Temporal and spatial isotopic patterns in Cordilleran arcs and tectonic implications
A compilation of age, Sr, Nd and O isotopic analyses of plutonic rocks from the western North American Cordillera shows that the high-flux pulses of magmatism that make up most of the exposed North American arcs are dominated by upper plate lithospheric mass. Oceanic crustal (basalts and sediments) melting cannot be a principal mechanism responsible for arc magmatism. Mass balance calculations show that no more than 50% of that mass can be mantle-derived.
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