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April 2017 Archives - Elements
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Posts Tagged ‘April 2017’

RSC Names New Fellows; NAE Elects Rodney Ewing

Dominique Weis (Department of Earth, Ocean and Atmospheric Sciences, the University of British Columbia, Canada) and David Graham Pearson (Department of Earth and Atmospheric Sciences, University of Alberta, Canada) were inducted as Fellows of the Royal Society of Canada.

The National Academy of Engineering (USA) announced that Rodney C. Ewing was elected as a member to the academy.

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Marine Geochemistry

Climate change, ocean acidification, coral bleaching, marine “dead zones”… for better or worse, the Anthropocene is certainly proving to be an interesting time for marine science, and particularly for marine geochemistry. Add to this the advent of vast and vastly accessible information, as well as technological advances in analytics and computing, and you are left with a virtually endless potential for scientific inquiry. And certainly the field of marine geochemistry is growing in all directions, as researchers push the boundaries of the science. Marine geochemists can now measure how isotopes of elements found in the oceans at pico-molar levels vary across entire ocean basins, and model what this implies for global change over millennia past and those to come! Heady times to be a marine geochemist. More importantly, it is a critical time to teach and inspire the next generations of marine geochemists so that they may keep forging ahead. As such, Marine Geochemistry by Roy-Barman and Jeandel comes at an opportune moment.

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Sedimentary Sulfides

Sedimentary sulfides constitute over 95% of the sulfide on the surface of the planet, and their formation, preservation and destruction largely determines the surface environment. The sulfide in sediments is mainly derived from the products of sulfate-reducing bacteria, which are currently responsible for oxidizing over half the organic matter flux reaching sediments. Pyrite is the mineral overwhelmingly produced. The geochemistry of pyrite, both in terms of its isotopic composition and its trace-element loading, has varied dramatically over geologic time. As such, it is a major source of our current understanding about the nature of the early Earth and of the Earth’s subsequent geochemical and biological evolution.

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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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Volcanic Sulfides and Outgassing

Sulfides are a major potential repository for magmatic metals and sulfur. In relatively reduced magmas, there may be a dynamic interplay between sulfide liquids and magma degassing as magmas ascend/erupt. Sulfide-bubble aggregates may segregate to shallow levels. Exsolved fluids may oxidize sulfides to produce SO2 gas and metals, which can vent to the atmosphere with chalcophile metal ratios reflecting those in their parent sulfide liquids. Sulfide breakdown and/or sequestration timing and balance define the role of sulfides in both ore formation and the environmental impacts of volcanic eruptions, including during the evolution of large igneous provinces, which are key periods of heightened volcanism during Earth history.

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Sulfide Minerals in Hydrothermal Deposits

Hydrothermal ore deposits are large geochemical anomalies of sulfur and metals in the Earth’s crust that have formed at <1 to ~8 km depth. Sulfide minerals in hydrothermal deposits are the primary economic source of metals used by society, which occur as major, minor and trace elements. Sulfides also play a key role during magmatic crystallization in concentrating metals that subsequently may (or may not) be supplied to hydrothermal fluids. Precipitation of sulfides that themselves may have little economic value, like pyrite, may trigger the deposition of more valuable metals (e.g. Au) by destabilizing the metal-bearing sulfur complexes. We review why, where and how sulfide minerals in hydrothermal systems precipitate.

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Magmatic Sulfide Ore Deposits

Magmatic sulfide ore deposits are products of natural smelting: concentration of immiscible sulfide liquid (‘matte’), enriched in chalcophile elements, derived from silicate magmas (‘slags’). Sulfide ore deposits occupy a spectrum from accumulated pools of matte within small igneous intrusions or lava flows, mined primarily for Ni and Cu, to stratiform layers of weakly disseminated sulfides within large mafic–ultramafic intrusions, mined for platinum-group elements. One of the world’s most valuable deposits, the Platreef in the Bushveld Complex (South Africa) has aspects of both of these end members. Natural matte compositions vary widely between and within deposits, and these compositions are controlled largely by the relative volumes of matte and slag that interact with one another.

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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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About v13n2, Sulfur or Sulphur?, Call for Proposals, Social Media

Elements magazine tries hard to be an internationally oriented and inclusive scientific publication. As such, Elements accepts texts written in American English or British English and it has been Elements’ policy to allow authors to choose between the American or British writing style and spelling. Our purpose in this is to pay respect to international differences and, as a result, help preserve these differences.

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