Rock physical properties are usually associated with important geologic features within mineral deposits and can be used to define the location, depth and size of the deposit, type of ore, or physical property contrast between the host and country rock. Geophysical surveys are sensitive to physical properties and therefore are widely used in mining exploration, especially in concealed terrains. The surveys can be performed at multiple scales, resulting in corresponding physical property datasets at different scales. Survey scale can vary from core or hand sample, involving few cubic centimeters, to regional-scale surveys providing information about physical property contrasts between distinct regional geological features. The understanding of the relationship between the physical property distributions with the sample volume (e.g. district, deposit, and drill-hole scale) is required where point scale physical property measurements are going to be consistent with measurements at larger volumetric scales during the integration of data for geophysical modeling The approach used to address the problem of understanding the scaling relations of physical properties, was achieved by considering them as second order stationary regionalized variables and then applying the random function formalism, provided by geostatistics theory. Geostatistics provide the required framework to characterize, quantify, model and link the spatial variability of the random variable at the different volumetric scales. The aim of this study is to apply geostatistics to effectively integrate data collected at several scales and bring knowledge to the understanding of the scaling relations of magnetic susceptibility. For this purpose, measurements of magnetic susceptibility available from Flin Flon copper-zinc district in Canada will be used. The data available at point scale were collected with hand portable magnetic susceptibility meter. The larger volumetric scale dataset were acquired using frequency domain electromagnetic instruments capable of measuring larger sample volumes, and then used to obtain magnetic susceptibility models using geophysical inversion algorithms. Once different scale models of magnetic susceptibility were available, quantification of the scaling relation using geostatistics, specifically variogram models and dispersion variance were determined. The understanding provided by the scaling analysis of the Flin-Flon magnetic data is applied to data from the Rio Blanco copper district in central Chile. Magnetic susceptibility measurements collected with a hand magnetic susceptibility meter on drill-core is integrated in larger scale volumes used for geophysical inversion modeling of regional scale airborne magnetic field measurements to recover magnetic susceptibility models. The methodology resulting from this application of geostatistics is used to address the problem of integrating multiple scales of physical property data in an effective way. The resulting physical property models capture the small-scale magnetic susceptibility variability observed and can guide larger-scale variability within geophysical inversion models. Establishing reliable statistical correlations between physical properties and rock units controlling ore within deposits are crucial steps leading predictive mine exploration tools. Any numerical modeling approach to establish these correlations should consider in some way the scaling nature of both physical property and ore content.

No description available.

<p> Brittleness is a key characteristic for effective reservoir stimulation and is mainly controlled by mineralogy in unconventional reservoirs. Unfortunately, there is no universally accepted means of predicting brittleness from measures made in wells or from surface seismic data. Brittleness indices (BI) are based on mineralogy, while brittleness average estimations are based on Young's modulus and Poisson's ratio. I evaluate two of the more popular brittleness estimation techniques and apply them to a Barnett Shale seismic survey in order to estimate its geomechanical properties. Using specialized logging tools such as elemental capture tool, density, and P- and S wave sonic logs calibrated to previous core descriptions and laboratory measurements, I create a survey-specific BI template in Young's modulus versus Poisson's ratio or alternatively &lambda;&rho; versus &mu;&rho; space. I use this template to predict BI from elastic parameters computed from surface seismic data, providing a continuous estimate of BI estimate in the Barnett Shale survey. Extracting &lambda;&rho;-&mu;&rho; values from microseismic event locations, I compute brittleness index from the template and find that most microsemic events occur in the more brittle part of the reservoir. My template is validated through a suite of microseismic experiments that shows most events occurring in brittle zones, fewer events in the ductile shale, and fewer events still in the limestone fracture barriers. </p><p> Estimated ultimate recovery (EUR) is an estimate of the expected total production of oil and/or gas for the economic life of a well and is widely used in the evaluation of resource play reserves. In the literature it is possible to find several approaches for forecasting purposes and economic analyses. However, the extension to newer infill wells is somewhat challenging because production forecasts in unconventional reservoirs are a function of both completion effectiveness and reservoir quality. For shale gas reservoirs, completion effectiveness is a function not only of the length of the horizontal wells, but also of the number and size of the hydraulic fracture treatments in a multistage completion. These considerations also include the volume of proppant placed, proppant concentration, total perforation length, and number of clusters, while reservoir quality is dependent on properties such as the spatial variations in permeability, porosity, stress, and mechanical properties. I evaluate parametric methods such as multi-linear regression, and compare it to a non-parameteric ACE to better correlate production to engineering attributes for two datasets in the Haynesville Shale play and the Barnett Shale. I find that the parametric methods are useful for an exploratory analysis of the relationship among several variables and are useful to guide the selection of a more sophisticated parametric functional form, when the underlying functional relationship is unknown. Non-parametric regression, on the other hand, is entirely data-driven and does not rely on a pre-specified functional forms. The transformations generated by the ACE algorithm facilitate the identification of appropriate, and possibly meaningful, functional forms.</p>

The Durham/Cambridge/Birmingham Universities two-ship marine geophysical cruise to the Hatton Bank continental margin took place in May/June 1985, during which single- and two-ship seismic reflection/refraction data, together with under way gravity and magnetic anomaly, and bathymetric data were collected within a 200 km by 150 km area straddling the continent-ocean transition. The processing, modelling and interpretation of four two-ship synthetic aperture profiles (SAP) and the gravity and magnetic anomaly data is presented. Gravity models show that a density model based on the crustal velocity structure defined by synthetic seismogram modelling of the two-ship expanding spread profiles is insufficient to reproduce the observed gravity profile across the margin. This requires additional contributions in the form of density gradients in the underlying sub-crustal part of the lithosphere and asthenosphere, and this is investigated by thermal modelling. Analysis of the magnetic anomaly data shows that oceanic magnetic anomalies 21 and 22 are developed in the north-west of the 1985 survey area. Anomalies 23 and 24 cannot be recognised due to post-rift igneous activity and/or subaerial seafloor spreading. The positions of anomalies 23 and 24B are reconstructed within the survey area, and the theoretical anomaly 24B position is used to determine the position of the continent-ocean boundary. Analysis of the anomalies recorded on the upper continental slope shows that the acoustic basement in this area is volcanic. Interpretation of the SAP profiles shows that the margin can be described in terms of three distinct volcanic sequences. The continental sequence is composed of lavas extruded onto continental crust during a period of continental volcanism which occurred before the onset of seafloor spreading just prior to anomaly 24B.The sequence thickens to the north-west, to form a set of seaward-dipping reflectors. The oceanic sequence comprises oceanic crust within which structurally different seaward-dipping dipping reflectors are developed. This sequence is associated with the reconstructed positions of anomalies 23 and 24B, and is interpreted as having formed during a period of subaerial seafloor spreading. The late sequence separates, and in part overlies the continental and oceanic sequences. Magnetic anomalies associated with the late sequence are arcuate, and have high amplitudes, implying an origin other than simple seafloor spreading. The late sequence is interpreted as originating from post-rift igneous activity in the Eocene.

Rock physical properties are usually associated with important geologic features within mineral deposits and can be used to define the location, depth and size of the deposit, type of ore, or physical property contrast between the host and country rock. Geophysical surveys are sensitive to physical properties and therefore are widely used in mining exploration, especially in concealed terrains. The surveys can be performed at multiple scales, resulting in corresponding physical property datasets at different scales. Survey scale can vary from core or hand sample, involving few cubic centimeters, to regional-scale surveys providing information about physical property contrasts between distinct regional geological features. The understanding of the relationship between the physical property distributions with the sample volume (e.g. district, deposit, and drill-hole scale) is required where point scale physical property measurements are going to be consistent with measurements at larger volumetric scales during the integration of data for geophysical modeling The approach used to address the problem of understanding the scaling relations of physical properties, was achieved by considering them as second order stationary regionalized variables and then applying the random function formalism, provided by geostatistics theory. Geostatistics provide the required framework to characterize, quantify, model and link the spatial variability of the random variable at the different volumetric scales. The aim of this study is to apply geostatistics to effectively integrate data collected at several scales and bring knowledge to the understanding of the scaling relations of magnetic susceptibility. For this purpose, measurements of magnetic susceptibility available from Flin Flon copper-zinc district in Canada will be used. The data available at point scale were collected with hand portable magnetic susceptibility meter. The larger volumetric scale dataset were acquired using frequency domain electromagnetic instruments capable of measuring larger sample volumes, and then used to obtain magnetic susceptibility models using geophysical inversion algorithms. Once different scale models of magnetic susceptibility were available, quantification of the scaling relation using geostatistics, specifically variogram models and dispersion variance were determined. The understanding provided by the scaling analysis of the Flin-Flon magnetic data is applied to data from the Rio Blanco copper district in central Chile. Magnetic susceptibility measurements collected with a hand magnetic susceptibility meter on drill-core is integrated in larger scale volumes used for geophysical inversion modeling of regional scale airborne magnetic field measurements to recover magnetic susceptibility models. The methodology resulting from this application of geostatistics is used to address the problem of integrating multiple scales of physical property data in an effective way. The resulting physical property models capture the small-scale magnetic susceptibility variability observed and can guide larger-scale variability within geophysical inversion models. Establishing reliable statistical correlations between physical properties and rock units controlling ore within deposits are crucial steps leading predictive mine exploration tools. Any numerical modeling approach to establish these correlations should consider in some way the scaling nature of both physical property and ore content.

Weathering geochronology permits delimiting the ages of weathering profiles, determining rates of weathering and landscape evolution and inferring palaeoclimatic and environmental conditions that control the surficial evolution of continents. It also provides insights into the timing and rates of supergene enrichment of metal and precious mineral deposits. Until recently, weathering geochronology was primarily based on K-Ar and 40Ar/39Ar dating of supergene minerals. Recent advances by U-Th series dating of pedogenic carbonate (Sharp et aI., 2003), in situ U-Th series dating of iron hydroxides (Bernal et aI., 2006), U-Pb SHRIMP dating of opals (Nemchin et aI., 2006), and (U-Th)/He and 4HePHe analysis of supergene goethite (Shuster et aI., 2005) expand the number of minerals and the time range where weathering geochronology can be applied. Weathering profiles blanket more than one third of the Australian continent and are purportedly among the oldest weathering profiles on earth. Unravelling the history of weathering and landscape evolution in these areas requires techniques capable of dating supergene minerals at all time scales, but particularly at the > I Ma scale. Currently, the K-Ar, U-Pb, and U-Th/He methods are the only techniques suitable to directly date supergene minerals on such time-scales. In this study, I show how the combination of 4°ArP9Ar and (U-Th)/He geochronology can be used to unravel the weathering and landscape evolution history of continents. The application of radiogenic isotope-dating techniques and the proper interpretation of geochronological results require understanding of the dated mineralogy and the presence of potentially contaminating phases. The successful application of 40ArP9Ar weathering geochronology was made possible through detailed understanding of the hollandite-group Mn oxide and alunite-group sulfate crystal chemistry and mineral physics. Similarly, in this study, I have refined the application of (U-Th)/He dating of goethite. The successful application of this technique relies on the identification and selection of suitable goethitebearing samples in the field; the characterization of mineral paragenesis by optical microscopy; the determination of fine-scale mineral chemistry and paragenesis through electron microscopy and microprobe analysis; the determination of physico-chemical properties (mineral structure, crystallinity) of the various types of supergene goethite through x-ray (bench-top and synchrotron) diffraction techniques; and application to noble gas diffusion experiments in ultra-high vacuum techniques to quantify the crystallochemical controls on the helium (natural radiogenic 4He and artificial spallogenic 3He) diffusion properties and retentivity of goethite. Finally, to test the reliability of the (U-Th)/He dating method, I apply the methodology to weathering profiles in a range of geological environments where stratigraphic and paragenetic relationships provide tight constraints on the possible history of mineral precipitation. For the applied component of this study, I (with a group of collaborators) chose the Hamersley Province as the key study site for the application of combined 40ArP9Ar and (UTh)/ He geochronology, for several reasons: the Hamersley Province is one of the longest lived landscapes on Earth and is extensively blanketed by thick weathering profiles that contain a plethora of crystalline goethite suitable for (U-Th)/He dating; the goethite in these weathering profiles coexists with K-bearing Mn oxides suitable for 4°Ar/39Ar dating; and mining operations provide exposure and access to near complete weathering profiles, enabling the sampling of goethite and Mn oxides for geochronology. Deep (50 to 100 metres on average and up to 400 metres) lateritic weathering profiles in the Hamersley Province outcrop over 80, 000 km2 on ridges and plateaus, ranging in height from II 00 m to 400 m. These lateritic weathering profiles are developed on Archaean banded-iron formation and host some of the world's largest iron ore deposits. Some authors have proposed that the lateritic weathering profiles represent the remnants of a continuous Mesozoic land surface now partially eroded. Surrounding the plateaus and ridges, ferruginized detrital sediments on valley slopes and floors and ferruginized detritus in paleochannel deposits (channel iron deposits or CID), also hosting high-grade iron ore, reveal evidence of widespread erosion and re-deposition of former weathering profiles. They also display evidence of post-depositional weathering and ferruginization, suggesting a complex interplay between weathering and erosion during landscape evolution in the region. 4°ArP9Ar dating of 204 grains of supergene Mn oxides (mostly cryptomelane and hollandite) extracted from 70 samples from seven distinct weathering profiles at 7 field sites, up to 300 kilometres apart, yield precipitation ages ranging from 63.4 ± 0.9 to 1.5 ± 0.2 Ma. When combined with previous unpublished 40ArP9Ar results, ranging from 81.1 ± 0.4 to 11.6 ± 0.3 Ma, the geochronology indicates a prolonged (Late Cretaceous to Recent) and episodic weathering record for the Hamersley Province, where periods of intense dissolution-reprecipitation of Mn oxides (51-41, 24-16 Ma) alternate with periods of relatively subdued mineral precipitation. The intense periods of mineral dissolution-precipitation correlate with maj or global climatic events. The goethite precipitation record confirms the longevity of weathering processes identified in the Mn oxide record. (U-Th)/He dating of 85 grains of goethite from 39 samples (20 hand specimens) from six sampling sites (5 sites sampled for 4°Ar/39Ar geochronology) yield reliable precipitation ages, ranging from 84.3 ± 12.2 to 3.0 ± 0.2 Ma. The deep (~100 m) lateritic weathering profile overlying banded iron-formation in the Hamersley Province record weathering process already ongoing in Late Cretaceous and spanning the Paleogene and Neogene. The geochronological results also reveal that the lateritic profiles in the Metawandy Valley (50-2 Ma), Mt Wall (60-30 Ma), Mt Tom Price (81-12 Ma) and Marandoo (52-12 Ma) regions had already reached great depths (70-100 m on average and up to 220 m below present land surfaces) by at least the Late Cretaceous or Early Paleogene. The results also show that weathering has been less effective at promoting the advancement of the weathering front during the Late Paleogene and Neogene. The geochronological results for authigenic supergene Mn-oxides and goethite III ferruginized detrital deposits (canga) in the Rhodes Ridge (41 to 7 Ma) area indicate that former land surfaces blanketing the Hamersley Province plateaus and ridges had been partially or nearly completely eroded by at least the Eocene. Geochronological results for the channel iron deposits reveal a similar scenario. 40ArP9Ar dating of Mn oxides (ranging from 32 to 17 Ma at the Lynn Peak Cm) and (U-Th)/He dating of goethite (ranging from 18 to 5 Ma at the Yandicoogina cm, and from 43 to 28 Ma at the Lynn Peak Cm) in late-stage authigenic cements indicate that the channel iron deposits had completely aggraded with ironrich sediments and were undergoing goethite cementation (ferruginization) by, at least, the Late Middle Eocene. Age versus depth distributions in channel iron deposits indicate that ferruginization of the channel sediments becomes progressively younger with depth in the profile, strongly suggesting that ferruginization occurred at the groundwater-atmosphere interface and the process moved downwards through progressive deepening of the water table. I interpret that this process was driven by the overall transition towards aridity of northwestern Australia in the Neogene. Excursion towards more humid climates in the Early-Middle Miocene has promoted the partial dissolution and secondary precipitation of channel cements in the upper parts of the profiles or near surface environments. Correlation between the weathering record and independent climatic and environmental indicators suggests that the formation of lateritic weathering profiles on banded iron-formation can be linked to warm and humid climatic conditions in the Late Cretaceous and Early Paleogene, when Australia lay with Gondwana at low latitudes. Climate change at the end of Paleogene, a consequence of the break-up of Gondwana and Australia's accelerated drift away from Antarctica, is identified at this stage as the causal event that promoted the erosion and deposition of former weathering profiles and the formation of extensive detrital and paleochannel deposits. Amid the Neogene aridification of northwestern Australia, a brief excursion towards more humid climatic conditions at the Early Miocene has promoted extensive re-crystallization of supergene minerals in weathering profiles throughout the region. The Neogene aridification of northwestern Australia may also explain the decelerating rates of weathering and weathering front propagation in lateritic profiles of this regIOn. A comparison of the weathering record obtained for the Hamersley Province with the results of similar studies from the Carajas and Quadrilatero Ferrifero Regions, Brazil, and Burkina Faso and Gabon, West Africa, reveals that intense weathering and enrichment ofMn oxides within the weathering profiles occurred at the 50-40 Ma interval, but particularly at 47-45 Ma. The remarkably similar weathering history obtained for the three southern Hemisphere continents suggests that weathering in these ancient landscapes may be controlled by global (greenhouse) climatic conditions.

Thesis (Ph.D.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 83-94)

Thesis (Geophysical Engineer)--California Institute of Technology, 1950. / Title from home page (viewed 04/27/2010). Includes bibliographical references.

Nautanen Deformation Zone, is a prominent deformation zone in the Malmfälten area, which is of importance to understand for mineral exploration purposes. In spite of diverse geophysical data being available in Malmfälten and the good correlation between airborne measurements and geological observations, the area has not been fully investigated in detail using the aforementioned available data. A geological feature in connection with the Mertainen magnetite-breccia apatite iron ore deposit has been studied. Methods include the study of geological maps, the study of analytic signals of magnetic and gravity data, data processing, potential field- and 3D modelling and the interpretation of aforementioned models. Based on the observed and modelled data a fold structure has been detected in connection with Mertainen, and several mineralizations are believed to be structurally related to this fold. Furthermore, a potential mineralization structurally related with the fold has been detected, though it is quite likely that it isn't economically viable. / Nautanen Deformation Zone, är en framträdande deformationszon i Malmfälten området, vilken är av betydelse att förstå för mineral prospekterings ändåmål. Trotts att det finns ett stort utbud av geofysiska data i Malmfälten och att det finns en god korrelation mellan de flyggeofysiska mätningarna och geologiska observationer, så har området inte undersökts fullständigt med den tillgängliga datan. En geologisk struktur i koppling till apatit järn malms fyndigheten Mertainen has studerats. Bland metoder ingår studie av geologiska kartor, studie av de analytiska signlar hos magnetiska och gravimetriska data, data processering, potential fält- och 3D modellering samt tolkningen av ovannämnda modeller. Baserat på den observerade samt modellerade datan har en veck strucktur upptäckts i koppling till Mertainen, och flertalet mineraliseringar tros vara strukturellt relaterade till detta veck. Dessutom har en potentiell mineralisering strukturellt relaterad till vecket upptäckts, dock är det väldigt troligt att den inte är ekonomiskt brytbar.

Rock physical properties are usually associated with important geologic features within mineral deposits and can be used to define the location, depth and size of the deposit, type of ore, or physical property contrast between the host and country rock. Geophysical surveys are sensitive to physical properties and therefore are widely used in mining exploration, especially in concealed terrains. The surveys can be performed at multiple scales, resulting in corresponding physical property datasets at different scales. Survey scale can vary from core or hand sample, involving few cubic centimeters, to regional-scale surveys providing information about physical property contrasts between distinct regional geological features. The understanding of the relationship between the physical property distributions with the sample volume (e.g. district, deposit, and drill-hole scale) is required where point scale physical property measurements are going to be consistent with measurements at larger volumetric scales during the integration of data for geophysical modeling The approach used to address the problem of understanding the scaling relations of physical properties, was achieved by considering them as second order stationary regionalized variables and then applying the random function formalism, provided by geostatistics theory. Geostatistics provide the required framework to characterize, quantify, model and link the spatial variability of the random variable at the different volumetric scales. The aim of this study is to apply geostatistics to effectively integrate data collected at several scales and bring knowledge to the understanding of the scaling relations of magnetic susceptibility. For this purpose, measurements of magnetic susceptibility available from Flin Flon copper-zinc district in Canada will be used. The data available at point scale were collected with hand portable magnetic susceptibility meter. The larger volumetric scale dataset were acquired using frequency domain electromagnetic instruments capable of measuring larger sample volumes, and then used to obtain magnetic susceptibility models using geophysical inversion algorithms. Once different scale models of magnetic susceptibility were available, quantification of the scaling relation using geostatistics, specifically variogram models and dispersion variance were determined. The understanding provided by the scaling analysis of the Flin-Flon magnetic data is applied to data from the Rio Blanco copper district in central Chile. Magnetic susceptibility measurements collected with a hand magnetic susceptibility meter on drill-core is integrated in larger scale volumes used for geophysical inversion modeling of regional scale airborne magnetic field measurements to recover magnetic susceptibility models. The methodology resulting from this application of geostatistics is used to address the problem of integrating multiple scales of physical property data in an effective way. The resulting physical property models capture the small-scale magnetic susceptibility variability observed and can guide larger-scale variability within geophysical inversion models. Establishing reliable statistical correlations between physical properties and rock units controlling ore within deposits are crucial steps leading predictive mine exploration tools. Any numerical modeling approach to establish these correlations should consider in some way the scaling nature of both physical property and ore content. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate