Magmatic zonation of the Kurile Island Arc

Conference · Fri Jun 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6313866

Tsvetkov, A ^[1]

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1. Institute of Ore Deposit Geology, Petrography, Mineralogy and Geochemistry, Moscow (USSR)

During the past decade Soviet r/v Volcanolog made six cruises in the Kurile Island arc conducting multipurpose geological-geophysical investigations practically on each of its 86 submarine volcanoes. The obtained results enabled us to decipher spatial-structural distribution of the Kurile Quaternary volcanoes and compositional patterns of their lavas. Correlating available information on submarine and onland volcanics one can notice that concentrations of LIL and HFS elements just as Mg, Ni, Cr quite distinctively increase from volcanic front toward the arc's rear while concentrations of Fe and V, just as {sup 87}Sr/{sup 86}Sr and {sup 143}Nd/{sup 144}Nd ratios distinctively decrease. Substantial difference is also reported for modal compositions of lavas and their phenocryst-microlith assemblages. Typical of the intermediate-acid rocks from the frontal zone are two-pyroxene assemblages while those from the back-arc zone are amphybole-biotite, the latter two minerals typical even to some basalts and basaltic andesites. Chemical differences between magmas generated in the two structural zones of the Kuriles are stressed by composition of inclusions. Volcanic front lavas are practically free of ultramafic nodules while in the back-arc zone they are fairly common (Chirinkotan, Brouton Islands, etc). Gabbroic and metamorphic inclusions in the frontal zone like lavas do not contain any H{sub 2}O-bearing phases while those of the back-arc zone are usually amphibole-mica bearing. The available data show that compositional dissimilarity of Quaternary lavas across the Kurile volcanic chain do not depend on the thickness of the crust but rather are related to chemical differences of magmatic sources and melting conditions at depths.

• OSTI ID: 6313866
• Report Number(s): CONF-900702--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:6
• Country of Publication: United States
• Language: English

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