bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mineralogical controls on arsenic mobility in the Baccu Locci stream catchment (Sardinia, Italy) affected by past mining
Authors: Frau F. , Ardau C. 
Published: August 2004

AbstractMineralogical-chemical techniques (XRD, SEM/EDX, WDXRF) and a sequential selective extraction procedure were applied to mine-waste materials and stream sediments from the Baccu Locci stream catchment (Sardinia, Italy) affected by serious As contamination as a consequence of past mining. Results indicate that solid-state speciation of As is mainly dominated by the presence of Fe(III) hydroxides (arsenical ferrihydrites with various Fe/As molar ratios) occurring as coatings of silicate grains, in which As is contained as sorbed or co-precipitated species. Scorodite (FeAsO4·2H2O) is common too, whereas arsenopyrite is generally subordinate but, owing to its relatively rapid oxidation, environmentally significant. Moreover, some unidentified arsenates of Ca-Fe or K-Fe were also detected. Arsenic contained in these phases is slowly, but continuously, released in relatively small amounts through three main mechanisms: (1) oxidation of residual arsenopyrite to scorodite; (2) decomposition of scorodite into a hydroxide or oxide of Fe(III); (3) desorption/release from Fe(III) hydroxides. Decomposition of the unidentified arsenates is also probable, e.g. Ca-Fe arsenate → calcite + Fe(III) hydroxide + As release. The flotation tailings are widely scattered and distributed in the middle–lower Baccu Locci stream catchment, and represent the most dangerous As-generating contamination source in the study area.
The respiratory toxicity of airborne volcanic ash from the Soufrière Hills volcano, Montserrat
Authors: Bérubé K. A. , Jones T. P. , Housley D. G. , Richards R. J. 
Published: August 2004

AbstractThe Soufrière Hills stratovolcano on the Caribbean island of Montserrat has been erupting since 18th July 1995. An enormous amount of respirable volcanic ash has been suspended into the atmosphere by the eruptions and wind re-suspension of deposited ash. The large amount of fine, airborne particulate matter, in particular the component 10 μm equivalent aerodynamic diameter (PM10), is a cause of medical concern. Airborne levels have frequently exceeded the UK environmental standard for PM10, (50 μg/m3), although it is noted that this standard was primarily set for urban PM10. The crystalline silica in the ash is mostly cristobalite, at reported levels up to 20%. The UK government’s Chief Medical Officer, referring to Montserrat, has suggested that long-term exposure to high levels of volcanic ash could lead to silicosis. These concerns have prompted government-funded investigations into the potential toxicity of well characterized volcanic ash samples from Montserrat. Given the well established toxicity of cristobalite, particular attention was paid to the amount of this mineral in the ash samples. Three ash samples were tested: (1) a vulcanian eruption ash, (2) ash released in a domecollapse pyroclastic flow, and (3) ash from a major vulcanian explosion that was wind-transported to, and deposited on, the neighbouring island of Antigua. Comparative toxicological studies were carried out on respirable preparations of these three samples together with appropriate control mineral dusts that matched the major components of the Montserrat samples: anorthite, labradorite, cristobalite/ obsidian and cristobalite. Alpha quartz (DQ12) was the positive control. All samples, including the controls, were characterized to establish particle-size distributions, particle morphologies, and to confirm the mineralogy. Rats were challenged with 1 mg via intratracheal instillation, and groups sacrificed at three time points (1, 3 and 9 weeks). Health assessment was made by examining endpoints of increasing lung damage such as inflammation, permeability (oedema), changes in epithelium, and increase in the size of broncho-thoracic lymph nodes. The data indicate that Montserrat respirable ash, derived from dome collapse pyroclastic flows or vulcanian explosions, has minimal acute bioreactivity in the lung. The feldspar standards showed low bioreactivity, in stark contrast to the cristobalite standard that showed progressive increases in lung damage. These results suggest that either the mass of cristobalite present in the Montserrat ash was insufficient to cause an effect in the lung, or the cristobalite in the ash was, for some as yet unknown reason, markedly less bioreactive than our pure cristobalite standard.
Carbonatitic melts in cuboid diamonds from Udachnaya kimberlite pipe (Yakutia): evidence from vibrational spectroscopy
Authors: Zedgenizov D. A. , Kagi H. , Shatsky V. S. , Sobolev N. V. 
Published: August 2004

AbstractMicro-inclusions (1 –10 μm) in 55 diamonds of cubic habit from the Udachnaya kimberlite pipe have been studied using vibrational spectroscopy. This has revealed a multiphase assemblage in cuboid diamonds from the Udachnaya kimberlite pipe. This assemblage includes carbonates, olivine, apatite, graphite, water and silicate glasses. The micro-inclusions preserve the high internal pressure and give confidence that the original materials were trapped during growth of the host diamond. The internal pressures, extrapolated to mantle temperatures, lie within the stability field of diamond and the relatively low temperatures are typical for the formation of cuboid diamonds. In contrast to previously reported data for African diamonds, the micro-inclusions in the cuboids from Udachnaya are extremely carbonatitic in composition (H2O/(H2O+CO2) ≈5 –20%) with the observed assemblage of microinclusions similar to some types of carbonatites. The low water and silica content testify that the material in the micro-inclusions of the Udachnaya diamonds was near-solidus carbonatitic melt. Vibrational spectroscopy has provided the evidence of carbonatitic melts in cuboid diamonds.
Iron and water losses from hydrous basalts contained in Au80Pd20capsules at high pressure and temperature
Authors: Hall L. J. , Brodie J. , Wood B. J. , Carroll M. R. 
Published: August 2004

AbstractWe have performed experiments to determine the extents to which Fe and H2O are lost from hydrous basaltic melts contained in Au80Pd20and graphite-lined Pt capsules at 0.7 –1 GPa and 1300–1350°C. All experiments were performed in the piston-cylinder apparatus. In order to minimize the possibility of rupture of the AuPd capsule and to control H2O loss we used a double-capsule method. The inner welded 2 mm diameter Au80Pd20capsule was placed inside a welded 3 mm diameter Pt capsule, the intervening space being packed with hydrous sample. Loss of FeO* from the sample was found to be ≤4% relative in both the Au80Pd20and graphite-lined Pt capsules in experiments of up to 24 h duration. Loss of H2O is greater and it depends on the oxidation state of the starting materials and the nature of the capsule. For starting mixes fired at 1 logfO2unit above the quartz-fayalite-magnetite (QFM) buffer at 1 atm, H2O loss from Au80Pd20capsules averaged 9% relative. Starting mixes fired at 1 logfO2unit below the QFM buffer at 1atm lost, on average, 32% of their H2O when run in Au80Pd20capsules at high pressure. All samples run in graphite-lined Pt capsules experienced dramatic H2O loss, averaging 52% relative, irrespective of initial oxidation state. We conclude that Au80Pd20capsules are suitable for high-pressure hydrous melting experiments and that the sample loses very little Fe. In order to minimize H2O-loss, however, it is important that the starting materials be relatively oxidized.
Magmatic evolution of the Gaussberg lamproite (Antarctica): volatile content and glass composition
Authors: Salvioli-Mariani E. , Toscani L. , Bersani D. 
Published: August 2004

AbstractThe lamproite of Gaussberg is an ultrapotassic rock where leucite, olivine and clinopyroxene microphenocrysts occur in a glass-rich groundmass, containing microliths of leucite, clinopyroxene, apatite, phlogopite and rare K-richterite.Abundant silicate melt inclusions occur in olivine, leucite and, rarely, in clinopyroxene microphenocrysts. Raman investigations on melt inclusions showed the presence of pure CO2 in the shrinkage bubbles. On the other hand, the glass of the groundmass is CO2-poor and contains up to 0.70 wt.% of dissolved H2O, as estimated by infrared spectra. It is inferred that CO2 was released at every stage of evolution of the lamproite magma (CO2-rich shrinkage bubbles), whereas H2O was retained for longer in the liquid. At Gaussberg, CO2 seems to have a major role at relatively high pressure where it favoured the crystallization of H2O-poor microphenocrysts; the uprise of the magma to the surface decreased the solubility of CO2 and caused a relative increase in water activity. As a consequence, phlogopite and K-richterite appeared in the groundmass.The glass composition of both the groundmass and melt inclusions suggests different evolutions for the residual liquids of the investigated samples. Sample G886 shows the typical evolution of a lamproite magma, where the residual liquid evolves toward peralkaline and Na-rich composition and crystallizes K-richterite in the latest stage. Sample G895 derives from mixing/mingling of different batches of magma; effectively glasses from melt inclusions in leucite and clinopyroxene are more alkaline than those found in early crystallized olivine. Leucite and clinopyroxene crystallized early from a relatively more alkaline batch of lamproite magma and, successively, a less alkaline, olivinebearing magma batch assimilated them during its rise to the surface.
The structure and thermal expansion behaviour of ikaite, CaCO3. 6H2O, from T = 114 to T = 293 K
Authors: Lennie A. R. , Tang C. C. , Thompson S. P. 
Published: August 2004

AbstractThe hydrous calcium carbonate mineral ikaite (CaCO3.6H2O) forms in nature at low temperature in carbonate- and Ca-rich waters. Ikaite crystallizes in the spacegroup C2/c, and consists of CaCO3.6H2O units with Ca ions coordinated by eight oxygens, six from H2O and two from the carbonate group. Hydrogen bonding links CaCO3.6H2O moieties to form the crystal structure.We have used synchrotron X-ray powder diffraction at T = 243 K to refine the monoclinic structure of ikaite, and have measured unit-cell parameters of ikaite between T = 114 K and T = 293 K. Anisotropic thermal expansion in ikaite is evident, with the smallest relative increase occurring along the b direction parallel to 2-fold axes. The contribution of hydrogen bonding to thermal expansion is assessed by comparison of our data with previously published data for deuterated ikaite, ice and gypsum. Ikaite exhibits a coefficient of volume expansion intermediate between that of ice (Ih) and of deuterated gypsum (CaSO4.2D2O) between T = 114 K and T = 293 K.
The crystal structures of kidwellite and ‘laubmannite’, two complex fibrous iron phosphates
Authors: Kolitsch U. 
Published: August 2004

AbstractThe previously unknown, complex crystal structures of two fibrous ferric iron phosphate minerals have been solved using single-crystal X-ray diffraction data. The structure of a slightly arsenatian kidwellite has been refined in space group P2/c (a = 20.117(4), b = 5.185(1), c = 13.978(3)Å, β = 107.07(3)°, V = 1393.8(5)Å3, Z = 2) to R1 = 5.21%; a revision of both space group symmetry and chemical formula is proposed. The idealized formula is Na(Fe3+,M)9+x(OH)11(H2O)3(PO4)6, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.3. The structure of a slightly arsenatian ‘laubmannite’ (as defined by Moore, 1970) has been refined in space group Pbcm (a = 5.172(1), b = 13.999(3), c = 31.083(6)Å, V = 2250.5(8)Å3, Z = 4) to R1 = 3.14%. The revised, idealized formula is (Fe3+,Fe2+,M)8+x(OH,H2O)9(-H2O)2(PO4)5, where M = Fe3+, Cu2+ or other metal cation, and x ≈ 0.1. The framework structures of both minerals are similar. Dominant building units are dimers composed of face- and edge-sharing FeO6 octahedra. Whereas kidwellite contains an additional trimer built of three corner-sharing FeO6 octahedra, ‘laubmannite’ instead contains a dimer built of two corner-sharing FeO6 octahedra. Kidwellite contains only trivalent iron, while one of the Fe sites in ‘laubmannite’ is occupied by a mixture of Fe3+ and Fe2+ in a 1:1 ratio. In both structures, the FeO6-based building units are linked via corners to PO4 tetrahedra; the M sites are located in narrow channels and have very low occupancies (~2 to 7%) and strongly distorted [6]- or [5+1]-coordinations. Close structural relations between kidwellite and ‘laubmannite’, and other fibrous iron phosphates explain observations of epitaxial intergrowths of them.
New insight into the crystal structure of orthorhombic edingtonite: evidence for a split Ba site
Authors: Gatta G. D. , Boffa Ballaran T. 
Published: August 2004

AbstractOrthorhombic edingtonite has been found coexisting with tetragonal edingtonite in a specimen from Ice River, British Columbia, Canada.We report data on the composition and crystal structure of the orthorhombic sample. Lattice parameters are:a= 9.5341(6),b= 9.6446(6),c= 6.5108(7)Å, V = 598.68(8)Å3. The crystal structure was refined in space groupP21212 toR1= 1.8% using 879 observed reflections. For the first time, evidence for splitting of the extra-framework Ba site in two different sites (Ba1, Ba2), ~0.37 Å apart, is demonstrated. A comparison with the published crystal structures of tetragonal and orthorhombic edingtonite is made.The present result supports the suggestion that the two edingtonite phases are a consequence of different nucleation phenomena and not different physicochemical conditions.
Cinnabar, livingstonite, stibnite and pyrite in Pliocene silica sinter from Northland, New Zealand
Authors: Hampton W. A. , White G. P. , O. Hoskin P. W. , L. Browne P. R. , Rodgers K. A. 
Published: August 2004

AbstractSilica sinter masses in the southern portion of the Pliocene Puhipuhi geothermal field of Northland, New Zealand, have recrystallized to microcrystalline quartz and moganite but many primary depositional fabrics of the sinters can still be recognized. Finely disseminated cinnabar, acicular stibnite, pyrite framboids and minor livingstonite are distributed through both massive sinter and stromatolitic fabrics with sulphide mineralization extending from fractured rocks about former spring vents into less disturbed sinter layers. The deposition of sulphides in the sinters is part of a continuum of mineralization resulting from the former hydrothermal regime and which extends to depth in the extinct geothermal system. Periodic changes in the hydrology, such as repeated fracturing following fracture sealing facilitated episodic sulphide deposition. Mercury is considered to have travelled in the liquid phase with antimony and precipitated directly as cinnabar. Remobilization of the sulphides, along with the recrystallization of the sinter masses, have produced complex textural relations. The multifaceted paragenesis of the sulphides is reflected in the range of their minor and trace element compositions revealed by electron microprobe analyses.
Quantitative high-resolution cathodoluminescence spectroscopy of smithsonite
Authors: Götte T. , Richter D. K. 
Published: August 2004

AbstractFive smithsonite samples from locations in Germany, Mexico and Namibia have been investigated with cathodoluminescence (CL) spectroscopy and trace-element analyses. As with other carbonates, the CL properties of smithsonite are mainly controlled by Mn2+- and Fe2+-incorporation, because these elements are the most important activator and quencher species, respectively. Additional trace elements may have either a quenching effect (Cu) or have only small or no influence (Ca, Pb). A linear correlation exists between the Mn content and the intensity of the Mn-emission band in smithsonite, which can be quantified, if the Cl intensity is related to the number of moles of Mn rather than the weight fraction. A correlation between the Cl intensity and the Mn concentration, which is valid for all trigonal carbonates, is obtained from the published results of calcite, dolomite and smithsonite. Matrix effects due to the different chemical composition of the carbonate minerals seem to be of lesser importance.
Nomenclature of amphiboles: additions and revisions to the International Mineralogical Association's amphibole nomenclature
Authors: Leake B. E. , Woolley A. R. , Birch W. D. , J. Burke E. A. , Ferraris G. , Grice J. D. , Hawthorne F. C. , Kisch H. J. , Krivovichev V. G. , Schumacher J. C. , N. Stephenson N. C. , W. Whittaker E. J. 
Published: August 2004

AbstractThe introduction of a fifth amphibole group, the Na-Ca-Mg-Fe-Mn-Li group, defined by 0.50 < B(Mg,Fe2+,Mn2+,Li) < 1.50 and 0.50 ≤ B(Ca,Na) ≤ 1.50 a.f.p.u. (atoms per formula unit), with members whittakerite and ottoliniite, has been required by recent discoveries of B(LiNa) amphiboles. This, and other new discoveries, such as sodicpedrizite (which, here, is changed slightly, but significantly, from the original idealized formula), necessitate amendments to the IMA 1997 definitions of the Mg-Fe-Mn-Li, calcic, sodic-calcic and sodic groups. The discovery of obertiite and the finding of an incompatibility in the IMA 1997 subdivision of the sodic group, requires further amendments within the sodic group. All these changes, which have IMA approval, are summarized.
Aurivilliusite, Hg2+HgI+OI, a new mineral species from the Clear Creek claim, San Benito County, California, USA
Authors: Roberts A. C. , Stirling J. A. R. , Criddle A. J. , Dunning G. E. , Spratt J. 
Published: August 2004

AbstractAurivilliusite, ideally Hg2+Hg1+OI, is monoclinic, C 2/c, with unit-cell parameters refined from X-ray powder data: a= 17.580(6), b= 6.979(1), c= 6.693(3)Å, β = 101.71(4)°, V = 804.0(5)Å3, a:b:c= 2.5190:1:0.9590,Z = 8. The strongest six lines of the X-ray powder-diffraction pattern [din Å (I )(hkl)] are: 8.547(70)(200), 3.275(100)(002), 2.993(80)(21), 2.873(80)(600), 2.404(50b)(02, 421, 22) and 1.878(50)(23). This extremely rare mineral was collected from a small prospect pit near the longabandoned Clear Creek mercury mine, New Idria district, San Benito County, California, USA. It is intimately intermixed with another new undefined Hg-O-I phase (‘CCUK-15’), and is also closely associated with native mercury, cinnabar and edgarbaileyite in a host rock principally composed of quartz and magnesite. Aurivilliusite occurs in a cm-wide quartz vein predominantly as irregular-shaped thin patches ‘splattered’ on the quartz surface; patches vary in size from 10–20 μm up to 0.5 mm. The only known subhedral platy brightly reflecting crystal fragment, with major ﹛100﹜ form and distinct ﹛100﹜ cleavage, did not exceed 0.2 mm in longest dimension. The mineral is dark grey-black with a dark red-brown streak. Physical properties include: metallic lustre; opaque; non-fluorescent; brittle; uneven fracture; calculated density 8.96 g/cm3 (empirical formula), 8.99 g/cm3 (ideal formula). In polished section in plane-polarized reflected light, aurivilliusite resembles cinnabar, is extremely light sensitive, shows twinning and no internal reflections, and exhibits an unusual ‘red light’ coalescing phenomena. Averaged and corrected results of electron-microprobe analyses yielded HgO 40.10, Hg2O 38.62, I 22.76, Br 0.22, Cl 0.06, sum 101.76, less O = I + Br + Cl –1.46, total 100.30 wt.%, corresponding to Hg1.002+Hg1.001+ O1.01(I0.97Br0.01Cl0.01)Σ0.99, based on O + I + Br + Cl = 2 atoms per formula unit (a.p.f.u.). The original value for Hg, 74.27 wt.%, was partitioned in a HgO:Hg2O ratio of 1:1 after the discovery of the crystal-structure paper dealing with the synthetic equivalent of aurivilliusite. The mineral name is in honour of the late Dr Karin Aurivillius (1920 –1982), chemistcrystallographer at the University of Lund, Sweden, for her significant contributions to the crystal chemistry of Hg-bearing inorganic compounds. Aurivilliusite is related chemically to terlinguaite, Hg2+Hg1+OCl, but has a different structure and X-ray characteristics.
Micron- to nano-scale intergrowths among members of the cuprobismutite series and paděraite: HRTEM and microanalytical evidence
Authors: Ciobanu C. L. , Pring A. , Cook N. J. 
Published: August 2004

AbstractCoherent intergrowths, at the lattice scale, between cuprobismutite (N= 2) and structurally related paděraite along both major axes (15 Å and 17 Å repeats) of the two minerals are reported within skarn from Ocna de Fier, Romania. The structural subunit, DTD, 3 layers of paděraite, is involved at interfaces of the two minerals along the 15 Å repeat, as well as in transposition of 1 paděraite unit to 2 cuprobismutite units along the 17 Å repeat in slip defects. Lattice images obtained by HRTEM across intervals of 200–400 nm show short- to long-range stacking sequences of cuprobismutite and padeÏ raite ribbons. Such nanoscale slabs mimic mm-scale intergrowths observed in back-scattered electron images at three orders of magnitude greater. These slabs are compositionally equivalent to intermediaries in the cuprobismutite-paděraite range encountered during microanalysis. Hodrushite (N= 1.5) is identified in the mm-scale intergrowths, but its absence in the lattice images indicates that, in this case, formation of polysomes between structurally related phases is favoured instead of stacking disorder among cuprobismutite homologues. The tendency for short-range ordering and semi-periodic occurrence of polysomes suggests they are the result of an oscillatory chemical signal with periodicity varying from one to three repeats of 15 Å, rather than simple ‘accidents’ or irregular structural defects. Lead distribution along the polysomes is modelled as an output signal modulated by the periodicity of stacking sequences, with Pb carried within the D units of paděraite. This type of modulator acts as a patterning operator activated by chemical waves with amplitudes that encompass the chemical difference between the minerals. Conversion of the paděraite structural subunit DTD to the C unit of cuprobismutite, conserving interval width, emphasizes that polysomatic modularity also assists interference of chemical signals with opposite amplitudes. Observed coarsening of lattice-scale intergrowths up to the mm-scale implies coupling between diffusion-controlled structural modulation, and rhythmic precipitation at the skarn front during crystallization.