The Indian Peak volcanic field is representative of the more than 50,000 km3 of ashflow tuff and tens of calderas in the Great Basin that formed during the Oligocene-early Miocene "ignimbrite flareup" in southwestern North America. The field formed about 32 to 27 Ma in the southeastern Great Basin and consists of the centrally positioned I n d i Peak caldera complex and a surrounding blanket of...

amygdaloidal, cavity- and fracture-filling zeolites in eocene volcanic rocks from the kuh-e-aradeh of southern kahrizak, in the northernmost part of central iran have been studied in some detail by optical, chemical analysis, sem, and xrd techniques. the zeolites identified, in order of their relative time of formation from early to late, are tetranatrolite, analcime, natrolite, mesolite, stilb...

Unlike the other terrestrial planets, Earth has a substantial silica-rich continental crust with bulk andesitic composition. A small number of meteorites compositions have been identified that are thought to be products partial melting chondritic protoliths, mode petrogenesis distinct from Earth’s crust. Here we show, using geochemical analyses, unlike known meteorites, Erg Chech 002 strongly f...

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...

Water is an important volatile component in andesitic eruptions and deep-seated andesitic magma chambers. We report an investigation of H2O speciation and diffusion by dehydrating haploandesitic melts containing 62.5 wt.% water at 743–873 K and 100 MPa in cold-seal pressure vessels. FTIR microspectroscopy was utilized to measure species [molecular H2O (H2Om) and hydroxyl group (OH)] and total H...

The total magmatic output in modern arcs, where continental crust is now being formed, is believed to derive from melting of the mantle wedge and is largely basaltic. Globally averaged continental crust, however, has an andesitic bulk composition and is hence too silicic to have been derived directly from the mantle. It is well known that one way this imbalance can be reconciled is if the paren...

ABSTRACT Erg Chech (EC) 002 is a meteorite with andesitic composition, potentially recording the lava crystallization and crust formation of its parent body. Nucleosynthetic Cr isotope composition (?54Cr = ?0.35 ± 0.06) for EC suggests non-carbonaceous region Solar system, possibly represents crustal brachinite The 53Mn-to-53Cr decay system shows it crystallized at 4566.6 0.6 Ma, i.e. 0.7 Ma af...

Volcanic cinder, also known as scoria, is an extrusive igneous rock that forms when gas-rich magmas of basaltic or andesitic composition cool quickly. It typically dark in color, ranging from black to red depending on its chemical composition. Sometimes fresh cinder samples show a variety shiny metallic colors surface blue gold silver. The origin these has remained unknown up now. Cinder erupti...

hydrothermal alteration processes are extensively took place on volcanic and pyroclstics of takestan area. existence of abundant, deep fracturing and subvolcanic intrusions are enhanced extend hydrothermal alteration zones. the following alteration zones are determined: propylitic, argillic, advanced argillic and sillicic. there are outcropped and widespread in different size and limit. formati...