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Environmental Chemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Geochemistry is the science that considers chemical species, reactions, and processes of rocks and minerals in the geosphere as they relate to the hydrosphere, atmosphere, biosphere, and anthrosphere.7 The influence of geochemistry on the anthrosphere and vice versa are important. As an example of a geochemical process, consider that carbon dioxide from the atmosphere dissolves in water in the hydrosphere and then reacts with limestone in the geosphere: CaCO3(s)+CO2(aq)+H2O↔Ca2++2HCO3-
Introduction
Published in A.C. McLean, C. D. Gribble, Geology for Civil Engineers, 2017
Geology is the study of the solid Earth. It includes the investigation of the rocks forming the Earth (petrology) and of how they are distributed (their structure), and their constituents (mineralogy and crystallography). Geochemistry is a study of the chemistry of rocks and the distribution of major and trace elements in rocks, rock suites, and minerals. This can lead to an understanding of how a particular rock has originated (pedogenesis), and also, in the broadest sense, to a knowledge of the chemistry of the upper layers of the Earth.
Environmental Chemistry and the Five Spheres of the Environment
Published in Stanley Manahan, Environmental Chemistry, 2017
Geochemistry is the science that considers chemical species, reactions, and processes of rocks and minerals in the geosphere as they relate to the hydrosphere, atmosphere, biosphere, and anthrosphere. In the geological time scale, consideration of the influence of the geochemistry of the anthrosphere has only very recently become important. As an example of a geochemical process, consider that carbon dioxide from the atmosphere dissolves in water in the hydrosphere and then reacts with limestone in the geosphere: CaCO3(s)+CO2(aq)+H2O↔Ca2++2HCO3−
Tectonic setting and mineralisation potential of the Cowley Ophiolite Complex, north Queensland
Published in Australian Journal of Earth Sciences, 2022
A. Edgar, I. V. Sanislav, P. H. G. M. Dirks
The Silurian–Carboniferous Hodgkinson Province is the largest sub-unit in the Mossman Orogen. It extends north–south for >500 km, and east–west from the coast to the Palmerville Fault (Withnall & Cranfield, 2013). The Hodgkinson Province consists mainly of marine siliciclastic sediments, with mafic volcanic units and fossiliferous limestone more common in the western successions (Bultitude et al., 1990; Poblete et al., 2021). Folding and thrusting events have disturbed much of the stratigraphy within the Hodgkinson Province. The major lithological units in the province are exposed along north–south-trending, thrust-bound belts, which comprise, from east to west, the Hodgkinson Formation, Chillagoe Formation, Mountain Creek Conglomerate, Mulgrave Formation and the Quadroy Conglomerate (Bultitude et al., 1990). The tectonic setting of the Hodgkinson Province remains enigmatic. An investigation of basalt geochemistry by Vos et al. (2006) concluded that the Hodgkinson Province formed within an evolving backarc setting, with extension driven by the eastward retreat of an outboard subduction complex. Other authors have suggested formation within a forearc setting associated with oblique slip subduction (Henderson, 1980, 1987), or a continental margin rift setting (Garrad & Bultitude, 1999).
Uranium in animals, vegetables and minerals: landscape geochemical and biogeochemical expressions of the Four Mile West sedimentary uranium deposit, South Australia
Published in Australian Journal of Earth Sciences, 2020
S. M. Hill, S. B. Hore, V. J. Normington
This study first characterises aspects of the surficial geochemical and biogeochemical expression of a deeply buried secondary uranium deposit. This, however, can be complicated in depositional settings where lateral physical transport can overwhelm otherwise subtle expressions of underlying mineralisation. In some cases, lateral transport and deposition can facilitate a surficial accumulation of target elements, such as U. This highlights the importance of providing a landscape geology perspective for interpreting surface geochemistry and biogeochemistry results. The recognition of landscape expressions linked to the buried mineral system, such as weathered stratigraphic sections, oxidised mineral systems and the landform expression of structural features (including faulted blocks) responsible for forming and preserving mineralisation, is also valuable in this case.
Geochemistry of uranium mill tailings in the Athabasca Basin, Saskatchewan, Canada: A review
Published in Critical Reviews in Environmental Science and Technology, 2019
Jared Robertson, M. Jim Hendry, T. Kotzer, Kebbi A. Hughes
Speciation of Se and Mo in the tailings is not well defined. Stability field diagrams for Se and Mo in the DTMF using tailings porewater pH and Eh data (Shaw et al., 2011) suggest SeO32- (Se(IV)) and MoO42- (Mo(VI)) are the dominant equilibrium aqueous species. The measured aqueous Se speciation, however, is approximately 65% Se(VI), suggesting the aqueous geochemistry of Se is not at equilibrium (Shaw et al., 2011). The cause of this disequilibrium is not clear, but slow Se(VI) reduction rates can be speculated to be due to a lack of readily available electron donors for Se(VI) reduction (either biotic or abiotic) and the diffusion-dominated nature of the tailings porewater. Selenium(VI) has higher mobility than Se(IV) (Das, Hendry, & Essilfie-Dughan, 2013); thus, the equilibrium speciation of Se in the tailings will influence the long-term Se porewater concentrations in the TMFs.