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Platinum exploration on the Great Dyke of Zimbabwe
222A
SITE 1NVESTIGATIONS:REMOTESENSING
955161 Probability analysis and its application in classification of rock masses in the workings (in Chinese) Gao Qian, Ren Tiangui & Ming Shixiang, Journal of China Coal Society, 19(2), 1994, pp 131-139. A probability analysis is proposed taking into consideration the uncertainty of factors for classification of rock masses on the basis of geomechanical classification. The paper describes the standards for quantitative analysis of all the factors for classification, and criteria for modifying classification indices. A method for determining rock strength and deformation parameters is investigated based on rock masses classification indices. Its application in the western area of Xiaoguanxlmang iron mine shows that it can be applied in practice. (from English summary)
IN SITU STRESS
Causes and nature of in situ stress
955162 Tbe effect of a devlatoric stress on physical rock properties. An experimental stady simulating tbe in-situ stress field at the KTB drllllng site, Germany H. Kern, T. Popp & R. Schmidt, Surveys in Geophysics, 15(5), 1994, pp 467-479. Petrophysical measurements were carried out on dry specimens of mica-gneiss, amphibolite and serpentinite from KTB core samples and samples of surface oucrops in or&r to determine the effect that a deviatoric stress field, as observed at the KTB area, may have on the in-situ rock properties. Simulating the variation of the actual principal stresses and temperature with depth, seismic wave velocities, densities, linear and volumetric strain (porosity) have been measured. Comparison with data evaluated for lithostatic pressure conditions revealed that the stress-related effect on wave velocities is in the range of l-3%, due to microcracks which are selectively closed or kept open by the deviatoric stress. The effect of the deviatoric stress is particularly documented by shear wave splitting due to microfractures that are oriented normal to the minimum principal stress axis. (from Authors)
Measurement of in situ stress
955163 Integrated stress determination by joint inversion of hydraulic tests and focal mechanisms J. M. Yin & F. H. Comet, Geophysical Research Letters, 21(24), 1994, pp 2645-2648. An inversion method, based on a genetic algorithm, is proposed for interpreting jointly various kinds of stress data in order to overcome the limitation, in number and quality, of each data set. The method has been applied to results from hydraulic tests in boreholes and to focal mechanisms of induced seismicity observed within the same depth interval. This inversion confirms previous results suggesting that the regional stress field cannot be determined solely from an inversion of the fault plane solutions. (from Authors)
SITE INVESTIGATION AND FIELD OBSERVATION General 955164 Analysis and management of financial risks arising from ground conditions 1. L. Whyte, Transactions - Institution of Mining & Metallurgy. Section A, 104(Jan-April), 1995, pp A34-A40. The financial benefits of adequate site investigation can be demonstrated by risk modelling, and such an approach is described for a tunnelling scheme. Two models are outlined: the first analyses the effect of uncertainty in ground conditions on planning estimates of project cost and duration; and the second models the financial consequences of encountering unforeseen conditions during construction. Results are shown to be realistic when compared to the prototype event. A strategy is proposed for the management of ground risk that relates the level of investigation to the complexity and degree of risk in a project. (Author) 955165 Platinum exploration on the Great Dyke of Zimbabwe D9J3F;wen, Exploration & Mining Geology, 3(4), 1994, pp . The Great Dyke extends for 540 km along strike, to unknown depth, and varies in width from 3 km to 11 km. Rb/Sr age determinations gives values of approximately 2470 Ma. The Dyke consists of a variety of matic and ultramafic rocks, many altered to serpent&es. Vast mineral resources exist. These include chrome, asbestos, platinoids, nickel, copper and gold. Up to eleven chrome seams numbered from top to bottom occur in the lower ultramaflc sequences. Seams are narrow at 10 cm to 30 cm but of high grade. The platinum occurs 10 m to 40 m below the norite/pyroxenite contact. Extensive exploration programs have been carried out and the intention is to begin large-scale mining. (from Author)
Remote sensing and photographic techniques 955166 Mineral identification and mapping of hydrothermal alteration zones using high-spectral resolution images (AVIRIS) F. D. Van der Meer, ITC Journal, 1994-2, 1994, pp 145-154. High-spectral resolution images (AVIRIS) of the cuprite mining area were used to evaluate atmospheric calibration algorithms and test several mineral mapping techniques. Four scene normalization techniques were used: 1) the flat-field method. 2) the internal average reflectance method , 3) the empirical tine method, and 4) the atmospheric absorption removal method (ATREM). The algorithms were evaluated in terms of their spectral interpretability and their ability to remove both solar irradiance and atmospheric absorption features, noise and artifacts. (from Author) 955167 Calibration of airborne visible/infrared imaging spectrometer data (AVIRIS) to reflectance and mineral mapping in hydrothermal alteration zones: an example from the ‘Cuprite mining district’ F. Van der Meer, Geocarto International, 9(3), 1994, pp 2337.
SITE 1NVESTIGATIONS:REMOTESENSING
955161 Probability analysis and its application in classification of rock masses in the workings (in Chinese) Gao Qian, Ren Tiangui & Ming Shixiang, Journal of China Coal Society, 19(2), 1994, pp 131-139. A probability analysis is proposed taking into consideration the uncertainty of factors for classification of rock masses on the basis of geomechanical classification. The paper describes the standards for quantitative analysis of all the factors for classification, and criteria for modifying classification indices. A method for determining rock strength and deformation parameters is investigated based on rock masses classification indices. Its application in the western area of Xiaoguanxlmang iron mine shows that it can be applied in practice. (from English summary)
IN SITU STRESS
Causes and nature of in situ stress
955162 Tbe effect of a devlatoric stress on physical rock properties. An experimental stady simulating tbe in-situ stress field at the KTB drllllng site, Germany H. Kern, T. Popp & R. Schmidt, Surveys in Geophysics, 15(5), 1994, pp 467-479. Petrophysical measurements were carried out on dry specimens of mica-gneiss, amphibolite and serpentinite from KTB core samples and samples of surface oucrops in or&r to determine the effect that a deviatoric stress field, as observed at the KTB area, may have on the in-situ rock properties. Simulating the variation of the actual principal stresses and temperature with depth, seismic wave velocities, densities, linear and volumetric strain (porosity) have been measured. Comparison with data evaluated for lithostatic pressure conditions revealed that the stress-related effect on wave velocities is in the range of l-3%, due to microcracks which are selectively closed or kept open by the deviatoric stress. The effect of the deviatoric stress is particularly documented by shear wave splitting due to microfractures that are oriented normal to the minimum principal stress axis. (from Authors)
Measurement of in situ stress
955163 Integrated stress determination by joint inversion of hydraulic tests and focal mechanisms J. M. Yin & F. H. Comet, Geophysical Research Letters, 21(24), 1994, pp 2645-2648. An inversion method, based on a genetic algorithm, is proposed for interpreting jointly various kinds of stress data in order to overcome the limitation, in number and quality, of each data set. The method has been applied to results from hydraulic tests in boreholes and to focal mechanisms of induced seismicity observed within the same depth interval. This inversion confirms previous results suggesting that the regional stress field cannot be determined solely from an inversion of the fault plane solutions. (from Authors)
SITE INVESTIGATION AND FIELD OBSERVATION General 955164 Analysis and management of financial risks arising from ground conditions 1. L. Whyte, Transactions - Institution of Mining & Metallurgy. Section A, 104(Jan-April), 1995, pp A34-A40. The financial benefits of adequate site investigation can be demonstrated by risk modelling, and such an approach is described for a tunnelling scheme. Two models are outlined: the first analyses the effect of uncertainty in ground conditions on planning estimates of project cost and duration; and the second models the financial consequences of encountering unforeseen conditions during construction. Results are shown to be realistic when compared to the prototype event. A strategy is proposed for the management of ground risk that relates the level of investigation to the complexity and degree of risk in a project. (Author) 955165 Platinum exploration on the Great Dyke of Zimbabwe D9J3F;wen, Exploration & Mining Geology, 3(4), 1994, pp . The Great Dyke extends for 540 km along strike, to unknown depth, and varies in width from 3 km to 11 km. Rb/Sr age determinations gives values of approximately 2470 Ma. The Dyke consists of a variety of matic and ultramafic rocks, many altered to serpent&es. Vast mineral resources exist. These include chrome, asbestos, platinoids, nickel, copper and gold. Up to eleven chrome seams numbered from top to bottom occur in the lower ultramaflc sequences. Seams are narrow at 10 cm to 30 cm but of high grade. The platinum occurs 10 m to 40 m below the norite/pyroxenite contact. Extensive exploration programs have been carried out and the intention is to begin large-scale mining. (from Author)
Remote sensing and photographic techniques 955166 Mineral identification and mapping of hydrothermal alteration zones using high-spectral resolution images (AVIRIS) F. D. Van der Meer, ITC Journal, 1994-2, 1994, pp 145-154. High-spectral resolution images (AVIRIS) of the cuprite mining area were used to evaluate atmospheric calibration algorithms and test several mineral mapping techniques. Four scene normalization techniques were used: 1) the flat-field method. 2) the internal average reflectance method , 3) the empirical tine method, and 4) the atmospheric absorption removal method (ATREM). The algorithms were evaluated in terms of their spectral interpretability and their ability to remove both solar irradiance and atmospheric absorption features, noise and artifacts. (from Author) 955167 Calibration of airborne visible/infrared imaging spectrometer data (AVIRIS) to reflectance and mineral mapping in hydrothermal alteration zones: an example from the ‘Cuprite mining district’ F. Van der Meer, Geocarto International, 9(3), 1994, pp 2337.