The effect of dissolved water on the diffusivity of Ar in glasses and melts of rhyolitic and albitic compositions was investigated experimentally at pressures up to 1500 MPa and water contents of 0.1^5 wt%. The data for water-poor rhyolitic composition at 500 MPa can be described in the whole temperature range of 480^11023C by a simple Arrhenius relationship DAr = 2.14U1036 m2/s exp(318 883/T)....

The diffusion of water in a peralkaline and a peraluminous rhyolitic melt was investigated at temperatures of 714–1,493 K and pressures of 100 and 500 MPa. At temperatures below 923 K dehydration experiments were performed on glasses containing about 2 wt% H2Ot in cold seal pressure vessels. At high temperatures diffusion couples of water-poor (\0.5 wt% H2Ot) and water-rich (*2 wt% H2Ot) melts ...

Samples produced in piston cylinder experiments were used to document the thermal isotopic fractionation of all the major elements of basalt except for aluminum and the fractionation of iron isotopes by chemical diffusion between a natural basalt and rhyolite. The thermal isotopic fractionations are summarized in terms of a parameter Xi defined as the fractionation in per mil per 100 C per atom...

Abstract The exposed rocks in Abu Hawis area, North Eastern Desert (NED), Egypt, consist of tonalite-granodiorite and monzogranite, dissected by post-granite felsic (microgranite rhyolite) mafic (basaltic-andesite) dikes. investigated radioactive minerals Zr-, Nb-, REE-bearing were restricted to dikes having E–W NE–SW trends. Uraninite, uranothorite, thorite occur as the main microgranite dikes...

Demingding is a promising porphyry Mo-dominated deposit recently discovered in the eastern Gangdese metallogenic belt Tibet, China. We present zircon U-Pb-Lu-Hf isotopic studies, as well geochemical data of late monzogranites and prior rhyolites from to uncover their origin geodynamic mechanism. Zircon U–Pb dating yielded precise crystallization ages 17.3 ± 0.6 Ma (MSWD = 2.5) 186.5 3.0 2.0) fo...