Covering approximately (57%) of the country's surface area the main basin of the geology of the Karoo Supergroup in South Africa has an important influence on the materials used in the construction of transport infrastructure in South Africa. The Karoo Dolerite Suite often serves as the only competent material in this otherwise sedimentary basin but on numerous occasions rapid premature failures of pavements constructed with Karoo Dolerite base courses have been attributed to the poor durability of these materials. The research presented here attempts to determine if the cause of such rapid failures can be attributed to dolerite durability deficiencies and if so if the durability of the material can be predicted using the current specifications to which these materials are required to conform with. The methodology followed was to perform comprehensive material investigations on selected pavement sections where Karoo Dolerite had been used as a base course aggregate. Eight suitable sites, ranging in age from two months to 10 years, were selected and comparative testing performed on samples of material obtained from the source quarries and pavement layers at each. Three of these sites experienced rapid failure that was suspected to be due to base course aggregate degradation. The tests performed included those specified by South African standards and a selection of new tests derived from published literature on alternative tests and proposed basic igneous rock degradation models. Well established tests were completed with relative ease while newer tests and newly proposed tests required additional development. The materials from at least two poor performance sites was shown to have undergone various degrees of degradation after quarrying which manifested itself primarily as a loss in resistance to attrition and abrasion forces. The variability in the inherent resistance of the material to these forces was also noted to have contributed to the poor performance of at least two sites. It is therefore proven that degradation of Karoo Dolerites after quarrying can occur and contribute to the poor performance of pavements but also that the variability in a source quarry can result in poor performance without material degradation. The prediction of material durability is possible but requires numerous tests to be performed on representative samples, particularly to identify variations in material properties. Petrographic properties that result in variable material properties and a susceptibility to further alteration included high degrees of deuteric and metasomatic alteration of primary minerals, especially the fine matrix minerals. It has been shown that the accurate quantification of such alteration is not feasible using easily available analysis techniques and therefore that no specifications can be based thereon. The current material specifications have been shown to not accurately predict the durability of Karoo Dolerite, primarily due to the inability to activate the mechanism by which material physical degradation occurs, namely the expansion of clay minerals within the aggregate. The only exception was the water absorption test performed on core samples, which was able to identify poor materials. Tests that were able to predict the durability included the modified versions of previously specified tests (e.g. ethylene glycol soaked aggregate impact value and ethylene glycol soaked modified durability mill index) and newly proposed testing methods (e.g. modified ethylene glycol durability index and shear wave velocity). Preliminary specifications for these have been proposed. The initial development of an aggregate expansion test has also shown a strong ability to predict Karoo Dolerite durability and is proposed for further development. Ultimately the use of poor durability Karoo Dolerite results in two changes in the material properties. The first effect is the production of more fines during construction, which can result in an unsuitable amount of fines (as identified by a low coarse sand ratio). The second effect is an increase in plasticity index and linear shrinkage of the material<0.425mm to levels considered marginal based on the current specifications. The shear strength of a Karoo Dolerite base course layer has been shown to be sensitive to such changes in plasticity index and linear shrinkage and the reduction of the current specification limit to ensure materials are non-plastic and/or non-expansive may therefore be justified.

The coalfields of South Africa contain numerous dolerite intrusions, which are believed to have affected the quality of the surrounding coal by a thermal process, controlled by the size of the magmatic body. Data gathered from a working coalfield in Secunda, South Africa, suggest that the relationship between intrusive sills and coal is complex and factors other than intrusion width must be considered in relation to the contact metamorphic effect. The study area contains multiple dolerite intrusions of Karoo age, separated according to their geometric relationship to the local coal seams. Three intrusions were selected for detailed study. The three dolerite bodies, namely the DO4, DO8 and DO10 dolerites, occur as sills intruded close to the main coal seam of the area. The dolerite sills have identical mineralogy and can only be distinguished through textural variations in thin section. Coal quality data was obtained from Sasol Mining Secunda and used to investigate the presence or absence of a change in coal quality relative to dolerite proximity. Reduction in coal quality was defined using three main proximate analysis values, termed Ash, Volatile content (Vols) and Dry Ash Free Volatile (DAFV) in the coal industry. These parameters were used to determine the extent of any effect deleterious to coal quality induced by the intrusion of the dolerite sills. The resultant investigation showed no correlation between the position and thickness of the dolerites, and a change in coal quality (as measured by proximate analysis). In the absence of a linear relationship between coal quality and dolerite proximity, two processes are proposed to explain the absence of the contact metamorphic effects expected from previous studies: -Dolerite emplacement dynamics may influence the size of the metamorphic aureole produced by an intrusion, and invalidating intrusion size as a measure of thermal output, - Hydrothermal fluids mobilised by the dolerite intrusions, either from the country rock or the intrusion itself may percolate through the coal and act as the metamorphic agent responsible for changing coal quality, by dissolving the volatile components of the coal and transporting them to other locations These two processes are sufficient to explain the lack of a clear “metamorphic effect” related to the dolerite intrusions. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Geology / unrestricted

<p>The chief aim of this project is to investigate the groundwater flow dynamics of the various fractured-rock aquifers (deep and shallow) associated with Karoo dolerite ring complexes in the Qoqodala area (northeast of Queenstown in the Eastern Cape Province).</p>

<p>The chief aim of this project is to investigate the groundwater flow dynamics of the various fractured-rock aquifers (deep and shallow) associated with Karoo dolerite ring complexes in the Qoqodala area (northeast of Queenstown in the Eastern Cape Province).</p>

Magister Scientiae - MSc / The chief aim of this project is to investigate the groundwater flow dynamics of the various fractured-rock aquifers (deep and shallow) associated with Karoo dolerite ring complexes in the Qoqodala area (northeast of Queenstown in the Eastern Cape Province). / South Africa

During drilling at Borg, ca. 5 km southwest of central Norrköping, an unidentified fine-grained grey rock was encountered in contact with dark red granitic gneiss at 35m depth. The fine-grained grey rock occurs above the red granitic gneiss. Our understanding prior to testing is that the rock may have been formed by fluid alteration of a mafic rock, as neither metamorphic nor sedimentary textures were observed. Understanding this rock and the formation processes related to it, is of interest for the general understanding of the region and of geotechnical importance since fracture fillings may affect the stability of the rock during and after construction projects. This study uses the methods petrography, XRD and XRF to define the fine-grained mafic rock, black vein in the fine-grained mafic rock, the contact zone and the granitic gneiss. Results show that the fine-grained grey rock has a composition of muscovite (36.1%), quartz (24.6%), albite (20.8%), sericite (10.8) and montmorillonite (0.5%). The contact is mainly made of quartz veins and calcite veins. The protolith of the fine-grained mafic rock is suggested to be iron-rich. Further testing on additional unaltered mafic rock samples from the area would provide a more accurate picture of the protolith evolution.

No description available.