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- Title
Comparison of rhyolites from continental rift, continental arc and oceanic island arc: Implication for the mechanism of silicic magma generation.
- Authors
Ayalew, Dereje; Ishiwatari, Akira
- Abstract
We discuss the chemical compositions of rhyolites from three distinct tectonic settings: (i) the continental rift from Ethiopia (both Oligocene-Miocene and Quaternary rhyolites); (ii) the early Miocene continental arc of Japan (the Mt Wasso rhyolites related to the rifting of the Japan Sea); and (iii) the oceanic Izu-Bonin Island Arc. The comparison reveals that the oceanic island arc rhyolites have high contents of CaO, AlO, and Sr, and extremely low abundance of trace elements including KO. In contrast, the Ethiopian continental rift rhyolites are characterized by low contents of CaO, AlO, and Sr, and high contents of KO, and are enriched in the whole range of trace elements. The continental arc Mt Wasso rhyolites are apparently low in Nb content, although they display similar chemical trends to those of the Ethiopian rhyolites. This obvious difference in the chemical signatures of the rhyolites from the three tectonic settings is the consequence of their derivation from different sources. The implication of this result is that fractional crystallization processes were dominant in the rift-related rhyolites both from continental rift and continental arc regardless of the prevailing tectonic setting and the nature of the crust (age, thickness, composition), whereas the oceanic island arc rhyolites may form through partial melting of young, mafic crust.
- Subjects
ETHIOPIA; JAPAN; CHEMICAL reactions; RHYOLITE; RIFTS (Geology); TRACE elements; STRUCTURAL geology
- Publication
Island Arc, 2011, Vol 20, Issue 1, p78
- ISSN
1038-4871
- Publication type
Article
- DOI
10.1111/j.1440-1738.2010.00746.x