Secondary Alteration Phases Research Articles

Naalasite, NaAl(AsO3OH)2⋅H2O, the Al analogue of nafeasite from the Torrecillas mine, Iquique Province, Chile

AbstractThe new mineral naalasite (IMA2023–027), NaAl(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, juansilvaite, magnesiokoritnigite and a lavendulan-like phase. Naalasite occurs in tightly intergrown aggregates and druses of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~3½. The density is 3.19(2) g⋅cm–3. Optically, naalasite is uniaxial (+), with ω = 1.630(3) and ɛ = 1.660(3) (white light). The empirical formula (based on 9 O apfu) is Na0.92Al0.61Fe3+0.39As2O9H4.07. Naalasite is trigonal, space group R32, with cell parameters: a = 8.494(4), c = 26.430(13) Å, V = 1651.5(4) Å3 and Z = 9. The structure, refined to R1 = 3.78% for 641 I > 2σI reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and AlO6 octahedra. The structure is topologically equivalent to that of nafeasite and can be regarded as its Al analogue, even though nafeasite is monoclinic with space group C2.

Cortesognoite, CaV2Si2O7(OH)2·H2O, a New Mineral from the Molinello Manganese Mine, Graveglia Valley, Italy

Cortesognoite (IMA 2014-029), CaV2Si2O7(OH)2·H2O, is a new vanadium silicate mineral that occurs within V-bearing lawsonite in association with vanadiocarpholite, chalcocite, quartz, minor poppiite, roscoelite, vanadomalayaite and volborthite in a silicified wood hosted in Mn-ore-bearing metacherts from the Molinello manganese mine in the Graveglia Valley, Northern Apennines, Liguria, Italy. The mean chemical composition of type cortesognoite by electron probe microanalysis is (wt%) SiO2 34.33, V2O3 31.38, CaO 15.80, Al2O3 7.69, MnO 0.14, FeO 0.09, MgO 0.06, TiO2 0.02 and H2O 10.29, totaling 99.80, giving rise to an empirical formula of (Ca0.99Mn0.01)(V1.47Al0.53Mg0.01)Si2.00O7(OH)2·H2O. The end-member formula is CaV2Si2O7(OH)2·H2O. Cortesognoite has the Cmcm lawsonite structure with a = 5.85(1) Å, b = 8.79(1) Å, c = 13.13(1) Å, V = 675(1) Å3 and Z = 4 as revealed by electron back-scatter diffraction. The calculated density using the measured composition is 3.44 g/cm3. Cortesognoite is a secondary alteration phase, formed with V-bearing lawsonite by multi-stage hydrothermal processes that occurred in the silicified fossil wood. The mineral name is in honor of Luciano Cortesogno, professor of petrography at University of Genova, Italy.

Alumolukrahnite, CaCu2+Al(AsO4)2(OH)(H2O), the aluminium analogue of lukrahnite from the Jote mine, Copiapó Province, Chile

AbstractThe new mineral alumolukrahnite (IMA2022–059), CaCu2+Al(AsO4)2(OH)(H2O), was found at the Jote mine, Copiapó Province, Chile, where it is a secondary alteration phase associated with conichalcite, coronadite, gypsum, olivenite, pharmacosiderite, rruffite and scorodite. Alumolukrahnite occurs as crude diamond-shaped tablets up to ~0.1 mm, intergrown in crude spherical aggregates. Crystals are apple green and transparent to translucent, with vitreous lustre and a white streak. The Mohs hardness is 3½. The mineral is brittle with irregular fracture and no cleavage. The calculated density is 4.094 g cm–3. Optically, alumolukrahnite is biaxial (+) with α = 1.73(1), β = 1.74(1) and γ = 1.76(1) (white light). The empirical formula, determined from electron microprobe analyses, is Ca1.01(Cu0.92Zn0.13)Σ1.05(Al0.96Fe0.01)Σ0.97(As0.985O4)2(OH)0.88(H2O)1.12. Alumolukrahnite is triclinic, P$\bar{1}$, a = 5.343(5), b = 5.501(5), c = 7.329(5) Å, α = 67.72(2), β = 69.06(2), γ = 69.42(2)°, V = 180.3(3) Å3 and Z = 1. Alumolukrahnite is a member of the tsumcorite group and is the Al analogue of lukrahnite.

Detection of incipient aqueous alteration in carbonaceous chondrites

We discuss if the detection of aqueous alteration depends on the techniques that are used. We apply different methods to estimate the extent of aqueous alteration on four ungrouped carbonaceous chondrites showing limited aqueous alteration and thermal metamorphism: Chwichiya 002, El Médano (EM) 200, Northwest Africa (NWA) 12957 and NWA 11750, classified as C3 or C3.00-ung. The aim is to propose a reliable methodology to identify the most primitive chondrites. Chwichiya 002, NWA 11750 and NWA 12957 display very primitive matrices and could be amongst the most primitive chondrites currently known, similar to the least altered lithologies of the CM chondrites Paris (CM2.9) and Asuka (A) 12085 (CM2.8), A 12236 (CM2.9) and A 12169 (CM3.0). The structure of organic matter and Cr2O3 in ferroan olivines show that the four meteorites have been less heated than the least metamorphosed standard/reference type 3 chondrite, Semarkona (LL3.00), with Chwichiya 002, NWA 12957 and NWA 11750 similar to the CO3.0 s, Acfer 094 (C2-ung) and Paris meteorites. Chwichiya 002 and NWA 12957 show similar alteration phases and degree of alteration, with high abundances of amorphous material with embedded metal and sulfide, resembling Glass with Embedded Metal and Sulfide (GEMS)-like materials, and tochilinite-cronstedtite intergrowths (TCIs) as the major alteration phases. The matrix in NWA 11750 contains aggregates of nanoscale olivine crystals and abundant carbonates, observed as micrometer-sized carbonate veins surrounding chondrules, and as nanoscale carbonates mixed with the fine-grained materials. It also contains abundant grains of metal and a low abundance of phyllosilicates. El Medano 200 shows a high abundance of magnetite (∼10 vol%), nanoscale phyllosilicates, troilite, and organic matter. The variability of the secondary alteration phases in the meteorites suggests different alteration mechanisms, likely depending on both the starting composition of the meteorites and the composition of the fluids of alteration.Scanning and transmission electron microscopy (SEM and TEM) allow the identification of primitive phases and the composition and spatial distribution of the secondary phases. X-ray diffraction (XRD) can detect alteration products, including some amorphous phases, although this is limited by the small coherence domains of small TCIs and other phyllosilicates. Transmission infrared (IR) spectroscopy can detect phyllosilicate and carbonate, but is ineffective for the detection of amorphous phases, metal, or sulfide. Both matrix defocused electron microprobe analyses (EMPA) and thermogravimetric analysis (TGA) allow detection of hydrated minerals, such as phyllosilicates and carbonates, but are strongly influenced by the presence of organic matter and do not reflect the overall alteration state of a meteorite. We conclude that the assessment of the primitivity of a chondrite is highly technique dependent. We propose a combination of XRD and the Cr2O3 in ferroan olivines or Raman spectroscopy for a rapid characterization of the alteration state of a chondrite and the detection of the most primitive meteorites. Finally, the combination of XRD and TEM allows for the detection of all primary and secondary phases and represents an ideal methodology for the characterization and detailed study of primitive chondrites and the different types of incipient aqueous alteration.

Nafeasite, NaFe3+(AsO3OH)2⋅H2O, a new framework arsenate from the Torrecillas mine, Iquique Province, Chile

AbstractThe new mineral nafeasite (IMA2021-103), NaFe3+(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, gypsum, halite, lavendulan, magnesiokoritnigite and natrojarosite. Nafeasite occurs in tightly intergrown aggregates of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~2½. The density is 3.23(2) g⋅cm–3. Optically, nafeasite is biaxial (+), with α = 1.679(3), β = 1.682(3), γ = 1.730(5) (white light); 2V = 27(2)°; and slight r < v dispersion. The empirical formulae of the holotype and cotype (based on 9 O atoms per formula unit) are Na0.98K0.02Fe0.92Al0.07As2.00O9H4.01 and Na0.97Fe0.68Al0.33As2.00O9H4.01, respectively. Nafeasite is monoclinic, space group C2, with cell parameters: a = 18.6876(16), b = 8.6769(7), c = 14.8100(10) Å, β = 105.238 (5)°, V = 2317.0(3) Å3 and Z = 12. The structure, refined to R1 = 5.03% for 5979 Io > 2σI reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and Fe3+O6 octahedra.

Geochemical evolution of a sublacustrine hydrothermal vent system: Temporal constraints imposed by reactive transport modeling

Studies of heat and mass transport in hydrothermal systems are challenging owing to the complex feedback that exists between chemical and physical processes. Taking full advantage of the existing geochemical framework recently recognized for sublacustrine vent fluids in the Stevenson Island Deep Hole, Yellowstone Lake, here we apply a multiphase reactive transport model, coupling hydraulic and thermal effects, to simulate time series changes in mineralization associated with venting of vapor-dominated hydrothermal fluids. This distinctive region of the lake floor is characterized by a series of overlapping depressions hosting sites of active venting. Model results show that the addition of high enthalpy steam enriched in CO2 and H2S, creates acidic and reducing conditions, while heating entrained lake water and coexisting sediment to temperatures in excess of 174 °C. The diatomaceous silica-rich substrate is predicted to dissolve, being replaced largely by pyrite, quartz, and kaolinite, in good agreement with the observed vent mineralization and fluid chemistry. Data suggest that vent-related mineral dissolution and transformation processes occur rapidly, on the order of 1 ka for the spatial scale of the modeled-up flow zone considered. The accuracy of time series changes predicted however, is explicitly linked to a number of physical and chemical factors imposed on the model, including source fluid, flow rate and gas enrichment, and sediment thermal conductivity, permeability, and reactive surface area, as well as mineral reaction rate data for primary and secondary alteration phases. When combined with robust field observations, as is the case here, reactive transport models can elucidate important, if not fundamental, controls on the temporal and spatial evolution of the geochemistry of modeled system, challenging chemical, and physical conditions notwithstanding.

Indigenous carbon-rich matter associated with unusual aqueous alteration features in Nakhla: Complex formation and preservation history

While indigenous organic matter has been previously reported in the Mars meteorite Nakhla, little is known as to either its form or distribution. A notable feature of Nakhla is the prevalence of secondary phases associated with aqueous alteration. By analogy with the terrestrial environment, our objective was to determine whether Martian secondary minerals could also act to accumulate and preserve such organic matter. Through a multidisciplinary approach, we have characterized the nature of carbonaceous matter and spatially associated phases within the Martian meteorite Nakhla using a wide-ranging suite of analytical instrumentation including optical microscopy, laser Raman spectroscopy, focused ion beam microscopy, secondary ion mass spectrometry, and scanning and transmission electron microscopy. In freshly fractured chips of Nakhla, we found carbonaceous phases intimately associated with secondary aqueous alteration phases, both mineral and amorphous, interpreted to have formed through the low-temperature aqueous dissolution of the host basalt while on Mars. The carbonaceous matter is present both in condensed phases and in a dispersed state spatially associated with secondary alteration phases. In the former, we identified discrete refractory micron to submicron assemblages that appear macromolecular in nature and, in several cases, associated with fluorine and, in one case, significant nitrogen. Textural, chemical, mineralogical and isotopic considerations argue for a non-terrestrial origin of this carbonaceous matter. Additionally, we report the presence of the ferrous hydroxycarbonate mineral chukanovite (Fe2OH2CO3) within some of the secondary mineral aggregates studied. Neither the intimate association of carbonaceous matter with secondary phases nor the identification of chukanovite have been previously reported in any of the Martian meteorites. In this regard, we note such microscale features within alteration phases would most likely be lost in the preparation of conventional polished thin sections and thus explain why they have not been previously reported. In lieu of sample return, the sui generis nature provided by Mars meteorites provide insight to alteration processes on Mars currently denied to robotic exploration and remote sensing. Our results show a variety of habitability-related sample attributes, formed hundreds of millions of years ago near Mars’ surface, have persisted there until very recently and may be more widespread in the surface regolith than previously thought. This may have implications in sample selection criteria for Mars sample return.

Application of Light Hydrocarbons in Natural Gas Geochemistry of Gas Fields in China

Light hydrocarbons (LHs) are an important component of natural gas whose chemical and isotopic compositions play a vital role in identifying gas genetic type, thermal maturity, gas–gas correlation, gas–source correlation, migration direction and phase, and secondary alterations (such as evaporative fractionation, biodegradation, and thermochemical sulfate reduction) experienced by the gas pool. Through review of geochemical research into LHs over recent decades, and analysis of chemical and isotopic compositions of LHs of gases and condensates from more than 40 gas fields in China, we present an overview of the genetic mechanisms of LHs and the impacts of various factors on their geochemical compositions. The primary objectives of this review are to demonstrate the application of LH chemical and isotopic composition characteristics to gas geochemistry research and to assess the applicability and reliability of geochemical identification diagrams and parameters for determining gas genetic types, maturity, source, secondary alteration, and migration direction and phase. ▪ Three main genetic mechanisms are proposed for the formation of light hydrocarbons: thermal decomposition, catalytic decomposition of organic matter, and microbial action. ▪ Chemical and isotopic compositions of light hydrocarbons with different carbon numbers and/or structures can be used to identify the genetic types and maturity of natural gas. ▪ Content ratios and carbon isotopes of characteristic light hydrocarbons are good indicators for gas–gas and gas–source correlations. ▪ Secondary alterations (evaporative fractionation, biodegradation, thermochemical sulfate reduction) and migration of gas can be indicated by chemical and isotopic compositions of light hydrocarbons.

Isolation and Reactivity of Uranyl Superoxide.

The high radiation field associated with spent nuclear fuel (UIV O2 ) pellets produces an array of reactive radical species that impact the corrosion and formation of secondary alteration phases. Dioxygen radicals are important as radiolysis products, but the interaction between these reactive oxygen species and UVI O22+ and its effects on the resultant alteration phases is unclear. We report the first example of a UVI superoxide compound and explore its reactivity in the environments relevant to the storage of spent nuclear fuel. We utilized X-ray diffraction and Raman scattering techniques to demonstrate that the uranyl superoxide reacts with CO2 in air to afford a mixed uranyl peroxide/carbonate within 3 days, both in solution and under atmospheric conditions. An additional transformation occurs over the course of 3 months to form a potassium UVI carbonate (grimselite), which also occurs as an alteration product on Chernobyl corium. Our results demonstrate the presence and significance of the superoxide anion in the alteration of spent nuclear fuel and indicate the impact of uranyl superoxide chemistry on high prevalence of carbonate in the secondary phases of spent nuclear fuel.

Isolation and Reactivity of Uranyl Superoxide

AbstractThe high radiation field associated with spent nuclear fuel (UIVO2) pellets produces an array of reactive radical species that impact the corrosion and formation of secondary alteration phases. Dioxygen radicals are important as radiolysis products, but the interaction between these reactive oxygen species and UVIO22+ and its effects on the resultant alteration phases is unclear. We report the first example of a UVI superoxide compound and explore its reactivity in the environments relevant to the storage of spent nuclear fuel. We utilized X‐ray diffraction and Raman scattering techniques to demonstrate that the uranyl superoxide reacts with CO2 in air to afford a mixed uranyl peroxide/carbonate within 3 days, both in solution and under atmospheric conditions. An additional transformation occurs over the course of 3 months to form a potassium UVI carbonate (grimselite), which also occurs as an alteration product on Chernobyl corium. Our results demonstrate the presence and significance of the superoxide anion in the alteration of spent nuclear fuel and indicate the impact of uranyl superoxide chemistry on high prevalence of carbonate in the secondary phases of spent nuclear fuel.

Nebular thermal processing of accretionary fine-grained rims in the Paris CM chondrite

Fine-grained rims (FGRs) are ubiquitous in chondrites. They consist of unequilibrated mineral assemblages that surround chondrules and refractory inclusions. As such, they carry information about the material that was accreted onto chondrules. To decipher the nature and the formation mechanism of FGRs and compare them to adjacent matrix material, we investigated their composition, mineralogy, density and texture in the pristine Paris CM chondrite. We coupled a new method at the SEM scale (ACADEMY) that allows high-resolution quantitative petrology and an analytical TEM study.Significant differences in modal abundance, grain size and porosity are observed between the FGRs and their adjacent matrix. Amorphous silicates domains embedding nanosulfides are indicative of a high preservation degree. They are less abundant in the matrix than in the rims. In contrast, secondary alteration phases (phyllosilicates, carbonates and tochilinites) are more abundant in the matrix and associated with larger and fewer sulfides grains. The similar composition of the amorphous silicate in the rims and the matrix attests for a close relationship between the two reservoirs. However, matrix underwent more aqueous alteration. We interpret it as the result of the accretion of material with a higher water/rock ratio in the matrix, leading to a more aqueously altered microenvironment. We also find that coarse-grained anhydrous silicates (olivine and pyroxene) are present in the matrix but not in the FGRs, likely as a result of a chondrule fragmentation episode that occurred after FGR but before matrix accretion.Most of the time, FGRs display distinct inner and outer layers. The inner part is compact and displays larger sulfide grains than the outer part, which is more porous (porosity ∼ 45%) and altogether more pristine. These mineral and textural differences are not easily explained by differential aqueous alteration. Instead, a pre-accretion thermal process that preferentially affected the inner rim could have induced loss of porosity, compaction of the amorphous silicate domains as well as sulfides growth. We therefore suggest that FGRs acquired their characteristics in the nebula before matrix accretion and discuss possible mechanisms such as dust heating in the chondrule formation environment or secondary heating episode of the previously rimmed chondrule.

Mauriziodiniite, NH4(As2O3)2I, the ammonium and iodine analogue of lucabindiite from the Torrecillas mine, Iquique Province, Chile

AbstractThe new mineral mauriziodiniite (IMA2019-036), NH4(As2O3)2I, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with calcite, cuatrocapaite-(NH4), lavendulan, magnesiokoritnigite and torrecillasite on matrix consisting of native arsenic, arsenolite and pyrite. Mauriziodiniite occurs as hexagonal tablets up to ~300 μm in diameter. Crystals are colourless and transparent, with pearly to adamantine lustre and white streak. The Mohs hardness is ~1. Tablets are sectile and easily flexible, but not elastic. Fracture is curved, irregular and stepped. Cleavage is perfect on {001}. The calculated density is 3.916 g/cm3. Optically, mauriziodiniite is uniaxial (–) with ω = 2.07(calc) and ɛ = 1.770(5) (white light). The empirical formula, determined from electron microprobe analyses, is (NH4)0.94K0.03(As2O3)2I0.92Cl0.03. Mauriziodiniite is hexagonal, P6/mmm, a = 5.289(2), c = 9.317(2) Å, V = 225.68(18) Å3 and Z = 1. The structure, refined to R1 = 4.16% for 135 Io > 2σI reflections, contains three types of layers: (1) a planar neutral As2O3 (arsenite) sheet; (2) an NH4+ layer that links adjacent arsenite sheets via bonds to their O atoms; and (3) an I– layer that links adjacent arsenite sheets via bonds to their As atoms. The layer sequence is I–As2O3–NH4–As2O3–I. Mauriziodiniite is isostructural with lucabindiite and is structurally related to gajardoite, cuatrocapaite-(NH4), cuatrocapaite-(K) and torrecillasite.

Cm(III) retention by calcium silicate hydrate (C-S-H) gel and secondary alteration phases in carbonate solutions with high ionic strength: A site-selective TRLFS study

We studied the Cm(III) retention by calcium silicate hydrate (C-S-H), portlandite (Ca(OH)2) and their alteration products calcite, vaterite, and aragonite in high ionic strength carbonate-containing solutions representing specific formation waters. For this, we synthesized C-S-H gels with calcium to silicon (C/S) ratios of 1.0 and 2.0 in the absence and presence of Cm(III), resulting in Cm(III)-free and Cm(III) doped C-S-H gel, respectively. For phase identification purposes we applied X-ray diffraction (XRD) while for the identification of the Cm(III)/C-S-H binding mode we applied site-selective time-resolved laser-induced luminescence spectroscopy (TRLFS). The stability of Cm(III) doped phases under repository-relevant conditions was evaluated by studying the time-dependent release of Cm(III) from the Cm(III) doped C-S-H gel into leaching solutions containing 0.02 M NaHCO3 or 2.5 M NaCl/0.02 M NaHCO3 over 60 d. Speciation changes of Cm(III) due to leaching were followed with TRLFS while C-S-H structure alterations and secondary phase formation were monitored with XRD. From the results it could be concluded that Cm(III) is not mobilized by aqueous carbonate but either remains incorporated in the C-S-H structure and portlandite or becomes partially re-immobilized into secondary CaCO3 phases. The presence of NaCl led to an accelerated conversion of metastable secondary CaCO3 phases into calcite.

Cuatrocapaite-(NH4) and cuatrocapaite-(K), two new minerals from the Torrecillas mine, Iquique Province, Chile, related to lucabindiite and gajardoite

AbstractThe new minerals cuatrocapaite-(NH4) (IMA2018-083) and cuatrocapaite-(K) (IMA2018-084) are the NH4- and K-dominant members of a series with the general formula (NH4,K)3(NaMg□)(As2O3)6Cl6·16H2O. Both minerals were found at the Torrecillas mine, Iquique Province, Chile, where they occur as secondary alteration phases. Both minerals occur as hexagonal tablets up to ~0.3 mm in diameter. They are transparent, with a vitreous lustre and white streak. For both, the Mohs hardness isca. 2½, the crystals are somewhat flexible, but not elastic, the fracture is irregular and the cleavage is perfect on {001}. The measured densities are 2.65(2) and 2.76(2) g/cm3for the NH4- and K-dominant species, respectively. Optically, cuatrocapaite-(NH4) is uniaxial (–) with ω = 1.779(3) andε= 1.541(3) and cuatrocapaite-(K) is uniaxial (–) with ω = 1.777(3) andε= 1.539(3) (white light). The minerals are insoluble in acids, but decompose in NaOH(aq). The empirical formulas, determined from electron-microprobe analyses, are (NH4)2.48Na1.66Mg0.87K0.09(As12O18.05)Cl5.88·16.02H2O and K2.68Na1.33Mg0.93(NH4)0.31(As12O18.01)Cl6.16·16.04H2O. The minerals are trigonal, space groupR${\bar 3}$m; the cuatrocapaite-(NH4) cell parameters area= 5.25321(19),c= 46.6882(19) Å,V= 1115.80(9) Å3andZ= 1; the cuatrocapaite-(K) cell parameters area= 5.2637(15),c= 46.228(8) Å,V= 1109.2(7) Å3andZ= 1. The structures, refined for cuatrocapaite-(NH4) toR1= 1.78% for 544Io> 2σIreflections, contain four types of layers: (1) a planar neutral As2O3(arsenite) sheet; (2) an (${\rm NH}_{\rm 4}^{\vskip -2pt\rm \scale65% +} $,K+) layer that links adjacent arsenite sheets; (3) a Cl–layer placed on the As side of each arsenite; and (4) a layer containing partially occupied Na, Mg and H2O sites that is flanked on either side by Cl layers. The layer sequence for the type 1, 2 and 3 layers is identical to the Cl–As2O3–K–As2O3–Cl layer sequence in the structures of lucabindiite and gajardoite.

Greenlizardite, (NH4)Na(UO2)2(SO4)2(OH)2·4H2O, a new mineral with phosphuranylite-type uranyl sulfate sheets from Red Canyon, San Juan County, Utah, USA

ABSTRACTThe new mineral greenlizardite (IMA2017-001), (NH4)Na(UO2)2(SO4)2(OH)2·4H2O, was found in the Green Lizard mine, Red Canyon, San Juan County, Utah, USA, where it occurs as a secondary alteration phase. It is associated with ammoniozippeite, boussingaultite and dickite. It forms as light green-yellow blades up to ~0.3 mm long. The mineral is vitreous and transparent with a white streak. It fluoresces greenish blue in 405 nm light. Mohs hardness is ~2. Crystals are brittle with irregular fracture and two cleavages: perfect {001} and good {2$\bar 1$0}. Greenlizardite is easily soluble in room-temperature H2O. The calculated density is 3.469 g cm–3. Optically, it is biaxial (+) with α = 1.559(1), β = 1.582(1) and γ = 1.608(1) (measured in white light). The measured 2V is 88(1)°; the calculated 2V is 87.8°. Dispersion is moderate, r < v. Pleochroism is X = very pale yellow green, Y = pale yellow green and Z = light yellow green; X < Y < Z. The optical orientation is X ≈ c, Y ≈ a and Z ≈ b*. The Raman spectrum exhibits bands attributable to both sulfate and uranyl groups. Electron probe microanalyses (with H2O based on the crystal structure) yielded (NH4)0.98Na1.00U1.96S2.04O18.00H10.02. Greenlizardite is triclinic, P$\bar 1$, a = 6.83617(17), b = 9.5127(3), c = 13.8979(10) Å, α = 98.636(7), β = 93.713(7), γ = 110.102(8)°, V = 832.49(8) Å3 and Z = 2. The crystal structure (R1 = 2.39% for 2542 I > 2σI) contains edge-sharing dimers of UO7 pentagonal bipyramids. The dimers link by sharing corners with SO4 groups to form a [(UO2)2(SO4)2(OH)2]2– sheet based on the phosphuranylite anion topology. Zig-zag edge-sharing chains of NaO6 octahedra link adjacent [(UO2)2(SO4)2(OH)2]2– sheets, forming thick slabs. NH4 bonds to O atoms in adjacent slabs linking them together. H2O groups occupy channels in the slabs and space between the slabs.

Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals

A cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) was developed in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. The method was applied to determine REE abundances in four uraninite (ideally UO2) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondary uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca2+ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K+ and Pb2+ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since a comparison is reported between the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.

Currierite, Na4Ca3MgAl4(AsO3OH)12·9H2O, a new acid arsenate with ferrinatrite-like heteropolyhedral chains from the Torrecillas mine, Iquique Province, Chile

AbstractThe new mineral currierite (IMA2016-030), Na4Ca3MgAl4(AsO3OH)12·9H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with anhydrite, canutite, chudobaite, halite, lavendulan, magnesiokoritnigite, quartz, scorodite and torrecillasite. Currierite occurs as hexagonal prisms, needles and hair-like fibres up to ∼200 μm long, in sprays. The crystal forms are ﹛100﹜ and ﹛001﹜. Crystals are transparent, with vitreous to silky lustre and white streak. The Mohs hardness is ∼2, tenacity is brittle, but elastic in very thin fibres, and the fracture is irregular. Crystals exhibit at least one good cleavage parallel [001]. The measured density is 3.08(2) g cm -3 and the calculated density is 3.005 g cm -3. Optically, currierite is uniaxial (–) with ω= 1.614(1) and ε= 1.613(1) (measured in white light). The mineral is slowly soluble in dilute HCl at room temperature. The empirical formula, determined from electron-microprobe analyses, is (Na3.95A12.96Ca2.74Mg1.28Fe0.633+Cu0.13K0.08Co0.03Σ11.80 (AS11.685+Sb0.325+Σ12(O56.96Cl0.04)Σ57H30.81. Currierite is hexagonal, P622, with a = 12.2057(9), c = 9.2052(7) Å, V= 1187.7(2) Å3 and Z = 1. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 10.63(100)(100), 6.12(20)(110), 5.30(15)(200), 4.61(24)(002), 4.002(35)(210), 3.474(29)(202), 3.021(96)(212) and 1.5227(29)(440,334,612). The structure of currierite (R1 = 2.27% for 658 Fo > 4σF reflections) is based upon a heteropolyhedral chain along c in which AlO6 octahedra are triple-linked by sharing corners with AsO3OH tetrahedra. Chains are linked to one another by bonds to 8(4 + 4)-coordinated Na and 8-coordinated Ca forming a three-dimensional framework with large cavities that contain rotationally disordered Mg(H2O)6 octahedra. The chain in the structure of currierite is identical to that in kaatialaite and a geometrical isomer of that in ferrinatrite. The mineral is named in honour of Mr. Rock Henry Currier (1940–2015), American mineral dealer, collector, author and lecturer.

Reduced and unstratified crust in CV chondrite parent body

Early Solar System planetesimal thermal models predict the heating of the chondritic protolith and the preservation of a chondritic crust on differentiated parent bodies. Petrological and geochemical analyses of chondrites have suggested that secondary alteration phases formed at low temperatures (<300 °C) by fluid-rock interaction where reduced and oxidized Vigarano type Carbonaceous (CV) chondrites witness different physicochemical conditions. From a thermodynamical survey of Ca-Fe-rich secondary phases in CV3 chondrites including silica activity (aSiO2), here we show that the classical distinction between reduced and oxidized chondrites is no longer valid and that their Ca-Fe-rich secondary phases formed in similar reduced conditions near the iron-magnetite redox buffer at low aSiO2 (log(aSiO2) <−1) and moderate temperature (210–610 °C). The various lithologies in CV3 chondrites are inferred to be fragments of an asteroid percolated heterogeneously via porous flow of hydrothermal fluid. Putative ‘onion shell’ structures are not anymore a requirement for the CV parent body crust.

Chinleite-(Y), NaY(SO4)2·H2O, a new rare-earth sulfate mineral structurally related to bassanite

AbstractThe new mineral chinleite-(Y) (IMA2016-017), NaY(SO4)2·H2O, was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as a secondary alteration phase. Chinleite-(Y) crystals are thin hexagonal {100} prisms (up to 0.3 mm long) with pyramidal terminations consisting of the forms {101} and {011}. Prisms are typically intergrown in divergent sprays, bow-tie aggregates or subparallel intergrowths. Crystals are colourless and transparent with a vitreous lustre. The streak is white and the mineral is nonfluorescent. The Mohs hardness is between 2½ and 3. Crystals are brittle with at least one good cleavage parallel to [001], probably {100}, and have splintery fracture. The mineral is slowly soluble in H2O at room temperature. The calculated density is 3.385 g cm–3. The mineralis optically uniaxial (+), with ω = 1.565(1) and ε = 1.603(1) (white light). Electron microprobe analyses yielded the empirical formula (Na0.507Ca0.285Y0.176)∑0.968(Y0.724Dy0.110Er0.053Gd0.037Ho0.021Yb0.013Nd0.014Eu0.005Sm0.008Ce0.010Pr0.003La0.002)∑1.000(SO4)2·H1.401O.The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 6.01(59)(100), 5.43(63)(011), 3.457(46)(110), 3.010(100)(200), 2.826(95)(014), 2.1365(39)(006,122), 1.8493(67)(214) and 1.6901(28)(125,034). Chinleite-(Y) is trigonal, P3221,a = 6.890(2), c = 12.767(2) Å, V = 524.9(3) Å3 and Z = 3. The structure of chinleite-(Y) (R1 = 0.0444 for 303 Fo &gt; 4σF), a three-dimensional framework, consisting of SO4 groups, irregular NaO8 polyhedra and YO9 distorted tricapped trigonal prisms, is similar to the structure of bassanite.

Significance of halogens (F, Cl) in kimberlite melts: Insights from mineralogy and melt inclusions in the Roger pipe (Ekati, Canada)

The abundance and distribution of halogens (F, Cl) are rarely recorded in kimberlites and therefore their petrogenetic significance is poorly constrained. Halogens are usually present in kimberlite rocks in the structure of phlogopite and apatite, but their original concentrations are never fully retained due to the effects of alteration. To provide new constraints on the origin and evolution of halogens in kimberlites and their melts, we present a detailed study of the petrography and geochemistry of the late-Cretaceous Group-I (or archetypal) Roger kimberlite (Ekati cluster, Canada). The studied samples contain abundant anhedral-to-euhedral olivine which is set in a crystalline groundmass of monticellite, phlogopite, apatite, spinel (i.e. magnesian ulvöspinel-magnetite (MUM), Mg-magnetite, pleonaste, Cr-spinel), and perovskite along with abundant secondary alteration phases (i.e. serpentine, garnet (andradite-schlorlomite), amakinite ((Fe2+, Mg, Mn)(OH)2), calcite). The Roger kimberlite is characterised by the highest recorded F-content (up to 2688ppm) of the Ekati cluster kimberlites, which is reflected by the preservation of F-rich phases, where bultfonteinite (Ca4(Si2O7)(F, OH)2) and fluorite commonly replace olivine.In order to examine the composition and evolution of the kimberlite melt prior to post-magmatic processes, we studied melt inclusions in olivine, Cr-spinel, monticellite and apatite. Primary multiphase melt inclusions in Cr-spinel, monticellite and apatite and secondary inclusions in olivine are shown to contain a diversity of daughter phases and compositions that are dominated by alkali/alkali-earth (Na, K, Ba, Sr)-enriched Ca-Mg-carbonates±F, Na-K-chlorides and sulphates, phosphates±REE, spinel, silicates (e.g. olivine, phlogopite, (clino)humite), and sulphides. Although alkali/alkali-earth- and halogen-bearing phases are abundant in melt inclusions, they are generally absent from the kimberlite groundmass, most likely due to ubiquitous effects of syn- and/or post-magmatic alteration (i.e. serpentinisation).Comparisons between halogens and other trace elements of similar compatibility (i.e. F/Nd and Cl/U) in the Roger kimberlite and their respective estimated primitive mantle abundances show that halogens should be a more significant component in kimberlites than typically measured. We propose that fluorine in the Roger kimberlite was magmatic and was redistributed during hydrothermal alteration by Ca-bearing serpentinising fluids to produce the observed bultfonteinite/fluorite assemblages. Based the compositions and daughter mineral assemblages in primary melt inclusions and reconstructed halogen abundances, we suggest that Cr-spinel, monticellite and apatite crystallised from a variably differentiated Si-P-Cl-F-bearing carbonate melt that was enriched in alkalis/alkali-earths and highly incompatible trace elements.