Geology of Ore Deposits - The crystal structure of a Ta-free Nb-dominant ixiolite analogue with the empirical formula (Nb1.55Ti1.11 $${\text{Fe}}_{{1.01}}^{{3 + }}{\text{Mn}}_{{0.19}}^{{2 +... 相似文献
Hydrogen bonding in topaz-OH, Al2SiO4(OH)2, was investigated by IR spectroscopic analysis of the temperature dependence of the OH-stretching frequencies. Low-temperature
spectra ranging from −196 to −160°C prove the existence of four non-equivalent H-positions in the crystal structure from the
occurrence of four different OH-bands. With increasing temperature, these bands merge first, above −160°C, into two OH-bands
and then above 400°C into one asymmetric broad band. Shifting of the OH-bands is caused by thermally induced hydrogen order–disorder.
Low temperature fixes the protons in their positions; increasing temperature induces proton movement and allows switching
between the different positions. Autocorrelation analysis of the IR spectra reveals two phase transitions, one at about −155°C
from P1 to Pbn21 characterized as static–dynamic change and the second at about 380°C from Pbn21 to Pbnm caused by disordering of the protons. The increasing symmetry with temperature is due to advanced proton movement and dynamical
averages over the proton distribution densities. 相似文献
The aqueous mobility and potential bioavailability of metals and metalloids in road runoff in a ‘wet–dry’ tropical location
were assessed by analysing metal and metalloid concentrations in particulate, total dissolved and labile dissolved phases
in runoff waters. Road-derived Al, Cu, Pb, Sb and Zn concentrations were substantially elevated in runoff when compared to
receiving creek waters. Median dissolved concentrations in road runoff exceeded those in creek waters by up to an order of
magnitude. Leaching experiments of road sediments confirmed that several metals and metalloids were released in high concentrations
from road sediments. Labile Zn and Cu concentrations measured by diffusion gradients in thin films (DGT) showed that almost
all dissolved Zn and up to half of dissolved Cu in runoff waters and in road sediment leachate were potentially bioavailable.
Comparisons of dissolved metal concentrations in receiving waters affected by road runoff with ecosystem guideline levels,
indicated a risk of reaching toxic levels of Cu and Zn in the receiving waters in the absence of adequate treatment or dilution.
Low dilution rates of road runoff are likely to occur during late ‘dry’ season/early ‘wet’ season storms which have the potential
to produce high metal concentrations derived from long periods of accumulation of road sediment at a time when creek flow
rates are at their annual minimum. 相似文献
The period between 21 June and 8 October, 2007 (Carrington rotations 2058 to 2061), comprising the Ulysses ecliptic plane crossing, was characterized by low solar activity. Excluding the small solar energetic particle events observed during July, the ion increases observed in the inner heliosphere between 100?keV/n and 10?MeV/n were associated with Corotating Interaction Regions (CIRs). In this work, we investigate CIR-related ion increases using multipoint observations from Ulysses, ACE, and the twin STEREO spacecraft. The ballistic backmapping technique has been used to correlate in situ observations of these spacecraft and remote-sensing observations of coronal holes. Although the radial, longitudinal and latitudinal separation of the spacecraft (except Ulysses) are relatively small, we find discrepancies when a detailed comparison of narrow structures like stream interfaces and CIR-associated shocks is performed. Therefore we concentrate on the two CIR events from day 5 to day 10 of August 2007 and from day 25 to day 31 of August 2007, which lend themselves to a more undisturbed comparison. Using the multi-spacecraft measurements we could determine a radial gradient of 230±30% AU?1, which is consistent with previous results by van Hollebeke et al. (J. Geophys. Res.83, 4723, 1978) of ~?350% AU?1 using Helios and Pioneer data.
The extractable organic matter of sediment samples from six sampling sites in Lake Perdana, Kuala Lumpur, was analyzed to characterize the source inputs. The analysis of aliphatic homologous series indicated that terrestrial higher plant waxes can be assigned as the major sources of the identified aliphatic components in the lake sediments. The presence of an unresolved complex mixture of branched and cyclic compounds and a series of hopanes ranging from C27 to C35 reflected the contamination by petroleum residues from urban vehicular emissions brought in by runoff and fallout. The steroids present included stenols and stanols and showed an input of organic matter from higher plants. The detected pentacyclic triterpenoids comprised oleanane, ursane, lupane and friedelane skeletons including unsaturated oxygenated, mono-, di- and triaromatic counterparts. They are recognized as biomarkers for angiosperms. The presence of des-A-triterpenoids and their aromatized derivatives as the major diagenetic products of triterpenoids reflected the degradation of natural organic matter in the sediments occurring under mainly anoxic conditions. In addition, the presence of tetrahymanol and ββ-bishomohopan-32-ol indicated a minor algal/plankton and bacterial input to the sediments. 相似文献
We determined experimentally the Nernst distribution coefficient between orthopyroxene and anhydrous silicate melt for trace elements i in the system Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) along the dry model lherzolite solidus from 1.1 GPa/1,230°C up to 3.2 GPa/1,535°C in a piston cylinder apparatus.
Major and trace element composition of melt and orthopyroxene were determined with a combination of electron microprobe and
ion probe analyses. We provide partitioning data for trace elements Li, Be, B, K, Sc, Ti, V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb,
Cs, Ba, La, Ce, Sm, Nd, Yb, Lu, Hf, Ta, Pb, U, and Th. The melts were chosen to be boninitic at 1.1 and 2.0 GPa, picritic
at 2.3 GPa and komatiitic at 2.7 and 3.2 GPa. Orthopyroxene is Tschermakitic with 8 mol% Mg-Tschermaks MgAl[AlSiO6] at 1.1 GPa while at higher pressure it has 18–20 mol%. The rare earth elements show a continuous, significant increase in
compatibility with decreasing ionic radius from DLaopx−melt ∼ 0.0008 to DLuopx−melt ∼ 0.15. For the high-field-strength elements compatibility increases from DThopx−melt ∼ 0.001 through DNbopx−melt ∼ 0.0015, DUopx−melt ∼ 0.002, DTaopx−melt ∼ 0.005, DZropx−melt ∼ 0.02 and DHfopx−melt ∼ 0.04 to DTiopx−melt ∼ 0.14. From mathematical and graphical fits we determined best-fit values for D0M1, D0M2, r0M1, r0M2, E0M1, and E0M2 for the two different M sites in orthopyroxene according to the lattice strain model and calculated the intracrystalline
distribution between M1 and M2. Our data indicate extreme intracrystalline fractionation for most elements in orthopyroxene;
for the divalent cations DiM2−M1 varies by three orders of magnitude between DCoM2−M1 = 0.00098–0.00919 and DBaM2−M1 = 2.3–28. Trivalent cations Al and Cr almost exclusively substitute on M1 while the other trivalent cations substitute on
M2; DLaM2−M1 reaches extreme values between 6.5 × 107 and 1.4 × 1016. Tetravalent cations Ti, Hf, and Zr almost exclusively substitute on M1 while U and Th exclusively substitute on M2. Our
new comprehensive data set can be used for polybaric-polythermal melting models along the Earth’s mantle solidus.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Foram determinadas as composições químicas e as idades Rb–Sr de mica branca, feldspato potássico e de rochas totais das mineralizações de esmeraldas de Capoeirana e Belmont, de pegmatitos sem esmeraldas e dos gnaisses Borrachudos, Monlevade e Guanhães da região de Nova Era–Itabira–Ferros (Minas Gerais, Brazil). Os gnaisses graníticos Borrachudos, os gnaisses bandados Monlevade, seus respectivos pegmatitos e veios/schlieren pegmatóides, e os gnaisses Guanhães, adquiriram suas texturas e composições mineralógicas atuais há cerca de 1.9 Ga no contexto do evento Transamazônico.As rochas regionais encaixantes típicas das ocorrências de esmeraldas são os gnaisses Monlevade que pertencem a uma sequência metavulcano-sedimentar de tipo greenstone belt. O evento principal de formação de esmeraldas em Belmont e Capoeirana foi uma reação metassomática dos pegmatitos anatéticos ricos em Be com rochas ultrabásicas ricas em Cr durante o evento Transamazônico em torno de 1.9 Ga. Em Capoeirana nesse contexto os pegmatitos com feldspato potássico ricos em Be foram transformados em rochas de plagioclasio–quartzo. As idades Rb–Sr de cerca de 480 Ma de minerais das mineralizações de esmeralda resultaram da reequilibração de biotitas e feldspatos Transamazônicos durante o evento Brasiliano.Os pegmatitos não-metamórficos e sem esmeralda da região estudada foram formados no evento Brasiliano há 477±14 Ma. O grau de diferenciação dos pegmatitos, estudado em diagramas indicadores específicos como por exemplo Cs vs. K/Rb de micas brancas e feldspatos potássicos, varia desde pegmatitos cerámicos até muscovita-pegmatitos, à pegmatitos de metais raros e até berilíferos. Alguns dos pegmatitos apresentam marcante diferenciação interna.
Seleniferous minerals of palladium and platinum from ouro preto-bearing mineralisation in Brazil
Alexandre Raphael Cabrala, b, , and Bernd Lehmanna
aInstitut für Mineralogie und Mineralische Rohstoffe, Technische Universität Clausthal, Adolph-Roemer-Str. 2A, D-38678 Clausthal-Zellerfeld, GermanybDepartment of Geology: Exploration Geology, Rhodes University, PO Box 94, Grahamstown, 6140 South Africa 相似文献
Crucial to most landslide early warning system (EWS) is the precise prediction of rainfall in space and time. Researchers are aware of the importance of the spatial variability of rainfall in landslide studies. Commonly, however, it is neglected by implementing simplified approaches (e.g. representative rain gauges for an entire area). With spatially differentiated rainfall information, real-time comparison with rainfall thresholds or the implementation in process-based approaches might form the basis for improved landslide warnings. This study suggests an automated workflow from the hourly, web-based collection of rain gauge data to the generation of spatially differentiated rainfall predictions based on deterministic and geostatistical methods. With kriging usually being a labour-intensive, manual task, a simplified variogram modelling routine was applied for the automated processing of up-to-date point information data. Validation showed quite satisfactory results, yet it also revealed the drawbacks that are associated with univariate geostatistical interpolation techniques which solely rely on rain gauges (e.g. smoothing of data, difficulties in resolving small-scale, highly intermittent rainfall). In the perspective, the potential use of citizen scientific data is highlighted for the improvement of studies on landslide EWS. 相似文献
Gasoline constituents were detected in unsaturated soil and rock during abandonment of a leaky underground storage tank (UST). The unsaturated sequence beneath the former UST consists of 90 feet of silty till, fractured dolomite, and friable sand-stone. Pore gas probes were installed in each of the unsaturated units, both in the source area and in a background on-site location. Pore gas samples were collected to evaluate the nature, extent, and fate of residual hydrocarbons in the vadose zone. Pore gas from the till and dolomite in the source area was enriched in petroleum hydrocarbons and carbon dioxide, and was depleted in oxygen, relative to pore gas from the background area. During two years of ground water monitoring at the site, methyl tertiary butyl ether was periodically detected in the ground water beneath the source area as pulses of recharge passed through the unsaturated zone, but no other gasoline constituents were detected. Apparently, the most degradable fraction of the gasoline (aromatic hydrocarbons) is being attenuated in the vadose zone before the water table is reached. 相似文献