Basalts erupted from recent volcanoes in central Nicaragua can be divided into distinct high-and low-Ti suites. Low-Ti basalts have higher concentrations of LILE and LREE than high-Ti basalts. In addition, low-Ti basalts have obviously higher Ba/La, La/Sm, and 87Sr/86Sr, and lower Ti/Zr, than high-Ti basalts. In contrast, there are no mineralogical or petrographic differences between the two suites.The differences between the high-and low-Ti basalts of central Nicaragua are inherited from their source regions. The primary magmas of both are generated in the mantle wedge. However, low-Ti primary magmas come from parts of the wedge which bear a strong subduction zone signature, including that of subducted pelagic sediment. On the other hand, the primary magmas of the high-Ti basalts are generated in parts of the wedge relatively free of subduction zone influence.Subducted pelagic sediment can therefore be a key source component at active continental margins as well as at island arcs. Pelagic sediment could also be responsible for subtle high-field-strength element fractionations within subduction zone magmas. The mantle wedge beneath Nicaragua, which is variably modified by the subducting plate, is relatively enriched suboceanic mantle.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology