Eu geochemistry in magmatic rocks of continental marginal volcanic belts

Abstract

The example of eastern Russia is employed to analyze the influence of diverse factors on the development of negative Eu anomalies in magmatic rocks at continental marginal volcanic belts. A strong correlation is identified between the relative value of Eu minima and the degree of Fe oxidation, Fe/(Fe+Mg) of mafic minerals, and an increase in the Eu minimum from basic to acid rocks. It is demonstrated that the value of the Eu minimum hardly depends on either the crystallization depth of the rocks and/or their alkalinity. Within individual tectono-stratigraphic zones, the value of Eu anomalies is independent of the age of the rocks, their affiliation with certain associations, and the basement structure of the volcanic zone. Rocks with clearly pronounced negative Eu anomalies belong exclusively to the ilmenite series that are formed under reduced conditions. The rocks of the magnetite series, which are formed under oxidized conditions, contain trivalent Eu, which behaves analogously to other REE.