Journal: The American Mineralogist

Abbreviation

Am. Mineral.

Publisher

Mineralogical Society of America

Journal Volumes

ISSN

0003-004X
1945-3027

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Publications 1 - 10 of 65
  • Heavy halogen geochemistry of martian shergottite meteorites and implications for the halogen composition of the depleted shergottite mantle source
    Item type: Journal Article
    Clay, Patricia; Joy, Katherine H.; O'Driscoll, Brian; et al. (2020)
    The American Mineralogist
  • Piston-cylinder experiments on H2O undersaturated Fe-bearing systems
    Item type: Journal Article
    Kägi, Ralf; Müntener, Othmar; Ulmer, Peter; et al. (2005)
    The American Mineralogist
  • Amorphous materials: Properties, structure, and durability
    Item type: Journal Article
    Malfait, Wim J. (2014)
    The American Mineralogist
  • The physical and chemical evolution of magmatic fluids in near-solidus silicic magma reservoirs: Implications for the formation of pegmatites
    Item type: Journal Article
    Troch, Juliana; Huber, Christian; Bachmann, Olivier (2022)
    The American Mineralogist
    As ascending magmas undergo cooling and crystallization, water and fluid-mobile elements (e.g., Li, B, C, F, S, Cl) become increasingly enriched in the residual melt until fluid saturation is reached. The consequential exsolution of a fluid phase dominated by H2O (magmatic volatile phase or MVP) is predicted to occur early in the evolution of long-lived crystal-rich "mushy" magma reservoirs and can be simulated by tracking the chemical and physical evolution of these reservoirs in thermomechanical numerical models. Pegmatites are commonly interpreted as the products of crystallization of late-stage volatile-rich liquids sourced from granitic igneous bodies. However, little is known about the timing and mechanism of extraction of pegmatitic liquids from their source. In this study, we review findings from thermomechanical models on the physical and chemical evolution of melt and MVP in near-solidus magma reservoirs and apply these to textural and chemical observations from pegmatites. As an example, we use a three-phase compaction model of a section of a mushy reservoir and couple this to fluid-melt and mineral-melt partition coeficients of volatile trace elements (Li, Cl, S, F, B). We track various physical parameters of melt, crystals, and MVP, such as volume fractions, densities, velocities, as well as the content in the volatile trace elements mentioned above. The results suggest that typical pegmatite-like compositions (i.e., enriched in incompatible elements) require high crystallinities (>70-75 vol% crystals) in the magma reservoir, at which MVP is eficiently trapped in the crystal network. Fluid-mobile trace elements can become enriched beyond contents expected from closed-system equilibrium crystallization by transport of MVP from more-evolved mush domains. From a thermomechanical perspective, these observations indicate that, rather than from melt, pegmatites may more likely be generated from pressurized, solute-rich MVP with high concentrations of dissolved silicate melt and fluid-mobile elements. Hydraulic fracturing provides a mechanism for the extraction and emplacement of such pegmatite- generating liquids in and around the main parental near-solidus mush as pockets, dikes, and small intrusive bodies. This thermomechanical framework for the extraction of MVP from mushes and associated formation of pegmatites integrates both igneous and hydrothermal realms into the concept of transcrustal magmatic distillation columns.
  • In situ determination of the compressibility of synthetic pure zircon (ZrSiO(4)) and the onset of the zircon-reidite phase transition
    Item type: Journal Article
    Van Westrenen, Wim; Frank, Mark R.; Hanchar, John M.; et al. (2004)
    The American Mineralogist
  • An evaluation of synthetic fluid inclusions for the purpose of trapping equilibrated, coexisting, immiscible fluid phases at magmatic conditions
    Item type: Journal Article
    Simon, Adam C.; Frank, Mark R.; Pettke, Thomas; et al. (2007)
    The American Mineralogist
  • The reaction talc + forsterite = enstatite + H2O revisited
    Item type: Journal Article
    Melekhova, Elena; Schmidt, Max W.; Ulmer, Peter; et al. (2006)
    The American Mineralogist
  • Atomic-scale characterization of commensurate and incommensurate vacancy superstructures in natural pyrrhotites
    Item type: Journal Article
    Jin, Lei; Koulialias, Dimitrios; Schnedler, Michael; et al. (2021)
    The American Mineralogist
    Pyrrhotites, characterized by the chemical formula Fe$_{1-δ}$S (0 < δ $\leq$ 1/8), represent an extended group of minerals that are derived from the NiAs-type FeS aristotype. They contain layered arrangements of ordered Fe vacancies, which are at the origin of the various magnetic signals registered from certain natural rocks and can act as efficient electrocatalysts in oxygen evolution reactions in ultrathin form. Despite extensive studies over the past century, the local structural details of pyrrhotite superstructures formed by different arrangements of Fe vacancies remain unclear, in particular at the atomic scale. Here, atomic-resolution high-angle annular dark-field imaging and nanobeam electron diffraction in the scanning transmission electron microscope are used to study natural pyrrhotite samples that contain commensurate 4C and incommensurate 4.91 $\pm$ 0.02C constituents. Local measurements of both the intensities and the picometer-scale shifts of individual Fe atomic columns are shown to be consistent with a model for the structure of 4C pyrrhotite, which was derived using X-ray diffraction by Tokonami et al. (1972). In 4.91 $\pm$ 0.02C pyrrhotite, 5C-like unequally sized nano-regions are found to join at anti-phase-like boundaries, leading to the incommensurability observed in the present pyrrhotite sample. This conclusion is supported by computer simulations. The local magnetic properties of each phase are inferred from the measurements. A discussion of perspectives for the quantitative counting of Fe vacancies at the atomic scale is presented.
  • Relationships between SEM-cathodoluminescence response and trace-element composition of hydrothermal vein quartz
    Item type: Journal Article
    Landtwing, Marianne R.; Pettke, Thomas (2005)
    The American Mineralogist
  • A XANES study of Cu speciation in high-temperature brines using synthetic fluid inclusions
    Item type: Journal Article
    Berry, Andrew J.; Hack, Alistair C.; Mavrogenes, John A.; et al. (2006)
    The American Mineralogist
Publications 1 - 10 of 65