نتایج جستجو برای: dacite
تعداد نتایج: 251 فیلتر نتایج به سال:
Ruapehu (150 km3 cone, 150 ring-plain) and Tongariro (90 60 are iconic stratovolcanoes, formed since ∼230 ∼350 ka, respectively, in the southern Taupo Volcanic Zone Rift. These volcanoes rest on Mesozoic metasedimentary basement with local intervening Miocene sediments. Both have complex growth histories, closely linked to presence or absence of glacial ice that controlled distribution preserva...
The origin of silicic rocks in the Michoacán-Guanajuato volcanic field (MGVF) has been understudied since attracted attention researchers. Using geochemical, petrological and structural data from literature, here we propose a model for magmas. We found that all known to date MGVF can be divided 40 % andesite, 33 basaltic 15 basalt, 2 trachybasalt trachyandesite, 10 dacite-rhyolite. systems defo...
Eocene volcanic rocks in SW of Choupanan are exposed along the Choupanan fault as lava with andesite, trachyandesite to dacite composition and pyroclastic rocks. This area is a part of Central Iran (Yazd block). Andesite is the most predominant rock unit of the area and is composed of feldspars (andesine, oligoclase, and sanidine), amphibole (magnesio hastingsite, magnesian hastingsite, magnesi...
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 ...
In southwest of Birjand, the Tertiary igneous rocks have oxposed in Cretaceous flysch type deposits. These bodies are made of micro quartzmonzodiorite, trachyandesite, andesite and dacite. The main texture in these rocks is porphyry. Their phenocrysts are plagioclase, hornblende and biotite. Plagioclases contain zoning. Pyroxene, quartz and opaque minerals are in groundmass. Often, hornblendes ...
The study area is located south of Nehbandan, in southern Khorasan Province. There are three mineralization zones with three veins in this area which number two is antimony rich and has anomaly for Au and Hg. This zone is composed of silica-carbonate with stibnite, pyrite, chalcopyrite and Fe-hydroxide. The textures of veins are open space filling, brecciate and colloidal. Mineralization occurr...
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...
The Sanjiang Indosinian orogen, located in the eastern part of Paleo-Tethys tectonic domain, is a critical region to study Paleo-Tethyan Ocean evolution. Middle Permian–Late Triassic magmatic rocks are widespread Deqin–Weixi–Madeng area southwestern (SW) yet their petrogenesis and setting remain disputed. In this study, LA-ICP-MS zircon U-Pb age Hf isotopes, whole-rock elemental Sr-Nd isotope g...
Abstract We examine the connected history of dacite-dominant volcanic rocks Tschicoma Formation, erupted between 5.5 and 2 Ma from Jemez Mountains field, western USA. Zircon samples two separate eruptions have continuous SHRIMP U–Pb age spectra spanning 0.84–1.08 Myr duration (3.12–3.96 3.50–4.58 Ma, respectively), following an episode zircon crystallization 0.28–0.50 earlier (at 4.46 4.86 resp...
Volcanic rocks in the Miramichi inlier Maine occur two areas separated by Bottle Lake plutonic complex: Danforth segment (Stetson Mountain Formation) north of complex and Greenfield to south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, rhyolite tuffs subordinate lavas, breccias, agglomerates. Rare basaltic a small area tuffs, agglomerates, l...
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