Origin of Sr, Nd and Pb isotopic systematics in high-Sr basalts from central Arizona

Alkalic and tholeiitic basalts were erupted in the central Arizona Transition Zone during Miocene-Pliocene time before and after regional faulting. The alkalic lava types differ from the subalkaline lavas in Sr, Nd and Pb isotopic ratios and trace element ratios and, despite close temporal and spatial relationships, the two types appear to be from discrete mantle sources. Pre-faulting lava types include: potassic trachybasalts (87Sr/86Sr = 0.7052 to 0.7055, e{open}Nd= -9.2 to -10.7); alkali olivine basalts (87Sr/ 86Sr = 0.7049 to 0.7054, e{open}Nd= -2 to 0.2); basanite and hawaiites (87Sr/86Sr = 0.7049 to 0.7053, e{open}Nd= -3.5 to -7.8); and quartz tholeiites (87Sr/86Sr = 0.7047, e{open}Nd= -1.4 to -2.6). Post-faulting lavas have lower 87Sr/86Sr (