bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluvial metal transport near sources of acid mine-drainage: Relationships of soluble, suspended and deposited metal
Authors: Boult Stephen 
Published: December 2006

AbstractThe Afon Goch (Anglesey, UK) is a short (12 km source to estuary) stream highly contaminated by acid mine drainage (AMD) throughout its length, due to past-mining at the head of the stream. Metal distribution is strongly controlled by the pH, which increases downstream particularly at confluences with two unpolluted tributaries. A pH increase causes precipitation of metals, primarily Fe as hydroxide, thus altering the transport of the metal load, potentially allowing storage of metal within the river as deposited material. However, further work suggests that the controls on whether metal can behave non-conservatively, and therefore the controls on metal distribution, are more complicated than being purely pH dependent. This is because much of the Fe load, even at the low pH at the head of the stream, is not soluble Fe3+ but colloidal Fe hydroxide. Consequently, coagulation is a requisite intermediate step between precipitation and potential for settling. It is possible that in reaches of the stream away from tributary confluences, the process of coagulation is the predominant influence on metal distribution. Furthermore, because much of the metal load in the water column is very fine, its deposition results in a sediment in which the metals can be intimately associated with a biofilm at the sediment/water interface. Such associations change both deposition and erosion characteristics of the sediment and have implications for subsequent diagenesis and mineral morphology.
Synthetic armalcolite and pseudobrookite
Authors: Medvedev A. Ya. 
Published: December 2006

AbstractArmalcolite and pseudobrookite have been crystallized from synthetic melts of basaltic composition with variable amounts of added TiO2. It was found that the composition of the armalcolite and pseudobrookite are dependent on the TiO2 content of the melt and the conditions (particularly oxygen fugacity, but also temperature and quenching rate) of formation. The maximum Al2O3 content of pseudobrookite appears to be ∼14–15 wt.% Al2O3, a spinel-like phase being exsolved at higher Al2O3 concentrations. Generally armalcolite is formed at low pO2 and pseudobrookite at higher oxygen fugacities.
Cadmium substitution in miargyrite (AgSbS2) and related phases: an experimental reconnaissance
Authors: Kelleher I. , Redfern S. A. T. , Pattrick R. A. D. 
Published: December 2006

AbstractAn experimental study of cadmium substitution into AgXS2 phases (X = As, Bi, Sb) indicates significant amounts of cadmium can be incorporated in the structure by the mechanism 2Cd ⇌ Ag + X. The limit of substitution of Cd in the high-temperature polymorph of miargyrite, β-AgSbS2 is 6.2 at.%, whereas the low-temperature polymorph, α-AgSbS2, can accommodate at least 12 at.% cadmium. Substitution of Cd into the cubic β-AgSbS2 induces a small monoclinic distortion and the unit cell becomes pseudo-cubic. The α ⇌ β transition in Cd-substituted miargyrites is modified by the solute ions, with both a reduction of Tc and transition smearing evident. Similar effects are also recorded in Cd-substituted AgAsS2 and AgBiS2.
Transition metal rutiles and titanates from the Deadhorse Creek diatreme complex, northwestern Ontario, Canada
Authors: Platt R. Garth , Mitchell Roger H. 
Published: December 2006

AbstractThe main mineralized zone of the West subcomplex of the Deadhorse Creek diatreme complex, northwestern Ontario possesses an exotic mineralogy. Mineralization involves the first-order transition metals (principally Sc, Ti, V, Cr, Mn, and Fe), the second-order transition metals (principally Zr and Nb), the lanthanides, the actinides (principally Th and U), Be, Ba and Sr. Minerals include phenacite, zircon, uraninite, thorite, monazite-(Ce), xenotime-(Y), barylite, thortveitiite, hollandite, tyuyamunite, a number of unknown and as yet undescribed species, and those minerals more specifically described in this paper. These are Cr-V-Nb rutile, V-rich members of the crichtonite series, and a titanate of general composition (Cr,V3+,Fe3+)2(Ti,V4+,Nb)O5.Similar to rutiles reported from alkaline rocks in general, the Deadhorse Creek rutiles are enriched in Cr and Nb, with the latter element attaining some of the highest recorded values. V contents are also unusually high and this element is thought to exist in both the tri- and tetravalent states.The V-rich crichtonites are essentially vanadium analogues of crichtonite and lindsleyite. M-site Nb and V are the highest yet recorded. A-site cations are dominated by Ba and Sr with an inverse relationship together with lesser but significant amounts of Ca and Pb. Although not of upper mantle origin, they plot in the upper mantle LIMA quadrant of TiO2vs. FeO + Fe2O3 + MgO (Haggerty, 1991).(Cr,V3+,Fe3+)2(Ti,V4+,Nb)O5 is thought to be a member of an homologous series of type (Cr,V3+,Fe3+)2p(Ti,V4+,Nb)2p+qO5p+4q with p = 1 and q = 0 and a V3O5-type structure. Whether this structure is ultimately derived from that of rutile or from α-PbO2 by crystallographic shear is not known.The rutiles and titanates discussed here are thought to have formed from hydrous alkaline solutions which have scavenged the necessary elements from a mafic/ultramafic source. The origin of the solutions is not specifically known although the magmatic activity associated with the spatially related Coldwell alkaline complex and/or the Prairie Lake complex are both potential sources. Both complexes contain the necessary mafic/ultramafic rocks.
Ba-rich micas from the Yindongzi-Daxigou Pb-Zn-Ag and Fe deposits, Qinling, northwestern China
Authors: Jiang Shao-Yong , Palmer M. R. , Li Yan-He , Xue Chun-Ji 
Published: December 2006

AbstractElectron-microprobe analyses of muscovite, biotite, and feldspar are reported for the stratiform Yindongzi—Daxigou Pb—Zn—Ag and Fe deposits of Qinling, northwestern China. The micas are characterized by high Ba levels in banded albite-carbonate rocks that host the deposits. The biotite is also rich in Cl, as is biotite in the nearby Tongmugou Pb-Zn deposit, although biotite and muscovite from this deposit lack Ba enrichment. It is likely that the Ba-rich micas in the Yindongzi-Daxigou deposits formed contemporaneously from the diagenesis and/or regional metamorphism of hydrothermally altered clay minerals, with the barium being derived from entrained pore fluids that may represent relict hydrothermal fluids associated with ore deposition. During the formation of coexisting muscovite and biotite, barium is preferentially partitioned into muscovite and chloride into biotite. Together with the presence of baryte rocks in the bedded ores, these data suggest that ore deposition in the Yindongzi—Daxigou deposits took place in a more oxidising environment than in the nearby Tongmugou deposit. This difference is attributed to the contrasting sedimentary environments of the two deposits, with the Yindongzi—Daxigou deposits having formed under shallow, oxic conditions and the Tongmugou deposit under deeper, anoxic conditions.
Fe-bearing trioctahedral micas from Mont Saint-Hilaire, Québec, Canada
Authors: Lalonde A. E. , Rancourt D. G. , Chao G. Y. 
Published: December 2006

AbstractWe document the occurrence of Fe-bearing trioctahedral micas in the Poudrette quarry in the Mont Saint-Hilaire alkaline intrusion, characterize them by microprobe analysis, Mössbauer spectroscopy, X-ray diffraction, and optical measurements, describe their mineral chemistry, and discuss their petrological significance. In the nepheline and sodalite syenite, biotite and annite occur as coarse crystals characterized by low Al content (typically 2 atoms per formula unit, a.f.u.), high Mn content (typically 0.2 to 0.8 a.f.u.) and variable Fe/(Fe+Mg) values from 0.61 to 0.97. In the gabbro, biotite is less Fe-rich, has lower Mn content and high Ti content. Phlogopite is found as small metamorphic crystals in marble xenoliths within the syenite and siderophyllite occurs as large crystals in a metasomatized albitite dyke. Fe3+/Fetot values extend from 0.079 in the siderophyllite to 0.282 in a high-Fe3+ annite. All of the micas except for the phlogopite have high contents of (Fe3+)iv (∼0.13 to 0.45 a.f.u.) despite the high availability of Al in the rocks. We suggest that the high (Fe3+)iv amounts are caused by the high Mn abundance via a local structural mechanism. The great variety of mica encountered at Mont Saint-Hilaire reflects the highly heterogeneous conditions that prevailed during magmatic and postmagmatic crystallization in this intrusion.
Ultra-high pressure aluminous titanites in carbonate-bearing eclogites at Shuanghe in Dabieshan, central China
Authors: Carswell D. A. , Wilson R. N. , Zhai M. 
Published: December 2006

AbstractPetrographic features and compositions of titanites in eclogites within the ultra-high pressure metamorphic terrane in central Dabieshan are documented and phase equilibria and thermobarometric implications discussed. Carbonate-bearing eclogite pods in marble at Shuanghe contain primary metamorphic aluminous titanites, with up to 39 mol.% Ca(Al,Fe3+)FSiO4 component. These titanites formed as part of a coesite-bearing eclogite assemblage and thus provide the first direct petrographic evidence that AlFTi−1O−1 substitution extends the stability of titanite, relative to rutile plus carbonate, to pressures within the coesite stability field. However, it is emphasised that A1 and F contents of such titanites do not provide a simple thermobarometric index of P—T conditions but are constrained by the activity of fluorine, relative to CO2, in metamorphic fluids — as signalled by observations of zoning features in these titanites.These ultra-high pressure titanites show unusual breakdown features developed under more H2O-rich amphibolite-facies conditions during exhumation of these rocks. In some samples aluminous titanites have been replaced by ilmenite plus amphibole symplectites, in others by symplectitic intergrowths of secondary, lower Al and F, titanite plus plagioclase. Most other coesite-bearing eclogite samples in the central Dabieshan terrane contain peak assemblage rutile often partly replaced by grain clusters of secondary titanites with customary low Al and F contents.
The conditions of metamorphism of a grossular—wollastonite vesuvianite skarn from the Omey Granite, Connemara, western Ireland, with special reference to the chemistry of vesuvianite
Authors: Ahmed-Said Y. , Leake Bernard E. 
Published: December 2006

AbstractThe Fountain Hill skarn, which was produced by thermal metamorphism of impure limestone in the Omey Granite aureole, consists of wollastonite, calcite, grossular-andradite garnet, diopside, B-free vesuvianite and small amounts of albite, K-feldspar and quartz. Zoning in vesuvianite is, overall, independent of birefringence but oscillatory concentric zoning in the mineral is controlled mainly by Ti. In addition to extensive within-site substitutions (e.g. F for OH in the OH-sites, Fe2+ for Mg, Fe3+ for Al, Ti for Al etc. in the Y-sites), there are significant cross-site combined substitutions involving Y-X and Y-Z but not X-Z sites so that ideal solution models for this mineral are not applicable. The thermodynamic mole fraction of Hoisch (1985) is modified to account for the excess of the ΣY cations in the Y sites and can be applied to both B-bearing and B-free vesuvianites. Using the thermodynamic dataset of Holland and Powell (1990) and taking into account the existence of andalusite, sillimanite and corundum in associated pelites, leads to the conclusion that the metamorphic conditions were about 640±20°C and 3.3±0.3 kb at 0.15±0.05 XCO2.
Blueschist-to-Greenschist Transition and the P-T Path of Prasinites from the Lavrion Area, Greece
Authors: Baltatzis Emmanuel 
Published: December 2006

AbstractThe Lavrion area is part of the Attic-Cycladic massif. Blue amphibole analyses revealed that they are glaucophane or ferroglaucophane. Ca-amphiboles are characterized as actinolite or actinolitic hornblende. The Ps component of epidotes from the glaucophane-bearing rocks varies from 25.42–30.89%, whereas the Ps component of epidotes from the greenschist assemblages ranges from 23.81–26.88%. Chlorites show narrow compositional variations of ferromagnesian ratios (Xmg=0.48–0.53). Albites are almost pure Ab100. The Kfeldspar present has a low Ab content. The evolution of the prasinites studied is characterized by the progressive transformation of eclogite facies (?) rocks through epidote blueschists into greenschists. A P-T path for the prasinites is presented indicating epidote blueschist facies at P-T conditions of around 7.0–7.5 kbar and 300–340°C. Pressures of 4.0–4.5 kbar and temperatures around 340–360°C are estimated for the subsequent overprint in the greenschist facies. The path EBS to GS conditions followed under nearly isothermal uplift.
Distribution of boron, lithium and beryllium in ocean island basalts from French Polynesia: implications for the B/Be and Li/Be ratios as tracers of subducted components
Authors: Dostal J. , Dupuy C. , Dudoignon P. 
Published: December 2006

AbstractThe study focuses on the distribution of B, Be, Li, rare earth elements (REE), high-field-strength elements (HFSE), Th, U and Pb in fresh and hydrothermally altered ocean island basalts (OIB) from French Polynesia, and evaluates B/Be and Li/Be ratios as potential tracers of subducted components in the mantle. Hydrothermal solutions affecting the rocks during cooling were derived from meteoric water, sea water and magmatic fluids. The concentrations of REE, HFSE, Th and Be in the OIB were not affected by secondary processes except during advanced stages of subaerial hydrothermal alteration where saponite was a dominant secondary phase. This alteration modified the contents of these elements, changed REE patterns and produced a positive Ce anomaly. The subaerial and submarine hydrothermal alteration (T ∼ 70–100°C) may change U concentrations in OIB, whereas Pb was only marginally redistributed during alteration.Boron was enriched during submarine and subaerial hydrothermal alteration but was not noticeably affected in basalts altered by magmatic fluids at T > 200°C. Like B, the mobility of Li during the alteration varies with fluid temperature. Lithium became enriched in the basalts during advanced stages of lower T hydrothermal alteration (<100°C). However, this element was partly removed from the rocks during higher T alteration (>200°C) by magmatic fluids. Boron, Be and Li behave as incompatible trace elements in basaltic magmas. Beryllium content in primitive mantle is estimated to be 0.07 ppm. Fresh Polynesian OIB have low abundances of B and Li and low B/Be (2–5) and Li/Be (2.5–5) ratios compared with volcanic arc rocks, marine sediments and altered oceanic crust. Various OIB including even those which have HIMU- and EM-affinities have similar overlapping B/Be and Li/Be ratios. Both B and Li are probably stripped from a lithospheric slab during subduction-related metamorphism and are, thus, not involved in deep mantle recycling. The mantle-normalized trace element abundances of MORB and OIB usually display patterns characterized by negative B, Pb and Li anomalies. The patterns of continental crust and crustal rocks have distinct positive anomalies for these elements whereas continental basaltic rocks have variable relative abundances of B, Pb and Li. The anomalies of these elements in basalts can be useful in discriminating their tectonic setting and constraining the mantle source regions of basalts.
A Model and Simulation of Branching Mineral Growth from Cooling Contacts and Glasses
Authors: Fowler Anthony D. , Roach Daniel E. 
Published: December 2006

AbstractSilicate minerals grown from glasses, and rapidly cooled melts, often have non-compact branching or ‘spherulitic’ morphology. The branching patterns are observed in volcanic rocks, glasses, meteorites, slags and sometimes in shallow level intrusive rocks. Experiments, observations, theory and simulations all support the concept that the crystal morphology is the result of growth under diffusion limited conditions. We show that in a silicate melt under appropriate conditions the equations for heat transfer and chemical-diffusion reduce to the Laplace equation. This means that the temperature or chemical gradient is a steady state field. Interaction between this field and a random variable (Brownian motion of growth species) is modelled and yields complex branching objects. The growing cluster affects the field such that an in-filled structure cannot be formed. The branching structures of the model crystal are remarkably similar to those formed in nature, and to those produced in laboratory experiments, implying that the model captures the essence of the branching-growth process.
Temperature-dependent disorder in a natural Mg-Al-Fe2+-Fe3+-Spinel
Authors: Della Giusta Antonio , Carbonin Susanna , Ottonello Giulio 
Published: December 2006

AbstractA natural Mg-Al-Fe spinel from the Balmuccia peridotite (Italian Western Alps) was annealed atTbetween 650 and 1150°C, under controlled oxygen activity, and quenched in H2O. Twenty-three cation distributions were calculated from XRD structural refinements in tandem with microprobe analysis, and verified by Mössbauer spectroscopy in the case of unheated samples.Unheated crystals showed essentially ordered distribution of Fe3+in octahedral and Fe2+in tetrahedral sites, the only intracrystalline disorder being represented by ∼0.12 atoms per formula unit of[4]Al and[6]Mg. Thermal runs and quenching maintained substantially ordered distribution of Fe2+and Fe3+up to ∼990°C and produced continuous[4]Mg-[6]Al exchange. Between 990 and 1150°C, the previous order of Fe2+-Fe3+appeared to change slightly,[6]Fe2+reaching ∼0.04 afu and[6]Mg ≅[4]Al ≅ 0.24 afu at the highestT. After quenching from this temperature, Fe2+still resided mainly in the T site. Some previously heated crystals underwent reordering on lowering of the temperature.Experimental data, integrated with existing literature, enabled cation-oxygen distance in this structure to be improved. Results from annealed samples allowed the formulation of an experimental thermometric function based on Mg-Al intracrystalline disorder.
The occurrence of niobian zirconolite, pyrochlore and baddeleyite in the Kovdor carbonatite complex, Kola Peninsula, Russia
Authors: Terry Williams C. 
Published: December 2006

AbstractThe compositions and textural relationships of the oxide minerals zirconolite, pyrochlore and baddeleyite are described. These occur as accessory minerals, often intergrown with each other, from a phoscorite rock associated with the Kovdor carbonatite complex. Both the zirconolite and baddeleyite have relatively high concentrations of Nb and Ta; the pyrochlore is rich in U and Ta. Backscattered electron images, coupled with detailed microprobe analyses, reveal complex compositional zoning in zirconolite and pyrochlore which reflect changes in the fluid composition during growth of these minerals. A comparison is made of incompatible element ratios Zr/Hf, Nb/Ta and Th/U between the three accessory minerals.
A natural ferrous substituted saléeite from Arcu su Linnarbu, Capoterra, Cagliari, Sardinia
Authors: Vochten R. , Van Springel K. 
Published: December 2006

AbstractFerrous substituted saléeite is a new variety of saléeite from Arcu su Linnarbu, Sardinia. It is tetragonal with a = 6.982(2) c = 19.660(2) Å, Z = 2; the ideal formula is (Mg,Fe2+)(UO2)2(PO4)2·4H2O. The strongest lines in the X-ray powder diffraction pattern are: 3.473(100)(114), 4.95(50)(110), 4.91(40)(004), 4.443(40)(112), 2.200(30)(118), 2.193(30)(303) and 2.178(30)(009). The mineral is light-yellow in colour and is dull fluorescent. The measured density is 3.242 g/cm3 and Z = 2. There is a prominent (001) cleavage. Refractive indices are : α = 1.572(2) β = 1.577(2) γ = 1.581(2) and 2V = 48°(2). The pleochroism is very weak and the elongation is positive parallel to Y. The mineral occurs as subparallel crystal aggregates with a quadratic outline.
Supra-subduction zone ophiolites of Central Anatolia: geochemical evidence from the Sarikaraman Ophiolite, Aksaray, Turkey
Authors: Yaliniz M. K. , Floyd P. A. , Göncüoğlu M. C. 
Published: December 2006

AbstractThe Central Anatolian Crystalline Complex (CACC), situated between the northern and southern oceanic strands of Neotethys, contain a number of little-studied ophiolitic bodies of late Cretaceous age that have a bearing on the Mesozoic development of this region. The pillow lavas and sheeted dykes of the Sarikaraman Ophiolite were originally a comagmatic differentiated series of vesicular, aphyric and olivine-poor, plagioclase—clinopyroxene phyric tholeiites, but now exhibit greenschist facies assemblages. A set of late dolerite dykes cross-cutting the whole volcanic sequence are more chemically evolved and were probably derived from a different source. Relative to N-MORB the lavas and dykes are enriched in some LIL elements (K, Rb, Cs, U, Th and Sr) and depleted in HFS elements (Nb, Ta, Hf, Zr, Ti and Y) and light REE. In terms of immobile elements the ophiolitic basalts have the broad chemical characteristics of island are tholeiites that were formed in a supra-subduction zone setting, whereas the late dykes are more akin to N-MORB. In this respect the Sarikaraman Ophiolite is similar to other ophiolites found in the eastern Mediterranean region and emphasizes the preservation of this particular environment in the CACC. If all the Central Anatolian Ophiolites (of which the Sarikaraman Ophiolite is one example) were derived via southward thrusting from the Vardar-Izmir-Ankara-Erzincan Ocean branch to the north, age relationships suggest that this segment of ocean crust was relatively short-lived before obduction onto the CACC.
Pyrochlore from Weathered Carbonatite at Lueshe, Zaire
Authors: Wall F. , Williams C. T. , Woolley A. R. , Nasraoui M. 
Published: December 2006

AbstractA detailed study of weathered pyrochlore in the laterite above carbonatite at Lueshe, NE Zaire, has been made in order to determine its chemical and textural variations. Pyrochlore in fresh carbonatite at Lueshe is close to an ideal formula of (Ca,Na)2Nb2O6(OH,F) (where a general formula is A2−xB2O6(OH,F)1−y·zH2O. The first and principal change on weathering occurs at the base of the profile and involves the leaching and partial exchange of A cations together with hydration. This change appears common to weathered pyrochlore worldwide. As a result weathered pyrochlore at Lueshe has a large apparent A cation deficiency with A totals between 0.25 and 0.59. The B cations remain stable. Abundant kalipyrochlore is unique to Lueshe and is thought to be related to the abundance of potassium feldspar in the fresh carbonatite, showing that the actual composition of weathered pyrochlore is a characteristic of a particular deposit. Weathered profiles at Lueshe are not simple trends from the least to most leached compositions. Further factors including variation in whole rock mineralogy and chemistry, and cation exchange and uptake are responsible for local concentrations of strontio-, bario- and calcium-rich, sodium-poor pyrochlore in the ore body, as well as rims of ceriopyrochlore on kalipyrochlore. The most important textural relationship in the Lueshe pyrochlore is the intimate intergrowth with crandallite in the most weathered parts of the laterite. Although pyrochlore persists throughout the weathering profile, niobium-beating goethite is thought to represent the final product of pyrochlore breakdown.