Multistage melt/fluid-peridotite interactions in the refertilized lithospheric mantle beneath the North China Craton: Constraints from the Li-Sr-Nd isotopic disequilibrium between minerals of peridotite xenoliths

Yan Jie Tang, Hong Fu Zhang, Eizo Nakamura, Ji Feng Ying

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62 Citations (Scopus)

Abstract

Elemental and Li-Sr-Nd isotopic data of minerals in spinel hosted by Cenozoic basalts allow us to refine the existing models for Li isotopic fractionation in mantle and constrain the melt/fluid-peridotite interaction in the lithospheric mantle beneath the North China Craton.Highly elevated Li concentrations in cpx(upto 24pp)relative to coexisting opx and olivine(< 4 ppm)that the experienced metasomatism by mafic silicate meltsanor fluids.The mineral δ7Li vary greatly, with olivine(+0.7 to +5.4‰) being isotopically heavier than coexisting opx (-4.4 to -25.9‰) and cpx (-33 to -21.4‰) in most samples. The δ7Li in pyroxenes are considerably lower than the normal mantle values and show negative correlation with their Li abundances,likely due to recent Li ingress attended by diffusive fractionation of Li isotopes. Two exceptional samples have olivine δ7Li of -3.0 and -7.9‰,indicating the existence oflow δ7Li domains in the mantle,which could be transient and generated by meter-scale diffusion of Li during melt/fluid-peridotite interaction.The 143Nd/144Nd (0.5123-0.5139) and 87Sr/86Sr (0.7018-0.7062) in the pyroxenes also show a large variation, in which the cpx are apparently lower in 87Sr/86Sr and slightly higher in 143Nd/144Nd than coexisting opx, implying an intermineral Sr-Nd isotopic disequilibrium.This is observed more apparently in having low 87Sr/86Sr and high 143Nd/144Nd ratios than in those with high 87Sr/86Sr and low 143Nd/144Nd,suggesting that a relatively recent interaction existed between an ancient metasomatized lithospheric mantle and asthenospheric melt, which transformed the refractory with highly radiogenic Sr and unradiogenic Nd isotopic compositions to the fertile lherzolites with unradiogenic Sr and radiogenic Nd isotopic compositions.Therefore,we argue that the lithospheric mantle represented by the has been heterogeneously refertilized by multistage melt/fluid-peridotite interactions.

Original languageEnglish
Pages (from-to)845-861
Number of pages17
JournalContributions to Mineralogy and Petrology
Volume161
Issue number6
DOIs
Publication statusPublished - Jun 2011

Keywords

  • Lithium isotope
  • Lithospheric mantle
  • Melt/fluid-peridotite interaction
  • North China Craton
  • Peridotite xenoliths

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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