Abstract In shallow-water limestones of the Plassen Formation in Tirolic nappe Northern Calcareous Alps, bauxite was formed on karstified and tilted platform margin grainstones to boundstones around ?Kimmeridgian/Tithonian boundary, or Early Tithonian as proven by Protopeneroplis striata Weynschenk, Labyrinthina mirabilis Salpingoporella pygmaea Gümbel. The established top obducted ophiolite st...

The origin of silicic rocks in the Michoacán-Guanajuato volcanic field (MGVF) has been understudied since attracted attention researchers. Using geochemical, petrological and structural data from literature, here we propose a model for magmas. We found that all known to date MGVF can be divided 40 % andesite, 33 basaltic 15 basalt, 2 trachybasalt trachyandesite, 10 dacite-rhyolite. systems defo...

Meteorites are interpreted as relics of early formed planetary bodies, and they provide information about the processes that occurred in first few Myrs our solar system. The ages measured for some differentiated meteorites (achondrites), indicate planetesimals a silicate crust ≈3Myr after beginning composition recently discovered achondrite Erg Chech 002 (EC002), oldest andesitic rock known so ...

Future occurrence of explosive eruptive activity at Cotopaxi and Guagua Pichincha volcanoes, Ecuador, is assessed probabilistically, utilizing expert elicitation. Eight eruption types were considered for each volcano. Type event probabilities evaluated the next volcano least one type within 100 years. For type, we elicited relevant source parameters (duration, average plume height, total tephra...

The focus of this thesis is the mineralogy, chemistry, and the understanding of the origin of small (1-5 cm diameter) miarolitic cavities observed in two altered andesitic dikes on West Spanish Peak, Colorado. Twenty rock samples were collected for analysis, and from them 42 thin sections were made for petrographic investigations. Eight of these thin sections were polished and analyzed with the...

Research subject. Andesitic complexes of the Tondono caldera and Lokon-Empung volcano locate din northeastern part Sulawesi Island (Indonesia). Aim. To determine petrogenesis conditions andesites in northeast based on detailed studies volcanic rocks volcano. Materials methods. We studied rock samples collected by I.Yu. Safonova. andesites, conventional petrochemical, geochemical mineralogical m...

Here, we present determinations of thallium (Tl) concentrations in the USGS reference materials BIR-1G, BHVO-2G and BCR-2G measured by solution ICP-MS. The Tl content in these three glasses spans a range of about 2–230 ng g, which is similar to the values published for the respective powder materials. The determined range of Tl concentrations in these three glass reference materials makes them ...

Smith, D. R. and Leeman, W. P., 1993. The origin of Mount St. Helens andesites. J. Volcanol. Geotherm. Res., 55: 271-303. Mount St. Helens volcano has intermittently produced mainly dacitic products but occasionally erupted a more diverse suite of lavas including basalts and andesites. Petrogenetic relations between these magmas provide insight into the dynamics of the subjacent magma system. M...

[1] The effect of H2O on harzburgite-saturated melts has been quantified with a series of hydrous and anhydrous melting experiments using a piston-cylinder device. Experimental conditions were 1.2–2.2 GPa and 1175–1500!C. Melt H2O contents range from 0 to 10 wt %. The effects of temperature, pressure, and bulk composition (including H2O) on the SiO2 content of the experimental melts have been e...