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GSA Session: Metals for the Future: Geology of Critical and Basic Minerals for the Green Economy

SR
Simone Runyon
Wed, May 5, 2021 4:13 PM

Hello all!

Doug Kreiner, Zhaoshan Chang, Simone Runyon, and John Dilles are co-chairing a topical session at the annual GSA meeting October 10-13 in Portland, OR, titled “Metals for the Future: Geology of Critical and Basic Minerals for the Green Economy” (T34).

Description

Critical (e.g., Li, REE, Co, Te) and basic (Cu, Au, Ni) minerals are essential for efficient green energy technologies and transportation. Such metals ideally could be produced in an environmentally sustainable and equitable manner. In this session we invite academics and private sector earth scientists to present new research on the geologic, petrochemical, and geophysical properties of known deposits; advanced theory of formation that include crustal-scale earth evolution, tectonics and structure, and igneous-metamorphic-sedimentary and geofluids; advanced plans to produce metals economically; future outlooks for demand, supply, and development; and environmental considerations for the sustainable development of these necessary resources.

We encourage you, your colleagues, and students to submit relevant contributions to this session to continue the discussion of critical and base metals required to meet the future needs of our rapidly advancing society. Abstract submissions will open June 1st and close July 20th. The meeting website can be found here: https://community.geosociety.org/gsa2021/home.

Cheers!


Simone E. Runyon (she/her/hers)

Assistant Professor - Economic Geology

Department of Geology and Geophysics

University of Wyoming

Hello all! Doug Kreiner, Zhaoshan Chang, Simone Runyon, and John Dilles are co-chairing a topical session at the annual GSA meeting October 10-13 in Portland, OR, titled “Metals for the Future: Geology of Critical and Basic Minerals for the Green Economy” (T34). Description Critical (e.g., Li, REE, Co, Te) and basic (Cu, Au, Ni) minerals are essential for efficient green energy technologies and transportation. Such metals ideally could be produced in an environmentally sustainable and equitable manner. In this session we invite academics and private sector earth scientists to present new research on the geologic, petrochemical, and geophysical properties of known deposits; advanced theory of formation that include crustal-scale earth evolution, tectonics and structure, and igneous-metamorphic-sedimentary and geofluids; advanced plans to produce metals economically; future outlooks for demand, supply, and development; and environmental considerations for the sustainable development of these necessary resources. We encourage you, your colleagues, and students to submit relevant contributions to this session to continue the discussion of critical and base metals required to meet the future needs of our rapidly advancing society. Abstract submissions will open June 1st and close July 20th. The meeting website can be found here: https://community.geosociety.org/gsa2021/home. Cheers! ______________________________ Simone E. Runyon (she/her/hers) Assistant Professor - Economic Geology Department of Geology and Geophysics University of Wyoming
RR
Rachel Russell
Thu, May 6, 2021 4:00 PM

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 soon here (http://www.minsocam.org/MSA/Ammin/AM_NotableArticles.html).

The DOI links below will take you to the abstract on GeoScienceWorld (or perhaps DeGruyter).

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.
Sincerely,
Hongwu Xu
Don Baker

How to apply elastic geobarometry in geology
https://doi.org/10.2138/am-2021-7845
This paper by by Fabrizio Nestola highlights the new "EntraPT" web application, published by Mazzucchelli et al. (2021)https://doi.org/10.2138/am-2021-7693CCBYNCND in American Mineralogisthttps://doi.org/10.2138/am-2021-7693CCBYNCND, which provides all recent advances of elastic geobarometry within a single platform. This application allows the user to interpret the residual strain of anisotropic inclusions in an intuitive and consistent manner. At the same time, the platform provides the tools needednto perform calculations of the residual pressure and of the entrapment pressure and temperature of isotropic and anisotropic systems using a self-consistent set of thermoelastic properties.

Early Archean alteration minerals in mafic-ultramafic rocks of the Barberton greenstone belt as petrological analogs for clay mineralogy on Mars
https://doi.org/10.2138/am-2021-7656
The upcoming Mars2020 rover analyses of Jezero crater will investigate phyllosilicate and carbonate-bearing outcrops in delta sediments, as well as basaltic bedrock containing olivine, chlorite, and serpentine (e.g., Goudge et al. 2017, Bramble et al. 2017; Amador et al., Brown et al. 2020). If chlorite- and serpentine-bearing rocks are encountered by Mars2020, the rock textures and spectral analyses in this study by Grosch et al. will provide ground truth to understand potential formation conditions for those rocks.

Characterization of the metasomatizing agent in the upper mantle beneath the northern Pannonian Basin based on Raman imaging, FIB-SEM, and LA-ICP-MS analysis of silicate melt inclusions in spinel peridotite
https://doi.org/10.2138/am-2021-7292
This study by Liptai et al. presents a combination of analytical methods applicable to silicate melt inclusions as an alternative to microthermometry. The combined analyses allow the acquisition of both geochemical properties and 3D structure of the daughter phases. With the use of these methods, composition, origin and crystallization history of a trapped metasomatizing melt was revealed in the upper mantle of the northern part of the Pannonian Basin (Central Europe).

The potential for aqueous fluid-rock and silicate melt-rock interactions to re-equilibrate hydrogen in peridotite nominally anhydrous minerals
https://doi.org/10.2138/am-2021-7435
Hydrogen diffusion chronometry provides first-order constraints on how quickly mantle mineral water contents can be overprinted by hydrothermal alteration and melt-rock interactions. Peridotite xenoliths likely completely lose their mantle-inherited water contents prior to eruption due to fast H re-equilibration timescales. Re-equilibration occurs in as little as 10 minutes at 1000 °C to several of years at 600 °C, suggesting that both melt- and/or aqueous fluid-rock interactions can explain why many peridotites have water contents decoupled from trace elements and that are too high to reflect residues of melting. Lynn and Warren also posit in this contribution that hydrogen has the unique potential to be used at low-T (e.g., 300 °C) to investigate the timescales of serpentinization.

Oxygen isotope ratios in zircon and garnet: A record assimilation and fractional crystallization in the Dinkey Dome peraluminous granite, Sierra Nevada, California
https://doi.org/10.2138/am-2021-7472
Quintero et al. demonstrate that δ18O variations in zircon and garnet from the Dinkey Dome peraluminous granite in the Sierra Nevada, California, show how a peraluminous pluton is constructed from multiple batches of variably contaminated melts, suggesting that early-stage arc magmas sample crustal heterogeneities in small melt batches. Further progressive invigoration of the arc more effectively blends with mantle melts in source regions. Peraluminous magmas provide key details of the nascent arc and pre-batholithic crustal structure.

An evolutionary system of mineralogy, Part IV: Planetesimal differentiation and impact mineralization (4566 to 4560 Ma)
https://doi.org/10.2138/am-2021-7632
The evolutionary system of mineralogy attempts to classify minerals based on their historical context, considering when and how the minerals formed, in addition to the traditional approach of documenting major element chemistry and atomic structure. In Part IV of their series, Morrison and Hazen consider minerals formed in the partially molten interiors of asteroids that began to separate metal-rich cores from silicate-rich mantles, as well as minerals transformed by high-pressure impacts. The 130 new natural kinds of minerals considered here all formed within the solar system's first 10 million years -- a time when high pressure first became an important factor in the formation of minerals.

Constraints on deep, CO2-rich degassing at arc volcanoes from solubility experiments on hydrous basaltic andesite of Pavlof Volcano, Alaskan Peninsula, at 300 to 1200 MPa
https://doi.org/10.2138/am-2021-7531
Mafic magmas that enter Earth's crust from the mantle are commonly estimated to have appreciable CO2 concentrations, but direct experimental determinations are few of CO2 solubility at pressures appropriate for the continental lower crust and underlying uppermost mantle.  This study by Mangan et al. determines CO2 solubility in that pressure range for basaltic andesite, a widespread subduction zone magma type, across a range of dissolved H2O concentrations suitable for arc magmas.  Results show that basaltic andesite can retain substantial dissolved CO2 in the deep arc crust, consistent with geochemical estimates, but that published models of magmatic CO2 solubility are inaccurate for mid-crustal to uppermost mantle pressures, some overestimating and others underestimating the measured concentrations.  Systematic studies varying individual melt compositional components may be required to improve understanding of controls on solubility and to develop robust models of H2O-CO2 degassing in the deep arc crust.

Electrical conductivity of diaspore, δ-AlOOH and ε-FeOOH
https://doi.org/10.2138/am-2021-7605
This study by Wang and Yoshino addresses the measurement of the electrical conductivity of three hydrous minerals: diaspore, δ-AlOOH, and ε-FeOOH. Investigations on such phases became hot topics because of their wide pressure-temperature stability field (Sano et al. 2008; Nishi et al. 2017; Duan et al. 2018; Hu et al. 2016, 2017). Electrical conductivity measurement of these minerals is also useful to understand deep water cycle. This study could provide important insights on the electrical behaviors of hydrous minerals and water cycle in the Earth's interior. Three significant outcomes were obtained from this study. (1) Diaspore shows a negative pressure dependence on the conductivity because of the ineffectual change of the length of O1H bond with increasing pressure. (2) δ-AlOOH and ε-FeOOH have shorter H...O2 bonds and longer O1H bonds which can account for the relatively higher conductivity than diaspore. (3) ε-FeOOH indicates higher conductivity than δ-AlOOH, which might be caused by the contribution of a small polaron conduction. The result of this study could be applied to the trends of the conductivity-depth relation for various lithologies including hydrous minerals in subduction zones such as altered oceanic crust, hydrous peridotites, and subducted sediments.

A reassessment of the amphibole-plagioclase NaSi-CaAl exchange thermometer with applications to igneous and high-grade metamorphic rocks
https://doi.org/10.2138/am-2021-7400
The existing calibrations of amphibole-plagioclase and amphibole-only thermometers yield inaccurate temperature estimates. Three new expressions of the amphibole-plagioclase NaSi-CaAl exchange thermometer are calibrated in this work by Molina et al. that yield an overall similar precision (plus or minus 50°C), but are significantly more accurate. The new expressions can be used in a wide range of igneous and high-grade metamorphic rocks that bear subcalcic to calcic amphibole and oligoclase or more calcic plagioclase

Structural variations across the nepheline (NaAlSiO4)-kalsilite (KAlSiO4) series
https://doi.org/10.2138/am-2021-7484
Antao and Hovis obtained the crystal structure of 19 samples within the (Na,K)AlSiO4 series on a fine compositional scale. Well-defined structural variations occur across the Ne-Ks series. Natural samples are not yet available to give a complete understanding of Ne-Ks solid series, which is overcome by using "synthetic" ion-exchanged, powder samples instead of single crystals. Natural samples with limited solid solutions plot close to their "synthetic" samples, so their results apply to natural systems. However, it would be interesting to see how the results for other natural samples with different chemistries, if discovered, compare to the present results. Phase transitions in minerals and their reversibility continue to intrigue researchers. Synchrotron high-resolution powder X-ray diffraction uses a highly intense beam that is sensitive to fine-scale intergrowths or overlapping multi-phases with subtle change in symmetry that cannot be resolved with conventional powder X-ray diffraction. The P31c to P63 transition in kalsilite may be monitored using the 111 reflection that is clearly observable with HRPXRD. K-rich nepheline and kalsilite occur in volcanic rocks as high temperatures expand the aluminosilicate framework to accommodate large K atoms. Particularly, P63 Ks occurs in volcanic rocks, and low temperature P31c Ks occurs in metamorphic rocks. The high to low transition is not completely reversible.

The (chemical) potential for understanding overstepped garnet nucleation and growth
https://doi.org/10.2138/am-2021-7354
This paper by Nagurney et al. utilizes phase equilibria modeling to understand the energetic consequences of metamorphic minerals, specifically garnet, not forming at thermodynamic equilibrium. They compare the chemical potentials of garnet-forming oxide components (MnO, CaO, FeO, MgO, Al2O3) between two calculations: one in which Gibbs free energy is minimized and one in which the minimization proceeds under identical conditions but in the absence of garnet. This allows them to study the energetic differences between a garnet-bearing and a garnet-absent calculation. Their results highlight that immediately up temperature of garnet-in, differences in the chemical potentials between the two calculations are commonly minimal for some components. In all twelve examples used in this study the chemical potential of Al2O3 (mu-Al2O3) diverges between garnet-bearing and garnet-absent calculations at greater P-T conditions than that of MnO, CaO, FeO and MgO. This P-T point at which mu-Al2O3 diverges is a function of bulk-rock MnO content. Further, results emphasize that immediately up temperature of garnet-in the total volume of garnet in a rock is commonly calculated to be minimal. These results highlight the necessity for petrologists to interrogate phase equilibria modeling data when interpreting the amount of overstepping of the garnet-in reaction.

EntraPT: an online platform for elastic geothermobarometry
https://doi.org/10.2138/am-2021-7693CCBYNCND
During geodynamic processes minerals in rocks can recrystallize at depth in the Earth at high pressures and temperatures and new minerals form. During crystallization, growing minerals can trap other minerals within them as inclusions. After millions of years, some of these rocks are exposed on the Earth's surface and become available to researchers for direct observation. The inclusions deform during exhumation because of the removal of external pressure and temperature. By measuring the residual deformation in the inclusion and applying specific calculations it is possible to estimate the conditions (pressure and temperatures) of the recrystallization; the time when the inclusion was entrapped in its host. This in turn gives us a wealth of information to understand large scale geological processes such as the subduction and the collision of tectonic plates. In this Open Access paper, Mazzucchelli et al. present EntraPT, a new freely accessible online application that eases the interpretation of the residual deformation of inclusions and performs the calculations to estimate the entrapment conditions. EntraPT gives a standardized procedure to make it easier for researchers to check, store, and share their data.

Sodium nanoparticles in alkali halide minerals: Why is villiaumite red and halite blue?
https://doi.org/10.2138/am-2021-7917
Radiation damage in natural alkali halides causes alkali ions to form metallic nanoparticles that produce vivid bright colors. In this paper by Calas et al., the Lorentzian lineshape of the main absorption band characterizes a Surface Plasmon Resonance effect due to Na colloids, about 2.5-3 nm large. As the resonance wavelength depends on the refractive index of the mineral, the position of this band shifts between the two minerals. The resulting change of the transmission window causes a dramatic change of color from red villiaumite to blue halite. This approach may also help understand the purple color of irradiated fluorite, which also arises from the presence of metal colloids.

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 soon here (http://www.minsocam.org/MSA/Ammin/AM_NotableArticles.html). The DOI links below will take you to the abstract on GeoScienceWorld (or perhaps DeGruyter). 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 (here<http://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. Sincerely, Hongwu Xu Don Baker How to apply elastic geobarometry in geology https://doi.org/10.2138/am-2021-7845 This paper by by Fabrizio Nestola highlights the new "EntraPT" web application, published by Mazzucchelli et al. (2021)<https://doi.org/10.2138/am-2021-7693CCBYNCND> in American Mineralogist<https://doi.org/10.2138/am-2021-7693CCBYNCND>, which provides all recent advances of elastic geobarometry within a single platform. This application allows the user to interpret the residual strain of anisotropic inclusions in an intuitive and consistent manner. At the same time, the platform provides the tools needednto perform calculations of the residual pressure and of the entrapment pressure and temperature of isotropic and anisotropic systems using a self-consistent set of thermoelastic properties. Early Archean alteration minerals in mafic-ultramafic rocks of the Barberton greenstone belt as petrological analogs for clay mineralogy on Mars https://doi.org/10.2138/am-2021-7656 The upcoming Mars2020 rover analyses of Jezero crater will investigate phyllosilicate and carbonate-bearing outcrops in delta sediments, as well as basaltic bedrock containing olivine, chlorite, and serpentine (e.g., Goudge et al. 2017, Bramble et al. 2017; Amador et al., Brown et al. 2020). If chlorite- and serpentine-bearing rocks are encountered by Mars2020, the rock textures and spectral analyses in this study by Grosch et al. will provide ground truth to understand potential formation conditions for those rocks. Characterization of the metasomatizing agent in the upper mantle beneath the northern Pannonian Basin based on Raman imaging, FIB-SEM, and LA-ICP-MS analysis of silicate melt inclusions in spinel peridotite https://doi.org/10.2138/am-2021-7292 This study by Liptai et al. presents a combination of analytical methods applicable to silicate melt inclusions as an alternative to microthermometry. The combined analyses allow the acquisition of both geochemical properties and 3D structure of the daughter phases. With the use of these methods, composition, origin and crystallization history of a trapped metasomatizing melt was revealed in the upper mantle of the northern part of the Pannonian Basin (Central Europe). The potential for aqueous fluid-rock and silicate melt-rock interactions to re-equilibrate hydrogen in peridotite nominally anhydrous minerals https://doi.org/10.2138/am-2021-7435 Hydrogen diffusion chronometry provides first-order constraints on how quickly mantle mineral water contents can be overprinted by hydrothermal alteration and melt-rock interactions. Peridotite xenoliths likely completely lose their mantle-inherited water contents prior to eruption due to fast H re-equilibration timescales. Re-equilibration occurs in as little as 10 minutes at 1000 °C to several of years at 600 °C, suggesting that both melt- and/or aqueous fluid-rock interactions can explain why many peridotites have water contents decoupled from trace elements and that are too high to reflect residues of melting. Lynn and Warren also posit in this contribution that hydrogen has the unique potential to be used at low-T (e.g., 300 °C) to investigate the timescales of serpentinization. Oxygen isotope ratios in zircon and garnet: A record assimilation and fractional crystallization in the Dinkey Dome peraluminous granite, Sierra Nevada, California https://doi.org/10.2138/am-2021-7472 Quintero et al. demonstrate that δ18O variations in zircon and garnet from the Dinkey Dome peraluminous granite in the Sierra Nevada, California, show how a peraluminous pluton is constructed from multiple batches of variably contaminated melts, suggesting that early-stage arc magmas sample crustal heterogeneities in small melt batches. Further progressive invigoration of the arc more effectively blends with mantle melts in source regions. Peraluminous magmas provide key details of the nascent arc and pre-batholithic crustal structure. An evolutionary system of mineralogy, Part IV: Planetesimal differentiation and impact mineralization (4566 to 4560 Ma) https://doi.org/10.2138/am-2021-7632 The evolutionary system of mineralogy attempts to classify minerals based on their historical context, considering when and how the minerals formed, in addition to the traditional approach of documenting major element chemistry and atomic structure. In Part IV of their series, Morrison and Hazen consider minerals formed in the partially molten interiors of asteroids that began to separate metal-rich cores from silicate-rich mantles, as well as minerals transformed by high-pressure impacts. The 130 new natural kinds of minerals considered here all formed within the solar system's first 10 million years -- a time when high pressure first became an important factor in the formation of minerals. Constraints on deep, CO2-rich degassing at arc volcanoes from solubility experiments on hydrous basaltic andesite of Pavlof Volcano, Alaskan Peninsula, at 300 to 1200 MPa https://doi.org/10.2138/am-2021-7531 Mafic magmas that enter Earth's crust from the mantle are commonly estimated to have appreciable CO2 concentrations, but direct experimental determinations are few of CO2 solubility at pressures appropriate for the continental lower crust and underlying uppermost mantle. This study by Mangan et al. determines CO2 solubility in that pressure range for basaltic andesite, a widespread subduction zone magma type, across a range of dissolved H2O concentrations suitable for arc magmas. Results show that basaltic andesite can retain substantial dissolved CO2 in the deep arc crust, consistent with geochemical estimates, but that published models of magmatic CO2 solubility are inaccurate for mid-crustal to uppermost mantle pressures, some overestimating and others underestimating the measured concentrations. Systematic studies varying individual melt compositional components may be required to improve understanding of controls on solubility and to develop robust models of H2O-CO2 degassing in the deep arc crust. Electrical conductivity of diaspore, δ-AlOOH and ε-FeOOH https://doi.org/10.2138/am-2021-7605 This study by Wang and Yoshino addresses the measurement of the electrical conductivity of three hydrous minerals: diaspore, δ-AlOOH, and ε-FeOOH. Investigations on such phases became hot topics because of their wide pressure-temperature stability field (Sano et al. 2008; Nishi et al. 2017; Duan et al. 2018; Hu et al. 2016, 2017). Electrical conductivity measurement of these minerals is also useful to understand deep water cycle. This study could provide important insights on the electrical behaviors of hydrous minerals and water cycle in the Earth's interior. Three significant outcomes were obtained from this study. (1) Diaspore shows a negative pressure dependence on the conductivity because of the ineffectual change of the length of O1H bond with increasing pressure. (2) δ-AlOOH and ε-FeOOH have shorter H...O2 bonds and longer O1H bonds which can account for the relatively higher conductivity than diaspore. (3) ε-FeOOH indicates higher conductivity than δ-AlOOH, which might be caused by the contribution of a small polaron conduction. The result of this study could be applied to the trends of the conductivity-depth relation for various lithologies including hydrous minerals in subduction zones such as altered oceanic crust, hydrous peridotites, and subducted sediments. A reassessment of the amphibole-plagioclase NaSi-CaAl exchange thermometer with applications to igneous and high-grade metamorphic rocks https://doi.org/10.2138/am-2021-7400 The existing calibrations of amphibole-plagioclase and amphibole-only thermometers yield inaccurate temperature estimates. Three new expressions of the amphibole-plagioclase NaSi-CaAl exchange thermometer are calibrated in this work by Molina et al. that yield an overall similar precision (plus or minus 50°C), but are significantly more accurate. The new expressions can be used in a wide range of igneous and high-grade metamorphic rocks that bear subcalcic to calcic amphibole and oligoclase or more calcic plagioclase Structural variations across the nepheline (NaAlSiO4)-kalsilite (KAlSiO4) series https://doi.org/10.2138/am-2021-7484 Antao and Hovis obtained the crystal structure of 19 samples within the (Na,K)AlSiO4 series on a fine compositional scale. Well-defined structural variations occur across the Ne-Ks series. Natural samples are not yet available to give a complete understanding of Ne-Ks solid series, which is overcome by using "synthetic" ion-exchanged, powder samples instead of single crystals. Natural samples with limited solid solutions plot close to their "synthetic" samples, so their results apply to natural systems. However, it would be interesting to see how the results for other natural samples with different chemistries, if discovered, compare to the present results. Phase transitions in minerals and their reversibility continue to intrigue researchers. Synchrotron high-resolution powder X-ray diffraction uses a highly intense beam that is sensitive to fine-scale intergrowths or overlapping multi-phases with subtle change in symmetry that cannot be resolved with conventional powder X-ray diffraction. The P31c to P63 transition in kalsilite may be monitored using the 111 reflection that is clearly observable with HRPXRD. K-rich nepheline and kalsilite occur in volcanic rocks as high temperatures expand the aluminosilicate framework to accommodate large K atoms. Particularly, P63 Ks occurs in volcanic rocks, and low temperature P31c Ks occurs in metamorphic rocks. The high to low transition is not completely reversible. The (chemical) potential for understanding overstepped garnet nucleation and growth https://doi.org/10.2138/am-2021-7354 This paper by Nagurney et al. utilizes phase equilibria modeling to understand the energetic consequences of metamorphic minerals, specifically garnet, not forming at thermodynamic equilibrium. They compare the chemical potentials of garnet-forming oxide components (MnO, CaO, FeO, MgO, Al2O3) between two calculations: one in which Gibbs free energy is minimized and one in which the minimization proceeds under identical conditions but in the absence of garnet. This allows them to study the energetic differences between a garnet-bearing and a garnet-absent calculation. Their results highlight that immediately up temperature of garnet-in, differences in the chemical potentials between the two calculations are commonly minimal for some components. In all twelve examples used in this study the chemical potential of Al2O3 (mu-Al2O3) diverges between garnet-bearing and garnet-absent calculations at greater P-T conditions than that of MnO, CaO, FeO and MgO. This P-T point at which mu-Al2O3 diverges is a function of bulk-rock MnO content. Further, results emphasize that immediately up temperature of garnet-in the total volume of garnet in a rock is commonly calculated to be minimal. These results highlight the necessity for petrologists to interrogate phase equilibria modeling data when interpreting the amount of overstepping of the garnet-in reaction. EntraPT: an online platform for elastic geothermobarometry https://doi.org/10.2138/am-2021-7693CCBYNCND During geodynamic processes minerals in rocks can recrystallize at depth in the Earth at high pressures and temperatures and new minerals form. During crystallization, growing minerals can trap other minerals within them as inclusions. After millions of years, some of these rocks are exposed on the Earth's surface and become available to researchers for direct observation. The inclusions deform during exhumation because of the removal of external pressure and temperature. By measuring the residual deformation in the inclusion and applying specific calculations it is possible to estimate the conditions (pressure and temperatures) of the recrystallization; the time when the inclusion was entrapped in its host. This in turn gives us a wealth of information to understand large scale geological processes such as the subduction and the collision of tectonic plates. In this Open Access paper, Mazzucchelli et al. present EntraPT, a new freely accessible online application that eases the interpretation of the residual deformation of inclusions and performs the calculations to estimate the entrapment conditions. EntraPT gives a standardized procedure to make it easier for researchers to check, store, and share their data. Sodium nanoparticles in alkali halide minerals: Why is villiaumite red and halite blue? https://doi.org/10.2138/am-2021-7917 Radiation damage in natural alkali halides causes alkali ions to form metallic nanoparticles that produce vivid bright colors. In this paper by Calas et al., the Lorentzian lineshape of the main absorption band characterizes a Surface Plasmon Resonance effect due to Na colloids, about 2.5-3 nm large. As the resonance wavelength depends on the refractive index of the mineral, the position of this band shifts between the two minerals. The resulting change of the transmission window causes a dramatic change of color from red villiaumite to blue halite. This approach may also help understand the purple color of irradiated fluorite, which also arises from the presence of metal colloids.