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...

An integrated study involving whole-rock and Sr–Nd–Hf isotope geochemistry and zircon geochronology and trace element combined with detailed field investigation was carried out for the composite Meiwu batholith in the West Qinling orogenic belt of central China to probe the origins of its compositional diversity and its emplacement history. The batholith is composed of quartz diorite, granodior...

Inclusions of quenched mafic magma occur in a 21 Ma rhyolite lava and precursory non-welded tuff that form the Spor Mountain Formation in west-central Utah. The mafic inclusions are not lithic inclusions; no comparable volcanic unit was present at the surface when the Spor Mountain Formation erupted. Mineral and bulk compositions preclude liquid immiscibility. The mafic inclusions show clear mo...

High-magnesian andesite occurs at Hachimantai, northern Honshu, Japan. Disequilibrium zoning features indicate that the phenocryst minerals were derived from three different magmas. Chemical compositions and zoning profiles are accounted for by two-stage magma mixing: the first mixing occurred between a crystal-free basalt magma and a more differentiated olivine basalt magma; the second stage o...

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...

Mafic enclaves from three plutons in the Chilliwack batholith have been compared with contemporaneous mafic stocks in order to determine (1) the processes by which mafic and felsic magmas hybridize in the plutonic environment and (2) whether analysis of early-formed enclave minerals, particularly apatite, can provide a means of seeing through hybridization effects and deciphering the original t...

dyke swarms emplacement constitutes one of the conspicuous features of the neoproterozoic arabian-nubian shield (ans) (~950-540ma). based on field investigations, petrographic and geochemical characteristics the dyke swarms in nw sinai (egypt) comprise of mafic (dolerite-trachy-basalt-basalt), intermediate (basaltic-andesite trachy-andesite) and felsic (rhyodacite-rhyolite) varieties. geochemic...

Introduction: Although mafic components of dominantly intermediate to silicic ignimbrites are rather common, voluminous, dominantly mafic ignimbrites are rare (e.g., Smith, 1979; cf. Freundt and Schmincke, 1995). Volcán Villarrica, the most active composite volcano in South America, located in the Southern Andean Volcanic Zone (SAVZ, López-Escobar and Moreno, 1994a), has produced two such ignim...

Large Ra excesses in a number of mafic arc magmas, and geophysical observations of earthquake hypocenters locations, indicate that mafic melts can get transferred from source to surface within days to ~1 kyr. Decreasing Ra–Th disequilibria with increasing SiO2 in co-magmatic suites of individual arc volcanoes suggest that magma differentiation often occurs on timescales of a few thousand years ...