ABSTRACT

A potpourri of mutually inconsistent normalized multi-element diagrams (‘spider-diagrams’) has been used in geochemistry, on the basis of different choices of: (i) element order; (ii) normalizing materials (chondrite, ‘primitive’ mantle, MORB, composite shale, etc.); (iii) normalizing values (many incompatible sets are used for conventional chondrite-normalized rare-earth element (REE) plots, which generate ‘enrichments’ varying by as much as 65 % from a single rock, and Eu anomalies of quite divergent strengths). Standardization is urgently required, not least because (1) many published diagrams are unnecessarily difficult to compare; (2) different element orders can drastically affect patterns, or lead to artificial ‘pseudo-anomalies’ lacking petrogenetic significance. One type of chondrite- and MORB-normalized spider-diagram (each based on one set of normalizing values) should suffice to represent most igneous rocks. Arguments favouring the chondrite-normalizing REE values of Nakamura (1974), the chondrite-normalized 19-element plot of Thompson (1982), and the MORB-normalized 15-element plot of Pearce (1982, 1983) are preferred, hopefully as an impetus to wider discussion. Consistently ordered sub-sets can be chosen from either multi-element plot if fewer elements are in fact analysed. A FORTRAN77 program has been written to realize these suggestions.