No description available.

No description available.

Thesis(M.Eng.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 96-99.

[From introduction] Exploration geochemistry is an indirect method of detecting mineral deposits by measuring the abundance and distribution of ore elements and elements closely associated with ore in natural materials at or near the earth's surface. The method relies on the assumption that a mineral deposit is reflected by unusual element abundances or distribution patterns (geochemical halos), and that these indications of mineralization can be detected by geochemical surveys involving the collection and analysis of natural materials. The interpretation of geochemical surveys in mineral exploration involves: 1) The use of geological and statistical inference, based on a knowledge of the normal behaviour and distribution of indicator elements in the exploration area, to recognize apparent geochemical anomalies in field and analytical data and to predict the type of geochemical halo reflected by the anomalies. 11) The use of geological inference, based on a knowledge of the characteristics of geochemical halos and their relationship to mineral deposits, to predict the presence and probable location of an ore body. The interpretation process is, however, complicated by the absence of a simple universal formula that relates the abundance and distribution of elements in natural materials to the presence or absence of a mineral deposit. The interpretation of a geochemical survey must, thus, be based on an empirical approach which avaluates each survey as an individual problem. The objective of this dissertation is to illustrate the factors affecting the "nuts and bolts" approach to the interpretation of geochemical surveys in mineral exploration. The discussion is aimed at providing field geologists responsible -for the planning and execution of geochemical surveys with some basic guidelines for interpreting the surveys. I hope that the contents of this dissertation will help field geologists to "look in the last place first".

The Damara-Katanga orogen in central-southern Africa represents an area of 1.73xl0⁶ sq. km. The region is considered one of the wealthiest metallogenic provinces in the world. Successful exploration for stratabound base-metal deposits has taken place at this particular area since the introduction of more organised methodology in the early 1920s. The genesis, location and distribution of the ore deposits are related to their tectonic settings. Geodynamic evolution of the orogen, which initially formed part of a complex Pan-African rift system, comprises the following stages rifting; downwarping, including spreading on the western portion; syn-orogeny and late-orogeny. Two major tectonic events in the history of the region have been identified: the Katangan (900-750 Ma) and the Damaran episodes (750-500 Ma). Timing of mineralisation of ore deposits has been related to the evolutionary stages of the orogen. Genetic models of the most productive deposits are briefly discussed in this dissertation. The sedimentological, geochemical, paleogeographic and structural features can be employed as geological guidelines for integrated exploration programmes. Discoveries of major deposits and prospects in the orogen are also summarised, focussing on the exploration methods employed. The cost-effective use of the exploration techniques includes the classical copper-lead-zinc soil sampling for residual soils such as those in the Copperbelt area. Airborne magnetics and electromagnetics and follow-up ground geophysics have proved successful in areas where the cover is transported in the search for shallow ore deposits such as the Matchless massive sulphides. Remote sensing, geochemical and geophysical techniques have been tried in covered areas of western Botswana. The lack of geological control makes this interpretation difficult. A detailed geological mapping and the use of geochemical and geophysical techniques has been used to delineate carbonate-hosted base-metal deposits at the Otavi Land. The more expensive traditional methods necessary for the delineation of orebodies, such as pitting, trenching and drilling, are also discussed. Using a sequential approach, a possible exploration strategy is suggested, outlining the cost-effective use of remote sensing, geochemical and geophysical techniques. Standardisation in basic geological information is required for future successful explorations in the Damara-Katanga orogen, as well as attractive mining policies. In the event of their implementation, exploration perspectives are promising, specifically in terms of ore potential.

M.Sc. (Geology) / Please refer to full text to view abstract

Europe’s largest chrome deposit is hosted by the 2.44 Ga Kemi ultramafic layered intrusion. The lower half of the intrusion consists of peridotites, pyroxenites and chromitite layers while the upper half consists of websterites, gabbronorites and leucogabbros. The mafic minerals of the lower and upper parts of the intrusion are altered to serpentine, chlorite, talc, amphiboles and carbonates. However, the original mineralogy is still preserved in the middle part of the intrusion. Earlier work on the Kemi intrusion concentrated mainly on the economically important chromitite layers and suggested that these layers were formed through contamination of a single pulse of primitive magma by underlying Archaean basement crustal material. The broad variations of the major element concentrations reflect variations in the mode of the Kemi rocks. The petrology, which shows olivine- and orthopyroxene-dominated rocks in the lower portion of the intrusion to plagioclase- and clinopyroxene-dominated rocks in the upper portion, shows a gross consistency with a fractional crystallization process.The incompatible elements are relatively enriched in the lower portion of the intrusion which is not consistent with a broad fractional crystallization process. These variations suggest that the ultramafic portion of the KemiIntrusion is relatively enriched in trapped liquid compared to the mafic portion.ε2.44 Nd values ranges from +4 (consistent with depleted mantle source) to -10 (indicating a contribution from Archaean crust). The lower peridotites, pyroxenites and websterites have ε2.44 Nd values ranging between depleted mantle signatures and -2, whereas the gabbroic cumulates have ε2.44 Nd values which cover a range from around -5 to -10. Nd isotopic variation in the lower part of the profile is punctuated by distinct spikes to lower ε2.44 Nd corresponding to the chromitite horizons. Both the lower and upper portions of the Kemi Intrusion show enrichment of LREEC1 relative to HREEC1. The LREEC1 enriched values start to increase markedly from about the 1000 meter mark and continue to increase in value towards the roof of the intrusion.The main enrichment of PGE (ΣPPGE = 55 to 148 ppb) occurs approximately 90 to 160 m above the basal contact, beginning within andcontinuing above the main chromitite ore horizon. The mantle-normalized PGE abundances of the main chromitite horizon and the peridotites and pyroxenites below it show enrichment of IPGEPM (Os + Ir + Ru) relative to PPGEPM (Rh + Pd + Pt). In contrast, the overlying rocks are characterised by enrichment of PPGEPM relative to IPGEPM. These PGE-patterns suggest the influence of two distinct controlling processes above and below the main chromitite reef.The isotopic data are consistent with the initial introduction of multiple pulses of depleted mantle-derived magma crystallising olivine and pyroxene. Before the parent magma was fed into the Kemi magma chamber, it underwent crustal contamination and assimilation in a staging chamber within the lower crust. Some of these pulses were “critically crustally contaminated”, inducing chromite saturation and precipitation. The modelling also predicts minor in-situ contamination of the parent magma in the Kemi chamber with its wall and roof rocks. Above the main chromitite layer (about 160 m above the basal contact), the chromite content decreases and the PPGEPM/IPGEPM values increase which is consistent with scavenging of the IPGE into the lowermost layers and/or evolving magma compositions. Above 1000 m, the isotopic and REE data indicate a new magma pulse which has also been extensively contaminated in the staging magma chamber before emplacement into the Kemi magma chamber. The contamination in the staging magma chamber increased which is reflected in a progressively larger crustal component towards the top of the Kemi Intrusion

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science, Faculty of Science University of the Witwatersrand, Johannesburg 2018 / Canteen Kopje has yielded rare in-situ assemblages of the Fauresmith, a poorly defined industry often associated with the later Acheulean. The Fauresmith contains precocious developments in technology as early as ~0.5 Ma–features which only become widespread in the ensuing Middle Stone Age. The Fauresmith as a regional industry provides insight into technological practices during the period of significant behavioural diversification associated with archaic Homo sapiens. Previous excavations were conducted with relatively low spatial resolution. A new excavation, Pit 4 West, was conducted to investigate the spatial, stratigraphic and contextual association of the Fauresmith horizon in more detail. A multi-disciplinary fineresolution geoarchaeological approach was applied. A nuanced assessment of the Fauresmith’s context was developed, with macroscopic and microscopic analyses allowing for the identification of site formation processes influencing assemblages. The artefact sample size for the site was increased and the presence of diagnostic tools has aided in formally defining the Fauresmith at Canteen Kopje. / XL2019

No description available.

Abstract not available