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...

-Oxygen isotope composition of three types of unique nodules which consist of amorphous silica-apatite, cristobalite-apatite and tridymite-apatite associations interspersed amidst basaltic pyroclastics from the Hat Peres volcano, Golan Heights, Israel is reported. Unusual isotopic temperature (75~ estimated from oxygen isotope fractionation between cristobalite (6'80 = +25.5%0-apatite (6'80 = +...

Experimental petrology and major element chemistry are used to infer the melting processes that operate in the upper oceanic mantle to yield basaltic magma, and the subsequent cooling processes by which these magmas chill to form the oceanic crust. THE PRIMARY MAGMAS OF MID-OCEAN RIDGE BASALTS This paper reports experiments carried out between 9 and 16 kbar (0.9 1.6 GPa) using natural, primitiv...

Introduction: The Mars Exploration Rover Opportunity has obtained chemical and mineralogical data for exposed bedrocks at Meridiani Planum on Mars. In using these data to formulate a diagenetic model for the bedrocks, a clear distinction must be made between the primary inputs into the rocks and products of secondary processes. The chemical composition of the Meridiani bedrocks provides the mos...

Accurate forecasts of lava flow length rely on estimates of eruption andmagma properties and, potentially more challengingly, on an understanding of the relative influence of characteristics such as the apparent viscosity, the yield strength of the flow core, or the strength of the lava’s surface crust. For basaltic lavas, the relatively high frequency of eruptions has resulted in numerous oppo...

Potential flank eruptions at the presently active Villarrica, Southern Andes Volcanic Zone (33.3–46 °S) require drawing of a comprehensive scenario eruptive style dynamics, which partially depends on degassing process. The case we consider in this study is from Los Nevados Subgroup 2 (LNG2) and constitutes post-glacial minor centers (MECs) basaltic–andesitic basaltic composition, associated wit...

Basaltic pyroclastic volcanism takes place over a range of scales and styles, from weak discrete Strombolian explosions (!10–10 kg s) to Plinian eruptions of moderate intensity (10–10 kg s). Recent well-documented historical eruptions from Etna, Kı̄lauea and Stromboli typify this diversity. Etna is Europe’s largest and most voluminously productive volcano with an extraordinary level and diversit...

Rhyolite lavas and xenoliths from the Salton Sea geothermal field (Southern California) provide insights into crustal compositions and processes during continental rupture and incipient formation of oceanic crust. Salton Buttes rhyolite lavas contain xenoliths that include granophyres, fine-grained altered rhyolites (“felsite”), and amphibole-bearing basalts. Zircon is present in lavas and xeno...