Hornblende occurs in some andesitic and basaltic rocks of calc-alkaline affini1y, where it is commonly associated with olivine. The texture, eruption history, and composition are interpreted to indicate that hornblende commonly forms as a product of reaction between olivine and basaltic and andesitic liquids. The natural hornblendes probably formed within the crust at temperatures between 960o ...

Mt. Pinatubo is one of several recent-age volcanoes along the west Luzon volcanic arc. A fumarole near the suminit emits gases with magmatic characteristics. Several thermal springs on the east and west flanks yield various fluid typos, including neutral chloride and bicarbonate. Three wellbores probed the Mt. Pinatubo caldera from elevations of +1230 through -1600 mRSL. Trajectories may be des...

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...

Orientation of the eruption fissures and composition of the lavas of the Miyakejima volcano is indicative of the competitive processes of the regional tectonic stress and the local stress generated by the activity of a magma plumbing system beneath the volcano. We examined the distributions and magmatic compositions of 23 fissures that formed within the last 2800 years, based on a field survey ...

Introduction: Deconvolution of thermal emission spectra from Mars orbiting spacecraft, in-situ analysis of martian rocks by Mars Pathfinder, Spirit and Opportunity rovers, as well as investigation of martian meteorites, all point towards a wide magmatic diversity at the surface of the planet. Compositions varying from olivine-rich basalt to high-silica granite / rhyolite through basaltic andesi...

This work presents the volcanic geology of easternmost sector Trans-Mexican Volcanic Belt, including Serdán-Oriental basin and Cofre de Perote-Citlaltépetl range, two contrasting Quaternary fields. The first comprises dominant monogenetic volcanism bimodal composition isolated rhyolitic domes tuff rings, basaltic andesite maar volcanoes, cinder lava cones, an active caldera complex (Los Humeros...

Volcán San Pedro in the Andean Southern Volcanic Zone (SVZ) Consequently, the role of young, unradiogenic hydrous gabbro in Chile, comprises Holocene basaltic to dacitic lavas with trace generating dacite and contaminating basalt may be underappreciated element and strontium isotope ratios more variable than those of in the SVZ. most Pleistocene lavas of the underlying Tatara–San Pedro complex....

Multiple volcanic eruptions occurred between 8500 and 9000 yr. B.P. from the central crater of CitiaitCpetl Volcano generating a series of pyroclastic flows that formed a deposit with a total volume of about 0.26 km3 (D.R.E.). The flows descended in all directions around the crater, but they were mostly controlled by topography and deposited in valleys or local topographic depressions up to abo...