bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compositional zoning in sodic amphiboles from the blueschist facies
Authors: Wood Robert Muir 
Published: December 2006

SummaryThe sodic amphiboles possess two independent chemical substitution series (Fe3+-Al and Fe2+-Mg) that combine to provide a ‘plane’ of compositions. Yet at no single T and P are compositions covering the whole plane stable: (i) pure riebeckite exists under low-P conditions but breaks down in normal blueschists to give deerite; (ii) ferro-glaucophane is in competition at all except the lowest blueschist temperatures with almandine garnet; (iii) magnesio-riebeckite is stable at high-T and low-P but within the blueschist facies is replaced by the alternative higher density aegirine-talc assemblage; and (iv) glaucophane is stable only at high-P.At higher T and P than those of the blueschists, competition from NaCa pyroxenes, garnets, and deerite first erodes, and then removes, nearly all sodic amphibole compositions. At low-P the normal sodic amphibole-forming reactions from stilpnomelane and chlorite (in the presence of iron oxides, albite, etc.) produce an initial ‘rie-beckitic’ amphibole that subsequently becomes more glaucophanitic with increasing P. Under certain conditions, perhaps connected with hydrous fluid overpressures, these reactions become transposed such that crossitic compositions become replaced whilst ferroglaucophane to glancophane compositions remain stable.
The crystal structure of kogarkoite, Na3SO4F
Authors: Fanfani L. , Giuseppetti G. , Tadini C. , Zanazzi P. F. 
Published: December 2006

SummaryThe crystal structure of synthetic kogarkoite has been determined from X-ray data collected on an automatic diffractometer. The refinement was performed by a least-squares method employing anisotropic thermal parameters. The 3157 reflections with I > 3σ(I) converged to a conventional R value of 0.033. The cell content is 12 Na3SO4F, the space-group P21/m, a = 18.074, b = 6.958, c = 11.443 Å, β = 107.71°.Kogarkoite presents a marked trigonal subcell with c′ corresponding to [102] of the monoclinic cell. The tridimensional framework can be considered built up by nine differently stacked layers of Na atoms approximately perpendicular to the c′ axis (five sheets are present in galeite, six in sulphohalite, and seven in schairerite). The very close structural relationships between these minerals are discussed.
Chemical variation of clinopyroxene phenocrysts from the trachybasaltic lavas of Mount Etna, Sicily
Authors: Duncan A. M. , Preston R. M. F. 
Published: December 2006

SummaryThe chemical variation of clinopyroxene phenocrysts from the trachybasaltic lavas of Etna volcano is described. The phenocrysts show a limited, but distinct trend in chemical variation from calcic-augite in the hawaiites to augite in the benmoreites. The trend of this variation is unusual, being one of Mg-enrichment with differentiation of the magma. Ca shows a steady decrease in the clinopyroxenes from the hawaiites to the benmoreites. Na, however, shows little chemical variation in the pyroxenes. The trace element chemistry is briefly examined. The clinopyroxenes show well-developed oscillatory and sector zoning. The basal {11} sectors are enriched in Si and Mg and depleted in Ti, Al, and Fe relative to the {100}, {110}, and {010} prism sectors.
Schieffelinite, a new lead tellurate-sulphate from Tombstone, Arizona
Authors: Williams Sidney A. 
Published: December 2006

SummaryFound at the Joe and Grand Central mines, Tombstone, Arizona, USA, in quartz gangue with girdite, rodalquilarite, bromargyrite, and gold. Crystals orthorhombic, tabular to scaly on {010} up to 1 mm; H = 2, colour white, Dmeas = 4.98 ± 0.12.Chemical analysis gave PbO 58.2 %, TeO3 28.6, SO3 6.8, H2O 4.7. Easily fusible to red-brown slag and soluble in cold, dilute acids.Crystals orthorhombic Cmcm; a = 9.67 Å, h = 19.56, c = 10.47. Strongest lines 9.778 (10), 3.426 (6), 3.250 (6B), 3.560 (5B), 3.338 (5), 3.033 (5), 2.934 (5), 2.603 (5). Dcalc = 5.15, Z = 16. Indices are α = 1.897, β = 1.940, γ = 1.942, 2Va = 24°; γ‖a, α‖b, β‖c.The mineral and name have been approved by the Commission on New Minerals and New Mineral Names, IMA.
Nomenclature of the phosphoferrite structure type: refinements of landesite and kryzhanovskite
Authors: Moore P. B. , Araki T. , Kampf A. R. 
Published: December 2006

SynopsisThe ideal end-members reddingite, Mn32+ H2 O)3(PO4)2, phosphoferrite, (H 2O)3(PO4)2, and kryzhanovskite, (OH)3(PO4)2 form a complex triple series. Similarities in crystal axes and pronounced differences in site preferences have led to erroneous indexing of the powder data and subsequent errors in cell refinements. Writing the general formula M(1)M(2)2[(H2O),(OH)]3(PO4)2, the following end-member names apply:Type landesite,Ca0.4Mg1.2(OH)3.2(H2O)8.8(PO4)8.0, has a = 9.458(3) Å, b = 10.185(2) Å, c = 8.543(2) Å, space group Pbna. R = 5.2% for 1821 independent reflexions (Mo-Kα radiation). The distance averages are M(1)-O = 2.098 Å, M(2)-O = 2.205 Å, P-O = 1.539 Å. Cotype kryzhanovskite,Ca0.5Mg0.4(OH)7.3(H4O)4.7(PO4)8.0, has a = 9.450(2) Å, b = 10.013(2), c = 8.179(2). R = 7.2% for 1,703 independent reflexions (Mo-Kα radiation). The distance averages are M(1)-O = 2.017 Å, M(2)-O = 2.115, P-O = 1.542.Computed powder pattern intensities from the structure data admitted extensive revisions of earlier published Miller indices and revised powder data are presented.
Johnsomervilleite, a new transition-metal phosphate mineral from the Loch Quoich area, Scotland
Authors: Livingstone A. 
Published: December 2006

SummaryJohnsomervilleite, Na10Ca6Mg18(Fe, Mn)25 (PO4)36 has Z = 3, a 15.00 Å, c 42.75 Å and cell volume 8330 Å3 and is a new rhombohedral species occurring in two metamorphic segregation pods in Moine gneiss of kyanite-sillimanite grade. Associated minerals are apatite, jahnsite, graftonite, mineral A, phosphosiderite, rockbridgeite, mitridatite, and vivianite. It is dark brown, brittle, and glassy, H = 4½, D = 3·35 (calc. 3.41) with a perfect basal (?) cleavage. Eight electron probe analyses are given and d spacings for 50 lines. The mineral, which is a Mg-Fe analogue of fillowite, is named after the late Mr J. M. Somerville who presented a specimen of garnet-quartz rock, which contained the new species, to the Royal Scottish Museum.
Glushinskite, a naturally occurring magnesium oxalate
Authors: Wilson M. J. , Jones D. , Russell J. D. 
Published: December 2006

SummaryGlushinskite, a dihydrate of magnesium oxalate, occurs at the lichen/rock interface on serpentinite colonized by Lecanora atra at Mill of Johnston, near Insch in north-east Scotland. It is found in a creamy white layer intermingled with the hyphae of the lichen fungus. It consists of crystals mainly 2 to 5 µm in size showing a distorted pyramidal form, often with curved and striated faces. X-ray, infrared, and chemical data are given.
Origin of Ba-rich sanidine megacrysts in a porphyry from Papua New Guinea
Authors: Nixon P. H. , Chapman N. A. , Smith J. V. 
Published: December 2006

SummaryA Miocene porphyry belonging to the sheshonite association contains 7 cm sanidine megacrysts in a groundmass of microphenocrysts of labradoritebytownite, augite, sporadic hastingsite, magnetite, sphene, K feldspar, apatite, Ca zeolite and calcite. The megacrysts (Or78–94) are enriched in BaO (≃ 2.0 wt%) and SrO relative to the groundmass. Although mineralogr and texture suggest that the megacrysts were suspended in a liquid, now represented by the groundmass, calculated liquid densities except for dry melts are less than those observed for the megacrysts and it is concluded that the original magma contained very little water. It possibly originated in a subduction zone with the main hycration taking place at shallow levels of intrusion during contact with groundwater. This produced zeolitization of the feldspars and may have played a part in the K enrichment at the margins of the sanidine megacrysts.
Geochemistry and mineralogy of weathered basalt from Morvern, Scotland
Authors: Bain D. C. , Ritchie P. F. S. , Clark D. R. , Duthie D. M. L. 
Published: December 2006

SummaryThe chemical, mineralogical, and textural changes involved in the weathering of basalt have been traced through various stages from fresh rock (which has a cation exchange capacity of 10 meq/100 g due to the presence of a swelling chlorite mineral) to reddened basaltic rubble consisting of interstratified montmorillonite-illite, hematite, and anatase. The cation exchange capacities of the rocks increase progressively with the formation of secondary clay from labradorite as Al, Fe, and Ti accumulate and Si, Mg, Ca, and Na are depleted—much of the K is retained in the secondary clay mineral. The weathering is considered to be contemporaneous with the formation of the Antrim bauxites but not so intense.
Arsenohauchecornite and tellurohauchecornite: new minerals in the hauchecornite group
Authors: Gait Robert I. , Harris Donald C. 
Published: December 2006

SummaryArsenohauchecornite, Ni9BiAsS8, and tellurohauchecornite, Ni9BiTeS8 from the Sudbury area, Ontario, are now recognized as distinct mineral species in the Hauchecornite Group and not as varieties as described previously. Descriptions of these two minerals are given, summarized from Gait and Harris (1972).
Incorporation of impurities in tridymites from a used silica brick
Authors: Schneider H. , Wohlleben K. , Majdic A. 
Published: December 2006

SummaryThe incorporation of impurities in tridymites taken from a used silica brick have been studied by means of a high-resolution microprobe, X-ray fluorescence, X-ray diffractometry, and optical microscopy. The bulk impurity content of the brick changes strongly from the hot zone (4.7 wt%) to the colder part of the brick (7.6 wt%), indicating material transport along the temperature gradient. The transport medium for migration processes is probably a melt occurring in narrow veins between large tridymite crystals at high temperatures. The average impurity contents of homogeneous tridymite single crystals are 0.49 wt% in the hot zone of the brick and 0.81 wt% in the cold zone. Al2O3, TiO2, and Na2O are main impurity constituents; the tridymites do not contain significant amounts of Fe2O3 or CaO. The a parameters of tridymites decrease by about 0.26% from 4.9837 Å to 4.9709 Å from the hot zone to the cold zone of the brick and the c dimension shows a smaller decrease (0.11 %) from 8.2023 Å to 8.1933 Å.
The chemical stability of mendipite, diaboleïte, chloroxiphite, and cumengéite, and their relationships to other secondary lead(II) minerals
Authors: Alun Humphreys D. , Thomas John H. , Williams Peter A. , Symes Robert F. 
Published: December 2006

SummaryThe chemical stabilities of mendipite, Pb3O2Cl2, diaboleïte, Pb2CuCl2(OH)4, chloroxiphite, Pb3CuCl2O2(OH)2, and cumengéite, Pb19Cu24Cl42 (OH)44, have been determined in aqueous solution at 298.2 K. Values of standard Gibbs free energy of formation, ΔGf°, for the four minerals are −740, −1160, −1129, and −15163±20 kJ mol−1 respectively. These values have been used to construct the stability diagram shown in fig. I which illustrates their relationships to each other and to the minerals cotunnite, PbCl2, paralaurionite, PbOHCl, and litharge, PbO. This diagram shows that mendipite occupies a large stability field and should readily form from cold, aqueous, mineralizing solutions containing variable amounts of lead and chloride ions, and over a broad pH range. The formation of paralaurionite and of cotunnite requires a considerable increase in chloride ion concentration, although paralaurionite can crystallize under much less extreme conditions than cotunnite. The encroachment of the copper minerals on to the stability fields of those mineral phases containing lead(II) only is significant even at very low relative activities of cupric ion. Chloroxiphite has a large stability field, and at given concentrations of cupric ion, diaboleïte is stable at relatively high aCl−. Cumengéite will only form at high concentrations of chloride ion.
Hydrobasaluminite and basaluminite from Chickerell, Dorset
Authors: Clayton T. 
Published: December 2006

SynopsisHydrobasaluminite and basaluminite, two hydrated basic aluminium sulphate minerals have been found in the weathering zone of the Oxford Clay at Crook Hill Brickyard, Chickerell, near Weymouth, Dorset. Hydrobasaluminite occurs as a reaction rim surrounding carbonate concretions, and is believed to have resulted from the neutralization of aluminium-bearing acid sulphate solutions formed by oxidation of pyrite and subsequent leaching of clay. Basaluminite is found only on concretions that have fallen to the floor of the pit, suggesting that it is formed as a dehydration product of hydrobasaluminite.Chemical analysis of hydrobasaluminite yields the composition 2Al2O3 · SO3 · 20H2O, although this almost certainly includes substantial amounts of adsorbed water. Chemical analysis of basaluminite gives the composition 2Al2O3 · SO3 · 9H2O, which is equivalent to a formula of Al4SO4(OH)10 · 4H2O if it assumed that water is present only as water molecules or hydroxyl ions. The sulphate ions are readily exchangeable. Electron-optical and X-ray powder diffraction data show the minerals to be monoclinic rather than hexagonal as previously reported. Indexed X-ray powder patterns give unit-cell parameters of a = 14.911(5) Å, b = 9.993(2) Å, c = 13.640(5) Å, β = 112.40(4)° for hydrobasaluminite and a = 14.857(3) Å, b = 10.011(3) Å, c = 11.086(7) Å, β = 122.28(3)° for basaluminite. The specific gravity of basaluminite is found to be 2.10 and Z = 4.Hydrobasaluminite dehydrates irreversibly to basaluminite under normal laboratory conditions, but can be preserved indefinitely at high relative humidity. A study of the dehydration of basaluminite using a diffractometer heating-stage shows the presence of three further distinct hydration states as well as interstratified intermediates. The dehydrations occur topotactically and involve major changes in the c* direction only. DTA and TGA curves can be interpreted in terms of progressive dehydration.It is suggested that the minerals possess a layer structure, probably containing gibbsite-like double-hydroxide layers with interlayer sulphate ions and water molecules. The data also seem to show a close structural relationship between basaluminite and the hydrated basic aluminium carbonate mineral, scarbroite.
Redskin Granite: a rare-metal-rich Precambrian pluton, Colorado, USA
Authors: Desborough G. A. , Ludington S. D. , Sharp W. N. 
Published: December 2006

SummaryThe Precambrian Redskin stock is a high-silica alkalic granite that forms a late pluton related to the 1000 Ma-old Pikes Peak batholith. Zircon, fluorite, fluocerite, ilmenorutile, columbite, biotite, magnetite, and hematite are the most abundant accessory minerals. Thorite, monazite, and xenotime are sparse, and cassiterite and topaz very rare. The principal residences of Sn, Nb, and Ta are ilmenorutile and columbite. The occurrence of cassiterite intergrown with biotite and columbite and the high contents of Nb and Ta in cassiterite are evidence that cassiterite is also a primary mineral. The high concentrations of certain trace elements indicate a high degree of fractionation of magma prior to emplacement of the Redskin Granite. An extremely low crystallization temperature for the granite is indicated by the compositions of albite and K-feldspars, the presence of Fe-rich dioctahedral mica, the absence of Ti in magnetite, and the low content of Ti in biotite. This low crystallization temperature seems due largely to the high concentrations of F, Rb, and other volatile elements in the magma.
Chromian jadeite, phengite, pumpellyite, and lawsonite in a high–pressure metamorphosed gabbro from the French Alps
Authors: Mevel C. , Kienast J. R. 
Published: December 2006

SummarySmall ophiolitic bodies are enclosed in the calcschists of the Piemont zone (western Alps). They have been metamorphosed in the blueschist facies during the alpine orogeny. One of them, the Roche Noire massif, includes gabbro breccias. The magmatic mineralogy of the gabbro was plagioclase + clinopyroxene + minor chromite. There was no chemical homogenization during metamorphism because of the lack of penetrative deformation and on the site of previous chromites, chromium-rich high-pressure and low-temperature minerals (jadeite, phengite, pumpellyite, and lawsonite) were formed. The Al ⇌ Cr substitution does not affect other P- and T-dependent substitutions.
Carbonatite magmas
Authors: Le Bas M. J. 
Published: December 2006

AbstractNormal carbonatite magmas are characteristically associated with ijolites and produce extensive fenitization by alkali metasomatism, commonly feldspathization or phlogopitization. The sequence of carbonatites developed from this magma are characterized by igneous isotopic ratios, high contents of incompatible elements, their distinctive pattern of differentiation from sövite to beforsite, and a late-stage rare-earth element, baryte, fluorite mineralization. Carbonatite rock is composed mainly of calcite, but fluid inclusion and related data indicate that the original magma was highly alkaline and chemically similar to that known at Oldoinyo Lengai volcano in Tanzania. It is suggested that this carbonatite magma is secondary magma produced from carbonated nephelinite magma by liquid immiscibility. Carbonatite magma can also occur associated with kimberlites but these carbonatites are alkali-poor and do not produce the characteristic fenitization.
Chemical and mineralogical changes during basalt-seawater interaction: Site 223, Leg 23, D.S.D.P., north-west Indian Ocean
Authors: Papavassiliou C. Th. , Cosgrove M. E. 
Published: December 2006

AbstractThe development of low- and hightemperature alteration products in a 23 m section of ocean-floor basalts is described. Analcime, calcite and dioctahedral smectite are ubiquitous. Trioctahedral smectite, smectite-chlorite mixed layers, chabazite and scolecite occur in the deeper sections with Fe3+ oxides/hydroxides progressively becoming more abundant in the upper regions. The upper layers of the sequence show marked chemical reduction. High-temperature chemical changes include Na and Mg enrichment accompanied by Ca and Fe2+ losses. Superimposed low temperature changes include gains in Fe3+ K, Li, and Rb, and losses in Na, Ca, and Fe2+ Many trace elements also show consistent behaviour.
Unit cell data of serpentine group minerals
Authors: Bayliss Peter 
Published: December 2006

AbstractLeast-squares analyses of powder X-ray diffraction data have been undertaken for minerals and synthetics of composition (Mg,Mn,Fe,Co,Ni)3−xSi2O5 (OH)4. New polytypes of nepouite and greenalite have been established, and eleven new or altered unit cells have been calculated. Baumite is an unnecessary varietal name for a manganoan ferroan lizardite-1T; tosalite is an unnecessary varietal name for a manganoan greenalite; clinochrysotile is an unnecessary polytype name for chrysotile-2Mc1; orthochrysotile is an unnecessary polytype name for chrysotile-2Orc1; ortho-antigorite and ortho-hexagonal serpentine are unnecessary names for lizardite-6T1; and septechlorite should not be used. The powder data of the serpentine group are in general, poor.
Rare-earth partition between allanite and glass in the obsidian of Sandy Braes, Northern Ireland
Authors: Brooks C. K. , Henderson P. , Rønsbo J. G. 
Published: December 2006

AbstractAllanite phenocrysts and co-existing glass from the perlitic obsidian of Sandy Braes have been analysed for nine rare earths (RE), uranium, and thorium by instrumental neutron activation analysis and for the major elements by electron microprobe. The chondritenormalized RE plot for the allanite shows a steep slope with a negative Eu anomaly. Allanite/glass partition coefficients show a smooth variation with ionic radius (except for Eu), the variation spanning two orders of magnitude. The partitioning behaviour, which is distinct from that shown by the RE in sphene, apatite, and zircon, can be explained by the allanite structure. The pronounced affinity of the light RE for allanite makes this an important mineral in considerations of RE concentrations during the evolution of granitic liquids.
Thermal aspects of the origin of Hebridean Tertiary acid magmas. I. An experimental study of partial fusion of Lewisian gneisses and Torridonian sediments
Authors: Thompson R. N. 
Published: December 2006

AbstractThermal aspects of the conflicting hypotheses that the acid magmas of the British Tertiary Igneous Province were generated by either fractional crystallization of basic magmas or partial fusion of country rocks around basic intrusions are investigated by combining petrological and experimental data. Sparse large xenoliths (up to 12 m2 outcrops) of Lewisian gneiss occur in the ferrodiorite member of the Marscoite Suite in the Western Redhills Eocene intrusive complex of Skye. Most of the blocks are of granodioritic-tonalitic gneiss which is very similar to the grey gneisses of the northern and southern regions of the mainland Lewisian. One is a two-pyroxene basic granulite, closely resembling in petrography and composition the granulite-facies basic gneisses of the central region of the Scottish mainland Lewisian. During Tertiary thermal metamorphism the xenoliths recrystallized patchily to pyroxene hornfelses and up to 50% of melting occurred in any parts of blocks that were rich in alkali feldspar and quartz. Microprobe analyses of intergrown Ca-rich and Ca-poor pyroxenes in a hornfelsed ultramafic mica pyroxenite lens within a leucogneiss block give a calculated temperature of 950 °C for the Tertiary metamorphism. Melting experiments at 1 kb PH2O were carried out on leucocratic and mesocratic Lewisian gneisses (from the xenoliths), Torridonian arkose and shale. Extensive melting of the leucogneiss and arkose, to peraluminous liquids, occurs within a few degrees above their solidus (715 °C). The silicate liquidus of the leucogneiss is at 930 °C. Microprobe analyses of the glass products of melting experiments (mostly of leucogneiss) show that liquid composition trends during progressive melting are consistent with theoretical equilibria in the synthetic system Ab-Or-An-Qz-H2O. Partial fusion in the Skye Lewisian gneiss xenoliths took place at a water vapour pressure of a few hundred bars, probably under water-undersaturated conditions.
Garnet-biotite-cordierite thermometry and barometry in the Cashel thermal aureole, Connemara, Ireland
Authors: Treloar Peter J. 
Published: December 2006

AbstractA number of geothermometers and geobarometers involving coexisting garnet, biotite, and cordierite have been used to calculate the pressures and temperatures of metamorphism of the Cashel thermal aureole in Connemara. Temperatures from the garnetbiotite thermometer show a wide variation between calibrations, and are markedly different from those obtained from the garnet-ordierite thermometer. These variations, together with the possibility of extensive reequilibration between garnet and cordierite rims and biotite, indicate that the use of exchange reaction thermometry, for these rocks at least, may be invalid. The various calibrations of the garnet-cordierite-sillimanitequartz geobarometer give reasonably consistent pressure estimates which, after allowance for partial pressures of water, indicate pressures of metamorphism of about 5±1 kb.
Zoning in garnets from the mainland Lewisian
Authors: Kerr A. 
Published: December 2006

AbstractTwo types of zoning are found in garnets from Lewisian rocks. One is due to retrogression of an earlier homogeneous garnet while the other results from growth (or equilibration) during falling temperatures. Both zoning patterns result from metamorphism during or after the Dionard tectonic phase of the Laxfordian event.