نتایج جستجو برای: volcanic arc
تعداد نتایج: 50065 فیلتر نتایج به سال:
Post-Eocene volcanic rocks of Alborz tectonic zone located in the NE of Qazvin, composed of rhyolite, trchydacite, trachyandesite, andesite, trachybasalt and basalt with porphyritic textures, pyroclastic rocks and volcanic red breccia which are settled alternatively on Eocene pyroclastics and tuffs. The volcanic rocks are enriched in LIL and depleted in HFS elements which may indicate a calc-al...
The study area is located in North-East of Lut block, and in Basiran Geological Quadrangle Map (1:100000).Tertiary intrusive-subvolcanic rocks intruded Paleocene limestone and formed skarn and Iron mineralization. Petographic studies show that rocks are Hbl-diorite porphyry, Hbl-qtz- diorite porphyry, Px- diorite porphyry, Hbl-px- diorite porphyry, Hbl-diorite and Bt-diorite. These rocks are s...
I prepared compilations of geochemical data from the central part of the Mexican Volcanic Belt (C-MVB), the Central American Volcanic Arc (CAVA) from Guatemala to northwestern Costa Rica, the continental arc of the Andes in South America, other mostly island arcs, extensional and continental break-up regions, and continental rifts. Using quantitative statistical methods, the origin of the C-MVB...
Active microplate boundaries in ocean-continent subduction zones may induce deformation of the overlying plate and spatial or geochemical variations in the volcanic arc. We discuss two modern cases. The first is the South Gorda-Juan de Fuca plate boundary in the Cascadia subduction zone, where there is little or no effect on the overriding plate and the oceanic plate takes up much of the deform...
Intraplate volcanism initiated shortly after the cessation of Cenozoic seafloor spreading in the South China Sea (SCS) region, but the full extent of its influence on the Indochina block has not been well constrained. Here we present major and trace element data and Sr-Nd-Pb-Hf isotope ratios of late Cenozoic basaltic lavas from the Khorat plateau and some volcanic centers in the Paleozoic Sukh...
Active volcanoes give significant threats to the populations that live in their proximity. The Three Sisters Volcanic region is one of 9 threatening volcanoes within the Cascades volcanic arc. Eruptions are probable which makes it essential to complete hazard, vulnerability, and risk assessments so that proper planning, education and mitigation procedures can be implemented prior to the threat ...
rocks of the Stuhuni and King Salmon Groups; a pre-.Middlm: Triassic unconformity is found througbmt the North American Cordillera (Read and Okulitch, 1977, Siberling, 1973:. In the Stikine Terrane, late Triassic volcanic rocks ar: dominantly fragmental andcommonly alkalic. Based on bul:: rock chemistry, both extensional, ba:k-arc, and Fore-ar: tectonic settings have been suggested tor these r...
Neogene high silica adakitic domes of south Quchan, cropped out in the northern part of the Quchan-Esfarayen Cenozoic magmatic arc (north of Sabzevar ophiolitic and metamorphic belt). In this volcanic belt, magmatic activities has been started since Eocene (about 40 Ma ago) and continued to Plio-Pleistocene (about 2 Ma ago). The ages of volcanic rocks range from Eocene to Plio-Pleistocene from ...
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