Detailed stratigraphic sampling of formations from Somma-Vesuvius (Southern Italy) volcano complex erupted during the last 3550 years of inteplinian activity provide a framework for comprehensive chemical analyses and isotopic studies. The evolution of majorand trace-element abundances of these rocks suggest that fractional crystallization together with crustal assimilation are only a partial e...

The plutonic complex in SE Jersey consists of a late Precambrian gabbro-diorite mass which has been intruded by several granites. The status of the diorites which, like the gabbros, often possess a layered structure, is not clear. New geochemical data, including rare earth and trace element analyses, suggest that acid-basic magma mixing was not responsible for the variety of intermediate rocks....

Major overturn within a magma chamber can bring together felsic and mafic magmas, prompting de-volatilisation and acting as the driver for Plinian eruptions. Until now identification of mixing has been limited to analysis of lavas or individual crystals ejected during eruptions. We have recovered partially developed cumulate material ('live' cumulate mush) from pyroclastic deposits of major eru...

The Miocene pyroxene andesite lava flows are exposed in southeastern edge of Urumieh Dokhtar Magmatic assemblage in Iran. The hypocrystalline andesite in parts contain conspicuous co-magmatic igneous enclaves which are dark grey and occur mostly as spherical and occasionally as ribbon shapes with some showing chilled margins. Petrographic study shows that the ribbon type enclaves have been form...

The volcanic island of Surtsey (Vestmannaeyjar, Iceland) is the product of a 3.5-year-long eruption that began in November 1963. Observations of magma-water interaction during pyroclastic episodes made Surtsey the type example of shallow-to-emergent phreatomagmatic eruptions. Here, in part to mark the 50(th) anniversary of this canonical eruption, we present previously unpublished major-element...

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...

The 465 Ma Svarthopen pluton in northcentral Norway was emplaced under middle-crustal conditions (~700 MPa) into metasedimentary rocks of the Helgeland Nappe Complex. The pluton is characterized by zones of mingling and mixing of gabbro/ diorite with peraluminous, garnet-bearing biotite granite. Variation in bulk-rock Sr and Nd isotope ratios are consistent with simple mixing; however, nonunifo...

Major element compositions of glass inclusions in olivine and plagioclase phenocrysts from representative Mariana arc lavas show that mafic Mariana arc liquids are tholeiitic and not high-alumina, implying that the high-alumina characteristic of these lavas reflects accumulation of plagioclase. Glass inclusions also show the common occurrence of felsic melts previously unrecognized among Marian...