Whole-rock Geochemistry

Abstract

As in Chapter 4, this chapter concentrates on descriptive geochemistry; interpretation is left to Chapter 8. Table 5.1 presents averages for the various branches and rock-types (Fig.1.2), based on data for over 5, (XX) specimens contained in LAMPDA (Appendix D). Because coverage varies so much (e.g. some specimens are analyzed only for major elements, some only for isotopes), numbers of values for individual variables vary greatly within Table 5.1, and are therefore clearly annotated. For KIL, averages calculated from LAMPDA are basically in agreement with the consensus of published averages (e.g. Dawson 1980; R.H.Mitchell 1986; Bergman 1987), so the latter are reproduced in Table 5.1. For CAL, AL, UML and LL, the new averages differ little from arithmetic means already presented in Rock (1977, 1984, 1986, 1987a), but are felt preferable for two reasons:

• they are in most cases based on vasdy larger numbers of data-values;

• an overall figure has been chosen from a range of location estimates (aridimetic and geometric means, median, etc.), which should provide better estimates for the mostiy non-Gaussian distributions than can arithmetic means alone (cf. Rock 1987a, 1988c).