Origin of the Quaternary Basalts from the Black Rock Desert Region, Utah: Strontium Isotopic Evidence
The basalts of the Black Rock Desert region in Utah have Sr 87 /Sr 86 ratios that vary from 0.7044 to 0.7059. Although this variation may be explained by derivation from inhomogenous mantle, it is also broadly compatible with a fractionation-assimilation model proposed for these basalts. Basalts of the Ice Spring field show an increase in Sr 87 /Sr 86 with decreasing Rb and Rb/Sr as a function of eruptive age. Such a trend may be explained by mixing of magmas having different differentiation-assimilation histories.