No description available.

Thesis (M.S.)--Ohio University, June, 2004. / Includes bibliographical references (p. 66-77).

Thesis (M.S.)--Ohio University, June, 2004. / Title from PDF t.p. Includes bibliographical references (p. 66-77)

No description available.

Major and trace element data for Damara granitoids distinguish three geochemically distinct granitoid groups, - crustal-melt granitoids, calc-alkaline granitoids and within-plate granitoids. The overwhelming majority of the Oamara granitoids are peraluminous crustal-melt leucogranites which have elevated ⁸⁷Sr/⁸⁶Sr ratios (> 0.710) and old model Nd ages (~ 2.0 Ga). Calc-alkaline diorites are metaluminous and have the lowest ⁸⁷Sr/⁸⁶Sr ratios (0.704 - 0.707) and model Nd ages (OM) in the range 1.1 -1.7 Ga. Within-plate granitoids are characterised by elevated high-field strength (HFS) abundances and have model Nd ages (OM) in the range 1.1 - 1.6 Ga. All Damara granitoids have model Nd ages (OM) older than about 1.0 Ga suggesting that intracrustal reworking was the dominant process and crustal growth was negligible. Damara granitoids define a hyperbola on an ∈ Sr vs. ∈ Nd diagram but cannot be modelled as simple binary mixtures between old continental crust and depleted mantle end-members. An episodic intracrustal remobilisation model is proposed to explain the hyperbola defined by granitoid data on an ∈ Sr vs. ∈ Nd diagram. Within the 10 km thick Damara metasedimentary pile ⁸⁷Sr/⁸⁶Sr ratios increase systematically with depth. This trend is accompanied by a decrease in ¹⁴³Nd/¹⁴⁴Nd ratios. Model Nd ages (CHUR) for the stratigraphically oldest Damara metasediments (Nosib Group) are about 2.0 Ga whereas the younger metasediments (Kuiseb Formation and Nama Group) have model Nd ages (CHUR) about 1.0 Ga reflecting sediment input from younger source terrains. The ratio of model ages (T^Nd_CHUR/T^Sr_BE) is used as an index of intracrustal reworking since it provides a measure of Rb/Sr fractionation (increases) relative to SmlNd fractionation. The older Damara metasediments (Nosib Group) have the highest model age ratios suggesting that their source terrains have suffered the largest amount of intracrustal reworking. However, the rate of intracrustal reworking was greatest in source terrains sampled by the younger Damara metasediments (Kuiseb Formation and Nama Group). This suggests that the rate of intracrustal reworking increased through time in the interval (2.0 - 1.0 Ga) in this segment of continental crust.

No description available.

No description available.

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 45-49). Also available via the World Wide Web.

Fracture distribution in a fold and thrust belt is commonly thought to vary depending on structural position, strain, lithology and mechanical stratigraphy. The distribution, geometry, orientation, intensity, connectivity and fill of fractures in a reservoir are all important influences on fractured reservoir quality. The presence of fractures is particularly beneficial in reservoirs that contain little matrix porosity or permeability, for example tight sandstones. In these examples fractures provide essential secondary porosity and permeability that enhance reservoir production. To predict how reservoir quality may fluctuate spatially, it is important to understand how fracture attributes may vary, and what controls them. This research aims to investigate the influence of structural position on fracture attribute variations. Detailed fracture data collection is undertaken on folded sandstone outcrops. 2D forward modelling and 3D model restorations are used to predict strain distribution in the fold-and-thrust belt. Relationships between fracture attributes and predicted strain are determined. Discrete Fracture Network (DFN) modelling is then undertaken to predict fracture attribute variations. DFN modelling results are compared with field fracture data to determine how well fractured reservoir quality can be predicted. Field data suggests strain is a major controlling factor on fracture formation. Fractures become more organised and predictable as strain increases. For example in high strain forelimb regions, fracture intensity and connectivity are high, and fracture orientations are consistent. In lower strain regions, fracture attributes are much more variable and unpredictable. Fracture variations often do not correspond to strain fluctuations, and correlations can be seen between fracture intensity and lithology. Reservoir quality is likely to be much more variable in low strain regions than high strain regions. DFN modelling is also challenging because fracture attribute variations in low strain regions do not correspond to strain, and therefore cannot be predicted.

abstract / Earth Sciences / Master / Master of Philosophy