Probable mineralogic control on the mantle metasomatic fluid composition beneath the northeast Japan arc

Journal Article · Mon Aug 01 00:00:00 EDT 1988 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(88)90182-2· OSTI ID:7164442

Ujike, Osamu ^[1]

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1. Toyama Univ., Gofuku (Japan)

Geochemical data are compiled for basalts from the Nasu zone at the trench side and the Chokai zone at the back-arc side, Northeast Japan arc. The source peridotites of these basalts above the subducted Pacific plate have large LIL (large ion lithophile)/HFS (high field strength) element ratios but are differentially enriched in individual LIL elements. The Chokai basalt sources are distinctly more enriched in K and Rb relative to Sr, Ce and Zr and lower in K/Rb than the Nasu tholeiite sources. A phlogopite component appears to have been important in metasomatic fluids related to the Chokai basalts which were generated at relatively great depths ({approximately} 140 km deep). On the other hand, fluids high in Sr and K/Rb and low in K/Sr and Rb/Sr, which are probably generated by dehydration of amphibole at a relatively shallower level ({approximately} 80 km deep), enrich the Nasu tholeiite sources. These metasomatic fluids derived ultimately from the subducted Pacific crust are, before added to the magma sources, probably trapped at the base of the mantle wedge descending by induced convection.

• OSTI ID: 7164442
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 52:8; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BASALT
CHEMICAL COMPOSITION
PETROGENESIS
JAPAN
EARTH MANTLE
GEOCHEMISTRY
GEOLOGIC HISTORY
METAMORPHISM
MINERALOGY
PETROLOGY
PLATE TECTONICS
POTASSIUM ISOTOPES
RUBIDIUM ISOTOPES
STRONTIUM ISOTOPES
SUBDUCTION ZONES
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
ASIA
CHEMISTRY
GEOLOGY
IGNEOUS ROCKS
ISOTOPES
ROCKS
TECTONICS
VOLCANIC ROCKS
580000* - Geosciences