No abstract

A rare sodium carbonate nyerereite, (Na,K)2Ca(CO3)2, first found in unique natrocarbonatite lava of Oldoinyo Lengai volcano, also attracted a lot of attention as an inclusion phase in mantle minerals formed in the course of deep carbonatite magmatism. We measured the evolution of nyerereite Raman spectra under quasi‐hydrostatic compression up to 6.4 GPa using a diamond anvil cell. The ν4(CO32−) band (710 cm−1 at ambient pressure) and ν1(CO32−) doublet (1077 and 1086 cm−1 at ambient pressure) demonstrated a positive pressure shift with dν/dP irregularities at 0.5 and 3.0 GPa. The obtained calibration was then used for residual pressure measurements in nyerereite‐bearing inclusions in olivine from the Udachnaya‐East kimberlite. Copyright © 2017 John Wiley & Sons, Ltd.

CO2‐bearing fluid inclusions coexisting with diamonds were identified in zircons from diamondiferous gneiss in the Kokchetav Massif. This discovery provides evidence for the presence of CO2 in UHP fluids and diamond formation in moderately oxidized conditions in the Kokchetav gneiss. Fluid and multiphase solid inclusions coexisting in zircons represent immiscible melt and fluid captured close to the peak metamorphic conditions for the Kokchetav UHP gneiss. Most of CO2‐bearing inclusions are CO2+H2O mixtures except for some cases when they also contain daughter phases (e.g. muscovite, calcite and quartz) tracing the presence of aqueous and solute‐rich fluids at different phases of UHP metamorphism. Decrease of pressure and temperature may have been responsible for the reduction of solutes in the CO2‐bearing fluid. The lack of CO2‐bearing inclusions in garnet porphyroblasts from diamond‐bearing gneiss, as well as the common coexistence of aqueous CO2‐bearing inclusions with calcite, testify that most likely all CO2 in fluid was consumed by the calcite‐forming reaction and hydrous melt was the only remaining growth medium during retrograde metamorphism of the Kokchetav UHPM gneisses. Neither K‐cymrite nor kokchetavite was identified among daughter phases in the hydrous melt inclusions in garnet, which indicates that they hardly could originate in a metapelitic system. Copyright © 2017 John Wiley & Sons, Ltd.

Resistance of the porous glass‐based aggregates to alkali‐silicate reaction (ASR) was the focus of this study. ASR was studied in mixtures of aggregates with water alkali solutions simulating alkali media of row concrete. Granular foam glass with homogeneous glass in the pore walls is ASR‐active, which leads to the leaching of glass and to the formation of hydrated Na‐silicate gel, Ca‐silicate, and aluminosilicate on the aggregate surfaces. Mitigation of ASR‐activity in granular foam glass was achieved by thermo‐induced crystallization (850‐900ºC) of micro‐ and nanoscale crystals (Na4CaSi3O9 and/or Na2Ca3Si6O16) in the pore walls with the formation of granular glass‐ceramic foams. The main characterization methods were scanning electron microscopy, x‐ray powder diffraction analysis, x‐ray fluorescence, atomic emission spectrometry, and pH analysis.