Preliminary results from the Russian-American Gallium Experiment Cr-neutrino source measurement

The Russian-American Gallium Experiment has been collecting solar neutrino data since early 1990. The flux measurement of solar neutrinos is well below that expected from solar models. We discuss the initial results of a measurement of experimental efficiencies by exposing the gallium target to neutrinos from an artificial source. The capture rate of neutrinos from this source is very close to that which is expected. The result can be expressed as a ratio of the measured capture rate to the anticipated rate from the source activity. This ratio is 0.93 + 0.15, - 0.17 where the systematic and statistical errors have been combined. To first order the experimental efficiencies are in agreement with those determined during solar neutrino measurements and in previous auxiliary measurements. One must conclude that the discrepancy between the measured solar neutrino flux and that predicted by the solar models can not arise from an experimental artifact

Biotites in granites, biotites in gneisses, and the status of biotite as a one-mineral environment indicator

Some aspects of one-mineral geological environment indicators are discussed. Factors controlling the composition of biotite in different P, T, and chemical environments are reviewed. On the basis of theoretical considerations and empirical observation it is concluded that biotites in igneous granites may tend to be somewhat richer in iron than biotites from gneisses, but the relation is not strict, and the Fe/Mg or FeO/MgO/Al2O3 ratios in biotite do not provide unequivocal indications of the origin of biotite-bearing rocks

Timing of late Palaeoproterozoic metamorphism in the northern Belomorian Belt, White Sea region: Conclusions from U-Pb isotopic data and P-T evidence

Brilliant-looking zircon crystals from a garnet-amphibolitic, metamorphosed mafic dyke at Lyagkomina in the Lake Kovdozero area, northern Belomorian Belt, most probably mark the 1875±4 Ma age of peak late Palaeoproterozoic regional metamorphism which followed upon dyke intrusion associated with deformation of the Lapland-Kola orogenic tectonic collage. U-Pb ages of titanites (ca. 1860 Ma) and rutiles (ca. 1750 Ma) help reconstruct the retrograde path and the cooling rates which decreased with time. The new titanite and rutile ages agree well with similar age data previously obtained on a regional scale from the central part of the belt and suggest absence of variation in mineral ages as a function of lithological differences. P-T analysis of the metamorphic parageneses indicates initial sharp decompression after peak metamorphism and jump uplift with unroofing of ca. 9-10 km of the crust in the Belomorian Belt previously thickened by late Palaeoproterozoic orogenic thrusting and stacking