Geothermal energy has been harnessed in Australia for several decades for both direct use applications and power generation, but only at very small scale installations. Australia's geothermal resources are amagmatic and unconventional by the accepted definitions in other parts of the world centred on active volcanism or plate margin collision. Worldwide, there is a lack of experience in exploring for and developing unconventional resources, and few "deposit" or resource models to aide exploration. The conceptualisation of a range of geological environments amenable to geothermal resource development will underpin the large scale development of geothermal utilisation in Australia. This will include developing exploration models spanning the range of unconventional geothermal resources; from "EGS" or "Hot (Dry) Rock" where permeability stimulation is a pre-requisite, to "Hot Sedimentary Aquifer" where no permeability stimulation is required.

Tsunami inundation models are computationally intensive and require high resolution elevation data in the nearshore and coastal environment. In general this limits their practical application to scenario assessments at discrete communities. This paper explores the use of moderate resolution (250 m) bathymetry data to support computationally cheaper modelling to assess nearshore tsunami hazard. Comparison with high resolution models using best available elevation data demonstrates that moderate resolution models are valid at depths greater than 10 m in areas of relatively low sloping, uniform shelf environments, however in steeper and more complex shelf environments they are only valid to depths of 20 m or greater. In contrast, arrival times show much less sensitivity to resolution. It is demonstrated that modelling using 250 m resolution data can be useful in assisting emergency managers and planners to prioritise communities for more detailed inundation modelling by reducing uncertainty surrounding the effects of shelf morphology on tsunami propagation. However, it is not valid for modelling tsunami inundation.

This paper describes two studies modelling the potential impacts of extreme events under sea level rise scenarios in two potentially vulnerable coastal communities: Mandurah and Busselton in Western Australia. These studies aim to support local adaptation planning by high resolution modelling of the impacts from climate change.

In this study, we conducted a simulation experiment to identify robust spatial interpolation methods using samples of seabed mud content in the Geoscience Australian Marine Samples database. Due to data noise associated with the samples, criteria are developed and applied for data quality control. Five factors that affect the accuracy of spatial interpolation were considered: 1) regions; 2) statistical methods; 3) sample densities; 4) searching neighbourhoods; and 5) sample stratification. Bathymetry, distance-to-coast and slope were used as secondary variables. Ten-fold cross-validation was used to assess the prediction accuracy measured using mean absolute error, root mean square error, relative mean absolute error (RMAE) and relative root mean square error. The effects of these factors on the prediction accuracy were analysed using generalised linear models. The prediction accuracy depends on the methods, sample density, sample stratification, search window size, data variation and the study region. No single method performed always superior in all scenarios. Three sub-methods were more accurate than the control (inverse distance squared) in the north and northeast regions respectively; and 12 sub-methods in the southwest region. A combined method, random forest and ordinary kriging (RKrf), is the most robust method based on the accuracy and the visual examination of prediction maps. This method is novel, with a relative mean absolute error (RMAE) up to 17% less than that of the control. The RMAE of the best method is 15% lower in two regions and 30% lower in the remaining region than that of the best methods in the previously published studies, further highlighting the robustness of the methods developed. The outcomes of this study can be applied to the modelling of a wide range of physical properties for improved marine biodiversity prediction. The limitations of this study are discussed. A number of suggestions are provided for further studies.

The sediment-hosted Nifty Cu deposit is located 450 km east of Port Hedland in the Yeneena Basin of the Paterson Orogen in Western Australia. It is hosted within interbedded black carbonaceous shales and dolomitised micrites of the Broadhurst Formation. The host rocks have been folded and metamorphosed to lower greenschist facies in the Miles Orogeny (see also Czarnota et al. this volume). Textural relationships of the ore to host rock suggest syn-deformational (Miles Orogeny) timing of mineralisation (see also van der Wacht et al., this volume). Primary chalcopyrite preferentially replaces dolomitised micrite beds, occurs in black shales within the axial plane foliation, or as breccia infill. The ore and silica dolomite alteration envelopes trend from the keel of the Nifty Syncline and up the steeply dipping limb of the fold. There are two high grade ore trends (>1% Cu): one strikes NE-SW parallel to the fold axis and the other strikes N-S across the axis of the fold. Based on the inference that Nifty is a structurally controlled deposit that formed late, or after the establishment of the fold architecture, the question is why high grade ore is located in the keel and towards one limb of the asymmetric Nifty syncline. Assuming that post-folding dilation focussed flow of mineralising fluid(s) 2D and 3D coupled deformation/fluid flow simulations were carried out to examine why Nifty is in a syncline and what the controls on high grade ore trends may be. 2D models The 2D model geometry consists of a three layer stratigraphy folded in a series of asymmetric folds. The three-layer model represents the camp scale lithostratigraphy consisting of (i) a moderately competent and moderately permeable siltstone, (ii) a strong and permeable carbonate and (iii) a weak and impermeable shale. Contraction at hydrostatic pore pressure of this material layering resulted in focuses fluid flow down fluid pressure gradient occurred from the hinge of the syncline and up the steeply dipping limb of the fold driven by dilation higher up the limb. This dilation is a consequence of the location of a shear band that developed along the shallow dipping limb of the fold, above the competent carbonate unit, and intersected the steeply dipping limb of the syncline, adjacent to the syncline hinge. Models run using the same geometry but varying the stratigraphy to the mine sequence of shale-carbonate-shale showed focusing of fluid flow into anticlinal fold closures. This is a consequence of shear strain localisation below the competent carbonate unit and the intersection of the resultant shear band with the carbonate unit adjacent to the anticlinal fold closure. This scenario does not explain why Nifty is in a syncline. However this model may explain why the Telfer Ore deposit hosted in sediments with a similar competency contrast to this model (i.e. a sandstone unit between two weak carbonate units) is situated in a dome fold closure adjacent to the steeply dipping limb of the fold. Other models run on symmetrical folds showed similar results as the two models outlined above. However the shear bands in these models do not have preferential shallowly dipping fold limbs to localise on. 3D models A simple three layer 3D model of the Nifty syncline was constructed to examine the effects of (i) the nearby Vines Fault which was active during the Miles Orogeny as a major dextral strike-slip fault and (ii) the effects of the NW-SE directed Paterson Orogeny. The results of applying a dextral strike-slip velocity boundary velocity parallel to the NNW orientation of the Vines Fault produced high strain zones and associated dilation broadly coincident with the second direction of high grade ore trends. Deformation under the Paterson stress field i.e. perpendicular to the fold axis, resulted in shear strain localisation along inflections in the fold axis away from regions of mineralisation....

During 2009-11 Geoscience Australia completed a petroleum prospectivity study of the offshore northern Perth Basin as part of the Australian Government's Offshore Energy Security Program. A significant component of the program was the acquisition of a regional 2D reflection seismic and potential field survey GA-310 in 2008/09. Basement in the northern Perth Basin is deep and generally not resolved in the reflection seismic data. This study models the observed gravity in 2.5D along two southwest trending dip-direction reflection seismic transects across WA11-18 to provide insight into the likely sediment thickness and basement topography. Three cases and ten models are examined according to assumptions about possible target depth to basement, and assumptions about Moho depth

Integration of disparate sets of geophysical data, such as Bouguer gravity, magnetotelluric and seismic travel time data for a robust interpretation of architectural settings of the subsurface is carried out. At the outset, the layered 2D model space is appropriately gridded. A spline node layer boundary parameterisation with a sigmoid basis function is used to relate local 1D layered model parameterisation to the 2D model space. Joint 1D inversion of seismic travel time and magnetotelluric data is carried out at the spline nodes using empirical relationships between seismic velocity and resistivity. The two objective functions corresponding to each of the input data types are combined through a weighting factor, the appropriate value of which is determined using the L-curve technique. The particle swarm optimization scheme is used as a robust optimiser for the layer depths and property values. The inverted velocity model is transformed to a density model using a second empirical rock property relationship. A 2D inversion of Bouguer gravity data is then carried out producing adjustments to the depths for the layer boundaries. This completes the initialisation phase of the procedure. A second iterative phase during which only the depths to the layer boundaries are modified is carried out to build a coherent model which is consistent with all three kinds of data. This involves re-inverting jointly the seismic travel time and magnetotelluric data, where parameters corresponding to the rock properties are kept unaltered, but the depth to the layer interfaces are updated. The method is trialled with a synthetic situation and is implemented to interpret the architectural settings of newly discovered Millungera basin of North Queensland, Australia.

Nutrients dynamics in estuaries are temporarily variable depending on changing physical-chemical conditions and the response of functional primary producer groups such as phytoplankton, microphytobenthos, seagrass and macroalgae. In order to reveal temporal regime shifts in primary producer groups and associated changes in estuarine nutrient dynamics we developed a box-model coupling the hydrology and nitrogen dynamics in Wilson Inlet, a large, central basin dominated, intermittently closed estuary exposed to Mediterranean climate. The model is calibrated and validated with monitoring data, aquatic plant biomass estimates and biogeochemical rate measurements. Macrophytes and their microalgal epiphytes appear to rapidly assimilate first flush nutrients from the catchment in winter, but this buffer capacity then ceases and a phytoplankton bloom develops in response to subsequent river run-off events in spring. In late spring to autumn high light availability stimulates high primary production by microphytobenthos leading to reduced benthic ammonia fluxes particularly in deep basin areas and contributing about 50% of annual whole-system primary production. Significant amounts of bioavailable nitrogen are flushed out, because phytoplankton predominance occurs concurrently with the opening of the bar.

Abstract # : 1479734 Paper # : GP43B-1142 Session : GP43B Potential-field and EM methods for geologic problems of the mid and upper crust Developments for 3D gravity and magnetic modeling in spherical coordinates Richard Lane - Geoscience Australia - rjllane@gmail.com Qing Liang - China University of Geosciences (Wuhan) - qingliang.cug@gmail.com Chao Chen - China University of Geosciences (Wuhan) - chenchao@cug.edu.cn Yaoguo Li - Colorado School of Mines - ygli@mines.edu At Geoscience Australia (GA), Australia's Commonwealth Government geoscientific agency, we perform gravity and magnetic modeling at a range of scales, from broad regional crustal studies with thousands of kilometer lateral extent and tens of kilometer vertical extent, to detailed local studies with kilometer or less lateral extent and meters to hundreds of meters vertical extent. To achieve greater integration and coherence, and to better understand the geological significance of this work, we are investing in a number of development projects; * Spherical coordinate gravity and magnetic modeling, * Modeling using High Performance Computing facilities, * Utilizing rock property data as an input into the modeling and interpretation of gravity and magnetic data, * Better management of geoscience data and models, and * Visualization of spatial data in a Virtual Globe format. In collaboration with the Colorado School of Mines (CSM) and the China University of Geosciences (CUG), we are developing a capability to model gravity and magnetic data in a spherical coordinate framework. This will provide more accurate calculations and permit us to integrate the results into a single framework that more realistically reflects the shape of the Earth. Modeling gravity and magnetic data in a spherical coordinate framework is far more compute intensive than is the case when performing the corresponding calculations in a Cartesian (rectangular) coordinate framework. To reduce the time required to perform the calculations in a spherical coordinate framework, we will be deploying the modeling software on the National Computational Infrastructure (NCI) High Performance Computing (HPC) facility at the Australian National University (ANU). This will also streamline the management of these software relative to the other main option of establishing and maintaining HPC facilities in-house. We are a participant in the Deep Exploration Technologies Cooperative Research Centre (DET CRC). In combination with this involvement, we are expanding our support for systematic management of rock property data, and developing a better understanding of how these data can be used to provide constraints for the modeling work. We are also using the opportunities afforded through the DET CRC to make progress with documentation and standardization of data storage and transfer formats so that the tasks of management, discovery and delivery of this information to users are simplified and made more efficient. To provide the foundations of integration and analysis of information in a spatial context, we are utilizing and customizing 3D visualization software using a Virtual Globe application, NASA World Wind. This will permit us to view the full range of information types at global to local scales in a realistic coordinate framework. Together, these various development activities will play an important role in the on-going effort by Geoscience Australia to add value to the potential field, rock property, and geological information that we possess. We will then be better able to understand the geology of the Australian region and use this knowledge in a range of applications, including mineral and energy exploration, natural hazard mitigation, and groundwater management.

No abstract available