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In this paper, we discuss the occurrence of liebermannite (IMA 2013-128), KAlSi3O8, a new, shock-generated, high-pressure tetragonal hollandite-type structure silicate mineral, in the Zagami basaltic shergottite meteorite. Liebermannite crystallizes in space group I4/m with Z = 2, cell dimensions of a = 9.15 ± 0.14 (1σ) Å, c = 2.74 ± 0.13 Å, and a cell volume of 229 ± 19 Å3 (for the type material), as revealed by synchrotron diffraction. In Zagami, liebermannite likely formed via solid-state transformation of primary igneous K-feldspar during an impact event that achieved pressures of ~20 GPa or more. The mineral name is in honor of Robert C. Liebermann, a high-pressure mineral physicist at Stony Brook University, New York, USA.

Within the Ca-Al-silicate system, dense, layered hexagonal phases occur at high temperatures and pressures between 20 and 23 GPa. They have been observed both in nature and in experiments. In this study, we describe the endmember with a dominant sixfold coordinated Si as a mineral zagamiite (IMA 2015-022a). This new mineral identified in Martian meteorites has a general formula of (Ca,Na)(Al,Fe,Mg)2(Si,Al,□)4O11, thus defining CaAl2Si3.5O11 as a previously unknown endmember of the hexagonal CAS phases. Zagamiite assumes space group P63/mmc with a unit cell of a = 5.403(2) Å, c = 12.77(3) Å, V = 322.9(11) Å3, and Z = 2. Zagamiite contains significant Fe and Mg and a substantial deficit of Na relative to plagioclase of an equivalent Al/Si, suggesting that it was formed through crystallization from a melt that was derived from a plagioclase-dominant mixture of plagioclase and clinopyroxene above the solidus beyond 20 GPa. [ABSTRACT FROM AUTHOR]

In Figure 6, we compare Mg#s (where Mg# = Mg/[Fe SP 2+ sp +Mg], atomic) of bulk olivine-phyric shergottites to the most Mg-rich olivine phenocrysts. Keywords: Olivine-phyric shergottites; Fe2+-Mg partitioning; olivine; basalt; Mars EN Olivine-phyric shergottites Fe2+-Mg partitioning olivine basalt Mars 1442 1452 11 07/05/22 20220701 NES 220701 Introduction The partitioning of elements between solid and liquid phases is an important tool for understanding and modeling igneous processes. Measuring Fe SP 3+ sp /Fe SP 2+ sp in silicate liquids is difficult; as a result, Fe SP 3+ sp /Fe SP 2+ sp of a melt it is often assumed to be negligible (e.g., [27]) or calculated using prior experimental calibrations (e.g., [79]; [52]). To ensure olivine saturation at the liquidus, we added ~17% synthetic olivine (enough to ensure olivine saturation but still dominated by liquid to facilitate rapid equilibration) with an Mg# of 77 (the estimated Mg# of olivine in the primitive martian mantle; [27]). [Extracted from the article]

Paqueite (Ca3TiSi2[Al,Ti,Si]3O14; IMA 2013‐053) and burnettite (CaVAlSiO6; IMA 2013‐054) are new refractory minerals, occurring as euhedral to subhedral crystals within aluminous melilite in A‐WP1, a type A Ca‐Al‐rich inclusion, and CGft‐12, a compact type A (CTA) from the Allende CV3 carbonaceous chondrite. Type paqueite from A‐WP1 has an empirical formula of (Ca2.91Na0.11)Ti4+Si2(Al1.64Ti4+0.90Si0.24V3+0.12Sc0.07Mg0.03)O14, with a trigonal structure in space group P321 and cell parameters a = 7.943 Å, c = 4.930 Å, V = 269.37 Å3, and Z = 1. Paqueite's general formula is Ca3TiSi2(Al,Ti,Si)3O14 and the endmember formula is Ca3TiSi2(Al2Ti)O14. Type burnettite from CGft‐12 has an empirical formula of Ca1.01(V3+0.56Al0.25Mg0.18)(Si1.19Al0.81)O6. It assumes a diopside‐type C2/c structure with a = 9.80 Å, b = 8.85 Å, c = 5.36 Å, β = 105.6°, V = 447.7 Å3, and Z = 4. Burnettite's general formula is Ca(V,Al,Mg)AlSiO6 and the endmember formula is CaVAlSiO6. Paqueite and burnettite likely originated as condensates, but the observed grains may have crystallized from local V‐rich melts produced during a later thermal event. For CGft‐12, the compositions of paqueite, clinopyroxene, and perovskite suggest that type As drew from two distinct populations of grains. Hibonite grains drew from multiple populations, but these were well mixed and not equilibrated prior to incorporation into type A host melilite. [ABSTRACT FROM AUTHOR]

Paqueite (Ca3TiSi2[Al,Ti,Si]3O14; IMA 2013‐053) and burnettite (CaVAlSiO6; IMA 2013‐054) are new refractory minerals, occurring as euhedral to subhedral crystals within aluminous melilite in A‐WP1, a type A Ca‐Al‐rich inclusion, and CGft‐12, a compact type A (CTA) from the Allende CV3 carbonaceous chondrite. Type paqueite from A‐WP1 has an empirical formula of (Ca2.91Na0.11)Ti4+Si2(Al1.64Ti4+0.90Si0.24V3+0.12Sc0.07Mg0.03)O14, with a trigonal structure in space group P321 and cell parameters a = 7.943 Å, c = 4.930 Å, V = 269.37 Å3, and Z = 1. Paqueite's general formula is Ca3TiSi2(Al,Ti,Si)3O14 and the endmember formula is Ca3TiSi2(Al2Ti)O14. Type burnettite from CGft‐12 has an empirical formula of Ca1.01(V3+0.56Al0.25Mg0.18)(Si1.19Al0.81)O6. It assumes a diopside‐type C2/c structure with a = 9.80 Å, b = 8.85 Å, c = 5.36 Å, β = 105.6°, V = 447.7 Å3, and Z = 4. Burnettite's general formula is Ca(V,Al,Mg)AlSiO6 and the endmember formula is CaVAlSiO6. Paqueite and burnettite likely originated as condensates, but the observed grains may have crystallized from local V‐rich melts produced during a later thermal event. For CGft‐12, the compositions of paqueite, clinopyroxene, and perovskite suggest that type As drew from two distinct populations of grains. Hibonite grains drew from multiple populations, but these were well mixed and not equilibrated prior to incorporation into type A host melilite. [ABSTRACT FROM AUTHOR]

Palladium oxide equilibration may be used to determine the the equilibrium thermodynamic properties of MgAl2O4 spinel. Researchers measured the energy of formation from magnesium and aluminum oxides at a range of -31jK/mol at 1150 degrees C to -39 kJ/mol at 1400 degrees C. These values agreed well with measures of disorder performed in other laboratory conditions. The equilibration method provided corrected calorimetric heat constants, and allowed for a new expression of heat capacity at constant pressure.

Kaitianite, Ti3+2Ti4+O5, is a new titanium oxide mineral discovered in the Allende CV3 carbonaceous chondrite. The type grain coexists with tistarite (Ti2O3) and rutile. Corundum, xifengite, mullite, osbornite, and a new Ti,Al,Zr‐oxide mineral are also present, although not in contact. The chemical composition of type kaitianite is (wt%) Ti2O3 56.55, TiO2 39.29, Al2O3 1.18, MgO 1.39, FeO 0.59, V2O3 0.08 (sum 99.07), yielding an empirical formula of (Ti3+1.75Al0.05Ti4+0.10Mg0.08Fe0.02)(Ti4+1.00)O5, with Ti3+ and Ti4+ partitioned, assuming a stoichiometry of three cations and five oxygen anions pfu. The end‐member formula is Ti3+2Ti4+O5. Kaitianite is the natural form of γ‐Ti3O5 with space group C2/c and cell parameters a = 10.115 Å, b = 5.074 Å, c = 7.182 Å, β = 112°, V = 341.77 Å3, and Z = 4. Both the type kaitianite and associated rutile likely formed as oxidation products of tistarite at temperatures below 1200 K, but this oxidation event could have been in a very reducing environment, even more reducing than a gas of solar composition. Based on experimental data on the solubility of Ti3+ in equilibrium with corundum from the literature, the absence of tistarite in or on Ti3+‐rich corundum (0.27–1.45 mol% Ti2O3) suggests that these grains formed at higher temperatures than the kaitianite (>1579–1696 K, depending on the Ti concentration). The absence of rutile or kaitianite in or on corundum suggests that any exposure to the oxidizing environment producing kaitianite in tistarite was too short to cause the precipitation of Ti‐oxides in or on associated corundum. [ABSTRACT FROM AUTHOR]

Chenmingite (FeCr2O4; IMA 2017-036) is a high-pressure mineral, occurring as micrometer- to submicrometer-sized lamellae within precursor chromite grains along with xieite and Fe,Cr-rich ulvöspinel next to shock-induced melt pockets, from the Tissint martian meteorite. The composition of type chenmingite by electron probe analysis shows an empirical formula of ( Fe 0.75 2 + Mg 0.23 Mn 0.02 ) $\left(\text{Fe}_{0.75}^{2+}\text{M}{{\text{g}}_{0.23}}\text{M}{{\text{n}}_{0.02}} \right)$ ( Cr 1.60 Al 0.29 Fe 0.06 3 + Fe 0.04 2 + Ti 0.02 ) Σ 2.01 O 4. ${{\left(\text{C}{{\text{r}}_{1.60}}\text{A}{{\text{l}}_{0.29}}\text{Fe}_{0.06}^{3+}\text{Fe}_{0.04}^{2+}\text{T}{{\text{i}}_{0.02}} \right)}_{\Sigma 2.01}}{{\text{O}}_{4}}.$ The general and end-member formulas are (Fe,Mg)(Cr,Al)2O4 and FeCr2O4. Synchrotron X‑ray diffraction reveals that chenmingite has an orthorhombic Pnma CaFe2O4-type (CF) structure with unit-cell dimensions: a = 9.715(6) Å, b = 2.87(1) Å, c = 9.49(7) Å, V = 264.6(4) Å3, and Z = 4. Both chenmingite and xieite formed by solid-state transformation of precursor chromite under high pressure and high temperature during the Tissint impact event on Mars. The xieite regions are always in contact with melt pockets, whereas chenmingite lamellae only occur within chromite, a few micrometers away from the melt pockets. This arrangement suggests that chenmingite formed under similar pressures as xieite but at lower temperatures, in agreement with experimental studies. [ABSTRACT FROM AUTHOR]

A new high‐pressure silicate, (Mg,Fe,Si)2(Si,□)O4 with a tetragonal spinelloid structure, was discovered within shock melt veins in the Tenham and Suizhou meteorites, two highly shocked L6 ordinary chondrites. Relative to ringwoodite, this phase exhibits an inversion of Si coupled with intrinsic vacancies and a consequent reduction of symmetry. Most notably, the spinelloid makes up about 30–40 vol% of the matrix of shock veins with the remainder composed of a vitrified (Mg,Fe)SiO3 phase (in Tenham) or (Mg,Fe)SiO3‐rich clinopyroxene (in Suizhou); these phase assemblages constitute the bulk of the matrix in the shock veins. Previous assessments of the melt matrices concluded that majorite and akimotoite were the major phases. Our contrasting result requires revision of inferred conditions during shock melt cooling of the Tenham and Suizhou meteorites, revealing in particular a much higher quench rate (at least 5 × 103 K s−1) for veins of 100–500 μm diameter, thus overriding formation of the stable phase assemblage majoritic garnet plus periclase. [ABSTRACT FROM AUTHOR]

Nuwaite (Ni6GeS2, IMA 2013-018) and butianite (Ni6SnS2, IMA 2016-028) are two new chalcogenide minerals, occurring as micrometer-sized crystals with grossular, Na-bearing melilite, heazlewoodite, and Ge-bearing Ni-Fe alloys in veins and as mono-mineralic crack-filling material in igneous diopside in the Type B1 Ca-Al-rich inclusion (CAI) ACM-2 from the Allende CV3 carbonaceous chondrite. The chemical composition of type nuwaite is (wt%) Ni 65.3, S 10.3, Ge 8.2, Te 7.9, Sn 5.1, and Fe 1.7, with a sum of 98.5 and an empirical formula of (Ni5.95Fe0.16)(Ge0.60Sn0.23)(S1.72Te0.33). The simplified formula is Ni6(Ge,Sn)(S,Te)2, leading to an end-member of Ni6GeS2. The chemical composition of type butianite is (wt%) Ni 62.1, Sn 8.9, Te 10.3, S 8.9, Ge 5.3, Fe 1.3, sum 99.1, giving rise to an empirical formula of (Ni5.93Fe0.13)(Sn0.52Ge0.41)(S1.56Te0.45). Butianite's simplified formula is Ni6(Sn,Ge) (S,Te)2 and the end-member formula is Ni6SnS2. Both nuwaite and butianite have an I4/mmm inter-growth structure with a = 3.65 Å, c = 18.14 Å, V = 241.7 Å3, and Z = 2. Their calculated densities are 7.24 and 7.62 g/cm3, respectively. Nuwaite and butianite are the first known meteoritic minerals with high Ge and Sn concentrations. Nuwaite and butianite are very late-stage, vapor-deposited, alteration products, filling in pores within preexisting grossular-rich alteration veins and cracks in igneous Al,Ti-diopside. These phases and associated heazlewoodite and Ge-bearing alloys are observed only within the Ca-,Al-rich inclusion (CAI) and not outside it or at the inclusion-matrix interface. As only sections in one half of ACM-2 contain nuwaite/butianite, they were probably derived through a relatively low fO2-fS2 sulfidation process, in which a highly localized, low-temperature Ge-, Sn-bearing fluid interacted with a portion of the host CAI. It is likely that the fluid became relatively more Sn- and Te-enriched with time and that crack fillings post-date vein fillings, possibly due to a late remobilization of vein sulfides. [ABSTRACT FROM AUTHOR]

We determined activity-composition relationships for the Pt-Fe system by equilibrating Fe-oxides with Pt-Fe alloys at temperatures in the range of 1200-1400 [degrees] C and oxygen fugacities from 1.6 to 7.7 log units above the iron-wustite (IW) buffer. The system is characterized by strong negative deviations from ideality throughout the investigated temperature range (e.g., [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] Our data are consistent with an asymmetric regular solution of the form: [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] where [WG.sub.1] = -138.0 [+ or -] 3.3 kJ/mol and [WG.sub.2] = -90.8 [+ or -] 24.0 kJ/mol (1[Sigma]). Based on experiments at 1200-1400 [degrees] C, variations in the activity coefficients at a given composition are consistent with ln [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. The Pt-Fe alloy composition in equilibrium with a FeO-bearing silicate liquid can be obtained from: [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] where [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is the standard state free energy for the reaction [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. We obtained values of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] from our model and used the program MELTS together with the thermodynamic properties of these elements to evaluate activities of [SiO.sub.2] and [Fe.sub.2][SiO.sub.4] components in the liquid and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. We provide sample calculations showing how to predict the optimum Fe concentrations for pre-saturation of Pt-bearing containers to reduce Fe loss from the charge during experiments on magmatic liquids at high temperatures and pressures from 1 atm to 40 kbar.