Mesozoic strata in the Cowhole Mountains, eastern Mojave block California, include 200–800 m of eolian quartz arenite (Aztec Sandstone) overlain by more than 575 m of silicic ignimbrites, lava flows, and minor sedimentary rocks (Cowhole volcanics). U-Pb zircon geochronologic data on a crystal-rich dacite lava flow in the Aztec Sandstone indicate that the sandstone is Middle Jurassic and is ther...

A 1:12,000 geological map of the Macao Special Administrative Region has been produced through detailed field work supported by petrographic, mineralogical, geochronological and geochemical data obtained in previous studies. This aims to represent a reliable tool understand evolution region for management territory. The geology is dominated two groups Jurassic granitic rocks belonging an intrus...

To refine the early Middle Miocene (ca. 16 Ma) paleomagnetic direction in the Motegi area, we collected paleomagnetic samples from dacite domes and intrusives of the Motegi Formation. Characteristic remanent magnetization components were revealed by stepwise demagnetization, which were used to calculate site-mean directions for 10 sites. Together with published data from 11 andesite and basalt ...

Five new stepwise-heating Ar/Ar ages and one new high-sensitivity C date of ash-fall and ash-flow deposits from late Quaternary silicic volcanoes in northern Central America document the eruption rates and frequencies of five major rhyodacite and rhyolite calderas (Atitlán, Amatitlán, Ayarza, Coatepeque, and Ilopango) located north of the basalt, andesite, and dacite stratovolcanoes of the Cent...

the study area is located at northwest of sarbisheh in south khorasan province and eastern border of lut block. in this area, tertiary (eocene-oligocene to pliocene) volcanic rocks consisting of basaltic andesite, dacite, rhyodacite, vitreous rhyolite (perlitic in some parts), tuff and ignimbrite are exposed. in the daghar mountain, a, b and c perlite layers with thicknesses of 102, 7 and 58 me...

a r t i c l e i n f o Interferometric synthetic aperture radar (InSAR) images reveal a pre-eruption deformation signal at Kizimen volcano, Kamchatka, Russia, where an ongoing eruption began in mid-November, 2010. The previous eruption of this basaltic andesite-to-dacite stratovolcano occurred in 1927–1928. InSAR images from both ascending and descending orbital passes of Envisat and ALOS PALSAR...

[1] We have modeled the nucleation and isothermal growth of bubbles in dacite from the 1912 Plinian eruption of Novarupta, Alaska. Bubble growth calculations account for the exsolution of H2O and CO2, beginning with bubble nucleation and ending when bubble sizes reproduced the observed size distribution of vesicles in Novarupta pumice clasts. Assuming classical nucleation theory, bubbles nuclea...

[1] Experiments were conducted to study the temporal evolution of feldspar crystallization kinetics during isothermal decompression. Pinatubo dacite was held at 780 C, 220 MPa, fO2 = NNO + 2, H2O-saturated conditions for an equilibration period, decompressed to final pressures, Pf, ranging from 175 to 5 MPa, and then held for 0.3–931 hours. According to the plagioclase liquidus curve in PH2O-T ...

Kepsut-Dursunbey volcanic field (KDVF) is located in NW Turkey and contains various products of the post-collisional Neogene magmatic activity. Two distinct volcanic suites have been recognized; the Kepsut volcanic suite (KVS) and the Dursunbey volcanic suite (DVS). The KVS includes basaltic trachyandesitebasaltic andesite-andesite lavas and associated pyroclastic rocks. The DVS consists of dac...