Band 107, Heft 2

Alumino-oxy-rossmanite, ideally □Al 3 Al 6 (Si 5 AlO 18 )(BO 3 ) 3 (OH) 3 O, is here described as a new member of the tourmaline supergroup. It is an early magmatic Al-rich oxy-tourmaline from a small pegmatitic body embedded in amphibolite and biotite-rich paragneiss. This new pink tourmaline was found in a Moldanubian pegmatite (of the Drosendorf Unit) that occurs in a large quarry near the village of Eibenstein an der Thaya, Waidhofen an der Thaya district, Lower Austria, Austria. The empirical formula of the holotype was determined on the basis of electron microprobe analysis (EMPA), secondary ion mass spectrometry (SIMS), spectroscopical methods (optical absorption and infrared spectroscopy), and crystal-structure refinement (SREF) as X (□ 0.53 Na 0.46 Ca 0.01 ) Y (Al 2.37 Mn 3 0.21 + Li 0.16 □ 0.14 Mn 2 0.07 + Fe 3 0.03 + Fe 2 0.01 + Ti 4 0.01 + ) Z Al6(Si 5.37 Al 0.41 B 0.22 O 18 )(BO 3 ) 3 V [(OH) 2.77 O 0.23 ] W [O 0.80 (OH) 0.15 F 0.05 ]. Chemical composition (wt%) is: SiO 2 33.96, TiO 2 0.10, Al 2 O 3 47.08, B 2 O 3 11.77, FeO 0.08, Fe 2 O 3 0.23, MnO 0.52, Mn 2 O 3 1.70, CaO 0.04, Li 2 O 0.25, ZnO 0.03, Na 2 O 1.51, H 2 O 2.79, F 0.09, total 100.11. The presence of relatively high amounts of trivalent Mn in alumino-oxy-rossmanite is in agreement with the observation that the OH groups are present at a lower concentration than commonly found in other Al-rich and Li-bearing tourmalines. The crystal structure of alumino-oxy-rossmanite [space group R 3 m ; a = 15.803(1), c = 7.088(1) Å; V = 1532.9(3) Å 3 ] was refined to an R 1( F ) value of 1.68%. The eight strongest X‑ray diffraction lines in the (calculated) powder pattern [ d in Å ( I ) hkl ] are: 2.5534 (100) 051, 3.9508 (85) 220, 2.9236 (78) 122, 4.1783 (61) 211, 2.4307 (55) 012, 2.0198 (39) 152, 1.8995 (30) 342, 6.294 (28) 101. The most common associated minerals are quartz, albite, microcline, and apatite. Beryl and, in places, schorl are also found as primary pegmatitic phases. Because of the low mode of associated mica (muscovite), we assume that the silica melt, which formed this pegmatite, crystallized under relatively dry conditions, in agreement with the observation that alumino-oxy-rossmanite contains a lower amount of OH than most other tourmalines. This new member of the tourmaline supergroup exhibits the most Al-rich end-member composition of the tourmaline supergroup (theoretical content: ~54 wt% Al 2 O 3 ). The significant content of tetrahedrally coordinated Al could reflect the relatively high-temperature conditions (~700 °C) inferred for crystallization of the pegmatite. Alumino-oxy-rossmanite was named for its chemical relationship to rossmanite, □(LiAl 2 )Al 6 (Si 6 O 18 ) (BO 3 ) 3 (OH) 3 (OH), which in turn was named after George R. Rossman, Professor of Mineralogy at the California Institute of Technology (Pasadena, California, U.S.A.).

Concentrations of fluorine and chlorine were measured in glasses (quenched melts) and coexisting clinopyroxene, orthopyroxene, olivine, and plagioclase in run products of experiments previously used to measure sulfur partitioning between these phases. The partitioning of F between clinopyroxene and silicate melt was determined in 13 experiments at a variety of pressures, temperatures, and melt compositions ranging from basaltic to dacitic (49 to 66 wt% SiO 2 ) at 0.8 to 1.2 GPa and 1000 to 1240 °C, at hydrous and anhydrous conditions. Additionally, we determined the crystal-melt partitioning of F for 4 experiments with plagioclase, 2 with orthopyroxene, and 1 with olivine. Although Cl was also measured in the experiments, the concentrations in the crystals are close to background concentration levels. The partition coefficients of fluorine between clinopyroxene and melt varied from ~0.09 to 0.29 and were linearly dependent upon the concentration of aluminum in the octahedral M1 site of clinopyroxene. Similar relationships are seen when our results are combined with previous measurements of the fluorine partition coefficient between clinopyroxene and melt, but each study shows its own unique correlation between the F partition coefficient and Al M 1. These dissimilarities in correlations with Al M1 are attributed to difering analytical protocols used in the various studies. However, the combined data set demonstrates a linear correlation with Al M 1, the inverse of the NBO/T ratio of the melt (T/NBO), pressure and temperature, which can be described as: ln(DFCpx/L)=(0.2298±0.04847)(T/NBO)−(1.029±0.8045)(AlMI)−(3889±1803)(1/T)−(0.5472±0.1084)(P)+0.5871±1.304 $$\begin{matrix}\ln \left( D_{\text{F}}^{\text{Cpx/L}} \right)=(0.2298\pm 0.04847)(\text{T}/\text{NBO})-(1.029\pm 0.8045)\left( \text{A}{{\text{l}}^{\text{MI}}} \right)-(3889\pm 1803)(1/T)- \\(0.5472\pm 0.1084)(P)+0.5871\pm 1.304 \\\end{matrix}$$ where each uncertainty is 1 standard error in the fit (as calculated by the R-project software), T is in K, and P is in GPa. Although this relationship reproduces 81% of the partitioning data to within 25% (relative), the different linear trends of the partition coefficient, D F Cpx/L vs. Al M1 from different laboratories suggest the need for additional investigations and development of clinopyroxene standards with certified fluorine compositions. Nevertheless, we conclude that the self-consistency of each study indicates that F partition coefficients determined using one protocol can be applied to minerals or glasses analyzed using the same protocol and ion microprobe to better understand the storage and transport of fluorine in magmatic systems.

The Shatanjiao pluton, located in the eastern Tongling region (Eastern China), is of great research significance for the study of magma evolutionary processes because this pluton is related to the regional Cu-Au mineralization. Zircon U-Pb dating on two granodiorite samples from this pluton yields ages of 141.9 ± 3.1 Ma (MSWD = 0.07) and 141.9 ± 3.3 Ma (MSWD = 0.03), respectively, which overlap the range of intense Late Jurassic to Early Cretaceous magmatism in the Tongling region. Based on the Sr content of apatite from the Shatanjiao granodiorites, they are subdivided into high-Sr apatite (apatite-I: 754–1242 ppm, mean = 1107 ppm) and low-Sr apatite (apatite-II: 415–613 ppm, mean = 507 ppm). Both apatite-I and apatite-II are characterized by high-Sr and -Sr/Y ratios and inconspicuous negative-Eu anomalies, indicating that these granodiorites have a likely adakite affinity. Considering their low-Rb contents (<0.05 ppm), in situ Sr isotopes of these apatite grains show 87 Sr/ 86 Sr ratios of 0.70848–0.71494 and 0.70767–0.71585 for apatite-I and apatite-II, respectively, indicating that the 87 Sr/ 86 Sr ratios of both apatite groups can represent the Sr isotopic compositions of their host rocks. Moreover, the La/Sm and Sr/Th ratios of both apatite groups suggest that the studied granodiorites might be sourced from the partial melting of subducted ocean slabs and overlying sediments. Based on their zircon trace element compositions, the calculated temperature and oxygen fugacity for the magma are characterized by high temperatures (mean T = 646 °C) and high oxygen fugacity (mean Ce 4+ /Ce 3+ ratios = 341). On the basis of MgO, FeO, SiO 2 , and ΣREE contents of apatite, we further suggest that apatite-I and apatite-II might have crystallized at the early and late stages of magma evolution, respectively. Because apatite-I has much higher Eu/Eu* ratios (0.56–0.76) but lower (La/Yb) N ratios (7.85–28.6) than apatite-II of 0.39–0.58 and 95.9–132, respectively, it is indicated that plagioclase, garnet, hornblende, and zircon might control the trace element composition of melt during the magma evolutionary history, which were recorded by the apatite. Therefore, apatite can be an ideal tracer to reflect the sequence of multistage magma evolution.

As ascending magmas undergo cooling and crystallization, water and fluid-mobile elements (e.g., Li, B, C, F, S, Cl) become increasingly enriched in the residual melt until fluid saturation is reached. The consequential exsolution of a fluid phase dominated by H 2 O (magmatic volatile phase or MVP) is predicted to occur early in the evolution of long-lived crystal-rich “mushy” magma reservoirs and can be simulated by tracking the chemical and physical evolution of these reservoirs in thermomechanical numerical models. Pegmatites are commonly interpreted as the products of crystallization of late-stage volatile-rich liquids sourced from granitic igneous bodies. However, little is known about the timing and mechanism of extraction of pegmatitic liquids from their source. In this study, we review findings from thermomechanical models on the physical and chemical evolution of melt and MVP in near-solidus magma reservoirs and apply these to textural and chemical observations from pegmatites. As an example, we use a three-phase compaction model of a section of a mushy reservoir and couple this to fluid-melt and mineral-melt partition coeficients of volatile trace elements (Li, Cl, S, F, B). We track various physical parameters of melt, crystals, and MVP, such as volume fractions, densities, velocities, as well as the content in the volatile trace elements mentioned above. The results suggest that typical pegmatite-like compositions (i.e., enriched in incompatible elements) require high crystallinities (>70–75 vol% crystals) in the magma reservoir, at which MVP is eficiently trapped in the crystal network. Fluid-mobile trace elements can become enriched beyond contents expected from closed-system equilibrium crystallization by transport of MVP from more-evolved mush domains. From a thermomechanical perspective, these observations indicate that, rather than from melt, pegmatites may more likely be generated from pressurized, solute-rich MVP with high concentrations of dissolved silicate melt and fluid-mobile elements. Hydraulic fracturing provides a mechanism for the extraction and emplacement of such pegmatite- generating liquids in and around the main parental near-solidus mush as pockets, dikes, and small intrusive bodies. This thermomechanical framework for the extraction of MVP from mushes and associated formation of pegmatites integrates both igneous and hydrothermal realms into the concept of transcrustal magmatic distillation columns.

The Au mineralization in the giant Jiaodong Au province is enigmatic and difficult to fit current classic mineralization models, primarily because of uncertainties as to the sources of ore-forming fluids and metals. The ca. 120 Ma Au mineralization has been previously proposed to have occurred during a magmatic lull, which would negate a magmatic-hydrothermal genetic model. However, recent drilling has revealed a buried mineralized monzonite equivalent in age to the Au mineralization in the Linglong goldfield. Here, we present comprehensive textural, geochemical [LA-(MC)-ICP-MS trace element, Nd and S isotopes] and geochronological (LA-ICP-MS U-Pb dating) analyses of titanite and pyrite from this previously unrecognized monzonite. Three types of titanite were distinguished, including magmatic Ttn1 and hydrothermal Ttn2 and Ttn3, which show indistinguishable U-Pb ages (120.7 ± 3.1 and 120.9 ± 2.6 Ma), REE patterns and Nd isotopes [ε Nd (t) = –14.7 to –12.9], implying that hydrothermal fluids were directly exsolved from the monzonitic magma, contemporaneous with the large-scale Au mineralization at ca. 120 Ma. The Nd isotopes of titanite potentially indicate a lower crustal source mixed with mantle materials for the monzonite. Four types of pyrite were analyzed, including magmatic Py1 from fresh biotite monzonite, hydrothermal Py2 from altered biotite monzonite, hydrothermal Py3 from quartz-pyrite veins with a monazite U-Pb age of 118.2 ± 4.6 Ma, and magmatic Py4 from mafic enclaves of the Gushan granite at ca.120 Ma. The δ 34 S values of magmatic Py1 and Py4 (+1.9 to +6.3‰, and +5.0 to +6.4‰, respectively) and hydrothermal Py2 and Py3 (+6.4 to +9.5‰ and +6.5 to +7.6‰, respectively) are consistent with sulfur isotopic fractionation between melt and fluid. Hydrothermal Py2 and Py3 also have higher Co, As, Ag, Sb, and Bi contents and submicrometer gold inclusions, implying that the magmatic-hydrothermal fluids were fertile for mineralization. This study highlights the importance of monzonite magmatism and exsolved fertile fluids in regional Au mineralization. Hydrous magmas at ca. 120 Ma probably extracted Au eficiently from the lower crustal-mantle sources and released auriferous fluids at the late magmatic stage, leading to the formation of Au deposits in the Jiaodong province.

Serpentine minerals exert important controls on the physical properties of ultramafic rocks and have the potential to influence deformation phenomena in fault zones and to control the release of water in subducted slabs. Sheet serpentine generally, and lizardite and amesite specifically, can adopt alternative crystallographic stacking arrangements called polytypes. Polytypism has been extensively studied in fully ordered crystals, but it remains largely enigmatic in the more common semi-disordered crystals that in long-range analyses such as X‑ray diffraction only exhibit random combinations of 0 b and ±1/3 b interlayer shifts. To date, atomic-resolution imaging to identify locally ordered polytypes has been precluded by the beam-sensitive nature of this hydrous magnesium silicate mineral. Here, we employed low-dose high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to study the polytypic structure of semi-disordered lizardite and amesite. Because the electron dose was as low as ~6000 e – /Å 2 , it was possible to directly resolve oxygen atomic columns and all the cations with a resolution of ~1 Å and reveal the short-range order. For lizardite, we identified long-period non-standard polytypes, including examples with 3, 4, 8, and 9 layers stemming from the ordering of the octahedral tilt along the a- axis. For amesite, we found short-range ordered polytypes with periodicities of up to 42 Å stemming from the ordering of interlayer shifts along the b -axis. The resolution was sufficient to determine the relative abundance of 6 R 2 , 6 R 1 , 2 H 1 , and 2 H 2 polytypes in amesite to be 46.1, 29.6, 7.7, and 1.9%, respectively. This is contrary to the expectation that the most common form of amesite is the 2 H 2 polytype, which may be more likely to form macroscopic crystals suitable for conventional X‑ray diffraction-based studies. We conclude that HAADF-STEM methods open the way for the characterization of beam-sensitive minerals and to resolve the structural details of less well-ordered (but possibly more abundant) minerals at a unit-cell scale.

Fluid inclusions in pegmatite minerals were studied using Raman spectroscopy to determine the carbon species. Carbon dioxide is very abundant in the aqueous liquid and vapor phases. Occasionally, CH 4 was found in the vapor. In the aqueous liquid, HCO 3 − was detected in fluid inclusions in tantalite-(Mn) from the Morrua Mine and in late-stage quartz from the Muiâne pegmatite and the Naipa Mine, all in the Alto Ligonha District, Mozambique. Moreover, we observed a carbonate (calcite group) in fluid inclusions in garnet from the Naipa Mine and in beryl from the Morrua Mine, both in the Alto Ligonha District, Mozambique, and a calcite-group carbonate and whewellite [CaC 2 O 4 ∙H 2 O] in fluid inclusions in topaz from Khoroshiv, Ukraine. The occurrence of oxalate is interpreted to be due to a reaction of some form of carbon (possibly CO or bitumen) with a peralkaline fluid. Our results support the hypothesis that, although counterintuitive, hydrogen carbonate-rich peralkaline fluids may locally be involved in the evolution of peraluminous granitic pegmatites, in which peralkaline minerals are normally absent or very rare.

Carbonate has often been identified in aqueous carbonic inclusions in spodumene-bearing and other pegmatites, but its origin remains unclear. Here, the conditions at which carbonate and hydrogen carbonate can be generated from spodumene, CO 2 and H 2 O, were studied using a hydrothermal diamond-anvil cell (HDAC) and Raman spectroscopy. In all experiments, spodumene persisted in aqueous carbonic solution up to the maximum temperature (600 to 800 °C). Heating of hydrogen carbonate/ oxalate solutions produced CO 2 - and HCO 3 − -rich peralkaline fluids, which resulted in strong corrosion of spodumene (and polylithionite-trilithionite) and, in one run, formation of zabuyelite [Li 2 (CO 3 )] crystals at low temperatures. The experiments indicate that the reaction of spodumene with CO 2 and H 2 O requires a peralkaline fluid to proceed rapidly. In addition, they show that spodumene crystallizes upon the heating of quartz, muscovite, and aqueous lithium carbonate solution. We conclude that if the aqueous fluid was rich in alkali hydrogen carbonate, zabuyelite in fluid inclusions in pegmatites can form both via a subsolidus reaction of CO 2 -bearing fluid inclusion with the spodumene host or by trapping a peralkaline fluid early in the evolution of simple or complex pegmatites. The results of our experimental study strengthen the conclusion that, although counterintuitive, hydrogen carbonate-rich peralkaline fluids may be involved in the evolution of peraluminous granitic pegmatites, in which peralkaline minerals are normally absent or very rare.

Using density functional theory electronic structure calculations, the equation of state, thermodynamic and elastic properties, and sound wave velocities of Fe 3 S at pressures up to 250 GPa have been determined. Fe 3 S is found to be ferromagnetic at ambient conditions but becomes non-magnetic at pressures above 50 GPa. This magnetic transition changes the c / a ratio leading to more isotropic compressibility, and discontinuities in elastic constants and isotropic sound velocities. Thermal expansion, heat capacity, and Grüneisen parameters are calculated at high pressures and elevated temperatures using the quasiharmonic approximation. We estimate Fe-Fe and Fe-S force constants, which vary with Fe environment, as well as the 56 Fe/ 54 Fe equilibrium reduced partition function in Fe 3 S and compare these results with recently reported experimental values. Finally, our calculations under the conditions of the Earth’s inner core allow us to estimate a S content of 2.7 wt% S, assuming the only components of the inner core are Fe and Fe 3 S, a linear variation of elastic properties between end-members Fe and Fe 3 S, and that Fe 3 S is kinetically stable. Possible consequences for the core-mantle boundary of Mars are also discussed.

In most geologic applications, if barite is present, it must be separated from zircon to enable analysis of the zircon. Current methods of barite removal include mechanical comminution in a ball mill or conversion to barium carbonate by boiling in an aqueous solution of sodium carbonate. Both procedures have potentially serious drawbacks. We optimized an alternative technique for barite removal to avoid these shortcomings. In repeated experiments, boiling in an aqueous solution of 0.1 M diethylenetriaminepentaacetic acid (DTPA) and 6 wt% potassium carbonate for one hour dissolved about 90% of sand-size barite grains. Examination of barite after boiling in DTPA solution revealed evidence for attacks on crystal surfaces in the form of microscopic scallops and pits. In contrast, zircon crystal surfaces were not detectably altered at the microscopic scale by a boiling solution of DTPA and potassium carbonate. The DTPA and potassium carbonate solution procedure may be superior to the other two barite removal methods in two ways. First, it might not introduce bias into the sample, in contrast to both of the other two methods. Second, it requires less time than the sodium carbonate solution technique. If future research shows that the DTPA and potassium carbonate solution technique does not affect isotopic systems in zircon, this method appears to be a favorable alternative to both milling and boiling in sodium carbonate solution.

Earth’s physical properties and mantle dynamics are strongly dependent on mantle grain size, shape, and orientation, but these characteristics are poorly constrained. Experimental studies provide an opportunity to simulate the grain growth kinetics of mantle aggregates. The experimentally determined grain sizes can be fit to the normal grain growth law ( G n – G n 0 ) = k 0 t ∙exp(–Δ H /R T ) and then be used to determine grain size throughout the mantle and geological time. The grain growth dynamics of spinel-orthopyroxene mixtures in the upper mantle are modeled here by experimentally producing small grain sizes in the range of 0.5 to 2 μm radius at pressures and temperatures equivalent to the spinel lherzolite stability field. To accurately measure the sizes of these small grains, we have developed a computer vision workflow; using a watershed transformation, which rapidly measures 68% more grains and produces a 20% improvement in the average grain size accuracy and repeatability when compared with manual methods. Using this automated approach, we have been able to identify a significant proportion of small grains, which have been overlooked when using manual methods. This additional population of grains, when fit to the normal grain growth law, highlights the influence of improved accuracy and sample size on the estimation of grain growth kinetic parameters. Our results demonstrate that automatic computer vision enables a systematic, fast, repeatable method of grain size analysis, across large data sets, improving the accuracy of experimentally determined grain growth kinetics.

A Raman spectroscopic study on the nature of As-S substitution in natural arsenian pyrite [Fe(S,As) 2 ] is presented, covering a compositional range of 0.01–4.6 at% As. Three Raman-active modes were identified in the Raman spectrum of a nearly pure pyrite: E g (344 cm −1 ), A g (379 cm −1 ), and T g (3) (432 cm −1 ). The Raman vibrational modes exhibit one-mode behavior, and the wavenumbers of optical modes vary approximately linearly with As content, correlating with the change in bond constants with increasing substitution of As for S. The linewidth of the A g mode increases with increasing As substitution, which may be attributed to the increase in lattice strain associated with the substitution of As for S. This study provides experimental evidence for As-induced structural evolution of pyrite from being stable to metastable before decomposing into other phases. Our results, together with those of another Raman study of arsenian pyrite whose As substitution is more complex, indicate that one cannot use Raman band shifts to determine As content, but for a given As content, can characterize the nature of As substitution, i.e., As for S or As for Fe or both.

The time and processes of hydrothermal mineralization are long-standing problems in geology. This work addresses these questions with reference to the Maoniuping giant rare earth elements (REE) deposit (southwest China), which has rare earth oxides (REO) reserves of 3.17 million tons with an average grade of 2.95 wt%. Bastnäsite is the dominant economic mineral, occurring as four distinct paragenetic types in the Maoniuping syenite–carbonatite complex: (1) primary euhedral bastnäsite (type-A) in syenite, with isolated melt inclusions; (2) macro-crystalline tabular euhedral bastnäsite (type-B) in pegmatitic dikes, with a diverse variety of fluid inclusions; (3) fine-grained, anhedral veinlet-disseminated bastnäsite (type-C) in syenite; and (4) coarse-grained anhedral bastnäsite (type-D) in carbonatite dikes, occurring as veinlets or interstitial to calcite, fluorite, and barite. From the paragenetic and compositional variations, it is inferred that type-A bastnäsite is of primary magmatic origin, whereas the other three types have characteristics of hydrothermal origins. In situ LA-ICP-MS U-Pb geochronology of the four types of bastnäsite results in lower intercept ages of 28.2 ± 0.5 Ma ( n = 95, MSWD = 5.10), 27.8 ± 0.4 Ma ( n = 43, MSWD = 0.73), 26.8 ± 0.7 Ma ( n = 50, MSWD = 0.83), and 25.8 ± 0.7 Ma ( n = 55, MSWD = 1.70), respectively, which are consistent with the weighted average 206 Pb/ 238 U and 208 Pb/ 232 Th ages by 207 Pb-correction method. Compositional variations of clinopyroxene and apatite from the associated syenite, pegmatitic and carbonatitic dikes indicate a genetic relationship of the Maoniuping alkaline complex. The compositions of clinopyroxene range from Ae 44–67 Di 14–18 Hd 17–41 in pegmatitic dikes, Ae 43–66 Di 6–20 Hd 21–38 in carbonatitic dikes to Ae 68–90 Di 0–3 Hd 10–30 in syenite. Apatites in the pegmatitic and carbonatitic dikes have similar compositions with higher F, total REE, and Sr, and lower CaO contents than those in the syenite, which suggests a cogenetic origin for the associated pegmatite and carbonatite. Clinopyroxene and apatite compositions suggest that the pegmatitic melt might differentiate directly from the initial carbonatitic melt rather than the syenitic magma. The bastnäsite U-Pb geochronology and minerals data indicate continuous magmatic-hydrothermal evolution for the REE mineralization in the Maoniuping alkaline complex.

Here we present new occurrences of amphibole in a suite of chromitites, dunites, and harzburgites from the mantle sequence of the Lycian ophiolite in the Tauride Belt, southwest Turkey. The amphibole occurs both as interstitial grains among the major constituent minerals and as inclusions in chromite grains. The interstitial amphibole shows generally decreasing trends in Na 2 O and Al 2 O 3 contents from the chromitites (0.14–1.54 wt% and 0.04–6.67 wt%, respectively) and the dunites (0.09–2.37 wt%; 0.12–11.9 wt%) to the host harzburgites (<0.61 wt%; 0.02–5.41 wt%). Amphibole inclusions in chromite of the amphibole-bearing harzburgites are poorer in Al 2 O 3 (1.12–8.86 wt%), CaO (8.47–13.2 wt%), and Na 2 O (b.d.l.–1.38 wt%) than their counterparts in the amphibole-bearing chromitites (Al 2 O 3 = 6.13–10.0 wt%; CaO = 12.1–12.9 wt%; Na 2 O = 1.11–1.91 wt%). Estimated crystallization temperatures for the interstitial amphibole grains and amphibole inclusions range from 706 to 974 °C, with the higher values in the latter. A comparison of amphibole inclusions in chromite with interstitial grains provides direct evidence for the involvement of water in chromitite formation and the presence of hydrous melt/fluid metasomatism in the peridotites during initial subduction of Neo-Tethyan oceanic lithosphere. The hydrous melts/fluids were released from the chromitites after being collected on chromite surfaces during crystallization. Different fluid/wall rock ratios are thought to have controlled the crystallization and composition of the Lycian amphibole and the extent of modification of the chromite and pyroxene grains in the peridotites. Considering the wide distribution of podiform chromitites in this ophiolite, the link between chromitite formation and melt/fluid metasomatism defined in our study may be applicable to other ophiolites worldwide.

Ferro-papikeite, ideally NaFe 2 2+ (Fe 3 2+ Al 2 )(Si 5 Al 3 )O 22 (OH) 2 , is a new mineral of the amphibole supergroup from the Filipstad Municipality, Värmland County, Central Sweden, where it occurs in a medium-grade felsic metavolcanic rock. Ferro-papikeite is pale brown with a translucent luster, has a colorless to very pale-brown streak, and shows no fluorescence under long-wave or short-wave ultraviolet light. Grains are subhedral, 0.4–3.0 mm in size, and show well-developed {210} cleavage. It has a Mohs hardness of ~6 and is brittle with a splintery fracture, has the characteristic perfect {210} cleavage of orthorhombic amphiboles, intersecting at ~56°, and the calculated density is 3.488 g/cm 3 . In transmitted plane-polarized light, ferro-papikeite is moderately pleochroic X = very pale brown, Y = Z = honey brown; X < Y = Z. Ferro-papikeite is biaxial (+), α = 1.674(2), β = 1.692(2), γ = 1.716(2), 2 V meas = 86.2(9) and 2 V calc = 88.3°, dispersion is r < v, weak. The orientation is: X || a, Y || b, Z || c. Ferro-papikeite is orthorhombic, space group Pnma , a = 18.628(4), b = 17.888(4), c = 5.3035(11) Å, V = 1767.2(6) Å 3 , Z = 4. The strongest ten X‑ray diffraction lines in the powder pattern are [ d in Å( I ) ( hkl )]: 8.255(100)(210), 3.223(39)(440), 3.057(68)(610), 2.824(28)(251), 2.674(41)(351), 2.572(56) (161,621), 2.549(38)(202), 2.501(50)(261,451), 2.158(25)(502), and 1.991(31)(661). Chemical analysis by electron microprobe gave SiO 2 36.50, Al 2 O 3 22.24, TiO 2 0.09, FeO 31.54, MnO 0.65, MgO 5.48, CaO 0.08, Na 2 O 2.35, F 0.22, H 2 O calc 1.85, O=F –0.09, sum 100.91 wt%. The formula unit, calculated on the basis of 24 (O+OH+F) with (OH) = 2 apfu and Fe 3+ = 0.13 apfu (determined from the < M 2–O> distance) is A (Na 0.70 Ca 0.01 ) B+C (Mg 1.25 Fe 2 3.90 + Mn 2 0.08 + Al 1.62 Fe 3 0.13 + Ti 4 0.01 + ) Σ6.99 T (Si 5.60 Al 2.40 ) Σ8 O 22 (OH 1.89 F 0.11 ) 2 . The crystal structure of ferro-papikeite was refined to an R-index of 3.60% using 2335 unique observed reflections collected with Mo K a X-radiation. [4] Al 3+ is ordered over the four T sites as follows: T 1B > T 1A > T 2B >> T 2a, [6] Al 3+ is completely ordered at M 2, and Fe 2+ is strongly ordered at M 4. The A site is split with Na + strongly ordered at A 1. End-member ferro-papikeite is related to end-member gedrite, □Mg 2 (Mg 3 Al 2 )(Si 6 Al 2 )O 22 (OH) 2 , by the substitutions Na + → □, Fe 2+ → Mg, and Al 3+ → Si 4+ . The description of ferro-papikeite as a new species further emphasizes the compositional similarities between the monoclinic calcium amphiboles and the orthorhombic magnesium-iron-manganese amphiboles.

We report for the first time the formation of a HP-PdF 2 -type FeCl 2 phase (space group Pa 3), through high pressure-temperature ( P-T ) reactions in the hydrous systems (Mg 0.6 Fe 0.4 )SiO 3 –H 2 O–NaCl and FeO 2 H– NaCl in a laser-heated diamond-anvil cell up to 108 GPa and 2000 K. Applying single-crystal X‑ray difraction (XRD) analysis to individual submicrometer-sized grains, we have successfully determined the crystal structure of the as-synthesized FeCl 2 phase, in agreement with our theoretical structure search results. In situ high P-T XRD data revealed the substitution of Cl for OH(O) in such a cubic Pa 3 structure, demonstrating that this topology is a potential host for both H and Cl in the deep Earth. The chemical analysis of the recovered sample showed that the post-perovskite phase contains considerable amounts of Na 2 O and Fe 2 O 3 . The coexistence of the cubic FeCl 2 phase and post-perovskite suggests that the lowermost mantle could be a potential reservoir of Cl. The possible presence of volatiles such as H and Cl in the deep lower mantle would impact the composition and iron valence state of the post-perovskite phase.

In this issue In this series of New Mineral Names, the theme is alteration products ranging from supergene mineralization to ambient pressure and temperature bat guano–rock interactions. The minerals highlighted here are: arrheniusite-(Ce), erssonite, krupičkaite, priscillagrewite-(Y), seaborgite, thalliomelane, thebaite, and uranoclite.