The Esmeralda Submarine Volcano at the Mariana Island Arc, and Some Features of the Constituent Rocks

This paper summarizes available original data and material from the literature concerning our geological and geophysical knowledge of the Esmeralda submarine volcano situated at the Mariana island arc. An advanced study of the rocks dredged during the 4th and 5th cruises of the Vulkanolog research vessel yielded new information on silicate and trace element compositions of the rocks that compose the volcano. It was found that the volcanic edifice under study is composed of five rock types: basalts, basaltic andesites, dacites, gabbro, and basanites. For the first time we recovered samples of dacite and basanite that provide evidence of a broader petrochemical diversity of the Esmeralda submarine volcano compared to what has been thought previously. All dredged rocks show slightly higher concentrations of incoherent elements LILE and HFSE. Our studies enable us to classify the bulk of the dredged rocks as belonging to the association of arc ferrous tholeiites (IAB, IAT), with the composition of a single sample of alkaline basalt (basanite) plotting in the field of alkaline oceanic island basalts (OIB, OIA). The higher concentration of iron in plagioclase phenocrysts confirms the fact that the rocks are part of the high-iron tholeiitic association.