Major element compositions of glass inclusions in olivine and plagioclase phenocrysts from representative Mariana arc lavas show that mafic Mariana arc liquids are tholeiitic and not high-alumina, implying that the high-alumina characteristic of these lavas reflects accumulation of plagioclase. Glass inclusions also show the common occurrence of felsic melts previously unrecognized among Marian...

The diffusion of water in dacitic and andesitic melts was investigated at temperatures of 1458 to 1858 K and pressures between 0.5 and 1.5 GPa using the diffusion couple technique. Pairs of nominally dry glasses and hydrous glasses containing between 1.5 and 6.3 wt.% dissolved H2O were heated for 60 to 480 s in a piston cylinder apparatus. Concentration profiles of hydrous species (OH groups an...

The youngest volcanism of the Ecuadorian Volcanic Front (Western Cordillera) is mainly dominated by highly explosive events, including growth and violent destruction lava domes, formation thick pyroclastic sequences. Deposits associated with such eruptive dynamics have been identified at Iliniza, a compound volcano located in Western Cordillera poorly defined evolutionary history. We present fi...

The subaerial surface of Koolau volcano is composed of lavas that define the distinctive endmember composition for Hawaiian shield lavas, known as the Koolau component, now designated as the Makapuustage. The geochemical characteristics of lavas recovered by the Koolau Scientific Drilling Project (KSDP) show that this distinctive composition forms a <300-m thick veneer. Below this veneer, from ...

The geochemical composition of surface soils and potential bedrocks in Davarzan area has been investigated to determine soil origin and evaluate environmental aspects. Davarzan plain is composed of soils and deposits derived by weathering and transportation of different bedrocks from northern mountains. The bedrocks consist of Eocene (andesitic to basaltic lavas and volcano-sedimentary rocks co...

marine sequences within several orogenic belts in YunWe report petrological and geochemical data on ultramafic pillow nan, SW China (Figs 1 and 2; Fang et al., 1996). These lavas from Late Palaeozoic marine sequences in Yunnan, SW lavas have been interpreted to be oceanic plateaux or China. These lavas have >26 wt % MgO, euhedral to subhedral seamount eruptive rocks associated with mantle plume...

Oxygen isotope ratios of olivine in 23 tholeiites from the Hawaii Scientific Drilling Project (HSDP) core (15 from Mauna Kea, 8 from Mauna Loa) and three samples of outcropping subaerial or dredged submarine Mauna Kea lavas have been measured by laser fluorination. The ~18o values are 4.6-5.4 %o, confirming previous observations that some Hawaiian lavas are derived from sources with ~18o values...

V/Sc systematics in peridotites, mid-ocean ridge basalts and arc basalts are investigated to constrain the variation of fO2 in the asthenospheric mantle. V/Sc ratios are used here to ‘ see through’ those processes that can modify barometric fO2 determinations in mantle rocks and/or magmas: early fractional crystallization, degassing, crustal assimilation and mantle metasomatism. Melting models ...