Barbara P. Nash

MPI‐DING reference glasses for in situ microanalysis: New reference values for element concentrations and isotope ratios

We present new analytical data of major and trace elements for the geological MPI-DING glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, BM90/21-G, T1-G, and ATHO-G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA-ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties (at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive (isotope dilution) and comparative bulk (e.g., INAA, ICPMS, SSMS) and microanalytical (e.g., LA-ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high-precision bulk techniques, such as TIMS and MC-ICPMS. In addition, LA-ICPMS and SIMS isotope data of B, Li, and Pb are presented.

Explosive silicic volcanism of the Yellowstone hotspot: The ash fall tuff record

Unaltered silicic ash fall tuffs are abundant in Neogene sedimentary basins of the western U.S. and constitute an important record of explosive silicic volcanism in this region. In particular, ash fall tuffs from silicic volcanic centers along the Yellowstone hotspot track are common in these basins and provide a detailed record of explosive volcanism along the hotspot track. The available hotspot ash fall tuff record commences at ca. 16 Ma, shortly after the initiation of hotspot silicic volcanism at ca. 16.5 Ma, and continues through the most recent explosive eruptions in the late Pleistocene. Post–16 Ma hotspot silicic volcanism has been dominated by eruption of metaluminous ash flow tuffs and rhyolites, and ash fall tuffs produced by these eruptions dominate the Yellowstone hotspot ash fall tuff record. Evaluation of a well-dated composite sequence of 142 of these tuffs reveals systematic variation in magma composition, magma temperature, eruption frequency, and, possibly, volumetric discharge as the hotspot migrated eastward from the western edge of the North America craton to its current location in the Yellowstone Plateau. On the basis of these variations, three primary stages of metaluminous rhyolite magmatism (M stages) are recognized: M1 (16.0–15.2 Ma), M2 (15.2–7.5 Ma), and M3 (7.5–0 Ma). Each of these stages is marked by distinctive magma compositions, eruption frequencies, and magma temperature ranges and trends, with an overall decline in average eruption frequency and magma temperature from stage to stage. The partitioning of explosive hotspot volcanism into stages likely reflects variation in the style and intensity of the interaction between the mantle anomaly powering the hotspot magmatic systems and a spatially and temporally heterogeneous lithosphere along the hotspot track. Although the ash fall tuff record does not provide definitive constraints on the nature of these variable interactions, correlations between changes in eruption frequency, ash fall tuff discharge, and magma temperature point to variable input of mantle basalt into hotspot crustal magmatic systems as a first order control on intensity of explosive volcanism. As future studies reveal more about the processes controlling the variations in hotspot silicic volcanism, a fuller understanding of both the nature of silicic magmatism and the nature of the Yellowstone hotspot should emerge.

Geochemical Discrimination of Five Pleistocene Lava-Dam Outburst- Flood Deposits, Western Grand Canyon, Arizona

Pleistocene basaltic lava dams and outburst‐flood deposits in the western Grand Canyon, Arizona, have been correlated by means of cosmogenic 3He (3Hec) ages and concentrations of SiO2, Na2O, K2O, and rare earth elements. These data indicate that basalt clasts and vitroclasts in a given outburst‐flood deposit came from a common source, a lava dam. With these data, it is possible to distinguish individual dam‐flood events and improve our understanding of the interrelations of volcanism and river processes. At least five lava dams on the Colorado River failed catastrophically between 100 and 525 ka; subsequent outburst floods emplaced basalt‐rich deposits preserved on benches as high as 200 m above the current river and up to 53 km downstream of dam sites. Chemical data also distinguishes individual lava flows that were collectively mapped in the past as large long‐lasting dam complexes. These chemical data, in combination with age constraints, increase our ability to correlate lava dams and outburst‐flood deposits and increase our understanding of the longevity of lava dams. Bases of correlated lava dams and flood deposits approximate the elevation of the ancestral river during each flood event. Water surface profiles are reconstructed and can be used in future hydraulic models to estimate the magnitude of these large‐scale floods.

Diagenetic characteristics of the Jurassic Navajo Sandstone in the Covenant oil field, central Utah thrust belt

The Jurassic Navajo Sandstone core in the Covenant field includes eolian dune interbedded with carbonate playa lake and fluvial interdune facies. Dune facies samples are bleached but not depleted in iron; bleached dune facies outcrop samples are depleted in iron. Bleached dune facies in the core samples contains ferroan dolomite, quartz overgrowths that do not completely fill pore spaces, grain-coating and pore-filling illite, coarse-grained gray hematite, kaolinite, and trace pyrite. Reddish brown interdune facies are typically very fine-grained sandstone and siltstone and contain dolomite and ferroan dolomite cement, illite pore-filling, and very fine-grained, red hematite. Diagenetic mineralogy and chemical compositions overlap the mineralogy and compositions of outcrop samples. The carbon and oxygen isotopic composition of dolomite in interdune facies and adjacent dune facies is derived from groundwater discharge modified by evaporation in a playa lake interdune environment, not from interaction with hydrocarbons. The iron in bleached dune facies is incorporated in coarse-grained hematite, ferroan dolomite, and trace pyrite. The bleached diagenetic mineral association of ferroan dolomite-hematite-pyrite with is metastable relative to more reducing conditions produced by petroleum. The reservoir temperature of 188F (87C) is too high for bacterial sulfate reduction and too low for geologically significant thermochemical sulfate reduction accounting for the association of abundant in produced water and trace pyrite in the core.

Neogene Fallout Tuffs from the Yellowstone Hotspot in the Columbia Plateau Region, Oregon, Washington and Idaho, USA

Sedimentary sequences in the Columbia Plateau region of the Pacific Northwest ranging in age from 16–4 Ma contain fallout tuffs whose origins lie in volcanic centers of the Yellowstone hotspot in northwestern Nevada, eastern Oregon and the Snake River Plain in Idaho. Silicic volcanism began in the region contemporaneously with early eruptions of the Columbia River Basalt Group (CRBG), and the abundance of widespread fallout tuffs provides the opportunity to establish a tephrostratigrahic framework for the region. Sedimentary basins with volcaniclastic deposits also contain diverse assemblages of fauna and flora that were preserved during the Mid-Miocene Climatic Optimum, including Sucker Creek, Mascall, Latah, Virgin Valley and Trout Creek. Correlation of ashfall units establish that the lower Bully Creek Formation in eastern Oregon is contemporaneous with the Virgin Valley Formation, the Sucker Creek Formation, Oregon and Idaho, Trout Creek Formation, Oregon, and the Latah Formation in the Clearwater Embayment in Washington and Idaho. In addition, it can be established that the Trout Creek flora are younger than the Mascall and Latah flora. A tentative correlation of a fallout tuff from the Clarkia fossil beds, Idaho, with a pumice bed in the Bully Creek Formation places the remarkably well preserved Clarkia flora assemblage between the Mascall and Trout Creek flora. Large-volume supereruptions that originated between 11.8 and 10.1 Ma from the Bruneau-Jarbidge and Twin Falls volcanic centers of the Yellowstone hotspot in the central Snake River Plain deposited voluminous fallout tuffs in the Ellensberg Formation which forms sedimentary interbeds in the CRBG. These occurrences extend the known distribution of these fallout tuffs 500 km to the northwest of their source in the Snake River Plain. Heretofore, the distal products of these large eruptions had only been recognized to the east of their sources in the High Plains of Nebraska and Kansas.

Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies

The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Member, Crockett Formation, Claiborne Group. Its mineralogy and geochemistry were examined in detail, and verdine facies minerals, predominantly odinite, were identified. Few glauconitic minerals were found in the green pelleted sediments of the MGB. Without detailed mineralogical work, glaucony facies minerals and verdine facies minerals are easily mistaken for one another. Their distinction has value in assessing paleoenvironments. In this study, several analytical techniques were employed to assess the mineralogy. X-ray diffraction of oriented and un-oriented clay samples indicated a clay mixture dominated by 7 and 14Å diffraction peaks. Unit cell calculations from XRD data for MGB pellets match the odinite-1M data base. Electron microprobe analyses (EMPA) from the average of 31 data points from clay pellets accompanied with Mössbauer analyses were used to calculate the structural formula which is that of odinite: Fe3+ 0.89 Mg0.45 Al0.67 Fe2+ 0.30 Ti0.01 Mn0.01) Σ = 2.33 (Si1.77 Al0.23) O5.00 (OH)4.00. QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) data provided mineral maps of quantitative proportions of the constituent clays. The verdine facies is a clay mineral facies associated with shallow marine shelf and lagoonal environments at tropical latitudes with iron influx from nearby runoff. Its depositional environment is well documented in modern nearshore locations. Recognition of verdine facies clays as the dominant constituent of the MGB clay pellets, rather than glaucony facies clays, allows for a more precise assessment of paleoenvironmental conditions.

Canutite, NaMn3[AsO4][AsO3(OH)]2, a new protonated alluaudite-group mineral from the Torrecillas mine, Iquique Province, Chile

Abstract The new mineral canutite (IMA2013-070), NaMn3[AsO4][AsO3(OH)]2, was found at two different locations at the Torrecillas mine, Salar Grande, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with anhydrite, halite, lavendulan, magnesiokoritnigite, pyrite, quartz and scorodite. Canutite is reddish brown in colour. It forms as prisms elongated on [201̅] and exhibiting the forms {010}, {100}, {102}, {201} and {102̅}, or as tablets flattened on {102} and exhibiting the forms {102} and {110}. Crystals are transparent with a vitreous lustre. The mineral has a pale tan streak, Mohs hardness of 2½, brittle tenacity, splintery fracture and two perfect cleavages, on {010} and {101}. The calculated density is 4.112 g cm-3. Optically, canutite is biaxial (+) with α = 1.712(3), β = 1.725(3) and γ = 1.756(3) (measured in white light). The measured 2V is 65.6(4)º, the dispersion is r < v (slight), the optical orientation is Z = b; X ^ a = 18º in obtuse β and pleochroism is imperceptible. The mineral is slowly soluble in cold, dilute HCl. The empirical formula (for tabular crystals from near themineshaft ) , determined from electron - microprobe analyses , is (Na1.05Mn2.64Mg0.34Cu0.14Co0.03)∑4.20As3O12H1.62. Canutite is monoclinic, C2/c, a = 12.3282(4), b = 12.6039(5), c = 6.8814(5) Å, b = 113.480(8)º, V = 980.72(10) Å3 and Z = 4. The eight strongest X-ray powder diffraction lines are [dobs Å (I)(hkl)]: 6.33(34)(020), 4.12(26)(2̅21), 3.608(29)(310,1̅31), 3.296(57)(1̅12), 3.150(28)(002,131), 2.819(42)(400,041,330), 2.740(100)(240,4̅02,112) and 1.5364(31)(multiple). The structure, refined to R1 = 2.33% for 1089 Fo > 4σF reflections, shows canutite to be isostructural with protonated members of the alluaudite group.

Magnesiokoritnigite, Mg(AsO3OH)·H2O, from the Torrecillas mine, Iquique Province, Chile: the Mg-analogue of koritnigite

Abstract The new mineral magnesiokoritnigite (IMA 2013-049), ideally Mg(AsO3OH)·H2O, was found at the Torrecillas mine, Salar Grande, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with anhydrite, chudobaite, halite, lavendulan, quartz and scorodite. Crystals of magnesiokoritnigite are colourless to pale-pink, thin to thick laths up to 2 mm long. Laths are elongated on [001], flattened on {010} and exhibit the forms {010}, {110}, {11̅0}, {101}, {031} and {03̅1}. The crystals also occur in dense deep-pink intergrowths. Crystals are transparent with a vitreous lustre. The mineral has a white streak, Mohs hardness of ~3, brittle tenacity, conchoidal fracture and one perfect cleavage on {101}. The measured and calculated densities are 2.95(3) and 2.935 g cm-3, respectively. Optically, magnesiokoritnigite is biaxial (+) with α = 1.579(1), β = 1.586(1) and γ = 1.620(1) (measured in white light). The measured 2V is 50(2)º and the calculated 2V is 50º. Dispersion is r < v, medium. The optical orientation is Y ≈ b; Z ^ c = 36º in obtuse β (note pseudomonoclinic symmetry). The mineral is non-pleochroic. The empirical formula, determined from electron-microprobe analyses, is (Mg0.94Cu0.03Mn0.02Ca0.01)Σ1.00As0.96O5H3.19. Magnesiokoritnigite is triclinic, P1̅, with a = 7.8702(7), b = 15.8081(6), c = 6.6389(14) Å , α = 90.814(6), β = 96.193(6), γ = 90.094(7)º, V = 821.06(19) Å3 and Z = 8. The eight strongest X-ray powder diffraction lines are [dobs Å (I)(hkl)]: 7.96(100)(020), 4.80(54)(101), 3.791(85)(2̅10,210,1̅3̅1,1̅31), 3.242(56)(01̅2,2̅2̅1,012), 3.157(92)(21̅1,2̅30,230), 3.021(61)(14̅1,141,22̅1,221), 2.798(41)(03̅2,032) and 1.908(43)(multiple). The structure, refined to R1 = 5.74% for 2360 Fo > 4σF reflections, shows magnesiokoritnigite to be isostructural with koritnigite and cobaltkoritnigite.

Camaronesite, [Fe3+(H2O)2(PO3OH)]2(SO4)·1–2H2O, a new phosphate-sulfate from the Camarones Valley, Chile, structurally related to taranakite

Abstract Camaronesite (IMA 2012-094), [Fe3+(H2O)2(PO3OH)]2(SO4)·1−2H2O, is a new mineral from near the village of Cuya in the Camarones Valley, Arica Province, Chile. The mineral is a low-temperature, secondary mineral occurring in a sulfate assemblage with anhydrite, botryogen, chalcanthite, copiapite, halotrichite, hexahydrite, hydroniumjarosite, pyrite, römerite, rozenite and szomolnokite. Lavendercoloured crystals up to several mm across form dense intergrowths. More rarely crystals occur as drusy aggregates of tablets up to 0.5 mm in diameter and 0.02 mm thick. Tablets are flattened on {001} and exhibit the forms {001}, {104}, {015} and {018}. The mineral is transparent with white streak and vitreous lustre. The Mohs hardness is 2 ½, the tenacity is brittle and the fracture is irregular, conchoidal and stepped. Camaronesite has one perfect cleavage on {001}. The measured and calculated densities are 2.43(1) and 2.383 g/cm3, respectively. The mineral is optically uniaxial (+) with ω = 1.612(1) and Ɛ = 1.621(1) (white light). The pleochroism is O (pale lavender) > E (colourless). Electron-microprobe analyses provided Fe2O3 31.84, P2O5 29.22, SO3 15.74, H2O 23.94 (based on O analyses), total 100.74 wt.%. The empirical formula (based on 2 P a.p.f.u.) is: Fe1.94(PO3OH)2(S0.96O4)(H2O)4·1.46H2O. The mineral is slowly soluble in concentrated HCl and extremely slowly soluble in concentrated H2SO4. Camaronesite is trigonal, R32, with cell parameters: a = 9.0833(5), c = 42.944(3) Å , V = 3068.5(3) Å3 and Z = 9. The eight strongest lines in the X-ray powder diffraction pattern are [dobs Å (I)(hkl)]: 7.74(45)(101), 7.415(100)(012), 4.545(72)(110), 4.426(26)(018), 3.862(32)(021,202,116), 3.298(93)(027,119), 3.179(25)(208) and 2.818(25)(1·1·12,125). In the structure of camaronesite (R1 = 2.28% for 1138 Fo > 4σF), three types of Fe octahedra are linked by corner sharing with (PO3OH) tetrahedra to form polyhedral layers perpendicular to c with composition [Fe3+(H2O)2(PO3OH)]. Two such layers are joined through SO4 tetrahedra (in two half-occupied orientations) to form thick slabs of composition [Fe3+(H2O)2(PO3OH)]2(SO4). Between the slabs are partially occupied H2O groups. The only linkages between the slabs are hydrogen bonds. The most distinctive component in the structure consists of two Fe octahedra linked to one another by three PO4 tetrahedra yielding an [Fe2(PO4)3] unit. This unit is also the key component in the sodium super-ionic conductor (NASICON) structure and has been referred to as the lantern unit. The polyhedral layers in the structure of camaronesite are similar to those in the structure of taranakite. The Raman spectrum exhibits peaks consistent with sulfate, phosphate, water and OH groups.

Kegginite, Pb3Ca3[AsV12O40(VO)]·20H2O, a new mineral with a novel ε-isomer of the Keggin anion

Abstract Kegginite, Pb3Ca3[AsV12O40(VO)]·20H2O, is a new mineral species from the Packrat mine, near Gateway, Mesa County, Colorado, U.S.A. It is a secondary mineral found on asphaltum in a montroseite- and corvusite-bearing sandstone. Other secondary minerals found in close association with kegginite are ansermetite, gypsum, mesaite, and sherwoodite. Crystals of kegginite are orange-red simple hexagonal tablets. The streak is pinkish-orange, the luster is vitreous, the Mohs hardness is about 2, the tenacity is brittle, fracture is irregular, cleavage is good on {001}, and the calculated density is 2.69 g/cm3. Kegginite is optically uniaxial (–) with pleochroism: O orange-red and E red-orange; E < O. Electron microprobe analyses yielded the empirical formula Pb2.98Ca2.39Mg0.56V13.05As0.95O61H40.15. Kegginite is trigonal, P3¯,