A-type granites: geochemical characteristics, discrimination and petrogenesis
TL;DR: A-type granites as mentioned in this paper were found to have high SiO2, Na2O+K2O, Fe/Mg, Ga/Al, Zr, Nb, Ga, Y and Ce, and low CaO and Sr.
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Abstract: New analyses of 131 samples of A-type (alkaline or anorogenic) granites substantiate previously recognized chemical features, namely high SiO2, Na2O+K2O, Fe/Mg, Ga/Al, Zr, Nb, Ga, Y and Ce, and low CaO and Sr. Good discrimination can be obtained between A-type granites and most orogenic granites (M-, I and S-types) on plots employing Ga/Al, various major element ratios and Y, Ce, Nb and Zr. These discrimination diagrams are thought to be relatively insensitive to moderate degrees of alteration. A-type granites generally do not exhibit evidence of being strongly differentiated, and within individual suites can show a transition from strongly alkaline varieties toward subalkaline compositions. Highly fractionated, felsic I- and S-type granites can have Ga/Al ratios and some major and trace element values which overlap those of typical A-type granites. A-type granites probably result mainly from partial melting of F and/or Cl enriched dry, granulitic residue remaining in the lower crust after extraction of an orogenic granite. Such melts are only moderately and locally modified by metasomatism or crystal fractionation. A-type melts occurred world-wide throughout geological time in a variety of tectonic settings and do not necessarily indicate an anorogenic or rifting environment.
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Jurassic granitoids in the northwestern Sanandaj Sirjan Zone: Evolving magmatism in response to the development of a Neo-Tethyan slab window
TL;DR: In this paper, the authors presented new in situ zircon U-Pb, whole-rock major and trace element, and Sr-Nd isotopic data for the Gorveh Plutonic Complex (GPC) of the northwestern SSZ in Iran.
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Geochronology and geochemistry of the Chuanwulu complex in the South Tianshan, western Xinjiang, NW China: Implications for petrogenesis and Phanerozoic continental growth
TL;DR: Based on LA-ICP-MS U-Pb zircon dating, the Chuanwulu complex is located in the eastern part of the Central Asian Orogenic Belt (CAOB), Xinjiang province, NW China as discussed by the authors.
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Geochemistry and Sr- and Nd-isotopic study on rare-metal-bearing granitic rocks, central Eastern Desert, Egypt
TL;DR: In this paper, three post-orogenic granitic plutons exposed in the Egyptian basement complex, namely Homr Akarem, Homrit Mukbid and Nuweibi were selected for geochemical and NdSr isotopic studies.
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Grenvillian magmatism in the northern Virginia Blue Ridge: Petrologic implications of episodic granitic magma production and the significance of postorogenic A-type charnockite
Richard P. Tollo,John N. Aleinikoff,Elizabeth A. Borduas,Alan P. Dickin,Robert H. McNutt,C. Mark Fanning +5 more
TL;DR: Grenvillian plutonic rocks in northern Virginia preserve evidence of episodic, mostly granitic magmatism that spanned more than 150 million years (my) of crustal reworking Crystallization ages determined by sensitive high resolution ion microprobe (SHRIMP) U-Pb isotopic analyses of zircon and monazite, combined with results from previous studies, define three periods of magmatic activity at 1183,1144,Ma (Magmatic Interval I), 1120,1111,Ma, and 1078,1028,
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Mesoproterozoic rift setting of SW Hainan: Evidence from the gneissic granites and metasedimentary rocks
TL;DR: In this article, the mesoproterozoic gneissic granites are monzogranites and granodiorites and crystallized at ∼1430 Ma.
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