This chapter summarizes the oxygen isotope geochemistry of terrestrial basalts and
their mantle sources, including the conceptual framework for interpreting such data and
the phenomenology of known variations. In particular, the first section outlines the
motivations for and first-order results of oxygen isotope studies of terrestrial and lunar
basalts over the last 30 years; the second section reviews oxygen isotopic fractionations
among phases relevant for studying basalts and mantle rocks; the third summarizes
variations in δ^(18)O of various crustal rocks that may contribute to the petrogenesis of
basalts either as subducted source components or lithospheric contaminants; and the
final and longest section describes observed oxygen isotope variations of major classes
of terrestrial basalts and related mantle nodules with an emphasis on data generated
within the last six years using laser-based fluorination techniques. In the interests of
brevity, I do not describe in detail methods for oxygen isotope analysis or changes in
δ^(18)O of volcanic rocks caused by sub-solidus alteration; however, these issues are
important practical considerations for anyone studying oxygen isotope compositions of
basalts and interested readers are directed to the following references: analytical
methods: Sharp (1990), Mattey and Macpherson (1993), and Valley et al. (1995); basalt
alteration: Muehlenbachs (1986), Alt (1993), and Staudigel et al. (1995)
