Viscosity of liquid silica,silicates and alumino-silicates     

G. Urbain  Y. Bottinga  P. Richet 《Geochimica et cosmochimica acta》1982,46(6):1061-1072

Viscosity measurements are reported for amorphous silica and liquids belonging to the systems SiO₂-M, SiO₂-Al₂O₃-M, where M is an alkali-earth metal oxide, MnO, or alumina, and the systems SiO₂-“FeO”, SiO₂-FeO-Fe₂O₃-CaO, and SiO₂-Al₂O₃-N, where N = Na₂O or K₂O. The implications of these measurements concerning the coordination of Al and the structure of these liquids are briefly discussed. Stable liquids in the systems SiO₂-Al₂O₂-M show a non-Arrhenian temperature dependence of their viscosity, in general. Results obtained with empirical methods to calculate the viscosity of silicate liquids are compared with our observations.  相似文献   

Derivation of detrital rutile in the Yaoundé region from the Neoproterozoic Pan-African belt in southern Cameroon (Central Africa)     

Henrik Stendal  Sadrack Flix Toteu  Robert Frei  Joseph Penaye  Urbain Olivier Njel  Jean Bassahak  Jean Nni  Boniface Kankeu  Vincent Ngako  Joseph Victor Hell 《Journal of African Earth Sciences》2006,44(4-5):443

Rutile, as an important component in alluvial or eluvial heavy mineral deposits, is known in southern Cameroon. These deposits are underlain by the Neoproterozoic low- to high-grade Yaoundé Group. Geochemical, thermometric, fluid inclusion and Pb isotopic studies of the rutile from alluvial and eluvial concentrates and from medium-grade micaschist from the nearby Yaoundé region permit the following conclusions: (1) alluvial and eluvial rutile of the Yaoundé region are derived from the degradation of metapelites, metamafic rocks and pegmatites of the nearby Yaoundé Group; (2) rutile in the Yaoundé Group formed during the Pan-African metamorphism, or was inherited as detrital rutile from a 900 Ma source. The study also shows that the rutile can be used to trace the history of the Pan-African belt north of the Congo craton.  相似文献   

The Guenie and Gao chondrites from Burkina Faso: Probably a single shower of stones     

Michle BOUROT-DENISE  Urbain WENMENGA  Mireille CHRISTOPHE 《Meteoritics & planetary science》1998,33(Z4):A181-A182

Abstract— Two H4–5 meteorite showers have been reported to have fallen at one month intervals in the Guenie-Gao area, but eyewitness accounts are imprecise. Though subtle mineralogical differences are found between stones with different ²¹Ne content, these differences are insufficient to confirm that two meteorite falls had occurred.  相似文献