Elements diagrams

Siderophile element diagrams used to classify iron meteorites. Modified from Scott and Wasson (1975). 

Figure 12.1 Finite-element diagram for diffusion to electrodes. The coordinate, x, represents the direction normal to the surface of the electrode. The origin of x is at the central axis in the cylindrical or spherical case.

There is an overall decrease in TiCL, MgO, FeOtotai, CaO and P2O5 with increasing silica contents, whereas K20 shows the opposite trend. AI2O3 and Na20 have a tendency to increase in the mafic compositions and decrease in the silicic rocks, but with considerable scatter. Ferromagnesian trace elements (i.e. Ni, Cr, Co, Sc, V) and Sr decrease with increasing silica, whereas incompatible elements (e.g. La, Th, Rb, Nb, Ta, Zr) show positive trends (Fig. 8.13). Incompatible elements define smooth positive correlations on inter-element diagrams (Fig. 8.14). 

REE patterns for basalts show moderate fractionation and a slightly positive Eu anomaly. The silicic rocks have much higher REE contents than basalts and display negative Eu anomalies (Fig. 8.15a). Extended incompatible element diagrams of mafic rocks show an upward convex pattern with a maximum at Ta and Nb, and a positive spike of Ba, but negative Sr, Hf and, to a lesser extent, Ti (Fig. 8.15b). 

The Sardinian Plio-Quatemary rocks define at least three main evolutionary series that are clearly defined on several major and trace element diagrams (Figs. 9.3, 9.5, 9.6) ... 

One ubiquitous ternary structure is that of PbFCl (ZrSiS, BiOCl, Co2Sb, Fe2As).16,71 We ll call it MAB here because in the phases of interest to us the first element is often a transition metal and the other components, A and B, are often main group elements. Diagram 91 shows one view of this structure, 92 another. 

Figure 13 Trace-element ratios in IDPs. Data from synehrotron X-ray fluoreseenee analyses are plotted on three element diagrams. Element ratios are normalized to bulk Cl abundances (element/Fe)sampie/(element/Fe)ci also denoted element/Fe/CL Cl eomposition lies at the point element/Fe/CI = 1 on eaeh plot. Averages, assuming data are normally distributed (open squares) and assuming the data are log normally distributed (open diamonds), are also shown. Plots (a)-(c) exhibit the behavior of some more refractory elements chromium, calcium, and titanium with respect to nickel, while (d) and (e) show the behavior of zine (relatively volatile) with respect to nickel (relatively refractory) and selenium (relatively volatile) (source Kehm et aL, 2002).

Figure 2 Primitive-mantle normalized minor and trace-element diagrams for (a) the upper, middle, bulk, and lower continental crust (values from Table 1), and (b) oceanic and island arc basalts and the bulk continental crust (all normalizing values are from McDonough and Sun, 1995). The oceanic basalts (N-MORB, normal mid-ocean ridge basalt and OIB, ocean island basalt) are from Sun and McDonough (1989), whereas the arc basalts are from Turner et al. (1997) (Tonga-Kermadec arc) and Pearce et al. (1995) (South Sandwich arc).

Figure 10 Bulk crust normalized multi-element diagrams comparing the chemical fractionation between source, melt and residue for (a) Himalayan leucogranites (Tm, tourmaline) from the Langtang region, Nepal (data from Inger and Harris, 1993) and that for (h) an average leucogranite from the Glenelg River Complex (GRC) in southeastern Australia the field of in situ migmatite leucosomes is shaded (from Kemp, 2001).

Figure 3 Extended trace-element diagrams for average arc lavas (Table 1). Concentrations are normaUzed to N-MORB (Hofmann, 1988). Primitive arc basalts are remarkably similar from one arc to another, and consistently distinct from MORE. In the oceanic Aleutian arc, and in continental arcs, primitive andesites are more enriched than primitive basalts. For plotting purposes some REE abundances are extrapolated from neighboring REEs with more analyses (Pr in Lesser Antilles, Dy in Greater Antilles, Er in Aleutian).

Figure 18 Extended trace-element diagrams (hereafter, spidergrams) for volcanics and felsic plutonic rocks from the Talkeetna arc section, south central Alaska. Concentrations are normalized to N-MORB (Hofmann, 1988). Bold red lines are average values from Table 3. Talkeetna lavas, and plutonic rocks interpreted as hquid compositions, are only shghtly enriched in light REE compared to MORB, but show depletion of Nb and Ta, and enrichment of Pb and Sr, t)fpical for arc lavas worldwide. Their trace-element contents are similar to, for example, lavas from the modem Tonga arc. Data from Greene et al. (2003) and our unpublished research.

Normalized incompatible trace element diagrams are shown in Figure 4. The basalts of the Belingwe belt are generally characterized by flat incompatible element patterns (1.7-4,6x primitive mantle) with marked enrichment of Th (28.3x) and Sr (8.2x). The komatiitic basalts show comparable patterns to those of the basalts but with spiked large ion lithophile element... 

A primitive mantle normalized trace element diagram appears to use a rather random set of trace elements. 

Similar correlation effects arise in the energy. These can be obtained explicitly by substituting x> Eq. (20), into Eq. (58). The comphcated algebra is conveniently carried out with diagrams, as in Eq. (52). The energy matrix element diagrams contain in addition to the solid lines for the V s, dotted lines that denote the fluctuation potentials, Eq. (17). Thus, for example... 

A number of elemental plots of trace elements are presented as ratio plots of the form X lXi vs X- fXi X vs X Xi or Xi vs X2/X1 and are all subject to the constraints of ratio correlation discussed above. In some cases the trace element diagrams are designed only for classification purposes but, where linear trends are important for petrogenetic interpretation, then the problem of spurious correlation applies. In this case the plots should be considered carefully and ideas tested on alternative plots before any petrological conclusions are drawn from the data. 

Normalized multi-element diagrams or incompatible element di a gra ms (spider diagrams)... 

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