نتایج جستجو برای: andesitic composition
تعداد نتایج: 260052 فیلتر نتایج به سال:
Thin oceanic crust is formed by decompression melting of the upper mantle at mid-ocean ridges, but the origin of the thick and buoyant continental crust is enigmatic. Juvenile continental crust may form from magmas erupted above intraoceanic subduction zones, where oceanic lithosphere subducts beneath other oceanic lithosphere. However, it is unclear why the subduction of dominantly basaltic oc...
The straightforward but unexpected relationship presented here relates crustal thickness to magma type in the Izu-Ogasawara (Bonin) and Aleutian oceanic arcs. Volcanoes along the southern segment of the Izu-Ogasawara arc and the western Aleutian arc (west of Adak) are underlain by thin crust (10-20 km). In contrast those along the northern segment of the Izu-Ogasawara arc and eastern Aleutian a...
Textural and Geochemical characteristics of plagioclase phenocrysts in Andesitic and basaltic rocks of Bazman volcano (from Makran volcanic arc) show evidence of interaction between basaltic and andesitic magmas. Plagioclase phenocrysts in andesites and basalts are composed of three major parts of core, mantle and rim, with similarity of the anorthite contents in cores and mantles. The cores of...
Point-counted modes, representative mineral analyses, and whole-rock majorand trace-element compositions determined by X-ray fluorescence spectroscopy and inductively coupled plasma mass spectroscopy (ICP-MS) are presented for 11 samples of the hornblende^andesite block-lava flows erupted from Volca¤n de Colima in 1991 and 1998^1999. New ICP-MS trace-element data are also presented for 37 andes...
Radon-222 diffusion in an anhydrous andesitic melt was investigated. The melts were glass discs formed artificially from melted volcanic materials. Solutions of the relevant diffusion equations were done by the explicit finite difference method. Results were compared to analytical solutions reported in the literature and good agreement was found. We have shown that the explicit finite differenc...
چکیده ندارد.
Extrusive igneous rocks are formed the main part of geological units in northeast region of Birjand. Investigation shows that these igneous rocks can be divided into rhyolitic, dacitic, andesitic and an especial group including basaltic andesite and basalts. In Later group that differ from the others according to geochemical and mineralogical characteristics, there are limited outcrops of high ...
Eocene volcanic rocks of north Anarak area are as scattered as masses. These rocks cross the Anarak schists and Ashin-Zavar ophiolites but had not metamorphosed them. Their outcrops follow the direction of within the area faults. Mineralogicaly, these rocks are limited in composition from Andesi-Basalt and Andesite to Dacite. These rocks have phenocrysts of amphibole and plagioclase in microcry...
Abstract Mocho-Choshuenco volcano has produced several highly explosive eruptions during its history, which make it one of the most hazardous volcanoes in southern volcanic zone Chile, although is still relatively little studied to date. We present a geochemical study products sub-Plinian, andesitic, Enco eruption that occurred about 1600 years ago. determined major and trace elements compositi...
Primitive arc magmatism and mantle wedge processes are investigated through a petrologic and geochemical study of high-Mg# (Mg/Mg ? Fe [ 0.65) basalts, basaltic andesites and andesites from the Kurile-Kamchatka subduction system. Primitive andesitic samples are from the Shisheisky Complex, a field of Quaternary-age, monogenetic cones located in the Aleutian–Kamchatka junction, north of Shiveluc...
نمودار تعداد نتایج جستجو در هر سال
با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید