Fig. 2. Trace element pattern and chemical proxies of past subduction influence.

(A) The average trace element composition of the basalts from the Western Gakkel Ridge region is plotted relative to N-MORB showing an enrichment in fluid mobile elements (Ba and Sr), similar to BABBs. The similarity to BABB is further supported by (B) and (C). A detailed trace element plot can be found in fig. S1. Data for N-, D-, and E-MORB and BABB are plotted for comparison and taken from Gale et al. (63) (B), and (C) basalts from the Western Gakkel Ridge region show a pronounced enrichment in Ba and ⁸⁷Sr/⁸⁶Sr (up to 0.7037) compared to MORBs from the Atlantic and Pacific, similar to active island-arc and back-arc basins, such as the Lau and Mariana back-arc basin. High ⁸⁷Sr/⁸⁶Sr, Ba/Yb, and Ba/Nb ratios are explained by partial melting of a fluid-enriched mantle source. SMZ basalts tend to have higher Ba/Yb and lower Ba/Nb than WVZ basalts, implying a higher degree of source enrichment. Atlantic/Pacific MORB and Mariana BABB and Lau BABB data, plotted here for comparison, are compiled from Gale et al. (63). MORB data from the pacific include all values from ridge segments ranging between 15°N and 33°S and from the Atlantic ranging between 30°N and 30°S. Literature data from WVZ and SMZ are compiled from Gale et al. (63) and Goldstein et al. (14).