An Evaluation of Five Models of Arc Volcanism

Abstract A first-order observation of convergent margin volcanism is that continental arc stratovolcanoes have substantially elevated incompatible element abundances and notable fractionations certain ratios compared to oceanic stratovolcanoes. Models account for these differences include (1) a greater influence differentiation contamination due thicker crust, (2) variable slab flux controlled by the thermal structure, (3) heterogeneity ambient mantle wedge, (4) variations in extents melting caused wedge (5) diapirs subduction erosion provide different source materials regime. An evaluation models using geochemistry, experimental results, physical models, tectonic constraints shows 1, 2, 5 are inconsistent with variety observations. While component always present along front, not primary cause continental/oceanic dichotomy. There compelling evidence 3 4, melting, which combination straightforward explanations features geochemistry. Oceanic arcs back-arc basins formed large an more depleted than normal ocean ridge basalt source. Continental smaller usually enriched. The apparent components can be understood leverage has on compositions. These conclusions apply global regional systematics, say individual volcanoes or samples may influenced crustal processes, temperature, sediment diapir intermittently incorporated into wedge.