preliminary Re-Os, PGE and trace elements in minerals from the first part of the suite will be discussed. Isotopic analysis will be initiated later this year.

Cross-cultural aspects of depression in general practice.

It was previously thought that black Africans from traditional cultures rarely suffered from what in the West is classified as depression. The word ‘fatalistic’ was often used to describe what was assumed to be a lack of emotion or feeling. It is being increasingly discovered by psycholinguistic and psychological research that depression in black Africans is underdiagnosed as it presents in different ways of living and interacting as well as from a different existential dimension and world view. From a constellation of symptoms and signs, the West has developed a concept and label of depression that fits and suits Western culture. Traditional African culture has not concretised or labelled this concept yet so that it remains diffuse and undifferentiated. It may present with different linguistic phrases, metaphors of life and symbolic language and often as a story that attempts to express the complex realities of life. An exploration into these stories (and other mediums such as song, theatre, poetry and literature) may reveal that depression is as common among black Africans as it is in the West, but that it is unrecognised and underdiagnosed. How does one diagnose depression in a Zulu patient who comes down from the villages of Hlatikhulu or Ntabamhlophe in the mountains, or from Msinga and Nkandla in the low bushveld? It is a meeting between two worlds of different experience, meaning, language and culture. The patient works within the experience of his or her social and cultural life whereas the doctor works within the criteria laid down by the Diagnostic and Statistical Manual-IV (DSM-IV) 1 and has a list of symptoms that have to be fulfilled before the diagnosis can be made. These symptoms and references are derived from both a biomedical perspective and the doctor’s own experience of living in the Western world. The doctor’s language and even grammar are technologically based. We have now classified almost every activity that human beings are capable of and are busy with subsets and smaller boxes, into which human behaviour can be fitted. When we encounter a traditional African culture that is not informed in this way and that experiences illness differently, we are often at a loss as how to assess, diagnose and treat such patients. For instance, traditional rural Africans may not differentiate their cognitive functions from their bodily functions and symptoms. Their dreams, visions, feelings and inner thoughts are not separated from their bodily symptoms of illness. There is no dichotomy between the spirit or soul and the body. 2

PRELIMINARY RE-OS ISOTOPIC DATA IN PGE RICH CHROMITITE LAYERS OF LUANGA ULTRAMAFIC LAYERED INTRUSION – CARAJAS (PARÀ STATE), BRAZIL

The Luanga layered complex intruded a greenstone belt sequence (Rio Novo Formation) at 2760 Ma (Rb-Sr radiometric dating; Suita and Nilson, 1991). This age is confirmed by relationships with the Lower Proterozoic age of the covering sequence (Salobo and Rio Fresco Units). Lithostratigraphic data based on outcrops and three drillholes confirm the layered nature of the intrusion made up of dunite, peridotite, pyroxenite, norite and gabbro layers from the bottom to the top. Chromitite layers and seams, occur in three well defined horizons located in plagioclase pyroxenites and at the transition zone between dunite and peridotite. The massive chromitite layers show thicknesses between 2 m and a few centimetres. The massive chromitite displays an equigranular texture, with single grains ranging from 0.5 to 2 mm in size. The fresh chromitite layers show: atoll-like texture with olivine and orthopyroxene inside and outside chromite rings, pseudomyrmekitic intergrowth of silicates and chromite. Relationships of the two dominant PGMs (braggite and sperrylite) with the silicates and chromite suggest that PGM crystallization predates the almost contemporaneous precipitation of silicates and chromite. Weathering processes changed only in part the primary composition and mineralogy of the chromitite, for this reason it was possible to select well preserved primary minerals and mineral assemblages for analyses with microprobe, fire assay and neutron activation and mass spectrometry. The chemistry of the chromitite layers is typical of chromites generated by fractionation and cumulus processes, with widely ranging, but generally high Al2O3 and low Cr2O3 contents. PGE chondritic profiles display a PPGE enrichment in all the three horizons (Table 1), (Diella et al., 1995). Preliminary Re–Os isotopic data were obtained on two selected massive chromitite samples from the PGE richer (Lu3) and the relatively PGE poorer (Lu 6) chromitite horizons. These two samples show respectively the highest and the lowest PGE contents of all data collected. Isotopic analyses were performed with the Carius tube isotope dilution procedure, using the PGE standard “WPR- 1” provided by the Canadian Certified Reference Materials Project. Isotopic data (Table 2), in form of 187Os/188Os, were transformed into 187Os/186Os by using a 188Os/186Os ratio of 8,302 (Luck and Allegre, 1983). Initial 187Os/186Os ratios and gOs were determined by considering an age of emplacement of Luanga complex at 2700 Ma. Reliabilty of data is confirmed by very low 2s values for both samples. Isotopic analyses were performed with the Carius tube isotope dilution procedure, using the PGE standard “WPR- 1” provided by the Canadian Certified Reference Materials Project. Isotopic data, in form of 187Os/188Os, were transformed into 187Os/186Os by using a 188Os/186Os ratio of 8,302 (Luck and Allegre, 1983). Initial 187Os/186Os ratios and gOs were determined by considering an age of emplacement of Luanga complex at 2700 Ma. Reliability of data is confirmed by very low 2s values for both samples. Our data were compared with those of other chromitites from layered complexes as Stillwater (A, B, G, I, K chromitites; Marcantonio et al., 1993) and Bushveld (UG1, UG2 chromitites; Hulbert and Gregoire, 1993) and PGE-rich Merensky Reef of Bushveld (Fig. 1). Luanga chromitites show high ratios, similar to those of Merensky Reef, and much higher than CHUR at 2700 Ma. It is possible to state that the mantle-melt system at Luanga underwent some modification and cannot be thought as due to a process of melting of a primary fertile undisturbed mantle. At this stage different processes able to increase (187Os/186Os)i can be envisaged: anomaly in the source due to the presence of a metasomatized mantle, strong differentiation during fractionation or crustal contamination.

Control of heartwater in cattle in Southern Africa using terramycin/LA

Heartwater is a fatal disease of cattle, sheep and goats in tropical and sub-tropical parts of the world, particularly Africa. The disease is due to infection with the rickettsia Cowdria ruminantium , which is transmitted by certain ixodid ticks of the genus Amblyomma . The disease is limited, therefore, to the geographical limits of distribution of these ticks. Diagnosis is difficult because there are no obvious stages circulating in the blood of infected animals and the principal area of proliferation and pathogenesis of the organisms is in the capillary blood vessels of the brain. The resultant brain damage causes characteristic nervous symptoms such as an un-natural high-stepping gait but positive diagnosis is usually obtained by examination of Giemsa-stained smears of cerebral cortex. Recently an indirect fluorescent antibody serologic test has been developed in South Africa and this will give the first opportunity to assess the epidemiology of the disease and to conduct meaningful experiments on immunisation. It is anticipated that the geographical limits of the disease will prove to be much broader than has been thought so far. There are two distinct parts of the paper to be presented. In the first part a review will be made of the occurrence and distribution of the Amblyomma species known to be vectors of heartwater in southern Africa (below 10°S). The information used in this review is supplied by scientists resident in each country. Heartwater is thought to be widespread in all southern African countries except Namibia, which is too dry to support Amblyomma ticks. In the other countries the vector ticks are most often concentrated in low-lying bush veld and along river valleys. In Malawi and Madagascar Amblyomma variegatum is recognised as the exclusive vector of heartwater since A.hebraeum and A.pomposum are absent. In South Africa A.hebraeum is the only major vector species present. In the second part of the paper the control of heartwater using TERRAMYCIN/LA will be discussed. Tetracyclines are almost invariably used for the treatment of heartwater, and of these TERRAMYCIN/LA as an intramuscular injection or Liquamycin 100 given intravenously have wide acceptance. There are two particular field situations in which cattle are prone to heartwater - either when young home-bred calves are subjected to heavy Amblyomma tick challenge at the start of the spring rains or when susceptible young animals are introduced onto a farm where heartwater is endemic. In each situation the possibility exists that the use of a short series of injections of TERRAMYCIN/LA to provide cover against frank disease during the critical first month of exposure to ticks may render the cattle immune to subsequent challenge without having undergone the trauma of a disease episode and therapy. The results of preliminary field trials to investigate this possibility are presented in this paper.

Reënvalonderskeppingsverlies In ’N Stand Van Suuragtige Gemengde Bosveld

Abstract Loss of water by interception during spells of rain is surveyed on an unorthodox experimental plot in a stand of mixed bush veld vegetation. The variables influencing interception loss are analysed. Net rainfall is assessed, and it found that an appreciable quantity of water during every storm is lost as a result of evaporation from, the vegetative cover. Apart from the density of the vegetation, this loss is influenced particularly by the duration and frequency of the precipitation, to such an extent that interception loss, for storms comparable in volume, differs by more than 200 percent.

Spectrographic and X-ray data on some fluorites from the Transvaal, South Africa

The fluorites of the Transvaal occur in different rock-types, viz in the dolomite of the Transvaal System, in acidic rocks (red granite and granophyre of the Bushveld igneous complex and Rooiberg felsites), and in alkalic rocks. The purpose of this study was to determine:(1) What minor elements are present in selected fluorites.(2) What the effect of these elements is on the respective cube-edges.(3) Whether these elements have any geological significance.Fluorite displays a wide range of colour; both colourless and distinctly coloured specimens were examined. Differently coloured varieties could in some instances be taken from the same sample. The choice of coloured varieties in the different rock-types was nevertheless limited. Only light-coloured fluorites occur in the dolomite, whereas the alkalic rocks yielded only very dark purple specimens.

4. ONE YEAR'S CENSUS AND STUDY OF BIRDS IN 2½ ACRES OF ALEANY BUSHVELD. (Part 2.) April, 1945, to March, 1946

(1947). 4. ONE YEAR'S CENSUS AND STUDY OF BIRDS IN 2½ ACRES OF ALEANY BUSHVELD. (Part 2.) April, 1945, to March, 1946. Ostrich: Vol. 18, No. 2, pp. 155-165.

The Economic Geography of Swaziland

arose once again in the Press concerning the South African Protectorates, and the question of their transfer to the Union. I know little of conditions in either Basutoland or Bechuanaland, but I would like to bring forward some aspects of the geography of Swaziland, in the hope that they may perhaps serve to clarify the issue, at least where this Protectorate is concerned. The territory is about the size of Wales, and since I cannot hope to deal with all the problems, I propose to survey briefly the physical geography and historical development of Swaziland in relation to its economic development. It is this economic aspect which is likely to figure most prominently if and when terms for the transfer of the Protectorate to the Union are drawn up. Swaziland lies about 3 degrees south of the Tropic of Capricorn. On travelling through or flying over the country one is struck by the four welldefined topographical units into which the region falls. These physical divisions are determined mainly by geological structure, and themselves give rise to variations in the natural vegetation. Firstly, in the west the rim of much dissected mountainous country varying from 4000 to 6000 feet above sea-level is known as the high veld. Secondly, east of the high veld there is a perceptible drop into the deep valleys of the broken, rolling middle veld, which lies between 4000 and 1500 feet above the sea. This region is transitional to the third division, the low veld, which stretches eastward, a monotonous practically level plain across which thorn and bush dominate the landscape; this region is sometimes termed the bush veld. This last area varies from 800 to 2ooo feet above sea-level, while its continuity towards the sea is broken by the fourth division, the sheer face of the Lebombo rising abruptly from the bush-clad flats to 2500-3000 feet above the sea and forming a continuous range along the eastern boundary of Swaziland, breached only by the narrow but conspicuous gorges worn by the rivers, practically all of which drain eastward to Delagoa Bay. The rivers differ from most South African rivers in one respect which is of great importance-the main Swaziland rivers are perennial, and only those tributaries which rise within the bush veld dwindle to a string of muddy puddles during the dry season (Map i). From the geological map it appears that most of Swaziland is built of ancient granitic rocks (Map 2). Since very little is known concerning the geology I do not claim that this map is accurate. The mountainous region on the northwest border is a geological unit, and although the old rocks do not all lie within Swaziland, it is convenient to discuss the mountainland as a whole. From the map one can trace the relationship of the Barberton mountainland to the geology of the surrounding areas. It is a fragment of a series of sedimentary strata, presumably Pre-Cambrian in age, surrounded by the Old Granites, which cover immense areas in Southern Africa. The Pre-Cambrian beds reappear in the south of Swaziland. The Barberton mountainland is a most important physiographic element, for it has a marked influence on