Kimberly T. Tait

Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon

Invaluable records of planetary dynamics and evolution can be recovered from the geochemical systematics of single meteorites. However, the interpreted ages of the ejected igneous crust of Mars differ by up to four billion years, a conundrum due in part to the difficulty of using geochemistry alone to distinguish between the ages of formation and the ages of the impact events that launched debris towards Earth. Here we solve the conundrum by combining in situ electron-beam nanostructural analyses and U–Pb (uranium–lead) isotopic measurements of the resistant micromineral baddeleyite (ZrO2) and host igneous minerals in the highly shock-metamorphosed shergottite Northwest Africa 5298 (ref. 8), which is a basaltic Martian meteorite. We establish that the micro-baddeleyite grains pre-date the launch event because they are shocked, cogenetic with host igneous minerals, and preserve primary igneous growth zoning. The grains least affected by shock disturbance, and which are rich in radiogenic Pb, date the basalt crystallization near the Martian surface to 187 ± 33 million years before present. Primitive, non-radiogenic Pb isotope compositions of the host minerals, common to most shergottites, do not help us to date the meteorite, instead indicating a magma source region that was fractionated more than four billion years ago to form a persistent reservoir so far unique to Mars. Local impact melting during ejection from Mars less than 22 ± 2 million years ago caused the growth of unshocked, launch-generated zircon and the partial disturbance of baddeleyite dates. We can thus confirm the presence of ancient, non-convecting mantle beneath young volcanic Mars, place an upper bound on the interplanetary travel time of the ejected Martian crust, and validate a new approach to the geochronology of the inner Solar System.

Inelastic neutron scattering study of hydrogen in d8-THF∕D2O ice clathrate

In situ neutron inelastic scattering experiments on hydrogen adsorbed into a fully deutrated tetrahydrofuran-water ice clathrate show that the adsorbed hydrogen has three rotational excitations (transitions between J=0 and 1 states) at approximately 14 meV in both energy gain and loss. These transitions could be unequivocally assigned since there was residual orthohydrogen at low temperatures (slow conversion to the ground state) resulting in an observable J=1-->0 transition at 5 K (kT=0.48 meV). A doublet in neutron energy loss at approximately 28.5 meV is interpreted as J=1-->2 transitions. In addition to the transitions between rotational states, there are a series of peaks that arise from transitions between center-of-mass translational quantum states of the confined hydrogen molecule. A band at approximately 9 meV can be unequivocally interpreted as a transition between translational states, while broad features at 20, 25, 35, and 50-60 meV are also interpreted to as transitions between translational quantum states. A detailed comparison is made with a recent five-dimensional quantum treatment of hydrogen in the smaller dodecahedral cage in the SII ice-clathrate structure. Although there is broad agreement regarding the features such as the splitting of the J=1 degeneracy, the magnitude of the external potential is overestimated. The numerous transitions between translational states predicted by this model are in poor agreement with the experimental data. Comparisons are also made with three simple exactly solved models, namely, a particle in a box, a particle in a sphere, and a particle on the surface of a sphere. Again, there are too many predicted features by the first two models, but there is reasonable agreement with the particle on a sphere model. This is consistent with published quantum chemistry results for hydrogen in the dodecahedral 5(12) cage, where the center of the cage is found to be energetically unfavorable, resulting in a shell-like confinement for the hydrogen molecule wave function. These results demonstrate that translational quantum effects are very significant and a classical treatment of the hydrogen molecule dynamics is inappropriate under such conditions.

Dellaventuraite, NaNa2(MgMn23+Ti4+Li)Si8O22O2, a new anhydrous amphibole from the Kajlidongri Manganese Mine, Jhabua District, Madhya Pradesh, India

Abstract Dellaventuraite is a new amphibole species from the Kajlidongri manganese mine, Jhabua District, Madhya Pradesh, India. It occurs with leakeite, kornite, albite, braunite, and bixbyite associated with cross-cutting epigenetic veins that have reacted with regionally metamorphosed rocks containing Mn-rich minerals (braunite, bixbyite, jacobsite, spessartine) to produce Mn-rich amphiboles, Mnrich pyroxenes, Mn-rich mica, piemontite, and manganophyllite. Dellaventuraite occurs as anhedral grains, the color of which varies from pink to red, depending on Mn content. It is brittle, H = 5, Dcalc = 3.184 g/cm3, has a pale pink streak, vitreous luster, and does notfluoresce in ultraviolet light; it has perfect cleavage on {110} and conchoidal fracture. In transmitted plane-polarized light, dellaventuraite is strongly pleochroic, X = pale mauve-brown, Y ~ Z = dark red-brown; Y ^ a = 20° (in β obtuse), Z = b, with absorption X < Y ~ Z. It is biaxial positive, ηα = 1.688 ± 0.003, ηβ = 1.692 ± 0.005, ηγ = 1.721 ± 0.003, 2V(obs) = 49 ± 3°, 2V(calc) = 41°. Dellaventuraite is monoclinic, space group C2/m, a = 9.808(1), b = 17.840(2), c = 5.2848(5) Å, γ = 104.653(1)°, V = 894.6(2) Å3, Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(I,hkl)]: 2.697(10,151), 2.542(9,.202), 3.127(8,310), 3.378(7,131), 2.154(7,261), 1.434 (7,.661), 4.450(6,021), 8.459(5,110), 2.727(5,.331), 2.328(5,.351). Analysis by a combination of electron microprobe, SIMS and crystal-structure refinement gives SiO2 = 54.22, Al2O3 = 0.81, TiO2 = 5.45, Fe2O3 = 6.44, Mn2O3 = 7.57, ZnO = 0.12, NiO = 0.16, MgO = 8.26, Li2O = 1.53, CaO = 1.85, Na2O = 8.12, K2O = 2.12, H2O = 0.80, Cr, V, F, Cl not detected, sum 97.41 wt%. The formula unit, calculated on the basis of 24(O,OH,F) is (K0.40Na0.61)(Na1.71Ca0.29) (Mg1.81Zn0.01 Ni0.02-Li0.90Fe3+0.71Mn3+ 0.85Ti4+ 0.60Al0.10)(Si7.96Al0.04)O22[(OH)0.80 O1.20]; the ideal end-member composition NaNa2(MgMn3+2LiTi04+)Si8O22O2. The crystal structure of dellaventuraite was refined to an R index of 3.8% using MoKα X-ray intensity data. The M1 site is occupied by Ti4+, Mn4+, and Mg in approximately equal amounts, the M2 site is occupied primarily by Mg and Fe3+, and M3 is occupied by Li with minor Mg and Mn2+. Local bond-valence considerations suggest that O2-at O3 is linked to Ti4+Mg or Mn3+Mn3+ at the adjacent M1 sites, and that OH at O3 is linked to MgMg at the adjacent M1 sites.

High-pressure/low-temperature neutron scattering of gas inclusion compounds: Progress and prospects

Alternative energy resources such as hydrogen and methane gases are becoming increasingly important for the future economy. A major challenge for using hydrogen is to develop suitable materials to store it under a variety of conditions, which requires systematic studies of the structures, stability, and kinetics of various hydrogen-storing compounds. Neutron scattering is particularly useful for these studies. We have developed high-pressure/low-temperature gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments allowing in situ and real-time examination of gas uptake/release processes. We studied the formation of methane and hydrogen clathrates, a group of inclusion compounds consisting of frameworks of hydrogen-bonded H2O molecules with gas molecules trapped inside the cages. Our results reveal that clathrate can store up to four hydrogen molecules in each of its large cages with an intermolecular H2–H2 distance of only 2.93 Å. This distance is much shorter than that in the solid/metallic hydrogen (3.78 Å), suggesting a strong densification effect of the clathrate framework on the enclosed hydrogen molecules. The framework-pressurizing effect is striking and may exist in other inclusion compounds such as metal-organic frameworks (MOFs). Owing to the enormous variety and flexibility of their frameworks, inclusion compounds may offer superior properties for storage of hydrogen and/or hydrogen-rich molecules, relative to other types of compounds. We have investigated the hydrogen storage properties of two MOFs, Cu3[Co(CN)6]2 and Cu3(BTC)2 (BTC = benzenetricarboxylate), and our preliminary results demonstrate that the developed neutron-scattering techniques are equally well suited for studying MOFs and other inclusion compounds.

Crystal structure refinements of borate dimorphs inderite and kurnakovite using 11 B and 25 Mg nuclear magnetic resonance and DFT calculations

Abstract Borate minerals composed of [Bφ3] triangles and/or [Bφ4] tetrahedra (φ = O or OH) commonly exhibit complex polymerizations to form diverse polyanion groups. High-resolution solid-state magic angle spinning (MAS) 11B and 25Mg NMR spectroscopy at moderate to ultrahigh magnetic fields (9.4, 14.1, and 21.1 T) allows for very accurate NMR parameters to be obtained for the borate dimorphs, inderite, and kurnakovite, [MgB3O3(OH)5·5H2O]. Improved agreement between experimental results and ab initio density functional theory (DFT) calculations using Full Potential Linear Augmented Plane Wave (FP LAPW) with WIEN2k validates the geometry optimization procedures for these minerals and permits refinements of the hydrogen positions relative to previous X-ray diffraction crystal structures. In particular, the optimized structures lead to significant improvements in the positions of the H atoms, suggesting that H atoms have significant effects on the 11B and 25Mg NMR parameters in inderite and kurnakovite. This study shows that combined high-resolution NMR spectroscopy and ab initio theoretical modeling provides an alternative method for the refinement of crystal structures, especially H positions.

Crystal structure of uchucchacuaite, AgMnPb3Sb5S12, and its relationship with ramdohrite and fizélyite

Abstract Uchucchacuaite, ideally AgMnPb3Sb5S12, was originally reported as orthorhombic, with possible space group Pmmm, P222, or Pmm2, and unit-cell parameters a = 12.67, b = 19.32, and c = 4.38 Å obtained from powder X‑ray diffraction data (Moëlo et al. 1984a). Using single-crystal X‑ray diffraction, we examined two uchucchacuaite samples, one from the type locality, Uchucchacua, Peru, and the other from Hokkaido, Japan (designated as R100213 and R070760, respectively). Our results show that uchucchacuaite is isostructural with ramdohrite and fizélyite, with monoclinic symmetry (P21/n) and the unit-cell parameters a = 19.3645(11), b = 12.7287(8), c = 8.7571(6) Å, β = 90.059(3)° for R100213 and a = 19.3462(7), b = 12.7251(5), c = 8.7472(3) Å, β = 90.017(2)° for R070760. Both samples are pervasively twinned and the twin refinements yielded the final R1 factors of 0.037 and 0.031 for R100213 and R070760, respectively. The chemical compositions determined from electron microprobe analysis are Ag0.99(Mn0.92Pb0.03Sb0.02Bi0.01)Σ=0.98Pb3.00Sb5.00S12.00 for R100213 and Ag1.00(Mn0.82Sb0.11Ag0.04Bi0.02)Σ=0.99Pb2.98Sb5.00S12.00 for R070760. The key structural difference among uchucchacuaite, ramdohrite, and fizélyite lies in the cations occupying the M2 site, which can be expressed with a general structural formula as Ag(M2+2yAg½-ySb½-y)Pb3Sb5S12, where M2+ represents divalent cations with 0 ≤ y ≤ ½. From the current list of IMA-defined minerals, we consider M = Cd with y = 0.125 for ramdohrite, M = Pb with y = 0.25 for fizélyite, and M = Mn with y = 0.5 for uchucchacuaite. Associated with the variation in the average M2 cation size from fizélyite (1.078 Å) to ramdohrite (0.955 Å) and uchucchacuaite (0.83 Å) is the significant decrease in the average M2-S bond distance from 2.917 to 2.834, and 2.654 Å, respectively, as well as corresponding variations in the unit-cell b dimension from ~13.23 to 13.06 and 12.73 Å.

Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, a new arsenate mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia: description and crystal structure

Abstract Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as thin platy crystals up to 80 μm long and a few mm thick, which form flattened aggregates up to 0.10 mm across, and ellipsoidal aggregates up to 0.5 mm across. It is associated with coarse white leiteite, dark blue köttigite, minor legrandite and adamite. Ianbruceite is sky blue to very pale blue with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. It has perfect cleavage parallel to (100), is flexible, and deforms plastically. The Mohs hardness is 1 and the calculated density is 3.197 g cm-3. The refractive indices are α = 1.601, β = 1.660, γ = 1.662, all ±0.002; 2Vobs = 18(2)º, 2Vcalc = 20º, and the dispersion is r < v, weak. Ianbruceite is monoclinic, space group P21/c, a = 11.793(2), b = 9.1138(14), c = 6.8265(10) Å, β = 103.859(9)º, V = 712.3(3) Å3, Z = 4, a:b:c = 1.2940:1:0.7490. The seven strongest lines in the X-ray powder diffraction pattern [d (Å), I, (hkl)] are as follows: 11.29, 100, (100); 2.922, 17, (130); 3.143, 15, (2̄02); 3.744, 11, (300); 2.655, 9, (230); 1.598, 8, (1̄52); 2.252, 7, (222). Chemical analysis by electron microprobe gave As2O5 36.27, As2O3 1.26, Al2O3 0.37, ZnO 49.72, MnO 0.32, FeO 0.71, K2O 0.25, H2Ocalc 19.89, sum 108.79 wt.%; the very high oxide sum is due to the fact that the calculated H2O content is determined from crystal-structure analysis, but H2O is lost under vacuum in the electron microprobe. The crystal structure of ianbruceite was solved by direct methods and refined to an R1 index of 8.6%. The As is tetrahedrally coordinated by four O anions with a mean As-O distance of 1.687 Å. Zigzag [[5]Zn[6]Znφ7] chains extend in the c direction and are linked in the b direction by sharing corners with (AsO4) tetrahedra to form slabs with a composition [Zn2(OH)(H2O)(AsO4)]. The space between these slabs is filled with disordered (H2O) groups and minor lone-pair stereoactive As3+. The ideal formula derived from chemical analysis and crystal-structure solution and refinement is [Zn2(OH)(H2O)(AsO4)](H2O)2.

Veblenite, K2_2Na(Fe2+5 Fe3+4 Mn2+7_)Nb3Ti(Si2O7)2 (Si8O22)2O6(OH)10(H2O)3, a new mineral from Seal Lake, Newfoundland and Labrador: mineral description, crystal structure, and a new veblenite (Si8O22) ribbon

Abstract Veblenite, ideally K2⃞2Na(Fe52+ Fe43+ Mn72+ ⃞)Nb3Ti(Si2O7)2(Si8O22)2O6(OH)10(H2O)3, is a new mineral with no natural or synthetic analogues. The mineral occurs at Ten Mile Lake, Seal Lake area, Newfoundland and Labrador (Canada), in a band of paragneiss consisting chiefly of albite and arfvedsonite. Veblenite occurs as red brown single laths and fibres included in feldspar. Associated minerals are niobophyllite, albite, arfvedsonite, aegirine-augite, barylite, eudidymite, neptunite, Mn-rich pectolite, pyrochlore, sphalerite and galena. Veblenite has perfect cleavage on {001} and splintery fracture. Its calculated density is 3.046 g cm-3. Veblenite is biaxial negative with α 1.676(2), β 1.688(2), γ 1.692(2) (λ 590 nm), 2Vmeas = 65(1)º, 2Vcalc = 59.6º, with no discernible dispersion. It is pleochroic in the following pattern: X = black, Y = black, Z = orange-brown. The mineral is red-brown with a vitreous, translucent lustre and very pale brown streak. It does not fluoresce under short and long-wave UV-light. Veblenite is triclicnic, space group P1̄ , a 5.3761(3), b 27.5062(11), c 18.6972(9) Å, α 140.301(3), β 93.033(3), γ 95.664(3)º, V = 1720.96(14) Å3. The strongest lines in the X-ray powder diffraction pattern [d(Å)(I)(hkl)] are: 16.894(100)(010), 18.204(23)(01̄1), 4.271(9)(14̄1, 040, 120), 11.661(8)(001), 2.721(3)(19̄5), 4.404(3)(1̄3̅2, 14̄2), 4.056(3)(031, 11̄2; 15̄2, 1̄4̄3), 3.891(2)(003). The chemical composition of veblenite from a combination of electron microprobe analysis and structural determination for H2O and the Fe2+/Fe3+ ratio is Nb2O5 11.69, TiO2 2.26, SiO2 35.71, Al2O3 0.60, Fe2O3 10.40, FeO 11.58, MnO 12.84, ZnO 0.36, MgO 0.08, BaO 1.31, SrO 0.09, CaO 1.49, Cs2O 0.30, K2O 1.78, Na2O 0.68, H2O 4.39, F 0.22, O = F - 0.09, sum 95.69 wt.%. The empirical formula [based on 20 (Al+Si) p.f.u. is (K0.53Ba0.28Sr0.03⃞0.16)∑1(K0.72Cs0.07⃞1.21)∑2(Na0.72Ca0.17⃞1.11)∑2(Fe5.322+Fe4.133+Mn5.972+Ca0.70Zn0.15Mg0.07⃞0.66)∑17(Nb2.90Ti0.93Fe0.173+)∑4(Si19.61Al0.39)∑20O77.01H16.08F0.38. The simplified formula is (K,Ba,⃞)3(⃞,Na)2(Fe2+,Fe3+,Mn2+)17(Nb,Ti)4(Si2O7)2(Si8O22)2O6(OH)10(H2O)3. The infrared spectrum of the mineral contains the following bands (cm-1): 453, 531, 550, 654 and 958, with shoulders at 1070, 1031 and 908. A broad absorption was observed between ~3610 and 3300 with a maximum at ~3525. The crystal structure was solved by direct methods and refined to an R1 index of 9.1%. In veblenite, the main structural unit is an HOH layer, which consists of the octahedral (O) and two heteropolyhedral (H) sheets. The H sheet is composed of Si2O7 groups, veblenite Si8O22 ribbons and Nb-dominant D octahedra. This is the first occurrence of an eight-membered Si8O22 ribbon in a mineral crystal structure. In the O sheet, (Fe2+, Fe3+, Mn2+) octahedra share common edges to form a modulated O sheet parallel to (001). HOH layers connect via common vertices of D octahedra and cations at the interstitial A(1,2) and B sites. In the intermediate space between two adjacent HOH layers, the A(1) site is occupied mainly by K; the A(2) site is partly occupied by K and H2O groups, the B site is partly occupied by Na. The crystal structure of veblenite is related to several HOH structures: jinshanjiangite, niobophyllite (astrophyllite group) and nafertisite. The mineral is named in honour of David R. Veblen in recognition of his outstanding contributions to the fields of mineralogy and crystallography.

Davidlloydite, ideally Zn3(AsO4)2(H2O)4, a new arsenate mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia: description and crystal structure

Abstract Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (~10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 μm in size. The crystals occur as aggregates (up to 500 μm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3-4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm-3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are α = 1.671, β = 1.687, γ = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r < v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1̅, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, α = 84.2892(9), β = 90.4920(9), γ = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 1̅10); 7.526, 71, (010); 2.974, 49, (200, 02̅1); 3.253, 40, (021, 120); 2.701, 39, (2̅10, 002, 1̅2̅1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave AS2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)∑2.92AS2.03O8(H2O)4. The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKα radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of comer-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.

Pieczkaite, ideally Mn5(PO4)3Cl, a new apatite-supergroup mineral from Cross Lake, Manitoba, Canada: Description and crystal structure

Abstract Pieczkaite, ideally Mn5(PO4)3Cl, is a new apatite-supergroup mineral from Cross Lake, Manitoba, Canada. It occurs as small patches and narrow veins in large crystals of apatite and (Mn,Cl)-bearing apatite in phosphate pods in the quartz core of a granitic pegmatite. Veins of Mn-bearing apatite narrow to ~25 μm where the Mn content becomes high enough to constitute pieczkaite. It is gray with a grayish-white streak, does not fluoresce under ultraviolet light, and has no observable cleavage or parting. Mohs hardness is 4-5, and pieczkaite is brittle with an irregular fracture. The calculated density is 3.783 g/cm3. Optical properties were measured using a Bloss spindle stage at a wavelength of 590 nm (using a gel filter). Pieczkaite is uniaxial (-) with indices of refraction ω = 1.696, ε = 1.692, both ±0.002. Pieczkaite is hexagonal, space group P63/m, a = 9.504(4), c = 6.347(3) Å, V = 496.5(1) Å3, Z = 2, c:a = 1:0.6678. The six strongest lines in the X‑ray powder diffraction pattern are as follows: d (Å), I, (hkl): 2.794, 100, (2̅31, 1̅31); 2.744, 88, (030); 2.639, 34, (1̅22); 2.514, 25, (031, 022); 1.853, 25, (3̅42, 1̅42); 3.174, 24, (002). Chemical analysis by electron microprobe gave P2O5 37.52, MnO 41.77, FeO 2.45, CaO 13.78, Cl 3.86, H2O 0.60, O≡Cl -0.87, sum 99.11 wt% where the H2O content was calculated as 1 - Cl apfu. The resulting empirical formula on the basis of 12 O anions is (Mn3.36Fe0.20Ca1.40)Σ4.96 (P1.01O4)3(Cl0.62OH0.38)1.00, and the end-member formula is Mn5(PO4)3Cl. The crystal structure of pieczkaite was refined to an R1 index of 4.07% based on 308 observed reflections collected on a three-circle rotating-anode diffractometer with MoKα X-radiation. Pieczkaite is isostructural with apatite, Mn is the dominant cation at both the [9]- and [7]-coordinated-cation sites in the structure, and Cl is the dominant monovalent anion.