Frisby et al.: Seawater-derived rare earth element addition to abyssal peridotites during serpentinization. Submitted to Lithos.
Supplementary text.
Leaching and digestion protocol details.
H2O leach: One gram of powdered sample was weighed and transferred to a 50ml precleaned polypropylene centrifuge tube and 10ml of 18MΩ H2Owas added to the tube, sonicated for 10 minutes and allowed to react for 2 hours. The sample was then centrifuged and the supernatant extracted to an acid washed 30ml PFA beaker.
Na-Acetate leach: After the H2O leach, 10 ml of (NaOAc) was added to the sample. The tube was shaken with a vortex mixer and the solution left to react overnight. Then the sample was centrifuged and the supernatant extracted into another acid washed 30ml PFA beaker. The sample was then rinsed 3 times with 5ml 18MΩ H2O, and the rinse solutions were added to the NaOAc supernatant.
HH- leach: After the NaOAc leach 10 ml of 1M-HH was added to the sample, vortexed and left to react overnight. Once reacted, the sample was centrifuged and the supernatant extracted to a 30ml PFA beaker. The sample was then rinsed 3 times with 18MΩ H2O and the rinses were combined with the HH supernatant.
6M HCl leach: After the HH-leach, 10 ml of 6M HCl was added to the samples, vortexed and left to react for two hours at room temperature. The sample was then centrifuged and the supernatant transferred to a clean 30ml PFA beaker. The sample was then rinsed three times with 18MΩ H2O and the rinses were combined with the 6N HCl.
Once dry, the four leachate solutions were reacted with 2 ml concentrated HNO3, for an hour and then dried at 80°C. 50µl of H2O2 was added to both the NaOAc and HH leachates. This process was repeated twiceas it was necessary to enhance subsequent sample dissolution. Once dry the samples were re-dissolved in 10ml of 2% HNO3 and an aliquot was removed and diluted for trace element analyses. The concentrations of the aliquots are reported as μg/g of the original powder (Table 4).
Residual and bulk rock dissolution: The residual rock after leaching was the dissolved in 3:1 HF:HNO3. After drying the sample, it was redissolved in 6N HCL plus 8ml of 0.9M boric acid in a 10N HCl solution, in order to complex the F and limit the formation of insoluble fluorides (Koornneef et al., 2010), heated for three hours and dried at 80°C. Once dry, the samples were redissolved in 7N HNO3, dried and finally picked up in 100 ml 2% HNO3. An aliquot was taken for trace element analyses and the remaining solution was then prepared for Nd and Sr isotopes. Hf isotopes were also determined but will be presented elsewhere with additional data.