bluuebunny/crossref_metadata_2025_split huggingface dataset:
Petrology of Mg-Mn amphibole-bearing assemblages in manganese silicate rocks of the Sausar Group, India
Authors: Dasgupta Somnath , Bhattacharya P. K. , Chattopadhyay G. , Banerjee H. , Majumdar N. , Fukuoka M. , Roy Supriya 
Published: December 2006

AbstractMg-Mn amphibole (tirodite), with or without pyroxmangite in the total absence of pyroxenes and high-calcic pyroxenoids, occurs in the Mn silicate rocks of the Sausar Group, India. The rocks were metamorphosed to amphibolite facies condition (T ∼ 650°C, P ∼ 6 kbar). Tirodite-pyroxmangite pairs developed in both carbonate-free and rhodochrosite-bearing assemblages. Also tirodite coexists with either kutnahorite or manganoan calcite in the absence of pyroxmangite. Mineral reactions inferred from modal abundances and compositions of the phases indicate stabilization of the amphibole alone from a bivalent cation-bearing residual unbuffered XCO2 system with XMn < 0.3. On the other hand, tirodite-pyroxmangite pairs appeared in unbuffered low to intermediate XCO2 assemblages with XMn > 0.35. Pyroxenes and high-calcic pyroxenoids did not appear in the present situation, though they occur elsewhere in rocks with broadly similar contents of immobile components. Closely associated assemblages of diverse mineralogy suggest that the XMn and XCO2, rather than the physical conditions of metamorphism, are the decisive factors in promoting the observed phase assemblages.
Trace element variation in the leucogranites within the main Galway Granite, Connemara, Ireland
Authors: Feely M. , Madden J. S. 
Published: December 2006

AbstractSix hundred and forty four gamma-ray spectrometer assays of U and Th obtained within the late Caledonian Galway Granite western Ireland are presented. The data cover the range of granodiorites, adamellites and leucogranites (Murvey Granite) present in the batholith. There is an overall increase in U and Th abundances with petrological evolution. The broad scatter of values that characterizes the Murvey Granite reflects the geographically separate occurrences of this leucogranite. Rubidium and strontium data imply varying degrees of fractionation among these separate Murvey Granite occurrences. Y andHREEare notably enriched in the Murvey granite at Costelloe which also contains the highest Th levels amongst the leucogranites. Thorite, uraninite, monazite and Y-zircon are present in this leucogranite and are responsible for the observed enrichments in U, Th, Y andHREE.
Orbicular gabbro from near Baskil, southeastern Turkey
Authors: Yazgan Evren , Mason Roger 
Published: December 2006

AbstractThe first occurrence of orbicular rocks in Turkey is reported. They are gabbros in a dyke in the Baskil island-arc magmatic suite, of the southern branch of the Alpine-Himalayan chain. The orbicules have lithologically varied cores, regular shells of troctolitic composition, with a radial arrangement of olivine and plagioclase crystals, and a matrix of vari-textured gabbro. Rock and mineral analyses indicate that magmatic crystallization began near the inner margin of the troctolitic shells. Metamorphic hydration of minerals in cores, shells and matrix followed directly after the later stages of magmatic crystallization, as part of a continuous process, and thus a magmatic-metamorphic origin for the orbicules is proposed. Alternative hypotheses for the development of the orbicules are discussed: one involving the development of a protocrystalline magma shell, the other rapid crystallization during upward migration of xenolith-bearing magma.
Hydrothermal subsilicic sodium gedrite from the Gåsborn area, West Bergslagen, central Sweden
Authors: Damman A. 
Published: December 2006

AbstractSubsilicic sodium gedrite has been found in a hydrothermal vein together with sekaninaite (Fe-cordierite), andalusite, plagioclase, topaz, sillimanite, quartz, biotite, magnetite, ilmenite, hercynite, wolframite, pyrrhotite, chalcopyrite and pyrite. This vein is part of a hydrothermal vein system consisting predominantly of quartz-feldspar veins, some of which contain andatusite, sekaninaite, biotite, muscovite, fluorite and accessory oxides and sulphides, which was formed during the later stages of crystallization of a high-level anorogenic Svecofennian granite. Petrographic observations suggest the following crystallization sequence for the quartz-feldspar veins: plagioclase-quartz-andalusite-sekaninaite-microcline-biotite-albite-oxides and sulphides-muscovite-fluorite, and for the subsilicic sodium gedrite-bearing vein: andalusite-sekaninaite-subsilicic sodium gedrite-biotite-quartz-albite-sillimanite-topaz-oxides and sulphides. Electron microprobe analysis revealed that all subsilicic sodium gedrite is relatively homogeneous with only the following compositional variation: Na(A) 0.57–0.81, Aliv 2.31–2.57, XMg 0.15–0.21. The temperature (T) for the formation of the hydrothermal vein system is estimated at 550–600°C and the pressure (P) is estimated to be less than 3 kbar.
Roggianite: revised chemical formula and zeolitic properties
Authors: Passaglia E. , Vezzalini Giovanna 
Published: December 2006

AbstractThe holotype roggianite from Alpe Rosso (Novara, Italy) has been chemically re-analysed using modern analytical procedures (microprobe, atomic absorption spectrophotometer, TG analyses) and tested for its zeolitic behaviour. When compared with that given in the original description, the new chemical composition shows an appreciable amount of Be and a different Si/Al ratio. On the basis of its structural data, the chemical formula here proposed for roggianite is: (Ca14.24Sr0.01Na0.37K0.56)Σ15.18[(Be5.29Al14.92Si27.79)Σ48O89.96(OH)14](OH)2·33.68H2OAn accurate powder pattern, index taking into account the structural factors, is also given. Since the mineral showed an almost complete rehydration after heating to 750°C and an appreciable ion exchange capacity, it must be considered as belonging to the zeolitic group of minerals, and, in this frame, it represents the first and up to now the only zeolite with Be as fundamental constituent and, like partheite, with OH groups in the framework.
The crystal structure of non-stoichiometric Eu-anorthite: an explanation of the Eu-positive anomaly
Authors: Kimata Mitsuyoshi 
Published: December 2006

AbstractSynthetic Eu-anorthite of the alkali feldspar structure type has been refined toRw= 4.7% using 3-D counter diffractometer data and full-matrix least-squares methods. The chemical composition of the feldspar is Eu0.92Al1.76Si2.24O8, based on both occupancy refinement of the Eu atom site and estimation of the Al/Si distribution calculated from the meanT-Obond length. The unit cell parameters area= 8.373(1),b= 12.959(1),c= 7.124(1) Å, and β = 115.51(1)° and the symmetry is enhanced toC2/m. Mean bond lengths areT(1)-O = 1.677 Å,T(2)-O = 1.668 Å, and Eu-O = 2.721 Å. The average Al/Si distribution over theT(1) andT(2) sites calculated from the meanT-Obond length is in fairly good agreement with an estimate of the Al content from the bond strength calculation; the Al partition is calculated ast1= 0.47 andt2= 0.41 respectively. Summing the bond strengths of these Eu and partially disordered Al/Si cations approximates to electrostatic neutrality for the anion content of the feldspar structure, indicating that this synthetic Eu feldspar can be non-stoichiometric, signifying vacancies on the alkali cation site.Plagioclase and melilite generally show a positive Eu anomaly. A fair insight into the driving force of this anomaly can be afforded by the crystallo-chemical affinities of Eu2+and Eu3+cations to the crystal structures of their host minerals; (1) ioinic radius, (2) electrostatic charge balance and (3) tolerance for non-stoichiometry of the crystal structure.
Petrogenetic Processes Associated with Intermediate and Silicic Magmatism in the Oslo Rift, South-East Norway
Authors: Rasmussen E. , Neumann E.-R. , Andersen T. , Sundvoll B. , Fjerdingstad V. , Stabel A. 
Published: December 2006

AbstractThe Permian magmatic province of the Oslo rift, south-east Norway, includes large volumes of felsic and silicic rocks. Based on their geochemical character, these rocks may be divided into two main groups. The Larvik larvikites (monzonites) are highly enriched in large ion lithophile elements (LILE) (e.g. 10–32 ppm Th. 8–15 ppm Ta), and have an initial 87Sr/86Sr of 0.70391 ± 5. The syenites and granites have moderate to high concentrations of LILE (e.g. 7–88 ppm Th, 4–25 ppm Ta), and initial 87Sr/86Sr ratios between 0.705 and 0.707. The Larvik larvikites and extrusive equivalents (rhomb porphyry lavas) have similar initial Sr isotope ratios to uncontaminated basalts and gabbros in the rift, and are believed to have a mantle origin. The higher initial 87Sr/86Sr ratios in the silicic than in the felsic rocks reflect a crustal component representing the intermediate or low crust. After intrusion into the upper crust, the major and traceelement concentrations of the silicic magmas were modified through fractional crystallization dominated by removal of alkali feldspar, and transport of elements with a fluid phase. The silicic magmas appear not to have interacted significantly with the side rock at this stage.
Gyrolite: Its Crystal Structure and Crystal Chemistry
Authors: Merlino Stefano 
Published: December 2006

AbstractThe crystal structure of gyrolite from Qarusait, Greenland, was solved and refined with the space group P and cell parameters a = 9.74(1), b = 9.74(1), c = 22.40(2)Å, α = 95.7(1)°, β = 91.5(1)°, γ = 120.0(1)°. The structure is built up by the stacking of the structural units already found in the crystal structure of reyerite (Merlino, 1972, 1988), namely tetrahedral sheets S1 and S2 and octahedral sheets O. The tetrahedral and octahedral sheets are connected by corner sharing to give rise to the complex layer which can be schematically described as 1OS2, where S2 and , as well as O and , are symmetry-related units. Successive complex layers with composition [Ca14Si23AlO60(OH)8]-5 are connected through an interlayer sheet made up by calcium and sodium cations and water molecules.The unit cell content NaCa16Si23AlO60(OH)8·14H2O, determined by the structural study, was confirmed by a chemical analysis, apart from the indication of a somewhat larger water content. The crystal chemistry of gyrolite is discussed on the basis of the present structural results and the chemical data given in the literature for gyrolite from different localities: the crystal chemical formula which accounts for most gyrolite samples is Ca16Si24O60(OH)8·(14+x)H2O, with 0 ⩽ x ⩽ 3.Stacking disorder, twinning and polytypic variants in gyrolite, as well as the structural relationships of gyrolite with truscottite, reyerite, fedorite and the synthetic phases K and Z are described and discussed.
Pottsite, a New Vanadate from Lander County, Nevada
Authors: Williams S. A. 
Published: December 2006

AbstractPottsite occurs in the oxide zone of a tungsten mine northwest of Potts, Lander County, Nevada, and is named for the locality. It occurs with scheelite, clinobisvanite, bismutite, and vanadinite. The colour is yellow, luster adamantine. Dobs. is 7.0, Dcalc. 7.31. Uniax (-) ω = 2.49, ɛ = 2.37. Microprobe analysis gave PbO 32.4, Bi2O3 34.0, V2O5 26.6; H2O by Penfield method 6.71% (total 99.71%), leading to HPbBi(VO4)2·2H2O. Crystals are tetragonal 14122, a = 11.084, c = 12.634Å. Strongest powder diffraction lines are 4.618 (9), 4.168 (3), 3.210 (4), 3.062 (10), 2.476 (4), 2.252 (3).
The Tertiary Kærven Syenite Complex, Kangerdlugssuaq, East Greenland: Mineral Chemistry and Geochemistry
Authors: Holm Paul Martin , Prægel Niels-Ole 
Published: December 2006

AbstractThe Kærven syenite complex, which reflects the hitherto earliest recorded stages in the Tertiary of East Greenland, outcrops in the middle reaches of the Kangerdlugssuaq Fjord as a peripheral intrusion to the Kangerdlugssuaq intrusion. The rocks of the Kærven complex range from syenite through alkali feldspar quartz-syenite to alkali feldspar granite. The general sequence of crystallization of the Kærven magmas was: alkali feldspar ± olivine(Fa96−99) ± plagioclase(An41−11), clinopyroxene (augite, ferrosalite, ferrohedenbergite), quartz and amphibole. Whole-rock major and trace-element data show coherent geochemical trends which suggest comagmatism. The data reveal that the Kærven rocks are distinct from the rocks from the adjacent Kangerdlugssuaq intrusion (e.g. higher TiO2, FeOT in low-SiO2 samples, lower Na2O, approx. constant Zr/Nb). The mineral chemistry supports this conclusion, as the Kærven samples typically have calcic amphiboles and clinopyroxenes with a very limited Na-enrichment in contrast to the sodic trends of the Kangerdlugssuaq intrusion. Normative feldspar compositions plot near to the Ab-Or cotectic in the Q-Ab-Or system and a maximum pressure of crystallization of 3–5 kbar with moderate to low PH2O is indicated.Trace elements preferently incorporated in plagioclase and alkali feldspar, i.e. Sr, Ba and Rb, show systematics which are not compatible with an evolution of the rock suite by crystal fractionation of these phases, though possibly alkali feldspar may be partially accumulated in a few very evolved rocks. Numerical calculations do not suggest a magmatic evolution by fractional crystallization of the observed phases. The variation of Sr, Ba and Rb as well as of the incompatible elements Nb, Zr and Th support a derivation of the rock suite mainly by mixing two components, a syenitic and a granitic end-member. It is concluded that magma mixing was the most significant process in the formation of the Kærven rock suite accompanied by some crystal fractionation. Evidence for crustal contamination is detected in a few samples from the outer part of the intrusion but has not affected the main suite of rocks.
Isocubanite, a New Definition of the Cubic Polymorph of Cubanite CuFe2S3
Authors: René Caye , Cervelle Bernard , Cesbron Fabien , Oudin Elisabeth , Picot Paul , Pillard François 
Published: December 2006

AbstractIsocubanite is a cubic polymorph of cubanite CuFe2S3, discovered in the submarine sulphide deposits of the East Pacific Rise (EPR) and the Red Sea, in association with chalcopyrite, pyrrhotine, pyrite, sphaterite or wurtzite and anhydrite. It was previously obtained artificially and mentioned as iss, ‘intermediate solid solution of CuFe2S3 composition’. Crystals are cubic with a = 5.303(3) Å and strongest lines in the X-ray powder pattern are 3.059 (10) 111, 1.876 (7) 220, 1.602 (5) 311. Euhedral grains range from a few microns up to 400 µm, with a Vickers microhardness of 175(25) kg/mm2 for P = 100 g. Isocubanite is usually intimately intergrown with iron- and zinc-rich chalcopyrite and is opaque with a metallic lustre and a bronze colour. Pinkish brown and isotropic in polished sections; reflectance values (SiC standard) are: 420 nm 22.73%, 460 nm 26.87, 500 nm 31.34, 540 nm 34.79, 580 nm 37.35, 620 nm 39.11,660 nm 40.32, 700 nm 41.33, 740 nm 41.91, 780 nm 42.50. Electron microprobe analyses gave (wt. %): Fe 41.64–42.49, Cu 20.79–21.52, Zn 0.77–1.09, S 35.49–35.82, corresponding to the formula (Cu,Zn)Fe2S3.Isocubanite is characteristic of high-temperature (> 200 °C) present-day submarine sulphide deposits where hot hydrothermal fluids are quenched by seawater as in EPR deposits or by cooler brines as in Atlantis II Deep, in the Red Sea; it is unstable and therefore unusual in fossil ores. This cubic phase was previously observed and described more or less accurately as cubic cubanite, cubanite II, chalcopyrrhotite and iss; the name isocubanite, proposed in order to clarify the nomenclature, and this new description, were approved by the IMA Commission on New Minerals and Mineral Names.
Silicic Magmas Derived by Fractional Crystallization from Miocene Minette, Elkhead Mountains, Colorado
Authors: Leat P. T. , Thompson R. N. , Morrison M. A. , Hendry G. L. , Dickin A. P. 
Published: December 2006

AbstractThe rock association of minette with silicic lavas and intrusions (granites, syenites, dacites) is a common geologic feature in both collisional and extensional tectonic settings. Considerable doubt exists as to whether a genetic link exists between these mafic and silicic rocks. We describe a Miocene sill from NW Colorado which is a clear example of a mixed magma consisting of originally-liquid inclusions of minette in a silicic trachydacite host. Chemical and Sr, Nd and Pb isotopic data are consistent with derivation of the silicic host magma of the sill dominantly by fractional crystallization of the minette magma. Correlations between the elemental compositions of the rock types and their Sr and Nd isotopic ratios imply minor assimilation of continental crust with relatively low values of both87Sr/86Sr and143Nd/144Nd, concomitantly with fractional crystallization. The parental minette magma was probably derived by partial melting of subcontinental lithospheric mantle. While the sill was emplaced in a rift-like tectonic setting, the chemical and isotopic composition of the lithosphere-derived minette magmas (and hence the silicic fractionates) was largely independent of this setting, but dependent upon the composition and age of the lithospheric mantle and crust.
Coupled Substitutions in Schorl-Dravite Tourmaline: New Evidence from SE Ireland
Authors: Gallagher V. 
Published: December 2006

AbstractAnalyses of tourmaline and coexisting muscovite in tourmaline-bearing rocks from SE Ireland indicate that the content of Si in tourmaline is not fixed but is dependent on bulk chemistry, varying inversely with Al. Zoning patterns within tourmaline reflect this and, despite theoretical objections, substitution of Si by Al in the tetrahedral site must occur in nature. Ti may also substitute for Si. Ca and Ti are generally involved in a coupled substitution. Estimates of the degree of alkali-defect and proton-loss substitution in SE Ireland tourmalines indicate that the former process is at least as important as the latter and that bulk chemistry is important in determining which substitution occurs. The general importance of alkali-defect substitution and Al⇌Si suggests that the most useful way to treat microprobe data for schorl-dravite tourmalines is to assume the presence of 3B and 4(OH) and calculate on the basis of 24.5 oxygen atoms.
Criddleite, TlAg2Au3Sb10S10, a New Gold-Bearing Mineral from Hemlo, Ontario, Canada
Authors: Harris Donald C. , Roberts Andrew C. , Gilles Laflamme J. H. , Stanley Chris J. 
Published: December 2006

AbstractCriddleite, ideally TlAg2Au3Sb10S10, is a rare constituent within the Hemlo gold deposit, Hemlo, Ontario, Canada. The mineral occurs as 20 to 50 µm-sized lath-like, tabular or anhedral grains usually surrounding or penetrating aurostibite, or associated with native antimony, native gold and stibnite. Criddleite is opaque with a metallic lustre and a black streak. It has been synthesized by reacting TlSbS2 and high purity Ag, Au, Sb and S in an evacuated silica glass tube at 400 °C. The measured density of the synthetic material is 6.86; the calculated density is 6.57 g/cm3. The difference is due to minor admixed aurostibite, native antimony and a dyscrasite-like phase within the charge. VHN25 is 94–129. Mohs hardness (calc.) = 3–3 ½. In reflected plane-polarized light in air, natural criddleite is weakly bireflectant with a discernible reflectance pleochroism from grey-blue to slightly greenish grey-blue. The mineral has a distinct to moderate anisotropy with rotation tints in shades of buff to slate grey. Reflectance spectra and colour values for both natural and synthetic criddleite are given. X-ray study showed that synthetic criddleite is monoclinic (pseudotetragonal) with refined unit-cell parameters a = 20.015(2), b = 8.075(2), c = 7.831(2) Å, β = 92.01(2)°, V = 1264.9 ± 1.0 Å3 and a:b:c = 2.4786: 1:0.9698. The space group choices are A2/m(12), A2(5) or Am(8), diffraction aspect A*/*. The seven strongest lines in the X-ray powder diffraction pattern [d in Å (I) (hkl)] are: 5.63(90) (011), 3.91(50) (002), 3.456(50) (320), 2.860(70) (700), 2.813(100) (022), 2.018(60) (040) and 1.959(70) (004). Electron microprobe analyses are reported of natural criddleite in five polished sections of drill core from four holes. The averaged empirical formulae, based on 26 atoms, are Tl0.92Ag1.99Au2.93Sb9.87S10.28 (natural) and Tl0.94Ag2.03Au2.89Sb9.76S10.38 (synthetic).
Quantitative colours of opaque minerals
Authors: Peckett A. 
Published: December 2006

AbstractAnisotropic opaque minerals viewed in reflected light microscopy show two sets of colours: the colours seen in plane polarized light which change as the section is rotated on the microscope stage, and the colours seen between crossed polars which change as the analyser is uncrossed. These latter colours are known variously as polarization colours or anisotropic rotation tints, but are here referred to as anisotropy colours. They are commonly a diagnostic aid to correct mineral identification. All these colours occur as a consequence of the dispersion of the relative permittivity (dielectric) tensor—the variation in the values of the tensor with wavelength of incident light and in low symmetry crystals, the variation in the directions of the principal axes of the tensor with wavelength.In this paper, it is shown that the colour seen in plane polarized light and the anisotropy colours can be predicted for any orientation of section, at any stage angle, and for any degree of uncrossing of the analyser by calculations based on the dielectric tensor values, and these predicted colours compare favourably with the observed values. Three minerals are studied in this paper as examples: stannite, covelline, and bournonite.
Sadanagaite and subsilicic ferroan pargasite from thermally metamorphosed rocks in the Nōgō-Hakusan area, central Japan
Authors: Sawaki Takayuki 
Published: December 2006

AbstractHigh-alumina subsilicic calcic amphiboles, including sadanagaite and subsilicic ferroan pargasite, are found in rock samples from the contact aureole in the Nōgō-Hakusan area, central Japan. They occur in the reaction zones between dark fragments and the surrounding crystalline limestone of the pyroxene hornfels facies zone. The dark fragments which underwent K-metasomatism are originally basaltic rocks. The sadanagaite and subsilicic ferroan pargasite have high Al2O3 (16–19 wt. %) and K2O (3.6–4.3 wt. %) contents. The Si value ranges from 5.38 to 5.64 and the total Al ranges from 3.10 to 3.43 when cation ratios are calculated on the basis of O = 23. The calculated unit cell parameters of sadanagaite are a 10.00 (1), b 18.06 (2), c 5.355 (4) Å, β105.52(7)°, V 932(1) Å3. The A-sites of the amphiboles is occupied almost entirely by K and Na; the amphiboles are saturated with the edenite component. The amphiboles show a larger extent of tschermakite-type substitution [(Mg,Fe)Si⇌AlAl] than does ordinary pargasite. Sadanagaite is probably stable at the temperature above the upper amphibolite facies.