Glass-ceramic materials, obtained by sinter-crystallization of melted alkaline-olivine basaltic tuffs, were investigated. The kinetics of bulk crystallization was evaluated by differential thermal analysis (DTA) at different heating rates. The phase formation and the sintering behavior of glass powders (<75 lm) were studied in air and in nitrogen atmospheres by DTA and dilatometry, respectively...

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...

Interpretations of faunal assemblages from the late Miocene Mpesida Beds in the Tugen Hills of the Central Kenyan Rift Valley have figured prominently in discussions of faunal turnover and establishment of the modern East African communities. These faunal changes have important implications for the divergence of the human lineage from the African apes ca. 8-5 Ma. While fossil material recovered...

Precise dating of K-rich minerals in volcanic rocks via the 40Ar/39Ar geochronometer has become crucial to resolving many geological problems. In some cases, ash beds containing biotite phenocrysts but lacking sanidine are the only datable horizons at key stratigraphic intervals, necessitating comparison of sanidine and biotite ages within the same chronostratigraphic framework. To assess the i...

New 40Ar/39Ar ages and paleomagnetic data are presented from a wide range of ignimbrites lava flows the region east Atacama Desert in northern Chilean part Central Volcanic Zone Andes. Eight dacitic to rhyolitic ignimbrites, 12 one shallow intrusion were dated by incremental heating method, first reported for these units. Ignimbrites age 4.2 Ma 0.5 Ma, with ~100 km3 Puripicar ignimbrite at 4.18...