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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Citations
A Jurassic peraluminous leucogranite from Yiwulüshan, western Liaoning, North China craton: age, origin and tectonic significance
TL;DR: The Gangjia granite stock is a garnet-bearing muscovite leucogranitic body emplaced in Yiwulushan in Western Liaoning Province at the eastern segment of the Yanshan orogenic belt, North China craton as mentioned in this paper.
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Evolution of the Mesozoic Granites in the Xiong'ershan-Waifangshan Region,Western Henan Province,China,and Its Tectonic Implications
TL;DR: Based on the new data of isotopic ages and geochemical analyses, three types of Mesozoic granites have been identified for the Xiong'ershan-Waifangshan region in western Henan Province.
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Neoproterozoic rift and within-plate magmatism in the Yenisei Ridge: implications for the breakup of Rodinia
A. D. Nozhkin,O. M. Turkina,Tamara B. Bayanova,N.G. Berezhnaya,A.N. Larionov,A.A. Postnikov,A. V. Travin,Richard E. Ernst +7 more
TL;DR: Geological, petrological, geochemical, and isotope data from the Yenisei Ridge indicate three stages of rifting and attendant within-plate magmatism at 750, 700, and 670 Ma as mentioned in this paper.
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Petrogenesis of granitoids in the Wulan area: Magmatic activity and tectonic evolution in the North Qaidam, NW China
TL;DR: In this paper, the authors present geochemical and geochronologic data for six intrusive bodies and review regional data to evaluate their ages, petrogenesis and genetic relationships to other granitoids in the North Qaidam block.
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Multi-stage emplacement of alkaline and peralkaline syenite–granite suites in the Mongolian–Transbaikalian Belt, Russia: Evidence from U–Pb geochronology and whole rock geochemistry
TL;DR: In this paper, the authors presented new U-Pb zircon and titanite geochronological data from five plutonic complexes located in the central part of the Mongolian-Transbaikalian Belt (MTB).
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