Chondrite-normalized rare-earth element patterns for the Zasur'ya depleted (A), transitional (B) and enriched (c) lavas. OIB, MORB and normalization values are from Sun and McDonough (1989). Symbols as in Fig. 4.

Contexts in source publication

Context 1

... 1.3 and 1.9 wt.%, and P 2 O 5 is in the range 0.13-0.19 wt.%. Both TiO 2 and Fe 2 O 3(tot) increase with decreasing MgO suggesting fractionation of olivine and pyroxene ( Fig. 5A and D). In this suite of basalts, La/Sm n ranges from 0.6 to 1.0, and Gd/Yb n ranges from 1.0 to 1.3 (Table 1). The REE patterns are flat to moderately LREE depleted ( Fig. 6A) and display no Eu anomalies. The samples have subchondritic and near-chondritic Ti/Zr ratios, whereas Zr/Y ratios are supra-and near-chondritic independently of their #Mg. The ratios of Al 2 O 3 /TiO 2 and Zr/Nb are consistently high, 8.9 and 35.0, compared to 5.8 and 6.2 in the transitional and enriched varieties, respectively ...

Context 2

... basalts are defined on the basis of their positive Nb anomalies in the trace-element diagram (Fig. 7) and pronounced positively fractionated REE patterns, where La/Yb n = 3.2-11 compared to La/Yb n = 0.8-1.4 for the depleted counterparts ( Fig. 6; Table 1). Relative to the suites of depleted tholeiitic basalts, they have higher contents of relatively or clearly incompatible elements (Ti, P, Th, La, Nb, Sm) at a given MgO value (Fig. ...

Context 3

... 4.0 vs. 6.7 av.) than the enriched counterparts (Table 1; Fig. 5A, B, and F). Both types of basalts show LREE enrichment though to a different degree (Fig. 6). Transitional and enriched basalts show less Th depletion over La (Th/La n = 0.8 vs. 0.9) compared to depleted basalts (Th/La n = 0.6). Both transitional and enriched varieties are characterized by clear positive anomalies of Nb with respect to La: Nb/La pm = 1.6 and 1.4 (averages), respectively (Table 1, Fig. 7). A subset of the ...

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... the studied set of least altered basaltic rocks, evidence for low mobility of HFSE, REE (except Eu) and, to a lesser degree, Th includes the following: (1) there is no significant enrichment or depletion of groups of elements (e.g., light REE) in a given rock type over a range of L.O.I. (Fig. 6; Table 1); (2) primitive mantle-normalized trace-element diagrams of given suites of basalts associated in the field exhibit coherent patterns for Th, HFSE, and REE (Fig. 7); (3) Th-Nb-La inter-element relationships do not correlate with the CIA (chemical index of alteration; not shown here), Eu/Eu à , or loss on ignition ( Fig. 11A-C; ...

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... of partial melting involved in the genesis of mafic oceanic lavas ( Polat et al., 1999 and the references cited therein). The medium to high differentiation of HREE (Gd-Yb n = 1.5-2.4) in the most of Zasur'ya transitional and enriched samples may reflect mantle melting in the garnet stability field (e.g., Green, 1994;Hirschman and Stolper, 1996; Fig. 6B and C), because garnet preferentially sequesters the HREE into its structure. Besides, the higher enrichment of the transitional and enriched varieties in Nb compared to the depleted group is typical of plume-related volcanic rocks, i.e., OIBs (e.g., Sun and McDonough, 1989; Figs. 5G, 7, 9). Saunders et al. (1988) supposed that Nb resides in ...