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目前国内关于麻粒岩中锆石的成因问题尚有争议,部分人认为变质岩中磨圆度较好的锆石属于熔蚀成因。笔者经过野外观察及室内分析鉴定,认为沙厂麻粒岩中的锆石是经搬运、磨蚀、沉积而形成,推测该区层状麻粒岩成因也为沉积形成。沙厂位于北京东北85km 的密云县境内,区内主要出露地层为太古界密云群沙厂组古老变质岩系,变质年龄为24亿年(表1)。区内构造复杂,褶皱断裂均较发育,受区域混合岩化作用和退变质作用的影响,岩石类型主要由各种斜长片麻岩、变粒岩、麻粒岩、角闪岩及磁铁石英岩组成。
At present, the cause of formation of zircon in granulite is still controversial in China. Some people think that zircons with good roundness in metamorphic rocks belong to the cause of erosion. After field observation and laboratory analysis, the authors believe that the zircons in the sandstone granulite were formed by transportation, erosion and sedimentation, suggesting that the stratiform granulite also formed in this area. The Sha Sha Factory is located in Miyun County, 85km northeast of Beijing. The main exposed formation in this area is the ancient metamorphic rocks of the Miyun and Qushachang formations in the Archean, with a metamorphic age of 2.4 billion years (Table 1). Due to the complex structure and fold-faults in the area, the rock types are mainly composed of various plagioclase gneiss, granulite, granulite, amphibolite and magnetite by the mixed and petrified regional metamorphism and retrogressive metamorphism. Rock composition.