ORIGIN OF CRATONIC PERIDOTITE AND KOMATIITE - EVIDENCE FOR MELTING INTHE WET ARCHEAN MANTLE

Citation
E. Ohtani et al., ORIGIN OF CRATONIC PERIDOTITE AND KOMATIITE - EVIDENCE FOR MELTING INTHE WET ARCHEAN MANTLE, Proceedings of the Japan Academy. Series B Physical and biological sciences, 72(6), 1996, pp. 113-117
Citations number
17
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Multidisciplinary Sciences",Biology
ISSN journal
0386-2208
Volume
72
Issue
6
Year of publication
1996
Pages
113 - 117
Database
ISI
SICI code
0386-2208(1996)72:6<113:OOCPAK>2.0.ZU;2-3
Abstract
We have conducted melting experiments of pyrolite containing 1 and 2 w t. % of water at 6.5 GPa by a multianvil high pressure apparatus. We o bserved melting at temperatures above 1550 degrees C and 1700 degrees C for pyrolite + 2%H2O and pyrolite + 1%H2O respectively at 6.5 GPa. A small amount of water reduces the solidus temperature by 250-100 degr ees C. Another important observation is expansion of the stability fie ld of orthopyroxene above the solidus, and reduction of the stability field of olivine + liquid. The present observation of expansion of the orthopyroxene stability held above the solidus at 6.5 GPa implies tha t the harzburgite residue can be formed by partial melting of the prim itive mantle under the hydrous conditions at the depth of around 200 k m. Hydrous melting is a key process to fill the missing link between t he cratonic peridotite and komatiite; i.e., cratonic peridotite was fo rmed as a residue of the komatiite extraction in a wet Archean mantle.