Figure 9. Hf–Nd co-variations (after Pearce et al. 1999) in the basaltic lavas from the Tethyan suture zone ophiolites in western Turkey. Hf and Nd define extent of positive and negative displacements of samples from the mantle array (shown as shaded area) defined by average MORB–OIB compositions (Pearce et al. 1999). values indicate displacements from the mantle array and positive value corresponds to high element ratios with respect to the mantle array. Equal Hf anomalies (Hf) are represented by straight lines parallel to the MORB–OIB array, with positive Nd values corresponding to negative Hf anomalies. Positive Nd values record the proportion of subducted Nd in mantle sources. Hf describes the negative Hf anomaly as a Hf depletion (that is, Hf < 1), whereas Nd describes the anomaly as a Nd enrichment. Both Hf and Nd can be expressed in terms of the element compositions of the mantle and subduction zone end-members. Mixing trends between depleted MORB mantle (DMM) and subducted pelagic sediment (see Pearce et al. 1999 for detail) are also shown for a mass fraction of subduction component in the mantle between 0.05 and 0.2 and a range of values of r_Nd and r_Hf at r_Yb equal to 0 (dashed lines) or 2 (solid lines). Representative ratios (r) for Hf and Nd between the subduction component and the mantle are shown as inset.