نتایج جستجو برای: alkaline volcanic
تعداد نتایج: 57247 فیلتر نتایج به سال:
Volcanic hazards assessment tools are essential for risk mitigation of volcanic activities. A number of offline volcanic hazard assessment tools have been provided, but in most cases, they require relatively complex installation procedure and usage. This situation causes limited usage of volcanic hazard assessment tools among volcanologists and volcanic hazards communities. In addition, volcani...
Spherulitic structures are classically defined as concentrically zoned crystal clusters that form in igneous systems (especially alkaline rocks), and usually occur different mineral layers or shells.
 The volcano-sedimentary series observed the Kırka region, south of Eskişehir, within Kırka-Afyon-Isparta Volcanic Province, Western Anatolia, consists predominantly Lower Miocene volcanic pyr...
In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thu...
85 The physiography of the area is dominated by glaciated landforms carved in gneiss of the Fiordland Complex. The gneiss is generally dioritic, with gradations to quartzo-feldspathic and amphibolitic varieties, and is cut by mainly barren pegmatite veins; epidote is abundant. The rocks commonly show signs of post-consolidational shearing and crushing. There is a well defined zone of strongly c...
The Upper Cretaceous volcanic and subvolcanic rocks from the Nageleh Sar, south of Mahmood Abad town in north Iran are dolerite, olivine basalt, trachyandesite and alkali trachyte. These units in an ordered stratification are set in a way that creates a syncline with WNW-ESE axial trend. The chemical data and discrimination diagrams represent medium alkaline bimodal series for the studied sampl...
The composition of Kuh-e- Barandeh volcanic dome is andesite, dacitic andesite and dacite of calc-alkaline affinity. A prominent feature of this dome is the presence of various types of enclaves with different composition, shape and size. Detailed field and laboratory investigation proved that they are of xenolith and autolith types. The xenoliths are of pelitic and basic protoliths. Xenoliths ...
The study area is located in the Kerman province, 10 Km north of Rabor. Geologically, the area is situated in the eastern section of Dehaj-Sarduiyeh belt which is a part of Urumieh-Dokhtar magmatic assemblage. The dykes were intruded in the Eocene pyroclastic rocks and Pliocene sedimentary units. Petrographic studies show that these rocks are andesitic in composition. Mineralogically they are c...
Fathabad area is located in northwest of the city of Zarand (Kerman province) in the Posht-e-Badam block of the central Iran structural zone. The Ordovician–Silurian gabbroic stocks have intruded into volcanic-sedimentary rocks of the Rizu series. The gabbros are mainly composed of clinopyroxene, kaersutite, plagioclase and biotite. Electron microprobe analyses demonstrate that the clinopyroxen...
The study area is located about 105 kilometers east of Sarbisheh in Southern Khorasan and in the Sistan suture zone. The magmatic rocks of this area are exposed as intrusive and sub volcanice including diorite, quartz diorite, porphyry quartz diorite and porphyry diorite with Oligocene- Miocene age. These rocks have granular, porphyry with fine- grained matrix, ophitic, intergranular and glomer...
In the southeast of Nir, south of Yazd Povince, several acidic volcanoes rocks are exposed and form the youngest volcanic rocks in this region with dacite-rhyodacite composition. These rocks are composed of plagioclase, hornblende, biotite and quartz phenocrysts with trachytic and hyallomicrolithic porphyry texture. Based on geochemical data, the magmatic affinity of these rocks is calc-alkali...
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