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多期变质事件的识别,可为复合造山带变质演化的研究提供重要证据.松树沟基性岩记录了早古生代的两期变质事件,为研究北秦岭的演化提供了一个“窗口”.野外地质及岩相学研究表明,松树沟榴闪岩呈透镜状分布,从透镜体核部到边缘,退变质程度逐渐增强,逐渐向外围的斜长角闪片岩过渡.在强退变质带中的斜长角闪片岩和含石榴石残余的斜长角闪片岩中,角闪石具有明显的生长环带,核部为阳起石,边缘为镁角闪石.这表明,松树沟的变基性岩从麻粒岩相或角闪岩相退变到绿片岩相后又遭受了后期低角闪岩相变质.锆石U-Pb年代学研究也揭示了变基性岩记录了北秦岭早古生代的两期变质作用:在经历484±4Ma最高变质级别为麻粒岩相的变质作用后,退变至绿片岩相;在418±5Ma又受到一期变质热作用,使基性岩中的角闪石发生了环带的增生.
The identification of multi-stage metamorphic events can provide important evidence for the study of the metamorphic evolution of the orogenic belt.The Songgou basic rock records two metamorphic events of the Early Paleozoic and provides a “window ” for studying the evolution of the North Qinling Mountains. Field geology and petrography studies show that the Songshugou granulite is lenticularly distributed, and the degree of retrograde metamorphism gradually increases from the nucleus to the periphery of the lens body and gradually transitions to the peripheral plagioclase feldspathic rocks. In the strongly retrogressive zone Of the plagioclase amphibole and garnet-containing plagioclase amphibole, amphibole has a clear growth zone, the nucleus is the actinolite, the edge of the amphibole .This shows that the changes in the pine gully The mafic rocks have suffered the late-amphibolite facies metamorphism from the granulite facies or amphibolite facies to the greenschist facies, and the zircon U-Pb chronology also reveals that the metamorphic rocks record the North Qinling The two metamorphism of Early Paleozoic degenerated into greenschist facies after experiencing the metamorphism of the granulite facies at the highest metamorphism level of 484 ± 4Ma and the first metamorphism at 418 ± 5Ma. Hornblende occurred in the ring zone hyperplasia.