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Mantle and Recycled Oceanic Crustal Components in Mantle Xenoliths From Northeastern China and their Mantle Sources
Author(s) -
Guo Peng,
Ionov Dmitri A.,
Xu WenLiang,
Wang ChunGuang,
Luan JinPeng
Publication year - 2020
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb018232
Subject(s) - geology , peridotite , geochemistry , xenolith , craton , mantle (geology) , olivine , subduction , lithosphere , oceanic crust , carbonatite , asthenosphere , transition zone , metasomatism , tectonics , paleontology
Abstract The subduction of the Paleo‐Pacific plate is widely credited for the destruction of the eastern North China Craton. However, how the Pacific plate subduction has affected the off‐craton lithospheric mantle in northeastern China is less clear, as few studies have focused on the lithospheric mantle‐derived xenoliths in that region. We report petrography, mineral and rock chemistry, and in situ isotopic compositions of Sr in clinopyroxene and O in olivine for 20 peridotite and 11 pyroxenite xenoliths hosted by the Cenozoic volcanic rocks at Jiaohe and Shuangliao localities. The peridotites include lherzolites, harzburgites, and a wehrlite, many are metasomatized. Group 1 garnet pyroxenites have high Al 2 O 3 , Ni, and Mg#; positive Eu and Sr anomalies; and olivine δ 18 O values of 4.8–5.1‰, which we attribute to recycling of oceanic crustal components to the asthenosphere and their reactions with host peridotites. Groups 2 and 3 pyroxenites are garnet‐free and contain peridotite‐like pyroxenes; we argue that they were formed by reactions of lithospheric peridotites with evolved melts derived from recycled oceanic crust. In addition, one pyroxenite contains orthopyroxene surrounded by fine‐grained olivine and clinopyroxene, while another pyroxenite and the wehrlite contain zoned clinopyroxene with gradual increases in Na 2 O, (La/Yb) N , Sr, and 87 Sr/ 86 Sr ratios and decreases in Ti/Eu from core to rim. These characteristics record infiltration of a carbonatite melt shortly before the transport of the xenoliths. The inferred carbonatite melt has 87 Sr/ 86 Sr ≥ 0.70415 and mantle‐like olivine δ 18 O and originated from carbonated asthenosphere. Our results, together with previous studies on the host basalts, suggest that subducted crustal materials were initially transported to the asthenosphere beneath northeastern China to produce carbonate‐bearing domains. Upwelling of the carbonated asthenosphere produced carbonatite melts that migrated upward and metasomatized the overlying lithospheric mantle.