Belmont, Australia
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Preisig G.,University of British Columbia | Eberhardt E.,University of British Columbia | Gischig V.,University of British Columbia | Roche V.,University of Alberta | And 5 more authors.
Geofluids | Year: 2015

The ability to generate deep flow in massive crystalline rocks is governed by the interconnectivity of the fracture network and its permeability, which in turn is largely dependent on the in situ stress field. The increase of stress with depth reduces fracture aperture, leading to a decrease in rock mass permeability. The frequency of natural fractures also decreases with depth, resulting in less connectivity. The permeability of crystalline rocks is typically reduced to about 10-17-10-15 m2 at targeted depths for enhanced geothermal systems (EGS) applications, that is, >3 km. Therefore, fluid injection methods are required to hydraulically fracture the rock and increase its permeability. In the mining sector, fluid injection methods are being investigated to increase rock fragmentation and mitigate high-stress hazards due to operations moving to unprecedented depths. Here as well, detailed understanding of permeability and its enhancement is required. This paper reports findings from a series of hydromechanically coupled distinct-element models developed in support of a hydraulic fracture experiment testing hypotheses related to enhanced permeability, increased fragmentation, and modified stress fields. Two principal injection designs are tested as follows: injection of a high flow rate through a narrow-packed interval and injection of a low flow rate across a wider packed interval. Results show that the development of connected permeability is almost exclusively orthogonal to the minimum principal stress, leading to strongly anisotropic flow. This is because of the stress transfer associated with opening of tensile fractures, which increases the confining stress acting across neighboring natural fractures. This limits the hydraulic response of fractures and the capacity to create symmetric isotropic permeability relative to the injection wellbore. These findings suggest that the development of permeability at depth can be improved by targeting a set of fluid injections through smaller packed intervals instead of a single longer injection in open boreholes. © 2014 John Wiley & Sons Ltd.


Harris A.C.,University of Tasmania | Percival I.G.,Geological Survey of New South Wales | Cooke D.R.,University of Tasmania | Tosdal R.M.,University of British Columbia | And 6 more authors.
Economic Geology | Year: 2014

The volcanosedimentary rocks that host the Au-rich porphyry Cu deposits of the Cadia Valley preserve the products of episodic volcanism that erupted into a large sedimentary basin. Volcanogenic sedimentation, including the Forest Reefs Volcanics, overwhelmed the fine-grained sedimentary component that characterized much of the Weemalla Formation. The Forest Reefs Volcanics evolved as a relatively low relief, multiplevent submarine volcanic complex. The vents comprised mafic to intermediate lava flows, cryptodomes, and subvolcanic intrusions (dikes and sills). Stacked lava sequences, including hyaloclastites, massive lavas, and their reworked equivalents, are up to 1 km thick, forming significant intrabasinal topography. Explosive volcanism occurred during the late stages of Forest Reefs Volcanics deposition. These air-fall deposits, combined with coexisting shallow-water faunal assemblages, imply that volcanism became locally emergent. Continuity of sedimentation between underlying deep marine basin deposits of the Weemalla Formation and Forest Reefs Volcanics, coupled with the predominance of sheet-like, laterally continuous debris flow and other coarsegrained sedimentary deposits, implies that volcanism and related sedimentation persisted in an active sedimentary basin marginal to an oceanic island arc. Deposition of the Forest Reefs Volcanics spanned the Late Ordovician to Early Silurian. Monzonite fragments (identical to the ore-related intrusions) are abundant in sedimentary breccias found at the top of the preserved volcanic stratigraphy. This finding, combined with available absolute ages of crosscutting intrusions and associated hydrothermal alteration and mineralization, suggests that some volcanosedimentary units were deposited synchronously with or immediately after the last known porphyry-related hydrothermal event in the Cadia Valley. The Au-rich porphyry deposits were therefore emplaced into an evolving sedimentary basin with episodic intrabasinal magmatism. Permeable horizons and volcanic lithofacies can preferentially host alteration and mineralization that can extend over several kilometers in lateral extent. This finding suggests that hydrological models of fluid flow in porphyry systems need to take basin architecture into account. © 2014 Society of Economic Geologists, Inc.


Jago C.P.,University of British Columbia | Tosdal R.M.,University of British Columbia | Cooke D.R.,University of Tasmania | Harris A.C.,University of Tasmania | Harris A.C.,Newcrest Mining Ltd
Economic Geology | Year: 2014

The moderately tilted and faulted Early Jurassic Mt. Milligan Au-Cu deposit provides a cross-section view of the hydrothermal alteration, sulfide mineralogy, and geochemical zonation of a silica-saturated alkalic porphyry system over a vertical distance approaching 700 m. Magnetite-bearing potassic alteration and associated Au-Cu form a core to the system in the central monzonitic stock and adjacent basaltic trachyandesite host rock. Lateral to the high-temperature core are sodic-calcic and inner and outer propylitic alteration assemblages. Chalcopyrite dominates the high-temperature potassic core whereas pyrite is the predominant sulfide within and outboard from the sodic-calcic assemblage. A funnel-shaped remnant of carbonate-rich phyllic alteration of the host supracrustal rocks in the fault-bounded 66 zone represents the upper auriferous alteration in the alkalic porphyry Au-Cu system. Alteration mineral assemblage, S isotope (ranging from δ34S -5% relative to Canon Diablo Troilite in the core to δ34S +0.5% in the periphery), and limited fluid inclusion data suggest mineralization at the Au-Cu alkalic porphyry system was derived from an oxidized, CO2-bearing magmatic fluid that rose upward along the margins and through the Magnetite Breccia stock. Laterally from the Au-Cu mineralized potassic core, magmatic fluid evolved through water-rock interaction, mixing with an external fluid as shown by a shift in calculated 87Sr/86Sr0 for alteration minerals to values higher than magmatic values, declining temperature, or some combination of all. Variations in trace element concentrations of epidote (V, Mn, Sb, Zr, As, and Bi) and pyrite (Mn, As, Zr, Pb, and Bi) across the deposit show a local high degree of variability, but general increases or decreases in overall trends in their median values are inferred to reflect the hydrothermal evolution of the system. Pistachite ratios of epidote show an outward decrease in ferric iron as recorded in the pistachite ratio changing from PS36 to PS25, suggesting less oxidizing conditions on the system periphery. Additionally, light rareearth elements in epidote fractionate toward the core of the deposit, and the height of positive Eu anomalies also appears to have a similar spatial trend. In pyrite, there is a general increase in trace element concentration toward the epidote-pyrite-rich outer propylitic assemblage forming the system periphery. Alteration mineralogy and trace element signatures indicate the southeastern portion of the deposit, the 66 zone, is a down-dropped segment from higher in the paleohydrothermal system. S isotope signatures of sulfides within and surrounding the stratiform Upper Trachyte unit in the 66 zone indicate structural channeling of oxidizing fluids that likely were the distal and cooler expression of more oxidizing magmatic-derived hydrothermal fluids responsible for potassic alteration and Au-Cu in the subjacent Magnetite Breccia zone, the main orebody. © 2014 Society of Economic Geologists, Inc.


Burns F.,Julius Kruttschnitt Mineral Research Center | Burns F.,Newcrest Mining Ltd | Peng Y.,Julius Kruttschnitt Mineral Research Center | Peng Y.,University of Queensland | And 2 more authors.
Minerals Engineering | Year: 2014

This study examined the performance of the CIL (Carbon-in-Leach) circuit at Telfer, a copper-gold plant treating porphyry copper deposits containing gold associated with both copper and iron sulphides, with an objective to identify factors normally limiting the gold recovery in the CIL circuit in the presence of a small amount of copper after copper flotation, and then propose a means to improve it. Diagnostic leaching assessment and mineralogical analysis by MLA revealed that the occlusion of gold by other minerals and the fine grain size of gold associated with them may be the contributing factors to the low gold recovery in the CIL circuit. Fine grinding of the CIL feed increased gold recovery significantly from the leaching process. However, it is interesting to find that fine grinding increased the amount of released copper ions which complex with cyanide resulting in significantly higher cyanide consumption. It is therefore proposed that regrinding of the CIL feed followed by copper flotation is an appropriate pre-treatment method for the CIL circuit. © 2013 Elsevier Ltd. All rights reserved.


Chen X.,Julius Kruttschnitt Mineral Research Center | Seaman D.,Newcrest Mining Ltd | Peng Y.,Julius Kruttschnitt Mineral Research Center | Peng Y.,University of Queensland | Bradshaw D.,Julius Kruttschnitt Mineral Research Center
Minerals Engineering | Year: 2014

The objective of this study is to understand the flotation behavior of copper and gold minerals after regrinding the rougher flotation concentrate with a high pyrite content. It was found that low Eh and dissolved oxygen (DO) were produced after regrinding due to the quick consumption of oxygen by the large amount of fresh pyrite surfaces created, resulting in poor flotation of copper and gold and their selectivity against pyrite. A number of methods were used to provide an oxidizing condition, including pre-aeration before flotation, regrinding in an oxidizing condition, and addition of different oxidizing agents during regrinding. It was found that all the oxidizing methods improved the flotation of copper and gold, however, the effectiveness of these methods varied from case to case. This study demonstrates the importance of oxidation during or after regrinding for the flotation of rougher flotation concentrates with high sulfide contents. © 2014 Elsevier Ltd. All rights reserved.


Wei R.,University of Queensland | Peng Y.,University of Queensland | Seaman D.,Newcrest Mining Ltd
Minerals Engineering | Year: 2013

This study was conducted to explain an inconsistent observation in the previous study that a lignosulfonate-based polymeric dispersant improved copper and gold flotation from high clay ores significantly in laboratory but clear improvement was not observed during the full-scale plant trial (Seaman et al., 2012). In this study the flotation of low and high clay ores after grinding with different grinding media was performed to understand the interaction of lignosulfonate dispersant and grinding conditions equipped with rheology measurements and EDTA (ethylene diamine-tetra acid) extraction. It was found that lignosulfonate dispersant mitigated the negative effect of clay minerals on copper and gold flotation when the amount of iron oxidation products originated from the grinding media was minimised. Mild steel media produced a great amount of iron oxidation products depressing copper and gold flotation and masking the role of the dispersant. © 2013 Elsevier Ltd. All rights reserved.


Brunton I.D.,Newcrest Mining Ltd | Brunton I.D.,University of Queensland | Fraser S.J.,CSIRO | Hodgkinson J.H.,CSIRO | Stewart P.C.,University of Queensland
International Journal of Rock Mechanics and Mining Sciences | Year: 2010

The literature discusses a number of theoretical, small, and full scale experimental programs, which have aimed at identifying parameters influencing sublevel caving (SLC) material flow behaviour, and therefore ore recovery and dilution. Historically, parameters directly influencing flow behaviour have been found to include the geometry of the extraction layout and drives, sublevel height, blast ring design, material characteristics of the blasted and waste material, and draw control methodology. To date, no detailed analysis of parameters influencing full scale material flow behaviour and recovery in modern SLC mines has been documented in the literature. This paper outlines the analysis undertaken to identify parameters which influence material recovery at the Ridgeway SLC operation. Parameters analysed included those related to drawpoint location, drill and blast design, geology, drawpoint geometry, and draw control. To identify parameters influencing recovery, a Self-Organising Map (SOM) technique was adopted. SOM is considered an ideal tool for analysing complex geological and mining datasets, and for extracting relationships and patterns that typically are not evident by other means. The SOM analysis indicated that a number of drill and blast design parameters were directly or inversely correlated to material recovery at the Ridgeway SLC operation. Blasting parameters dominated correlations with recovery when compared to drawpoint and geological parameters. © 2010 Elsevier Ltd.


Lowther R.J.,Newcrest Mining Ltd
Shotcrete: Elements of a System - Proceedings of the 3rd International Conference on Engineering Developments in Shotcrete | Year: 2010

The Application of Fibre Reinforced Shotcrete (FRS) at Newcrest Mining Limited's Cadia Hill Open Pit has been effective in reducing the exposure of personnel and equipment to rockfall events. This has been achieved through applying Fibre Reinforced Shotcrete to the infill of large structures as well as to areas of poor rock mass in order to contain material that may unravel over time. © 2010 Taylor & Francis Group, London.


Peng Y.,University of Queensland | Peng Y.,BHP Billiton | Seaman D.,BHP Billiton | Seaman D.,Newcrest Mining Ltd
Minerals Engineering | Year: 2011

In this work, the flotation of slime-fine fractions of Mt. Keith pentlandite ore was studied in de-ionised water, and bore water with high ionic strength. Compared with de-ionised water, bore water increased pentlandite flotation significantly while decreasing serpentine flotation. Carboxymethyl cellulose (CMC) was tested as a dispersant to improve pentlandite flotation in both de-ionised and bore water. The degree of substitute (DS) of CMC, an indication of the charge density, was found to be an important parameter. In de-ionised water, the higher the DS of CMC, the better the pentlandite flotation, while in bore water, the lower the DS of CMC, the better the pentlandite flotation. © 2011 Elsevier Ltd. All rights reserved.


Karanovic I.,Zoologisches Museum und Institute Hamburg | Karanovic I.,University of Tasmania | McKayc K.,Newcrest Mining Ltd
Journal of Natural History | Year: 2010

Two new species, Leicacandona pinkajartinyi sp. nov. and L. jula sp. nov., are described from the Great Sandy Desert, Western Australia. Both species have reduced posterior claws on the caudal ramus, but differ in carapace shape and the length of setae and number of segments on the second and third thoracopods. A cladistic tree based on 27 morphological characters and a tree based on geographic latitudes and longitudes of the localities where Leicacandona species have been collected so far were constructed. These two cladograms do not correspond completely, although some similarities exist. The results obtained here agree with those obtained for some other subterranean animals in Australia, and they are understood as independent colonizations of subterranean waters by a couple of widespread surface water species. © 2010 Taylor & Francis.

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