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Crystal chemical algorithms were used to estimate the chemical composition of selected mineral phases observed with the CheMin X-ray diffractometer onboard the NASA Curiosity rover in Gale crater, Mars. The sampled materials include two wind-blown soils, Rocknest and Gobabeb, six mudstones in the Yellowknife Bay formation (John Klein and Cumberland) and the Murray formation (Confidence Hills, Mojave2, and Telegraph Peak), as well as five sandstones, Windjana and the samples of the unaltered Stimson formation (Big Sky and Okoruso) and the altered Stimson formation (Greenhorn and Lubango). The major mineral phases observed with the CheMin instrument in the Gale crater include plagioclase, sanidine, P21/c and C2/c clinopyroxene, orthopyroxene, olivine, spinel, and alunite-jarosite group minerals. The plagioclase analyzed with CheMin has an overall estimated average of An40(11) with a range of An30(8) to An63(6). The soil samples, Rocknest and Gobabeb, have an average of An56(8) while the Murray, Yellowknife Bay, unaltered Stimson, and altered Stimson formations have averages of An38(2), An37(5), An45(7), and An35(6), respectively. Alkali feldspar, specifically sanidine, average composition is Or74(17) with fully disordered Al/Si. Sanidine is most abundant in the Wind-jana sample (∼26 wt% of the crystalline material) and is fully disordered with a composition of Or87(5). The P21/c clinopyroxene pigeonite observed in Gale crater has a broad compositional range {[Mg0.95(12)-1.54(17)Fe0.18(17)-1.03(9)Ca0.00-0.28(6)]Σ2Si2O6} with an overall average of Mg1.18(19)Fe0.72(7)Ca0.10(9)Si2O6. The soils have the lowest Mg and highest Fe compositions [Mg0.95(5)Fe1.02(7)Ca0.03(4)Si2O6] of all of the Gale samples. Of the remaining samples, those of the Stimson formation exhibit the highest Mg and lowest Fe [average = Mg1.45(7)Fe0.35(13)Ca0.19(6)Si2O6]. Augite, C2/c clinopyroxene, is detected in just three samples, the soil samples [average = Mg0.92(5)Ca0.72(2)Fe0.36(5)Si2O6] and Windjana (Mg1.03(7)Ca0.75(4)Fe0.21(9)Si2O6). Orthopyroxene was not detected in the soil samples and has an overall average composition of Mg0.79(6)Fe1.20(6)Ca0.01(2)Si2O6 and a range of [Mg0.69(7)-0.86(20)Fe1.14(20)-1.31(7)Ca0.00-0.04(4)]Σ2Si2O6, with Big Sky exhibiting the lowest Mg content [Mg0.69(7)Fe1.31(7)Si2O6] and Okoruso exhibiting the highest [Mg0.86(20)Fe1.14(20)Si2O6]. Appreciable olivine was observed in only three of the Gale crater samples, the soils and Windjana. Assuming no Mn or Ca, the olivine has an average composition of Mg1.19(12)Fe0.81(12)SiO4 with a range of 1.08(3) to 1.45(7) Mg apfu. The soil samples [average = Mg1.11(4)Fe0.89SiO4] are significantly less magnesian than Windjana [Mg1.35(7)Fe0.65(7)SiO4]. We assume magnetite (Fe3O4) is cation-deficient (Fe3-x∎xO4) in Gale crater samples [average = Fe2.83(5)∎0.14O4; range 2.75(5) to 2.90(5) Fe apfu], but we also report other plausible cation substitutions such as Al, Mg, and Cr that would yield equivalent unit-cell parameters. Assuming cation-deficient magnetite, the Murray formation [average = Fe2.77(2)∎0.23O4] is noticeably more cation-deficient than the other Gale samples analyzed by CheMin. Note that despite the presence of Ti-rich magnetite in martian meteorites, the unit-cell parameters of Gale magnetite do not permit significant Ti substitution. Abundant jarosite is found in only one sample, Mojave2; its estimated composition is (K0.51(12)Na0.49)(Fe2.68(7)Al0.32)(SO4)2(OH)6. In addition to providing composition and abundances of the crystalline phases, we calculate the lower limit of the abundance of X-ray amorphous material and the composition thereof for each of the samples analyzed with CheMin. Each of the CheMin samples had a significant proportion of amorphous SiO2, except Windjana that has 3.6 wt% SiO2. Excluding Windjana, the amorphous materials have an SiO2 range of 24.1 to 75.9 wt% and an average of 47.6 wt%. Windjana has the highest FeOT (total Fe content calculated as FeO) at 43.1 wt%, but most of the CheMin samples also contain appreciable Fe, with an average of 16.8 wt%. With the exception of the altered Stimson formation samples, Greenhorn and Lubango, the majority of the observed SO3 is concentrated in the amorphous component (average = 11.6 wt%). Furthermore, we provide average amorphous-component compositions for the soils and the Mount Sharp group formations, as well as the limiting element for each CheMin sample.

An updated and expanded data set that consists of 214 plagioclase-liquid equilibrium pairs from 40 experimental studies in the literature is used to recalibrate the thermodynamic model for the plagioclase-liquid hygrometer of Lange et al. (2009); the updated model is applicable to metaluminous and alkaline magmas. The model is based on the crystal-liquid exchange reaction between the anorthite (CaAl2Si2O8) and albite (NaAlSi3O8) components, and all available volumetric and calorimetric data for the pure end-member components are used in the revised model. The activities of the crystalline plagioclase components are taken from Holland and Powell (1992). Of the 214 experiments, 107 are hydrous and 107 are anhydrous. Four criteria were applied for inclusion of experiments in the final data set: (1) crystallinities <30%; (2) pure-H2O fluid saturated; (3) compositional totals (including H2O component) of 97-101% for hydrous quenched glasses and 98.5-101 for anhydrous quenched glasses; and (4) melt viscosities ≤5.2 log10 Pa·s. The final data set spans a wide range in liquid composition (45-80 wt% SiO2; 1-10 wt% Na2O+K2O), plagioclase composition (An17-95), temperature (750-1244°C), pressure (0-350 MPa), and H2O content (0-8.3 wt%). The water solubility model of Zhang et al. (2007) was applied to all hydrous experiments. The standard error estimate on the hygrometer model is 0.35 wt% H2O, and all liquid compositions are fitted equally well. Application of the model as a thermometer recovers temperatures to within ±12°, on average. Tests of the hygrometer on anhydrous piston-cylinder experiments in the literature, not included in the regression, show that the model is accurate at all pressures where plagioclase is stable. Applications of the hygrometer are made to natural rhyolites (Bishop Tuff, Katmai, and TobaTuff) with reported H2O analyses in quartz-hosted melt inclusions from the literature; the results show agreement. Applications of the hygrometer/thermometer are additionally made to natural rhyolites from Iceland and Glass Mountain, California. The updated model can be downloaded either as a program in Excel format or as a MatLab script from the Data Repository.

We quantify the metamorphic pressure-temperature (P-T) conditions for a newly discovered silica-undersaturated high-pressure granulite (HPG) from the Central Maine Terrane (CMT) in northeastern Connecticut, U.S.A. The rocks lie within the Acadian-Neoacadian orogenic belt (Devonian) and form part of the Brimfield Schist. The Brimfield and the adjacent Bigelow Brook Formation contain silica-saturated rocks that have previously been shown to have undergone ∼1000 °C metamorphism. The pressure was less well constrained at ≥ ∼1 GPa. Silica-undersaturated rocks hold underutilized potential for pinpointing peak metamorphic conditions, particularly pressure, because of their resilience to melting and the variety of refractory minerals they contain. The typical silica-undersaturated mineral assemblage is garnet + spinel + corundum + plagioclase + K-feldspar + biotite + ilmenite. Leucosomes are syenites consisting of two feldspars ± biotite. Plagioclase is commonly antiperthitic, particularly in feldspathic domains surrounding peritectic garnet; such garnet crystals reach ∼10 cm in diameter. Alkali feldspars are perthitic. The rocks contain remarkable ellipsoidal spinels as much as 5.5 cm long comprising discrete crystallographic domains hosting crystallographically oriented lamellae of a Fe-Ti phase, most likely ilmenite. Corundum is usually colorless, but can also be found as sapphire in shades of pink, purple, and blue, particularly in antiperthite-rich domains surrounding large garnets. Some sapphires are concentrically color zoned. We carried out a P-T estimation using ternary feldspar reintegration thermometry of metamorphic antiperthites together with pseudosection modeling. Samples texturally and chemically record near-eclogite facies equilibration at minimum conditions of ∼1040 °C and ∼1.8 GPa, establishing the CMT in northeastern CT as the first known HPG locality in the U.S. These results are consistent with high P2O5 levels found in garnet (0.18 wt%), Ti-in-biotite thermometry, regional sillimanite pseudomorphs after kyanite, and preliminary experimental work on melt inclusions in garnet (Ferrero et al. 2017). The leucosomes provide strong evidence that partial melting of silica-undersaturated rocks at HPG conditions can produce syenitic magmata. Strongly melt-depleted silica-undersaturated rocks may also be protoliths for garnet + spinel + corundum xenoliths reported from kimberlites. The presence of HPG gneisses demonstrates that the large-scale thrusts of the CMT sample the deepest roots of the orogenic belt (60-70 km), and perhaps even deeper subduction zone lithologies as well.

Brittle reactivation of plastic shear zones is frequently observed in geologically old terranes. To better understand such deformation zones, we have studied the >700 Ma long structural history of the Himdalen–Ørje Deformation Zone (HØDZ) in SE Norway by K–Ar and 40Ar–39Ar geochronology, and structural characterization. Several generations of mylonites make up the ductile part of HØDZ, the Ørje Shear Zone. A 40Ar–39Ar white mica plateau age of 908.6 ± 7.0 Ma constrains the timing of extensional reactivation of the Ørje mylonite. The mylonite is extensively reworked during brittle deformation events by the Himdalen Fault. 40Ar–39Ar plateau ages of 375.0 ± 22.7 Ma and 351.7 ± 4.4 Ma from pseudotachylite veins and K–Ar ages of authigenic illite in fault gouge at c. 380 Ma are interpreted to date initial brittle deformation, possibly associated with the Variscan orogeny. Major brittle deformation during the Early–Mid Permian Oslo Rift is documented by a 40Ar–39Ar pseudotachylite plateau age of 294.6 ± 5.2 Ma and a K–Ar fault gouge age of c. 270 Ma. The last datable faulting event is constrained by the finest size fraction in three separate gouges at c. 200 Ma. The study demonstrates that multiple geologically significant K–Ar ages can be constrained from fault gouges within the same fault core by combining careful field sampling, structural characterization, detailed mineralogy and illite crystallinity analysis. We suggest that initial localization of brittle strain along plastic shear zones is controlled by mechanical anisotropy of parallel-oriented, throughgoing phyllosilicate-rich foliation planes within the mylonitic fabric.

The full elastic tensors of two K-rich monoclinic alkali feldspars, Or83Ab15 sanidine and Or93Ab7 orthoclase, have been determined by using the Impulse Stimulated Light Scattering technique to measure surface acoustic wave velocities. The new data confirm that alkali feldspars exhibit extreme elastic anisotropy, so the bounds of their isotropic average properties span a wide range. The measured adiabatic moduli are, for Or83Ab15 and Or93Ab7, respectively, KReuss = 54.7(7), 54.5(5) GPa; KVoigt = 62.9(1.1), 64.4(0.6) GPa; GReuss = 24.1(1), 24.5(1) GPa; and GVoigt = 36.1(5), 36.1(7) GPa. The small differences in moduli between the samples suggests that variations in composition and in state of Al, Si order only have minor effects on the average elastic properties of K-rich feldspars. The new measurements confirm that the earliest determinations of elastic wave velocities of alkali feldspars, widely used to calculate wave velocities in rocks, resulted in velocities systematically and significantly too slow by 10% or more.

The Miocene rhyolites of the Spor Mountain Formation host Earth's largest beryllium deposit, which produced 85% of the world's beryllium in 2010. The fresh lava is extremely enriched in Be (up to 75 ppm in matrix glass). We have examined the rhyolite to better understand the Be enrichment. The Spor Mountain rhyolite contains ∼40% quartz, ∼40% sanidine, ∼10% biotite, and ∼10% plagioclase, along with accessory fluorite, columbite, euxenite, fergusonite, monazite, thorite, and zircon. Two types of rhyolite are present within the Spor Mountain Formation, a less-evolved magma (1150 ppm Rb, 42 ppm Be, 0.7 wt% F in glass) and a more-evolved magma (1710 ppm Rb, 75 ppm Be, 1.6 wt% F in glass). Eruption temperatures estimated using two-feldspar (Elkins and Grove 1990; Putirka 2008; Benisek et al. 2010), plagioclase-liquid and alkali feldspar-liquid (Putirka 2008), Ti-in-quartz (Thomas et al. 2010, 2015; Huang and Audetat 2012), biotite (Righter and Carmichael 1996), and zircon saturation (Boehnke et al. 2013) geothermometers converge on 718 °C for the less-evolved magma and 682 °C for the more-evolved magma. Using the Ti-in-Qz equation of Huang and Audetat (2012), the pre-eruptive pressure of the Spor Mountain rhyolite system is estimated to be about 2 kbar at 700 °C. Water content of the rhyolite melt was less than <5 wt%, based on the co-crystallization of all four major mineral phases at 700 °C, and the magma was water undersaturated (Webster et al. 1987). Viscosity of the rhyolite was about 106.2 Pa·s for the less-evolved rhyolite and 105.8 Pa·s for the more-evolved rhyolite. Fluorine lowered the melt viscosity, though not by a large amount (less than 0.5 log units at 1.6 wt% F). Partition coefficients for Be and other trace elements were determined for biotite, sanidine, plagioclase, and quartz from laser ablation-inductively coupled plasma-mass spectrometry analyses. Partition coefficients for trace elements in feldspars from the Spor Mountain rhyolite are generally higher than for feldspars from other silicic magmas and lower for biotite. The enrichment of beryllium in the Spor Mountain rhyolite was aided by its high incompatibility in the major mineral phases, with a bulk partition coefficient <0.1. Trace element models using the measured partition coefficients are inconsistent with accumulation of increments of melt formed by different degrees of partial melting and cannot explain the great depletion of compatible elements. Rather, the trace element abundances and Nd and Sr isotopic compositions are consistent with derivation of rhyolite by ∼25% partial melting of crust hybridized with mantle-derived components, followed by extensive fractional crystallization (75%). The combination of these magmatic processes set the stage for the formation of a world-class beryllium deposit.

The new mineral mazorite, ideally Ba3(PO4)2, a P-analogue of gurimite Ba3(VO4)2, was discovered in rankinite paralava hosted by the massive gehlenite-bearing pyrometamorphic rocks of the Hatrurim Complex in Israel. It has also recently been discovered in xenolith samples from the Bellerberg volcano in Germany. Holotype mazorite usually forms colourless plate-like crystals up to 70-100 µm in length but also occurs in small aggregates in association with other rare Ba-bearing minerals such as zadovite, celsian, hexacelsian, bennesherite, sanbornite, walstromite, fresnoite, gurimite, alforsite and barioferrite. The mineral is transparent, exhibits vitreous lustre and has a good cleavage on (001). Optically, mazorite is uniaxial (+), with ω = 1.760(3) and ε = 1.766(3) (λ = 589 nm). The empirical formula of the holotype mazorite calculated on 8O is (Ba2.69K0.22Na0.04Ca0.02Sr0.01)Σ2.98(P1.16V0.57S0.24Al 0.04S i0.03)Σ2.04O8. Mazorite crystallises in space group R3̄m, with unit-cell parameters a = 5.6617(5) Å, c = 21.1696(17) Å, V = 587.68(9) Å3 and Z = 3. Its crystal structure consists of BaO12, BaO10, and PO4 polyhedra, ordered along the c-axis in PO4-BaO10-BaO12-BaO10-PO4 columnar arrangement characteristic for palmierite-supergroup minerals. A tetrahedrally coordinated site is generally occupied by P5+ but can be partially substituted by V5+ and S6+ This substitution is shown in the Raman spectrum of mazorite, which reveals bands that can be assigned to the stretching and bending vibrations of (PO4)3-, (VO4)3- and (SO4)2- groups. The Raman spectra of mazorite from two localities (Hatrurim and Bellerberg) and spectra of minerals belonging to the mazorite Ba3(PO4)2 to gurimite Ba3(VO4)2 solid-solution series are presented. The gradual shift of the Raman bands, caused by cation substitutions, is well observed. The high V5+ → P5+ substitution is also observed for gurimite, for which the first X-ray structural data are also presented. Mazorite and other Ba-bearing minerals crystallised from a small portion of residual melt enriched in incompatible elements, such as Ba, V, P, U, S, Ti and Nb, at a temperature of ∼1000°C.

Ferroinnelite, Ba4Ti2Na(NaFe2+)Ti(Si2O7)2[(SO4)(PO4)]O2[O(OH)], is a new mineral from the Phlogopite deposit, Kovdor alkaline massif, Kola Peninsula, Russia. In an agpaitic pegmatite, ferroinnelite occurs as transparent elongated platy to tabular crystals up to 0.15 mm long. Associated minerals are cancrinite, orthoclase, aegirine-augite, magnesio-arfvedsonite, golyshevite and fluorapatite. The mineral is yellow to yellow brown with a vitreous lustre and a white streak, Dcalc. is 4.088 g/cm3. Ferroinnelite is triclinic, space group P1̄, a = 5.3994(8), b = 7.09239(13), c = 14.7345(4) Å, α = 98.4086(19), β = 94.3275(18), γ = 90.0133(13)°, V = 556.56(8) Å3. The chemical composition of ferroinnelite is SO3 5.47, Nb2O5 0.45, P2O5 4.59, ZrO2 0.13, TiO2 16.91, SiO2 17.55, Al2O3 0.06, BaO 42.83, SrO 1.01, FeO 3.34, MnO 0.97, CaO 0.09, MgO 0.64, K2O 0.01, Na2O 4.47, H2O 1.11, F 0.15, O = F -0.06, total 99.72 wt.%, with H2O calculated from structure refinement. The empirical formula calculated on 26 (O + F) apfu is (Na1.95Fe2+0.64Mg0.21Mn2+0.19Ca0.02)Σ3.01(Ba3.84Sr0.13Na0.03) Σ4.00(Ti2.91Nb0.05Al0.02Zr0.01Mg0.01)Σ3.00Si4.02S0.94P0.8 9H1.70O25.89F0.11, Z = 1. The crystal structure was refined to an R1 index of 7.45% from 4485 unique reflections (Fo > 4σF). The structure is a combination of a TS (Titanium Silicate) and an I (intermediate) blocks. The TS block consists of HOH sheets (H - heteropolyhedral and O - octahedral). The O sheet is composed of Ti-, Na- and (Na,Fe2+)-octahedra, the H sheet, of [5]Ti-polyhedra and Si2O7 groups. The I block contains T sites, statistically occupied by S and P, and Ba atoms. Ideal compositions of the TS and I blocks are {Ti2Na(NaFe2+)Ti(Si2O7)2O2[O(OH)]}3- and {Ba4[(SO4)(PO4)]}3+. Ferroinnelite is a new member of the lamprophyllite group of the seidozerite supergroup. It is isostructural with innelite-1A, Ba4Ti2Na(NaMn2+)Ti(Si2O7)2[(SO4)(PO4)]O2[O(OH)]. Ferroinnelite and innelite are related by the following cation substitution at the MO3 site in the O sheet: Fe2+fer ⇌ Mn2+inn. IR and Raman spectroscopies confirm presence of OH and H2O groups in ferroinnelite and innelite.