The data sets reported in Tables T1, T2, T3, T4, and T5, other than those collected by the first author and his colleagues at Massachusetts Institute of Technology (MIT), were collected by investigators using different analytical schemes, techniques, and standards. They describe these in papers in the Leg 118 and Leg 176 volumes (Bloomer et al., 1991; Hebert et al., 1991; Natland et al., 1991; Niu et al., Chap. 8, this volume; Ozawa et al., 1991; Robinson et al., Chap. 9, this volume). The new data collected at the MIT Electron Microprobe Facility used a JEOL JXA-733 Superprobe. The operating conditions included a 15-keV accelerating voltage, 10-nA probe current, 10-µm spot size, and 10- to 40-s per element counting time. Standards used included diopside-jadeite (dj35, synthetic), aluminous orthopyroxene (synthetic), forsterite (synthetic), fayalite (synthetic), marjalotti olivine, Amelia albite, anorthite (synthetic), orthoclase glass (synthetic), Lake County labradorite, spinel (synthetic), hematite (synthetic), rutile (synthetic), uvarovite (synthetic), rhodonite (synthetic), nickel sulfide (synthetic), chromite (synthetic), and Wilberforce apatite. Data reduction was done using the Phi-Rho-Z method.
The reader will note that there is no systematic comparison of interlaboratory bias here. Insofar as these analyses represent the analytical procedures of many different laboratories and were collected over some 11 yr, this is not really possible. Accordingly, the user and reader should take note and not draw too fine a distinction between analyses exhibiting small differences in concentration. Generally, for example, it is safe to assume that differences of few mole percent forsterite between data sets are real but one is on very shaky ground for differences less than that without careful justification.