Trace element discrimination diagrams

Pearce, J., Harris, N.B.W., Tindle, A.D. 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology, 25, 956-983. 

Pearce J.A. and Gale G.H., 1977, Identification of ore-deposition environment from trace element geochemistry of associated igneous host rocks. Geol Soc. Spec. Publ, 7, 14-24. Pearce JA., Harris N.B.W. and Tindle A.G., 1984, Trace element discrimination diagrams for the tectonic interpretation of granitic rocks, f. Petrol, 25, 956-983. 

F2O5 diagram of (1975) is that it daims to differentiate between oceanic and continental basalts. T.B. Pearce Most trace element discriminant plots allocate ocean-island and continental-flood... 

Pearce J.A. 1996, A user s guide to basalt discrimination diagrams. In Wyman, D.A. (ed) Trace Element Geochemistry of Volcanic Rocks Applications for Massive Sulphide Exploration. Geological Association of Canada, Short Course Notes, v.12, p.79-113. 

In order to determine the source composition of sediments using trace elements, it is necessary to ascertain that the element is immobile under conditions of diagenesis and weathering (Spalletti 2008). Several ratios and plots may be used to define the source rocks. The felsic source rock compositions are found in the Co/Th vs. La/Sc diagram (Fig. 3 Table 1). Other trace element characteristics of sedimentary rocks also place some constrains on the nature of the source rock. Floyd Leveridge (1987) used a La/Sc vs. Hf plot to discriminate between different source compositions. In this plot, most data fall in the felsic source to mixed felsic/basic source field (Fig. 4 Table 1). 

Figure 7. Variation of some trace elements in spring waters from common rock types (Derron, 1999). No simple discrimination diagrams exists for traces. The two diagrams shown here, involving Ni, Rb, Ba and Sr are more or less the only ones which discriminate the rock categories distinguished in Fig. 6.

Discrimination diagrams have also been applied to the environment of deposition of sedimentary rocks. Potter et al. (1965) showed that a discriminant function based upon the trace elements B and V could be used to distinguish between freshwater and marine argillaceous sediments. More recently tectonic discrimination diagrams have also been extended to sedimentary rocks. Bhatia (1983) and Roser and Korsch (1988) have produced discriminant function diagrams which allow the identification of the provenance of sandstones according to their plate tectonic setting. 

There are a large number of discrimination diagrams applicable to basalts and basaldc andesites which use trace elements, major and minor elements and the mineral clinopyroxene. These are considered in turn. Table 5.1 classifies the different types of basalt according to tectonic setting and shows which diagrams might be useful in their identification. 

Discrimination diagrams which utilize the major elements are less likely to be successful than those for trace elements, for there is extensive overlap in major element chemistry between MORB, back-arc basin tholeiites and volcanic-arc basalts (Perfit et a/., 1980). This is because there is a large number of possible variables controlling the element concentrations and fewer elements to choose from. Thus it is difficult to identify elements which are either completely immobile or are unaffected by the effects of crystal fractionation. 

Discrimination diagrams for clastic sediments using trace elements... 

Unlike igneous rocks, where most discriminant diagrams are based upon trace r , element chemistry, diagrams of this sort are in their infancy in sedimentary... 

The major components CaO and MgO in dolomite have a minimal range indicative of very small variation in Ca/(Ca+Mg+Fe) ratios, whereas the minor elements such as SrO and MnO have a wide variation. Therefore trace components in carbonate minerals can be used as discriminant parameters to determine the origin of the carbonate rocks (cf. Yang LeBas 2004). Compositional variation of carbonate minerals from Chehelkureh on the basis of MnO or SrO (wt%) versus [Ca/(Ca+Mg+Fe)j (atoms per formula unit, a.f.u.) diagrams (Fig. 4) show that the MnO and SrO contents in dolomite-ankerite are higher than those in siderite-magnesite and accessory calcite. 

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