Table S1.
Magnesium isotopic compositions of standards and subducting sediments from DSDP sites 144 and 543 (SE and NE of Martinique Island, respectively)
| Sample | Depth, m | MgO, wt% | LOI | 87Sr/86Sr | 143Nd/144Nd | 206Pb/204Pb | δ26Mg | 2 SD | δ25Mg | 2 SD |
| Standards | ||||||||||
| San Carlos olivine | −0.27 | 0.07 | −0.14 | 0.06 | ||||||
| Duplicate | −0.25 | 0.07 | −0.11 | 0.06 | ||||||
| Replicate | −0.29 | 0.09 | −0.14 | 0.06 | ||||||
| Replicate | −0.24 | 0.05 | −0.12 | 0.05 | ||||||
| Average | −0.26 | 0.05 | −0.13 | 0.03 | ||||||
| Hawaiian seawater | −0.86 | 0.07 | −0.43 | 0.06 | ||||||
| Duplicate | −0.82 | 0.07 | −0.44 | 0.05 | ||||||
| Replicate | −0.86 | 0.11 | −0.45 | 0.10 | ||||||
| Duplicate | −0.86 | 0.10 | −0.45 | 0.07 | ||||||
| Replicate | −0.87 | 0.07 | −0.45 | 0.05 | ||||||
| Duplicate | −0.84 | 0.07 | −0.43 | 0.05 | ||||||
| Duplicate | −0.88 | 0.10 | −0.46 | 0.07 | ||||||
| Duplicate | −0.88 | 0.09 | −0.45 | 0.06 | ||||||
| Duplicate | −0.84 | 0.06 | −0.44 | 0.04 | ||||||
| Average | −0.86 | 0.04 | −0.45 | 0.02 | ||||||
| Rec. value† | −0.83 | 0.09 | −0.43 | 0.06 | ||||||
| JB-1* | −0.27 | 0.07 | −0.14 | 0.05 | ||||||
| Duplicate | −0.27 | 0.09 | −0.12 | 0.06 | ||||||
| Duplicate | −0.25 | 0.06 | −0.13 | 0.04 | ||||||
| Average | −0.26 | 0.04 | −0.14 | 0.03 | ||||||
| Rec. value† | −0.27 | 0.10 | −0.15 | 0.04 | ||||||
| SCo-1* | −0.86 | 0.10 | −0.46 | 0.07 | ||||||
| Duplicate | −0.85 | 0.09 | −0.43 | 0.06 | ||||||
| Duplicate | −0.87 | 0.06 | −0.46 | 0.04 | ||||||
| Average | −0.86 | 0.05 | −0.45 | 0.03 | ||||||
| Rec. value† | −0.89 | 0.08 | −0.47 | 0.05 | ||||||
| SGR-1* | −1.03 | 0.11 | −0.54 | 0.10 | ||||||
| Rec. value† | −0.98 | 0.12 | −0.50 | 0.06 | ||||||
| DSDP site 144: South Antilles (9.454°N, 54.342°W) | ||||||||||
| 144A-2–2W-79–80.5* | −0.32 | 0.09 | −0.16 | 0.06 | ||||||
| Duplicate | −0.32 | 0.06 | −0.17 | 0.04 | ||||||
| Average | 41 | 0.88 | 36.7 | 0.708098 | 0.511942 | 19.3454 | −0.32 | 0.05 | −0.17 | 0.03 |
| 144–1-4W-98–99* | −0.78 | 0.11 | −0.40 | 0.10 | ||||||
| Duplicate | −0.76 | 0.06 | −0.39 | 0.04 | ||||||
| Average | 62 | 0.56 | 36.2 | 0.707944 | 0.511998 | 19.4381 | −0.76 | 0.05 | −0.39 | 0.03 |
| 144A-3–1W-79–80* | 0.53 | 0.11 | 0.27 | 0.10 | ||||||
| Duplicate | 0.52 | 0.06 | 0.26 | 0.04 | ||||||
| Average | 141 | 1.33 | 22.8 | 0.708335 | 0.511988 | 19.7053 | 0.52 | 0.05 | 0.26 | 0.03 |
| 144A-3–3W-125–126* | −0.35 | 0.09 | −0.17 | 0.06 | ||||||
| Duplicate | −0.42 | 0.06 | −0.22 | 0.04 | ||||||
| Duplicate | −0.37 | 0.09 | −0.20 | 0.06 | ||||||
| Duplicate | −0.41 | 0.06 | −0.21 | 0.04 | ||||||
| Duplicate | −0.42 | 0.06 | −0.22 | 0.04 | ||||||
| Average | 144 | 0.52 | 36.5 | 0.708301 | 0.511780 | 19.6460 | −0.40 | 0.03 | −0.21 | 0.02 |
| 144–3-1W-120–121* | 0.32 | 0.11 | 0.18 | 0.10 | ||||||
| Duplicate | 0.30 | 0.06 | 0.14 | 0.04 | ||||||
| Average | 163 | 0.75 | 30.3 | 0.708694 | 0.511730 | 20.0424 | 0.30 | 0.05 | 0.15 | 0.03 |
| 144A-6–1W-125–130 | −0.23 | 0.06 | −0.12 | 0.04 | ||||||
| Duplicate | −0.25 | 0.07 | −0.13 | 0.05 | ||||||
| Average | 190 | 0.56 | 37.7 | 0.707904 | 0.511840 | 22.9249 | −0.24 | 0.05 | −0.13 | 0.03 |
| 144–6-1W-46–48* | −0.41 | 0.09 | −0.20 | 0.06 | ||||||
| Duplicate | −0.38 | 0.07 | −0.19 | 0.05 | ||||||
| Duplicate | −0.40 | 0.09 | −0.21 | 0.06 | ||||||
| Duplicate | −0.40 | 0.06 | −0.21 | 0.04 | ||||||
| Average | 295 | 1.02 | 13.5 | 0.709158 | 0.512101 | 19.1781 | −0.39 | 0.04 | −0.20 | 0.03 |
| 144–7-1W-80–82* | −0.04 | 0.07 | −0.03 | 0.06 | ||||||
| Duplicate | −0.04 | 0.07 | −0.02 | 0.05 | ||||||
| Duplicate | −0.03 | 0.07 | −0.01 | 0.05 | ||||||
| Average | 299 | 2.03 | 11.5 | 0.710830 | 0.512105 | 18.8081 | −0.04 | 0.04 | −0.02 | 0.03 |
| 144–7-1W-125–130 | 299 | 1.63 | 12.2 | 0.709141 | 0.512105 | 18.9347 | −0.16 | 0.07 | −0.08 | 0.06 |
| DSDP site 543: North Antilles (15.712°N, 58.654°W) | ||||||||||
| 543–23-2W-73–75 | 0.04 | 0.07 | 0.03 | 0.05 | ||||||
| Duplicate | 0.03 | 0.07 | 0.02 | 0.05 | ||||||
| Duplicate | 0.03 | 0.07 | 0.01 | 0.05 | ||||||
| Duplicate | 0.03 | 0.05 | 0.01 | 0.05 | ||||||
| Average | 220 | 1.96 | 15.1 | 0.718270 | 0.511953 | 19.4023 | 0.03 | 0.03 | 0.02 | 0.03 |
| 543–26-1W-120–122* | −0.19 | 0.09 | −0.08 | 0.06 | ||||||
| Duplicate | −0.13 | 0.07 | −0.07 | 0.05 | ||||||
| Duplicate | −0.18 | 0.07 | −0.09 | 0.05 | ||||||
| Duplicate | −0.15 | 0.07 | −0.08 | 0.05 | ||||||
| Duplicate | −0.17 | 0.07 | −0.09 | 0.03 | ||||||
| Average | 248 | 2.17 | 12.1 | 0.717401 | 19.1260 | −0.16 | 0.03 | −0.08 | 0.02 | |
| 543–29-4W-45–47* | 0.11 | 0.09 | 0.06 | 0.06 | ||||||
| Replicate* | 0.09 | 0.10 | 0.05 | 0.07 | ||||||
| Duplicate | 0.10 | 0.07 | 0.05 | 0.05 | ||||||
| Average | 280 | 1.45 | 15 | 0.719727 | 0.511947 | 19.5323 | 0.10 | 0.05 | 0.05 | 0.03 |
| 543–31-1W-76–78* | 0.01 | 0.09 | 0.01 | 0.06 | ||||||
| Duplicate | 0.00 | 0.07 | 0.01 | 0.05 | ||||||
| Duplicate | 0.00 | 0.07 | −0.01 | 0.05 | ||||||
| Average | 295 | 1.67 | 15.2 | 0.718082 | 0.511880 | 19.5283 | 0.00 | 0.04 | 0.00 | 0.03 |
| 543–33-2W-71–73* | −0.13 | 0.07 | −0.05 | 0.06 | ||||||
| Replicate* | −0.13 | 0.11 | −0.06 | 0.10 | ||||||
| Duplicate | −0.15 | 0.07 | −0.08 | 0.05 | ||||||
| Duplicate | −0.15 | 0.07 | −0.08 | 0.05 | ||||||
| Duplicate | −0.15 | 0.07 | −0.07 | 0.03 | ||||||
| Average | 315 | 2.63 | 13.7 | 0.716811 | 0.511918 | 19.1515 | −0.14 | 0.03 | −0.07 | 0.02 |
| 543A-5–3W-47–49* | 0.19 | 0.07 | 0.11 | 0.05 | ||||||
| Duplicate | 0.25 | 0.07 | 0.13 | 0.05 | ||||||
| Replicate* | 0.18 | 0.09 | 0.09 | 0.06 | ||||||
| Duplicate | 0.20 | 0.07 | 0.10 | 0.05 | ||||||
| Duplicate | 0.24 | 0.07 | 0.13 | 0.05 | ||||||
| Duplicate | 0.23 | 0.07 | 0.13 | 0.05 | ||||||
| Average | 364 | 3.07 | 14.6 | 0.722128 | 0.511936 | 19.2605 | 0.22 | 0.03 | 0.12 | 0.02 |
| 543A-8–1W-116–118* | −0.33 | 0.09 | −0.17 | 0.06 | ||||||
| Duplicate | −0.37 | 0.07 | −0.18 | 0.05 | ||||||
| Average | 390 | 4.94 | 19.7 | 0.731781 | 0.511965 | 19.3564 | −0.36 | 0.05 | −0.18 | 0.04 |
| 543A-10–1W-25–27* | 0.06 | 0.09 | 0.04 | 0.06 | ||||||
| Duplicate | 0.05 | 0.06 | 0.02 | 0.04 | ||||||
| Average | 408 | 2.38 | 28.8 | 0.709340 | 0.512077 | 19.1270 | 0.05 | 0.05 | 0.03 | 0.03 |
The depth, MgO, LOI, and Sr, Nd, Pb isotopic data are from Carpentier et al. (6, 7); 2 SD = 2 times the SD of the population of n (n > 20) repeated measurements of the standards during an analytical session. Duplicate refers to repeated measurement of Mg isotopic ratios on the same purified Mg cuts at different days. Replicate refers to repeated column chemistry and measurement of different aliquots of a stock solution. The average value and associated 2 SD are error-weighted values calculated by Isoplot.
*
Data that were measured on a Nu Plasma HR-MC-ICP-MS; all other data were measured on a Nu Plasma II MC-ICP-MS.
†
Rec. value is recommended value, from Teng et al. (44).