Previous   |    Close   |    Next

Figure F13. Two hypotheses for the evolution of Izu arc crust: from the beginning and from the middle. Red = crust rich in fluid-mobile recycled slab components and strongly depleted in mantle-derived fluid-immobile elements typical of the modern arc front; blue = crust created where diminished slab signature and lower degrees of mantle melting producing crust enriched in mantle-derived fluid immobile elements typical of the rear-arc seamount chains, which are more similar to average continental crust than are arc front magmas (Fig. F12). Thus, the Neogene Izu arc is asymmetric in geochemical characteristics. In the “from the beginning” hypothesis, the geochemical asymmetry has always existed; in the “from the middle” hypothesis, the asymmetry developed over time. Each model has implications for the mechanisms involved in generation of arc magmas and of continental crust.

Previous   |    Close   |    Next   |    Top of page