Thesis (M.S.)--University of Arizona, 2001. / Added thesis t.p. Title from HTML title screen (viewed Apr. 25, 2002). Includes bibliographical references.

Thesis (Ph. D.)--University of Adelaide, Dept. of Geology and Geophysics, 1985. / 6 folded (5 of them maps) in pocket. Includes bibliographical references.

Thesis (Ph. D.)--University of Adelaide, Dept. of Geology and Geophysics, 1987. / Offprint in pocket. Includes bibliographical references (leaves 82-90).

Thesis (Ph. D.)--University of Adelaide, Dept. of Economic Geology, 1984. / Microfiche and maps (numbered 1-7) in pocket. Includes bibliographical references (6 unnumbered leaves ).

Airborne electromagnetic methods were developed in the early 1950's, mostly by Canadian mining exploration companies as a means of economically and successfully searching large areas for conductive massive sulfide mineralisations. As new technologies developed they have become more and more sophisticated. They can detect conductors at depths in excess of 200 m and are routinely used for overburden mapping. The data is digitally recorded and processed. One of the most successful methods is the time domain airborne INPUT$ sp1$ system, for numerous mineral deposits were found by this system in the Canadian Shield. / Present interpretation techniques are based on the use of nomograms (i.e. families of pre-computed characteristic responses) and the method is easily amenable to digital processing as it is easy to program and economic to use. For high accuracy interpretation however it is necessary to develop quantitative interpretation techniques that can make full use of all the data available. Inverse theory has been used with great success in all branches of geophysics, but to date in mining exploration it has been used for the interpretation of airborne E.M. data using only the one layer earth model. Use of inverse theory for the plate model has been limited by the high cost of numerically solving the forward problem. / In this thesis we show how to use inverse theory to interpret time domain E.M. data with the rectangular thin plate model by introducing some economies. It is then possible to estimate parameter errors, the correlation matrix and to assess the validity of the model. This is extended to the joint inversion of magnetic and aeromagnetic data a case that often arises in mining problems. It is finally shown that under some assumptions the late time channels can be used to interpret time domain E.M. data in the presence of conductive overburden. ftn$ sp1$Registered trademark of Barringer Research Ltd.

No description available.

The eastern branch of the late Proterozoic Damara Orogenic Belt of central Namibia hosts various copper, gold, manganese and uranium deposits, but in the vicinity of Steinhausen, approximately 145 km northeast of Windhoek, the Damara Belt becomes increasingly covered by recent Kalahari cover sediments resulting in little known geology and subsequent lack of discovered economic mineral deposits. Airborne magnetic and radiometric data over the Steinhausen Study Area was enhanced through image processing and filtering to accentuate characteristics of subsurface geology that, by comparing these characteristics to known geology, aided in the interpretive mapping of lithology, structure and targets for follow-up exploration. As a result, some important observations regarding the regional lithology can be drawn. An arenaceous stratigraphic unit that includes a coarse grained, glassy quartzite below the Kuiseb Formation equates to either the eastern Damaran equivalent of the Nosib Group subjected to high grade metamorphism or, alternatively, the upper part of the pre-Damaran sequence, immediately underlying the Damara. The Kuiseb Formation within the study area is uncharacteristically varied as compared to the same formation further west along the Damaran Orogen and can be subdivided into 5 separate units based on geophysical signature. Structural features evident within the study area include the prominent Kudu and Okahandja Lineaments and straddle an area of inferred uplifted stratigraphy of possibly pre-Damara age. The Ekuja Dome (Kibaran age and host to the Omitiomire copper deposit) is also clearly discernible on the airborne magnetic data and is cross-cut by an east-northeast structural zone. Direct targets for follow-up exploration include the Rodenbeck intrusion, anomalous magnetic bodies and numerous radiometric anomalies present within the study area. Identified dome-like features are considered prospective for Omitiomire-style deposits and the Okatjuru Layered Complex is considered a possible source of copper, chromite, magnetite, ilmenite, nickel and the platinum group elements.

Offprint in pocket / Bibliography: leaves 82-90 / xii, 95 leaves, [6] leaves of plates : ill. (some col.) ; 30 cm. + [11] plastic envelopes containing 22 folded ill., all in case, 35 mm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1987

Thesis (M.S. - Geosciences)--University of Arizona. / Includes bibliographical references.

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. Johannesburg, 2015 / Three new methods for determining the structural index and source distance for magnetic field data are presented. These methods require only the calculation of the first and second order analytic signal amplitudes of the total field and are applicable to both profile and gridded data. The three methods are first tested on synthetic data and then on two real datasets to test for applicability and repeatability. It was found that each method had different strengths and weaknesses and thus one method cannot be favoured over the others. Cooper (2014) describes how to calculate the distance to source over both profile and gridded data given a user defined structural index. Often however, particularly in the case of real data, the structural index is not known or varies over the surveyed area. These three new methods however do not require any user input since the structural index is calculated thus making them more applicable to regions of unknown geology. It was found that the first of the three new methods, the multi-distance inversion method, was best used as an edge-detection filter, since the use of higher order derivatives resulted in increased noise levels in the distance to source calculation. The third of these new methods, the unconstrained inversion method, discussed in Chapter 7, not only solves for the structural index but also determines the depth of the source. In that particular case, the structural index is used as a rejection filter, whereby, depth solutions associated with structural index values outside of the expected range are deemed to be invalid. Unlike the third new method, the first two methods require the distance to source to be calculated via the approach described by Cooper (2014) (which requires the user to define the structural index), the results of which are later rescaled by the calculated structural index to yield what is termed a rescaled distance to source. All three of the new methods are fully automatic and require no user control. The techniques were first tested on both profile and gridded theoretical data over sources with known structural index values. All of the methods were able to estimate the structural index of each of the particular sources and give depth estimates that varied from the true depth by less than 20 percent (with deeper sources being more inaccurate). Noise was also added to the theoretical data in an attempt to assess how the methods can be expected to perform with real data. It was found that when applied to noisy data, these methods performed equally well to slightly worse, than when the method developed by Cooper (2014) was used. As a real world case study these three new methods were tested on aeromagnetic data collected over the Kuruman Military Area, Northern Cape, South Africa. Regional deformations as well as later intrusive dykes and cross cutting faults were imaged by the chosen depth determination procedures. The dolerite dykes in the area were found to occur between 20 to 60 m deep. While the sand cover was estimated to be between 30 to 40 m thick. Overall, the techniques yield distance to source estimates that differ by less than 15 m, over sources, to the results obtained by using the source distance method (Cooper, 2014). To test for repeatability a second aeromagnetic dataset, collected over a dyke swarm within the Bushveld Complex, South Africa was considered. Again comparable (less than 15 m over sources) depth estimates were made between the unconstrained and constrained inversions. Since the distance to source estimates produced by these new unconstrained inversion methods are comparable to those produced by constrained inversion (Cooper, 2014) the project can be deemed successful.