bluuebunny/crossref_metadata_2025_split huggingface dataset:
1966 ash eruption of the carbonatite volcano Oldoinyo Lengai: mineralogy of lapilli and mixing of silicate and carbonate magmas
Authors: Dawson J. B. , Smith J. V. , Steele I. M. 
Published: December 2006

AbstractLapilli from the August 1966 eruption of the carbonatite volcano Oldoinyo Lengai consist of carbonate-cemented aggregates of (i) mono- and poly-mineralic fragments of ijolitic rocks, (ii) single grains and clusters of euhedral nepheline, Ti-andradite, and Ti-magnetite, and (iii) corroded pyroxene and wollastonite grains surrounded by coronas containing combeite, melilite, Ca-silicates (possibly larnite and rankinite), and rounded bodies of submicrometre intergrowths with complex bulk compositions dominated by Na,K,Ca-phosphate-carbonate and alkali-iron-sulphide-carbonate. The (ii,iii) materials, together with abundant Na-carbonate, sylvite and fluorite occurring as cement and shells in the lapilli, are attributed to mixing and incomplete reaction of ijolite and carbonatite magmas during the explosive eruption. The rounded submicrometre intergrowths are interpreted as the quench products of two types of immiscible liquids whose properties should be studied by controlled synthesis.
Rare-earth minerals yttrian zirconolite and allanite-(Ce) and associated minerals from Koberg mine, Bergslagen, Sweden
Authors: Zakrzewski M. A. , Lustenhouwer W. J. , Nugteren H. J. , Williams C. T. 
Published: December 2006

AbstractA study of mine dump material from Koberg, Bergslagen, Sweden has revealed a varied mineral assemblage, including Zr-, REE-, Th- and U-bearing minerals associated with the sulphide ore deposit. Detailed descriptions and microprobe analyses are presented of the rare earth minerals yttrian zirconolite and allanite-(Ce), and the zirconium oxide baddeleyite. Yttrian zirconolite is patchily zoned in the actinide elements Th and U, and the low analytical totals suggest the presence of several weight per cent of H2O. The implications of these features with respect to synthetic zirconolite in SYNROC and to radioactive waste management are briefly discussed. Chemical zoning of individual REE in yttrian zirconolite is described and the REE distribution compared with those of zirconolites from other localities. Allanite-(Ce) is generally unzoned, but contains REE-rich rims which are considered to be sub-micron intergrowths of allanite plus a bastnäisite-type mineral phase. The MgO content of allanite-(Ce) is unusually high and appears to be a characteristic feature of allanite from other cerium and mineral occurrences of Central Sweden. The rare earth minerals at Koberg are interpretated as having been formed as a result of localized remobilization of elements including Ti and Zr with H2O- and CO2-rich fluids.
The geochemistry and cryptic zonation of pyrochlore from San Vicente, Cape Verde Islands
Authors: Hodgson N. A. , Le Bas M. J. 
Published: December 2006

AbstractZr-rich pyrochlore crystals in carbonatite from San Vicente (Cape Verdes Islands) show cryptic, concentric and rhythmic chemical zonation with Ca increasing and Ti, U and Zr decreasing towards the rims. In one carbonatite, taken from the Camile dyke, previously undocumented cryptic sector zonation of Ti, U and Zr is also observed in these crystals. The chemical variation is investigated by wavelength-dispersive electron microprobe, with both single spot and crystal map analyses.The concentric and rhythmic zonation, marked by element substitution, was generated by magma heterogeneity and/or element diffusion kinetics, but it is suggested that the sector zonation, marked by differential site substitution, was governed by protosite variation between octahedral and cubic faces.
Wagnerite with isokite from the Benson Mines, west-central Adirondack Highlands, New York
Authors: Jaffe Howard W. , Hall Leo M. , Evans Howard T. 
Published: December 2006

AbstractThe rare fluophosphate minerals wagnerite, ideally Mg2(PO4)F, and isokite, ideally CaMg(PO4)F, are intimately associated with magnetite-hematite deposits in sillimanite-, garnet-, and pyroxene-rich paragneisses and migmatites at the Benson Mines, near Star Lake in the west-central Adirondack Highlands of New York State. Coarsely crystalline wagnerite occurs in lenticular masses, typically 4 × 8 cm, delineated by sharply cross-cutting, sinuous, 2 cm-wide veins of fine-grained, fibrous to platy isokite and granular fluorapatite. These also penetrate transverse fractures across wagnerite lenses. Isokite formed from the introduction of Ca- and O-rich hydrothermal solutions into wagnerite. Both minerals are monoclinic: wagnerite crystallises in space group P21/a with a = 11.945, b = 12.717, c = 9.70 Å, β = 108.18°, V = 1400.2 Å3, D(calc) = 3.291 g/cm3 for Z = 16; isokite crystallises in space group A2/a with a = 6.909, b = 8.746, c = 6.518 Å, β = 112.20°, V = 364.7 Å3, D(calc) = 3.248 for Z = 4. Optical properties for wagnerite are: α = 1.5845, β = 1.5875, γ = 1.6010, 2V = 51°(calc.) disp = r < v weak, absorption α < β > γ with α = col., β = pale yel., γ = v. pale yel. For isokite only a mean index of refraction, n = 1.598, could be measured. Wet chemical analysis of wagnerite containing a calculated 11.4% of isokite as fine lamellae, gave the formula:
Mineralogy and cryptic layering of the Kunene anorthosite complex of SW Angola and Namibia
Authors: Silva Zenaide C. G. 
Published: December 2006

AbstractThe gabbro-anorthosite complex of SW Angola and Namibia (Kunene Complex) is dominated by anorthosite-troctolite cumulates. Other broadly gabbroic rock types are subordinate. An-rich plagioclase (max. An85) and Fo-rich olivine (max. Fo79) are common in the western area of the complex with plagioclase becoming gradually less anorthitic (min. An45) and olivine less forsteritic (min. Fo62) toward the east. This cryptic change is more pronounced in the northern half of the complex where rocks are darker, fresh, and the rhythmic layering is also more conspicuous. Within the white 'massive' anorthosite type, which is largely restricted to the southern half of the intrusion, cryptic layering is less pronounced. Textures indicate that rocks cooled very slowly and the co-existing mineral compositions indicate re-equilibration to usually low temperatures.
Significance of the cumulate mineralogy of the Belhelvie mafic-ultramafic intrusion—comments on: Silicate mineralogy of the Belhelvie cumulates, NE Scotland, by W. J. Wadsworth
Authors: Boyd R. , Ashcroft W. A. 
Published: December 2006

AbstractNew data on the composition of cumulus phases in the Belhelvie intrusion presented by Wadsworth (1991) are discussed in the light of existing data and of knowledge on the form and internal structure of the intrusion. The relevance of the Rustenburg Layered suite of the Bushveld Complex as a model for the 'single intrusion' hypothesis for the layered basic intrusions in NE Scotland is examined: current knowledge of the Rustenburg Layered Suite and related intrusions suggests that similar crystallisation sequences of cumulus phases and ranges of cryptic variation do not give any case for a single intrusion hypothesis.
Högbomite in sapphirine-bearing rocks from the Bamble Sector, south Norway
Authors: Visser D. , Thijssen P. H. M. , Schumacher J. C. 
Published: December 2006

AbstractHögbomite is reported from two upper-amphibolite and granulite-facies, sapphirine-bearing, Al–Mg–Fe-rich and silica-poor lens-shaped layers within the Bamble Sector, south Norway. Primary assemblages, indicating peak metamorphic conditions of 773-844°C at 7 kbar (Mg–Fe exchange thermometry), are spinel–sapphirine–biotite–gedrite, spinel–corundum–sapphirine–cordierite and orthopyroxene–biotite–cordierite–plagioclase. Högbomite formed by hydrous alteration and oxidation of primary spinel and rutile and/or ilmenite according to the generalised reaction:Suggested conditions of högbomite formation are 550–620°C and 6–7 kbar. The högbomites contain 10.2–14.7 wt.% MgO, 04).3 wt.% ZnO, 58.9–62.1 wt.% Al2O3 and 15.6-17.6 wt.% Fe as FeO. The two högbomite may belong to different polytypes, as suggested by their differing TiO2 (9.9-10.1 versus 5.7–5.8 wt. %) and calculated Fe3+ – and H2O–contents. The partitioning of Zn between spinel and högbomite is not uniform and is considered to depend upon prevailing fo2 and aH2O.
Clinotobermorite, Ca5Si6(O,OH)18·5H2O, a new mineral from Fuka, Okayama Prefecture, Japan
Authors: Henmi C. , Kusachi I. 
Published: December 2006

AbstractClinotobermorite, Ca5Si6(O,OH)18·5H2O, has been found as a vein-forming mineral in gehlenitespurrite skarns at Fuka, Okayama Prefecture. It is associated with tobermorite, plombierite, apophyllite, and calcite. The clinotobermorite is colourless or white and occurs as tabular or acicular crystals. It is monoclinic with the space group Cc or C2/c. The unit cell dimensions are a 11.331, b 7.353, c 22.67 Å, β 96.59°. Microtwinning and stacking disorder on (001) are observed. On heating the clinotobermorite at 300°C the 002 spacing is reduced from 11.3 to 9.3 Å. Its refractive indices are α 1.575, β 1.580, γ 1.585, and the density 2.58 g/cm3 (meas.), 2.69 g/cm3 (calc). The Moh's hardness is 4.5. Calculation of the analytical data on the basis of six tetrahedral cations shows that this mineral has a simplified chemical formula Ca5.3Si6(O,OH,F)18·5H2O. The chemical composition and the unit cell are closely related to those of tobermorite. It is most likely that clinotobermorite is a low-temperature polymorph of tobermorite.
Transformation of chernikovite into meta-uranocircite II, Ba(UO2)2(PO4)2.6H2O and study of its solubility
Authors: Vochten R. F. , Van Haverbeke L. , Van Springel K. 
Published: December 2006

AbstractChernikovite, (H3O)2(UO2)2(PO4)2, was synthesized and subsequently transformed into metauranocircite II, Ba(UO2)2(PO4)2.6H2O, by ion-exchange experiments. The crystals are lemon-yellow and strongly fluorescent. From solubility data a mean pKs value at 25°C was determined as 51.79 ± 0.21. For a cell volume of 16.31.7 Å3 and Z = 4 the density was calculated as 3.970 g/cm3 whereas the measured density is 3.964 g/cm 3. The X-ray powder pattern shows the following strongest lines: 3.609(60)(114), 3.470(60)(123), 2.9272(90)(132)2.9006(90)(312), 2.6065(80)(116), 2.4581(75)(233), 2.2015(100)(143 ; 143), 2.1869(100) (241 ; 226 ;241).
High pressures and the structure of solids of geochemical and geophysical interest
Authors: Goodman C. H. L. 
Published: December 2006

AbstractPressures of 10 GPa and above can bring about phase transformations in many oxides, an effect of great interest to geochemists and geophysicists. We can interpret such behaviour as due to the differential compressibility of 'anion' and 'cation' leading to a progressive rise in radius ratio with pressure, and hence, on the classic crystallochemical picture, eventually to an increase in co-ordination number (though with complications which make prediction difficult). More generally, pressure affects Gibbs free energy G directly; for oxides a pressure of 5 GPa gives, very roughly, the same contribution to G as 100°C in temperature (though with opposite sign). Thus high pressure significantly affects the shape and structure of phase diagrams, showing increasingly important effects above, say, 10 GPa—but again prediction can be difficult. However these two complementary approaches to the effects of pressure, helpful though they can be conceptually, are 'crystal-based' and totally neglect another rather littleknown but potentially important effect--the formation of amorphous solids; 'polymers' and glasses. Since amorphous materials are 'non-equilibrium' they are not readily dealt with theoretically; also, since they are difficult to detect by standard crystallographic techniques, they can be overlooked experimentally. The pressure-induced formation of amorphous solids could have significant implications for both geochemistry and geophysics.
The first occurrence of qandilite in Russia
Authors: Oktyabrsky R. A. , Shcheka S. A. , Lennikov A. M. , Afanasyeva T. B. 
Published: December 2006

AbstractNumerous small octahedra of a black, brittle, magnetic mineral were found in calciphyre and brucite marble, occurring in the northern part of the exocontact zone of the Kondyor ultramafic-alkalic massif (south-eastern part of the Aldan Shield, 250 km north west of sea port Ayan). Their composition corresponds to the group from titanium magnesioferrite (11.53% TiO2) to titanium-rich magnesian spinel (27.34% TiO2), similar to spinellide found in Greenland (Gittins et al., 1982) and in Iraq (Al-Hermezi, 1985) and approved by the Commission on New Minerals as a new mineral named qandilite. Hardness, specific gravity, and reflectance of Kondyor qandilite are similar to those of the Iraq mineral. Peaks of IR-absorption spectra are equal to 580-590 cm−1 (v2) and 431-438 cm−1 (v2). There is a positive correlation between lattice parameters and the amount of Mg2TiO4: from 8.368 Å at 26.6% to 8.429 Å at 60.4%. Kondyor qandilite crystallized together with geikielite, oxidized alumina spinel (8.55% Fe2O3, ftotal : 16.5%), periclase, and forsterite.
Manganese-rich calcic amphiboles of the tremolite-ferro-actinolite series
Authors: Damman A. H. , Lustenhouwer W. J. 
Published: December 2006

AbstractAmphiboles of the tremolite-ferro-actinolite series from the Bergslagen district in central Sweden have between 0 and 46% of their M1-M3 sites occupied by Mn. These amphiboles are divided into two groups; (1) a group characterised by Mn (M1-M3) > (Mg or Fe) (M1-M3), and (2) a group with much lower contents of Mn (M1-M3), showing the following chemical characteristics: (a) Mn (M1-M3) never exceeds Fe (M1-M3); (b) in Mg-rich members of the group [Mg (M1-M3) > (Mn or Fe) (M1- M3)], the highest amounts of Mn (M1-M3) occur in amphiboles with about 2.20 Mg (M1-M3) per formula unit (pfu); in Fe-rich members of the group Fe [(M1-M3) > (Mg or Mn) (M1-M3)] high amounts of Mn (M1-M3) [> 0.4 Mn (MI-M3)] pfu only occur in amphiboles with >3.40 Fe (M1-M3) pfu; (d) the lowest amounts of Mn (M1-M3) occur in amphiboles with Mg (M1-M3) = Fe (M1-M3).Mn (M4) increases with increasing amounts of Mn (M1-M3), indicating that solid solution towards the tirodite-dannemorite series is enhanced by incorporation of Mn (M1-M3).
Geochemistry of orbicular diorite from the Grenville Front zone, eastern Labrador
Authors: Victor Owen J. 
Published: December 2006

AbstractOrbicules in diorite from the Grenville Front zone of eastern Labrador consist of biotite- and/or hornblende-studded, dioritic cores enclosed by fine-grained shell structures alternately enriched and depleted in biotite. The orbicules occur in a mesocratic, quartz-bearing matrix. Epidote of inferred magmatic origin occurs in all parts of the rock. Plagioclase in the matrix is relatively sodic, and biotite more ferroan than in the orbicules, suggesting that the matrix material has the most evolved composition, and crystallized last.The diorite is unusually aluminous (orbicules: 24.9-27.4 wt.% Al2O3; matrix: 22.4-23.6% Al2O3) and calcic (orbicules: 7.0-8.4 wt.% CaO; matrix: 6.0-6.9% CaO); it shows a positive Eu anomaly, and has elevated Sr concentrations (1800-2500 ppm Sr), demonstrating that, compositionally, it resembles a plagioclase cumulate. Mass-balance calculations suggest that the orbicule cores had a crystal/melt ratio of ≤5. This accounts for the extreme fractionation of the rock (e.g., in orbicules, Zr <5 ppm). Compared with fractional crystallization patterns, variation diagrams show counter-trends (e.g. the siliceous matrix contains elevated TiO2) or scatter for several components, suggesting that the crystal/melt ratio governed some of the geochemical characteristics of the diorite.The presence of coarse mafic clots containing primary epidote, biotite and/or hornblende testify to an elevated water content in the orbieule cores. The shell magma apparently formed as a result of the interaction of supercooled orbicule core fluids with the matrix magma, and tended to serve as a reservoir for alkalis and Fe. Alkalis and Ca diffused in opposite directions, possibly as a result of a temperature gradient at the orbicule/matrix interface. This, however, requires decoupling of the thermodiffusional behaviour of alkalis and femic components in hydrated intermediate magma, which contrasts with documented Soret diffusion in mafic systems.The solidification of the shell magma prior, to the orbicule cores and matrix is attributed to dewatering, consistent with the fine grain size of the shell structures. Except where remobilized core material has disrupted the shells, the cores crystallized in isolation from the matrix, which fractionated toward a more evolved composition.
Relation between graphitization of organic matter and clay mineralogy, Silurian black shales in Central Spain
Authors: Barrenechea J. F. , Rodas M. , Arche A. 
Published: December 2006

AbstractA horizon containing graphite in the Early Silurian slates of the Eastern Central System, Central Spain, has been studied. The carbonaceous slates contain quartz, muscovite, graphitized organic matter, plagioclase, pyrite and apatite; and the slates above the graphite horizon contain quartz, phengite, plagioclase and chlorite. The origin of the graphite is related to a period of very slow accumulation rate, anoxic seafloors deep-water upwellings and plankton blooms. The chlorite and graphite are mutually exclusive and by' using the chlori te AlIV content and the graphite Co parameter, the conditions of metamorphism were calculated to be 300 ± 20°C and 1.5-2 kbar.
Reflected-light microscope and SEM/EMP observations on the behaviour of aurostibite (AuSb2) during amalgamation
Authors: Jedwab Jacques , Chuva Jose Mendes , Poot Eric 
Published: December 2006

AbstractThe Mobale gold mine (Kivu, Zaire) has been worked since 1923, but the presence of aurostibite in the ore was recognized only very recently. The discovery of the mineral has also led to the recognition of its heretofore unsuspected reactivity during the amalgamation ore dressing operations. At the surface of aurostibite a layer of up to 30 μm thickness forms which has an overall brown colour and a low reflectivity, and is composed of several variegated, concentric zones. These zones contain gold, mercury, antimony and oxygen, with traces of iron and arsenic. Oxygen is present with a concentration range of 2-4 wt.% (20-30 at.%). The zones form at the expense of aurostibite, according to micrographical criteria. In complex grains formed of gold-arsenopyrite-galena-aurostibite, only aurostibite is affected by the formation of the external brown zones. Later pure gold veneers are deposited on the outermost surface of the brown layers during the processing of the ore. The newly discovered features of processed aurostibite could explain some of the difficulties met with during the dressing of antirnonian gold ores.
The crystal chemistry of cowlesite
Authors: Vezzalini Giovanna , Artioli Gilberto , Quartieri Simona , Foy Harry 
Published: December 2006

AbstractCowlesite specimens from nine new occurrences in Northern Ireland and from eight localities previously reported in the literature, were crystal-chemically characterised. The chemical data for a total of 25 samples indicate a composition close to the stoichiometric formula for cowlesite and a very limited compositional range. X-ray powder diffraction spectra were performed on 8 samples. The crystallographic unit cell permit a proper indexing of the X-ray powder diffraction patterns as orthorhombic, unit cell constants close to a 23.3, b 30.6, c 25.0 Å and doubled with respect to those originally reported in literature. The powder pattern and the TG curve arc reported for an unidentified mineral species associated with cowlesite in one of the samples from Northern Ireland.
Zr-rich garnet and Zr- and Th-rich perovskite from the Polino carbonatite, Italy
Authors: Lupini L. , Williams C. T. , Woolley A. R. 
Published: December 2006

AbstractTh- and Zr-bearing perovskite and Zr-rich Ti garnet are described from the Polino calcite carbonatite, Italy. The garnets contain 6.05-7.50 wt.% ZrO2 in cores and up to 15.80 wt.% in rims. Silicon is low in these garnets and substantial Al and Fe 3+ has been assigned to the tetrahedral sites. A strong correlation of Si with Zr from published data suggests the possibility that some Zr may also be tetrahedrally coordinated. However, the chemistry alone does not constrain the site distribution of Fe, Ti, Zr and Mg unambiguously. The perovskites are very unusual in containing 2.81-3.27 wt.% ZrO2 and 1.48-1.71 wt.% ThO2. For comparison, new analyses are presented of the zirconium garnet kimzeyite and coexisting perovskite from the type locality at Magnet Cove.
Cannonite, Bi2O(OH)2SO4, a new mineral from Marysvale, Utah, USA
Authors: Stanley C. J. , Roberts A. C. , Harris D. C. , Criddle A. J. , Szymañski J. T. 
Published: December 2006

AbstractCannonite, ideally Bi2O(OH)2SO4, is a new mineral from the Tunnel Extension mine, Ohio Mining District, Marysvale, Utah, USA. It occurs mostly as intergrown crystalline aggregates (<1 mm) of subhedral to euhedral equant to prismatic crystals (<200 μm) in cavities in quartz gangue. Other associated minerals are cuprobismutite, bismuthinite, and covelline. Cannonite is colourless and transparent with an adamantine lustre and white streak. It is brittle with an uneven to conchoidal fracture. In reflected light it is low reflecting, weakly to moderately bireflectant and weakly anisotropic. Internal reflections (colourless to white) are abundant. Measured reflectance values in air and oil are tabulated. Colour values relative to the CIE illuminant C for R1 and R2 in air respectively are: Y% 10.4, 11.7; Lambdad 475,475; Pe% 2.6, 3.0. Calculated refractive indices at 589 nm: R1 1.91 and R2 1.99. VHN100 229 (range 183-280); calculated Mohs hardness is 4.X-ray studies show that cannonite is monoclinic with space group P21/c and a 7.700(3), b 13.839(6), c 5.686(2) Å, β 109.11(3) ° It has a cell volume of 572.5(4) Å3 with Z = 4. Dcalc. is 6.515 g/cm3. The strongest six lines of the X-ray powder pattern are [d in Å (I) (hkl)] 3.206 (100) (221); 1.984 (90) (340, 152); 2.924 (70) (131); 3.644 (60) (111); 3.466 (60) (040); 2.782 (50) (112). Averaged probe analyses gave the empirical formula Bi1.99O(OH1.04)2S0.99O4 on the basis of 7 oxygen atoms. The name is for Benjamin Bartlett Cannon of Seattle, Washington, United States of America.