华北克拉通之下古老岩石圈地幔的锂同位素组成异常。

Abnormal lithium isotope composition from the ancient lithospheric mantle beneath the North China Craton.

作者信息

Tang Yan-Jie, Zhang Hong-Fu, Deloule Etienne, Su Ben-Xun, Ying Ji-Feng, Santosh M, Xiao Yan

机构信息

State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of SciencesP.O. Box 9825, Beijing 100029, China.

1] State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of SciencesP.O. Box 9825, Beijing 100029, China [2] State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China.

出版信息

Sci Rep. 2014 Mar 4;4:4274. doi: 10.1038/srep04274.

DOI:10.1038/srep04274

PMID:24589693

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC3940973/

Abstract

Lithium elemental and isotopic compositions of olivines in peridotite xenoliths from Hebi in the North China Craton provide direct evidence for the highly variable δ(7)Li in Archean lithospheric mantle. The δ(7)Li in the cores of olivines from the Hebi high-Mg# peridotites (Fo > 91) show extreme variation from -27 to +21, in marked deviation from the δ(7)Li range of fresh MORB (+1.6 to +5.6) although the Li abundances of the olivines are within the range of normal mantle (1-2 ppm). The Li abundances and δ(7)Li characteristics of the Hebi olivines could not have been produced by recent diffusive-driven isotopic fractionation of Li and therefore the δ(7)Li in the cores of these olivines record the isotopic signature of the subcontinental lithospheric mantle. Our data demonstrate that abnormal δ(7)Li may be preserved in the ancient lithospheric mantle as observed in our study from the central North China Craton, which suggest that the subcontinental lithospheric mantle has experienced modification of fluid/melt derived from recycled oceanic crust.

摘要

华北克拉通鹤壁地区橄榄岩捕虏体中橄榄石的锂元素和同位素组成，为太古代岩石圈地幔中δ(7)Li的高度变化提供了直接证据。鹤壁高镁#橄榄岩（Fo>91）中橄榄石核心的δ(7)Li显示出从-27到+21的极端变化，与新鲜洋中脊玄武岩（MORB）的δ(7)Li范围（+1.6至+5.6）有明显偏差，尽管橄榄石的锂丰度在正常地幔范围内（1-2 ppm）。鹤壁橄榄石的锂丰度和δ(7)Li特征不可能是由近期锂的扩散驱动同位素分馏产生的，因此这些橄榄石核心中的δ(7)Li记录了大陆岩石圈地幔的同位素特征。我们的数据表明，正如我们在华北克拉通中部的研究中所观察到的，异常的δ(7)Li可能保存在古老的岩石圈地幔中，这表明大陆岩石圈地幔经历了来自再循环洋壳的流体/熔体的改造。