Multi-element diagrams for igneous rocks

There are three popular ways of normalizing trace element data for presentation as a spider diagram. These include an estimated primitive mande composidon and chondridc meteorites — two views of the primitive undifferentiated earth. Others normalize their data to primitive MOKE. Each version of the spider diagram has a slightly different array of elements with a slightly different order. In detail there are innumerable variations on each particular theme, usually dictated by the number of trace elements and the quality of their determinations in a particular data-set. This state of affairs is not satisfactory and some standardization is desirable. First, however, we consider the present state of the art . 

Primordial The primitive mantle is the composition of the mantle before the continental crust (primitive) formed. One of the most frequently used estimates of its composition is that of 

Figurt 4.24 Trace clement concentrations normalized to the composition of chondridc meteorites and plotted from left to right in order of increasing compadbility in a Small fracnon melt of the mantle. The normalizing values are those of Thompson (1982) — Table 4.7, column 6. (a) Upper and lower continental crust from Weaver and Tarney (1984) — data in Table 4.8 (b) Average N-type MORB from Saunders and Tamey (1984) and OIB from Sun (1980) — data in Table 4.8. 

The normalizing values used by Pearce (1983) are taken from the average MORB of Pearce et al. (1981) and are given in Table 4.7, column 10, A longer list of elements arranged in a slightly different order is used by Bevins et al (1984) 

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