Chapter 17 Ans

Chapter 17 Ans - Answers for Chapter 17: Subduction-Related...

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Answers for Chapter 17: Subduction-Related Igneous Activity, Part II: Continental Arcs. 1. Cite some reasons why crustal contamination is more evident in continental arcs than in island arcs. The continental crust through which arc magma must travel is thick and more enriched than oceanic arc crust. The sub-continental lithospheric mantle is believed to also be an enriched magma source and/or contaminant. The thick continental crust is a more effective density trap for rising mafic magma and may stall them for longer durations and allow more crust/magma interaction and differentiation. Continents stand in higher relief and shed more sediment to the arc and ocean beyond. This enriched sediment may then be subducted into the igneous system. 2. Why is the subcontinental lithospheric mantle likely to differ significantly from the sub-oceanic lithospheric mantle? The subcontinental lithospheric mantle has probably been anchored as a keel to the continental crust since the creation of that crust, ranging in age to over 3 Ga. Although initially depleted, this mantle is believed to have been re-enriched (by mantle fluids and/or melts) during its residence. Many samples from kimberlite pipes exhibit enriched characteristics. 3.
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Chapter 17 Ans - Answers for Chapter 17: Subduction-Related...

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