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941.
Geraldo Magela da Costa Gabriel de Oliveira Polli Márcio A. Kahwage Eddy de Grave Antônio Claret Soares Sabioni Júlio Cesar Mendes 《Physics and Chemistry of Minerals》2006,33(3):161-166
Mössbauer spectra (MS) of blue, green and yellow beryl (ideally Be3Al2Si6O18) containing approximately 1% of iron were obtained at 295 and 500 K. Room temperature (RT) spectra of both blue and green samples showed the presence of an asymmetric Fe2+ doublet (ΔE
Q~2.7 mm/s, δ~1.1 mm/s), with a very broad low-velocity peak. There is no clear evidence for the presence of a ferric component. The MS of the yellow sample at RT consists of an intense central absorption with parameters typical for Fe3+ (ΔE
Q~0.4 mm/s, δ~0.29 mm/s), plus an apparently symmetrical Fe2+ doublet. This sample acquires a light-blue shade upon heating in air at about 620 K. Thermal treatments at high temperatures caused no significant changes in the MS, but the green and yellow beryl acquire a blue colour. All these results are interpreted in relation to the existence of channel water and the distribution of iron among the available crystallographic sites. 相似文献
942.
The data obtained on melt and fluid inclusions in minerals of granites, metasomatic rocks, and veins with tin ore mineralization
at the Industrial’noe deposit in the southern part of the Omsukchan trough, northeastern Russia, indicate that the melt from
which the quartz of the granites crystallized contained globules of salt melts. Silicate melt inclusions were used to determine
the principal parameters of the magmatic melts that formed the granites, which had temperatures at 760–1020°C, were under
pressures of 0.3–3.6 kbar, and had densities of 2.11–2.60 g/cm3 and water concentrations of 1.7–7.0 wt %. The results obtained on the fluid inclusions testify that the parameters of the
mineral-forming fluids broadly varied and corresponded to temperatures at 920–275°C, pressures 0.1–3.1 kbar, densities of
0.70–1.90 g/cm3, and salinities of 4.0–75.0 wt % equiv. NaCl. Electron microprobe analyses of the glasses of twelve homogenized inclusions
show concentrations of major components typical of an acid magmatic melt (wt %, average): 73.2% SiO2, 15.3% Al2O3, 1.3% FeO, 0.6% CaO, 3.1% Na2O, and 4.5% K2O at elevated concentrations of Cl (up to 0.51 wt %, average 0.31 wt %). The concentrations and distribution of some elements
(Cl, K, Ca, Mn, Fe, Cu, Zn, Pb, As, Br, Rb, Sr, and Sn) in polyphase salt globules in quartz from both the granites and a
mineralized miarolitic cavity in granite were assayed by micro-PIXE (proton-induced X-ray emission). Analyses of eight salt
globules in quartz from the granites point to high concentrations (average, wt %) of Cl (27.5), Fe (9.7), Cu (7.2), Mn (1.1),
Zn (0.66), Pb (0.37) and (average, ppm) As (2020), Rb (1850), Sr (1090), and Br (990). The salt globules in the miarolitic
quartz are rich in (average of 29 globules, wt %) Cl (25.0), Fe (5.4), Mn (1.0), Zn (0.50), Pb (0.24) and (ppm) Rb (810),
Sn (540), and Br (470). The synthesis of all data obtained on melt and fluid inclusions in minerals from the Industrial’noe
deposit suggest that the genesis of the tin ore mineralization was related to the crystallization of acid magmatic melts.
Original Russian Text@ V.B. Naumov, V.S. Kamenetsky, 2006, published in Geokhimiya, 2006, No. 12, pp. 1279–1289. 相似文献
943.
944.
I. N. Tomson O. P. Polyakova V. Yu. Alekseev V. A. Baskina 《Geology of Ore Deposits》2006,48(1):74-76
Two types of metalliferous carbonaceous rocks that differ in associated metals are considered. One of them is characterized by gold occurring in finely dispersed arsenopyrite and arsenic-bearing pyrite, and the other, by finely impregnated native metals in carbonaceous matter. Rocks of the first type also contain elements of the platinum group, while those of the second type bear rhenium, silver, iron, molybdenum, and other metals. Graphitic mineralization is usually localized in the shear zone associated with alkaline basalts. 相似文献
945.
946.
Yu. V. Plotkina E. B. Sal’nikova A. B. Kotov M. D. Tolkachev M. R. Pavlov 《Petrology》2006,14(2):201-208
The paper reports results obtained by the complex studying of zircon crystals from rocks of various genesis. Zircon is one of the minerals most often used as geochronometers. It also provides genetic information on superimposed processes that is “recorded” in the external and internal morphology of its crystals. This mineral is thoroughly examined to select its unaltered crystals for U-Pb dating by the single-grain method. Zircon grains are selected with the use of optical and electron microscopy and cathodoluminescence. This publication presents the first results obtained by examining zircon by computer microtomography (μCT) and the results of the studying of the external and internal structure by conventional techniques ([optical microscopy and SEM (SE and CL)]. The paper demonstrates the advantages of the application of the μCT techniques to the selection of targets for U-Pb zircon dating: there is no need for the special preparation of the samples and no material is destructed. However, this technique may be not informative enough if the zircon contains inherited core whose density does not differ from the density of the surrounding mineral. 相似文献
947.
948.
The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation as a dominant external energy supplier to the Earth, (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities generating and consuming atmospheric gases at the interface of lithosphere and atmosphere. The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate. Quantitative comparison of the scope and extent of the forces of nature and anthropogenic influences on the Earth’s climate is especially important at the time of broad-scale public debates on current global warming. The writers show that the human-induced climatic changes are negligible. 相似文献
949.
We present three-dimensional hydrodynamical modeling of mass transfer in the close binary system β Lyr taking into account explicitly radiative cooling and the stellar wind of the accretor. Our computations show that flow forces wind out from the orbital plane, where an accretion disk with a radius of 0.4–0.5 and a height of about 0.15–0.17 (in units of orbital separation) is formed. Gas motions directed upward from the orbital plane are initiated in the region of interaction of the flow from L1 and the accretor wind (x = 0.91, y = ?0.17); i.e., a jetlike structure forms. This structure has the shape of a gas pillar above the orbital plane, where gas moves with the velocity of stellar wind. The number density of the gas in this structure is about 1014 cm?3, and its temperature is 20 000–45 000 K. At heights of about 0.15–0.20 above the orbital plane, in the region between the jetlike structure and the disk, two spiral shocks form. It is possible that the emission lines observed in the spectrum of β Lyr binary originate in this region. 相似文献
950.