Ce ANOMALIES OF ISLAND ARC IGNEOUS ROCKS

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A number of igneous rocks from Kuzuryu and Hakusan volcanic zones, anf Ogasawara islands have been analyzed for rare earth elements by ICP-MS, Some plutonic rocks from central Mongolia have been analyzed as well. Only some volcanic rocks from the Ogasawara islands show negative Ce anamalies. Almost all of them are rather poor in light rare earth elements. In contrast, none of the volcanic rocks from Kuzuryu and Hakusan volcanic zones show Ce anomaly. All of the rocks from the two volcanic zones are highly enriched in light rare earth elements. It seems that there appears no volanic rock with netative Ce anomaly in the matured island arc. The mongolian plutonic rocks show slight but clear Ce anomaly : this may imply that the parental crustal material of the plutonic rocks could be pre-matured island arc material.