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Great Rift Valley Mid-Oceanic Ridge Baikal Rift Zone http://en.wikipedia.org/wiki/Baikal_Rift_Zone Kamchatka-Aleutian Triple Junction Queen Charlotte Triple Junction The Queen Charlotte Triple Junction is a geologic triple junction where three tectonic plates meet: the Pacific Plate, the North American Plate, and the Explorer Plate. The three plate boundaries which intersect here are: the Queen Charlotte Fault, the Cascadia subduction zone, and the Explorer Ridge. Mendocino Triple Junction The Mendocino Triple Junction is a geologic triple junction where the San Andreas Fault meets the Mendocino Fault and the Cascadia subduction zone, separating three tectonic plates: the Pacific Plate, the North American Plate and the Gorda Plate. It is located just offshore of Cape Mendocino in northern California Mendocino Triple Junction Offshore Northern California http://woodshole.er.usgs.gov/operations/obs/rmobs_pub/html/mendocino.html The Mendocino Triple Junction (MTJ) is one of the most seismically active regions of the San Andreas transform system. Since 1983 the region (Figure 1) has generated about 80 M3.0 quakes each year, and historically the region has experienced major quakes. This activity is generated in response to ongoing plate motions between the Gorda, North America, and Pacific plates. Triple junction http://en.wikipedia.org/wiki/Triple_junction A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction a boundary will be one of 3 types - a ridge, trench or transform fault and triple junctions can be described according to the types of plate margin that meet at them. Of the many possible types of triple junction only a few are stable through time. The Amurian Plate, the Okhotsk Plate, and the Philippine Sea Plate is also triple junction Divergent boundary Rift East African Rift Rede Sea Rift Gulf of Suez Rift Basin and Range Province Timiskaming Rift Valley Rio Grande Rift, USA Gulf of Corintyh, Greece ReelFoot Rift Rhine Rift Taupo Volcanic Zone Oslo Rift Ottawa-Bonnechere Graben Northern Cordilleran Volcanic Province The Northern Cordilleran Volcanic Province (NCVP), formerly known as the Stikine Volcanic Belt West Antarctic Rift Midcontinent Rift System (MRS) or Keweenawan Rift Fundy Basin Gulf of California Rift Zone The Gulf of California Rift Zone (GCRZ) is the northernmost extension of the East Pacific Rise which extends some 1300 km from the mouth of the Gulf of California to the southern terminus of the San Andreas Fault at the Salton Sink. The GCRZ is an incipient rift zone akin to the Red Sea Rift where continental crust associated with the North American Plate is being pulled apart by tectonic forces and being replaced by newly-formed oceanic crust and seafloor spreading THE ARCTIC RIFT SYSTEM http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0687303 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V72-48B5DTD-KB&_user=10&_coverDate=12%2F31%2F1969&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1483380019&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=d13aabce0e6957c65da90764a767b693&searchtype=a A short description is presented of the topography, sediments and magnetic anomaly pattern of the Gakkel (Mid-Arctic) Ridge which together with the adjoining abyssal Nansen and Amundsen basins forms the Eurasian Basin of typical oceanic nature in the Arctic Ocean. The Eurasian Basin is characterized by a linear, symmetric pattern of magnetic anomalies with prominent axial anomaly typical of the world mid-oceanic ridge system. A number of fracture zones have been deduced from the magnetic data and a preliminary estimate of the average rate of spreading of about 1.1 cm/year for the last 8–10 million years in the Eurasian Basin is obtained. Some evidence indicating the possible continental extension of the rift zone of the Gakkel Ridge into the Moma Trough is presented. The Tatar Continental Rift The Tatar Continental Rift - Large Cenozoic Extension structure, boundared by the convergent system of submeridional dextral strike-slip faults partly transformed to normal faults. The continental crust began to breake down in Paleocene-Eocene into a system narrow horst and grabens (5-10 km)and accumulation of sediments 1.5 km thick. The Tatar Continental Rift Abstract The paper presents data on pull-apart (synchronous with strike-slip faulting) extensional structures formed in relation to Indo-Eurasian collision and including continental marginal rifts in East Asia and adjacent marginal sea basins. The evolution of Cenozoic pull-apart basins (developing synchronously with strike-slip faulting) in the western surroundings of the Pacific ocean corresponds to a basaltoid sequence in which the onset of rifting and the stage of maximum extension are marked by the first and last members of this sequence that have, respectively, calc-alkaline and tholeiitic depleted composition. The predominance of intermediate members with mixed isotopic-geochemical signatures testifies to the interaction of diverse magmatic melts. The opening of pull-apart basins (including those of marginal sea) was associated with magmatism whose sources were localized, judging from geochemical indicators, in the modified continental lithospheric mantle and depleted asthenosphere. The sources in the lithospheric mantle that was affected by long-lasting metasomatic recycling in the geological past dominated during the initial stages of continental extension and gave way to depleted asthenospheric sources. This model is consistent with the deep structure of the territories: extensional basins correspond to asthenospheric upwelling, with the ascent of asthenospheric diapirs positively correlated with the intensity of extension of the continental lithosphere and the degree of depletion of the accumulated basaltoids. The discovery of widespread calc-alkaline rocks (which are genetically related to the ancient metasomatized lithospheric mantle) in zones of continental rifting and marginal basins of the strike-slip fault nature significantly broadens the compositional range of volcanics typical of extensional geodynamic environments. At the same time, this testifies to the polygeodynamic nature of calc-alkaline volcanics, which can accumulate without any relations with coeval subduction zones. Original Russian Text © N. I. Filatova, 2008, published in Petrologiya, 2008, Vol. 16, No. 5, pp. 480–500 ПОПЕРЕЧНАЯ ЗОНАЛЬНОСТЬ, РИФТИНГ http://plate-tectonic.narod.ru/orogen2photoalbum.html РИФТОГЕНЕЗ http://plate-tectonic.narod.ru/riftphotoalbum.html Source - http://avspir.narod.ru/geo/khain1995/hain_5_1.htm большинство рифтовых зон (в широком понимании) находится в океанах, однако там рифты как структуры, контролируемые сбросами, имеют подчиненное значение, а главным способом реализации растягивающих напряжений служит раздвиг. |
