bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synmetamorphic uranium mineralization from Tiraun, Graubünden, Switzerland
Authors: von Pechmann E. , Bianconi F. 
Published: December 2006

AbstractPetrographic, microscopic, and X-ray investigations of a uranium occurrence near Tiraun, Graubünden, Switzerland, are described. The uranium mineralization occurs in greenschist facies metamorphic rocks of the Tavetsch massif and consists essentially of uraninite of various habits with minor chalcopyrite, linnaeite, millerite, galena, marcasite, pyrite, hematite, magnetite, and skutterudite. The ore structure, characterized by concentrations along foliation planes, boudinage, and rotated (helicitic) textures of uraninite porphyroblasts, is indicative of a synmetamorphic (Alpine) remobilization, recrystallization and enrichment of the ore, which was probably derived from an original ‘protore’ in psephites and psammites (? sandstone-type mineralization) of at least Variscan age. The synmetamorphic emplacement of the ore took place under medium- to high-temperature conditions (approx. 350–400°C), as demonstrated by the lattice constants of the uraninite phases and by the ore paragenesis. Late to postmetamorphic tectonism resulted in a partial remobilization (over cm distances) and redistribution of the ore along veinlets that cut the foliation planes. The characteristics of the ore from Tiraun are similar to those from the synmetamorphic ore from Preit, northern Italy, as described by Cevales (1961).
The mineralogy and genesis of uranium in rhyolitic ignimbrites of precambrian age from Duobblon, Sweden
Authors: Smellie John A. T. 
Published: December 2006

AbstractThe Duobblon rhyolitic ignimbrites, of middle Precambrian age are 60 m thick. They consist of at least three flows with varying degrees of welding and have undergone devitrification, producing lithophysal and spherulitic textures. They are overlain by thick fluviatile red-bed-type conglomerates and sandstones, which in turn are capped by terrestrial acid volcanics.Uranium enrichments of up to 3000 ppm U occur within two or three peneconcordant tabular horizons which are mostly lithophysae-bearing. Fission-track investigations of the ignimbrites and overlying conglomerates and sandstones, which supplement earlier mineralogical studies, show that U occurs as fine pitchblende disseminations; as complex uranotitanates associated with Fe-Ti-Mn oxides; and as coatings associated with matrix sericite. Small amounts of O are present in such primary accessory minerals as sphene, apatite, and zircon.It is suggested that oxidizing U-bearing solutions, generated partly during devitrification of the ignimbrites and partly from the overlying volcano-sedimentary pile, produced the U enrichments with later sulphide deposition, along the more permeable lithophysal horizons in the ignimbrites.
Lattice structural variation in K-feldspar megacrysts of associated charnockite and alkali granite
Authors: Iball D. R. , Hubbard F. H. 
Published: December 2006

AbstractThe perthite megacrysts from charnockitic and non-charnockitic members of a sialic intrusive complex in the Varberg area of south-west Sweden have been investigated by powder X-ray diffraction. The extent of Al/Si order in the K-feldspar host lattices of the megacrysts is restricted in all but the major alkali granite differentiate. A direct relationship between the hydration state of the containing rock and the degree of order of the megacryst lattices is indicated. High lattice strain is common to all the megacrysts but decreases progressively with increasing triclinicity.
Atomic arrangements on the twin boundaries of crystals of calcite and aragonite
Authors: Wooster W. A. 
Published: December 2006

AbstractBy constructing ball-and-spoke models an attempt has been made to arrive at the atomic arrangements on the twin boundaries of four twins of calcite and one of aragonite. The Miller indices of the twins of calcite are (111), (110), (100) and (11). The twin plane in aragonite is (110). Each of the models of calcite twins has the same plane for twin plane and composition plane, and in each case it is a true mirror plane. Aragonite has a pseudo glide plane parallel to (110) gliding in the [001] direction. By making this pseudo symmetry element into a true glide plane a good model of the twin is obtained. In the (111), (110) and (100) twins of calcite all the CO3 groups in the composition plane are parallel to it. In the (11) twin the composition plane contains only CO3 groups and these are perpendicular to it.
Chromian mica from Sierra Nevada, Spain
Authors: Martín-Rabios J. D. , Rodriguez-Gallego M. 
Published: December 2006

SynopsisEmerald green chromian 2M1 mica occurs in metamorphosed and metasomatized limestones, related to serpentinic rocks from Sierra Nevada, Spain. Chemical analysis gave: SiO2 44.51, Al2O3 27.60, TiO2 0.17, Cr2O3 3.35, Fe2O3 1.76, FeO 0.07, MnO 0.00, MgO 8.59, Li2O 0.03, Rb2O 0.01, BaO 0.01, CaO 1.71, Na2O 0.40, K2O 7.86, H2O 4.21 = 100.28. Optic properties are: pleochroism X blue, Y green, Z bluish green; refractive indices: α=1.562, β=1.611, γ=1.616 (yellow light); inclined dispersion, r > v. Orientation: second order mica. Refined parameters are a = 5.2116(6), b = 9.045(2), c = 19.97(2)Å, β = 95.7(3)°. The structure is discussed and an order in the octahedral M(1) sites is observed, but no ordering in the tetrahedral T(1) and T(2) cations is detected. The mica described is a mariposite with anoma-lously high contents of Ca and Mg.
Mantle-derived dunite and lherzolite nodules from Ubekendt Ejland, west Greenland Tertiary province
Authors: Larsen Jørgen Gutzon 
Published: December 2006

AbstractScattered dunite and lherzolite nodules occur in one of the youngest basanitoid lavas on Ubekendt Ejland. They have protogranular to porphyroclastic textures. The dunites are composed of olivine (Fo93.2−91.9b), enstatite (En93.4−92.8) low in Al2O3 and CaO, and Cr-spinel (61-13% Cr2O3 and 3–55% Al2O3). A solitary lherzolite module has olivine (Fo94.7–94.1), enstatite (En94.7–94.2), Cr-rich spinel, Ti-phlogopite (11% TiO2), and hyalophane. Petrographic evidence suggests that the two latter minerals have not been introduced by magmatic injection from the host in spite of the refractory nature of the coexisting phases, and metasomatic processes prior to the last deformation are therefore indicated. Partial melting of such mantle material would presumably produce small amounts of alkaline liquids even at very high temperatures. Another lherzolite nodule from a lamprophyre dyke has minerals with lower Mg/(Mg + Fe) ratios which, together with its preserved igneous textures, suggest a high-pressure precipitate. The lowest well-esablished equilibrium temperatures of 700–830°C for both dunites and lherzolites indicate a pressure regime of 12-17 kbar, according to the oceanic geotherm, whereas unrealistically high pressure (20–5 kbar) are suggested using the continental shield geotherm.
Roeblingite: new chemical data
Authors: Dunn Pete J. , Norberg Julie A. , Leavens Peter B. 
Published: December 2006

AbstractNew chemical analyses of roeblingite from Franklin, New Jersey, and Långban, Sweden, are presented. The average composition of Franklin roeblingite is SiO2 24.9, CaO 23.8, SrO 2.4. MnO 2.4, PbO 30.2 SO3 10.4, H2O 6.13%, Sum = 100.23%. The data support space group C2/m and suggest the formula is (Ca,Sr)12 (Mn,Ca)2Pb4(SO4)4Si12O28(OH)20, if there is ordering on the site of rank 2.
Mineralization in the Bonser vein, Coniston, English Lake District: mineral assemblages, paragenesis, and formation conditions
Authors: Stanley C. J. , Vaughan D. J. 
Published: December 2006

AbstractThe Bonser vein, one of the most productive sources of copper in the English Lake District, contains a mineral assemblage comprising quartz, chlorite, calcite, dolomite, stilpnomelane, magnetite, pyrrhotine, pyrite, marcasite, native bismuth, bismuthinite, laitakarite, joseite, arsenopyrite, chalcopyrite, sphalerite, galena, and cosalite. The phases pyrrhotine, sphalerite, arsenopyrite, laitakarite, joseite, and cosalite were analysed by electron microprobe. The occurrence of laitakarite is the first reported in the British Isles. Textures of the ore and gangue minerals show that the vein minerals were deposited successively in open voids. The sequence of deposition was of quartz forming throughout, early chlorite and stilpnomelane with some dolomite and calcite, magnetite as the earliest opaque phase, followed by arsenopyrite, pyrrhotine, sphalerite, chalcopyrite, pyrite, and marcasite; the bismuth- and lead-bearing minerals were the last to form.The data on the coexisting phases and their compositions have been used to estimate the temperatures of mineralization and the activities of sulphur and oxygen. Magnetite and arsenopyrite appear to have formed at 350–400% with aS2 reaching 10−12 to 10−14 atm. and aO2 around 10−24 to 10−29 atm. The assemblage of quartz, chlorite, stilpnomelane, calcite, dolomite, pyrrhoine, chalcopyrite, sphalerite, and (late) arsenopyrite was probably deposited at ∼ 240°C, with aS2 decreasing to 10−15 to 10−16 atm and aO2 to 10−38) to 10{su−44 atm. The later minerals probably formed at temperatures as low as 200°C and under similar conditions of sulphur and oxygen activity.
Cooling rate studies of rocks from two basic dykes
Authors: Corrigan G. M. 
Published: December 2006

SynopsisNucleation and crystal growth of plagioclase have been studied in two basaltic melts by one atmosphere, constant-rate and variable-rate cooling experiments using the wire-loop technique (Donaldsonet al., 1975). Constant-rate cooling studies indicate that the length of the incubation period prior to nucleation varies systematically with the degree of supercooling and with the cooling rate. Attempts to determine the rates at which the marginal parts of two dykes (from the Isle of Arran, SW Scotland) cooled, by the attempted reproduction of the natural textural features, in constant-rate cooling experiments suggest that for one of the dykes, plagioclase phenocrysts at the contact could have grown at a cooling rate of approximately 3°C/hour and the groundmass plagioclase laths at faster cooling rates in excess of 10°C/hour. For the other dyke the plagioclase laths in the rocks 0.5 cm from the dyke contact probably grew at rates slower than 2°C/hour. Attempts to validate experimentally the Jaeger (1957) cooling model for the two dykes suggest that the dykes cooled at much slower rates than the theory predicts.
Autometasomatic gneisses of the Currywongaun-Doughruagh syntectonic intrusion, Connemara Ireland
Authors: Angus N. S. , Kanaris-Sotiriou R. 
Published: December 2006

AbstractThe Currywongaun and Doughruagh masses of northern Connemara represent a section through a syntectonic, partially layered intrusion formed of ultrabasic cumulates all having plagioclase of around An94. Differentiation and contamination of the magma from which these cumulates were precipitated ultimately produced an acid residuum which was responsible for the hydrous metasomatism of the earlier formed ultrabasic rocks resulting in the extensive formation of quartz-amphibole-anorthite gneisses in the petrogenetically ‘upper’ parts of the intrusion. Coexisting Ca-rich and Ca-poor amphiboles in the gneisses are interpreted as ‘frozen’ reaction intermediates that were in local equilibrium. The bulk-rock chemical data presented confirm that the compositions of the quartz-rich gneisses can be attributed almost entirely to the addition of Si to the ultrabasic rocks, coupled with the removal of Mg and Ca. The data also suggest that Zr, which reaches around 1000 ppm in some of the gneisses, may have been ‘mobile’ under these conditions of hydrothermal metasomatism.
An occurrence of rare-earth-rich eudialyte from Ascension Island, South Atlantic
Authors: Harris C. , Cressey G. , Bell J. D. , Atkins F. B. , Beswetherick S. 
Published: December 2006

AbstractA mineral closely resembling eudialyte in single crystal X-ray pattern and chemistry has been found in one granite block from the 5 Mile Post area on Ascension Island. To our knowledge, eudialyte has not previously been recognized in this suite of granites although they contain two other rare zirconium silicates, dalyite and vlasovite. Textural evidence suggests that the eudialyte, which is remarkable for its high yttrium and REE content, crystallized from very late-stage magmatic fluids. Rare-earth patterns are only slightly fractionated (CeN/YN = 1.8–2.5) compared with those of allanites and sphenes from Skye granites which presumably have similar parageneses. In contrast, the whole-rock REE pattern shows greater enrichment of light REE (CeN/YN ∼ 10). This difference in REE pattern is considered to be due to the effects of REE and other element complexing related to the peralkalinity of the granite liquid.
The crystal morphology of plagioclase feldspar produced during isothermal supercooling and constant rate cooling experiments
Authors: Corrigan G. M. 
Published: December 2006

AbstractThe crystal morphology of plagioclase feldspar in seven mafic rocks has been studied by isothermal supercooling and constant rate cooling experiments at 1 atmosphere using the ‘wire-loop’ suspension method. There is a systematic variation in crystal morphology with supercooling (−ΔT), but the transitions between the different morphologies are gradual, and consecutive forms sometimes occur together. As −ΔT increases, the sequence of plagioclase morphology is generally laths → skeletal forms → fan spherulites. During isothermal supercooling the position of the plagioclase morphological fields is shown to be dependent on −ΔT, superheating (+ΔT), and also on time to a greater or lesser degree. Variations in melt composition and viscosity affect the position and slope of the boundaries of the fields. In the constant rate cooling experiments, the morphological type is dependent on the cooling rate and can be used to a limited extent as an indicator of the range of supercooling over which the first crystals nucleated and grew.
Appraisal of the Ferguson method and the linear model using Δ(bc), Δ(b*c*), Δ(αγ), Δ(α*γ*) to estimate tetrahedral Al-contents in alkali feldspar
Authors: Blasi Achille 
Published: December 2006

AbstractThe new method proposed by Ferguson (1980, 1981) for estimating the T-site occupancies in K-rich feldspars from lattice constants is discussed and compared with the linear model using the structural indicators Δ(bc), Δ(b*c*), Δ(αγ), Δ(α*γ*). The latter method appears to be considerably more effective in view of its wider application to alkali feldspars of different compositions and structural states. Ferguson's (1980, 1981) method has been conceived for K-rich feldspars alone and may produce results that tend to be more erroneous the further a K-rich feldspar lies from the two-step ordering paths involved in the formulation of the determinative procedure itself.
Evaluation of stream sediment data for favourability of uranium mineralization in Tertiary granitic plutons of the Alaska Range
Authors: Beyth Michael , McInteer Carlotta 
Published: December 2006

AbstractFavourability of uranium mineralization in six tertiary granitic plutons of the Alaska Range in the Talkeetna and Mt McKinley quadrangles was studied. The uranium concentrations of drainage sediment samples, which were collected and analysed by the Los Alamos Scientific Laboratory for the National Uranium Resources Evaluation, were statistically evaluated and compared to those of the surrounding area using factor and cluster analyses. The results of this study suggest that five of the six plutons under consideration are likely to contain uranium mineralization. These plutons are probably a potential source rock for uranium in the region.
Occurrence and significance of awaruite in the Dras ultramafics, Kashmir Himalaya, India
Authors: Radhakrishna T. , Divakara Rao V. , Krishna Rao J. R. S. 
Published: December 2006

AbstractA new occurrence of awaruite, from India, is reported in the ultramafic units of the Dras area which form part of the Indus Suture ophiolites in Kashmir Himalaya. Its formation in these rocks suggests a low-temperature process of serpentinization. Ni and Fe released from olivine and/or pyroxene must have formed awaruite peragenetically next to magnetite and pentlandite.
Eggonite (Kolbeckite, Sterrettite), ScPO4 · 2H2O
Authors: Hey M. H. , Milton Charles , Dwornik Edward J. 
Published: December 2006

SynopsisThe curious history of the mineral eggonite is reviewed, and two new occurrences are described. The original specimens, for which Schrauf gave good morphological and optical data in 1879, with a tentative suggestion that it was a cadmium silicate, were fakes; the tiny crystals of the new mineral were glued on to hemimorphite specimens from Altenberg, Belgium. In 1929, Zimanyi edited and published observations by Krenner, who found the mineral on silver ores from Felsöbánya, Hungary, added to Schrauf's physical data, and identified it as an aluminium phosphate. It was not until 1959 that Mrose and Wappner showed that it is scandium phosphate, ScPO4 · 2H2O, and essentially identical with kolbeckite, described by Edelmann in 1926 as a phosphate and silicate of beryllium, aluminium, and calcium from Saxony, and with sterrettite, described by Larsen and Montgomery in 1940 as an aluminium phosphate from Fairfield, Utah.In 1980 the IMA Commission on New Minerals and Mineral Names, while accepting the identity of the three minerals and rejecting the name sterrettite, were almost equally divided over the names eggonite and kolbeckite, which are thus both acceptable; since eggonite has 47 years priority, we suggest that it should have preference.The available physical and chemical data on eggonite are summarized and added to, and two new occurrences, at Potash Sulfur Springs, Arkansas, and at Sakpur, Gujarat, India, are described.
High-pressure metamorphism between the pelagonian Massif and Vardar Ophiolite Belt, Yugoslavia
Authors: Majer Vladimir , Mason Roger 
Published: December 2006

AbstractA reported occurrence of metamorphic rocks containing sodic pyroxenes, in the transition zone between the Pelagonian Crystalline Massif and the Vardar Ophiolite Belt, in Macedonia, Yugoslavia, has been re-investigated, and pyroxenes, micas, plagioclase, and clinozoisite analysed by microprobe. The presence of the high-pressure metamorphic assemblage quartz + omphacite+albite is confirmed, giving the first definite indication of blueschist-facies metamorphic conditions in Yugoslavia.
The distribution of lithium in some Cornish minerals: ion microprobe measurements
Authors: Wilson G. C. , Long J. V. P. 
Published: December 2006

AbstractIon microprobe analyses of Li are presented for minerals of the Variscan granites and related rocks of west Cornwall. Together with electron microprobe data these provide insight into the behaviour of Li during the protracted late- and post-magmatic history of the granites. The role of the Mg-Fe tourmaline series is emphasized in this exploratory study.
New data on georgiadesite
Authors: Roland C. Rouse  , Pete J. Dunn  
Published: December 2006

AbstractThe chemistry and crystallography of type georgiadesite from Laurion, Greece, have been reexamined using electron microprobe analysis along with powder and single-crystal X-ray diffraction. Georgiadesite is monoclinic, P21/c, with a = 13.803(10), b = 7.910(2), c = 10.812(4) Å, and β = 102.68(3)°. No twinning was observed. The probable chemical formula is either Pb16(AsO4)4Cl14O2(OH)2 or Pb16(AsO4)4Cl14(OH)6. The calculated densities for these formulae are 6.39 and 6.44 g/cm3, respectively, compared to a measured value of 6.3 + 0.3 g/cm3
Karroo basalts of southern Malawi and their regional petrogenetic significance
Authors: Macdonald R. , Crossley R. , Waterhouse K. S. 
Published: December 2006

AbstractKarroo basaltic lavas of southern Malawi are divided into two groups on the basis of stratigraphy, petrography, and the data from 20 newly analysed rocks. A lower group of porphyritic lavas is notably rich in plagioclase phenocrysts and has contents of K, Ti, P, Ba, and Zr unusually high for tholeiitic basalts. They are overlain by an upper group of aphyric or sparsely microphyric lavas whose chemistry is more normal for tholeiites and is comparable with that of the Karroo dolerite dykes in Malawi. Though they outcrop in the northern part of the Karroo province, the lavas and dykes have chemical characteristics more similar to southern province rocks, adding some complexity to the concept of geochemical provinces established by earlier workers. Inter-suite variations in incompatible trace element contents and ratios indicate that the basalts of each group were derived from heterogeneous mantle sources.
The geochemistry of hydrothermal and pelagic sediments from the Galapagos Hydrothermal Mounds Field, D.S.D.P. Leg 70
Authors: Moorby S. A. , Cronan D.S. 
Published: December 2006

AbstractOver 200 sediment samples taken from ten holes drilled in the Galapagos Hydrothermal Mounds Field during D.S.D.P. Leg 70 have been analysed for twenty-one elements. The three main sediment lithologies recognized are siliceous carbonate ooze, Mn-oxide crust, and an Fe-rich silicate (nontronite), the latter two being of hydrothermal origin. The major element composition of the hydrothermal deposits is similar in each mound hole, suggesting that formation conditions and hydrothermal solution composition have been constant both geographically and with time. The large variations which occur in the concentration of some trace elements in the Mn-oxide crusts and in transition metal ratios in the nontronite compared with the pelagic ooze suggests a hydrothermal supply to the mounds of Li, Mo, Pb, and Ba in addition to Mn, Fe, and silica.The data are compatible with suggestions that the nontronite formed at depth in the pelagic sediment blanket by replacement of biogenic ooze, whilst the Mn crusts formed at or near the sediment-water interface. Pelagic sediments in the mounds which have not been replaced are similar in composition to pelagic sediments from non-mounds holes.
A reappraisal of chloritoid-bearing phyllites in the Forland Complex rocks of Prins Karls Forland, Spitsbergen
Authors: Manby G. M. 
Published: December 2006

AbstractIn the Forland Complex chloritoid is restricted to the grey and green phyllites which characterize the Scotia and Peachflya groups. The textures and compositions of the rocks and constituent minerals are described and discussed in an attempt to assess how metamorphism, deformation, and chemistry have influenced the stability of chloritoid.
The Structural behaviour of tetrahedral framework compounds—a review. Part I. Structural behaviour
Authors: Taylor D. 
Published: December 2006

AbstractTetrahedral framework compounds, as defined in this paper, generally exist as tilted and distorted versions of ideal fully expanded structures at room temperature and atmospheric pressure. How pressure, temperature, and composition (P, T, and X) affect the tilting and distortion is critically reviewed. Although P, T, and X are generally regarded as analogous variables in their effect on framework structures there is reason to believe that they have different structural effects. In particular, an important, and frequently neglected, thermal effect is the apparent shortening of the framework bonds by the anisotropic thermal motion of the framework oxygens. The effects of P, T, and X on displacive transformations in framework compounds are reviewed with particular reference to the disordered alkali feldspars and the leucites. It seems probable from the available evidence that displacive transformations do not take place at a critical size of the framework. Displacive transformations can take place with or without a volume discontinuity and hysteresis. Furthermore, the effects of P, T, and X on a solid-solution series with a displacive transformation can be different, one variable causing a volume discontinuity and another a smooth transition.