A mineralogical and geochemical analysis of basaltic lavas from the Zion National Park Region, Southwestern Utah
Price, Jason R. (Jason Rodney)
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In the Transition zone of southwestern Utah, basaltic lavas are geochemically defined as a subduction suite and a plume suite. These predominantly basic lavas are late Cenozoic (<17 Ma) in age, with the two suites related in time and space. This paper suggests a two layer upper mantle model, an upper metasomatized lithospheric layer underlain by an asthenospheric layer, with both alkali basaltic and olivine tholeiitic magmas being generated by varying degrees of partial melting of spinel lherzolite in each individual layer. Due to the greater depth at which asthenospheric magmas are derived, mixing occurs between the alkali basaltic and the olivine tholeiitic magmas during ascent through the lithosphere. Since lithosphere-derived magmas ascend to the crust soon after generation, significantly less mixing occurs, if at all. Time-space relations support such a model.