Features of mineral and chemical composition of the Khamambettu Carbonatites, Tamil Nadu

The paper presents mineralogical features and EPMA results of the Khamambettu carbonatites. The mineralogical data suggest that these rocks have been generated in magmatic and hydrothermal stages. Mineral geothermometer for carbonatite give temperatures of 790°–980°C. Fluid inclusion measurements in monazite (hydrothermal stage) give temperatures of 220°–290°C. One of the features of the carbonatites is high content of magnesia that is defined by the presence of dolomite, olivine, spinel, phlogopite, Mg-rich ilmenite. Chloritization, serpentinization, amphibolization, silicification processes and occurrence of barite, monazite-(Ce), strontianite, celestine are related to hydrothermal stage. Hydrothermal minerals at the Khamambettu were formed by recrystallization of primary carbonatite minerals in the presence of Ba, (SO₄)^2?, REE and Si carried in solution by the hydrothermal fluid.     

The passage of radiation through a wormhole

We consider a model for the passage of radiation through a “wormhole.” A physical interpretation of a special class of solutions of the Einstein equations with a scalar field is given. A solution describing the passage of an infinitely narrow pulse of radiation is constructed by joining along the null geodesic the two stationary equations describing the wormhole before and after the passage of the radiation. The physical consequences of the passage of the radiation on the structure of the wormhole are analyzed.     

Newania carbonatites, Western India: example of mantle derived magnesium carbonatites

The key mineralogical features of the Newania carbonatites, that illustrate their derivation from primary mantle melts (Gruau et al. Terra Nova, Abstract Suppl 1:336, 1995; Viladkar Petrology 6(3):272–283, 1998; Basu and Murty Abstracts of Goldschmidt Conference A40, 2006), are the presence of magnesite, graphite and Cr-rich magnetite. Magnesite is an early crystallizing phase. Cr-rich magnetite and graphite coexist with carbonatite minerals and precipitated from carbonate magma. Graphite, as well as gaseous CO₂ and carbonate minerals such as dolomite and magnesite, can be stable in peridotite mantle. Coexistence of these minerals is controlled by fO ₂ and PT-conditions. Mineral geothermometers for the Newania carbonatite give temperatures from 463 to 950°C. The parental source for Newania carbonatites was characterized by a relatively high log (fHF/fH₂O) level which increased during the crystallization history of Newania. The estimated oxygen fugacity (for ilmenite–magnetite pairs) varies from ?1.5 to +3.5 (log-bar unit deviation from FMQ buffer), which is supported by the presence of Fe-columbite, and the composition of phlogopite, amphibole and pyroxene that have an elevated concentration of Fe³⁺. However, the oxygen fugacity range represented by co-existing early-crystallized graphite and magnesite is below that of the FMQ buffer and lies on the CCO buffer.     

Prospects for Observations of Gravitationally Lensed Sources by Submillimeter Space Observatories

The prospects for observations of gravitationally lensed extragalactic sources in the far-infrared and submillimeter ranges of the electromagnetic spectrum by the planned space observatories with active cooling of the telescope mirror to cryogenic temperatures are considered. The possibility of solving topical cosmological and astrophysical problems related to the observations of gravitationally lensed sources is discussed. The number counts of lensed sources have been performed for various wavelengths in the range from 70 to 2000 µm. The redshift and magnification distributions of lensed sources and the mass distribution of lenses have been obtained. We have constructed model photometric sky maps for which the contribution from lensed sources has been calculated for the first time.

     

Statistical characteristics of simulated walls

The large-scale matter distribution in three different simulations of CDM models is investigated and compared with corresponding results of the Zel'dovich theory of non-linear gravitational instability. We show that the basic characteristics of wall-like structure elements are well described by this theory, and that they can be expressed by the cosmological parameters and a few spectral moments of the perturbation spectrum. Therefore the characteristics of such elements provide reasonable estimates of these parameters. We show that the compressed matter is relaxed and gravitationally confined and manifests itself in the existence of walls as (quasi-)stationary structure elements with a lifetime restricted by their disruption into high-density clouds.
The matter distribution is investigated in both real and redshift spaces. In both cases almost the same particles form the walls, and we estimate differences in corresponding wall characteristics. The same methods are applied to several mock catalogues of 'galaxies', which allows us to characterize a large-scale bias between the spatial distribution of dark matter and of simulated 'galaxies'.     

Aluminium phosphate and phosphate-sulphate minerals in kyanite schists of the Ichetuyskoye area, West Transbaikalia, Russia: crystal chemistry and evolution

Aluminium phosphate and aluminium phosphate-sulphate (APS) minerals occur as disseminated crystals and fine-grained aggregates in kyanite schists near Ichetuyskoye, in the Dzhida basin (West Transbaikal region, Russia). Petrographical, mineralogical and geochemical data suggest a metamorphic evolution through prograde and retrograde stages. Lazulite-scorzalite and trolleite in association with kyanite, quartz, muscovite, paragonite, topaz, rutile, magnetite and hematite formed during the prograde stage. More than 25 minerals identified in schists are genetically related to the retrograde stage. Some phosphates and all of the APS minerals belong to the alunite, beudantite and plumbogummite groups. Electron-microprobe data reveal the presence of wide compositional variations and complex solid-solution series among the members. The main crystal-chemical variations of the APS solid-solution series in the alunite supergroup concern the relative proportions of svanbergite, woodhouseite, goyazite, crandallite, florencite-(Ce) and natroalunite. Chemical analyses of APS minerals indicate extremely high amounts of LREE, Sr, Ba, Ca and Na. In some cases, APS minerals have compositions of Ba and Ca,Ba phosphates?C sulphates.