School of Earth Sciences - Theses
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ItemHeat flow modelling in the Adelaide Geosyncline, South Australia and implications for geothermal resource exploration( 2008)The central theme of this research is the continental heat flow at the surface of the Earth. Radioactive heat production in the lithosphere and heat flux from convection in the asthenosphere are first order controls on surface heat flow. Accurate heat flow determinations are essential in understanding the geodynamics of the lithosphere and refining resource exploration models, in particular those related to geothermal resources. The focus of this investigation is confined to the understanding of heat refraction as a result of the heterogeneity and anisotropy of the geological subsurface, under a steady-state heat conduction regime. Within the South Australian Heat Flow Anomaly, an area of particular significance for geothermal resource exploration is the deep seated Torrens Hinge Zone, a strip of tectonic transition between the Archaean Gawler Craton to the west and the Neoproterozoic to Cambrian sedimentary cover of the Adelaide Geosyncline to the east. (For complete abstract open document)
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ItemNeogene vertical motions in intraplate settings: case studies from Australia and Korea( 2012)The lithosphere is dynamically linked with the large-scale dynamics in the convective mantle beneath. While the horizontal lithospheric movements are now well understood in a framework of plate tectonics, it is still a challenge to explain the vertical motions of the Earth’s surface, especially in intraplate regions. Such movements may arise from a variety of causes, such as upper mantle flow and lithospheric responses to plate boundary forces. This thesis explores the unique records of vertical motion in two settings. In Southeast Australia, tectonic modes and rates during the Late Neogene are established from uplifted marine terraces and other geomorphic constraints. Uplift of southern Victoria has occurred at rates of up to ~55 m Myr-1 during the Quaternary, and the rate of uplift has increased progressively since the Middle Pliocene. Non-uniform uplift of coastal Tasmania varies from ~40 m Myr-1 to ~112 m Myr-1. Spatial variations of vertical motions in southern Victoria and Tasmania is order 100’s kms, and is largely explicable in terms of lithospheric flexure, in response to contemporary plate boundary forces coupled with localised lithospheric failures, superimposed on a longer wavelength dynamic topography. The eastern margin of NE Asia, including Korea, sits in the back-arc setting to the Western Pacific Subduction Zone, in the vicinity of a complex trench triple junction of the Philippine, Pacific, and Eurasian plate. Geochronology of the Quaternary marine terraces and fission track dating results of upper Cretaceous granites imply maximum uplift rates of 45.3±1.1 m Myr-1 during the Neogene and 168±16 m Myr-1 in the Late Quaternary. Maximum uplift rates correspond in a general sense with a belt of Quaternary mafic intraplate volcanism suggesting the uplift can be attributed to asthenospheric upwelling around the edges of the sinking Western Pacific slab. The edges of the subducting slab are currently located beneath the eastern margin of the peninsula at a depth of 600 km. In addition, plate boundary forces arising from interactions between the Pacific, Asian and Philippine plate contribute to lithospheric failure relating with faulting movements in the peninsula since the Late Neogene. This research on the long- term vertical deformation field of the continents provides new insights into the way in which the internal dynamics of the Earth modify the surface with the various scales driven by both lithospheric and sub-lithospheric processes.