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Geothermal energy
Published in John Twidell, Renewable Energy Resources, 2021
In principle, in both hyperthermal and semithermal regions heat may be obtained from: Natural hydrothermal circulation of water, which heats as it percolates to deep aquifers and reappears as dry steam, a vapor/liquid mixture, or hot water. Such natural phenomena are not uncommon. If pressure increases by steam formation at deep levels, spectacular geysers may occur, as at the geysers near Sacramento in California and in the Wairakei area near Rotorua in New Zealand (see Fig. 14.4). Note, however, that liquid water is ejected, and not steam.Hot igneous systems associated with heat from semi-molten magma that solidifies to lava. The first power plant using this source was the 3 MWe station in Hawaii, completed in 1982.Dry rock fracturing. Poorly conducting dry rock (e.g. granite) stores heat over millions of years with a subsequent increase in temperature. Artificial fracturing from boreholes enables water to be pumped through the rock, so that (in principle) the heat can be extracted. However, there are many practical difficulties with this; see §14.4.3.
Energy and Environment
Published in T.M. Aggarwal, Environmental Control in Thermal Power Plants, 2021
Electricity generation requires high temperature resources that can only come from deep underground. The heat must be carried to the surface by fluid circulation, either through magma conduits, hot springs, hydrothermal circulation, oil wells, drilled water wells, or a combination of these. This circulation sometimes exists naturally where the crust is thin: magma conduits bring heat close to the surface, and hot springs bring the heat to the surface. If no hot spring is available, a well must be drilled into a hot aquifer. Away from tectonic plate boundaries the geothermal gradient is 25–30°C per kilometre (km) of depth in most of the world, and wells would have to be several kilometres deep to permit electricity generation. The quantity and quality of recoverable resources improves with drilling depth and proximity to tectonic plate boundaries.
Current status of coastal sediments contamination in the former industrial area of Bagnoli-Coroglio (Naples, Italy)
Published in Chemistry and Ecology, 2020
Giovanna Armiento, Raffaela Caprioli, Antonietta Cerbone, Salvatore Chiavarini, Cinzia Crovato, Maurizio De Cassan, Luigi De Rosa, Maria Rita Montereali, Elisa Nardi, Luigi Nardi, Massimo Pezza, Marco Proposito, Juri Rimauro, Agostino Salerno, Antonio Salluzzo, Fabio Spaziani, Fabio Zaza
The geological setting of the area has been extensively studied over the years by several authors ([19–22], among the others). The overall area is characterised by the presence of two main active volcanic districts, Phlegrean Fields and Mt. Somma-Vesuvius, developed along coastland, the Gulf of Pozzuoli representing the submerged sector of Phlegrean Fields [11]. The substrate of the study area consists of Neapolitan Yellow Tuff (12,000 yBP), followed by a more recent sequence of interdigitated pyroclastics produced by many volcanic and tectonic events. At the top of the sequence, there are lacustrine and palustrine sediments. Moreover, hydrothermal springs were identified in the Gulf of Pozzuoli with NW-SE arrangement [23]. The Phlegrean Fields, built up by mafic to felsic alkaline potassic magmas [24], in the quiescent state since 1538 A.D., are currently the site of intense hydrothermal circulation, the surface manifestations of which include hot springs, steam-heated pools, and submarine and subaerial fumarole emissions within the bay of Pozzuoli and the Solfatara volcano, favouring the transfer of arsenic from deep-seated reservoir(s) to the surface, and the consequent development of arsenic-rich groundwater [5]. These fluids contain also other heavy and potentially toxic metals [8] giving to the rocks and soils of the area a relatively high background content of potentially toxic elements [6].
Cretaceous molybdenite in metasomatic epidosite associated with the Pounamu ophiolite, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2020
Alan F. Cooper, Anthony Reay, Trevor R. Ireland, Marc D. Norman
If Mo is not derived from quartzofeldspathic schists, the only other potential source would be in the pelagic metasedimentary rocks that directly overlie the mafic components of the Pounamu ophiolite. Calvert and Pedersen (1993) have shown that Mo is greatly enriched in deep sea sediments formed under anoxic conditions. Sun et al. (2016) have proposed that during weathering of continental crust, Mo is oxidised to water-soluble (MoO4)2-, and, when transported to the world’s oceans, may interact during oceanic anoxic events with deep-sea sediments precipitating Mo sulphides or other complexes. Sediments, either quartzofeldspathic or pelagic, despite their low concentrations, could be leached of Mo during accretion, subduction, or the attendant Cretaceous Alpine metamorphism-metasomatism, and mobilised by dehydration-induced hydrothermal circulation.
Strategic elements in the Fort Cooper Coal Measures: potential rare earth elements and other multi-product targets
Published in Australian Journal of Earth Sciences, 2020
J. H. Hodgkinson, M. Grigorescu
Lithium concentrations have been found to be high in the northern-most borehole and would be worthy of further investigation to discover the likely source and lateral extent of the anomaly. Although Li is a relatively abundant element in the Earth’s crust, it is rarely found in concentrations sufficient to warrant mining owing to geological constraints (Kesler et al., 2012). Qin, Zhao, Li and Zhang (2015) estimated that Li concentrations in coal should be at a minimum of 80 ppm and ideally 120 ppm to be of economic or industrial grade. Given that only one sample shows relatively high Li concentration (105 ppm), tuffaceous-rich tailings produced in the area should be analysed when available. It would also be valuable to analyse samples from the coal and waste from over- and underlying coal measures in that locality to determine whether Li content is consistently elevated, and whether it has been influenced by groundwater or hydrothermal circulation.