The origin of geochemical variations in mariana lavas: A general model for petrogenesis in intra-oceanic island arcs?

Abstract

Major and trace element data are presented for a suite of lavas and gabbroic xenoliths from the northern Mariana Islands in the west Pacific.Fractional crystallization of a gabbroic mineral assemblage, similar to that observed in the xenoliths, appears to be the predominant control on major and trace element variation within the lavas. Mixing calculations indicate that this 'extract' has an average composition of PLAG:CPX:MAG:OLIV =60:25:10:5. Amphibole is not thought to be an important component of the fractionating assemblage.Consideration of REE data, in particular the pronounced negative correlation between Eu/Eu* and silica, allows the identification of a 'parental' magma composition, r..