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胶北地块粉子山群石榴云母片岩中石榴石变斑晶内包裹物迹线明显,保留了岩石形成过程中的多期变质变形信息。电子探针成分面扫描图显示石榴石成分环带明显,可分为核部、幔部和边部。石榴石中MgO、FeO、MnO和CaO含量变化特征表明其核部到边部温度先升高后降低,对应进变质及退变质过程。根据原位独居石Y元素成分面扫描图显示,部分独居石颗粒由核部到边部Y含量呈现逐渐降低趋势,说明测得的232.6±1.1Ma~229.5±3.7Ma的独居石U-Pb年龄,对应石榴石的进变质生长过程。结合1869±72Ma的锆石U-Pb年龄数据,可推断粉子山群石榴云母片岩至少经历了古元古代及三叠纪两期变质事件的改造。粉子山群石榴云母片岩卷入了苏鲁超高压变质带的俯冲碰撞造山事件。电子探针成分分析结果表明粉子山群石榴云母片岩中的石榴石属于铁铝榴石,反映出经受中级区域变质作用的特征。说明粉子山群石榴云母片岩虽然参与了三叠纪苏鲁超高压变质带的俯冲碰撞造山过程,但俯冲深度较浅。这可用大陆俯冲过程中上盘的俯冲剥蚀来解释,并可为陆-陆碰撞俯冲剥蚀模式提出的扬子板片在240~220Ma的深俯冲作用过程中拽动胶北地块向下俯冲又折返的运动过程提供佐证,但胶北地块是否经历了深俯冲超高压变质作用,还需要进一步验证。
The trace of garnet inclusions in the pomegranate mica schist of the Powderzishan group in the Jiaobei block is obvious, which retains the information of multi-stage metamorphism and deformation in the process of rock formation. Electron probe component surface scan shows garnet composition annulus obvious, can be divided into nuclear, mantle and edge. The characteristics of the contents of MgO, FeO, MnO and CaO in garnet show that the temperature at the core to the edge first increases and then decreases, corresponding to the metamorphism and retrogressive metamorphism. According to the in-situ monolith Y elemental surface scan images, the content of some monazite particles gradually decreases from the core to the edge, indicating that the measured monazite U-Pb age of 232.6 ± 1.1Ma ~ 229.5 ± 3.7Ma , Corresponding to the progress of garnet into the growth process. Combined with the zircon U-Pb ages of 1869 ± 72 Ma, it can be inferred that the pomegranate mica schist of the Zhenshan Group experienced at least the transformation of the metamorphic events of the Paleoproterozoic and Triassic phases. The Fenzi Mountain Group pomegranate mica schist involved in the subduction collision orogeny of the Sulu UHP metamorphic belt. Electron probe composition analysis results show that the garnet in the pomegranate mica schist of the Fenzishan Group is almandite, reflecting the characteristics of being subjected to metamorphism in the intermediate region. It shows that although the Picasso pumice mica schist participated in the subduction collision orogeny of the Triassic Sulu UHP metamorphic belt, the subduction depth is shallower. This can be explained by the subduction of the upper plate during the subduction process in the continental depression and can be used for the subduction and erosion pattern of the continental-continental collision. During the deep subduction process from 240 to 220 Ma, the Yangtze plate de- However, whether the Jiaobei block has undergone deep-subducted UHP metamorphism still needs further verification.