Dataset: Radiochemistry data for rocks and deposits from the Lost City Hydrothermal Field at the Atlantis Massif from 2018-2020

ValidatedFinal no updates expectedDOI: 10.26008/1912/bco-dmo.864460.1Version 1 (2022-01-04)Dataset Type:Cruise Results

Principal Investigator: Willard S. Moore (University of South Carolina)

Co-Principal Investigator: Claudia R. Benitez-Nelson (University of South Carolina)

Co-Principal Investigator: Jessica D. Frankle (University of South Carolina)

Co-Principal Investigator: Gretchen Fruh-Green (ETH-Zurich)

Co-Principal Investigator: Susan Q. Lang (University of South Carolina)

BCO-DMO Data Manager: Taylor Heyl (Woods Hole Oceanographic Institution)

BCO-DMO Data Manager: Shannon Rauch (Woods Hole Oceanographic Institution)


Project: Collaborative Research: Investigating the Lost City as an ultramafic urban center of the subseafloor, fueled by energy and carbon from the mantle (Lost City Limits to Life)


Abstract

Radiochemistry of serpentinite, carbonate-brucite chimney, and other solid samples from the Lost City Hydrothermal Field at the Atlantis Massif from 2018 and four previous expeditions in 2015, 2005, 2003, and 2000 (Kelley et al., 2001; Kelley et al., 2005; Früh-Green et al.,2018).

Solid samples were obtained from the 2018 Return to Lost City and four previous expeditions in 2015, 2005, 2003, and 2000 (Kelley et al., 2001; Kelley et al., 2005; Früh-Green et al., 2018). In all years except 2015, chimney and local rock materials were gathered as grab samples by the manipulators of either the ROV or Human Occupied Vehicle (HOV) Alvin and stowed in rock boxes. In 2015, rock samples were recovered with seabed rock drills as part of International Ocean Discovery Program (IODP) Expedition 357, which drilled a series of shallow boreholes across the Atlantis Massif (Früh-Green et al., 2018). In 2015 and 2018, samples were wrapped in Teflon sheeting and stored at -20°C. In previous years, samples were dried and stored at room temperature. 

The solid rock samples were analyzed for uranium (Ur) and thorium (Thr) concentrations by a Thermo Element 2 inductively coupled plasma mass spectrometer (ICP-MS). Approximately 40 mg of sample and approximately 80 mg of an Sm-Nd (145Nd) spike were weighed into a Teflon vial. The samples were digested for four days in a 4 mL dissolution mixture (3:1 concentrated HF: concentrated HNO3) in a closed beaker at 100°C. The digest was dried, 1 mL of concentrated HNO3 added, and the sample dried again. This was repeated three times. The digestion was brought into solution with 2.2 mL of 7N HNO3 and 4.8 mL of water and stored overnight. The contents were transferred to a 50 mL tube and diluted with an additional 33 mL of water. A 1:1 dilution (1 mL of sample and 1 ml of 2% HNO3) was distributed into 4 mL omnivials, and the samples were analyzed by ICP-MS.

Analyses of Ra in the solid samples (Rar) were conducted on seven carbonates, 19 serpentinites, four gabbro. The carbonates were crushed with a mortar and pestle while the other rocks were crushed with an impact mortar. An aliquot of dry, crushed sample (2 – 10 g) was then measured for 227Ac, 226Ra, 228Ra and 228Th via gamma spectrometry.


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Related Publications

Results

Moore, W. S., Frankle, J. D., Benitez‐Nelson, C. R., Früh‐Green, G. L., & Lang, S. Q. (2021). Activities of 223-Ra and 226-Ra in Fluids From the Lost City Hydrothermal Field Require Short Fluid Residence Times. Journal of Geophysical Research: Oceans, 126(12). Portico. https://doi.org/10.1029/2021jc017886
Methods

Früh-Green, G. L., Orcutt, B. N., Rouméjon, S., Lilley, M. D., Morono, Y., Cotterill, C., … Bilenker, L. (2018). Magmatism, serpentinization and life: Insights through drilling the Atlantis Massif (IODP Expedition 357). Lithos, 323, 137–155. doi:10.1016/j.lithos.2018.09.012
Methods

Kelley, D. S., Karson, J. A., Blackman, D. K., Früh-Green, G. L., Butterfield, D. A., … Rivizzigno, P. (2001). An off-axis hydrothermal vent field near the Mid-Atlantic Ridge at 30° N. Nature, 412(6843), 145–149. doi:10.1038/35084000
Methods

Kelley, D. S., Karson, J. A., Früh-Green, G. L., Yoerger, D. R., Shank, T. M., Butterfield, D. A., … Sylva, S. P. (2005). A Serpentinite-Hosted Ecosystem: The Lost City Hydrothermal Field. Science, 307(5714), 1428–1434. doi:10.1126/science.1102556
Methods

Ludwig, K. A., Shen, C.-C., Kelley, D. S., Cheng, H., & Edwards, R. L. (2011). U–Th systematics and 230Th ages of carbonate chimneys at the Lost City Hydrothermal Field. Geochimica et Cosmochimica Acta, 75(7), 1869–1888. doi:10.1016/j.gca.2011.01.008