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2. Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba

Author

Mayfield, Kimberley K, Eisenhauer, Anton, Santiago Ramos, Danielle P, Higgins, John A, Horner, Tristan J, Auro, Maureen, Magna, Tomas, Moosdorf, Nils, Charette, Matthew A, Gonneea, Meagan Eagle, Brady, Carolyn E, Komar, Nemanja, Peucker-Ehrenbrink, Bernhard, and Paytan, Adina

Subjects
Climate Change Impacts and Adaptation, Earth Sciences, Environmental Sciences, Geochemistry, Geology, Life Below Water
Abstract

Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models.

Published
2021

4. Barium cycling in the Gulf of Aqaba.

Author

Mayfield, Kimberley K., Horner, Tristan J., Torfstein, Adi, Auro, Maureen E., Crockford, Peter W., Paytan, Adina, Dehairs, Frank, and Siebert, Christopher

Subjects
WATER masses, TRACE metals, MARINE sediments, PARTICULATE matter, METAL analysis
Abstract

The isotopic composition of barium ^[sup 138]Ba) has emerged as a powerful tracer of deep-ocean circulation, water mass provenance, and the oceanic Ba cycle. Although the δ[sup 138]Ba of water masses is primarily controlled by the balance between pelagic barite precipitation and Ba resupply from ocean circulation, questions remain regarding the isotopic offset associated with pelagic barite formation and how the resultant Ba isotope compositions are transmitted through the water column to marine sediments. To address these questions, we conducted a time series study of dissolved, particulate, and sedimentary Ba chemistry in the Gulf of Aqaba (GOA), in the northern Red Sea, from January 2015 to April 2016. These data span significant seasonal changes in hydrography, primary productivity, and aerosol deposition, revealing three principal findings. First, the dissolved Ba chemistry of the GOA is vertically uniform across the time series, largely reflecting water mass advection from the Red Sea, with mean dissolved Ba concentrations of 47.9 ± 4.7 nmol kg[sup -1] and mean δ[sup 13ί]^ = +0.55%" ± 0.07%" (±2 SD, n = 18). Second, despite significant variations in particulate matter composition and flux, the δ[sup 138]Ba of sinking particulate Ba maintained a consistent isotope composition across different depths and over time at +0.09% ± 0.06% (n = 26). Consequently, these data imply a consistent Ba isotope offset of -0.46% ± 0.10% (±2 SD) between sinking particulates and seawater. This offset is similar to those determined in previous studies and indicates that it applies to particulates formed across diverse environmental conditions. Third, barite-containing sediment samples deposited in the GOA exhibit δ[sup 13ί]^ = +0.34% ± 0.03%, which is offset by approximately +0.2% relative to sinking particles. While the specific mechanism driving this offset remains unresolved, our results highlight the importance of performing site-specific proxy validations and exercising careful site selection when applying novel paleoceanographic proxies. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Magnesium isotope fractionation processes during seafloor serpentinization and implications for serpentinite subduction.

Author

Nielsen, Sune G., Klein, Frieder, Marschall, Horst R., Pogge von Strandmann, Philip A. E., and Auro, Maureen

Subjects
SLABS (Structural geology), MAGNESIUM isotopes, CHRYSOTILE, REGOLITH, SERPENTINITE
Abstract

Studies of magnesium (Mg) isotope ratios in subduction zone lavas have revealed small but significant offsets from the mantle value with enrichments in the heavy isotopes. However, the very high concentration of Mg in the mantle contrasts with much lower concentrations in the subducted igneous crust and oceanic sediments, making these subduction components unlikely vehicles of the Mg isotope anomalies in arc lavas. Only serpentinites, which in various proportions form part of oceanic plates, have high Mg contents comparable to fresh mantle rocks, and they have thus been regarded as a potential source of exotic Mg in the source of arc magmas. In this study we analyzed serpentinite samples from different oceanic settings for their Mg isotopic compositions. The majority of samples are indistinguishable from the depleted mantle (δ26Mg=-0.24 ‰ ± 0.04 ‰) irrespective of their origin. Only a small number of seafloor-weathered serpentinites are slightly enriched in the heavy isotopes (up to δ26Mg=-0.14 ‰ ± 0.03 ‰), implying that bulk serpentinites are unlikely sources of isotopically anomalous Mg in subduction zones. We also developed a partial dissolution method in which 5 % acetic acid for 180 min was shown to fully dissolve the minerals brucite and iowaite while leaving the serpentine mineral chrysotile essentially undissolved. Partial dissolution of 11 bulk serpentinite samples revealed Mg isotopic composition of brucite (± iowaite) that is systematically ∼0.25 ‰ heavier than that of coexisting serpentine. Thus, preferential breakdown of brucite and/or iowaite in a subducted slab prior to serpentine could preferentially release isotopically heavy Mg, which could subsequently be transported into the source region of arc magmas. Such a scenario would require brucite/iowaite breakdown to occur at pressures in excess of 3 GPa and produce fluids with very high concentrations of Mg that could be transported to arc magma source regions. Whether these conditions are met in nature has yet to be experimentally investigated. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Size-fractionated major particle composition and concentrations from the US GEOTRACES north Atlantic zonal transect

Author

Lam, Phoebe J, Ohnemus, Daniel C, and Auro, Maureen E

Subjects
Particles, SPM, CaCO3, Opal, Biogenic silica, POC, Ballast, Dust, Lithogenic material
Abstract

The concentration and the major phase composition (particulate organic matter, CaCO3, opal, lithogenic matter, and iron and manganese oxyhydroxides) of marine particles is thought to determine the scavenging removal of particle-reactive TEIs. Particles are also the vector for transferring carbon from the atmosphere to the deep ocean via the biological carbon pump, and their composition may determine the efficiency and strength of this transfer. Here, we present the first full ocean depth section of size-fractionated (1–51 µm, >51 µm) suspended particulate matter (SPM) concentration and major phase composition from the US GEOTRACES North Atlantic Zonal Transect between Woods Hole, MA and Lisbon, Portugal conducted in 2010 and 2011. Several major particle features are notable in the section: intense benthic nepheloid layers were observed in the western North American margin with concentrations of SPM of up to 1648 µg/L, two to three orders of magnitude higher than surrounding waters, that were dominated by lithogenic material. A more moderate benthic nepheloid layer was also observed in the eastern Mauritanian margin (44 µg/L) that had a lower lithogenic content and, notably, significant concentrations of iron and manganese oxyhydroxides (2.5% each). An intermediate nepheloid layer reaching 102 µg/L, an order of magnitude above surrounding waters, was observed associated with the Mediterranean Outflow. Finally, there was a factor of two enhancement in SPM at the TAG hydrothermal plume due almost entirely to the addition of iron oxyhydroxides from the hydrothermal vent. We observe correlations between POC and CaCO3 in large (>51 µm) particles in the upper 2000 m, but not deeper than 2000 m, and no correlations between POC and CaCO3 at any depth in small (

Published
2014

12. The GEOTRACES Intermediate Data Product 2017

Author

Schlitzer, Reiner, Anderson, Robert F., Dodas, Elena Masferrer, Lohan, Maeve, Geibert, Walter, Tagliabue, Alessandro, Bowie, Andrew, Jeandel, Catherine, Maldonado, Maria T., Landing, William M., Cockwell, Donna, Abadie, Cyril, Abouchami, Wafa, Achterberg, Eric P., Agather, Alison, Aguliar-Islas, Ana, van Aken, Hendrik M., Andersen, Morten, Archer, Corey, Auro, Maureen, de Baar, Hein J., Baars, Oliver, Baker, Alex R., Bakker, Karel, Basak, Chandranath, Baskaran, Mark, Bates, Nicholas R., Bauch, Dorothea, van Beek, Pieter, Behrens, Melanie K., Black, Erin, Bluhm, Katrin, Bopp, Laurent, Bouman, Heather, Bowman, Katlin, Bown, Johann, Boyd, Philip, Boye, Marie, Boyle, Edward A., Branellec, Pierre, Bridgestock, Luke, Brissebrat, Guillaume, Browning, Thomas, Bruland, Kenneth W., Brumsack, Hans-Jürgen, Brzezinski, Mark, Buck, Clifton S., Buck, Kristen N., Buesseler, Ken, Bull, Abby, Butler, Edward, Cai, Pinghe, Mor, Patricia Cámara, Cardinal, Damien, Carlson, Craig, Carrasco, Gonzalo, Casacuberta, Núria, Casciotti, Karen L., Castrillejo, Maxi, Chamizo, Elena, Chance, Rosie, Charette, Matthew A., Chaves, Joaquin E., Cheng, Hai, Chever, Fanny, Christl, Marcus, Church, Thomas M., Closset, Ivia, Colman, Albert, Conway, Tim M., Cossa, Daniel, Croot, Peter, Cullen, Jay T., Cutter, Gregory A., Daniels, Chris, Dehairs, Frank, Deng, Feifei, Dieu, Huong Thi, Duggan, Brian, Dulaquais, Gabriel, Dumousseaud, Cynthia, Echegoyen-Sanz, Yolanda, Edwards, R. Lawrence, Ellwood, Michael, Fahrbach, Eberhard, Fitzsimmons, Jessica N., Russell Flegal, A., Fleisher, Martin Q., van de Flierdt, Tina, Frank, Martin, Friedrich, Jana, Fripiat, Francois, Fröllje, Henning, Galer, Stephen J.G., Gamo, Toshitaka, Ganeshram, Raja S., Garcia-Orellana, Jordi, Garcia-Solsona, Ester, Gault-Ringold, Melanie, George, Ejin, Gerringa, Loes J.A., Gilbert, Melissa, Godoy, Jose M., Goldstein, Steven L., Gonzalez, Santiago R., Grissom, Karen, Hammerschmidt, Chad, Hartman, Alison, Hassler, Christel S., Hathorne, Ed C., Hatta, Mariko, Hawco, Nicholas, Hayes, Christopher T., Heimbürger, Lars-Eric, Helgoe, Josh, Heller, Maija, Henderson, Gideon M., Henderson, Paul B., van Heuven, Steven, Ho, Peng, Horner, Tristan J., Hsieh, Yu-Te, Huang, Kuo-Fang, Humphreys, Matthew P., Isshiki, Kenji, Jacquot, Jeremy E., Janssen, David J., Jenkins, William J., John, Seth, Jones, Elizabeth M., Jones, Janice L., Kadko, David C., Kayser, Rick, Kenna, Timothy C., Khondoker, Roulin, Kim, Taejin, Kipp, Lauren, Klar, Jessica K., Klunder, Maarten, Kretschmer, Sven, Kumamoto, Yuichiro, Laan, Patrick, Labatut, Marie, Lacan, Francois, Lam, Phoebe J., Lambelet, Myriam, Lamborg, Carl H., Le Moigne, Frédéric A.C., Le Roy, Emilie, Lechtenfeld, Oliver J., Lee, Jong-Mi, Lherminier, Pascale, Little, Susan, López-Lora, Mercedes, Lu, Yanbin, Masque, Pere, Mawji, Edward, Mcclain, Charles R., Measures, Christopher, Mehic, Sanjin, Barraqueta, Jan-Lukas Menzel, van der Merwe, Pier, Middag, Rob, Mieruch, Sebastian, Milne, Angela, Minami, Tomoharu, Moffett, James W., Moncoiffe, Gwenaelle, Moore, Willard S., Morris, Paul J., Morton, Peter L., Nakaguchi, Yuzuru, Nakayama, Noriko, Niedermiller, John, Nishioka, Jun, Nishiuchi, Akira, Noble, Abigail, Obata, Hajime, Ober, Sven, Ohnemus, Daniel C., van Ooijen, Jan, O'Sullivan, Jeanette, Owens, Stephanie, Pahnke, Katharina, Paul, Maxence, Pavia, Frank, Pena, Leopoldo D., Peters, Brian, Planchon, Frederic, Planquette, Helene, Pradoux, Catherine, Puigcorbé, Viena, Quay, Paul, Queroue, Fabien, Radic, Amandine, Rauschenberg, S., Rehkämper, Mark, Rember, Robert, Remenyi, Tomas, Resing, Joseph A., Rickli, Joerg, Rigaud, Sylvain, Rijkenberg, Micha J.A., Rintoul, Stephen, Robinson, Laura F., Roca-Martí, Montserrat, Rodellas, Valenti, Roeske, Tobias, Rolison, John M., Rosenberg, Mark, Roshan, Saeed, Rutgers van der Loeff, Michiel M., Ryabenko, Evgenia, Saito, Mak A., Salt, Lesley A., Sanial, Virginie, Sarthou, Geraldine, Schallenberg, Christina, Schauer, Ursula, Scher, Howie, Schlosser, Christian, Schnetger, Bernhard, Scott, Peter, Sedwick, Peter N., Semiletov, Igor, Shelley, Rachel, Sherrell, Robert M., Shiller, Alan M., Sigman, Daniel M., Singh, Sunil Kumar, Slagter, Hans A., Slater, Emma, Smethie, William M., Snaith, Helen, Sohrin, Yoshiki, Sohst, Bettina, Sonke, Jeroen E., Speich, Sabrina, Steinfeldt, Reiner, Stewart, Gillian, Stichel, Torben, Stirling, Claudine H., Stutsman, Johnny, Swarr, Gretchen J., Swift, James H., Thomas, Alexander, Thorne, Kay, Till, Claire P., Till, Ralph, Townsend, Ashley T., Townsend, Emily, Tuerena, Robyn, Twining, Benjamin S., Vance, Derek, Velazquez, Sue, Venchiarutti, Celia, Villa-Alfageme, Maria, Vivancos, Sebastian M., Voelker, Antje H.L., Wake, Bronwyn, Warner, Mark J., Watson, Ros, van Weerlee, Evaline, Alexandra Weigand, M., Weinstein, Yishai, Weiss, Dominik, Wisotzki, Andreas, Woodward, E. Malcolm S., Wu, Jingfeng, Wu, Yingzhe, Wuttig, Kathrin, Wyatt, Neil, Xiang, Yang, Xie, Ruifang C., Xue, Zichen, Yoshikawa, Hisayuki, Zhang, Jing, Zhang, Pu, Zhao, Ye, Zheng, Linjie, Zheng, Xin-Yuan, Zieringer, Moritz, Zimmer, Louise A., Ziveri, Patrizia, Zunino, Patricia, and Zurbrick, Cheryl

Published
2018
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17. Magnesium isotope fractionation processes during seafloor serpentinization and implications for serpentinite subduction.

Author

Nielsen, Sune G., Klein, Frieder, Marschall, Horst R., Strandmann, Phillip A. E. Pogge von, and Auro, Maureen

Subjects
MAGNESIUM isotopes, SERPENTINITE, ISOTOPIC fractionation, SUBDUCTION, SUBDUCTION zones, CHRYSOTILE, REGOLITH
Abstract

Studies of magnesium (Mg) isotope ratios in subduction zone lavas have revealed small, but significant offsets from the mantle value with enrichments in the heavy isotopes. However, the very high concentration of Mg in the mantle contrasts with much lower concentrations in the subducted igneous crust and oceanic sediments, making these subduction components unlikely vehicles of the Mg isotope anomalies in arc lavas. Only serpentinites, which in various proportions form part of oceanic plates, have high Mg contents comparable to fresh mantle rocks and have thus been considered a potential source of exotic Mg in the source of arc magmas. In this study we analyzed serpentinite samples from different oceanic settings for their Mg isotopic compositions. The majority of samples are indistinguishable from the depleted mantle (δ26Mg = −0.24 ± 0.04 ‰) irrespective of their origin. Only a small number of seafloor-weathered serpentinites are slightly enriched in the heavy isotopes (up to δ26Mg = −0.14 ± 0.03 ‰), implying that bulk serpentinites are unlikely sources of isotopically anomalous Mg in subduction zones. We also developed a partial-dissolution method in which 5 % acetic acid for 180 minutes was shown to fully dissolve the minerals brucite and iowaite while leaving the serpentine mineral chrysotile essentially undissolved. Partial dissolution of 11 bulk serpentinite samples revealed a Mg isotopic composition of brucite (±iowaite) that is systematically ~0.25 ‰ heavier than that of coexisting serpentine. Thus, preferential breakdown of brucite and/or iowaite in a subducted slab prior to serpentine could preferentially release isotopically heavy Mg, which could subsequently be transported into the source region of arc magmas. Such a scenario would require brucite/iowaite breakdown to occur at pressures in excess of 3 GPa and produce fluids with very high concentrations of Mg that could be transported to arc magma source regions. Whether these conditions are met in nature has yet to be experimentally investigated. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Strong Margin Influence on the Arctic Ocean Barium Cycle Revealed by Pan‐Arctic Synthesis

Author

Whitmore, Laura M., Shiller, Alan M., Horner, Tristan J., Xiang, Yang, Auro, Maureen E., Bauch, Dorothea, Dehairs, Frank, Lam, Phoebe J., Li, Jingxuan, Maldonado, Maria T., Mears, Chantal, Newton, Robert, Pasqualini, Angelica, Planquette, Hélène, Rember, Robert, Thomas, Helmuth, Whitmore, Laura M., Shiller, Alan M., Horner, Tristan J., Xiang, Yang, Auro, Maureen E., Bauch, Dorothea, Dehairs, Frank, Lam, Phoebe J., Li, Jingxuan, Maldonado, Maria T., Mears, Chantal, Newton, Robert, Pasqualini, Angelica, Planquette, Hélène, Rember, Robert, and Thomas, Helmuth

Published
2022
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26. Strong Margin Influence on the Arctic Ocean Barium Cycle Revealed by Pan‐Arctic Synthesis

Author

Whitmore, Laura M., primary, Shiller, Alan M., additional, Horner, Tristan J., additional, Xiang, Yang, additional, Auro, Maureen E., additional, Bauch, Dorothea, additional, Dehairs, Frank, additional, Lam, Phoebe J., additional, Li, Jingxuan, additional, Maldonado, Maria T., additional, Mears, Chantal, additional, Newton, Robert, additional, Pasqualini, Angelica, additional, Planquette, Hélène, additional, Rember, Robert, additional, and Thomas, Helmuth, additional

Published
2022
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29. Fossil records of early solar irradiation and cosmolocation of the CAI factory: A reappraisal

Author

Bekaert, David V., primary, Auro, Maureen, additional, Shollenberger, Quinn R., additional, Liu, Ming-Chang, additional, Marschall, Horst, additional, Burton, Kevin W., additional, Jacobsen, Benjamin, additional, Brennecka, Gregory A., additional, MacPherson, Glenn J., additional, von Mutius, Richard, additional, Sarafian, Adam, additional, and Nielsen, Sune G., additional

Published
2021
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30. Fossil records of early solar irradiation and cosmolocation of the CAI factory: a reappraisal

Author

Bekaert, David V., Auro, Maureen E., Shollenberger, Quinn R., Liu, Ming-Chang, Marschall, Horst R., Burton, Kevin W., Jacobsen, Benjamin, Brennecka, Gregory A., MacPherson, Glenn J., von Mutius, Richard, Sarafian, Adam, Nielsen, Sune G., Bekaert, David V., Auro, Maureen E., Shollenberger, Quinn R., Liu, Ming-Chang, Marschall, Horst R., Burton, Kevin W., Jacobsen, Benjamin, Brennecka, Gregory A., MacPherson, Glenn J., von Mutius, Richard, Sarafian, Adam, and Nielsen, Sune G.

Abstract

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bekaert, D. V., Auro, M., Shollenberger, Q. R., Liu, M.-C., Marschall, H., Burton, K. W., Jacobsen, B., Brennecka, G. A., McPherson, G. J., von Mutius, R., Sarafian, A., & Nielsen, S. G. Fossil records of early solar irradiation and cosmolocation of the CAI factory: a reappraisal. Science Advances, 7(40), (2021): eabg8329, https://doi.org/10.1126/sciadv.abg8329., Calcium-aluminum–rich inclusions (CAIs) in meteorites carry crucial information about the environmental conditions of the nascent Solar System prior to planet formation. Based on models of 50V–10Be co-production by in-situ irradiation, CAIs are considered to have formed within ~0.1 AU from the proto-Sun. Here, we present vanadium (V) and strontium (Sr) isotopic co-variations in fine- and coarse-grained CAIs and demonstrate that kinetic isotope effects during partial condensation and evaporation best explain V isotope anomalies previously attributed to solar particle irradiation. We also report initial excesses of 10Be and argue that CV CAIs possess essentially a homogeneous level of 10Be, inherited during their formation. Based on numerical modeling of 50V–10Be co-production by irradiation, we show that CAI formation during protoplanetary disk build-up likely occurred at greater heliocentric distances than previously considered, up to planet-forming regions (~1AU), where solar particle fluxes were sufficiently low to avoid substantial in-situ irradiation of CAIs., This study was funded by NASA Emerging Worlds grant NNX16AD36G to S.G.N. and prepared by LLNL under contract DE-AC52-07NA27344 with release number LLNL-JRNL-819045. M.C.L acknowledges the support by the NASA grant 80NSSC20K0759. The UCLA ion microprobe facility is partially supported by a grant from the NSF Instrumentation and Facilities program.

Published
2021

31. Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba

Author

Mayfield, Kimberley K., Eisenhauer, Anton, Santiago Ramos, Danielle, Higgins, John A., Horner, Tristan J., Auro, Maureen E., Magna, Tomas, Moosdorf, Nils, Charette, Matthew A., Gonneea, Meagan E., Brady, Carolyn E., Komar, Nemanja, Peucker-Ehrenbrink, Bernhard, Paytan, Adina, Mayfield, Kimberley K., Eisenhauer, Anton, Santiago Ramos, Danielle, Higgins, John A., Horner, Tristan J., Auro, Maureen E., Magna, Tomas, Moosdorf, Nils, Charette, Matthew A., Gonneea, Meagan E., Brady, Carolyn E., Komar, Nemanja, Peucker-Ehrenbrink, Bernhard, and Paytan, Adina

Abstract

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mayfield, K. K., Eisenhauer, A., Santiago Ramos, D. P., Higgins, J. A., Horner, T. J., Auro, M., Magna, T., Moosdorf, N., Charette, M. A., Gonneea, M. E., Brady, C. E., Komar, N., Peucker-Ehrenbrink, B., & Paytan, A. Groundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba. Nature Communications, 12(1), (2021): 148-020-20248-3, doi:10.1038/s41467-020-20248-3., Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models., We thank A. Beck, H. Dulai, I. Santos, C. Benitez-Nelson, W. Moore, A. Martin, and H. Windom for sample access. We also thank A. Kolevica, A. Heuser, H. Pryer, J. Middleton, R. Franks, F. Lon, N. Slater, and O. Šebek for their laboratory and analytical assistance. This material is based upon research supported by the National Science Foundation Graduate Research Fellowship Program and an internship provided through the U.S. Geological Survey Graduate Research Internship Program (GRIP). This research was also supported by grants from: the German Academic Exchange Service (DAAD), Northern California chapter of the Achievement Rewards for College Scientists Foundation, International Association of GeoChemistry, Geological Society of America, Northern California Geological Society, Myers Trust, Friends of Long Marine Lab, and UC MEXUS (to K.K.M.). We acknowledge funding from EU-ITN Horizon project 643084 (to A.E. and T.M.) and NSF grant Award Number 1259440 (to A.P.). We also acknowledge funding from NSF grant award number OCE-1736949 (to T.J.H.). Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Published
2021

33. Strong margin influence on the Arctic Ocean barium cycle revealed by Pan-Arctic synthesis

Author

Whitmore, Laura M., primary, Shiller, Alan M., additional, Horner, Tristan J, additional, Xiang, Yang, additional, Auro, Maureen E, additional, Bauch, Dorothea, additional, Dehairs, Frank, additional, Lam, Phoebe J., additional, LI, JINGXUAN, additional, Maldonado, Maria Teresa, additional, Mears, Chantal, additional, Newton, Robert, additional, Pasqualini, Angelica, additional, Planquette, Hélène, additional, Rember, Robert, additional, and Thomas, Helmuth, additional

Published
2021
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35. Controls on barium and radium-226 distributions along GEOTRACES GP15

Author

Le Roy, Emilie, primary, Charette, Matthew, additional, Henderson, Paul, additional, Horner, Tristan, additional, Shiller, Alan, additional, Moore, Willard, additional, Casciotti, Karen, additional, van Beek, Pieter, additional, Souhaut, Marc, additional, Auro, Maureen, additional, Lawrence, Rian, additional, and Shrikumar, Avanti, additional

Published
2021
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40. The GEOTRACES Intermediate Data Product 2017

Author

50197000, 30830202, Schlitzer, Reiner, Anderson, Robert F., Dodas, Elena Masferrer, Lohan, Maeve, Geibert, Walter, Tagliabue, Alessandro, Bowie, Andrew, Jeandel, Catherine, Maldonado, Maria T., Landing, William M., Cockwell, Donna, Abadie, Cyril, Abouchami, Wafa, Achterberg, Eric P., Agather, Alison, Aguliar-Islas, Ana, van Aken, Hendrik M., Andersen, Morten, Archer, Corey, Auro, Maureen, de Baar, Hein J., Baars, Oliver, Baker, Alex R., Bakker, Karel, Basak, Chandranath, Baskaran, Mark, Bates, Nicholas R., Bauch, Dorothea, van Beek, Pieter, Behrens, Melanie K., Black, Erin, Bluhm, Katrin, Bopp, Laurent, Bouman, Heather, Bowman, Katlin, Bown, Johann, Boyd, Philip, Boye, Marie, Boyle, Edward A., Branellec, Pierre, Bridgestock, Luke, Brissebrat, Guillaume, Browning, Thomas, Bruland, Kenneth W., Brumsack, Hans-Jürgen, Brzezinski, Mark, Buck, Clifton S., Buck, Kristen N., Buesseler, Ken, Bull, Abby, Butler, Edward, Cai, Pinghe, Mor, Patricia Cámara, Cardinal, Damien, Carlson, Craig, Carrasco, Gonzalo, Casacuberta, Núria, Casciotti, Karen L., Castrillejo, Maxi, Chamizo, Elena, Chance, Rosie, Charette, Matthew A., Chaves, Joaquin E., Cheng, Hai, Chever, Fanny, Christl, Marcus, Church, Thomas M., Closset, Ivia, Colman, Albert, Conway, Tim M., Cossa, Daniel, Croot, Peter, Cullen, Jay T., Cutter, Gregory A., Daniels, Chris, Dehairs, Frank, Deng, Feifei, Dieu, Huong Thi, Duggan, Brian, Dulaquais, Gabriel, Dumousseaud, Cynthia, Echegoyen-Sanz, Yolanda, Edwards, R. Lawrence, Ellwood, Michael, Fahrbach, Eberhard, Fitzsimmons, Jessica N., Russell Flegal, A., Fleisher, Martin Q., van de Flierdt, Tina, Frank, Martin, Friedrich, Jana, Fripiat, Francois, Fröllje, Henning, Galer, Stephen J.G., Gamo, Toshitaka, Ganeshram, Raja S., Garcia-Orellana, Jordi, Garcia-Solsona, Ester, Gault-Ringold, Melanie, George, Ejin, Gerringa, Loes J.A., Gilbert, Melissa, Godoy, Jose M., Goldstein, Steven L., Gonzalez, Santiago R., Grissom, Karen, Hammerschmidt, Chad, Hartman, Alison, Hassler, Christel S., Hathorne, Ed C., Hatta, Mariko, Hawco, Nicholas, Hayes, Christopher T., Heimbürger, Lars-Eric, Helgoe, Josh, Heller, Maija, Henderson, Gideon M., Henderson, Paul B., van Heuven, Steven, Ho, Peng, Horner, Tristan J., Hsieh, Yu-Te, Huang, Kuo-Fang, Humphreys, Matthew P., Isshiki, Kenji, Jacquot, Jeremy E., Janssen, David J., Jenkins, William J., John, Seth, Jones, Elizabeth M., Jones, Janice L., Kadko, David C., Kayser, Rick, Kenna, Timothy C., Khondoker, Roulin, Kim, Taejin, Kipp, Lauren, Klar, Jessica K., Klunder, Maarten, Kretschmer, Sven, Kumamoto, Yuichiro, Laan, Patrick, Labatut, Marie, Lacan, Francois, Lam, Phoebe J., Lambelet, Myriam, Lamborg, Carl H., Le Moigne, Frédéric A.C., Le Roy, Emilie, Lechtenfeld, Oliver J., Lee, Jong-Mi, Lherminier, Pascale, Little, Susan, López-Lora, Mercedes, Lu, Yanbin, Masque, Pere, Mawji, Edward, Mcclain, Charles R., Measures, Christopher, Mehic, Sanjin, Barraqueta, Jan-Lukas Menzel, van der Merwe, Pier, Middag, Rob, Mieruch, Sebastian, Milne, Angela, Minami, Tomoharu, Moffett, James W., Moncoiffe, Gwenaelle, Moore, Willard S., Morris, Paul J., Morton, Peter L., Nakaguchi, Yuzuru, Nakayama, Noriko, Niedermiller, John, Nishioka, Jun, Nishiuchi, Akira, Noble, Abigail, Obata, Hajime, Ober, Sven, Ohnemus, Daniel C., van Ooijen, Jan, O'Sullivan, Jeanette, Owens, Stephanie, Pahnke, Katharina, Paul, Maxence, Pavia, Frank, Pena, Leopoldo D., Peters, Brian, Planchon, Frederic, Planquette, Helene, Pradoux, Catherine, Puigcorbé, Viena, Quay, Paul, Queroue, Fabien, Radic, Amandine, Rauschenberg, S., Rehkämper, Mark, Rember, Robert, Remenyi, Tomas, Resing, Joseph A., Rickli, Joerg, Rigaud, Sylvain, Rijkenberg, Micha J.A., Rintoul, Stephen, Robinson, Laura F., Roca-Martí, Montserrat, Rodellas, Valenti, Roeske, Tobias, Rolison, John M., Rosenberg, Mark, Roshan, Saeed, Rutgers van der Loeff, Michiel M., Ryabenko, Evgenia, Saito, Mak A., Salt, Lesley A., Sanial, Virginie, Sarthou, Geraldine, Schallenberg, Christina, Schauer, Ursula, Scher, Howie, Schlosser, Christian, Schnetger, Bernhard, Scott, Peter, Sedwick, Peter N., Semiletov, Igor, Shelley, Rachel, Sherrell, Robert M., Shiller, Alan M., Sigman, Daniel M., Singh, Sunil Kumar, Slagter, Hans A., Slater, Emma, Smethie, William M., Snaith, Helen, Sohrin, Yoshiki, Sohst, Bettina, Sonke, Jeroen E., Speich, Sabrina, Steinfeldt, Reiner, Stewart, Gillian, Stichel, Torben, Stirling, Claudine H., Stutsman, Johnny, Swarr, Gretchen J., Swift, James H., Thomas, Alexander, Thorne, Kay, Till, Claire P., Till, Ralph, Townsend, Ashley T., Townsend, Emily, Tuerena, Robyn, Twining, Benjamin S., Vance, Derek, Velazquez, Sue, Venchiarutti, Celia, Villa-Alfageme, Maria, Vivancos, Sebastian M., Voelker, Antje H.L., Wake, Bronwyn, Warner, Mark J., Watson, Ros, van Weerlee, Evaline, Alexandra Weigand, M., Weinstein, Yishai, Weiss, Dominik, Wisotzki, Andreas, Woodward, E. Malcolm S., Wu, Jingfeng, Wu, Yingzhe, Wuttig, Kathrin, Wyatt, Neil, Xiang, Yang, Xie, Ruifang C., Xue, Zichen, Yoshikawa, Hisayuki, Zhang, Jing, Zhang, Pu, Zhao, Ye, Zheng, Linjie, Zheng, Xin-Yuan, Zieringer, Moritz, Zimmer, Louise A., Ziveri, Patrizia, Zunino, Patricia, Zurbrick, Cheryl, 50197000, 30830202, Schlitzer, Reiner, Anderson, Robert F., Dodas, Elena Masferrer, Lohan, Maeve, Geibert, Walter, Tagliabue, Alessandro, Bowie, Andrew, Jeandel, Catherine, Maldonado, Maria T., Landing, William M., Cockwell, Donna, Abadie, Cyril, Abouchami, Wafa, Achterberg, Eric P., Agather, Alison, Aguliar-Islas, Ana, van Aken, Hendrik M., Andersen, Morten, Archer, Corey, Auro, Maureen, de Baar, Hein J., Baars, Oliver, Baker, Alex R., Bakker, Karel, Basak, Chandranath, Baskaran, Mark, Bates, Nicholas R., Bauch, Dorothea, van Beek, Pieter, Behrens, Melanie K., Black, Erin, Bluhm, Katrin, Bopp, Laurent, Bouman, Heather, Bowman, Katlin, Bown, Johann, Boyd, Philip, Boye, Marie, Boyle, Edward A., Branellec, Pierre, Bridgestock, Luke, Brissebrat, Guillaume, Browning, Thomas, Bruland, Kenneth W., Brumsack, Hans-Jürgen, Brzezinski, Mark, Buck, Clifton S., Buck, Kristen N., Buesseler, Ken, Bull, Abby, Butler, Edward, Cai, Pinghe, Mor, Patricia Cámara, Cardinal, Damien, Carlson, Craig, Carrasco, Gonzalo, Casacuberta, Núria, Casciotti, Karen L., Castrillejo, Maxi, Chamizo, Elena, Chance, Rosie, Charette, Matthew A., Chaves, Joaquin E., Cheng, Hai, Chever, Fanny, Christl, Marcus, Church, Thomas M., Closset, Ivia, Colman, Albert, Conway, Tim M., Cossa, Daniel, Croot, Peter, Cullen, Jay T., Cutter, Gregory A., Daniels, Chris, Dehairs, Frank, Deng, Feifei, Dieu, Huong Thi, Duggan, Brian, Dulaquais, Gabriel, Dumousseaud, Cynthia, Echegoyen-Sanz, Yolanda, Edwards, R. Lawrence, Ellwood, Michael, Fahrbach, Eberhard, Fitzsimmons, Jessica N., Russell Flegal, A., Fleisher, Martin Q., van de Flierdt, Tina, Frank, Martin, Friedrich, Jana, Fripiat, Francois, Fröllje, Henning, Galer, Stephen J.G., Gamo, Toshitaka, Ganeshram, Raja S., Garcia-Orellana, Jordi, Garcia-Solsona, Ester, Gault-Ringold, Melanie, George, Ejin, Gerringa, Loes J.A., Gilbert, Melissa, Godoy, Jose M., Goldstein, Steven L., Gonzalez, Santiago R., Grissom, Karen, Hammerschmidt, Chad, Hartman, Alison, Hassler, Christel S., Hathorne, Ed C., Hatta, Mariko, Hawco, Nicholas, Hayes, Christopher T., Heimbürger, Lars-Eric, Helgoe, Josh, Heller, Maija, Henderson, Gideon M., Henderson, Paul B., van Heuven, Steven, Ho, Peng, Horner, Tristan J., Hsieh, Yu-Te, Huang, Kuo-Fang, Humphreys, Matthew P., Isshiki, Kenji, Jacquot, Jeremy E., Janssen, David J., Jenkins, William J., John, Seth, Jones, Elizabeth M., Jones, Janice L., Kadko, David C., Kayser, Rick, Kenna, Timothy C., Khondoker, Roulin, Kim, Taejin, Kipp, Lauren, Klar, Jessica K., Klunder, Maarten, Kretschmer, Sven, Kumamoto, Yuichiro, Laan, Patrick, Labatut, Marie, Lacan, Francois, Lam, Phoebe J., Lambelet, Myriam, Lamborg, Carl H., Le Moigne, Frédéric A.C., Le Roy, Emilie, Lechtenfeld, Oliver J., Lee, Jong-Mi, Lherminier, Pascale, Little, Susan, López-Lora, Mercedes, Lu, Yanbin, Masque, Pere, Mawji, Edward, Mcclain, Charles R., Measures, Christopher, Mehic, Sanjin, Barraqueta, Jan-Lukas Menzel, van der Merwe, Pier, Middag, Rob, Mieruch, Sebastian, Milne, Angela, Minami, Tomoharu, Moffett, James W., Moncoiffe, Gwenaelle, Moore, Willard S., Morris, Paul J., Morton, Peter L., Nakaguchi, Yuzuru, Nakayama, Noriko, Niedermiller, John, Nishioka, Jun, Nishiuchi, Akira, Noble, Abigail, Obata, Hajime, Ober, Sven, Ohnemus, Daniel C., van Ooijen, Jan, O'Sullivan, Jeanette, Owens, Stephanie, Pahnke, Katharina, Paul, Maxence, Pavia, Frank, Pena, Leopoldo D., Peters, Brian, Planchon, Frederic, Planquette, Helene, Pradoux, Catherine, Puigcorbé, Viena, Quay, Paul, Queroue, Fabien, Radic, Amandine, Rauschenberg, S., Rehkämper, Mark, Rember, Robert, Remenyi, Tomas, Resing, Joseph A., Rickli, Joerg, Rigaud, Sylvain, Rijkenberg, Micha J.A., Rintoul, Stephen, Robinson, Laura F., Roca-Martí, Montserrat, Rodellas, Valenti, Roeske, Tobias, Rolison, John M., Rosenberg, Mark, Roshan, Saeed, Rutgers van der Loeff, Michiel M., Ryabenko, Evgenia, Saito, Mak A., Salt, Lesley A., Sanial, Virginie, Sarthou, Geraldine, Schallenberg, Christina, Schauer, Ursula, Scher, Howie, Schlosser, Christian, Schnetger, Bernhard, Scott, Peter, Sedwick, Peter N., Semiletov, Igor, Shelley, Rachel, Sherrell, Robert M., Shiller, Alan M., Sigman, Daniel M., Singh, Sunil Kumar, Slagter, Hans A., Slater, Emma, Smethie, William M., Snaith, Helen, Sohrin, Yoshiki, Sohst, Bettina, Sonke, Jeroen E., Speich, Sabrina, Steinfeldt, Reiner, Stewart, Gillian, Stichel, Torben, Stirling, Claudine H., Stutsman, Johnny, Swarr, Gretchen J., Swift, James H., Thomas, Alexander, Thorne, Kay, Till, Claire P., Till, Ralph, Townsend, Ashley T., Townsend, Emily, Tuerena, Robyn, Twining, Benjamin S., Vance, Derek, Velazquez, Sue, Venchiarutti, Celia, Villa-Alfageme, Maria, Vivancos, Sebastian M., Voelker, Antje H.L., Wake, Bronwyn, Warner, Mark J., Watson, Ros, van Weerlee, Evaline, Alexandra Weigand, M., Weinstein, Yishai, Weiss, Dominik, Wisotzki, Andreas, Woodward, E. Malcolm S., Wu, Jingfeng, Wu, Yingzhe, Wuttig, Kathrin, Wyatt, Neil, Xiang, Yang, Xie, Ruifang C., Xue, Zichen, Yoshikawa, Hisayuki, Zhang, Jing, Zhang, Pu, Zhao, Ye, Zheng, Linjie, Zheng, Xin-Yuan, Zieringer, Moritz, Zimmer, Louise A., Ziveri, Patrizia, Zunino, Patricia, and Zurbrick, Cheryl

Published
2018

41. Nucleosynthetic vanadium isotope heterogeneity of the early solar system recorded in chondritic meteorites

Author

Nielsen, Sune G., Auro, Maureen E., Righter, Kevin, Davis, David, Prytulak, Julie, Wu, Fei, Owens, Jeremy D., Nielsen, Sune G., Auro, Maureen E., Righter, Kevin, Davis, David, Prytulak, Julie, Wu, Fei, and Owens, Jeremy D.

Abstract

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 505 (2019): 131-140, doi:10.1016/j.epsl.2018.10.029., Vanadium (V) isotopes have been hypothesized to record irradiation processes in the early solar system through production of the minor 50V isotope. However, because V only possesses two stable isotopes it is difficult to distinguish irradiation from other processes such as stable isotope fractionation and nucleosynthetic heterogeneity that could also cause V isotope variation. Here we perform the first detailed investigation of V isotopes in ordinary and carbonaceous chondrites to investigate the origin of any variation. We also perform a three-laboratory inter-calibration for chondrites, which confirms that the different chemical separation protocols do not induce V isotope analytical artifacts as long as samples are measured using medium resolution multiple collector inductively coupled plasma mass spectrometry (MCICPMS). Vanadium isotope compositions (51V/50V) of carbonaceous chondrites correlate with previously reported nucleosynthetically derived excesses in 54Cr. Both 51V and 54Cr are the most neutron-rich of their respective elements, which may suggest that pre-solar grains rich in r-process isotopes is the primary cause of the V-Cr isotope correlation. Vanadium isotope ratios of ordinary chondrite groups and Earth form a weaker correlation with 54Cr that has a different slope than observed for carbonaceous chondrites. The offset between carbonaceous and non-carbonaceous meteorites in V-Cr isotope space is similar to differences also reported for chromium, titanium, oxygen, molybdenum and ruthenium isotopes, which has been inferred to reflect the presence in the early solar system of two physically separated reservoirs. The V isotope composition of Earth is heavier than any meteorite measured to date. Therefore, V isotopes support models of Earth accretion in which a significant portion of Earth was formed from material that is not present in our meteorite collections., This study was funded by NASA Emerging Worlds grant NNX16AD36G to SGN.

Published
2018

43. Thallium isotopes as tracers of recycled materials in subduction zones : review and new data for lavas from Tonga-Kermadec and Central America

Author

Nielsen, Sune G., Prytulak, Julie, Blusztajn, Jerzy S., Shu, Yunchao, Auro, Maureen E., Regelous, Marcel, Walker, James A., Nielsen, Sune G., Prytulak, Julie, Blusztajn, Jerzy S., Shu, Yunchao, Auro, Maureen E., Regelous, Marcel, and Walker, James A.

Abstract

© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Journal of Volcanology and Geothermal Research 339 (2017): 23-40, doi:10.1016/j.jvolgeores.2017.04.024., Sediment is actively being subducted in every convergent margin worldwide. Yet, geochemical data for arc lavas from several subduction zones, such as Northern Tonga and Costa Rica have revealed either attenuated or limited evidence for sediment in their mantle source regions. Here we use thallium (Tl) isotopes to trace slab components in lavas from the Tonga-Kermadec and Central American arcs. In general, both arcs display Tl isotope data that are most compatible with addition of sediment to the sub-arc mantle from the subducting slab. This evidence is particular strong in the Tonga-Kermadec arc where pelagic clays dominate the Tl budget along the entire arc. Contributions from altered oceanic crust as well as the Louisville Seamount chain that subducts underneath Northern Tonga are not visible in Tl isotopes, which is likely due to the very high Tl concentrations found in pelagic sediments outboard of the Tonga-Kermadec arc. Lavas from Central America reveal variable and systematic Tl isotope compositions along-strike. In particular, lavas from Nicaragua are dominated by contributions from sediments, whereas Costa Rican samples reveal a significant altered oceanic crust component with little influence from sediments on thallium isotope composition. The absence of a sediment signature in Costa Rica corresponds with the Cocos Ridge and the seamount province subduction, which results in a thinner sediment cover. Furthermore, the subducted sediment is dominated by carbonates with very low Tl concentrations and, therefore, small amounts of carbonate sediment added to the mantle wedge do not contribute significantly to the overall Tl budget. A review of Tl isotope and concentration data from the Aleutians, Marianas, Tonga-Kermadec and Central American arcs demonstrate that pelagic sediments are detectable in most arcs, whereas altered oceanic crust components only become appreciable when sediment Tl concentrations are very low (e.g. carbonate) or if sediments are no long, We gratefully acknowledge funding from NSF grants EAR-1119373 and EAR-1427310 to SGN.

Published
2017

44. Improvements to 232-thorium, 230-thorium, and 231-protactinium analysis in seawater arising from GEOTRACES intercalibration

Author

Auro, Maureen E., Robinson, Laura F., Burke, Andrea, Bradtmiller, Louisa I., Fleisher, Martin Q., and Anderson, Robert F.

Subjects
Chemical oceanography
Abstract

The GEOTRACES program requires the analysis of large numbers of seawater samples for ^(232)Th, ^(230)Th, and ^(231)Pa. During the GEOTRACES international intercalibration exercise, we encountered unexpected difficulties with recovery and contamination of these isotopes, ^(232)Th in particular. Experiments were carried out to identify the source of these issues, leading to a more streamlined and efficient procedure. The two particular problems that we identified and corrected were (1) frits in columns supplied by Bio-Rad Laboratories caused loss of Th during column chemistry and (2) new batches of AG1-X8 resin supplied by Bio-Rad Laboratories released more than 100 pg of ^(232)Th during elution of sample. To improve yields and blanks, we implemented a series of changes including switching to Eichrom anion exchange resin (100-200 μm mesh) and Environmental Express columns. All Th and Pa samples were analyzed on a Neptune multi-collector inductively-coupled-plasma mass spectrometer (MC-ICP-MS) using peak hopping of ^(230)Th and ^(229)Th on the central SEM, with either ^(232)Th, ^(236)U (or both) used to monitor for beam intensity. We used in-house laboratory standards to check for machine reproducibility, and the GEOTRACES intercalibration standard to check for accuracy. Over a 1-y period, the 2 s.d. reproducibility on the GEOTRACES SW STD 2010-1 was 2.5% for ^(230)Th, 1.8% for ^(232)Th, and 4% for ^(231)Pa. The lessons learned during this intercalibration process will be of value to those analyzing U-Th-Pa and rare earth elements as part of the GEOTRACES program as well as those using U-series elements in other applications that require high yields and low blanks, such as geochronology.

Published
2012

45. Neodymium isotope analyses after combined extraction of actinide and lanthanide elements from seawater and deep-sea coral aragonite

Author

Struve, Torben, primary, van de Flierdt, Tina, additional, Robinson, Laura F., additional, Bradtmiller, Louisa I., additional, Hines, Sophia K., additional, Adkins, Jess F., additional, Lambelet, Myriam, additional, Crocket, Kirsty C., additional, Kreissig, Katharina, additional, Coles, Barry, additional, and Auro, Maureen E., additional

Published
2016
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48. Environmental and biological controls on Mg and Li in deep-sea scleractinian corals

Author

Case, David H., Robinson, Laura F., Auro, Maureen E., Gagnon, Alexander C., Case, David H., Robinson, Laura F., Auro, Maureen E., and Gagnon, Alexander C.

Abstract

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 300 (2010): 215-225, doi:10.1016/j.epsl.2010.09.029., Deep-sea scleractinian corals precipitate aragonite skeletons that provide valuable archives of past ocean conditions. During calcification biological mediation causes variability in trace metal incorporation and isotopic ratios of the aragonite such that signals caused by environmental controls can be overwhelmed. This complicates the interpretation of geochemical proxies used for paleo-reconstructions. In this study we examine the environmental controls on the Mg/Li ratio of 34 individuals from seven genera of deep-sea scleractinian corals: Desmophyllum, Balanophyllia, Caryophyllia, Enallopsammia, Flabellum, Trochocyanthus, and Lophelia. In addition we examine the distributions of Mg and Li in Desmophyllum and Balanophyllia using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Both Mg/Ca and Li/Ca ratios increased by more than a factor of 2 in the center of calcification regions compared to the outer, fibrous regions of the coral skeleton. As a result, replicate ~10 mg subsamples of coral show less variability in the Mg/Li ratio than Mg/Ca. Microscale Mg and Li results are consistent with Rayleigh-type incorporation of trace metals with additional processes dominating composition within centers of calcification. Comparison of Mg/Li to seawater properties near the site of collection shows that the ratio is not controlled by either carbonate ion or salinity. It appears that temperature is the major control on the Mg/Li ratio. For all 34 samples the temperature correlation (R2=0.62) is significantly better than for Mg/Ca (R2=0.06). For corals of the family Caryophyllidae the R2 value increases to 0.82 with the exclusion of one sample that was observed to have an altered, chalky texture. Despite this excellent correlation the scatter in the data suggests that the Mg/Li ratio of deep-sea corals cannot be used to reconstruct temperature to better than approximately ±1.6°C without better temperature control and additional calibration points on mo, Financial Support was provided by the USGS WHOI Co-operative agreement, NSF-ANT grant numbers 0636787 and 80295700 and the WHOI Ocean Life Institute. David Case was supported by the WHOI Summer Student Fellowship.

Published
2011

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