Geochronological framework and tectonic setting of the granitic magmatism in the Chaihe–Moguqi region, central Great Xing’an Range, China
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Devonian
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Several narrow terranes occur along the Denali fault in the Eastern and Central Alaska Range in Southern Alaska. These terranes are the Aurora Peak, Cottonwood Creek, Maclaren, Pingston, and Windy terranes, and a terrane of ultramafic and associated rocks. Exterior to the narrow terranes to the south is the major Wrangellia island arc composite terrane, and to the north is the major Yukon-Tanana metamorphosed continental margin terrane. Overlying mainly the northern margin of the Wrangellia composite terrane are the Kahiltna overlap assemblage to the west, and the Gravina-Nutzotin-Gambier volcanic-plutonic-sedimentary belt to the east and southeast. The various narrow terranes are...
North American Plate
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Based on the great thickness crustal struture and complex geophysical character,this paper points out the principle for dividing terranes in Qinghai─Xizang Plateau according to earthquake activities and wave field sign,lithospheric structure and velocity character,palemagnetic mark,potential field sign ,temperature sign, geological and tectonics character. From north to south of the Qinghai─Xizang Plateau and its neighbouring regions can be devided in seven terranes, ie, Qaidam terrane, Kunlun terrane, Hon Xil-Bayan Har terrane, Qangtang terrane, Lhasa-Gangdise terrane, Himalayan terrane and Ganges Plain terrane. The distribution and character of these terranes have important rools for the studies of the formation and evolution.of the plateau and plate movement and dynamic mechanism.
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Abstract Voluminous plutonic and volcanic rocks were emplaced in the eastern part of the North China Craton (NCC) in the Mesozoic. The Mesozoic igneous rocks include a variety of rock types ranging from monzogabbroic, through monzonitic to monzogranitic, and locally to syenitic. Monzonitic rocks are dominant, and frequently contain mafic enclaves (dioritic in composition). The principal geochemical signatures of these Mesozoic rocks include high-K calc-alkaline to shoshonitic affinity, high Sr–Ba abundances and high Sr/Y, La/Yb, and highly enriched Sr–Nd isotopic compositions with ε Nd ( t ) ranging from −8 to −20 and I Sr from 0.7053 to 0.710. Zircon sensitive high-resolution ion microprobe dating reveals that these Mesozoic rocks formed between 180 Ma and 120 Ma, but are predominantly confined to a narrow range of 135–127 Ma. The sudden surge of Mesozoic magmatism was genetically linked to the upwelling of asthenosphere in a back-arc extensional regime that was caused by subduction of the palaeo-pacific plate beneath the eastern NCC. Upwelling of hot asthenospheric mantle material triggered partial melting of enriched subcontinental lithosperic mantle, generating voluminous mafic magmas. The mafic magmas underplated in the lower crust and sparked melting of the latter, producting granitic melts. We suggest that the Mesozoic rocks in the NCC probably originated from mixing between the coeval mafic and granitic melts, followed by fractionation of ferromagnesian phases and subordinate plagioclase, rather than from melting of mafic lower crust as previously suggested by many others.
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Mesozoic magmatism in the North Huaiyang area,Anhui can be divided into two phases: early high-potassium and calcium alkaline and shoshonite series,and late alkaline rock series.Combination of petrogeochemical characteristics,magmatic activity features,etc indicate polymetallic mineralization was closely related to Mesozoic magmatism.magmatic activity.
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Based on abundant geological data,this paper divides geologically Fujian province into four distinct terranes,namely,Northwest Fujian terrane,Southwest Fujian terrane,East Fujian terrane and Southeast Fujian terrane,and correlates their geological features in detail respectively.Through the study on collision-amalgamation history of each terrrane,it can be concluded that they mainly underwent three stages:(1)in Late Proterozoic,the Southwest Fujian terrane and Northwest Fujian terrane collided and amalgamated along the Nanping-Ninghua fracture zone,being accompanied by submarine and continental volcanic eruptions;(2)in Triassic,the East Fujian terrane collided and amalgamated with the Southwest Fujian terrane and Northwest Fujian terrane along the Zhenghe-Dapu fracture belt,and the Southeast Fujian terrane amalgamated simultaneously with the East Fujian terrane;(3)in Cretaceous,the Southwest Fujian terrane underwent a left-lateral strike slip along the Pingtan-Dongshan fracture zone.
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In southern Alaska, multiple terranes—slabs that have broken off from larger tectonic plates and shuffed around—create a complex patchwork that makes it challenging for scientists to untangle the tectonic history and structure of the region. One of these, the Yakutat terrane, which lies just offshore southern Alaska in the Gulf of Alaska, is converging with the North American plate and driving the growth of the Chugach–St. Elias mountains. The structure of this terrane has not been well studied until now. Worthington et al. conducted seismic studies to create a two‐ dimensional seismic velocity model of the Yakutat terrane. The model allows them to constrain the crustal thickness and composition of the terrane.
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