31 research outputs found
Gold in Devono-Carboniferous red beds of northern Britain
We are grateful to D. Craw and an anonymous reviewer for comments that helped to clarify the paper. Research was funded by NERC grants NE/L001764/1 and NE/M010953/1.Peer reviewedPublisher PD
High molybdenum availability for evolution in a Mesoproterozoic lacustrine environment
Peer reviewedPostprin
Mesoproterozoic surface oxygenation accompanied major sedimentary manganese deposition at 1.4 and 1.1 Ga
This research was funded by the Australian Science and Industry Endowment Fund (SIEF) as part of The Distal Footprints of Giant Ore Systems: UNCOVER Australia Project (RP04-063)—Capricorn Distal Footprints. EAS also thanks the donors of The American Chemical Society Petroleum Research Fund for partial support of this research (61017-ND2).Peer reviewedPublisher PD
Mineralogy and geochemistry of atypical reduction spheroids from the Tumblagooda Sandstone, Western Australia
Funding Information: This research was supported by a CSIRO Mineral Resources studentship, a Curtin University student scholarship and a Minerals Research Institute of Western Australia scholarship. The editors of Sedimentology and three anonymous reviewers are acknowledged for their assistance in improving the manuscript. We would also like to thank Mike Paxman and the Parks and Wildlife Service for permission to sample in Kalbarri National Park. Finally, the authors would like to pay tribute to the memory of Professor Nigel Trewin, whose work laid much of the foundation for this study and many others on the Tumblagooda Sandstone.Peer reviewedPostprin
High-charge 10 GeV electron acceleration in a 10 cm nanoparticle-assisted hybrid wakefield accelerator
In an electron wakefield accelerator, an intense laser pulse or charged
particle beam excites plasma waves. Under proper conditions, electrons from the
background plasma are trapped in the plasma wave and accelerated to
ultra-relativistic velocities. We present recent results from a
proof-of-principle wakefield acceleration experiment that reveal a unique
synergy between a laser-driven and particle-driven accelerator: a high-charge
laser-wakefield accelerated electron bunch can drive its own wakefield while
simultaneously drawing energy from the laser pulse via direct laser
acceleration. This process continues to accelerate electrons beyond the usual
decelerating phase of the wakefield, thus reaching much higher energies. We
find that the 10-centimeter-long nanoparticle-assisted wakefield accelerator
can generate 340 pC, 10.4+-0.6 GeV electron bunches with 3.4 GeV RMS convolved
energy spread and 0.9 mrad RMS divergence. It can also produce bunches with
lower energy, a few percent energy spread, and a higher charge. This
synergistic mechanism and the simplicity of the experimental setup represent a
step closer to compact tabletop particle accelerators suitable for applications
requiring high charge at high energies, such as free electron lasers or
radiation sources producing muon beams
Redox-controlled selenide mineralization in the Upper Old Red Sandstone
<p>Selenium concentrations occur in organic-rich lithologies such as coal, and as secondary accumulations from the oxidative
mobilization, migration and subsequent concentration upon encountering reductants such as organic matter or H<sub>2</sub>S. Here we assess the redox mineralization of copper and lead selenide phases in the cores of reduction spheroids in Devonian
sedimentary red beds. We propose that the selenide mineralization occurred as descending meteoric fluids, supplied with selenium
from Carboniferous coal seams, migrated through a major fault plane into underlying sandstones where localized, microbially-induced
reducing conditions prevailed. These findings and other occurrences of selenide mineralization between Devonian and Carboniferous
strata on the British Isles suggest a widespread selenide mineralization system between strata of that age.
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Multi-Media Geochemical Exploration in the Critical Zone: A Case Study over the Prairie and Wolf Zn–Pb Deposits, Capricorn Orogen, Western Australia
In this study, we compared traditional lithochemical sample media (soil) with hydrochemical (groundwater), biogeochemical (plant matter of mulga and spinifex), and other near-surface sample media (ferro-manganese crust), in a case study applied to mineral exploration in weathered terrain, through the critical zone at the fault-hosted Prairie and Wolf Zn–Pb (Ag) deposits in Western Australia. We used multi-element geochemistry analyses to spatially identify geochemical anomalies in samples over known mineralization, and investigated metal dispersion processes. In all near-surface sample media, high concentrations of the metals of interest (Zn, Pb, Ag) coincided with samples proximal to the mineralization at depth. However, the lateral dispersion of these elements differed from regional (several km; groundwater) to local (several 100′s of meters; solid sample media) scales. Zinc in spinifex leaves over the Prairie and Wolf deposits exceeded the total concentrations in all other sample media, while the metal concentrations in mulga phyllodes were not as pronounced, except for Ag, which exceeded the concentrations in all other sample media. These observations indicate potential preferential metal-specific uptake by different media. Pathfinder elements in vegetation and groundwater samples also indicated the Prairie Downs fault zone at the regional (groundwater) and local (vegetation) scale, and are, therefore, potentially useful tools to trace fault systems that host structurally controlled, hydrothermal Zn–Pb mineralization
Water Radiolysis: Influence of Oxide Surfaces on H2 Production under Ionizing Radiation
The radiolysis of water due to ionizing radiation results in the production of electrons, H· atoms, ·OH radicals, H3O+ ions and molecules (dihydrogen H2 and hydrogen peroxide H2O2). A brief history of the development of the understanding of water radiolysis is presented, with a focus on the H2 production. This H2 production is strongly modified at oxide surfaces. Different parameters accounting for this behavior are presented