ALBERT

Description: To use structural hydroxyl (OH) concentrations preserved in volcanic phenocrysts to constrain magmatic water contents prior to eruption, it is first necessary to understand the diffusive behavior of hydrogen in plagioclase. In this study, diffusion coefficients for a natural OH-bearing plagioclase feldspar (Ab 66 An 31 Or 3 ) are determined from a series of integrated loss heating experiments performed at 800–1000 °C and 1 atm under air, nitrogen gas, and a CO 2 -H 2 mixture at the FMQ oxygen buffer. Hydrogen diffusion is found to be isotropic within analytical error. Using a one-dimensional diffusive loss model for an infinite slab, the diffusion behavior for hydrogen in plagioclase is described by the diffusion parameters log D 0 = –1.62 ± 0.31 (m 2 /s) and E a = 266 ± 77 kJ/mol, and log D 0 = –0.97 ± 0.35 (m 2 /s) and E a = 278 ± 90 kJ/mol for experiments only conducted under nitrogen gas. Nearly complete (83–97%) loss of OH from the andesine was achieved in 900 and 1000 °C heating series, except for the 900 °C FMQ buffer experiment in which only 64% of the total OH was lost after 21.6 days of cumulative heating. The diffusion rates of hydrogen in the plagioclase after 800–1000 °C are similar to interpolated diffusion rates for sodium diffusion in An 30 feldspar, implying that Na + and H + both diffuse via Frenkel defects involving the large cation sites and interstitial ions. The diffusion coefficient ( D ) values for hydrogen in plagioclase are lower than most reported diffusion data for hydrogen in nominally anhydrous minerals, and are most similar to D reported for pure forsterite, unaffected by iron redox reactions. Based on the hydrogen diffusion parameters in this study, a 1 mm spherical plagioclase phenocryst experiencing dehydration under lowered water activity during ascent and eruption at 800 °C retains 50% of its initial OH concentration after 34 days. At 900 and 1000 °C, a 1 mm phenocryst retains 50% of its initial OH concentration after only 1.3 days and 0.25 day, respectively. OH concentrations in plagioclase are therefore most indicative of magmatic water contents during the latest stages of ascent and eruption.

Description: Darrellhenryite, Na(LiAl 2 )Al 6 (BO 3 ) 3 Si 6 O 18 (OH) 3 O, a new member of the tourmaline supergroup (related to the alkali-subgroup 4), is a new Li-bearing tourmaline species, which is closely related to elbaite through the substitution Y Al W 0.5 O 1 Y Li W –0.5 (OH) –1 . It occurs in a complex (Li-bearing) petalite-subtype pegmatite with common lepidolite , Li-bearing tourmalines, and amblygonite at Nová Ves near Cesky Krumlov, southern Bohemia, Moldanubian Zone, Czech Republic. This zoned pegmatite dike cross-cuts a serpentinite body enclosed in leucocratic granulites. Pink darrellhenryite forms columnar crystals (sometimes in parallel arrangement) up to 3 cm long and up 2 cm thick, associated with albite (var. cleavelandite ), minor quartz, K-feldspar, petalite, rare polylithionite, and locally rare pollucite. The optical properties and the single-crystal structure study ( R 1 = 0.019) of darrellhenryite are consistent with trigonal symmetry, = 1.636(2), = 1.619(2), birefringence: 0.017, space group R 3 m , a = 15.809(2), c = 7.089(1) Å, V = 1534.4(4) Å 3 , and Z = 3. The chemical analysis, in combination with the results from the single-crystal structure refinement, gives the formula X (Na 0.58 Ca 0.01 0.41 ) 1.00 Y (Li 1.05 Al 1.95 ) 3.00 Z Al 6 (BO 3 ) 3 T (Si 6 O 18 ) V (OH) 3 W (O 0.66 F 0.34 ) 1.00 , which can be simplified to an ideal formula of Na(LiAl 2 )Al 6 (BO 3 ) 3 Si 6 O 18 (OH) 3 O. The strongest lines of the powder pattern [ d in Å ( I , hkl )] are 4.180 (39, 211), 3.952 (54, 220), 3.431 (73, 012), 2.925 (100, 122), 2.555 (90, 051), 2.326 (42, 511), 2.029 (42, 223), 2.021 (42, 152), 1.901 (50, 342), 1.643 (49, 603). The density is D meas = 3.03(3) g/cm 3 , D calc = 3.038 g/cm 3 . Darrellhenryite is considered to have crystallized in Li- and B-rich but F-moderate environments in complex pegmatites; no influence of higher activity of O on the darrellhenryite formation is implied from its mineral assemblage. The name is for Darrell J. Henry, Professor of Geology at the Louisiana State University, Baton Rouge, U.S.A., an expert on the mineralogy, petrology, crystal chemistry, and nomenclature of tourmaline-supergroup minerals.

Description: Recent interest in hydrogen incorporation in feldspars has been driven by the potential of this common mineral species to record magmatic water contents. Accurate measurement of H concentrations in feldspars by Fourier transform infrared (FTIR) spectroscopy is hampered by the need to collect polarized spectra in three mutually perpendicular directions, which can be impractical for crystals characterized by small dimensions, polysynthetic twinning, and/or chemical zoning. SIMS is an attractive alternative to FTIR, offering high spatial resolution, high precision, and the feasibility of attaining low detection limits. In this study we compare FTIR and SIMS data for 19 feldspars, including plagioclase, anorthoclase, sanidine, microcline, and orthoclase. We present adjustments to previously published FTIR data on some of these samples. Our new SIMS and FTIR data are well correlated and we demonstrate the feasibility of quantitatively measuring H concentrations as low as 1–2 ppmw H 2 O using SIMS. Combination of the new data together with re-evaluation of the NMR calibration of Johnson and Rossman (2003) indicates that the IR absorption coefficients for hydrous species in feldspar increase with decreasing frequency of their O-H absorptions, in accord with theory. We derive new molar integral IR absorption coefficients (I) for feldspars with the following hydrous species as defined by Johnson and Rossman (2003) : Type I and II H 2 O (microcline and orthoclase): I = 120 470 ± 11 360 L·mol –1 H 2 O cm –2 Type IIb OH (sanidine): I = 150 000 ± 15 000 L·mol –1 H 2 O cm –2 Type IIa OH (plagioclase and anorthoclase): I = 202 600 ± 20 260 L·mol –1 H 2 O cm –2 These absorption coefficients depend on critical assumptions with regards to SIMS matrix effects. If accurate, one important implication is that the H concentrations of plagioclase crystals estimated in the literature are too high by up to a factor of two, requiring revision of previously estimated plagioclase-melt H partitioning coefficients.

Description: Yttriaite-(Y), ideally Y2O3, is a new mineral (IMA2010-039) from the alluvial deposits of the Bol'shaya Pol'ya River, Subpolar Urals, Russia. The new mineral occurs as isolated crystals, typically cubo-octahedra

Description: Krotite, CaAl2O4, occurs as the dominant phase in an unusual Ca-,Al-rich refractory inclusion from the NWA 1934 CV3 carbonaceous chondrite. Krotite occupies the central and mantle portions of the inclusion along with minor perovskite, gehlenite, hercynite, and Cl-bearing mayenite, and trace hexamolybdenum. A layered rim surrounds the krotite-bearing regions, consisting from inside to outside of grossite, mixed hibonite, and spinel, then gehlenite with an outermost layer composed of Al-rich diopside. Krotite was identified by XRD, SEM-EBSD, micro-Raman, and electron microprobe. The mean chemical composition determined by electron microprobe analysis of krotite is (wt%) Al2O3 63.50, CaO 35.73, sum 99.23, with an empirical formula calculated on the basis of 4 O atoms of Ca1.02Al1.99O4. Single-crystal XRD reveals that krotite is monoclinic, P21/n; a = 8.6996(3), b = 8.0994(3), c = 15.217(1) A, {beta} = 90.188(6), and Z = 12. It has a stuffed tridymite structure, which was refined from single-crystal data to R1 = 0.0161 for 1014 Fo 〉 4{sigma}F reflections. Krotite is colorless and transparent with a vitreous luster and white streak. Mohs hardness is ~6[1/2]. The mineral is brittle, with a conchoidal fracture. The calculated density is 2.94 g/cm3. Krotite is biaxial (-), {alpha} = 1.608(2), {beta} = 1.629(2), {gamma} = 1.635(2) (white light), 2Vmeas = 54.4(5){degrees}, and 2Vcalc = 55.6{degrees}. No dispersion was observed. The optical orientation is X = b; Y {approx} a; Z {approx} c. Pleochroism is colorless to very pale gray, X 〉 Y = Z. Krotite is a low-pressure CaAl2O4 mineral, likely formed by condensation or crystallization from a melt in the solar nebula. This is the first reported occurrence of krotite in nature and it is one of the earliest minerals formed in the solar system.

Description: Synthetic Al- and B-rich tourmaline crystals described by London (2011) were characterized further by SIMS and new EMP analyses. These tourmalines are the first synthetic B-rich olenites characterized by single-crystal X-ray diffraction, because they are significantly larger than synthetic samples produced in the past. The average final formulas are X (Na 0.7 0.3 ) Y (Al 2.5 Li 0.4 Fe 2+ 0.1 ) Z Al 6 (BO 3 ) 3 [Si 5.2 B 0.5 Al 0.3 O 18 ] V [(OH) 2.9 O 0.1 ] W [O 0.9 (OH) 0.1 ], with a = 15.765(1), c = 7.083(1) Å, X (Na 0.7 0.3 ) Y (Al 2.5 Li 0.5 ) Z Al 6 (BO 3 ) 3 [Si 4.8 B 0.9 Al 0.3 O 18 ] V (OH) 3 W [(OH) 0.5 O 0.5 ], with a = 15.746(1), c = 7.075(1) Å, and X (Na 0.6 Ca 0.1 0.3 ) Y (Al 2.3 Li 0.5 Fe 0.2 ) Z Al 6 (BO 3 ) 3 [Si 4.7 B 1.2 Al 0.2 O 18 ] V (OH) 3 W [(OH) 0.9 O 0.1 ], with a = 15.723(1), c = 7.068(1) Å. The small 〈T-O〉 distances, down to 1.599 Å, reflect relatively high amounts of [4] B (up to ~1.2 apfu; refinements with R = ~2%). All these samples also contain significant amounts of [4] Al (~0.2 apfu). A pronounced negative correlation ( r 2 = 1.00; only three data points) between temperature during crystal growth (at a constant pressure) and [4] B (from refinement) in these synthetic olenites was found.

Description: Buseckite (IMA 2011-070), (Fe,Zn,Mn)S, is the Fe-dominant analog of wurtzite, a new member of the wurtzite group discovered in Zakłodzie, and an ungrouped enstatite-rich achondrite. The type material occurs as single-crystal grains (4–20 μm in size) in contact with two or more of enstatite, plagioclase, troilite, tridymite, quartz, and sinoite. Low-Ni iron, martensitic iron, schreibersite, keilite, cristobalite, and graphite, which are also present in the type sample, are not observed to be in contact with buseckite. Buseckite is black under diffuse illumination and nearly opaque grayish brown in transmitted light. The mean chemical composition of buseckite, as determined by electron microprobe analysis of the type material, is (wt%) S 35.84, Fe 28.68, Zn 23.54, Mn 10.04, Mg 1.18, sum 99.28, leading to an empirical formula calculated on the basis of 2 atoms of (Fe0.46Zn0.32Mn0.16Mg0.04)∑0.99S1.01. Electron backscatter diffraction patterns of buseckite are a good match to that of synthetic (Zn0.558Fe0.442)S with the P63mc structure, showing a = 3.8357, c = 6.3002 Å, V = 80.27 Å3, and Z = 2. Buseckite is likely derived from the breakdown of high-temperature pyrrhotite to form troilite and buseckite following the solidification of sulfide-rich liquids produced during impact melting of an enstatite-rich rock.

Description: Panguite (IMA 2010-057), (Ti4+,Sc,Al,Mg,Zr,Ca)1.8O3, is a new titania, occurring as fine-grained crystals with Ti-rich davisite in an ultra-refractory inclusion within an amoeboid olivine inclusion from the Allende CV3 carbonaceous chondrite. The phase was characterized by SEM, EBSD, synchrotron micro-diffraction, micro-Raman spectroscopy, and EPMA. The mean chemical composition of the type panguite is (wt%) TiO2 47.97, ZrO2 14.61, Sc2O3 10.67, Al2O3 7.58, MgO 5.54, Y2O3 5.38, CaO 3.34, SiO2 1.89, FeO 1.81, V2O3 0.95, Cr2O3 0.54, HfO2 0.28, sum 100.56 with a corresponding empirical formula calculated on the basis of 3 O atoms of [(Ti0.79Zr0.16Si0.04)4+∑0.99(Sc0.20Al0.20Y0.06V0.02Cr0.01)3+∑0.49 (Mg0.18Ca0.08Fe0.03)2+∑0.29]∑1.77O3. Synchrotron micro-Laue diffraction (i.e., an energy scan by a high-flux X-ray monochromatic beam and white beam diffraction) on one type domain at sub-micrometer resolution revealed that panguite is an orthorhombic mineral in space group Pbca. The structure is a subgroup of the Ia3 bixbyite-type. The cell parameters are a = 9.781(1), b = 9.778(2), and c = 9.815(1) Å, yielding V = 938.7(1) Å3, Z = 16, and a calculated density of 3.746 g/cm3. Panguite is not only a new mineral, but also a new titania material, likely formed by condensation. It is one of the oldest minerals in the solar system.

Description: We measured hydrogen concentrations in 12 olivines using secondary ion mass spectrometry (SIMS and NanoSIMS), cross-calibrated against Fourier transform infrared (FTIR) spectroscopy and nuclear reaction analysis (NRA). Five of these samples are routinely used for calibration in other laboratories. We assess the suitability of these olivines as standards based on over 300 SIMS analyses, comprising 22 separate calibrations. Seven olivines with 0-125 ppm H2O give highly reproducible results; in contrast to previous studies, the data are fit to well-constrained calibration lines with high correlation coefficients (r2 = 0.98-1). However, four kimberlitic megacrysts with 140-245 ppm H2O sometimes yield 16O1H/30Si ratios that have low internal precision and can vary by up to a factor of two even in sequential analyses. A possible cause of this behavior is the presence of sub-microscopic inclusions of hydrous minerals, such as serpentine. In most cases, however, we link the anomalous results to the presence of sub-micrometer to micrometer-scale pores (as small as 100 nm), which we imaged using SEM and NanoSIMS. These pores are interpreted to be fluid inclusions containing liquid H2O, other volatiles (including fluorine), and/or hydrous phase precipitates. Ionization of the contents of the pores contributes variably to the measured 16O1H, resulting in analyses with erratic depth profiles and corresponding high uncertainties (up to 16%, 2{sigma}mean). After filtering of these analyses using a simple criterion based on the error predicted by Poisson counting statistics, all the data fit well together. Our results imply that the Bell et al. (2003) calibration can be applied accurately to all olivines with IR bands from ~3400-3700 cm-1, without the need for band-specific IR absorption coefficients.

Description: Murchisite (IMA 2010-003), Cr5S6, is a new chromium sulfide mineral, discovered in the Murchison CM2 meteorite. The type material occurs as one subhedral crystal (1.3 x 4 m in size) in contact with low-Ni iron ("kamacite"), martensitic iron, schreibersite, and a Ca-,Al-rich glass, all of which are included in an isolated forsteritic olivine grain in the meteorite's matrix. The mean chemical composition determined by electron microprobe analysis of the type material is (wt%) Cr 53.32, S 42.87, V 1.44, Fe 1.14, P 0.10, Ni 0.10, sum 98.97. The empirical formula calculated on the basis of 6 S atoms is (Cr4.60V0.13Fe0.09Ni0.01){sum}4.83(S6.00P0.01){sum}6.01. Murchisite was also identified in another isolated olivine grain from the same meteorite. These crystals are subhedral to round in shape, 300 nm to 1 m in size, and occur in association with tochilinite and serpentine, within which it is included, chromite, and eskolaite. Its electron backscatter diffraction patterns are an excellent match to that of synthetic Cr5S6 with the P[IMG]f1.gif" ALT="3" BORDER="0"〉1c structure, showing a = 5.982, c = 11.509 A, V = 356.67 A3, and Z = 2, based on previously published data from synthetic material. Murchisite is named for the locality (the Murchison meteorite). It is a low-temperature phase (~327 {degrees}C in the Cr-S system), probably formed from higher temperature Cr1-xS exsolved or expelled from a Cr-,S-bearing, metal-rich spherule included in forsteritic olivine grains that were probably derived from chondrule fragments. The formation of this phase reflects sulfur fugacities intermediate between those that would have led to troilite and those that would have led to no sulfide at all. The high-temperature Cr1-xS phase equilibrated with coexisting alloys to ~600 {degrees}C. Murchisite formed from this precursor at low temperatures (