Abstract
87Sr/ 86Sr and 143Nd/ 144Nd ratios, REE and selected minor and trace elements are presented and compared for present-day volcanic rocks in the Scotia Sea. Tholeiitic basalts from the South Sandwich Islands show widely ranging contents of some lithophile elements, e.g. K 2O (0.09–0.55%) and Rb (1.55–14.2 ppm), but fairly constant Na 2O and Sr. Total REE contents range from about 4–20 times chondritic abundances with significant light-REE depletion and both positive and negative Eu anomalies. The variations in minor and trace element abundances are consistent with low-pressure fractional crystallization of plagioclase and clinopyroxene but only minor amounts of olivine. The 87Sr/ 86Sr and 143Nd/ 144Nd ratios of the parental magmas are thought be 0.7038–0.7039 and 0.51301–0.51314 respectively, and indicate derivation of at least some 87Sr from subducted ocean crust. The back-arc tholeiites in the Scotia Sea have lower 87Sr/ 86Sr ratios (0.7028–0.7033), similar 143Nd/ 144Nd ratios (0.51305) and are variably light-REE-enriched (Ce N/Yb N= 1.0–1.6) . Total REE contents are comparable to those of the South Sandwich Islands tholeiites.
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