Geodynamics, rifting, stratiform and stratabound mineral deposits
- Authors: Dingemans, D.R.W.
- Date: 1981 , 2013-03-19
- Subjects: Ore deposits , Geodynamics , Mines and mineral resources , Rifts (Geology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5012 , http://hdl.handle.net/10962/d1006107 , Ore deposits , Geodynamics , Mines and mineral resources , Rifts (Geology)
- Description: Stratiform and stratabound ore deposits commonly show a direct relationship with rifts. This association is studied by developing a geodynamic model of mantle processes and crustal responses. The geodynamics of the earth can be modelled by the process of mantle advection, which involves the episodic generation and segregation of low density mantle diapirs and their rise and subsequent interaction with the crust. The theory of mantle advection explains the genetic association between rifting, magmatism, basin development and subsequent orogeny and metamorphism. Global evolution has passed through a number of major stages of non-uniformitarian development in which each cycle was characterized by fairly uniform behaviour terminated by intense geodynamic upheaval. The relationship between geological evolution and mantle advection is examined by reviewing the major characteristics of each of the cycles, which correspond to the Archean, Early Proterozoic, Mid Proterozoic, Late Proterozoic-Palaeo2oic, and Mesozoic - Cainozoic eras. Although mentle advection has controlled crustal processes throughout time, the decrease in the thermal energy of the earth has caused >the major evolutionary changes in response to thickening and a greater rigidity of the sialic crust. Rifts are penetrative taphrogenic faults in the earths crust which act as major conduits for the transfer of magmas, from the mantle and lower crustal levels, to the upper crust and the surface. Rifts are also permeable zones for the migration of metalliferous brines, generated by magmatic differentiation. These metalliferous brines would either be exhaled at surface to form stratiform volcanogenic and volcanosedimentary ore deposits , or would interact with preferential host horizons to form stratabound ore deposits . The associat ion between rifting and stratiform and stratabound ore deposits is illustrated by examining :he tectonic setting, and st ratigraphic relationships of typical ore deposit types .
- Full Text:
- Date Issued: 1981
- Authors: Dingemans, D.R.W.
- Date: 1981 , 2013-03-19
- Subjects: Ore deposits , Geodynamics , Mines and mineral resources , Rifts (Geology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5012 , http://hdl.handle.net/10962/d1006107 , Ore deposits , Geodynamics , Mines and mineral resources , Rifts (Geology)
- Description: Stratiform and stratabound ore deposits commonly show a direct relationship with rifts. This association is studied by developing a geodynamic model of mantle processes and crustal responses. The geodynamics of the earth can be modelled by the process of mantle advection, which involves the episodic generation and segregation of low density mantle diapirs and their rise and subsequent interaction with the crust. The theory of mantle advection explains the genetic association between rifting, magmatism, basin development and subsequent orogeny and metamorphism. Global evolution has passed through a number of major stages of non-uniformitarian development in which each cycle was characterized by fairly uniform behaviour terminated by intense geodynamic upheaval. The relationship between geological evolution and mantle advection is examined by reviewing the major characteristics of each of the cycles, which correspond to the Archean, Early Proterozoic, Mid Proterozoic, Late Proterozoic-Palaeo2oic, and Mesozoic - Cainozoic eras. Although mentle advection has controlled crustal processes throughout time, the decrease in the thermal energy of the earth has caused >the major evolutionary changes in response to thickening and a greater rigidity of the sialic crust. Rifts are penetrative taphrogenic faults in the earths crust which act as major conduits for the transfer of magmas, from the mantle and lower crustal levels, to the upper crust and the surface. Rifts are also permeable zones for the migration of metalliferous brines, generated by magmatic differentiation. These metalliferous brines would either be exhaled at surface to form stratiform volcanogenic and volcanosedimentary ore deposits , or would interact with preferential host horizons to form stratabound ore deposits . The associat ion between rifting and stratiform and stratabound ore deposits is illustrated by examining :he tectonic setting, and st ratigraphic relationships of typical ore deposit types .
- Full Text:
- Date Issued: 1981
Sampling in the evaluation of ore deposits
- Authors: Grant, D E C S
- Date: 1981 , 2013-03-19
- Subjects: Ore deposits , Mine valuation , Ores -- Sampling and estimation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5008 , http://hdl.handle.net/10962/d1005912 , Ore deposits , Mine valuation , Ores -- Sampling and estimation
- Description: Sampling is an error generating process and these errors should be reduced to a minimum if an accurate ore reserve estimation is to be made from the sample values. Error in sampling can arise from the sampling procedure as well as where and how each sample is taken from the deposit . Sampling procedure involves sample collection, sample reduction and analysis, and the error from each of these three stages has an equal influence on the total error of the process. Error due to sampling procedure should be identified and eliminated at an early stage in the evaluation programme. An ore deposit should be subdivided into sampling strata along geological boundaries, and once these boundaries have been established they should be adhered to for the evaluation programme. The sampling of each stratum depends on the small-scale structures in which the grade is distributed, and this distribution in relation to sample size controls sample variance, sample bias and the volume of influence of each sample. Cluster sampling can be used where an impractically large sample is necessary to reduce sample variance or increase the volume of influence of samples. Sample bias can be reduced by composing a large number of small samples . Sampling patterns should be designed with reference to the volumes of influence of samples, and in favourable geology, geostatistical or statistical techniques can be used to predict the precision of an ore reserve estimation 1n terms of the number of samples taken. Different are deposits have different sampling characteristics and problems which can be directly related to the geology of the mineralization. If geology is disregarded when sampling an are deposit, an evaluation programme cannot claim to give an accurate estimate of the ore reserves .
- Full Text:
- Date Issued: 1981
- Authors: Grant, D E C S
- Date: 1981 , 2013-03-19
- Subjects: Ore deposits , Mine valuation , Ores -- Sampling and estimation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5008 , http://hdl.handle.net/10962/d1005912 , Ore deposits , Mine valuation , Ores -- Sampling and estimation
- Description: Sampling is an error generating process and these errors should be reduced to a minimum if an accurate ore reserve estimation is to be made from the sample values. Error in sampling can arise from the sampling procedure as well as where and how each sample is taken from the deposit . Sampling procedure involves sample collection, sample reduction and analysis, and the error from each of these three stages has an equal influence on the total error of the process. Error due to sampling procedure should be identified and eliminated at an early stage in the evaluation programme. An ore deposit should be subdivided into sampling strata along geological boundaries, and once these boundaries have been established they should be adhered to for the evaluation programme. The sampling of each stratum depends on the small-scale structures in which the grade is distributed, and this distribution in relation to sample size controls sample variance, sample bias and the volume of influence of each sample. Cluster sampling can be used where an impractically large sample is necessary to reduce sample variance or increase the volume of influence of samples. Sample bias can be reduced by composing a large number of small samples . Sampling patterns should be designed with reference to the volumes of influence of samples, and in favourable geology, geostatistical or statistical techniques can be used to predict the precision of an ore reserve estimation 1n terms of the number of samples taken. Different are deposits have different sampling characteristics and problems which can be directly related to the geology of the mineralization. If geology is disregarded when sampling an are deposit, an evaluation programme cannot claim to give an accurate estimate of the ore reserves .
- Full Text:
- Date Issued: 1981
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