Mineralogical Characteristics of Qingshan Granitic Pluton in North Qilian Orogenic Belt and Their Constraints on Petrogenesis
Wang Nan
Wu Cailai
Lei Min
Chen Hongjie
Li Mingze
Abstract：The North Qilian orogenic belt underwent a complete Wilson Cycle through opening and closing of an ocean basin. Deepening the research of granite within can provide pivotal clues to reconstruct the subduction-accretion/collision orogenic framework.On the basis of systematic petrological and petrographical research,this paper conducts electron microprobe analy-sis on the main rock-forming minerals,aiming to determine the physicochemical conditions during rock formation and provide further constraints on the petrogenesis and tectonic setting.Results show that Qingshan monzogranite is mainly composed of K-feldspar(orthoclase),plagioclase(andesine-oligoclase),biotite(magnesian biotite),amphibole(magnesiohornblende)and quartz.Zircon saturation thermometer shows that the average temperature of initial magma is 750 ℃.Meanwhile,mineral chemistry analysis reveals that the average crystallization temperature for biotite is 647 ℃ and the oxygen fugacity during the rock formation is —15,corresponding to solidification depth of 6.73 km and solidification pressure of 1.85×108Pa.The data in this paper indicates that Qingshan monzogranite is I-type subsolvus granite,with the features of crust-mantle mixed source. Thus,it is proposed that Qingshan monzogranite belongs to calc-alkaline granite and produced under water-bearing condition.
Keywords：geothermo barometerpetrogenesismineralogical chemistrymonzograniteNorth Qilian orogenic beltpetrology
Publication Date：2018-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 1253-1265 )