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通过野外和室内研究结果表明,石桥片麻岩是由沉积岩变质组成。在化学成分上,表现为高硅(SiO_2=75.22%~76.42%)、低铝(Al_2O_3=11.02%~12.29%)、富碱(Na_2O+K_2O=8.00%~8.68%)和贫钙(CaO=0.30%~0.82%),富集Rb、Ba、Th、U等大离子亲石元素,贫Nb、Ta、Zr、Hf、Ti等高场强元素,以及轻稀土相对富集(LREE/HREE=6.06~7.14)、铕负异常较明显(δEu=0.18~0.56)等。通过锆石成因类型及定年研究,获得超高压变质作用时间为254 Ma和退变质作用时间为217 Ma,老核(继承锆石)岩浆碎屑锆石是异地多时代(元古代—古生代),其寄主岩的原岩为沉积岩,时代不会早于古生代。
Field and laboratory studies show that Shiqiao gneiss is composed of sedimentary rocks. In the chemical composition, the contents of high silicon (SiO 2 = 75.22% ~ 76.42%), low aluminum (Al 2 O 3 = 11.02% ~ 12.29%), alkali rich (Na 2 O + K 2 O = 8.00% ~ 8.68% (LREE / HREE = 0.30% ~ 0.82%) enrichment of large ion lithophile elements such as Rb, Ba, Th and U and depletion of high field strength elements such as Nb, Ta, Zr, Hf and Ti, 6.06 ~ 7.14), europium negative anomaly more obvious (δEu = 0.18 ~ 0.56) and so on. According to the type and dating of zircons, the UHP metamorphism time is 254 Ma and retrogressive metamorphism time is 217 Ma. The magma detrital zircons from the old core (inherited zircon) are allochthonous (Proterozoic-Paleozoic) The host rocks of the original rock sedimentary rock, the age will not be earlier than the Paleozoic.