Coexisting melt (MI), fluid-melt (FMI) and fluid (FI) inclusions in quartz from the Oktaybrskaya pegmatite, central Transbaikalia, have been studied and the thermodynamic modeling of PVTX-properties of aqueous orthoboric-acid fluids has been carried out to define the conditions of pocket formation. At room temperature, FMI in early pocket quartz and in quartz from the coarse-grained quartz–oligoclase host pegmatite contain crystalline aggregates and an orthoboric-acid fluid. The portion of FMI in inclusion assemblages decreases and the volume of fluid in inclusions increases from the early to the late growth zones in the pocket quartz. No FMI have been found in the late growth zones. Significant variations of solid/fluid ratios in the neighboring FMI result from heterogeneous entrapment of coexisting melts and fluids by a host mineral. Raman spectroscopy, SEM EDS and EMPA indicate that the crystalline aggregates in FMI are dominated by mica minerals of the boron-rich muscovite–nanpingite CsAl2[AlSi3O10](OH,F)2 series as well as lepidolite. Topaz, quartz, potassium feldspar and several unidentified minerals occur in much lower amounts. Fluid isolations in FMI and FI have similar total salinity (4–8 wt.% NaCl eq.) and H3BO3 contents (12–16 wt.%). The melt inclusions in host-pegmatite quartz homogenize at 570–600 °C. The silicate crystalline aggregates in large inclusions in pocket quartz completely melt at 615 °C. However, even after those inclusions were significantly overheated at 650±10 °C and 2.5 kbar during 24 h they remained non-homogeneous and displayed two types: (i) glass+unmelted crystals and (ii) fluid+glass. The FMI glasses contain 1.94–2.73 wt.% F, 2.51 wt.% B2O3, 3.64–5.20 wt.% Cs2O, 0.54 wt.% Li2O, 0.57 wt.% Ta2O5, 0.10 wt.% Nb2O5, 0.12 wt.% BeO. The H2O content of the glass could exceed 12 wt.%. Such compositions suggest that the residual melts of the latest magmatic stage were strongly enriched in H2O, B, F, Cs and contained elevated concentrations of Li, Be, Ta, and Nb. FMI microthermometry showed that those melts could have crystallized at 615–550 °C.
Crystallization of quartz–feldspar pegmatite matrix leads to the formation of H2O-, B- and F-enriched residual melts and associated fluids (prototypes of pockets). Fluids of different compositions and residual melts of different liquidus–solidus P–T-conditions would form pockets with various internal fluid pressures. During crystallization, those melts release more aqueous fluids resulting in a further increase of the fluid pressure in pockets. A significant overpressure and a possible pressure gradient between the neighboring pockets would induce fracturing of pockets and “fluid explosions”. The fracturing commonly results in the crushing of pocket walls, formation of new fractures connecting adjacent pockets, heterogenization and mixing of pocket fluids. Such newly formed fluids would interact with a primary pegmatite matrix along the fractures and cause autometasomatic alteration, recrystallization, leaching and formation of “primary–secondary” pockets. 相似文献
We examine a model for the expected contributions to the soft X-ray background (SXRB) due to bremsstrahlung and re-combination radiation of gas, enriched with heavy elements, located in groups of galaxies taken from Tully'sCatalog of Nearby Groups of Galaxies.
It is shown that the contribution to the SXRB of groups of galaxies can explain up to 20% of the observed flux depending on the chemical composition and ratio of emitting mass to assumed virial mass. 相似文献
The influence of deep crustal processes on basin formation and evolution and its relation to current morphology is not well
understood yet. A key feature to unravel these issues is a detailed seismic image of the crust. A part of the data recorded
by the hydrocarbon industry in the late 1970s and 1980s in the North German Basin were released to the public recently. The
seismic reflection data were recorded down to 15 s two-way travel time. The mean Common Midpoint fold of about 20 is relatively
low compared to contemporary seismic acquisitions. The processing of the 1980s focussed on the sedimentary structures to explore
the hydrocarbon potential of this area. We applied the Common Reflection Surface stack technique to the data sets, which is
well suited for low-fold data. The reprocessing was focussed on the imaging of the subsedimentary crustal range. The reprocessed
images show enhanced reflections, especially in the mid and lower crustal part. Also, the image of the salt structures in
the graben area was improved. Furthermore, the reprocessed images indicate an almost flat Moho topography in the area of the
Glückstadt Graben and an additional lower crustal structure, which can be correlated with a high-density body found in recent
gravity modeling studies. 相似文献
Clay-rich mine tailings from phosphate mine operations in Florida are a major environmental and economic problem. Options
for reclamation and restoration for these tailings are very limited and are fundamentally restricted by poor physical properties
such as low mechanical strength, low hydraulic conductivity, and heavy metal content. The major control on these bulk physical
properties is the mineralogy of the materials. Eight continuous push borings were obtained to investigate stratigraphy, mineralogy,
aspects of geochemistry, and bulk properties of a deposit of clay-rich mine tailings from a phosphate mine near Bartow, Florida
that ceased operations in the early 1970s. Stratigraphy is dominated by laminated clay-rich sediment with minor units of silt
and sand. An intact kaolinite liner occurs near the impoundment walls and the impoundment floor has approximately 4 m of relief.
Moisture content varies from 4.35 to 57.40 wt% and organic content varies from 0.41 to 9.53 wt%. Bulk XRF investigation indicates
that the P2O5 concentrations vary from approximately 4 to 21 wt%. A very strong correlation (r2 = 0.92) between CaO and P2O5 indicates that apatite is a major control on the phosphate. The strong correlation (r2 = 0.77) of Al2O3 and TiO2 suggests that the source materials for this deposit are comparatively uniform. A number of heavy metal elements and trace
elements occur. Cr, V, Ni, Cu are interpreted to be in phosphate minerals, largely apatite. Sr and Pb are interpreted to be
in both phyllosilicates and phosphate minerals. Two populations of apatite were observed in the clay-sized fraction, one that
was Fe and Si- bearing and another that was only Si-bearing. Fe-bearing apatite had Fe2O3 contents that varied from 0.38 to 5.32 wt% and SiO2 contents that varied from 0.90 to 3.32 wt%. The other apatite population had a wider range of SiO2 contents that varied from 0.77 to 8.80 wt%. TEM imaging shows that apatite grains are dominantly single crystals with lesser
amounts of aggregates. Wavellite commonly occurs as individual or clusters of lath-like crystals and the chemical composition
differs from the pure aluminium phosphate end member with average concentrations of components being that of CaO (1.57 wt%),
Fe2O3 (1.98 wt%), SiO2 (5.94 wt%). In the clay-sized phosphate minerals investigated no fluorine was found above detection limit (approximately
0.15 wt%), nor was any uranium, radium, heavy metal, or REE element detected. The phyllosilicate mineralogy of the deposit
is dominated by smectite (montmorillonite with lesser amounts of nontronite), palygorskite, illite and kaolinite. No systematic
variation in the relative proportions of phyllosilicates was observed in the clay deposit. Energy dispersive spectroscopy
EDS analysis indicates that chemical compositions of phyllosilicates are somewhat typical but overall are enriched with respect
to Fe compared to theoretical end members. The relative enrichment of Fe is interpreted to be a primary sedimentary feature.
Ca content in smectite minerals is high and may inhibit stabilization using lime or similar methods. The high percentages
of montmorillonite and palygorskite explain the high bulk water contents observed. This investigation provides fundamentally
new details regarding clay tailing deposits from closed phosphate mines in central Florida which can be used in restoration
and reclamation efforts. 相似文献
Fluxes of dissolved forms of iron and manganese across the sediment–water interface were studied in situ in the Gulf of Finland and the Vistula Lagoon (Baltic Sea), and in the Golubaya Bay (Black Sea) from 2001 to 2005. Fluxes were measured using chamber incubations, and sediment cores were collected and sliced to assess the porewater and solid phase metal distribution at different depths. Measured and calculated benthic fluxes of manganese and iron were directed out of sediment for all sites and were found to vary between 70–4450 and 5–1000 µmole m− 2 day− 1 for manganese and iron, respectively. The behavior of the studied metals at various redox conditions in the near-bottom water and in the sediment was the main focus in this study. Our results show the importance of bottom water redox conditions for iron fluxes. We measured no fluxes at oxic conditions, intermediate fluxes at anoxic conditions (up to 200 μmole m− 2 day− 1) and high fluxes at suboxic conditions (up to 1000 μmole m− 2 day− 1). Total dissolved iron fluxes were generally dominated by iron(II). Contribution of iron(III) to the total iron flux did not exceed 20%. Obtained fluxes of manganese at all studied regions showed a linear correlation (r2 = 0.97) to its concentration in the porewater of the top sediment layer (0–5 mm) and did not depend on dissolved oxygen concentrations of bottom water. Organically complexed iron and manganese were in most cases not involved in the benthic exchange processes. 相似文献
The World Space Observatory UltraViolet (WSO–UV) is an international space mission devoted to UV spectroscopy and imaging. The observatory includes a 170 cm aperture telescope capable of high-resolution and long slit low-resolution spectroscopy, and deep UV and optical imaging. The observatory is designed for observations in the ultraviolet domain where most of astrophysical processes can be efficiently studied with unprecedented capability. 相似文献
The dwarf planet Ceres has a density of 2040-2250 kg m−3, and a dark non-icy surface with signs of hydrated minerals. As opposed to a differentiated internal structure with a nonporous rocky core and a water mantle, there are arguments for undifferentiated porous interior structure. Ceres’ mass and dimensions are uncertain and do not exclude undifferentiated interior even if hydrostatic equilibrium is attained. The rocky surface may be inconsistent with a large-scale water-rock differentiation. A differentiated structure with a thick water mantle below a rocky crust is gravitationally unstable and an overturn would have led to abundant surface salt deposits, which are not observed. A formation of hydrated surface minerals caused by internal heating implies a major density increase through devolatilization of the interior. A later accumulation of hydrated materials is inconsistent with anhydrous surfaces of many asteroids and with a low rate of the cosmic dust deposition in the inner Solar System. Ceres’ internal pressures (<140-200 MPa) are insufficient to significantly reduce porosity of chondritic materials and there is no need for abundant water phases to be present to account for the bulk density. Having the porosity of ordinary chondrites (∼10%), Ceres can consist of rocks with the grain density of pervasively hydrated CI carbonaceous chondrites. However, additional low-density phases (e.g., water ice) require to be present in the body with the grain density of CM chondrites. The likely low-density mineralogy of the interior implies Ceres’ accretion from pervasively aqueously altered carbonaceous planetesimals depleted in short-lived radionuclide 26Al. Abundant water ice may not have accreted. Limited heat sources after accretion may not have caused major mineral dehydration leading to formation of water mantle. These inferences can be tested with the Dawn spacecraft in 2015. 相似文献