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Http Dx Doi Org 10 1080 00357529 2014 842840, Dec 9, 2013
The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrus... more The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrusions was evaluated through rock magnetic analysis on samples from borehole G39974 from the Kopoasfontein farm in the Calvinia district. The borehole intersected rocks from the Ecca Group as well as three dolerite sills of varying thicknesses. The variation of magnetic susceptibility with depth (Fig. 1a) succesfully distinguishes between the different stratigraphic units intersected in the borehole. Both low field anisotropy of magnetic susceptibility (LFAMS) (Fig. 1b) and magnetostratigraphy data (Fig. 1 c) are relatively constant with depth, showing significant change only at sill-sediment contacts. This suggests that the re-magnetization of magnetic fabric is restricted to short distances from the sill contacts as was previously reported by De Kock and Kirschvink (2004). Alteration index (A40) data (Fig. 1d) indicate maximum acquired temperatures for the sedimentary units ranging betwe...
The viability of using magnetic fabric analyses as geothermometers in sedimentary basins was inve... more The viability of using magnetic fabric analyses as geothermometers in sedimentary basins was investigated and new constraints on regional-scale geotherms for the Karoo sedimentary Basin were identified. A comparative study of the variation in magnetic properties in eight boreholes located along a southwest to northeast traverse across the Karoo Basin was performed. The thermal impact of the intrusive Karoo Dolerite Suite on the surrounding sediments was determined using several magnetic experiments. The methods employed during the investigation include low field anisotropy of magnetic susceptibility, variation in magneto-stratigraphy using the classic baked contact test, the magnetic Alteration Index (A40) as well as looking at the possibility to use magnetite-pyrrhotite geothermometry. The experiments indicated the heating effect of the dolerite intrusions to be limited to short distances within the contact aureole. Boreholes that intersected dolerite sills indicated that the heati...
The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrus... more The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrusions (Karoo LIP) was evaluated through rock magnetic analysis on core samples from borehole G39974 in the Calvinia district. The borehole intersected rocks from the Ecca Group as well as three dolerite sills of varying thicknesses. The variation of magnetic susceptibility with depth succesfully distinguishes between the different stratigraphic units in the borehole. Both low field anisotropy of magnetic susceptibility (LAMS) and magnetostratigraphy data are relatively constant with depth, showing significant change only at sill-sediment contacts. This suggests that the re-magnetization of magnetic fabric is restricted to short distances from the sill contacts. Alteration index (A40) data indicate maximum acquired temperatures for the sedimentary units ranging between 200°C and 650°C with the highest temperatures restricted to short distances within the contact aureoles. These elevated ge...
ABSTRACT Thesis (Ph. D.)--University of the Witwatersrand, Johannesburg, 1986. Includes bibliogra... more ABSTRACT Thesis (Ph. D.)--University of the Witwatersrand, Johannesburg, 1986. Includes bibliographical references (leaves 207-232).
Http Dx Doi Org 10 1080 00357529 2014 842840, Dec 9, 2013
The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrus... more The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrusions was evaluated through rock magnetic analysis on samples from borehole G39974 from the Kopoasfontein farm in the Calvinia district. The borehole intersected rocks from the Ecca Group as well as three dolerite sills of varying thicknesses. The variation of magnetic susceptibility with depth (Fig. 1a) succesfully distinguishes between the different stratigraphic units intersected in the borehole. Both low field anisotropy of magnetic susceptibility (LFAMS) (Fig. 1b) and magnetostratigraphy data (Fig. 1 c) are relatively constant with depth, showing significant change only at sill-sediment contacts. This suggests that the re-magnetization of magnetic fabric is restricted to short distances from the sill contacts as was previously reported by De Kock and Kirschvink (2004). Alteration index (A40) data (Fig. 1d) indicate maximum acquired temperatures for the sedimentary units ranging betwe...
The viability of using magnetic fabric analyses as geothermometers in sedimentary basins was inve... more The viability of using magnetic fabric analyses as geothermometers in sedimentary basins was investigated and new constraints on regional-scale geotherms for the Karoo sedimentary Basin were identified. A comparative study of the variation in magnetic properties in eight boreholes located along a southwest to northeast traverse across the Karoo Basin was performed. The thermal impact of the intrusive Karoo Dolerite Suite on the surrounding sediments was determined using several magnetic experiments. The methods employed during the investigation include low field anisotropy of magnetic susceptibility, variation in magneto-stratigraphy using the classic baked contact test, the magnetic Alteration Index (A40) as well as looking at the possibility to use magnetite-pyrrhotite geothermometry. The experiments indicated the heating effect of the dolerite intrusions to be limited to short distances within the contact aureole. Boreholes that intersected dolerite sills indicated that the heati...
The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrus... more The geothermal history of the western Karoo Basin with respect to the large scale dolerite intrusions (Karoo LIP) was evaluated through rock magnetic analysis on core samples from borehole G39974 in the Calvinia district. The borehole intersected rocks from the Ecca Group as well as three dolerite sills of varying thicknesses. The variation of magnetic susceptibility with depth succesfully distinguishes between the different stratigraphic units in the borehole. Both low field anisotropy of magnetic susceptibility (LAMS) and magnetostratigraphy data are relatively constant with depth, showing significant change only at sill-sediment contacts. This suggests that the re-magnetization of magnetic fabric is restricted to short distances from the sill contacts. Alteration index (A40) data indicate maximum acquired temperatures for the sedimentary units ranging between 200°C and 650°C with the highest temperatures restricted to short distances within the contact aureoles. These elevated ge...
ABSTRACT Thesis (Ph. D.)--University of the Witwatersrand, Johannesburg, 1986. Includes bibliogra... more ABSTRACT Thesis (Ph. D.)--University of the Witwatersrand, Johannesburg, 1986. Includes bibliographical references (leaves 207-232).