Fe–Mg Interdiffusion in (Mg,Fe)O

We have performed a series of interdiffusion experiments on magnesiowüstite samples at room pressure, temperatures from 1,320° to 1,400°C, and oxygen fugacities from 10^?1.0 Pa to 10^?4.3 Pa, using mixed CO/CO₂ or H₂/CO₂ gases. The interdiffusion couples were composed of a single-crystal of MgO lightly pressed against a single-crystal of (Mg_1-x Fe _x )_1-δO with 0.07<x<0.27. The interdiffusion coefficient was calculated using the Boltzmann–Matano analysis as a function of iron content, oxygen fugacity, temperature, and water fugacity. For the entire range of conditions tested and for compositions with 0.01<x<0.27, the interdiffusion coefficient varies as $$\tilde D\, =\,2.9\times10^{ - 6}\,f_{{\text{O}}_2 }^{0.19}\,x^{0.73}\,{\text{e}}^{ - (209,000\, -\,96,000\,x)/RT}\,\,{\text{m}}^{\text{2}} {\text{s}}^{ -1} $$ These dependencies on oxygen fugacity and composition are reasonably consistent with interdiffusion mediated by unassociated cation vacancies. For the limited range of water activity that could be investigated using mixed gases at room pressure, no effect of water on interdiffusion could be observed. The dependence of the interdiffusion coefficient on iron content decreased with increasing iron concentration at constant oxygen fugacity and temperature. There is a close agreement between our activation energy for interdiffusion extrapolated to zero iron content (x=0) and that of previous researchers who used electrical conductivity experiments to determine vacancy diffusivities in lightly doped MgO.     

Water soluble components of PM_(10) in Chongqing, China

1Introduction Particleswithanaerodynamicdiameterof< 10μmarerecognizedasinhalabaleparticlesandhave beenfoundtobewidelyassociatedwithhealthprob lems(Chapmanetal.,1997).Theywouldalsoinflu enceclimateandvisibilitythroughanumberofimpor tantatmosphericprocesses(Horvath,1993). Rapiddevelopmentofurbanconstructionandrap idgrowthofpopulationhaveexacerbatedChongqing’s pollution.Althoughsulfurdioxidehasbeenreducedby morethan60%incontrasttothevaluein1991,the concentrationsofparticulatematterarestil…     

Rare earth elements (REE)—Minerals in the Silius fluorite vein system (Sardinia,Italy)

The Silius vein system, located in SE Sardinia (Italy) is analogous to other late- to post-Hercynian mineral systems of this type in Europe. The Silius system consists of two main veins, characterized by several generations of fluorite, calcite and quartz, with initial ribbon-like geometries, followed by breccias and cockade-like textures. In this study, aimed at investigating the REE concentrations in the Silius vein system, a REE average of ~ 800 ppm (locally ΣREE > 1500 ppm) has been observed in the carbonate gangue of the fluorite orebody. These amounts are related to the presence of the REE-bearing minerals synchysite-(Ce) and xenotime-(Y). The chemical composition of synchysite-(Ce) has been obtained by wavelength dispersive spectrometry (WDS). The average synchysite-(Ce) formula, built on the basis of (CO₃)₂F and 5 negative charges, is Ca_1.07(La_0.19,Ce_0.36,Pr_0.04,Nd_0.15,Sm_0.03,Gd_0.03,Y_0.13)(CO₃)₂F. From their geochemical characteristics, and their textural relationships with other gangue phases, it is likely that synchysite-(Ce) and xenotime-(Y) formed at the same P-T-X conditions as the other minerals of the Silius fluorite mineralization. Synchysite-(Ce) and xenotime-(Y) at Silius could be related to a local circulation phenomenon, where the REE are derived from a REE-bearing source rock in the basement of southeastern Sardinia, which has been leached by the same fluids precipitating the fluorite/calcite mineralization. REE concentrations contained in the carbonate gangue of still unexploited parts of the Silius vein deposit, as well as in dumps and tailings accumulated during past fluorite processing, could possibly represent a sub-economic by-product of the fluorite exploitation.     

The Al (Nb,Ta) Ti(in−2) substitution in titanite: the emergence of a new species?

Summary The highest (Nb, Ta) content ever encountered in titanite is reported from the Maríkov 11 pegmatite in northern Moravia, Czech Republic. This dike is a member of a pegmatite swarm of the beryl-columbite subtype, metamorphosed under conditions of the amphibolite facies. The pegmatite carries, i.a., rare tantalian rutile intergrown with titanian ixiolite, titanian columbite-tantalite, fersmite and microlite. Fissures generated in the Nb, Ta oxide minerals during deformation are filled with titanite, formed by reaction of the oxide minerals with metamorphic pore fluids. The titanite displays limited degrees of substitutions Na(Ta > Nb)(CaTi)_–1, (Ta > Nb)₄Ti_–4Si_–1 and AI(OH, F)(TiO)_–1, but an extensive (and occasionally the sole significant) substitution (Al > Fe³⁺)(Ta > Nb)Ti_–2, responsible for widespread oscillatory zoning. This substitution reduces the proportion of the titanite componentsensu stricto, CaTiSiO₄,O, to less than 50 mole % in many analyzed spots. The extreme composition corresponds to (Ca_0.994Na_0.011)(Ti_0.436Sn_0.007Al_0.280Fe³⁺ _0.006Ta_0.199Nb_0.079)Si_0.988O₄(O_0.974F_0.026). However, so far this substitution fails to generate compositions that would define a new species.

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Zusammenfassung Die AI(Nb, Ta)Ti_–2 Substitution im Titanit: Auftauchen einer neuen Mineralspecies? Die höchsten (Nb, Ta) Gehalte, die jemals für Titanit gefunden wurden, werden für den Maríkov II Pegmatit in Nordmähren, Tschechei, berichtet. Der Intrusivgang ist Teil eines Amphibolit-faziell überprägten Pegmatitschwarms vom Beryll-Columbit Subtypus Der Pegmatit führt u.a. seltene tantalbetonte Rutile verwachsen mit titanbetontem Ixiolith, titanbetontem Columbit-Tantalit, Fersmit and Mikrolith. Deformationsbedingte Frakturen in den (Nb, Ta) Oxiden sind mit Titanit, als Folge der Reaktion der metamorphen Porenlösungen mit den Oxidmineralen, verkittet. Titanit zeigt begrenzte Substitutionen Na(Ta > Nb)(CaTi)_–1,(Ta > Nb)₄Ti_–4Si_–1 and Al(OH, F)(TiO)_–1, aber extensive (und gelegentlich einzig bedeutsame) Substitution (Al >> Fe³⁺)(Ta > Nb)Ti_–2, die eine weitverbreitete, oszillierende Zonierung hervorruft. Diese Substitution verringert den Anteil der Titanit-Komponentesensu stricto, CaTiSiO,O, auf weniger als 50 Mol% in vielen Analysen. Die Extremzusammensetzung entspricht Ca_0.994Na_0.11) (T_10.436Sn_0.007Al_0.280Fe³⁺ _0.006Ta_0.199Nb_0.079)Si_0.988O₄(O_0.974F_0.026). Das AusmaB dieser Substitution ist unzureichend, um eine neue Mineralspecies zu definieren.

     

Abtragung,Transport und Sedimentation in der östlichen Beltsee (Ostsee)

Ohne ZusammenfassungEine ausführliche Darstellung erscheint in Die Küste, Bd. 3, 1955.     

Dynamic compaction evaluation using in situ tests in Sagunto’s Harbor,Valencia (Spain)

This paper presents an assessment on the use of dynamic compaction as a ground improvement technique in a port’s hydraulic fill in the new southern dock of Sagunto’s Harbor near Valencia (Spain). Soil behavior improvement was monitored by several in situ techniques such as boreholes with SPTs, DPSH, CPTU and CSWS geophysical tests. A total energy between 2188 and 3125 kN/m² (depending the area) was applied to the hydraulic fill by the dynamic compaction procedure. In situ techniques led to evaluate dynamic compaction efficiency, as well as controlling ground modifications that might cause potential damages to adjacent buildings. The dynamic compaction carried out was capable of fulfilling requirements established to use the area, that is, an average deformability modulus (E′) of 30 MPa with a minimum of 20 MPa, in a depth of 10 m. Moreover, dynamic compaction increased hydraulic fill relative density by about 75%.     

Pressure dependence of Néel transition in (Mg,Fe)O

Pressure dependence of Néel temperature (T _N) in (Mg_0.20Fe_0.80)O, (Mg_0.25Fe_0.75)O, and (Mg_0.30Fe_0.70)O was newly measured up to 1.14 GPa, using superconducting quantum interference device magnetometer and piston–cylinder-type pressure cell under hydrostatic condition. The dT _N/dP values of (Mg_0.20Fe_0.80)O, (Mg_0.25Fe_0.75)O, and (Mg_0.30Fe_0.70)O were determined as 4.0 ± 0.3, 2.7 ± 0.3, and 4.4 ± 0.4 K/GPa, respectively, in linear approximation; however, the T _N deviated from the linearity under nonhydrostatic conditions. The compositional dependence of dT _N/dP in (Mg_1?X Fe _X )O showed a rapid decay with increasing Mg components at X ≥ 0.75 and the trend ended at X = 0.70. The estimated Néel transition pressure at room temperature by extrapolating these linearities are very similar to the rhombohedral distortion determined by previous X-ray diffraction studies for X ≥ 0.75, which suggests that the rhombohedral phase of (Mg_1?X Fe _X )O (X ≥ 0.75) at room temperature is antiferromagnetic under hydrostatic conditions.     

Air pollution prediction models of particles,As, Cd,Ni and Pb in a highly industrialized area in Castellón (NE,Spain)

The objective of this study was to elaborate a series of mathematical models with the aim of short-term prediction of TSP, PM10, As, Cd, Ni and Pb in ambient air. These pollutants depend on some known variables (meteorological variables). The reason for choosing this pollutant type is that particulate matter may present a much higher potential risk despite its low representativeness as compared with the gas pollutant group. A positive correlation between high particle concentrations and deterioration in public health has been shown in recent studies. The elements As, Cd, Ni and Pb in PM10 were also analyzed to determine the toxicity of these particles. The goal is to provide a useful instrument to alert the population facing possible episodes of high concentrations of atmospheric pollutants. The study was carried out in a highly industrialized area in the ceramic cluster of Castellón for 5 years (2001–2005). The origin of the contamination in this area is both natural and anthropogenic. The natural origin is due to the resuspension of mineral materials from the surrounding mountains and from the long-range transport of materials from North Africa. The anthropogenic contamination sources that stand out include the non-metallic mineral material industries (ceramic production), chemical industries (color, frit and enamel manufacturing), as well as vehicular traffic. Once the particle samples were collected in quartz fiber filters, the concentration levels of TSP and PM10 were determined gravimetrically. The chemical analysis of the filters was carried out by ICP-MS. Predictive models have been constructed by using multiple regression analysis together with time series models (ARIMA). The SPSS 14.0 statistical software has been employed to analyze the obtained experimental data.     

Crescentiella morronensis (Crescenti) (incertae sedis) dominated microencruster association in Lower Cretaceous (lower Aptian) limestones from the Rarău Massif (Eastern Carpathians,Romania)

Analysis of eight outcrops from Rarău Massif (Eastern Carpathians, Romania) revealed a rich assemblage of encrusting organisms mostly of problematic biological affiliation within platform-margin facies – Crescentiella morronensis, Radiomura cautica, Koskinobullina socialis, Pseudorothpletzella schmidi, Lithocodium aggregatum and bacinellid structures, encrusting calcified sponges (Calcistella jachenhausenensis, Neuropora lusitanica) and foraminifera (Coscinophragma cribrosa). Orbitolinids, calcareous green algae and rudists assign an early Aptian age (Bedoulian) for the studied limestones. In terms of species variety, abundance and structural microfabrics the studied microencruster association show similarity with the Upper Jurassic communities from reef and peri-reefal sedimentary settings. Comparisons with such assemblages are emphasized here. The presence of the sporolithacean and peyssonneliacean red algae (Sporolithon rude and Polystrata alba) contributes also to the construction of superimposed crusts. Even if the known stratigraphic range of the microencrusters is not strictly limited to the late Jurassic, reports of comparable associations in Urgonian-type facies is poorly documented. Therefore, it exemplifies the resistance and flourishing events of many encrusters throughout the Mesozoic.     

Deforestation in the Buea-Limbe and Bertoua regions in southern Cameroon (1984–2000): modernization,world-systems,and neo-Malthusian outlook

This paper characterizes changes in land use and forest cover in southern Cameroon. In doing so, we use remotely sensed data to define the rates and area of forest loss and cover change in two reference areas over a period of 16 years (from 1984 to 2000)—the Buea-Limbe area in the southwest province and the Bertoua area in the east province. We relate socio-economic data of these study areas with results from the empirical spatial analysis to explain causes of deforestation. A second set of explanations, which we call the theoretical perspective, attributes deforestation in southern Cameroon to the intricacies of modernization, world-systems, and neo-Malthusian theories.     

~(40)Ar-~(39)Ar Dating of Quartz from Ore in the Baiyangping Cu-Co Polymetallic Ore-Concentrated Area, Lanping Basin, Yunnan

40Ar-39Ar fast neutron activation age spectrum of quartz in ore collected from the Baiyangping Cu-Co polymetallic ore-concentrated area, Lanping Basin, is saddle-shaped. The plateau age, minimum appearance age and isochron age shown on the spectra are 56.53±0.43 Ma, 55.52±1.78 Ma and 55.90±0.29 Ma respectively. The age data are consistent with each other within 1σ uncertainties. Because the given initial 40Ar/36Ar value of 294.7±1.14 is very close to Nier's value (295.5±5), both plateau and isochron ages may be considered as the forming time of quartz. So the age of 55.90-56.53 Ma represents the forming age of ore deposits. It is obvious that the ore deposits were formed during the Early Himalayan period.     

Paleo water–rock interaction determined through isotopic tracing (Sr,O, C,U) in fracture-fill minerals: Evidence from the Vienne granitoids (France)

Based on the concepts (a) that the stable C and O isotopes combined with the Sr isotope ratios of fracture fills should reflect the source groundwater from which the solid phases precipitated and (b) that U-series disequilibria (USD) enable the calculation of residence time for the U by using Fe oxides as the best candidate, an “isotopic toolbox” was applied to fracture fill from the crystalline basement of the Vienne district. The fracture fills are formed mainly of carbonates, clays and Fe oxides. The isotope data indicate two main generations of carbonate that originated from hydrothermal circulation and equilibrium with present-day groundwaters but the Sr isotope ratios highlight another component with a higher ⁸⁷Sr/⁸⁶Sr ratio reflecting the complexity of the water–rock interactions.For the USD, the Fe-hydroxides located at 207 m depth yield an age of 102 ± 5 ka (St. Germain I interglacial stage), whereas those located at 277 m and 300 m yield respective ages of 173 ± 15 ka and 181 ± 10 ka. These corresponding to the transition between the penultimate glacial period (isotopic stage 6) and the end of the preceding interglacial stage (isotopic sub-stage 7a). Investigating water–rock interaction (⁸⁷Sr/⁸⁶Sr, ¹⁸O, ¹³C, USD) in the fracture-fill minerals from the crystalline basement has shown that such an approach is relevant to developing an understanding of how the groundwater system has changed over time.     

Late Cretaceous (Santonian) Atractosteus (Actinopterygii,Lepisosteidae) remains from Hungary (Iharkút,Bakony Mountains)

Lepisosteid fishes are well known from the Upper Cretaceous of Europe, but only by fragmentary remains from some Cenomanian and Campanian–Maastrichtian deposits. Here we report various cranial and postcranial remains of gars, discovered in the Upper Cretaceous (Santonian) Csehbánya Formation of Iharkút (Bakony Mountains, Hungary). These remains represent one of the most diverse assemblages of lepisosteid fish material from Upper Cretaceous continental deposits of Europe. Based on tooth morphology, scale-microstructure and the features of the supracleithrum we refer these remains to the genus Atractosteus. Besides some uncertain remains from the Cenomanian of France and Spain, the Santonian aged fossils from Iharkút represent the oldest undisputable occurrence of the family Lepisosteidae in the European continental Cretaceous. Using tooth crown morphology, the surface microstructure of the ganoid scales and the anatomy of the supracleithrum a review of the Late Cretaceous lepisosteid record suggests the occurrence of both Atractosteus and Lepisosteus in the European archipelago.     

Tourmalinites and Sn-Li mineralization in the Valdeflores area (Cáceres,Spain)

Summary Tourmalinites containing quartz, Li- and Cs-micas, and small amounts of arsenopyrite occur near Cáceres, Spain. The tourmalinites are developed within Ordovician pelites near the eastern margin of the Cabeza de Araya batholith and close to several small bodies of tectonized granite. Field and textural relationships document an epigenetic character for the tourmalinites. The tourmaline is fine to very fine-grained and its composition is intermediate within the schorl-dravite solid-solution series. Hydrothermal veins containing quartz, muscovite, amblygonite-montebrasite, apatite, fluorite, and/or cassiterite appear spatially related to the tourmalinites. The mineralized area is located in a shear zone that was active during D₃ Hercynian deformation and the emplacement of granitic bodies. Tourmalinites and veins derived from B- and Li-rich magmatic-hydrothermal fluids are believed to have been associated with the intrusion of a hidden granite dome, the tourmalinites being produced by extensive metasomatism of Ordovician metasedimentary rocks.

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Turmalinite and Sn-Li-Vererzungen im Valdeflores Gebiet (Cáceres, Spanien)

Zusammenfassung Turmalinite, die Quarz, Li- und Cs-Glimmer, sowie geringe Mengen an Arsenkies führen, kommen in der Ne von Cáceres, Spanien, vor. Sie sind an ordovizische Metapelite in der Nähe des Cabeza de Araya Batholiths und kleinere tektonisierte Granitkörper gebunden. Eine epigenetische Genese der Turmalinite ist auf Grund von Feldbeziehungen und texturellen Beobachtungen belegt. Die Zusammensetzung der sehr feinkörnigen Turmaline entspricht intermediären Gliedern der Schörl-Dravit- Reihe. Hydrothermale Gänge mit Quarz, Muskowit, Amblygonit-Montebrasit, Apatit, Fluorit und/oder Zinnstein treten benachbart zu den Turmaliniten auf. Der mineralisierte Bereich ist an eine Scherzone gebunden, die während der hercynischen D3 Deformation und der Platznahme der Granite aktiv war. Turmalinite und Gänge lassen sich genetisch von magmatisch-hydrothermalen Fluiden ableiten, die mit der Intrusion eines nicht aufgeschlossenen Granitdomes zusammenhängen. Die Turmalinite sind das Produkt einer weiträumigen Metasomatose der ordovizischen Metasedimente.

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With 8 Figures     

Identification of Composite Rock Body in Dongguashan Copper (Gold) Deposit, Anhui Province

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Typical Geological Features of Rich Zn-Pb-(Ge-Ag) Deposits in Northeastern Yunnan, China

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