Coexistence of the moderately refractory and fertile mantle beneath the eastern Central Asian Orogenic Belt

Shaokui Pan, Jianping Zheng*, Linlin Chu, W. L. Griffin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

Relative to the North China Craton, the subcontinental lithospheric mantle (SCLM) beneath the Central Asian Orogenic Belt is little known. Mantle-derived peridotite xenoliths from the Cenozoic basalts in the Xilinhot region, Inner Mongolia, provide samples of the lithospheric mantle beneath the eastern part of the belt. The xenoliths are predominantly lherzolites with minor harzburgites, and can be subdivided into three groups, based on the REE patterns of clinopyroxenes. Group 1 peridotites (LREE-enriched), with low modal Cpx (3-7%), high Mg # in olivine (>90.6) and Cr # in spinel (>43.8), low whole-rock CaO+Al 2O 3 contents (1.62-3.22wt.%) and estimated temperatures of 1043-1126°C, represent moderately refractory SCLM that has experienced carbonatite-related metasomatism. Group 2 peridotites (LREE-depleted), with high modal Cpx (9-13%), low Mg # in olivine (<90.6) and Cr # in spinel (<20.0), high whole-rock CaO+Al 2O 3 contents (4.93-6.37wt.%) and estimated temperatures of 814-970°C, show affinity with Phanerozoic fertile SCLM that has undergone silicate-related metasomatism. Group 3 peridotites (convex-upward REE patterns), show wide ranges of olivine-Mg # (88.4-90.6), spinel-Cr # (11.5-47.6), and modal Cpx (3-14%) that overlap Groups 1 and 2. Their spinels have high TiO 2 contents (>0.41wt.%), implying involvement of reactions between melt and peridotites. The estimated temperatures of Group 3 (1033-1156°C) are similar to those of Group 1. We suggest that the pre-existing moderately refractory lithospheric mantle (i.e., Group 1) beneath the eastern part of the Central Asian Orogenic Belt was strongly penetrated by upwelling asthenospheric material, and the cooling of this material produced fertile lithospheric mantle (i.e., Group 2). The present lithospheric mantle of this area consists of interspersed volumes of younger fertile and older more refractory lithosphere, with the fertile type dominating the shallower levels of the mantle.

Original languageEnglish
Pages (from-to)176-189
Number of pages14
JournalGondwana Research
Volume23
Issue number1
DOIs
Publication statusPublished - Jan 2013

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