We seek applicants for the open ranked position, Chair in Economic Geology, who would lead a research program in Mineral Deposit studies and related fields, as well as teach and mentor students (at the BSc, MSc and PhD levels). The chair receives a generous start-up fund from the university and an annual research grant from an Industry-endowed fund.
The advertisement is attached and can be found under Faculty of Science, Department of Earth and Environmental Sciences, at the University of Ottawa web site:
Department of Earth and Environmental Sciences
Advanced Research Complex,
University of Ottawa Ottawa,
Ontario, K1N 6N5, Canada
Dear American Mineralogist Readers,
Below are the Paper Highlights for this month’s issue of the American Mineralogist: International Journal of Earth and Planetary Materials. You may also view the American Mineralogist Paper Highlights list at here (http://www.minsocam.org/MSA/Ammin/AM_NotableArticles.html).
The DOI links below will take you to the abstract on GeoScienceWorld.
If you have “IP” access via your institution’s library, it should reveal the whole paper. Consult your institution’s IT department or friendly librarian.
If you have MSA membership, then authenticate in from the American Mineralogist menu (herehttp://www.msapubs.org/ directly). Once at the portal page, click the right-side American Mineralogist link, enter your user name (e-mail address), and your password (membership number). Then search via your browser’s search tools for the paper you want to read. (On Rachel’s computer, it is control-f but we think that is little different for everyone.)
Note that on GSW you can sign up for a table of contents to be sent you when the issue is live -- this is a feature open to anyone who registers on the site.
Thank you for reading American Mineralogist.
Gamma-enhancement of reflected light images: A rapid, effective tool for assessment of compositional heterogeneity in pyrite
Zhu et al. developed a gamma correction method to display impurity-induced reflectance variation of pyrite at grain scale. This method enhances optical digital signal differences obtained under reflected light using an optical microscope. Incorporation of As in pyrite reduces the total number of electrons that could be excited to produce reflected light, resulting in decrease of reflectance. Gamma correction is a rapid, effective tool for the assessment of compositional heterogeneity in pyrite and other ore minerals with negligible bireflectance. Gamma-enhanced images may help constrain links between textures and compositions of minerals prior to subsequent quantitative analyses.
Thermal metamorphic history of Antarctic CV3 and CO3 chondrites inferred from the first- and second-order Raman peaks of polyaromatic organic carbon.
Yesiltas et al. determined the first- and second-order carbon Raman peak parameters in an effort to infer asteroidal thermal metamorphic history. The second-order carbon peaks are quantitatively studied for the first time, which contain information that the first-order peaks don't. Peak metamorphic temperatures of the investigated meteorites have been estimated based on the width of the D band as well as the calculated Raman spectral curvature.
A quantitative description of fission-track etching in apatite
Aslanian et al. propose a quantitative model of fission-track etching in apatite and use it for calculating the shapes and dimensions of etched tracks in different faces. Their model replaces an earlier model and invalidates certain restrictive dating practices based on it. This can have a profound effect on fission-track dating. Their measurements show that the length of confined tracks increases with etch time at a decreasing average rate that differs from the track-etch rate as well as from that of undamaged apatite. Step-etch experiments are shown to be useful for reducing or eliminating procedure-related effects from the track-length data and so for accessing more fundamental track properties resulting from formation and annealing.
Spectroscopic analysis of allophane and imogolite samples with variable Fe abundance for characterizing the poorly crystalline components on Mars
Poorly crystalline nanophase minerals that occur as weathering products on Mars contain critical information about the evolution of the early martian climate. Jeute et al. present compositional, structural, and spectroscopic data on a set of synthetic Mars analog nanophase aluminosilicates, including imogolite and allophanes with varying Al-Si ratios. They show that changes in the Al-Si ratio can be remotely detected, and that this measurement will help evaluate current models for the climatic evolution of Mars.
The relationship between 207Pb NMR chemical shift and the morphology and crystal structure for the apatites Pb5(AO4)3Cl, vanadinite (A = V), pyromorphite (A = P), and mimetite (A = As)
NMR spectroscopy of single crystals is the method of choice to precisely determine the full tensors of NMR interaction parameters via orientation-dependent measurements. Zeman et al. conducted a series of single-crystal NMR experiments on natural minerals, in particular on lead-bearing compounds, with the aim to extract the chemical shift tensor of 207Pb in high precision. Going beyond mere tensor determination, they noted that within the mineral family of vanadinite, pyromorphite, and mimetite, the NMR chemical shift may be related to some structural parameters such as unit-cell volume. From evaluating the number of the NMR resonances and their respective line widths, information about the mosaicity of these minerals could be derived.
Effect of cationic substitution on the pressure-induced phase transitions in calcium carbonate
Martirosyan et al. studied a member of the (Ca,Sr)CO3 solid solution series using in situ Raman spectroscopy at pressures up to 55 GPa and temperatures up to 1273 K. They observed crystallization of the CaCO3-II-type structure at 1273 K and 2 GPa. A new high-pressure modification, Sr-calcite-IIIc, was detected at 7-14 GPa. Thus, substitution of Ca2+ with Sr2+ promotes the formation of structures with larger cation coordination numbers such as aragonite, CaCO3-VII, and post-aragonite at lower P-T conditions compared to pure CaCO3.
Immiscible-melt inclusions in corundum megacrysts: Microanalyses and geological implications
Xu et al. identified two types of inclusions in the corundum megacrysts from Changle, China. Type I inclusion consists of a dark part (DP) and a bright part (BP), which were formed due to liquid immiscibility at ~1200 °C; the former is composed of quartz, corundum, and amorphous substance-1, and the latter is composed of baddeleyite and amorphous substance-2. Type II inclusion is composed of zircon, quartz, and amorphous substance-3. The novel inclusions, together with other previously found mineral inclusions in Changle corundum, demonstrate that both the alkaline felsic melt and carbonatitic melt existed, and they derived from metasomatized mantle. The ages of zircon inclusions show that the corundum megacrysts crystallized from syenitic-type differentiated of earlier underplated basalts at the crust-mantle boundary and were brought up by later episodic basalt eruptions.
Water quantification in olivine and wadsleyite by Raman spectroscopy and study of errors and uncertainties
Martinek and Balfan-Casanova demonstrate that Raman spectroscopy allows the study of water quantification in different phases of fine polymineralic samples of complex composition, with a wide range of measurable water contents. The water contents of olivine and wadsleyite can be measured using this method with a simple sample preparation. Despite being around 25%, the uncertainties on water concentration are sufficiently low to infer the presence of dehydration that was induced by melting or other geologic processes.
High-pressure and high-temperature vibrational properties and anharmonicity of carbonate minerals up to 6 GPa and 500 °C by Raman spectroscopy
Carbonate minerals play a dominant role in the deep carbon cycle. Farsang et al. measured the high-pressure and high-temperature vibrational properties of all aragonite-group and calcite-group carbonate minerals up to 6 GPa and 500 °C by Raman spectroscopy in order to understand their anharmonicity under crustal and upper mantle conditions.
Vanadium-induced coloration in grossite (CaAl4O7) and hibonite (CaAl12O19)
Ardit et al. studied the unusual coloration in hibonite (purple) and grossite (light violet) crystals, caused by high concentrations of vanadium. Characterization of these specimens by means of single-crystal X-ray diffraction and absorption spectroscopy (aided by EMPA chemical analyses) provides information of both long- and short-range characteristics of their crystal structures.
Incorporation mechanism of tungsten in W-Fe-Cr-V-bearing rutile
Majzlan et al. examined the position of tungsten in the structures of two common minerals, rutile and hematite. It is of interest because these and related minerals serve as vehicles that enrich the sediments in the element tungsten. These sediments can be later melted and transformed into fertile magmas that form ore deposits. Tungsten was found to enter the structure of rutile, but in hematite, there exist nanoinclusions of iron-tungsten oxide intergrown with the host mineral. Rutile is a better vehicle for tungsten; hematite can serve as such under specific moderately reducing conditions.
Titanium diffusion profiles and melt inclusion chemistry and morphology in quartz from the Tshirege Member of the Bandelier Tuff
Boro et al. describe that melt Inclusions in quartz from the chemically zoned Tshirege Member of the Bandelier Tuff record the compositional evolution of a caldera-forming magma chamber. Variable melt inclusion faceting suggests timescales of millennia for crystal mush generation and crystal storage. Titanium concentration zoning in quartz suggests shorter timescales of decades to centuries for recharge and mobilization of said mush to produce an eruptible, zoned magma body.
Vasilseverginite, Cu9O4(AsO4)2(SO4)2, a new fumarolic mineral with a hybrid structure containing novel anion-centered tetrahedral structural units
Pekov et al. describe the unique structure of a new mineral, vasilseverginite Cu9O4(AsO4)2(SO4)2, which can be considered as a hybrid of the structures of popovite Cu5O2(AsO4)2 and dolerophanite Cu2O(SO4). The concept of hybridization of mineral species developed in this study may give new ideas for the preparation of novel structural architectures on the border of stability fields of chemically and structurally simpler compounds. The discovery of vasilseverginite indicates the existence of polynuclear oxocentered copper clusters in a gaseous phase, which may be a form of transport of Cu by volcanic gases.
Priscillagrewite-(Y), (Ca2Y)Zr2Al3O12: A new garnet of the bitikleite group from the Daba-Siwaqa area, the Hatrurim Complex, Jordan
Galuskina et al. report the discovery of a new garnet, priscillagreowte-(Y), belonging to the bitikleite group of the garnet supergroup. The mineral was found in apatite-bearing varicolored spurrite marble in the Daba-Siwaqa area, central Jordan. Priscillagrewite-(Y) is interpreted to be a relic of the high-temperature association formed in the progressive stage of the peak pyrometamorphism conditions, when the temperature could have reached close to 1000 °C. The authors suggest that there is a reasonable chance of finding priscillagrewite-(Y) in ultrarefractory calcium-aluminum-rich inclusions from chondrites, then it can be the third garnet species originating in the solar nebula.
Stoefflerite, (Ca,Na)(Si,Al)4O8 in the hollandite structure: A new high-pressure polymorph of anorthite from martian meteorite NWA 856
Stoefflerite is the high-pressure polymorph of anorthite. Tschauner et al. show that in Earth's transition zone, it is a component of the important carrier of K, liebermannite. In shock-metamorphic environments, it marks high-pressures at temperatures above the Hugoniot but below formation of stable phases.
Recycled volatiles determine fertility of porphyry deposits in collisional settings
There have long been debates about whether copper and gold come from the mantle or crust. Previous hypotheses dominantly relied on the metal concentration, which is lower in both Earth's mantle and crust. The volatile elements Cl and S are the most important factors controlling the transport of ore metals in magma; therefore, their source and evolution can be a key to understanding the genesis of Cu-Au deposits. Xu et al. show that geochemical and Rb-Sr isotopic data on apatite from 12 porphyry systems across Iran, Tibet, and western China, can distinguish fertile magmas from barren magmatic suites and indicate the importance of volatiles, recycled from previous oceanic subduction, in collisional settings. This study is of importance to the Earth's volatile evolution and economic geologists.
Nitrogen diffusion in silicate melts under reducing conditions
Nitrogen and argon are the two most abundant elements in the current atmosphere, but the elemental composition of Earth's interior and surficial reservoirs may have evolved over time. In this study, Boulliung et al. provide the first constraints on nitrogen diffusion in natural-like silicate melt with implications on N/Ar fractionation during reducing magmatic events, such as Earth's magma ocean stage. The result implies a N/Ar fractionation during reducing magmatic events, such as Earth's magma ocean stage.