44 research outputs found

    The genesis and evolution of the Drake Goldfield, north-eastern New South Wales, Australia

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    The Drake Goldfield, a part of which is known as ‘Mount Carrington’, is located in north-eastern New South Wales (NSW) Australia, and is largely centred around the town of Drake, 44 km east of Tenterfield, and ~ 800 km north of Sydney. It contains a number of low-intermediate sulphidation epithermal precious metal deposits including Mount Carrington, Kylo, Strauss, Red Rock, Lady Hampden, Silver King, White Rock and White Rock North, along with numerous other small deposits and prospects. These deposits occur exclusively within the Drake Volcanics which comprise a 60 × 20 km NW-SE trending sequence of Late Permian shallow volcanics and related epiclastics. The Drake goldfield has been mined and explored intermittently since 1886 for precious metals, particularly Au and Ag with the most recent mining activity by Mt. Carrington Mines (1988 to 1990) producing 22,951 oz of Au and 434,870 oz of Ag. Although being known and mined for over 100 years, there are only few detailed studies on the deposits associated with the Drake Volcanics as a whole. A 20 km diameter circular caldera, called the Drake Quiet Zone (DQZ), was identified by its low magnetic response in an MCM airborne magnetic survey. The known mineral camps have a clear spatial relationship concerning the interpreted faults and fractures that define the DQZ. Recently, White Rock Minerals Ltd reported an indicated resource of 23.3 Moz of Ag and 352 Koz of Au. The Drake Volcanics (~265 Ma) are calc-alkaline, conformably overlie the Razorback Creek Mudstone and are conformably overlain by the Gilgurry Mudstone. The Drake Volcanics are suggested to have formed in a shallow marine environment. Due to pervasive alteration throughout the Drake Volcanics, only immobile elements were reliable in determining any fractionation trends. The immobile elements Nb, Y, Zr and Ti showed a regular fractionation trend from rhyolitic through to andesitic. Whole-rock ICP-MS data shows a significant strontium depletion, which is related to the intense and pervasive alteration throughout the Drake Goldfield to vertical depths of at least 500 metres in some areas. The volcanics show moderate LREE enrichment with small negative Eu anomalies, and relative depletion in Nb, Ta and Ti, indicating a continental arc tectonic setting. The DQZ contains approximately concentric and quasi-radial faults and fractures, which formed shortly after the collapse of the caldera. Hydrothermal fluids migrated upwards through these faults and were responsible for quartz alteration of the tuffs, polymictic breccias and quartz precipitation within fractured wallrocks forming veins and hydrothermal breccias. Within the DQZ, a number of deposits and numerous prospects are hosted within the rhyolitic to basaltic (mostly dacitic and andesitic) crystal ± lithic ± vitric tuffs and hydrothermal breccias. Juvenile and vitric clasts are widespread and abundant throughout the Drake Volcanics, which suggests that the vitric and lithic fragments within the Drake Volcanics are from a localised source. The field mapping within the Kylo and Strauss open-cut suggests that the mineralised structures had similar orientations to the unmineralised structures. This suggests that they have been formed during the regional scale event. Intense and pervasive alteration is prominent throughout the Drake Goldfield. Three alteration facies have been identified, comprising argillic/sub-propylitic (quartz-illite-chlorite), phyllic (quartz-chlorite-muscovite-carbonate) and propylitic (epidote-chlorite-illite-carbonate and adularia-illite-carbonate). In the Ag-deposits (Mozart, Silver King, White Rock and White Rock North), propylitic alteration is the dominant facies, with minor argillic and phyllic alteration. Propylitic alteration mainly occurs in the basal part of the Au-, and Cu- dominant deposits, but conversely in the top part of the Ag- dominant deposits. There is no definitive relationship between lithology and mineralisation on the scale of the Drake Goldfield. Mineralisation at the Drake Goldfield is of the low to intermediate sulfidation epithermal style which is typically characterised by pyrite, sphalerite, galena and minor chalcopyrite associated with late Ag mineralisation and electrum. The paragenesis in the Drake Goldfield was pyrite I pyrite II sphalerite I + chalcopyrite I + galena I + electrum sphalerite II chalcopyrite II+ galena II + Ag. The ore-forming fluids within the deposit evolved as deposition proceeded from ~300 ÂșC (for Au deposition) to ~200 - 250 ÂșC (for sphalerite and galena) and down to ~ 117 - 195ÂșC (for Ag-mineralisation). Electrum within the Drake Goldfield has two distinct Au: Ag ratios 5(4):1 and 2:1. Overall, the chemistry of pyrite varies very little between the different morphological generations and between the various deposits. The trace elements within sphalerite from the Red Rock and White Rock deposits show similar characteristics (i.e., Co as solid solution). The galena within the Au- and Ag-dominant deposits contains significant Ag (up to 593 ppm). No significant textural or chemical zonation was found to occur within the sulphides analysed. The carbon and oxygen isotope results indicate that the fluids responsible for the precipitation of carbonates from across the Drake Goldfield had complex origins, involving extensive mixing of hydrothermal fluids from several sources including magmatic origin, meteoric fluids and fluids associated with low-temperature alteration processes. Sulphur isotope ratios of sulphide minerals indicate that although the sulphur was most likely derived from at least two different sources; magmatic sulphur was the dominant source while sedimentary-derived sulphur was more significant for the deposits distal from the DQZ, with the relative importance of each varying from one deposit to another. This study describes a low to intermediate sulphidation mineralisation style and the potential for porphyry environments at depth, using a combination of conventional and unconventional analytical and data processing techniques. Ar-Ar dating suggests most of the mineralisation within the Drake Goldfield is intimately related to the Late Permian volcanism. The mineralisation at the centre of the DQZ was directly associated with the main stage of volcanism at 265 Ma, while there was a minor Ag mineralisation in the White Rock area associated with distinctive later hydrothermal events at around ~251 Ma. This later mineralisation in the White Rock area is possibly associated with Permo-Triassic magmatism in the SNEO. The 251 Ma 39Ar/40Ar age for muscovite from the White Rock field implies that there must be an unknown intrusion at depth within the greater White Rock region close to this age responsible for the hydrothermal fluids. After a significant volcanic event happened in the subaerial environment at around 265 Ma in the Drake area, with the main caldera centred around the Mount Carrington deposits. This magmatic system possibly continued to be active for another 14 Ma. Initial hydrothermal fluids derived from this major heat and metal source travelled along with main structures/fractures within the caldera up to the surface, forming numerous near-surface epithermal deposits. The Au- (Cu)- intermediate-sulphidation deposits mainly occur within the centre of the DQZ, while the Ag low-sulphidation deposits mainly occur within the periphery. There is a high possibility that there may be localized heat sources at both the Red Rock and White Rock – White Rock North Fields. This study collectively indicates that there may be a porphyry system underlying the centre of the DQZ

    Agricultural Water Conservation: Tools, Strategies, and Practices

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    Water scarcity is a critical issue for agriculture, and, hence, efficient management and conservation practices for agricultural water use are essential for adapting to and mitigating the impacts of current and future discrepancy between water supplies and water demands. This Special Issue focuses on “Agricultural Water Conservation: Tools, Strategies, and Practices”, which aims to bring together a collection of recent cutting-edge research and advancements in agricultural water conservation. The Special Issue intends to give a broad overview focusing on on-farm water conservation practices, advanced irrigation tools and water technologies, and the best management practices and strategies for efficient water use in agriculture

    Nonlinear Systems

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    The editors of this book have incorporated contributions from a diverse group of leading researchers in the field of nonlinear systems. To enrich the scope of the content, this book contains a valuable selection of works on fractional differential equations.The book aims to provide an overview of the current knowledge on nonlinear systems and some aspects of fractional calculus. The main subject areas are divided into two theoretical and applied sections. Nonlinear systems are useful for researchers in mathematics, applied mathematics, and physics, as well as graduate students who are studying these systems with reference to their theory and application. This book is also an ideal complement to the specific literature on engineering, biology, health science, and other applied science areas. The opportunity given by IntechOpen to offer this book under the open access system contributes to disseminating the field of nonlinear systems to a wide range of researchers

    Infrastructure Design, Signalling and Security in Railway

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    Railway transportation has become one of the main technological advances of our society. Since the first railway used to carry coal from a mine in Shropshire (England, 1600), a lot of efforts have been made to improve this transportation concept. One of its milestones was the invention and development of the steam locomotive, but commercial rail travels became practical two hundred years later. From these first attempts, railway infrastructures, signalling and security have evolved and become more complex than those performed in its earlier stages. This book will provide readers a comprehensive technical guide, covering these topics and presenting a brief overview of selected railway systems in the world. The objective of the book is to serve as a valuable reference for students, educators, scientists, faculty members, researchers, and engineers

    Minimising mathematical anxiety in teaching mathematics and assessing student’s work

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    This paper builds up a theoretical perspective and supports a possibility of creating a special assessment environment for students, where mathematical knowledge and understanding can be assessed with a reduced number of external psychological factors that may affect such assessment. A concept of a zone with minimal effect of anxiety is introduced and described. Students’ successful work on extending the zone by means of a carefully selected chain of questions, where some questions only are part of a real assessment, allows students to reconsider their attitudes towards mathematics and assist teachers to identify some students’ main learning difficulties as of psychological character. Further suggestions about developing and investigating special assessment environments are outlined and discussed

    Brain-muscle axis during treatment of minimal hepatic encephalopathy with L-ornithine L-aspartate

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    Abstract Background: Minimal Hepatic Encephalopathy (MHE) is a fluctuant cognitive deficit, and a common complication of cirrhosis, with significant health and socioeconomic consequences. Oral L-Ornithine L-Aspartate (LOLA) has been proposed to treat MHE but mechanism and efficacy are unknown. This study hypothesises LOLA treatment will correlate with improvements in: 1) Cognitive function (primary endpoints) 2) Relation to Brain-muscle axis (secondary endpoints) Design and methods: This double-blinded placebo-controlled trial included 34 patients (LOLA n=14, placebo n=20) over 12 weeks. All underwent psychometric testing (PHES, CogstateTM, Stroop, Short Form-36). Secondary endpoints included brain volume, white matter microstructure, brain function (proton MR spectroscopy/ functional MRI); muscle power (handgrip strength, 6-minute-walk-test); anthropometry (upper limb skinfold); muscle metabolome (lateral vastus muscle biopsy LC-MS analysis). Results: Significantly more patients receiving LOLA reported improved energy levels, specifically in Vitality (SF36 subdomain). No differences in PHES, Cogstate and Stroop test performance occured. Change-in-biceps skinfold thickness demonstrated significant gain with LOLA compared to placebo, without differences in power. LC-MS experiments were not discriminatory. Whole Brain differences in FA and RD suggested reduced brain oedema (subcortical volume reduction and global white matter changes). No significant group differences in fMRI task/ resting activation were seen. Spectroscopy of ACC showed significantly higher unresolved glutamine-glutamate (Glx) complex levels with LOLA, also correlating with increased PPI use, and may represent LOLA-driven increased Krebs-cycling or a function of altered gut microbiome. Conclusion: No cognitive benefits were demonstrated. Improved quality of life measures maybe a nutritional consequence also relating to increased biceps skinfold thickness with LOLA. Effects on brain oedema are postulated. Future studies need higher powering to allow subanalysis by aetiology, and smaller voxels at basal ganglia are recommended. Attempts to replicate rising ACC Glx with LOLA and regions of interest identified on fMRI subanalysis may be fruitful.Open Acces

    An Investigation into Neuropsychological Profiles in Anorexia Nervosa and Associated Clinical and Demographic Variables

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    Objective: Treatment outcomes for anorexia nervosa (AN) remain unsatisfactory. Substantial research has investigated the neuropsychological effects of AN, often with mixed results. One explanation for the inconsistencies is that there exist several distinct neuropsychological profiles within AN. Profiles have been reported, though not associated with clinical or demographic variables, limiting their utility. Suboptimal statistical techniques may undermine these findings. Method: An existing dataset of healthy controls (HCs) and AN patients (n = 423) was subjected to secondary analysis using latent profile analysis and a neural network to investigate latent profiles and the existence of non-linear neuropsychological structure. Profiles were compared with respect to demographic and clinical variables. Results: The latent profile analysis revealed five AN neuropsychological profiles. Patients in a globally neuropsychologically impaired profile were older than those in a high-average with high verbal profile and weighed less than those in an average performance profile. A non-linear neural network failed to outperform a linear neural network on a diagnosis classification task. Discussion: The five-profile solution extended the neuropsychological groups previously found in the literature. This study is the first to successfully associate latent neuropsychological profile to clinically meaningful variables, though the profile in which differences were observed was tiny (7% of patients). None of the discovered profiles differed in terms of anxiety, undermining support for the noradrenergic hypothesis of AN. The failure of the non-linear neural network to outperform the linear network indicates that AN neuropsychological ability does not contain significant non-linearity, indicating that conventional statistical techniques can model them

    Demographic and Psychiatric Correlates of Performance Validity Profiles of Individuals Assessed Subsequent to Motor Vehicle Accidents

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    The current study explored the effects of cultural, demographic and psychiatric variables on Performance Validity Test (PVT) base rates of failure (BRFAIL) in 325 examinees with traumatic brain injury (TBI) following motor vehicle accidents. PVTs are widely used measures of credibility in neuropsychological assessment. Gaps in the PVT literature regarding the effects of various demographic, cultural, and psychiatric factors limit the generalizability of PVTs. Higher false-positive rates in minority groups may lead to the inaccurate characterization of members as noncredible, resulting in the denial of treatment and compensation following injuries. To address this gap in the literature, the first objective of the study explored the relationship between BRFAIL, and limited English proficiency, time spent in Canada, education, age, gender, and injury severity. Results indicated that examinees with limited English proficiency had higher BRFAIL on PVTs with low verbal mediation (i.e., tests that did not have verbal components beyond the instructions) compared to Anglophone Canadians. Examinees who had language interpreters had higher BRFAIL on PVTs with both high and low verbal mediation compared to examinees assessed in English. Examinees who immigrated to Canada had higher BRFAIL on both high and low verbal mediation PVTs compared to Canadian-born examinees. Examinees aged 40 to 49 and those with less than high school education had higher BRFAIL for low verbal mediation PVTs than other groups. There were no differences for gender or TBI severity on BRFAIL. These results may be explained by several cultural factors, including cultural concepts of distress and differences in health literacy, which may contribute to PVT BRFAIL. As such, neuropsychologists should consider the contribution of these cultural factors when interpreting PVT results of examinees who have immigrated to Canada. Another important gap in the literature is in regards the relationship between PVTs and dissociative symptoms (i.e., disrupted consciousness, affect, and memory). Findings on the effects of psychiatric factors (e.g., posttraumatic, depressive, and anxious symptoms) on PVT BRFAIL are mixed but generally indicate that PVTs are robust to psychiatric disorders except psychosis. However, disruptions in consciousness, memory, and affect due to dissociative pathology might be expected to interfere with test performance. The second objective of this study explored the relationship between BRFAIL and dissociative, posttraumatic, anxious, and depressive symptoms. Results indicated elevated rates of PVT BRFAIL for examinees with higher levels of self-reported posttraumatic, depressive, and anxious symptoms. Results also indicated that those with high self-reported dissociative symptoms had higher BRFAIL for verbally mediated PVTs. The findings suggest that dissociative symptoms may interfere with verbally mediated PVTs, and highlight the need for further research into the effects of dissociative pathology on neuropsychological and PVT performance. The current study demonstrated that previously unexplored cultural, demographic, and psychiatric factors are related to PVT performance, and may affect the interpretation of PVTs. Implications, limitations, and avenues for future research are discussed
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