A detailed study on petrology and mineral chemistry of 12 mantle xenoliths from Late Cretaceous basaltic lava flows at Daxizhuang has been conducted to constrain the nature and secular evolution of the Mesozoic lithospheric mantle beneath the eastern North China Craton (NCC). The Daxizhuang mantle xenoliths are mainly anhydrous spinel lherzolite, with subordinate olivine websterite and rare spinel wehrlite. Based on petrographic and geochemical characteristics, the Daxizhuang spinel lherzolite can be subdivided into two groups. Group 1 lherzolite has olivine with Fo contents from 89.4 to 90.6 and LREE-depleted through spoon-shaped to LREE-enriched REE (rare earth element) patterns in clinopyroxene grains, reflecting variable degrees of partial melt extraction (up to 18%) overprinted by later incipient metasomatism. In contrast, Group 2 lherzolite is strongly metasomatized and enriched in iron, as evidenced by relatively lower Fo contents of olivine (84.9 to 88.2) than that from the Group 1 lherzolite and convex-upward trace element patterns in clinopyroxene grains. The Daxizhuang olivine websterite and spinel wehrlite are rich in Fe, Al and low Mg# in olivine and pyroxenes, and slight Ti-enrichment in spinel. Numerical modeling of the Mg# shows that the Daxizhuang olivine websterite and wehrlite may have resulted from the reaction between host residual lherzolite and evolved, silicate melts at high melt/rock ratios. The result of this study indicates that the lithospheric mantle beneath Daxizhuang underwent multiple metasomatism through asthenosphere-lithosphere interaction, which plays an important role in the transformation of the lithospheric mantle of the NCC at least during Late Cretaceous time.

中文翻译：

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软流圈熔体对岩石圈地幔的多阶段交代作用——来自华北克拉通东部大溪庄地幔包体的证据

对来自大西庄晚白垩世玄武岩熔岩流的 12 块地幔包体的岩石学和矿物化学进行了详细研究，以限制华北克拉通东部 (NCC) 下中生代岩石圈地幔的性质和长期演化。大西庄地幔包体主要为无水尖晶石锂辉石，次要橄榄石韦氏橄榄石和稀有尖晶石橄榄石。根据岩石学和地球化学特征，大溪庄尖晶石二辉石可细分为两组。组 1 橄榄石具有橄榄石，其 Fo 含量为 89.4 至 90.6，LREE 通过勺形耗尽到 LREE 富集的 REE（稀土元素）图案在斜辉石颗粒中，反映了不同程度的部分熔体提取（高达 18%）后期初期交代。相比之下，橄榄石的 Fo 含量 (84.9 至 88.2) 比 1 组红长石的 Fo 含量相对较低，并且单斜辉石颗粒中的微量元素图案向上凸出，这证明了第 2 族的二辉石强烈交代并富含铁。大溪庄橄榄石橄榄石和尖晶石橄榄石富含Fe、Al，橄榄石和辉石中Mg # 含量低，尖晶石中Ti 微量富集。Mg # 的数值模拟表明，大溪庄橄榄石韦氏橄榄石和橄榄石可能是由主体残留的二长方岩与高熔体/岩石比的演化出的硅酸盐熔体之间的反应产生的。研究结果表明，大西庄下方岩石圈地幔通过软流圈-岩石圈相互作用经历了多次交代作用，