bluuebunny/crossref_metadata_2025_split huggingface dataset:
Techniques of field gamma-ray spectrometry
Authors: Cassidy J. 
Published: December 2006

AbstractField gamma-ray spectrometry is a rapid and effective quantitative method of mapping variations of radioelements within igneous intrusions. A field procedure for radioelement mapping demonstrates the value of the method to studies of late-stage magmatic processes during the emplacement of granite intrusions and the determination of their present-day heat productivities. Methods and problems of instrument calibration using both natural and artificial sources are discussed. Calibration based on neutron activation analysis of samples from natural outcrops achieves results comparable with those obtained using artificial sources and has the advantage that it relates directly to field conditions; furthermore it enables secular disequilibrium in the uranium and thorium decay series to be recognized.
U, Th, and K distribution in a differentiated charnockite-granite intrusion and associated rocks from SW Sweden
Authors: Constable J. L. , Hubbard F. H. 
Published: December 2006

AbstractThe concentrations of U, Th, and K in a charnockite-alkali granite intrusive complex from SW Sweden and associated, partly charnockitized country rocks are presented. The charnockitic components have constant low U and Th levels throughout the compositional range with a mean Th/U ratio of 1.2 to 1.5. The transition from charnockite to granite is marked by a sharp increase in Th and U concentrations with mean Th/U ratios increasing to 3.4 4.4. However, the K concentration increases relatively smoothly with increasing acidity through the compositional range studied. Late shearing of the alkali granite led to significant Th depletion with little change in the U and K concentrations. Charnockitization of the country rock granite gneisses is marked by depletion in Th and K while the U content is almost unchanged.It is suggested that the behaviour of U and Th reflects the tendency for Th to associate with magma-dissolved water whilst U shows a greater affinity for coexisting free volatiles. In the absence of a significant free volatile phase during crystallization of this charnockite-granite suite, U was incorporated into primary mineral lattice sites whereas Th entered sites from which it could be liberated more easily.
On the sources of uranium in some Scottish Caledonian granites
Authors: Halliday A. N. 
Published: December 2006

AbstractThe lead isotope systematics, zircon uranium concentrations and whole-rock rubidium concentrations of 11 Scottish Caledonian granites are examined for clues to the origin of their uranium. A positive correlation between U in zircon and initial lead isotope ratios suggests that U and Pb were derived from the same source which, as some of these granites contain their U in inherited zircons, is likely to have been within the crust. It is argued, therefore, that most of the uranium in these granites had a crustal derivation but lead isotope ratios indicate that any Lewisian contribution was minor in comparison with those from postulated Grenville, Morarian or Caledonian metamorphic reservoirs. However, additional data are required before this conclusion can be extended to include uraniferous Caledonian granites such as Cairngorm.
A classification of British Caledonian granites based on uranium and thorium contents
Authors: Hennessy John 
Published: December 2006

AbstractA method of epithermal neutron activation analysis for uranium and thorium is discussed in relation to other rapid analytical methods for these elements. Caledonian granites are divided into four main groups on the basis of U and Th contents: (a) a group of evolved late granites with high U and Th contents and high Th/U ratios, (b) a group of uranium-enriched mineralized granites, (c) granites containing approximately average levels of U and Th, and (d) a group of granites with low thorium content.
Identification of uraniferous granitoids in the USA using stream sediment geochemical data
Authors: Howarth R. J. , Koch G. S. , Plant J. A. , Lowry R. K. 
Published: December 2006

AbstractTrace element variations in stream sediments from an area of 76 000 km2 in central Colorado are used to identify uraniferous granitoids on the basis of whole rock geochemical criteria developed to distinguish barren from metalliferous granitoids in Britain. These criteria (which include enhanced Ba, Be, Cs, Cs/Ba, K, La/Eu, Li, Lu/Eu, Nb, Rb, Rb/K, low Sr and Mg, and RE patterns with marked negative Eu anomalies) are used to formulate an index based on the Pikes Peak batholith of the Front Range as a type uranium source rock.Uraniferous granitoids in Colorado, which are associated with sedimentary basins containing major uranium mineralization, are identified using this index which may be applicable to the interpretation of stream sediments from elsewhere. The use of stream sediment geochemistry as an exploration method for similar uranium source rocks, which may indicate potential uranium provinces, is thus possible.
Uraninite-albite veins from the Mistamisk Valley of the Labrador Trough, Quebec
Authors: Kish L. , Cuney M. 
Published: December 2006

AbstractThe uraninite-albite veins of the Mistamisk area occur in the argillite member of the Dunphy Formation, which is near the base of the slightly meta-morphosed Lower Proterozoic sequence of the central Labrador Trough. The vein minerals are albite, uraninite, dolomite, and chlorite, and minor quantities of quartz, tellurides, sulphides, gold, and organic material. Pitchblende and calcite are related to late remobilization.The veins were deposited in fractures by hydrothermal solutions, and metasomatism caused albitization of wall rocks. Fluid inclusions have an unusual composition, described here for the first time in connection with soda-metasomatism; the aqueous solution of the inclusions is oversaturated in NaCl and contains Ca2+ and Mg2+, and the gas phase mostly consists of N2, CO and CO2. The presence of hematite and absence of hydrocarbons indicates that the vein-forming solution was oxidizing.The temperature and pressure of vein formation, estimated from fluid inclusion data, was 300°–350° and 2.5 kbar respectively consistent with the composition of the phengite which is a common metamorphic mineral of the host rock. Vein emplacement occurred in the waning stages of the Hudsonian Orogeny, the hydrothermal solution possibly originating by metamorphism of sodic schists of the Mistamisk area, which are possibly of evaporitic origin.
The nature of the upper mantle
Authors: Dawson J. B. 
Published: December 2006

AbstractThe nature of the upper mantle below the ancient cratonic areas can be deduced by study of the xenolith suites in kimberlites. Studies on the proportions of xenoliths, together with their mineralogy and chemistry, suggest an upper mantle containing an upper harzburgite zone and a lower lherzolite zone, with both of these zones containing chemical and mineralogical variants, together with minor rock types such as glimmerites, MARID-suite rocks, pyroxenites, and eclogites. Isotopic studies of the phases in xenoliths have yielded restricted ranges of values for the isotopic composition of hydrogen, carbon, oxygen, and sulphur which are tentatively identified as the true isotopic values for these elements in the upper mantle. In addition, recent discoveries suggest that diamond may be a primary uppermantle phase.The textures and fabrics of the xenoliths indicate that plastic deformation has taken place in connection with the intrusive kimberlite event, and also in earlier events unconnected with the kimberlite event. In addition, brittle fracture has been observed, this fracturing often being accompanied by the filling of the ensuing veins and joints by fluids that have crystallized potassium-, titanium-, and water-rich phases; limited metasomatism of peridotite wall rocks accompanies this vein filling and more widespread pervasive metasomatism may also be present.Although most upper-mantle rocks are now metamorphic, in some rare instances there are relics of earlier rock types that have not been completely obliterated by subsequent metamorphic events; most of these could be attributed to an igneous origin and in most cases during subsequent metamorphism the original rock types have been subjected to increasing pressures and/or lower temperatures.Although the source of most materials now present at the earth's surface can be directly attributed to some identifiable source within upper-mantle rocks, no source has yet been identified for CO2, N, P, and the rare gases.
Solid solution and cation ordering limits in high-temperature sodic pyroxenes from the Nybö eclogite pod, Norway
Authors: Carpenter M. A. , Smith D. C. 
Published: December 2006

AbstractA range of sodic pyroxenes (Jd78Ac2Aug20Jd24Ac9Aug67) from the Nybö eclogite pod, Norway, have been examined by electron-microprobe analysis and by transmission electron microscopy.. Five different microprobes give generally compatible results and new analyses completely fill the natural composition gap in jadeite-rich omphacites with ∼ 3–12% acmite, confirming complete miscibility at high temperatures (⩾ 700 °C). Crystals with omphacite compositions around jadeite: augite = 1:1 contain antiphase domains resulting from the C2/c → P2/n cation ordering transformation. Exsolution microstructures were not observed, from which it is concluded that there are no two-phase regions separating the P2/n and C2/c stability fields at high temperatures (∼ 620–750 °C) and that cooling was too rapid for exsolution to occur in the jadeite/omphacite and omphacite/augite low-temperature solvi. Crystals whose compositions depart significantly from Jd:Aug= 1:1 have weak, diffuse h + k = odd reflections in selected area electron diffraction patterns which are interpreted as being due to short-range ordering outside the true P2/n stability field. The short-range ordering and lack of exsolution are consistent with a previous suggestion that the order/disorder transformation in omphacite is second (or higher) order in character. The average antiphase domain sizes (up to ∼ 3500 Å) are larger than any previously recorded in omphacites and are consistent with available petrological evidence for a long period of annealing at high temperatures before tectonic uplift and cooling.
Taneyamalite, (Na,Ca)(Mn2+,Mg,Fe3+,Al)12Si12 (O,OH)44, a new mineral from the Iwaizawa mine, Saitama Prefecture, Japan
Authors: Matsubara Satoshi 
Published: December 2006

AbstractTaneyamalite, (Na,Ca)(Mn2+,Mg,Fe3+,Al)12 Si12(O,OH)44, is a Mn2+-dominant analogue of howieite, and has been found in the metamorphosed bedded manganese ore deposit of the lwaizawa mine, Saitama Prefecture, Japan. It is triclinic, P1 or P, a 10.198(1), b 9.820(1), c 9.485(1) Å, α 90° 30(1)′, β 70° 32(1)′, γ 108° 34(1)′, Z = 1. The strongest X-ray powder diffractions are: 9.29(80)010, 7.99(35)10, 4.62(50)020, 3.65(40)120, 3.273(100)30, 3.081(50)11, 2.790(35)31, 2.630(28)023, 2.216(35)014, 43. Taneyamalite occurs in association with minor bannisterite as small seams in a caryopilite mass or as a fissure mineral cutting a hematite-quartz mass. It is greenish grey-yellow, lustre vitreous. Streak light yellow. Cleavage {010}, perfect. H. (Mohs) about 5. Calculated sp. gr. 3.30 (on unit cell data and normalized empirical formula), 3.25 (after the Gladstone-Dale Law using the revised data of Mandarino, 1976). It is optically biaxial negative, 2Vα about 70°. The refractive indices: α = 1.646(2), β = 1.664(2), γ = 1.676(2). Extinction is nearly parallel, sign of elongation positive. Pleochroism distinct: α = β nearly colourless, γ pale yellow. Absorption: α ≈ β < γ.
Choloalite, CuPb(TeO3)2·H2O, a new mineral
Authors: Williams S. A. 
Published: December 2006

AbstractProbably first found in Arabia, then Moctezuma, Sonora (the type locality), finally at Tombstone, Arizona. Crystals are cubic, invariably octahedral in habit, up to 2 mm in size. Colour forest green (RHS 136A), H = 3, D = 6.4.Wet chemical analysis gave CuO 11.0%, PbO 33.0, TeO2 50.7, H2O 3.4; soluble in cold dilute acids. The strongest lines are 7.223(5), 4.170(2), 3.614(3), 3.472(4), 3.343(6), 3.036(10), 7.952(3), 2.454(5) Å. The cell indexes as cubic, a = 12.519 Å; for Z = 12, ρcalc = 6.41 g/cm3. May be anisotropic in thin section with birefringence up to 0.011; n = 2.04.
Aldermanite, a new magnesium aluminium phosphate
Authors: Harrowfield I. R. , Segnit E. R. , Watts J. A. 
Published: December 2006

AbstractA new magnesium aluminium phosphate mineral with the ideal formula Mg5Al12(PO4)4(OH)22·nH2O (n ⋍ 32) has been named aldermanite. It occurs as minute talc-like flakes, partly as an alteration product of fluellite, thinly coating cracks and cavities in a brecciated metamorphosed rock phosphate at Moculta, South Australia. Strongest X-ray diffraction lines are 13.40 Å (100) 002, 7.98 Å (80) 011, 5.55 Å (60) 210; unit cell parameters a= 15.00±0.007, b=8.330±0.006, c= 26.60±0.01 Å, Z = 2.
Origin of hydrous cordierite and isotopically light oxygen in granulite-facies rocks, Strangways Range, Central Australia
Authors: Allen Alistair R. 
Published: December 2006

AbstractThe origin of hydrous cordierite from a granulite-facies terrain in the Strangways Range, Central Australia, reported by Wilson (1978) is reviewed. In the light of geochemical and microstructural evidence for a metasomatic episode which affected the terrain subsequent to the growth of the cordierites, it is contended that the hydrous character of the cordierites results from hydration of the cordierite at this time. Extraneous argon also recorded in these cordierites may either have been incorporated into the cordierites at this time or at a later stage in the history of the terrain due to partial loss of radiogenic argon from micas which grew during the metasomatic episode. Furthermore, in view of the history of these cordierites, oxygen isotope values for the cordierites reported by Wilson are likely to be anomalous, and the isotopically light oxygen in the host granulites recorded by Wilson and Baksi (1978) probably reflects exchange with the metasomatic fluids which permeated the terrain.
Equilibration conditions of upper-mantle eclogites: implications for kyanite-bearing and diamondiferous varieties
Authors: Carswell D. A. , Dawson J. B. , Gibb F. G. F. 
Published: December 2006

AbstractNew mineral data for kyanite-bearing eclogites supplement existing data for eclogite nodule suites from the Roberts Victor and Bellsbank kimberlite intrusions, South Africa. Calculation of equilibration temperatures using the refined KD calibration of Ellis and Green (1979) indicates that the majority of these eclogites equilibrated over a considerably narrower range (940–1185 °C) than implied by earlier estimates which did not take account of the influence of the Ca-component of garnet on KD. Most of the Roberts Victor diamondiferous eclogites appear to have equilibrated in the lower part of this range, whilst the equilibration temperatures for the Roberts Victor diamond-free eclogites extend to higher values than those from Bellsbank. The petrogenetic implications of the (calculated) temperature and pressure equilibration conditions for these eclogite suites are discussed with particular reference to possible uppermantle geotherms and available data on the graphitediamond transition boundary.
Högbomite of unusual composition from Reedy Creek, South Australia
Authors: Mancktelow N. S. 
Published: December 2006

AbstractHögbomite from Reedy Creek, South Australia, is of a composition outside the previously reported range. It contains less Ti and Mg and more Al and total Fe, with a total Fe/(total Fe + Mg) value between 0.69 and 0.72. The högbomite occurs in unusual cordieritesillimanite aggregates containing minor magnetite, ilmenite, hematite, corundum, and hercynite.
Wollastonite from hydrothermally altered basaltic rocks in Iceland
Authors: Kristmannsdóttir H. 
Published: December 2006

AbstractWollastonite is reported, for the first time in Iceland, in hydrothermally altered basaltic rocks in the Krafla high-temperature geothermal area, northern Iceland. Two possible modes of origin are suggested: (1) A contact metamorphic origin at the expense of hydrothermal quartz and calcite near the margins of dykes. (2) A hydrothermal origin at depths below 1000 m where fluid temperatures exceed 300°C.
Chemical studies on the stabilities of boleite and pseudoboleite
Authors: Abdul-Samad Fawzy A. , Alun Humphries D. , Thomas John H. , Williams Peter A. 
Published: December 2006

SynopsisFREE energies of formation of boleite, Pb26Cu24 Ag9Cl62(OH)47·H2O, and pseudoboleite, Pb5Cu4 Cl10(OH)8·2H2O, have been determined from solution studies at 298.2 K. ΔG°f values for the minerals are −19097.9±4.1 and −3705.4±5.5 kJ mol−1 respectively. These values, together with results of earlier studies (Humphreys et al., 1980) have been used to construct the stability field diagram shown in fig. 1. The boundaries for boleite and pseudoboleite are shown separately. If fields for the two minerals are plotted together, boleite has no thermodynamic stability at the silver ion activity chosen. At higher activities of Ag+(aq) the boleite field is negligible in extent.The results can, however, be rationalized in terms of kinetics of mineral formation, rather than thermodynamic considerations alone. Since pseudoboleite is never found without boleite upon which it is observed to grow epitaxially (Winchell, 1963), it is clear that boleite must form metastably prior to any pseudoboleite deposition. Accordingly, boleite has a large range of solution compositions, from which it may precipitate. The hatched area of fig. 1 shows this at the Cu2+(aq) and Ag+(aq) activities chosen. The field is terminated at high aCl− by the AgCl line, above which silver is precipitated as AgCl(s), chlorargyrite.It is also evident from the chemical studies that the deposition of several assemblages in the leadcopper-chloride group of minerals is simply related to variations of chloride activity. With decreasing aCl− the associations cumengeite + boleite + pseudoboleite, diaboleite + boleite + pseudoboleite, and diaboleite + chloroxiphite are expected in turn. This relationship is apparently borne out by field observations of occurrences of the minerals.
Amphiboles in the Lilloise intrusion, East Greenland
Authors: Brown P. E. , Tocner F. E. , Chambers A. D. 
Published: December 2006

AbstractAmphibole in the lower parts of the Lilloise layered intrusion occurs interstitially and as a replacement of pyroxene; in the upper rocks it is a major cumulus phase. There is an overall trend of increasing Fe/(Fe + Mg) with height. Coupled substitutions which effect the variation in composition of the amphiboles are chiefly Na,K(A)+Al(T) for □A+SiT) and Ti+Al(T) for Fe3+(C)+ Si(T). There is considerable variation in composition both on the specimen scale and within individual grains. This variation, plus scatter found in plots of the coupled substitutions, is partly attributed to many of the amphiboles having replaced pyroxene and also to the effects of magmatic-hydrothermal fluids.
Studies of the orthoamphiboles III. Hydroxyl spectra of gedrites
Authors: Law Anthony D. 
Published: December 2006

AbstractInfra-red spectra of gedrites have been measured in the hydroxyl region (3800–3500 cm−1). The spectra can be related to those of clinoamphiboles and of anthophyllites, and show the normal amphibole pattern of peaks whose intensities reflect the proportions of different cations in the adjacent octahedral sites. The absorption is weak especially in spectra of gedrites high in Al. Hyperfine splitting of peaks has been observed in anthophyllite spectra (Law, 1981) but the extent of hyperfine splitting in gedrite spectra is limited. The underlying baseline absorption, upon which the hydroxyl peaks are superimposed, becomes steeper and more awkward to estimate in gedrites. Some higher frequency peaks, probably arising from unit cells withAsites occupied by Na, are observed.
Interlayered biotite-kaolin and other altered biotites, and their relevance to the biotite isograd in eastern Otago, New Zealand
Authors: Craw D. , Coombs D. S. , Kawachi Y. 
Published: December 2006

AbstractGreen biotite-like material occurring in Haast Schist at Brighton, eastern Otago, consists of biotite and a kaolin-group mineral interlayered on a 1 μm scale. Electron probe analyses of composite grains show K2O contents of 4.4 to 8.5 wt.%, in part reflecting the kaolin content, and in part, leaching of K+ ions. Phengitic muscovite shows similar but less extreme effects. Kaolin, siderite, calcite, and titanium oxides have formed in the rock during hydrothermal alteration of epidote, sphene, and biotite by carbonated waters. Potassium leaching due to surficial weathering processes appears to be widespread in biotites from the schists of eastern Otago, and biotites (hydrobiotites?) with K2O as low as 4 wt. % are reported. Similar material with 0.8 to 2.4% K2O and with Na2O about 1% is thought to be more highly degraded biotite. Microprobe analyses of kaolin and chlorites from associated rocks are given in addition to those of ‘biotite’ and phengitic muscovite. Analyses of sheet biotite and sheet muscovite from the Mataketake Range pegmatites in the highest grade parts of the Haast Schist terrane are presented for comparison. The study shows that biotite is more widespread in eastern Otago than was previously thought, and that almandine-rich garnet is not confirmed down-grade of the first appearance of biotite in eastern Otago.
The Laytonville Quarry (Mendocino County California) exotic block: iron-rich blueschist-facies subduction-zone metamorphism
Authors: Wood Robert Muir 
Published: December 2006

AbstractThe Laytonville Quarry exotic block contains a series of deep-ocean sediments of varying Fe: Mn, Fe:Al and Fe2+ : Fe3+ contents, but all enriched in Fe-Mn carbonates. These sediments have a complex metamorphic history that has involved the early development of aegirine and garnet, followed by various phases of ‘secondary’ mineral growth, all of which required the addition of water to the metamorphic assemblages under high-P, low-T conditions. During the course of an early hydration episode deerite formed within most of the ironstones, and zussmanite in certain Fe-rich, Mn-poor pelites. At a later, and apparently lower pressure period in the metamorphic history, howieite, riebeckite, stilpnomelane, and a more manganous variety of zussmanite (ZU2) have overtaken much of the earlier mineralogy. Subsequent to this, and contemporaneous with the development of the tremolite-talc exotic block rind assemblage, there is a minor development of minnesotaite and ekmanite. During the course of the metamorphism the ironstones have become enriched in K and Na, necessary to form the blueschist meta-ironstone mineralogy. Such rocks therefore have the potential to reveal details of fluid expulsion within the subduction zone.
Trace element distributions between the perthite phases of alkali feldspars from pegmatites
Authors: Mason R. A. 
Published: December 2006

AbstractThe distribution of various trace elements between the K-feldspar and albite phases of perthites from several pegmatites was determined by ion microprobe. Ranges in distribution coefficients (wt. % in K-feldspar/wt. % in albite) are: Li, 1.2–780; Mg, 0.2–1.1; P, 0.1–17; Ca, 0.02–1.6; Cs, 32–820; Ba, 24–284; Pb, 1.6–30; Fe, 0.3–0.7; Rb, 59–5505; Sr, 1.3–5.1. The trace elements are zoned within the K-feldspar lamellae and the profiles are interpreted as the result of cross coefficients in the diffusion matrix.