نتایج جستجو برای: plagioclase
تعداد نتایج: 1579 فیلتر نتایج به سال:
Melt inclusions with large, positive Sr anomalies have been described in multiple tectonic settings, and the origins of this unusual geochemical feature are debated. Three proposed, all involving plagioclase as source elevated Sr: (i) direct assimilation plagioclase-rich lithologies, (ii) recycled lower oceanic gabbro mantle source, (iii) shallow-level diffusive interaction between present day ...
At the first site, the Weinsberg (Moldanubian) granite and an older quartzmonzonite facies of the South Bohemian pluton in Austria both contain orthopyroxene and clinopyroxene and must have crystallized from magmas at high temperatures. The granite contains orthoclase megacrysts (as much as 10 to 20 cm long), which (1) are chemically zoned with Ba-rich cores (1 to 2 % mol Cs; and locally as muc...
Timescales of magma ascent in conduit models are typically assumed to be much longer than crystallization and gas exsolution for basaltic eruptions. However, it is now recognized that basaltic magmas may rise fast enough for disequilibrium processes to play a key role on the ascent dynamics. The quantification of the characteristic times for crystallization and exsolution processes are fundamen...
Introduction. The Mócs meteorite is L5-type chondrite, which fell in 1882, Kolozs county. The meteorite major modal composition are: olivine, pyroxene, plagioclase feldspars, and opaque minerals. The meteorite is highly fractured, and shock induced veins are also discernible. The fractures are filled by iron rich material. The sample contains shock-metamorphic effects (especially in olivine), s...
Mineral chemistry, major and trace elements and Sr-Nd isotopes are presented for basalts and trachybasalts from the Quaternary alkaline Tepi shield from southwest Ethiopia. The lavas are variably porphyritic with phenocrysts of olivine (Fo67–87), clinopyroxene (Wo45–47En38–40Fs13–16), plagioclase (An57–68) and Ti-magnetite set in a microcrystalline matrix. Although there are two high-MgO lavas ...
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