Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes maps in pocket. Includes bibliographical references (leaves 389-409). Also available on the World Wide Web

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Includes bibliographical references. Available also in an electronic version.

Thesis (M.S.)--University of New Orleans, 2005. / Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Geology and Geophysics"--Thesis t.p. Vita. Includes bibliographical references.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2005. / Includes bibliographical references (p. 103-105).

Thesis (M. Sc.)(Geology)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

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 .

Candelaria, situated in central western Nevada, along the western margin of the Great Basin, is a large and predominantly low grade, epigenetic disseminated- and vein-type Ag deposit, of Early Cretaceous age. It represents the eroded, deeply oxidised and fault-disrupted root of extensive stratiform quartz-dolomite stockworked and sericite-dolomite-altered zones of medium temperature pyrite-dominated Ag(-Pb-Zn-Sb-As±Cu±Au) sulphide-sulphosalt mineralisation, which is hosted by receptive sedimentary and igneous rocks within structurally favourable zones in a district-scale tectonic pinchout, and which is genetically associated with Cordilleran granodiorite porphyry hypabyssal magmatism (diking), of high K calc-alkaline affinity. The mineralisation occurs along and directly beneath the Pickhandle allochthon, a serpentinite-sheathed volcanic-sedimentary tectonic méange which forms a local 'sole' plate to the regionally extensive Golconda allochthon, which was emplaced onto the edge of continental North America during the Early Triassic Sonoma orogeny. Mineralisation occurred where an irregularity in the Pickhandle thrust plane, caused by thickening of the méange, effected locally deeper truncation of the parautochthonous foreland sequence in its footwall - chiefly marine sediments of the Lower Triassic Candelaria Formation - against the deformed cherts of the Ordovician basement (Palmetto complex), to form a structural trap. Within this trap, mineralisation is hosted mainly by carbonaceous, carbonate- and phosphate-rich (and trace metal-rich) black shales at the base of the Candelaria Formation and by dolomite-quartz-altered serpentinites at the base of the Pickhandle allochthon. Stable isotope data (O, H, S) point to a predominantly magmatic source for the hydrothermal fluids and ore sulphur, a source most likely to be the parent pluton to the granodiorite porphyry dikes. More ore metals were also of igneous origin (mass balance calculations rule out Candelaria member 1 as the chief metal source).

No description available.

The Navachab Gold mine, an orogenic lode gold deposit, is located in the Karibib region of the Pan-African (ca. 550-500) Damara belt of central Namibia. Gold mineralisation is developed within the steeply NW dipping limb of the Karibib dome. Here, ore envelopes trend along three main orientations: a) trends shallowly towards the NE (the down plunge extent), b) trends sub-vertically in and along the down plunge extent and c) trends sub-horizontally across the down plunge extent. The down plunge extent represents the bulk of the gold mineralisation, hosting the only high grade ores mined at Navachab. As such, past work primarily focused on establishing the controls to the mineralisation observed here. The sub-vertical and sub–horizontal ore trends are seen as secondary, lower grade, being hosted in the footwall. By cutting pushbacks into the footwall, in an effort to regain access to high grade pit bottom, future gold production almost exclusively relies upon optimally mining these ores. This underlines the importance to investigate and outline the mineralising controls to the secondary ore trends. This study identified the following prevailing quartz vein sets developed within the footwall, set (1) dips shallowly towards the NE (conjugate vein set), (2) steeply towards the NW (bedding parallel veins) and (3) steeply towards the SE (S2 foliation parallel). The NW and SE dipping sets contain high average gold grades, occurring at an infrequent vein density. The NE dipping veins, as a result of occurrence density alone, was highlighted as the dominant gold hosting set. Veining occurred during the late stages of the NW-SE directed, sub-horizontal shortening (D2) event and is associated with top-to-the-NW thrusting and NW-verging folds. Re-Os molybdenite dating from auriferous quartz veins indicates mineralisation occurred at 525-520 Ma. As crustal shortening amplified the Karibib dome, flexural flow developed fractures along bedding planes, providing the control to bedding parallel veins (NW dipping). With continued crustal compression the dome later experienced fold lock up associated with reduced mean rock stress and sub-horizontal extension occurred along the steeply NW dipping limb. Horizontal extensional gashes sucked in fluids to form the shallowly NE dipping conjugate vein set. These features suggest the regional D2 strain as the first-order control to quartz vein development, down plunge and within the footwall ores. To further define the secondary ores, lithological and structural controls were evaluated on a more detailed local scale. With equal amounts of biotite schist and calc-silicate host rock (bulk of the footwall lithology) material analysed, the biotite schist units were found to contain a larger volume amount of quartz veins. The mineralisation incurred is also developed at higher average gold grades compared to that of the calc-silicates, demonstrating biotite schist having the optimal rheology for quartz vein emplacement. Normal faulting and thrusting occurs widespread, at all scale levels, across the footwall. These were primarily observed along bedding foliations and secondly at higher angles cutting across foliation. The study did not constrain the extent of these, but can conclude faulting plays a very prominent role in re-distributing the secondary ores parallel to bedding along sub-vertical trend planes. Great care should be placed in properly modelling these with 3D software such as Leapfrog. The Navachab gold mineralisation came about as a result of convergent and collisional tectonics activating metamorphic dehydration of the crustal metapelites. As these fluids ascended they absorbed gold from the crust, emplaced by either a magmatic or paleo-placer source. The gold enriched hydrothermal fluids amalgamated in large scale 1ste order structures (shearing of the steep NW limb of the Karibib Dome, the Mon Repos Thrust Zone) that acted as primary active fluid path ways. In the case of Navachab the gold enriched fluid fluxed along these pathways while interacting with fluid sinks related to a physical throttle (brittle schist, folding, bedding parallel shears) and/or a chemical trap (marbles). By summarising and detailing the fluid sinks and active fluid pathways identified by this and previous works, it is strongly recommended that a mineral approach system be designed and implemented as targeting model to lead future exploration endeavours.