Transformation of Subcontinental Lithospheric Mantle through Peridotite-Melt Reaction: Evidence from a Highly Fertile Mantle Xenolith from the North China Craton
Transformation of Subcontinental Lithospheric Mantle through Peridotite-Melt Reaction: Evidence from a Highly Fertile Mantle Xenolith from the North China Craton
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DOI：
10.2747/0020-6814.49.7.658
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发表时间：
2007-07
影响因子：
2.6
通讯作者：
Hong‐fu Zhang;E. Nakamura;M. Sun;K. Kobayashi;Jin Zhang;Jifeng Ying;Yanjie Tang;Li‐feng Niu
中科院分区：
文献类型：
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作者：
Hong‐fu Zhang;E. Nakamura;M. Sun;K. Kobayashi;Jin Zhang;Jifeng Ying;Yanjie Tang;Li‐feng Niu
山东上白垩统大西庄玄武岩中的一个高丰度地幔捕虏体为华北克拉通东部中生代岩石圈地幔中玄武质熔体与难熔橄榄岩之间的反应提供了岩石学证据。捕虏体被划分为二辉橄榄岩核、剪切的韦尔岩地幔和反应物边缘。二辉橄榄岩具有中等颗粒结构，含有橄榄石、斜方辉石、单斜辉石和尖晶石，Mg #值较低（≤ 87）。这是全球范围内金伯利岩和玄武岩中地幔捕虏体的最低值，但与华北克拉通东部邻区的低Mg尖晶石二辉橄榄岩相近。韦尔岩地幔显示出清晰的方向性和叶理组成的橄榄石和单斜辉石。反应物边缘显示细颗粒橄榄石，单斜辉石，尖晶石的合晶结构，其特征在于轻稀土富集模式。剪切地幔和反应物边缘缺乏斜方辉石。明显的分带和系统的核心-边缘变化的主要和微量元素的组成矿物证明通过熔体橄榄岩反应的捕虏体中的再施肥的发生。这一反应可能是由高Mg #原岩生成低Mg #橄榄岩的原因，也可能是陆下岩石圈地幔由古生代耐火地幔向晚中生代富氧地幔转变的重要机制。
A highly fertile mantle xenolith entrained in the Upper Cretaceous Daxizhuang basalt, Shandong Province, China provides petrological evidence for reaction between basaltic melt and refractory peridotite in Mesozoic lithospheric mantle beneath the eastern North China craton. The xenolith is zoned with a lherzolite core, a sheared wehrlite mantle, and a reactant rim. The lherzolite has a medium-grained granular texture and contains olivine, orthopyroxene, clinopyroxene, and spinel with low Mg# values (≤87). This is the lowest value observed globally in mantle xenoliths entrained in both kimberlites and basalts from old cratons, but is close to low-Mg# spinel lherzolites entrained in adjacent region of the eastern North China craton. The wehrlite mantle shows clear orientation and foliation of constituent olivine and clinopyroxene. The reactant rim displays a symplectite texture of fine-grained olivine, clinopyroxene, and spinel, and is characterized by LREE-enriched patterns. Orthopyroxene is lacking from the sheared mantle and reactant rim. Clear zoning and systematic core-rim variations in major and trace elements of the constituent minerals demonstrate the occurrence of the refertilization through the melt-peridotite reaction in the xenolith. This reaction may have produced the low-Mg# peridotite from a high-Mg# protolith and could be an important mechanism for the change of the subcontinental lithospheric mantle from a Paleozoic refractory mantle to a Late Mesozoic fertile mantle.