Skip to content

Research at St Andrews

Atmospheric S and lithospheric Pb in sulphides from the 2.06 Ga Phalaborwa phoscorite-carbonatite Complex, South Africa

Research output: Contribution to journalArticlepeer-review

Author(s)

Robert Bolhar, Martin J. Whitehouse, Lorenzo Milani, Nivea Magalhães, Suzanne D. Golding, Grant Bybee, Loic LeBras, Andrey Bekker

School/Research organisations

Abstract

Lead and multiple sulphur isotope compositions were measured in-situ by SIMS on sulphide minerals from phoscorites and carbonatites of the ca. 2.06 Ga Phalaborwa Complex in South Africa. Additionally, sulphide mineral separates and bulk-rock samples were analyzed with IRMS methods to confirm SIMS data. Lead isotope ratios define a trend stretching from unradiogenic to highly radiogenic ratios corresponding to a Pb–Pb regression date of 2054 ± 99 Ma. This apparent date is consistent with the timing of emplacement and thus provides an age estimate for the sulphide mineralization. The least radiogenic Pb isotope compositions overlap, and the regression line intersects, a hypothetical mixing line between MORB mantle and an upper crustal reservoir at ca. 2.1 Ga, suggesting that either a significant quantity of crustal Pb contributed to sulphide mineralization, or that sulphidic xenomelts were derived from an isotopically enriched mantle source. Sulphur isotope ratios of individual sulphide minerals obtained by SIMS are highly variable (δ34S: −15 to +15‰ V-CDT) and, importantly, reveal the contribution of pre-Great Oxidation Event (GOE) atmospheric sulphur with mass-independent isotope fractionation (Δ33S = δ33S–[(1+δ34S)0.515-1]×1000 ≠0.0‰). Mass-independent sulphur isotope fractionation is also revealed by sulphur isotope ratios measured on sulphide mineral separates (Δ33S: 0.2 to 0.7‰) and bulk rock samples (Δ33S: 0.2 to 0.4‰). Generally, the range of sulphur isotope ratios obtained with SIMS is much larger than that observed in non-SIMS data, possibly reflecting isotopic variability at the μm scale, resolvable only with microbeam measurements. Various sources and mechanisms by which supracrustal material may have been incorporated into mantle-derived carbonatite-phoscorite magmas are assessed, taking into account that geological evidence for the presence of sedimentary material available for assimilation during shallow-level magma emplacement is lacking. Given the variability in S and Pb isotopic compositions, it is inferred that pre-GOE surficial Pb and S were not derived from asthenospheric mantle contaminated with supracrustal materials. Instead, whole rock trace element compositions, in concert with published geochemical and petrological evidence, are consistent with interaction of asthenospheric, plume-derived melt with compositionally heterogeneous lithospheric mantle that was metasomatically modified by fluids and melts released from a subducting slab. Despite geochemical and geochronological similarities with the 2055 Ma Busvheld Complex, lead and sulphur isotope data for both complexes are resolvably different, pointing to distinct lithospheric mantle sources involved in sulphide mineralization.

Close

Details

Original languageEnglish
Article number115939
JournalEarth and Planetary Science Letters
Volume530
DOIs
Publication statusPublished - 15 Jan 2020

    Research areas

  • Great Oxidation Event, Lead isotopes, Magmatic sulphides, Phalaborwa Complex, Sub-continental lithospheric mantle, Sulphur isotopes

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by author

  1. Silicate melt inclusions in the new millennium: A review of recommended practices for preparation, analysis, and data presentation

    Rose-koga, E. F., Bouvier, A., Gaetani, G. A., Wallace, P. J., Allison, C. M., Andrys, J. A., Angeles De La Torre, C. A., Barth, A., Bodnar, R. J., Bracco Gartner, A. J. J., Butters, D., Castillejo, A., Chilson-parks, B., Choudhary, B. R., Cluzel, N., Cottrell, E., Daly, A., Danyushevsky, L. V., Devitre, C. L., Drignon, M. J. & 51 others, France, L., Gaborieau, M., Garcia, M. O., Gatti, E., Genske, F. S., Hartley, M. E., Hughes, E. C., Iveson, A. A., Johnson, E. R., Kagoshima, T., Katzir, Y., Kawaguchi, M., Kawamoto, T., Kelley, K. A., Koornneef, J. M., Kurz, M. D., Laubier, M., Layne, G. D., Lerner, A., Lin, K., Liu, P., Lorenzo-merino, A., Luciani, N., Magalhães, N., Marschall, H. R., Michael, P. J., Monteleone, B. D., Moore, L. R., Moussallam, Y., Muth, M., Myers, M. L., Narváez, D. F., Navon, O., Newcombe, M. E., Nichols, A. R. L., Nielsen, R. L., Pamukcu, A., Plank, T., Rasmussen, D. J., Roberge, J., Schiavi, F., Schwartz, D., Shimizu, K., Shimizu, K., Shimizu, N., Thomas, J. B., Thompson, G. T., Tucker, J. M., Ustunisik, G., Waelkens, C. & Zhou, T., 5 Jun 2021, In: Chemical Geology. 570, p. 120145

    Research output: Contribution to journalArticlepeer-review

  2. Multiple sulfur isotopes reveal a possible non-crustal source of sulfur for the Bushveld Province, southern Africa

    Magalhães, N., Farquhar, J., Bybee, G., Penniston-Dorland, S., Rumble, D., Kinnaird, J. & McCreesh, M., 1 Oct 2019, In: Geology. 47, 10, p. 982-986 5 p.

    Research output: Contribution to journalArticlepeer-review

  3. Intercomparison measurements of two 33S-enriched sulfur isotope standards

    Geng, L., Savarino, J., Caillon, N., Gautier, E., Farquhar, J., Dottin, J. W., Magalhães, N., Hattori, S., Ishino, S., Yoshida, N., Albarède, F., Albalat, E., Cartigny, P., Ono, S. & Thiemens, M. H., 1 Jun 2019, In: Journal of Analytical Atomic Spectrometry . 34, 6, p. 1263-1271 9 p.

    Research output: Contribution to journalArticlepeer-review

  4. Deep crustal source for hydrogen and helium gases in the São Francisco Basin, Minas Gerais, Brazil

    Flude, S., Warr, O., Magalhaes, N., Bordmann, V., Fleury, J-M., Trindade, R., Reis, H., Sherwood Lollar, B. & Ballentine, C., 2019, AGU Fall Meeting.

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

  5. Sulfur isotope signatures of eucrites and diogenites

    Wu, N., Farquhar, J., Dottin, J. W. & Magalhães, N., 15 Jul 2018, In: Geochimica et Cosmochimica Acta. 233, p. 1-13 13 p.

    Research output: Contribution to journalArticlepeer-review

Related by journal

  1. Earth and Planetary Science Letters (Journal)

    Chris Hawkesworth (Member of editorial board)

    19851993

    Activity: Publication peer-review and editorial work typesEditor of research journal

Related by journal

  1. Controls on boron isotopes in a cold-water coral and the cost of resilience to ocean acidification

    Gagnon, A., Gothmann, A., Branson, O., Rae, J. W. B. & Stewart, J., 15 Jan 2021, In: Earth and Planetary Science Letters. 554, 10 p., 116662.

    Research output: Contribution to journalArticlepeer-review

  2. Photochemical modelling of atmospheric oxygen levels confirms two stable states

    Gregory, B. S., Claire, M. & Rugheimer, S., 1 May 2021, In: Earth and Planetary Science Letters. 561, 12 p., 116818.

    Research output: Contribution to journalArticlepeer-review

  3. Stirred not shaken; critical evaluation of a proposed Archean meteorite impact in West Greenland

    Yakymchuk, C., Kirkland, C. L., Cavosie, A. J., Szilas, K., Hollis, J., Gardiner, N. J., Waterton, P., Steenfelt, A. & Martin, L., 1 Mar 2021, In: Earth and Planetary Science Letters. 557, 9 p., 116730.

    Research output: Contribution to journalArticlepeer-review

  4. The phases of the Moon: modelling crystallisation of the lunar magma ocean through equilibrium thermodynamics

    Johnson, T. E., Morrissey, L. J., Nemchin, A. A., Gardiner, N. J. & Snape, J. F., 15 Feb 2021, In: Earth and Planetary Science Letters. 556, 13 p., 116721.

    Research output: Contribution to journalArticlepeer-review

  5. Theoretical versus empirical secular change in zircon composition

    Kirkland, C. L., Yakymchuk, C., Olierook, H. K. H., Hartnady, M. I. H., Gardiner, N. J., Moyen, J-F., Hugh Smithies, R., Szilas, K. & Johnson, T. E., 15 Jan 2021, In: Earth and Planetary Science Letters. 554, 12 p., 116660.

    Research output: Contribution to journalArticlepeer-review

ID: 270821170

Top