The most frequent and voluminous eruptive Kurasawa, 1983], (4) partial melting of the lower crust products at Mount St. Helens are dacitic in composition, [e.g., Grant et al., 1984; Reid and Cole, 1983], and (5) although a wide variety of magma types (basalt to formation of compositional gradients in response to rhyodacite) is represented. To address the petrogenesis of convective and diffusive...

[1] The radiogenic isotopic ratios of Sr, Nd, Hf, and Pb in basaltic lavas associated with major hot spots, such as Hawaii, document the geochemical heterogeneity of their mantle source. What processes created such heterogeneity? For Hawaiian lavas there has been extensive discussion of geochemically enriched source components, but relatively little attention has been given to the origin of dep...

Ferric/ferrous ratios have been used to estimate the oxygen fugacity of lavas erupted in 1984 on Mauna Loa Volcano, Hawaii. Rapidly quenched lavas erupted close to vents are less oxidized than rapidly quenched lavas scooped from lava flows several kilometers away from the vents. These results demonstrate that sampling is of critical importance in determining the oxidation state of lava. The oxi...

Slope instability in the Butterfly Biosphere Reserve (RBMM) Michoacán, Mexico, is a widespread phenomenon that results from complex interaction among different factors such as climate, slope, and spatial distribution of rock units. The climate temperate subhumid, with rains summer an annual average rainfall 700 to 1250 mm. main physiographic units area are volcanic mountains, slopes greater tha...

Abstract Glaciovolcanic deposits at Tongariro and Ruapehu volcanoes, New Zealand, represent diverse styles of interaction between wet-based glaciers andesitic lava. There are iceconfined lavas, also hydroclastic breccia subaqueous pyroclastic that formed during effusive explosive eruptions into meltwater beneath the glacier; they rare among globally reported products glaciovolcanism. The appare...

The lava section in the Troodos ophiolite, Cyprus, is chemically stratified and divided into a shallow lava sequence with low TiO2 content and a deeper lava sequence with high TiO2 content. We calculate the viscosity at magmatic temperature based on major element chemistry of lavas in Cyprus Crustal Drilling Project (CCSP) Holes CY-1 and 1A. We find that typical shallow low-Ti lavas have a magm...

In the Central Andes, large (> 500 km2) and long-lived (1–5 Ma) volcanic clusters (LVCs) are less explored their eruptive history magmatic regimes understood than smaller, short-lived (<0.5 Ma), individual stratocones. The Chachani-large cluster (C-LVC) sizeable volume (c. 290 km3) consists of twelve edifices forming 1.06–0.64 Ma group stratovolcanoes 0.46–0.05 domes coulees block-lava flow fie...

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...

Young intra-transform lavas erupted as a result of extension within the Garrett Transform Fault on the southern East Pacific Rise, are more porphyritic, less evolved, have lower concentrations of incompatible trace elements, and lower ratios of more incompatible to less incompatible elements (e.g. low K=Ti and La=Sm) compared to lavas from the adjacent East Pacific Rise ridge axis. Sr, Nd and P...