Episodes

Vol. 28 No.3 September 2005

Journal of International Geoscience

Published by the International Union of Geological sciences

by Zhaochong Zhang1,2, Jingwen Mao3, Fusheng Wang1, Yanli Hao1 and John J. Mahoney4

Mantle plume activity and melting conditions: Evidence from olivines in picritic-komatiitic rocks from the Emeishan Large Igneous Province, southwestern China

1 Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China. E-mail: zhangzhaochong@sohu.com
2 China University of Geosciences, Beijing, 100083, China.
3 Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, 100037, China.
4 School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822, USA.

Abstract

Olivine phenocryst compositions and whole-rock chemical compositions are used to identify primitive picrite basalts from the early part of flood basalt successions in the western part of the Emeishan large igneous province (ELIP), southwestern China. The Fo contents of olivine phenocrysts of komatiites with MgO ~21.79 wt% range from 85.2% to 91.4%. The composition of unerupted parental melts is calculated from the compositions of the most Fo-rich olivine phenocrysts. These melts had ~22 wt% MgO, and originated in mantle with a potential temperature of ~1600ˇăC and at about 4.2 GPa pressure, supporting the conclusion that the generation of ELIP can be attributed to melting of a plume head beginning at ~138 km depth.

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