Genesis of Peraluminous Granites I. Experimental Investigation of Melt Compositions at 3 and 5 kb and Various H2O Activities   总被引：1，自引：0，他引：1  

HOLTZ  FRAN?OIS; JOHANNES  WILHELM 《Journal of Petrology》1991,32(5):935-958

Melting experiments have been performed on a peraluminous quartzo-feldspathicgneiss from Northern Portugal. This gneiss occurs as xenolithsin the Tourem anatectic complex and is the most probable sourcerock for the surrounding anatectic granites. On the basis offield, petrological, and geochemical data, it can be shown thatanatexis took place in the stability field of cordierite + biotiteand that the evolution of magmas is the result of processesinvolving segregation of partial melt and separation of restiteminerals. Experiments were performed at 700, 750, and 800 ?C, 3 and 5kb, and various H₂O activities (aH₂O) to clarify the influenceof aH₂O and melt fraction on the composition of the generatedmelts. Biotite and cordierite are the two main ferromagnesianphases observed in the run products. Cordierite is formed byincongment melting of biotite. For relatively low melt fractions (< 30–35 wt. %),the partial melts coexisting with quartz, alkali feldspar, andplagioclase have a minimum or near-minimum melt composition.The melts become richer in potassium with decreasing aH₂O. Thisresult using a natural rock as starting material is in goodagreement with results achieved in the synthetic Qz-Ab-Or system.In the stability field of biotite and cordierite, the influenceof aH₂O on melt composition is at least as important as theeffect of changing P and/or T. For higher melt fractions the composition of the melt is stronglycontrolled by the disappearance of alkali feldspar and the meltsbecome richer in An and poorer in Or with increasing degreeof melting. The wide range of compositions (especially for K₂O, which variesfrom 3.5 to 5.4%) observed in the experimental peraluminousmelts demonstrates that a wide variety of granitoid magmas maybe produced from the same source rocks. The application of theexperimental results to the Tourem anatectic complex shows thatmelting occurred at H2O-undersaturated conditions (4–5wt. % H₂O in the melts, corresponding to aH₂O of {small tilde}0.5at 5 kb). Experimental melts similar in composition to the mostleucocratic granite of the Tourem anatectic complex (consideredto approximate the composition of the generated melt) were obtainedaround 800 ?C, suggesting that this temperature was attainedduring the peak of anatexis.  相似文献   

Justifying the WKB approximation in pure katabatic flows   总被引：1，自引：0，他引：1  

BRANKO GRISOGONO  JOHANNES OERLEMANS 《地球，A辑:动力气象学与海洋学》2002,54(5):453-462

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A data chart for field description and genetic interpretation of glacial diamicts and associated sediments…with examples from Greenland, Iceland, and Denmark     

JOHANNES KRüGER  KURT HENRIK KJÆR 《Boreas: An International Journal of Quaternary Research》1999,28(3):386-402

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Baroclinic instability in a two-layer, vertically semi-infinite domain     

JOHANNES C. MÜLLER 《地球，A辑:动力气象学与海洋学》1991,43(5):275-284

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