Fifteen andesite-dacite stratovolcanoes on the volcanic front of a single segment of the Andean arc show along-arc changes in isotopic and elemental ratios that demonstrate large crustal contributions to magma genesis. All 15 centers lie 90 km above the Benioff zone and 280 _+ 20 km from the trench axis. Rate and geometry of subduction and composition and age of subducted sediments and seafloor...

The central Oregon section of the Cascade Range volcanic arc is characterized byrelatively high Quaternary volcanic extrusion rates and hot-spring discharge rates, and by high conductive h at flow. However, a large area of near-zero near-surface onductive h at flow occurs in the younger volcanic rocks, due to downward and lateral flow of cold groundwater. Alternate models for the high heat flow...

Abstract Eastern Indonesia has a complicated structure due to the collision of Eurasian Plate, Pacific Indo-Australian and Philippine creating an active seismic zone. The Banda - Seram segment eastern comprises subduction, rollback, detachment, slab tear, back-arc thrust, volcanic arc. Sri Widiyantoro did previous study in utilizing tomography methods detect upper mantle 180-degree curved trans...

volcanic rocks of interest are situated in the middle part of the urumieh-dokhtar magmatic arc (udma). they are parts of a vast magmatic province located in the north of bitlis-zagros suture zone. having a prevailing porphyritic texture, these rocks include phenocrysts of plagioclase, amphibole and biotite in a matrix composed of feldspar, quartz, opaque, glass and microlite and mineralogically...

Oxygen isotope data are reported for clinopyroxene phenocrysts from volcanic rock samples from Filicudi island, Italy, with the aim of investigating mechanisms of magma evolution and mantle source characteristics in a continental arc volcano. Filicudi rocks range from calc-alkaline basalt to high-K andesite and dacite. Mafic rocks have MgO 6-7 wt%, Mg# 60, Ni < 50 ppm and Cr < 200 ppm, suggesti...

Arc magmas are distinguished from those of other tectonic settings by several first order characteristics; 1) they tend to be realtively differentiated with even the most mafic rocks in a suite typically ≥50% SiO2, 2) they typically contain high H2O contents and 3) they have distinctive trace element signatures. The “standard” model for arc petrogenesis involves melting of a mantle wedge, preco...

Anorthite megacrysts from twelve volcanic centers of the Kurile Island Arc were analyzed by the ion microprobe for concentrations of: Li, Be, B, F, Mg, P, Cl, K, Ti, Fe, Co, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, and Pb. These 1–2-cm megacrysts are mainly found as early phenocrysts in basalts, but are also present in andesites, rhyolites and hybrid rocks from almost every studied vo...

the shahabad gabbroic intrusion, with nw-se trend cropped out at the boundary of zagros and sanandaj-sirjan zones is composed of olivine gabbro, orthogabbro and troctolite. plagioclase, clinopyroxene and olivine are the main minerals; and magnetite, titanomagnetite and serpentine are minor and secondary minerals. microprobe analyses of the minerals show that plagioclase is labradorite, pyroxene...