华北地幔橄榄岩捕虏体的矿物组成特征与成因意义

Mineral composition characteristics and genetic significances of mantle peridotite xenoliths in the North China Craton

地幔橄榄岩捕虏体是起源于地幔的岩浆在上升过程中携带的岩石圈地幔的碎块,因此是岩石圈地幔的直接样品,具有地球深部的探针之称,为岩石圈地幔特征与演化研究提供了关键信息。本文综述了华北克拉通地幔橄榄岩捕虏体的岩石类型、矿物组成特征与成因意义,并指出熔体改造(熔-岩反应)在华北东部岩石圈地幔从克拉通型转变为大洋型的过程中所起的重要作用;华北中部和西北部边缘地区既有大量古老、难熔的残留地幔,也有相对年轻的、具有大洋型特征的饱满地幔,反映了熔体对古老岩石圈地幔长期改造的结果。参与地幔改造作用的熔体有多个来源,包括再循环的古老地壳、蚀变洋壳和大洋沉积物等。地幔改造作用发生的时间、期次及其对岩石圈地幔的影响机制有待进一步研究。

Mantle peridotite xenoliths are fragments of the lithospheric mantle which were carried by the mantle-derived magmas in their ascent process.Therefore,they are direct samples of the lithospheric mantle and are known as probes for the deep Earth.They can provide key information for studying the characteristics and evolution of the lithospheric mantle.This article summarizes the rock types,mineral composition characteristics,and genetic significances of mantle peridotite xenoliths in the North China Craton,and points out that the mantle modification by melts(melt-rock reaction)played an important role in the modification process of lithospheric mantle beneath the eastern part of the North China Craton from typically cratonic type to oceanic type.There are a large amount of ancient and refractory residual mantle,as well as relatively young and oceanic-type fertile mantle in the central part and northwestern margin of North China Craton,reflecting the long-term modification of ancient lithospheric mantle by various melts.The melts involved in the mantle modification process were derived from multiple sources including the recycled ancient crust,altered oceanic crust,and oceanic sediments.Further researches should be focused on the timing and stages of the mantle modification and its influencing mechanisms on the lithospheric mantle beneath the North China Craton.