bluuebunny/crossref_metadata_2025 huggingface dataset:
The mineralogy and geochemistry of uranium, thorium, and rare-earth elements in two radioactive granites of the Vosges, France
Authors: Pagel Maurice
Published: December 2006

Two contrasting types of Hercynian U-rich granites can be distinguished by their accessory minerals: (1) subalkaline potassic granites (amphibole-biotite±pyroxene) characterized by apatite-zircon-thorite-sphene-allanite and rare ThO2-rich uraninite, in order of appearance in the magma, and (2) leucocratic granites (biotite and muscovite) which contain monazite-zircon-apatite-xenotime-ThO2-poor uraninite and Ti oxides. Intermediate accessory mineral associations may also exist.

The mineralogy, crystallization history, and geochemistry of two high K-U-Th granites from the Vosges, France, is described. Their assemblage of U- and Th-bearing accessory minerals is listed, in order of appearance in the magma, in Group 1 (above). Trace elements (U, Th, Zr, Hf) and preliminary data on REE are discussed. In a layered sequence of the Crêtes granite, thorite, with up to 15% UO2, is shown to be important during differentiation. There is a decrease of the Th/U ratio corresponding to a slight decrease of the Th content whereas there is an increase of the U content at the end of differentiation. The Crêtes and Ballons granites have REE patterns characterized by LREE enrichment with a La/Yb ratio of about 28 (Crêtes granite) and a slight negative Eu anomaly. These relationships are typical of subalkaline potassic granites of the Hercynian. The trace element associations are similar to those of the shoshonite association with high U, Th, LREE and Ba, Rb, and Sr contents. A hypothetical model for uranium mineralization associated with such granites is discussed in the light of these data.
Uranium occurrences in the Cree Lake Zone, Saskatchewan, Canada
Authors: Parslow G. R. , Thomas D. J.
Published: December 2006

Over 100 samples of ‘pegmatite’ and associated host rocks from the Cree Lake Zone of northern Saskatchewan have been studied. The degree of U and Th enrichment of the pegmatites appears to depend on the parent material of the anatectic melts produced during the Hudsonian thermotectonic event. Evidence for Archaean granulite-facies depletion of U and Th is inconclusive; however, important enrichment of U and Th in the basal Aphebian is associated with metamorphosed black shales and possibly evaporates.
Determination of uranium: carbon ratios in fluid inclusion decrepitates by inductively coupled plasma emission spectroscopy
Authors: Rankin A. H. , Alderton D. H. M. , Thompson M. , Goulter J. E.
Published: December 2006

Uranium has been detected in fluid inclusion decrepitates from quartz of several granites of the British Isles and from vein quartz associated with the Hcrcynian granites of SW England using ICP. Material, ejected from the inclusions during decrepitation on heating the sample, is transferred into the plasma for qualitative analysis via a stream of argon. Several other elements have been detected in the decrepitate, of which carbon is of particular interest. It shows a strong positive correlation with U and indicates the importance of C (presumably as carbonate complexes) in the transport of U in hydrothermal systems. Approximate order of magnitude estimates of the average U contents of fluid inclusions from the SW England samples, based on the assumption that U in the decrepitates is principally derived from the fluid inclusions, range from less than one to over a thousand ppm. Fluid inclusions may therefore be important in contributing to the levels of U reported in quartz (0.1 to 10 ppm).
The occurrence of uranium in association with cassiterite, wolframite, and sulphide mineralization in South-West England
Authors: Swart P. K. , Moore F.
Published: December 2006

The U content of cassiterite (SnO2), wolframite (Fe,Mn)WO4, and various sulphides from two localities in the Cornubian batholiths of south-west England has been investigated. Cassiterites showed concentrations of U between 0 and 6 ppm with the higher concentrations corresponding to the darker colour bands. Sulphides contained no detectable U using the fissiontrack method, but high concentrations relate to micro-veining. This veining was also evident in associated wolframite and appeared to have a composition similar to an iron-arsenate mineral associated with the alteration of arsenopyrite. Wolframite exhibited a wide range of U concentrations with sharp zonation and several generations of ore deposition within one crystal. The U was not, however, associated with either the iron- or manganese-rich phases.
Uranium-rich granites in the Olden Window, Sweden
Authors: Troëng Björn
Published: December 2006

U-enriched granites occur in a Precambrian window in the Caledonides of central Sweden and intrude an extensive supracrustal formation dominated by acid terrestrial volcanics. During the Caledonian orogeny, thrusting, foliation, mylonites, and mesoscopic folds developed in the Precambrian rocks under low-grade metamorphic conditions. Ground and airborne γ-spectrometry indicate U-enrichment mainly in the northern part of the window where two uraniferous granites have been intruded. Several small U vein-type mineralizations are associated with one of the granites. The largest occurrence of the mineralization might be economic, and a Rb-Sr age determination has established a minimum age of 1500 Ma on the associated granite which is highly evolved.
Uranium and thorium geochemistry in the elberton batholith of the Southern Appalachians, USA
Authors: Wenner David B. , Spaulding James D.
Published: December 2006

U and Th data have been obtained by γ-ray spectrometry on samples from thirty quarry sites in the Elberton batholith, a large (500 km2) late orogenic (320 Ma) mesozonal biotite granite in the Southern Piedmont, USA. The granite is enriched in the Th (=42ppm), but U contents (=3ppm) are close to the average abundance for granites (18 ppm Th; 4 ppm U). Th/U ratios vary widely throughout the batholith, ranging from 3 to 58, with an unusually high mean of 18±10 (1). At some localities, lower Th/U ratios, high U contents of zircons (1500 ppm), and similarities to two-mica granites which have low Th/U ratios of ∼ 1 indicate that the granite once had a much higher U content. Pegmatites are enriched in U (up to a factor of 8), but Th contents are low (by a factor of 3) compared with the granite suggesting loss of U from the granite by an early magmatic vapour-phase. Significant U loss may also have occurred as a result of groundwater leaching, possibly associated with uplift and weathering of the intrusion 200 Ma ago. The highest Th/U values occur in the upper portions of the batholith, consistent with the hypothesis of U loss by these processes. The U content is highly variable throughout the batholith but Th is more uniform, both regionally and at outcrop. The distribution of Th does not correlate with patterns shown using previously published, 18O/16O, 87Sr/86Sr, or trace element (Ba, Rb. Sr, Mn) data, which are thought to reflect inhomogeneity in the protolith of the granite although the possibility that at least some of the isotopic ratios were disturbed by late alteration processes cannot be eliminated.
Geological setting and geochemistry of uranium-rich granites in the Proterozoic of Sweden
Authors: Wilson M. R. , Åkerblom G. V.
Published: December 2006

Uraniferous granites occur in several different geological settings in the Swedish Precambrian and represent a variety of granite types and ages. Granites with > 10 ppm U are highly differentiated leucocratic alkali granites with initial87Sr/86Sr ratios over 0.708. They commonly show enrichment in F, Sn, W, and/or Mo, while mineralization of these dements may, in some cases, be found in the nearby country rock. Radiogenic heat from the granites may have assisted hydrothermal circulation. In only one case, Hotagen, is important U mineralization thought to be directly related to a U-rich granite, while the majority of epigenetic U mineralizations with economic potential are related to hydrothermal processes in areas where the bedrock is regionally enhanced in U.
Some observations on todorokites from marine and terrestrial environments
Authors: Ostwald Joseph
Published: December 2006

Manganese nodules from the central Pacific contain poorly crystalline todorokite and also small amounts of a post-depositional recrystallization todorokite. The Cu and Ni of the nodules is preferentially concentrated in the latter. Crystalline todorokite on Groote Eylandt does not contain Cu or Ni, providing further evidence that these elements are not necessary to the development of well-crystalline todorokite.
New data for pitticite and a second occurrence of yukonite at Sterling Hill, New Jersey
Authors: Dunn Pete J.
Published: December 2006

Pitticite is re-examined analytically and found to be a gel-like mineral of widely varying composition. Previously reported minor amounts of accessory elements are indeed present in pitticite. The name pitticite has validity only as a generic name for gel-like ferric iron arsenate minerals of varying composition.

Yukonite is reported from the Sterling Hill mine, Ogdensburg, New Jersey, the second occurrence. New data for yukonite suggest the name should be retained.
Ferromagnesian silicates in a differentiated alkaline complex: Kûngnât Fjeld, South Greenland
Authors: Stephenson D. , Upton B. G. J.
Published: December 2006

Kûngnât Fjeld is an intrusive complex resulting from three intrusive events involving trachyte, mafic trachyte and hawaiite magmas tapped successively from a single magmatic source. In situ differentiation produced gabbroic, syeno-gabbroic, syenitic, and quartz syenitic cumulates showing strong cryptic variation. Layered sequences of syenitic rocks total c. 3500 m. The compositional range is extended by late-stage minor intrusions of microsyenite and peralkaline granite. The principal cumulus minerals are feldspar (Ab40An60 to Or45Ab51An4); olivine (Fo56 to Fo1) and clinopyroxene (Di70Hd27Ac3 to Di6Hd90Ac4 followed by an abrupt change of trend towards Di3Hd78Ac19 in the layered series and nearly pure aegirine in some peralkaline residues). Intercumulus phases are amphibole (hastingsite to ferro-edenite to ferro-actinolite in the layered series with riebeckite to arfvedsonite in some associated granites) and biotite (annite31 to annite98.5).
Nature and origin of meladiorite layers in northern Guernsey, Channel Islands
Authors: Bishop A. C. , French W. J.
Published: December 2006

The Cadomian igneous complex of N. Guernsey includes gabbro, diorite, granodiorite, and adamellite. The gabbro is layered, shows variations in colour index and texture, contains abundant amphibole, and is cut by the diorites. The diorites show little variation in mineral compositions despite considerable variation in modal proportions. They contain numerous thin and roughly parallel veins of leucodiorite and granodiorite, and layers of meladiorite occur in several places within the veined diorites. These meladiorites, previously interpreted as separate intrusions, form individual layers from a few centimetres to several metres thick which can be traced for some tens of metres along strike. The upper surfaces of the meladiorites are planar but the lower tend to be indented and irregular. The layers thin out laterally and usually pass into the host diorite by way of a zone containing dark spots and both the spots and the meladiorite layers are composed of actinolitic hornblende and Mg-biotite.

Chemical and petrographic data are presented for most of the rocks and minerals especially for the meladiorites and their host, the veined diorites. The rock chemistry and particularly the compositions of the amphiboles and micas of the meladiorites and the mafic spots, taken together with the presence of unmixing lamellae in the amphibole and the details of the field relationships, indicate that the rocks tended to equilibrium under subsolidus conditions and are most probably of metasomatic origin.

Acid pipes and pegmatites occur within and are restricted to the meladiorites. The forms of the pipes were previously taken to indicate that they were magmatic at the same time as the meladiorites. The metasomatic origin for the meladiorites proposed here calls into question this magmatic interpretation and it is suggested that the pipe formation is connected with the metasomatic process. It is envisaged that the alteration of the veined diorites took place under conditions in which high gas pressures allowed acidic melt to be produced at temperatures only a little above the solidus of the diorites. The thermal impulse for this recrystallization may have resulted from the polyphase intrusive history of the complex as a whole.
A calcium-poor rhodonite from Xanthi (N. Greece)
Authors: Sapountzis Elias S. , Christofides George
Published: December 2006

A Ca-poor rhodonite (CaO 1.31 wt.%), found in a quartz vein cutting manganese ore bodies, north of the Xanthi plutonic complex (northeastern Greece) was studied. Microprobe analyses with optical and physical properties are given. The cell dimensions, obtained by least squares calculation from direct θ value measurements on a Philips PW1100 single-crystal diffractometer are a = 7.626, b = 11.844, c = 6.702 Å, α = 92.44°, β = 94.28°, γ = 105.70°, V = 579.89 Å3, Z = 10, and space group P.
Dwornikite, (Ni,Fe)SO4 · H2O, a member of the kieserite group from Minasragra, Peru
Authors: Milton Charles , Evans Howard T. , Johnson Robert G.
Published: December 2006

Dwornikite, (Ni1−xFex)SO4 · H2O is a member of the kieserite group, monoclinic with space group C2/c. Specimens from Minasragra, Peru with x ∼ 0.1 have a unit cell with a = 6.839(2), b = 7.582(2), c = 7.474(2) Å, and β = 117.85(2)°. The six strongest lines of the powder pattern are: 3.342 (12, 100), 4.732 (110, 70), 3.024 (200, 70), 4.754 (11, 50), 3.293 (021, 35), 2.491 (022, 35). The mineral occurs as fine grained white aggregates associated with vanadium sulphide ores containing patronite and bravoite, mixed with other oxidation products. New unit cell data for the synthetic end-member compounds NiSO4 · H2O and FeSO4 · H2O, and new X-ray powder data for retgersite (NiSO4 · 6H2O) are provided.
Ardaite—a new lead-antimony chlorosulphosalt
Authors: Breskovska V. V. , Mozgova N. N. , Bortnikov N. S. , Gorshkov A. I. , Tsepin A. I.
Published: December 2006

The first occurrence of new mineral ardaite (a chlorine sulphosalt) has been discovered in the Madjarovo polymetallic ore deposit (Bulgaria). The average composition is Pb 56.50, Ag 0.04, Sb 22.48, S 15.56, Cl 3.78, total 98.36 wt.%. The formula is Pb20–18 Sb12–24S34–36.5Cl6–8. The mineral occurs as fine acicular aggregates associated with galena, nadorite, a Cl-bearing robinsonite and Cl-beating semseyite, pyrostilpnite, silver- bearing tetrahedrite and anglesite.
Luddenite, a new copper-lead silicate from Arizona
Authors: Williams S. A.
Published: December 2006

Found at a small prospect in the Artillery Peaks area, Arizona. Luddcnite occurs in oxidized Cu-Zn ores with fluorite, alamosite, and cerussite. Colour nickel green, H = 4, G meas. 4.45.

Strongest X-ray lines are 7.361(10), 3.173(10), 2.918(8), 5.218(7), 4.226(5), 3.411(5), 2.888(5), 3.650(4). A possible cell found by Ito method is a = 7.85, b = 20.06, c = 14.72 Å, β = 90.78° (monoclinic). Optically (+), α = 1.852, γ = 1.867.

Chemical analysis by wet methods gave CuO 13.2%, PbO 35.1, SiO2 25.7, H2O 20.5, TiO2 (leucoxene impurity) 4.7. Not all water need be essential, hence Cu2Pb2Si5 O14·nH2O. The new mineral and name have been approved in advance of publication by the Commission on New Minerals and New Mineral Names, IMA.
Gobbinsite, a new zeolite mineral from Co. Antrim, N. Ireland
Authors: Nawaz Rab , Malone John F.
Published: December 2006

A chalky white, fibrous mineral, in the amygdales of Tertiary basalts from the Gobbins area, Co. Antrim, has been discovered to be a new mineral. It consists of fibrous dusters of lath-shaped crystals showing straight extinction with negative elongation. Its refractive index is ɛ 1.489, ω 1.494 (both ± 0.003) and specific gravity is 2.194 (meas.), 2.147 (calc.). The mineral is tetragonal with ɛ = c (elongation); a = 10.145, c = 9.788 Å. The strongest powder lines (in Å, intensity in brackets) are: 7.10, 4.10, 3.19(100); 3.10, 2.69(80); 5.07(50); 2.64(40). A spectrographic analysis shows major Si, Al, minor Ca, Na, Cu, and trace Fe. Two chemical and one probe analysis give the ideal formula Na4(Ca,Mg,K2)Al6Si10 O32.12H2O. The name gobbinsite (approved by the IMA Commission on New Mineral Names) is suggested after the locality. The type specimen (I7881) is preserved in the Ulster Museum.

Rotation and Weissenberg photographs of gobbinsite and garronite show doubled reflections, which are explained on the basis of submicroscopic twinning on (101). Relationship between gobbinsite and garronite is discussed and evidence is presented for the occurrence of minute amounts of a merlinoite-type mineral that forms regular intergrowths with gobbinsite and garronite.
Palladium minerals from Hope's Nose, Torquay, Devon
Authors: Clark A. M. , Criddle A. J.
Published: December 2006

Two palladium arsenide-antimonides have been found as small inclusions associated with native gold at Hope's Nose. One of the minerals has been identified as isomertieite; the other is chemically very similar to mertieite-II (Cabri et al., 1975). Electron probe microanalysis gives the formula of the isomertieite as (Pd10.89 Au0.08Cu0.03)Σ11.00(Sb2.01As1.99)Σ4.00 and of mertieite II as (Pd7.90Au0.07Cu0.01)Σ7.98(Sb2.43As0.59)Σ3.02. The relectance spectra of isomertieite in air and in oil at intervals of 10 nm from 400–700 nm are tabulated. The luminance values of the Hope's Nose isomertieite are 55.5 % in air and 42.5% in oil. The type specimen of isomertieite from Itabira, Minas Gerais, Brazil, has been re-examined; a new electron probe analysis is given and improved reflectance spectra are tabulated. The latter gives luminance values of 54.3% in air and 41.3% in oil.
The occurrence of pumpellyite in basic igneous rocks from the Coloured Series NE of Neyriz, Iran
Authors: Arvin M.
Published: December 2006

The occurrence of pumpellyite in Late Cretaceous volcanic rocks of the Coloured Series, NE of Neyriz, is reported for the first time. The form of the pumpellyite and its chemistry are described. The mineral assemblages of the prehnite-pumpellyite facies of metamorphism are present, indicating that burial metamorphism has occurred, a new factor to be considered in the tectonic evolution of the Zagros suture zone.
Microscopic rods in metallurgical slags
Authors: Wearing E.
Published: December 2006

Microscopic rods of wüstite and sulphide phases have been observed within silicate crystals from metallurgical slags. The rods, which are distinct from acicular crystals of accessory minerals, tend to be orientated perpendicular to the faces of the host crystal. These rods, and their constant orientation, are a product of the crystallization environment. It is proposed that they result from saturation of the melt with the relevant phase at the growth front of the silicate crystals. This microstructure is compared with known examples of microscopic rods and tubes in rocks.
A note on the occurrence of chevkinite, allanite, and zirkelite on St. Kilda, Scotland
Authors: Harding R. R. , Merriman R. J. , Nancarrow P. H. A.
Published: December 2006

The occurrence of three accessory minerals with significant rare earth contents in Tertiary acid rocks of St. Kilda is described. Allanite, zirkelite, and chevkinite were identified by electron probe analysis (with energy-dispersive attachment) and the chevkinite confirmed by X-ray diffraction. Brief comparison is made with other Tertiary occurrences of RE minerals. This is the first recorded occurrence of chevkinite in Great Britain.
New data for lansfordite
Authors: Hill R. J. , Canterford J. H. , Moyle F. J.
Published: December 2006

Euhedral crystals of the low-temperature mineral lansfordite, MgCO3 · 5H2O, have been prepared from saturated magnesium bicarbonate solutions at temperatures below 10°C. The crystals are monoclinic P21/a with a = 12.4758(7), b = 7.6258(4), c = 7.3463(6)Å, β = 101.762(6)°, V = 684.24Å3, Dcalc. = 1.693 g cm−3, Dobs. = 1.70(1) g m−3. At room temperature, the crystals slowly effloresce to produce pseudomorphs of nesquehonite, MgCO3 · 3H2O. Dehydration is complete at 300°C, with decarbonation taking place in the interval to 560°C. A new X-ray powder diffraction pattern is presented, and details of the infra-red absorption spectrum are discussed.
The crystal structures of aluminosilicate-sodalites: X-ray diffraction studies and computer modelling
Authors: Beagley B. , Henderson C. M. B. , Taylor D.
Published: December 2006

X-ray powder methods have been used to study the room-temperature structures of the synthetic sodalites: Li8(Al6Si6O24)Cl2, K7.6Na0.4(Al6Si6O24)Cl2, and Na8(Al6Si6O24)I2. Natural sodalite was also studied and the atomic coordinates show satisfactory agreement with those determined from the single-crystal data of Löns and Schulz (1967). The LiCl- and KCl- as well as the NaCl-sodalites refined in the expected sodalite space group P3n, but the NaI-sodalite fitted 13m better. The resulting structural data reveal shortcomings in the previous computer models for sodalite structures and an improved computer modelling procedure is devised which successfully predicts atomic coordinates, starting from the experimental a value and an estimate of the cationanion distance. The method incorporates the experimental result that the average T-O distance (T = Al, Si) throughout the samples is ∼ 1.678 Å, and Si-O and Al-O are set at 1.618 and 1.738 Å, respectively. Although T-O remains little changed throughout the samples, the data confirm the inverse relationship between ∠ T-O-T and the tetrahedron tilt angle ϕ, in which ∠ T-O-T approaches ∼ 160° as ϕ → 0° and the sodalite cage becomes fully expanded.
General comments on the identification of chlorites in thin sections
Authors: Saggerson E. P. , Turner L. M.
Published: December 2006

Although a ‘chlorite’ is usually simple to recognize in thin section because of its characteristic colour, form, and often very low or anomalous interference colours, the identification of the various species is more difficult and requires both chemical and X-ray work for accurate determination. Roy and others have demonstrated that chlorites are polymorphous and occur in two structural groups, the normal 14 Å chlorites and the 7Å septechlorites (Nelson and Roy, 1958). Many chlorite varieties may be found in both structural states, low-temperature end-members and compositionally extreme end-members favouring the septechlorite structure, especially antigorite, amesite, chamosite, greenalite, and cronstedtite. Phillips (1964) subsequently proposed that six variables, Y, R3+, R2+ , Σ, H, plus the appropriate structural designation, must be fixed to define completely a variety of the chlorite group and from this he developed a numerical system of classification. Unfortunately these specific chemical and structural properties cannot be directly recognized by normal optical methods.
The primary ore mineralogy of the Alderley Edge deposit, Cheshire
Authors: Ixer R. A. , Vaughan D. J.
Published: December 2006

The Alderley Edge deposit, Cheshire, England has been mined principally for Cu and Pb. Here, veins and disseminations occur in coarse-grained clastic sediments of Triassic age and are classified as belonging to the red-bed type of mineralization.

Examination of material in polished and thin section has shown the mineralization to be multiphase. The earliest opaque phases are associated with the diagenesis of the sandstones and include authigenic anatase, plus bravoite, pyrite, and chalcopyrite within authigenic quartz overgrowths. This stage of mineralization was followed by the formation of intergrown bravoite, pyrite, chalcopyrite, sphalerite, and galena accompanied by minor amounts of Ni-Co-Fe sulpharsenides, marcasite, and tetrahedrite cementing the clastic grains. This primary assemblage has undergone extensive alteration resulting in the formation of djurleite, covelline, and blaubleibender covelline accompanied by Pb and Zn carbonates and sulphates. Later, extensive shattering of the cemented clastic grains has been infilled by supergene Cu, Pb, and Zn carbonates and sulphates, limonite, and other secondary minerals.

Electron probe microanalysis of the sulphides shows the pyrite to contain significant Ni and Cu but lesser amounts of Co; the sphalerite to be an Fe-poor variety but to contain Cd, and the chalcopyrite to contain Sb. Ag is present in appreciable amounts in tetrahedrite and occurs in trace amounts in both sphalerite and chalcopyrite but not in galena. The concentration of Ag increases with the alteration of the primary sulphides to secondary sulphides. This is most clearly demonstrated by the alteration of chalcopyrite to an idaite-like phase and finally to djurleite when the Ag content increases from 0.10 to 2.35 wt. %.
Thermal aspects of the origin of Hebridean Tertiary acid magmas. II. Experimental melting behaviour of the granites at 1 kbar PH20
Authors: Thompson R. N.
Published: December 2006

Experimental melting equilibria at 1 kbar PH2O are reported for three early Tertiary granites from Skye and one from Rhum, together with a quartz monzonite from Ardnamurchan. The Hebridean Province leucogranites show cotectic melting behaviour, whilst associated ‘primitive’ (mostly adamellitic) acid plutons have silicate liquidi ∼ 925 °C and plagioclase liquidi ∼ 875 °C. At such high temperatures the morefusible crustal rock types of the region would be almost completely molten. If the Tertiary ‘primitive’ acid magmas were simple crustal melts, they would inherit the incompatible element ratios of their sialic progenitors. This is demonstrably not so. Minor element ratios in these plutons are consistent with extensive fractional crystallization during the evolution of their magmas. But it is, in most individual instances, extremely difficult to specify, either by thermal or geochemical arguments, whether (1) fractional crystallization followed sialic contamination of basic magmas or (2) mixing occurred between fractionation residua and sialic melts. Both the minor element ratios and cotectic melting behaviour of the Hebridean Province leucogranites are consistent with the view that they are products of extreme fractional crystallization of (sial contaminated) more-basic magmas. Nevertheless, it is clear—when the sequence and timing of emplacement of acid magmas within individual intrusive centres is considered—that very complex polycyclic combinations of fusion, fractionation, and re-fusion were involved in the evolution of these granites.

The solidi of the samples studied experimentally, together with published data, show a progressive rise in temperature as the compositions of the rocks diverge from the minimum melting composition in NaAlSi3O8-KAlSi3O8-SiO2 at 1 kbarH2O. This relationship is important when considering the likely nature of sialic contamination of basic to intermediate continental magmatic suites fed through reservoir systems which are swarms of dykes and, or, sills. Because salic low-solidus crustal rock types also show near-cotectic melting behaviour, the composition of the contaminant may be strongly biased towards these (usually minor) crustal units, rather than the ‘bulk’ or average crustal composition.
The geology and geochemistry of the strathy complex of north-east Sutherland, Scotland
Authors: Moorhouse Valerie E. , Moorhouse Steven J.
Published: December 2006

The Strathy complex is a fault-bounded block of the sub-Moine succession basement characterized by a marked aeromagnetic anomaly. XRF analyses of 94 rocks for 26 elements are used to illustrate the geochemistry of the complex. It comprises siliceous grey gneisses (50 analyses), subordinate amphibolite (13 analyses), hornblende gneiss (13 analyses), and ultramafites (1 analysis), with scapolite-diopside marble and calc-silicate rocks (3 analyses from Strathy, 14 analyses of other calc-silicates). Geochemically the Strathy gneisses are quite distinct from the adjacent Moine lithologies, being unusually low in K, Rb, La, and Ce, and high in SiO2 and Na2O, whilst differences in immobile elements such as Ti and Zr preclude their derivation from a Moine source. The Strathy complex is unlike other high-grade gneiss terrains and apparently acquired its characteristic geochemical features by the removal of an anatectic melt under amphibolite-facies conditions leaving a refractory residue of quartz, plagioclase, Ca-poor amphibole, and garnet ± staurolite in siliceous gneisses. Subsequent influx of water, retrogression to biotite-bearing assemblages, production of sillimanite, and anateclic trondhjemitic melts took place during the maximum metamorphism of the surrounding Moine. The complex is considered to have originated as a dacitic supracrustal sequence with minor sediments and mafic-ultramafic intrusives. REE and Y abundances suggest a Proterozoic age, possibly as part of the Laxfordian cycle.
Chemical distinction between igneous and metamorphic orthopyroxenes especially those coexisting with Ca-rich clinopyroxenes: a re-evaluation
Authors: Rietmeijer Frans J. M.
Published: December 2006

A previously suggested simple relationship in a diagram of(Al2O3vs. MgO + FeO + Fe2O3)opx for the distinction between igneous and metamorphic orthopyroxenes is shown to be inadequate. A revised diagram is presented and its limitations are discussed. A diagram showing Fe2+/(Fe2+ + Mg) vs. 100Ca/(Fe2+ + Mg + Ca) for orthopyroxenes coexisting with Ca-rich clinopyroxenes proves to be useful for the discrimination of igneous and metamorphic orthopyroxenes and for evaluation of the extent and physical conditions of regional orthopyroxene re-equilibration.
Equilibria in the Mg-rich part of the pyroxene quadrilateral
Authors: Jenner G. A. , Green D. H.
Published: December 2006

Pyroxene phase relations in the Mg-rich corner of the pyroxene quadrilateral, at 1 atmosphere, have been reinvestigated. Experimental studies on sixteen selected compositions in the systems CMS and CFMS were undertaken in the temperature range 1100–1400 °C. The results of this study clarify our understanding of the pyroxene stability relations at low pressure. In particular, the demonstration that there is a high-temperature stability field of orthoenstatite denies the existence of a stable (or real) invariant point defined by the reactions OE = PE + DI, PE + DI = PI, and OE + DI = PI, in the system CaMgSi2O6-Mg2Si2O6. New phase relations, consistent with the experimental findings of this and other studies, for the Mg-rich corner of the pyroxene quadrilateral are presented. These new phase relations may be of use in interpreting the origin of volcanic rocks containing magnesian pigeonite.
Crystallization of plagioclase, augite, and olivine in synthetic systems and in tholeiites
Authors: Biggar G. M.
Published: December 2006

Experimental data from the system CaO-MgO-Na2O-Al2O3-SiO2 and from the system CaO-MgO-FeO-Al2O3-SiO2 are used to show the nature of the changes in composition, with temperature and with pressure, of liquids in equilibrium with augite, plagioclase, and olivine as MgO in the system CaO-MgO-Al2O3-SiO2 is partially replaced by FeO and as Na2O replaces CaO. As differentiation of tholeiitic basalts proceeds, Fe/Mg increases, Na/Ca increases, and normative hypersthene increases and these effects alter the solubilities, and hence the proportions of augite, plagioclase, and olivine which co-precipitate. In particular olivine becomes more soluble (less is precipitated) as Fe/Mg increases; plagioclase becomes more soluble but augite less soluble as Na/(Na + Ca) increases; augite also becomes less soluble as normative hypersthene increases, and as pressure is reduced during ascent.

Experimental data from remelted ocean tholeiites encounter the same equilibrium and are presented and compared with the data from synthetic systems.

Some natural examples of daughter liquids related to parents by crystallization of augite, plagioclase, olivine, are combined with the experimental data and with some model calculations to demonstrate that only a very limited range of proportions of augite : plagioclase: olivine (approximately 30 : 50 : 15 to 20 : 60: 20) produces daughter liquids which lie on the major element variation of the tholeiitic basalt series. Other proportions lead to daughter liquids which are not basalts. In the light of these restrictions, several recent publications are reinterpreted as examples of fractionation of augite, plagioclase, and olivine, rather than examples of partial melting. The recognition of the small effect that massive (50 to 83%) crystallization has on basaltic chemistry by contrast with the large effect that small accumulations of phenocrysts can have is particularly emphasized in this reinterpretation.

Comparisons and possible relationships are suggested between some low-K2O, low-TiO2 tholeiites; some calcic-, aphyric-, dykes of some tholeiitic provinces; some chilled margins of some layered intrusions; some basalts from Iceland, and some basalts from the ocean ridges.
Crystal-chemical characterization of NaAlSiO4 with the CaFe2O4 structure
Authors: Yamada Hirohisa , Matsui Yoshito , Ito Eiji
Published: December 2006

A high-pressure modification of NaAlSiO4, with the calcium ferrite structure was synthesized at pressures higher than 24 GPa using a double-stage split-sphere type high-pressure apparatus. The unit cell dimensions are: a=10.1546(8), b=8.6642(8), c= 2.7385(4) Å, and V = 240.93(3) Å3 with the space group Pbnm. Calculated density is 3.916(1) g/cm3. The crystal structure was determined by the ordinary powder X-ray method. Both M1O6 and M2O6 octahedra run parallel to the c-axis, forming edge-shared double chains. The shared edges exhibit remarkable shortening (2.25–2.39 Å). Sodium atoms are located in the ‘tunnel’ formed by the linked double chains, being in eightfold co-ordination. The structure is very similar to that predicted by Dempsey and Strens (1976) with the aid of the DLS method. The possible instability of the calcium ferrite type of Mg2SiO4 is discussed.
Geochemistry and mineralogy of Triassic sandstones and implications for groundwater composition
Authors: Spears D. A.
Published: December 2006

Borehole samples from the Wildmoor Sandstone Formation have been analysed for whole-rock major and trace elements and the mineralogy determined by X-ray diffraction and conventional thin sections. The forty-two samples studied were obtained from boreholes drilled in a long established effluent site and from control boreholes away from the site. Elements are associated with one or more of calcite, quartz, K-feldspar, and clay plus oxide. The most important mineralogical change due to current infiltration is progressive loss of calcite. Background element concentrations are established and only Pb, and in one sample Cu and Zn, are found in higher concentrations representing anthropogenic additions to the system.
The dependence of alumina and silica contents on the extent of alteration of weathered ilmenites from Western Australia
Authors: Frost M. T. , Grey I. E. , Harrowfield I. R. , Mason K.
Published: December 2006

The distribution of the minor impurities, aluminium and silicon, between co-existing phases in altered ilmenite grains from three Western Australian localities has been investigated using SEM and electronmicroprobe analyses. A striking dependence of the impurity levels on the Ti/(Ti + Fe) fraction is observed. For compositions with Ti/(Ti + Fe) between 0.45 and 0.60, i.e. between ferrian-ilmenite and pseudorutile, the impurity content is virtually independent of Ti/(Ti + Fe), and is very low (0.2 wt. % Al2O3. 0.05 wt. % SiO2). For compositions between those of rutile and pseudorutile, there is a direct correlation between the impurity contents and the Ti content of the alteration phase. The impurity levels increase with increasing Ti/(Ti+Fe) to about 3 wt. % Al2O3and 1 wt. % SiO2for compositions close to TiO2. Thus during the latter stages of ilmenite alteration, alumina and silica are extracted from the ambient environment and are coprecipitated with, or adsorbed on to, the alteration products. The observed dependence of the alumina and silica contents on extent of alteration is consistent with a two-stage alteration mechanism earlier proposed (Grey and Reid, 1975).
A Mössbauer study of some Australian iron ore minerals
Authors: Fysh S. A. , Ostwald J.
Published: December 2006

Six specimens of Australian iron ore, three hematite-rich and three goethite-rich, have been investigated by Mössbauer spectroscopy at both 300 K and 4.2 K. The resulting spectra provide data relevant to crystallite particle size variations in the hematite and goethite, the extent of isomorphous replacement, and the existence within one specimen of a poorly defined goethite-like material.
Synthesis, properties, and dehydroxylation of members of the crandallite-goyazite series
Authors: Gilkes R. J. , Palmer B.
Published: December 2006

Unit-cell parameters of synthesized members of the crandallite (a = 7.007 Å, c = 16.216 Å)-goyazite (a = 7.013 Å, c = 16.650 Å) series vary linearly with composition between end-members. Most members of the series consist of 0.1 μm platy crystals, but crandallite also contains some larger (1–5 µm) tapered crystals elongated along the c axis.

With increasing Sr substitution the dehydroxylation temperature decreases from c. 475 °C for crandallite to 420 °C at 20 mole % Sr, and then increases to 440 °C for goyazite. Partial dehydroxylation of crandallite is accompanied by contraction of the c unit cell parameter and expansion of a, thereby retaining an unaltered unit cell volume. The much greater sensitivity of c to both Sr substitution and dehydroxylation may be due to the rigidity of continuous sheets of Al(OH)4O2 octahedra which are parallel to the (001) plane in these minerals.
Iron-rich talc-opal-minnesotaite spherulites and crystallochemical relations of talc and minnesotaite
Authors: Kager P. C. A. , Oen I. S.
Published: December 2006

Zoned spherulites in greenalite-siderite-silica rocks of the Emilia-San Valentin lead-zinc deposit, Sierra de Cartagena, SE Spain, show a core of iron-rich talc, (Mgl.8Fel.2)Si4Ol0(OH)2, an intermediate zone of opal-chalcedony, and a rim of minnesotaite, (Fe2.7Mg0.3)Si4Ol0(OH)2. Crystalllization of the spherulites, presumably from undercooled silica sols carrying dissolved Mg and Fe, began with the non-equilibrium precipitation of metastable iron-rich talc; the residual fluids enveloping the growing spherulites became more iron-rich in composition until metastable equilibrium between iron-rich talc and iron-enriched residual liquid impeded the further growth of the iron-rich talc; the spherulites were then overgrown by colloidal silica flocculates and a rim of minnesotaite precipitated from the iron-enriched residual fluid. The proposed crystallization model implies that, if talc and minnesotaite represent an isomorphic series, under equilibrium conditions there is a broad immiscibility region in the series.
The geochemistry of mafic and ultramafic from the Archaean greenstone belts of Sierra Leone
Authors: Rollinson H. R.
Published: December 2006

The Archaean (c. 2800 Ma) ultramafic rocks in eastern Sierra Leone cut basalt lavas and are mostly olivine-rich cumulates either iron-rich (Fo85–86) and derived from a basaltic or picritic parent, or more magnesian (Fo92–93) derived from an ultramafic melt with c. 18–25 wt. % MgO. In central Sierra Leone the ultramafic rocks are lavas predating tholeiitic basalts.

The basalts show a wide variation in Zr/Y, suggesting that garnet was present in the source region of some of these rocks but not others. This implies that melting took place at different depths in the mantle. The REE evidence for basaltic rocks in the upper part of the Nimini belt succession suggests that they were derived from a mantle source region which had already suffered melt extraction. Ti/Zr ratios in the basaltic rocks are also variable and individual belts define different trends on a Ti vs. Zr plot implying that the basaltic rocks evolved in geographically distinct magma chambers. It is likely that the basaltic rocks evolved from a parental liquid with Ti/Zr = 90 via shallow level crystal fractionation. The source region for these rocks therefore had a lower than chondritic Ti/Zr.

There are two possible models for the basaltic and ultramafic magmas in the Sierra Leone greenstone belts. First that the ultramafic and basaltic liquids were derived from mantle diapirs of differing size, but originating in the same region of the mantle. Ultramafic liquids were produced in small diapirs, which store large melt fractions, and basaltic liquids in larger diapirs which segregate larger melt fractions. A second model is based upon the double diffusion process suggested for magma chambers at mid-ocean ridges and involves a transient magma chamber from which basalts, derived from parental ultramafic liquids, are erupted, with ultramafic liquids rising directly to the surface when the magma chamber is frozen. The available data does not discriminate between these two models.
Buddingtonite (NH4-feldspar) in the Condor Oilshale Deposit, Queensland, Australia
Authors: Loughnan F. C. , Roberts F. Ivor , Lindner A. W.
Published: December 2006

Buddingtonite of similar composition and properties to that described from the type area, is uniformly distributed throughout the upper 600 m of strata in the Condor Oilshale Deposit near Proserpine, Queensland. The mineral, which constitutes up to 16% and averages nearly 10 % of the strata, is associated with abundant montmorillonite, siderite, and quartz as well as minor amounts of disordered kaolinite, illite, calcite, pyrite, cristobalite, and an unnamed species of the jahnsite group. The buddingtonite is concluded to be of diagenetic origin. It developed in an ammonium-rich environment, most probably at significant depth within the mud beneath a stratified lake. Its progenitor, however, remains unknown. The occurrence of this mineral is also of interest in that ammonia could prove an important by-product in the commercial exploitation of the oilshales.
Clinopyroxene solid solutions and water in magmas: results in the system phonolitic tephrite-H2O
Authors: Dolfi D. , Trigila R.
Published: December 2006

Clinopyroxene solid solutions crystallized at Ptot = 2 kbar in the natural system phonolitic tephrite-H2O (lava type from Etna eruption 1971) indicate a linear increase of ln Xcpxcats with H2Oliq %. After coupling this with the In Xcpxcats pressure dependence found through experiments, a simple relation has been set up for clinopyroxene- and plagioclase-bearing magmas. This relation allows us to calculate the amount of water dissolved in the melt, at any known pressure in the crustal range.
Chemical variation in garnets from aplites and pegmatites, peninsular Thailand
Authors: Manning D. A. C.
Published: December 2006

Electron microprobe analyses of almandine-spessartine garnets from pegmatites and aplites from the Hub Kapong batholith and Phuket Island in peninsular Thailand show three types of zoning. Garnets from pegmatites show extreme zoning, with Mn-rich cores (⋍ 80 % spessartine) and Mn-poor rims (⩾ 40 % spessartine), whereas those from aplites are either unzoned (35–40% spessartine) within the limits of detection, or have Mn-enriched rims (cores 45 %, rims 55 % spessartine). The origin of the three types of zoning is considered to reflect different crystal growth histories in each case. The pegmatitic garnets grew under conditions favourable for the development and preservation of marked concentration gradients—low nucleation density, rapid growth rate and slow cation diffusion rates for the crystal and rapid diffusion rates for the pegmatitic liquid. The aplitic garnets had a more complex growth history, with slower growth rates and faster diffusion rates for the crystal, coupled with slower diffusion rates within the aplite magma, tending to prevent the formation and preservation of concentration gradients. Subsequent resorption of aplitic garnets at lower temperatures gave rise to Mn-rich rims because of the preferential retention of Mn by the garnet; lower cation diffusion rates within the crystal permitted these marginal concentration gradients to be preserved.
Chemistry of biotites from a zoned granitic pluton in Morocco
Authors: Mahmood A.
Published: December 2006

Chemical analyses and structural formulae of biotites from the Zaër pluton, a zoned granitic body in the Central Hercynian Massif of Morocco, are presented. The pluton grades from more mafic single-mica granodioritic facies near the margin to more felsic two-mica granitic facies in the central part. There is a relationship between the composition of the biotites and that of the host rocks. Biotite composition in the internal two-mica facies was influenced by a hydrothermal phase.
Bostwickite, a new calcium manganese silicate hydrate from Franklin, New Jersey
Authors: Dunn Pete J. , Leavens Peter B.
Published: December 2006

Bostwickite, CaMn63+Si3O16-7H2O, is a new species from the Franklin Mine, Franklin, New Jersey. Chemical analysis yielded MgO 0.9, CaO 5.1, Mn2O3 56.3, Fe2O3 0.5, Al2O3 1.0, As2O5 1.0, SiO2 20.1, H2O [15.1], sum = 100.0%. This yields (Ca0.76Mg0.19)Σ0.95(Mn5.973+Fe0.053+)Σ6.02(Si2.80Al0.16As0.075+)Σ6.02(Si2.80Al0.16AS5+0.07)Σ3.03O16·7.01H2O, corresponding to the idealized formula. The strongest lines in the X-ray powder diffraction pattern are (d, I): 11.3, 100; 3.548, 30; 2.898, 30; 2.567, 40; 2.262, 25; 2.238, 25; 1.470, 25. Bostwickite is dark red in colour; hardness c. 1 (Mohs'); density (meas.)= 2.93 g/cm3. It occurs in radial aggregates of acicular compound crystals. Optically, bostwickite is biaxial negative with 2Vα = 25deg; α = 1.775, Β = 1.798, γ = 1.800;, dispersion strong, r > v; strongly pleochroic with α = β redbrown, γ = yellow-brown; absorption is α = β = γ. Bostwickite is named in honour of Richard C. Bostwick, collector and compiler of data on the minerals of Franklin and Sterling Hill.
Tristramite, a new calcium uranium phosphate of the rhabdophane group
Authors: Atkin D. , Basham I. R. , Bowles J. F. W.
Published: December 2006

Tristramite, a new mineral of the rhabdophane group, has the composition (Ca0.54U4+0.29Fe3+0.17)Σ1.00 [(PO4)0.79(SO4)0.12(CO3)0.07]Σ0.98·1.77H2O. It occurs as a late-stage replacement or matrix to brecciated uraninite (var. pitchblende) associated with sulphides in hydrothermal veins related to Hercynian granites in south-west England. It is hexagonal, space group P6222, with a 6.913 ± 0.003 Å and c 6.422 ± 0.006 Å. The strongest lines of the indexed powder pattern are 2.99 (100), 2.83 (100), 2.14 (50), 1.850 (50), 5.99 (40), 4.37 (40), 3.46 (30). For comparison, new indexed powder data for rhabdophane from Fowey Consols, Cornwall, are included. The mineral is pale yellow to greenish yellow, uniaxial positive with ω 1.644 and ε 1.664, and does not fluoresce in either short-or long-wave ultraviolet light. The habit is acicular or fibrous and no cleavage has been observed. Density (g/cm3) 3.8–4.2 (meas.), 4.18 (calc.).