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大别-苏鲁造山带内部出露的浅变质岩与超高压变质围岩之间的成因关系是研究大陆板块俯冲过程中地壳拆离的重要对象之一.本文通过对大别山岳西县菖蒲地区产于超高压带内浅变质岩层中富硅凝灰岩进行40Ar/39Ar定年,得到与超高压变质火成岩原岩一致的两组新元古代年龄.一组Ar-Ar坪年龄为784.4±2.0Ma,等时线年龄为785.0±4.7Ma;另一组坪年龄为770.9±2.0Ma,等时年龄为769.5±3.1Ma.由于火山岩Ar-Ar同位素体系具有低的扩散封闭温度,这些新元古代Ar-Ar年龄的保存说明,浅变质火山岩未受到三叠纪超高压变质事件的明显影响,因此在扬子板块向华北板块俯冲过程中并未发生深俯冲,而是大陆板块俯冲过程中盖层与基底之间发生拆离后被刮削下来的构造残片.浅变质岩与超高压变质岩之间的共存指示,深俯冲岩片折返过程能够导致构造混杂现象.
The genetic relationship between the superdeformable rocks and the metamorphic rocks exposed in the Dabie-Sulu orogenic belt is one of the important objects for studying the crustal detachment during the subduction of the continental plate.Based on the analysis of the relationship between the iris area Produced in the ultrahigh-pressure zone within the metamorphic rock strata rich in silicon-rich tuff 40Ar / 39Ar dating, obtained with the ultrahigh-pressure metamorphic igneous rock metamorphic two sets of Neoproterozoic age.A group Ar-Ar Ping age of 784.4 ± 2.0Ma, isochron The line age is 785.0 ± 4.7Ma and the other is 770.9 ± 2.0Ma with an isochron age of 769.5 ± 3.1Ma. Because of the low diffusion sealing temperature of the Ar-Ar isotopic system of volcanic rocks, these Neoproterozoic Ar-Ar ages , The shallow metamorphic volcanic rocks were not significantly affected by the Triassic UHP metamorphism. Therefore, deep subduction did not occur during the subduction of the Yangtze Plate to the North China Plate, but rather occurred between the cap layer and the basement during the subduction of the continental plate The tectonic debris scraped off after detachment.The coexistence of superficial metamorphic rocks and ultrahigh-pressure metamorphic rocks indicates that the tectonic remnants of the deep-subducted rock fragments can lead to the confounding of structures.