华北克拉通北缘地处古亚洲洋板片向华北板块俯冲的汇聚部位。近年来对深源捕虏体的研究表明，华北北缘的深部岩石圈受到古亚洲洋俯冲交代作用的显著改造。然而，关于交代介质的来源、性质以及交代作用发生的时间等仍存在较大争议。这些问题也是深入理解俯冲作用对深部岩石圈改造机制的重点和难点所在。申请者近来在华北北缘阳原地区新生代玄武岩中发现一些深源石榴单斜辉石岩捕虏体。初步的矿物学研究表明这些石榴单斜辉石岩具交代成因特征，是研究深部岩石圈交代作用的理想对象。鉴于此，本项目拟对其展开详细的矿物学、岩石学、元素及Sr-Nd-Hf-Mg-O同位素地球化学和年代学等多方面综合研究，明确阳原石榴单斜辉石岩的来源深度、探究交代作用发生的时间及机制，从而揭示阳原地区的深部岩石圈是否受到古亚洲洋俯冲作用的影响，限定古亚洲洋的俯冲时限和影响范围。在此基础上，全面认识俯冲相关的交代作用对华北北缘深部岩石圈改造的机制和规律。

The northern North China Craton (NCC)is located where Paleo-Asian ocean slab (PAOS) subducted toward the NCC. In recent years, studies on deep-seated xenoliths have shown that deep lithosphere in northern NCC has been significantly modified by the subduction-related metasomatism of the PAOS. However, there is still considerable controversy about the source, nature of the metasomatic agent and the time of metasomatism. These are also the key points to understanding the modification of deep lithosphere by subduction-related metasomatism. The applicant recently found some garnet clinopyroxenite xenoliths with hydrous minerals in Cenozoic Yangyuan basalts, northern NCC. Preliminary mineralogical studies have shown that these garnet clinopyroxenite xenoliths have characteristics of metasomatism. Therefore, they are excellent research object for studying metasomatism in deep lithosphere. We will carry out systematic studies on mineralogy, petrology, Sr-Nd-Hf-Mg-O multi-isotope and elemental geochemistry and chronology to clarify the source depth of these xenoliths and figure out the time and mechanism of metasomatism. This research will further reveal whether the deep lithosphere in Yangyuan area was modified by the subduction of the PAOS, and limit the subduction time and influence range of the PAOS. On this basis, it contributes to a comprehensive understanding of the modification of deep lithosphere in northern NCC by subduction-related metasomatism.