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doi:10.2204/iodp.proc.309312.204.2009

Summary

Major and trace element concentrations of 159 pool samples from Expedition 309/312 were analyzed by XRF and ICP-MS. Accuracy of major element analyses is high. Almost all trace elements have values consistent with recommended values. Major element concentrations determined by this study are generally similar to shipboard data as shown with respect to downhole variations. Trace element abundances of Zr, Hf, Th, and U of Expedition 312 samples were analyzed by alkali fusion method because of the presence of zircon.

When compared to shipboard data, our results for trace elements, V, Cr, Ni, Zn, Y, and Zr are similar in terms of downhole variations. Other elements tend to show wholly or partially different values, may be due to differences in analytical method or differences of analyzed samples.

Almost all basaltic rocks of Expedition 309/312 show N-MORB REE patterns. However, three samples (309-1256D-80R-2, 92–102 cm; 312-1256D-189R-1, 0–13 cm; and 189R-1, 71–89 cm) show LREE-enriched patterns. Moreover, one sample (312-1256D-234R-1, 26–29 cm) from the bottom of hole has highly evolved N-MORB chemistry. It may imply that late-stage magmatism as shown by the late dike and lava pond that formed the uppermost basement at Site 1256, is characterized by evolved magmas.

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