Helium and argon isotopes of the Tertiary basic igneous rocks from Shandong Peninsula and implications for the magma origin

Hua Yun Tang, Jian Ping Zheng*, Hong Han Chen, Xian Ren Ye

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Helium (He) and Argon (Ar) isotopic compositions of the Tertiary basic igneous rocks were determined by the high temperature melting extraction method. The selected samples for the studies included alkaline basalts and diabases from the Jiyang basin, and the surrounding Shanwang and Qixia outcrops in the Shandong Peninsula, eastern China. The results show that the Paleogene basalts and diabases from the Jiyang basin yielded a wide range of 4He abundance of (73.70-804.16)×10-8 cm3 STP·g-1, with 3He/4He ratios of 0.374-2.959 Ra, which was lower than the MORB but evidently higher than the continental crust value. The Neogene alkaline basalts from the Jiyang basin, Shanwang and Qixia outcrops have variable 4He abundances ((42.34-286.72)×10-8 cm3 STP g-1), and "continental crust-like" 3He/4He ratios (0.013-0.074 Ra). All of them contain atmospheric-like 40Ar/36Ar ratio (395.4-1312.7), reflecting the mantle sources with air components. Their low 3He/4He ratios are interpreted as the enrichment of the radiogenic 4He mainly inherited from the mantle. He and Ar systematics show the mixing of MORB-type, air and a 4He enriched member in the mantle source, suggesting that these igneous rocks originated from the depleted asthenospheric mantle mixed with an EMI component. Therefore, the present He and Ar isotopes do not support the viewpoints that the Cenozoic igneous rocks of Eastern North China were the products of mantle plume(s) activities.

Original languageEnglish
Pages (from-to)1021-1032
Number of pages12
JournalScience in China, Series D: Earth Sciences
Volume50
Issue number7
DOIs
Publication statusPublished - Jun 2007
Externally publishedYes

Keywords

  • Asthenosphere
  • He and Ar isotopes
  • Mantle sources
  • Shandong Peninsula
  • Tertiary basic igneous rocks

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