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Posts Tagged ‘free article’

Deep-Ocean Mineral Deposits: Metal Resources and Windows into Earth Processes

Deep-ocean mineral deposits could make a significant contribution to future raw material supply. Growing metal demand and geopolitics are focussing increasing attention on their resource potential and economic importance. However, accurate assessment of the total amounts of metal and its recoverability are very difficult. Deep-ocean mineral deposits also provide valuable windows through which to study the Earth, including the evolution of seawater and insights into the exchange of heat and chemicals between the crust and the oceans. Exploration for, and potential extraction of, deep-ocean mineral deposits poses many geological, technical, environmental and economic challenges, as well as regulatory and philosophical questions. Great uncertainty exists, and the development and stewardship of these deposits requires an incremental approach, encouraging transparency and scientific and civil societal input to balance the interests of all.

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Responsible Sourcing of Critical Metals

Most critical raw materials, such as the rare-earth elements (REEs), are starting products in long manufacturing supply chains. Unlike most consumers, geoscientists can become involved in responsible sourcing, including best environmental and social practices, because geology is related to environmental impact factors such as energy requirements, resource efficiency, radioactivity and the amount of rock mined. The energy and material inputs and the emissions and waste from mining and processing can be quantified, and studies for REEs show little difference between ‘hard rocks’, such as carbonatites, and easily leachable ion-adsorption clays. The reason is the similarity in the embodied energy in the chemicals used for leaching, dissolution and separation.

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Chalcophile Elements and Sulfides in the Upper Mantle

Sulfides are among the most important petrogenetic agents in magmatic systems. They are ubiquitous in most upper-mantle rock types, common as inclusions in diamonds and they host significant amounts of geochemically and economically important chalcophile (‘sulfur-loving’) elements, such as Cu, Ni, Pb, In, Au and the platinum-group elements. Despite their low abundance (<< 1% of the bulk rock), residual sulfides have a disproportionate control over the chalcophile element budget in upper mantle lithologies, as well as that of melts derived from the Earth’s mantle.

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Mineralogy of Sulfides

Metal sulfides are the most important group of ore minerals. Here, we review what is known about their compositions, crystal structures, phase relations and parageneses. Much less is known about their surface chemistry, their biogeochemistry, or the formation and behaviour of ‘nanoparticle’ sulfides, whether formed abiotically or biogenically.

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