Young oxygenation of the Archean Keonjhar Palaeosol, India, from 138La-138Ce chronometry
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Keywords: 138La-138Ce, GOE, oxygenation, palaeo-weathering, REE mobilisation, Keonjhar Palaeosol, Singhbhum Craton
Update: A corrigendum to this article was published on 12 March 2025.
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Abstract
Figures
 Figure 1 (a–h) Selected major and trace element ratios normalised to Al and the element/Al ratios are normalised to the corresponding element/Al of the granite protolith sample SIN17F (Tables S-1 and S-2). (i) Ce/Ce*CI values calculated after Barrat et al. (2023) (Table S-2). (Top panels) Palaeosol samples SIN17A-E from this study (digestion no. 4). (Lower panels) Data from Mukhopadhyay et al. (2014). The grey line represents the element ratio in the protolith sample SIN17F, which by definition is 1. Mukhopadhyay et al. (2014) did not provide sufficient information on outcrop location and palaeosol stratigraphy, but we assume that the authors collected the palaeosol samples from the same outcrop albeit from a different section (see text and Fig. S-1). |  Figure 2 Protolith-normalised incompatible element data for the Keonjhar palaeosol samples from this study (digestion no. 4) and data from Mukhopadhyay et al. (2014). Mukhopadhyay et al. (2014) did not provide sufficient information on outcrop location and palaeosol stratigraphy, but we assume that their samples were collected from the same outcrop albeit from a different section (see text and Fig. S-1). Both datasets are normalised to Al and the element/Al ratios are normalised to the corresponding element/Al of the granite protolith sample SIN17F (Tables S-1 and S-2). Both datasets show LREE depletion of the palaeosol relative to the protolith and La-Ce fractionation, which likely occurred during post-Archean alteration as indicated by the isotope data (Fig. 3). The two datasets display somewhat distinct element patterns in terms of REE mobility and magnitude of Ce anomalies, which is most likely due to alteration at different fluid conditions or simply less fluid alteration. |  Figure 3 Radiogenic isotope compositions of palaeosol samples SIN17A to E (blue) and protolith sample SIN17F (grey). Errorchrons and age reference lines were calculated using MS Excel and Isoplot 2.49 for MS Excel (Ludwig, 2001). Error bars show external reproducibility. See Supplementary Information for further information on calculations and isotope measurements. Plots shown are (a) 138La-138Ce, (b) 147Sm-143Nd and, for (c) 176Lu-176Hf, only age reference lines are shown. Error bars are smaller than symbol sizes for 147Sm-143Nd. |
| Figure 1 | Figure 2 | Figure 3 |
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Introduction
The evolution of complex life on Earth is closely linked to the presence of free oxygen in the atmosphere. The Great Oxidation Event (GOE) describes the first rise in free oxygen from >10−5 PAL to >10−2 PAL (Present Atmospheric Level), starting at ca. 2.45 Ga (e.g., Farquhar et al., 2007
Farquhar, J., Peters, M., Johnston, D.T., Strauss, H., Masterson, A., Wiechert, U., Kaufman, A.J. (2007) Isotopic evidence for Mesoarchean anoxia and changing atmospheric sulphur chemistry. Nature 449, 706–709. https://doi.org/10.1038/nature06202
). The source of oxygen is generally ascribed to oxygenic photosynthesis, which led to the development of local oxygen oases in the marine realm well before the GOE (e.g., Planavsky et al., 2014Planavsky, N.J., Asael, D., Hofmann, A., Reinhard, C.T., Lalonde, S.V., Knudsen, A., Wang, X., Ossa Ossa, F., Pecoits, E., Smith, A.J.B., Beukes, N.J., Bekker, A., Johnson, T.M., Konhauser, K.O., Lyons, T.W., Rouxel, O.J. (2014) Evidence for oxygenic photosynthesis half a billion years before the Great Oxidation Event. Nature Geoscience 7, 283–286. https://doi.org/10.1038/ngeo2122
). The reconstruction of oxygen levels in Earth’s atmosphere and hydrosphere through deep time is typically based on various palaeo-redox proxies in terrestrial and marine sedimentary rocks and palaeosols (e.g., Rye and Holland, 1998Rye, R., Holland, H.D. (1998) Paleosols and the evolution of atmospheric oxygen: A critical review. American Journal of Science 298, 621–672. https://doi.org/10.2475/ajs.298.8.621
; Lyons et al., 2014Lyons, T.W., Reinhard, C.T., Planavsky, N.J. (2014) The rise of oxygen in Earth’s early ocean and atmosphere. Nature 506, 307–315. https://doi.org/10.1038/nature13068
; Catling and Zahnle, 2020Catling, D.C., Zahnle, K.J. (2020) The Archean atmosphere. Science Advances 6, eaax1420. https://doi.org/10.1126/sciadv.aax1420
). In this regard, the anomalous behaviour of Ce relative to other REE provides a key palaeo-redox proxy, as Ce can be oxidised to highly insoluble Ce4+ (e.g., Tostevin, 2021Tostevin, R. (2021) Cerium Anomalies and Paleoredox. Cambridge University Press, Cambridge. https://doi.org/10.1017/9781108847223
). Accordingly, water–rock interaction under oxidising conditions leads to a decoupling of Ce4+ from the remaining REE3+. Soil horizons may show such a decoupling, with upper oxic zones showing positive Ce anomalies due to immobility of Ce4+, whereas lower, reduced soil horizons may inherit negative anomalies due to mineral authigenesis from REE3+-enriched groundwaters (e.g., Banfield and Eggleton, 1989Banfield, J.F., Eggleton, R.A. (1989) Apatite Replacement and Rare Earth Mobilization, Fractionation, and Fixation During Weathering. Clays and Clay Minerals 37, 113–127. https://doi.org/10.1346/CCMN.1989.0370202
). Therefore, Ce anomalies in palaeosols can yield information of ancient atmospheric O2 levels.One of the oldest preserved palaeosols is the ca. 3.0 Ga old Keonjhar Palaeosol from the Singhbhum Craton, India (Bandopadhyay et al., 2010
Bandopadhyay, P.C., Eriksson, P.G., Roberts, R.J. (2010) A vertic paleosol at the Archean-Proterozoic contact from the Singhbhum-Orissa craton, eastern India. Precambrian Research 177, 277–290. https://doi.org/10.1016/j.precamres.2009.12.009
; Das et al., 2012Das, M., Monalisa, S.M., Paul, A.K., Mishra, R.K., Mohanty, J.K., Pradhan, A.A., Goswami, S. (2012) Geochemistry and Petrogenesis of Pyrophyllite Deposit of Madrangjodi, Keonjhar District, Orissa. Journal of the Geological Society of India 79, 460–466. https://doi.org/10.1007/s12594-012-0070-7
; Dzombak and Sheldon, 2022Dzombak, R.M., Sheldon, N.D. (2022) Terrestrial records of weathering indicate three billion years of dynamic equilibrium. Gondwana Research 109, 376–393. https://doi.org/10.1016/j.gr.2022.05.009
), for which Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
reported the presence of negative Ce anomalies. These authors interpreted the anomalies to have formed in the Archean, at the time of pedogenesis and, therefore, serving as evidence for pre-GOE atmospheric oxygenation. However, care needs to be taken by applying palaeo-redox proxies to rocks that have potentially experienced multiple episodes of alteration, including prolonged recent surface exposure (e.g., Bonnand et al., 2020Bonnand, P., Lalonde, S.V., Boyet, M., Heubeck, C., Homann, M., Nonnotte, P., Foster, I., Konhauser, K.O., Köhler, I. (2020) Post-depositional REE mobility in a Paleoarchean banded iron formation revealed by La-Ce geochronology: A cautionary tale for signals of ancient oxygenation. Earth and Planetary Science Letters 547, 116452. https://doi.org/10.1016/j.epsl.2020.116452
). Direct dating of REE3+-Ce4+ decoupling is therefore needed. However, the application of the 138La-138Ce chronometer (Tanaka and Masuda, 1982Tanaka, T., Masuda, A. (1982) The La-Ce geochronometer: a new dating method. Nature 300, 515–518. https://doi.org/10.1038/300515a0
) has been challenging so far, and there are only few pilot studies available (e.g., Hayashi et al., 2004Hayashi, T., Tanimizu, M., Tanaka, T. (2004) Origin of negative Ce anomalies in Barberton sedimentary rocks, deduced from La–Ce and Sm–Nd isotope systematics. Precambrian Research 135, 345–357. https://doi.org/10.1016/j.precamres.2004.09.004
; Bonnand et al., 2020Bonnand, P., Lalonde, S.V., Boyet, M., Heubeck, C., Homann, M., Nonnotte, P., Foster, I., Konhauser, K.O., Köhler, I. (2020) Post-depositional REE mobility in a Paleoarchean banded iron formation revealed by La-Ce geochronology: A cautionary tale for signals of ancient oxygenation. Earth and Planetary Science Letters 547, 116452. https://doi.org/10.1016/j.epsl.2020.116452
). To better understand whether Ce anomalies in the Keonjhar Palaeosol indeed record Archean weathering, we applied 138La-138Ce chronometry to directly date the formation of the Ce anomalies. Ion exchange chromatography and measurements of La and Ce using MC-ICP-MS were performed following the protocol of Schnabel et al. (2017)Schnabel, C., Münker, C., Strub, E. (2017) La-Ce isotope measurements by multicollector-ICPMS. Journal of Analytical Atomic Spectrometry 32, 2360–2370. https://doi.org/10.1039/C7JA00256D
(see methods in the Supplementary Information for more details). To complement the information from 138La-138Ce and better infer alteration conditions in general, we also analysed major and trace elements as well as 176Lu-176Hf and 147Sm-143Nd isotope compositions for samples from the Keonjhar Palaeosol. Further information on methodology is provided in the Supplementary Information.top
The Keonjhar Palaeosol—Geological Background
The Keonjhar Palaeosol formed on top of the Keonjhar Bhaunra Granite (Tait et al., 2011
Tait, J., Zimmermann, U., Miyazaki, T., Presnyakov, S., Chang, Q., Mukhopadhyay, J., Sergeev, S. (2011) Possible juvenile Palaeoarchaean TTG magmatism in eastern India and its constraints for the evolution of the Singhbhum craton. Geological Magazine 148, 340–347. https://doi.org/10.1017/S0016756810000920
), a porphyritic feldspar-biotite granite which is part of the Singhbhum Granitoid Complex (SGC), one of the main crustal units of the Singhbhum Craton (e.g., Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
). The palaeosol formation age is constrained by the crystallisation of the granite at ca. 3.29 Ga (Tait et al., 2011Tait, J., Zimmermann, U., Miyazaki, T., Presnyakov, S., Chang, Q., Mukhopadhyay, J., Sergeev, S. (2011) Possible juvenile Palaeoarchaean TTG magmatism in eastern India and its constraints for the evolution of the Singhbhum craton. Geological Magazine 148, 340–347. https://doi.org/10.1017/S0016756810000920
) and the deposition age of the overlying quartzites at ca. 3.02 Ga (Mukhopadhyay et al., 2014Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
). As the latter is a maximum depositional age based on detrital zircons, the age of pedogenesis is poorly constrained but clearly Archean. The overlying, cross-bedded quartzites form the base of the Koira Group, which unconformably overlies the SGC (Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
). These shallow-marine quartzites represent clastic sediments that formed during craton-wide transgression of the Singhbhum Craton, associated with crustal extension (e.g., Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
). The sampled palaeosol outcrop lies within an operating quarry site that is located ca. 8 km northwest of Keonjhar (Fig. S-1). We analysed one sample representing the granitic protolith (F) and five samples (A–E) of the palaeosol profile at the palaeo-surface (0 m), and at 2 m, 4 m, 5 m, and 7 m below the palaeo-surface. More details are provided in the Supplementary Information, including coordinates and field photographs of outcrop locations in Figures S-1 and S-2, and photographs of hand specimens A–F in Figure S-3. The up to 10 m thick alteration zone is predominantly composed of quartz and pyrophyllite and subordinate muscovite, illite, orthoclase, plagioclase, chloritoid and tourmaline (Das et al., 2012Das, M., Monalisa, S.M., Paul, A.K., Mishra, R.K., Mohanty, J.K., Pradhan, A.A., Goswami, S. (2012) Geochemistry and Petrogenesis of Pyrophyllite Deposit of Madrangjodi, Keonjhar District, Orissa. Journal of the Geological Society of India 79, 460–466. https://doi.org/10.1007/s12594-012-0070-7
; Mukhopadhyay et al., 2014Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
; Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
). Alkaline elements are strongly depleted relative to Al and Ti, as well as compared to their concentrations in the protolith (Figs. 1, S-4; Bandopadhyay et al., 2010Bandopadhyay, P.C., Eriksson, P.G., Roberts, R.J. (2010) A vertic paleosol at the Archean-Proterozoic contact from the Singhbhum-Orissa craton, eastern India. Precambrian Research 177, 277–290. https://doi.org/10.1016/j.precamres.2009.12.009
; Mukhopadhyay et al., 2014Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
). In addition to the predominance of pyrophyllite, the occurrence of increasingly abundant quartz veins towards the palaeo-surface suggests hydrothermal alteration, which could have proceeded along the unconformity plane separating the former palaeosol-surface and the overlying quartzites. The presence of a foliation and evidence for shearing indicate late-stage deformation of the palaeosol (Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
).Figure 1 (a–h) Selected major and trace element ratios normalised to Al and the element/Al ratios are normalised to the corresponding element/Al of the granite protolith sample SIN17F (Tables S-1 and S-2). (i) Ce/Ce*CI values calculated after Barrat et al. (2023)
Barrat, J.-A., Bayon, G., Lalonde, S. (2023) Calculation of cerium and lanthanum anomalies in geological and environmental samples. Chemical Geology 615, 121202. https://doi.org/10.1016/j.chemgeo.2022.121202
(Table S-2). (Top panels) Palaeosol samples SIN17A-E from this study (digestion no. 4). (Lower panels) Data from Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
. The grey line represents the element ratio in the protolith sample SIN17F, which by definition is 1. Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
did not provide sufficient information on outcrop location and palaeosol stratigraphy, but we assume that the authors collected the palaeosol samples from the same outcrop albeit from a different section (see text and Fig. S-1).top
Results and Discussion
Detailed information on major and trace element concentrations, isotope data and measurement protocols are provided in the Supplementary Information. Major and trace element patterns of the soil profile are shown in Figures 1, 2, and S-4, S-5, S-6, S-7 and S-12. Because Al is regarded as a highly immobile element, we normalised elemental abundances to Al and the element/Al to the corresponding element/Al of the protolith in Figures 1, 2, S-4, S-6 and S-7. Figure S-12 also shows selected element data without any protolith-normalisation. In Figure S-6, we show normalised data for all samples and additional data from Tait et al. (2011)
Tait, J., Zimmermann, U., Miyazaki, T., Presnyakov, S., Chang, Q., Mukhopadhyay, J., Sergeev, S. (2011) Possible juvenile Palaeoarchaean TTG magmatism in eastern India and its constraints for the evolution of the Singhbhum craton. Geological Magazine 148, 340–347. https://doi.org/10.1017/S0016756810000920
for the Keonjhar Bhaunra Granite, which is compositionally very similar to our sample of the palaeosol protolith. However, we note strong compositional heterogeneity of palaeosol samples likely linked to heterogeneously distributed REE-rich accessory phases and small-scale REE redistribution within the alteration zone, which is discussed in more detail in the Supplementary Information, including additional trace element data (Figs. S-7 to S-11). Isochrons and age reference lines for the three isotope systems 138La-138Ce, 147Sm-143Nd and 176Lu-176Hf are shown in Figure 3. Lanthanum anomalies and Ce anomalies were calculated using a geometric extrapolation after Barrat et al. (2023)Barrat, J.-A., Bayon, G., Lalonde, S. (2023) Calculation of cerium and lanthanum anomalies in geological and environmental samples. Chemical Geology 615, 121202. https://doi.org/10.1016/j.chemgeo.2022.121202
(Fig. 1i, Tables S-2, S-3) and are displayed in a PAAS-normalised plot in Figure S-5 (Pourmand et al., 2012Pourmand, A., Dauphas, N., Ireland, T.J. (2012) A novel extraction chromatography and MC-ICP-MS technique for rapid analysis of REE, Sc and Y: Revising CI-chondrite and Post-Archean Australian Shale (PAAS) abundances. Chemical Geology 291, 38–54. https://doi.org/10.1016/j.chemgeo.2011.08.011
). The dataset from Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
shows remarkably strong negative Ce anomalies from Ce/Ce*CI of 0.76 up to 0.20, while our samples show somewhat smaller Ce/Ce*CI of 0.82 up to 1.21 (Fig. S-5). Minor LREE mobility of the protolith is also displayed by its composition (La/La*CI = 0.87–0.89, Ce/Ce*CI = 0.81–0.97) (Tables S-2, S-3), which may indicate that some alteration also affected the protolith in addition to the Keonjhar Palaeosol.Figure 2 Protolith-normalised incompatible element data for the Keonjhar palaeosol samples from this study (digestion no. 4) and data from Mukhopadhyay et al. (2014)
Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
. Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
did not provide sufficient information on outcrop location and palaeosol stratigraphy, but we assume that their samples were collected from the same outcrop albeit from a different section (see text and Fig. S-1). Both datasets are normalised to Al and the element/Al ratios are normalised to the corresponding element/Al of the granite protolith sample SIN17F (Tables S-1 and S-2). Both datasets show LREE depletion of the palaeosol relative to the protolith and La-Ce fractionation, which likely occurred during post-Archean alteration as indicated by the isotope data (Fig. 3). The two datasets display somewhat distinct element patterns in terms of REE mobility and magnitude of Ce anomalies, which is most likely due to alteration at different fluid conditions or simply less fluid alteration.Figure 3 Radiogenic isotope compositions of palaeosol samples SIN17A to E (blue) and protolith sample SIN17F (grey). Errorchrons and age reference lines were calculated using MS Excel and Isoplot 2.49 for MS Excel (Ludwig, 2001
Ludwig, K.R. (2001) User’s Manual for Isoplot/Ex rev. 2.49. A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center Special Publication 1a, 1–55.
). Error bars show external reproducibility. See Supplementary Information for further information on calculations and isotope measurements. Plots shown are (a) 138La-138Ce, (b) 147Sm-143Nd and, for (c) 176Lu-176Hf, only age reference lines are shown. Error bars are smaller than symbol sizes for 147Sm-143Nd.The depletion of fluid-mobile elements such as alkaline earth metals (Figs. 1, 2 and S-4) implies that they were largely removed from the palaeosol. Immobile elements such as Nb, Hf and Ti show no evidence of a significant depletion relative to Al and the protolith (Figs. 1a–c, 2, S-4). These results are in good agreement with the element mobilisation patterns in the palaeosol profile studied by Mukhopadhyay et al. (2014)
Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
(see also Figs. 1, 2 and S-4), whereby the authors interpreted these patterns to reflect palaeo-weathering. Notably, the data from Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
and our study display somewhat distinct geochemical signatures in terms of HREE mobilisation and magnitude of Ce anomalies (Figs. 1i, S-5, Tables S-2, S-3). These differences can potentially be explained by a locally different environmental setting and different fluid conditions within the alteration zone as discussed below. Unfortunately, Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
did not provide detailed information on outcrop location, and we assume that their samples reflect a different profile from the same outcrop (Fig. S-1). Therefore, we limit our discussion below to possibly similar alteration processes that affected the two palaeosol profiles, rather than putting them in a direct stratigraphic context. The dissolution of REE (and Th)-rich accessory mineral phases during alteration, such as apatite, monazite, xenotime or allanite, as indicated by Th depletion in both datasets (Fig. 2), could explain the (L)REE depletion relative to the protolith in both palaeosol profiles (e.g., Banfield and Eggleton, 1989Banfield, J.F., Eggleton, R.A. (1989) Apatite Replacement and Rare Earth Mobilization, Fractionation, and Fixation During Weathering. Clays and Clay Minerals 37, 113–127. https://doi.org/10.1346/CCMN.1989.0370202
; Braun et al., 1993Braun, J.-J., Pagel, M., Herbilln, A., Rosin, C. (1993) Mobilization and redistribution of REEs and thorium in a syenitic lateritic profile: A mass balance study. Geochimica et Cosmochimica Acta 57, 4419–4434. https://doi.org/10.1016/0016-7037(93)90492-F
). To create negative Ce anomalies, first alteration under oxidising conditions must have occurred nearby, whereby most of the Ce4+ was retained and other REE3+ may have been complexed and removed to variable extents. Thereby, positive Ce anomalies, as for example displayed by our sample SIN17D1, were similarly generated (Figs. 1i, S-5, Tables S-2, S-3). The Ce-depleted and REE-enriched fluids might have migrated to different portions of the palaeosol at different redox or pH conditions, thereby generating slightly enriched REE patterns as observed for the palaeosol profile from Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
, and negative Ce anomalies as observed for both datasets (Figs. 1i, S-5, Tables S-2, S-3). Notably, our sampled portion of the palaeosol shows a lower magnitude of negative Ce anomalies and no HREE enrichment compared to the sampled section from Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
, which is probably due to alteration at different fluid conditions or simply less fluid alteration. Based on experimental studies, selective REE mobility occurs during hydrothermal alteration, depending on prevailing pH-values and available ligands (e.g., Yongliang and Yusheng, 1991Yongliang, X., Yusheng, Z. (1991) The mobility of rare-earth elements during hydrothermal activity: A review. Chinese Journal of Geochemistry 10, 295–306. https://doi.org/10.1007/BF02841090
; Haas et al., 1995Haas, J.R., Shock, E.L., Sassani, D.C. (1995) Rare earth elements in hydrothermal systems: Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures. Geochimica et Cosmochimica Acta 59, 4329–4350. https://doi.org/10.1016/0016-7037(95)00314-P
). Therefore, considering the prevalence of pyrophyllite, and the abundance of quartz veins in the alteration zone (e.g., Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
), hydrothermal alteration likely played an important role in the alteration history of the Keonjhar Palaeosol rather than weathering-related processes. Either way, Ce oxidation requires the involvement of oxic fluids at least at some point in the alteration history.Our 138La-138Ce dating approach (Fig. 3a) yields an errorchron age of 198 ± 422 Ma. The expected 138Ce ingrowth for an Archean La-Ce fractionation event is illustrated by the 3 Ga reference line in Figure 3a, which is clearly not supported by our dataset. Rather, our samples show a narrow range in present-day 138Ce/136Ce ratios but a large spread in La/Ce ratios (from 0.2663 to 0.4538), indicating only small ingrowth of 138Ce and, therefore, likely a more recent and post-depositional fractionation of La from Ce. Even though this result neither rules out the possibility of previously formed Ce anomalies nor the influence of recent weathering, it demonstrates unambiguously that the Ce anomalies in the Keonjhar Palaeosol cannot be taken as direct evidence for an elevated Mesoarchean oxygen partial pressure, as suggested by Mukhopadhyay et al. (2014)
Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
. Rather, our finding agrees with observations arguing for post-depositional overprint of the Keonjhar Palaeosol (Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
). Furthermore, this result aligns with evidence from Hayashi et al. (2004)Hayashi, T., Tanimizu, M., Tanaka, T. (2004) Origin of negative Ce anomalies in Barberton sedimentary rocks, deduced from La–Ce and Sm–Nd isotope systematics. Precambrian Research 135, 345–357. https://doi.org/10.1016/j.precamres.2004.09.004
and Bonnand et al. (2020)Bonnand, P., Lalonde, S.V., Boyet, M., Heubeck, C., Homann, M., Nonnotte, P., Foster, I., Konhauser, K.O., Köhler, I. (2020) Post-depositional REE mobility in a Paleoarchean banded iron formation revealed by La-Ce geochronology: A cautionary tale for signals of ancient oxygenation. Earth and Planetary Science Letters 547, 116452. https://doi.org/10.1016/j.epsl.2020.116452
, also applying 138La-138Ce chronometry to date purported Archean Ce anomalies. In both studies of ∼3.2 Ga old sedimentary rocks from the Barberton Greenstone Belt, South Africa, Ce mobility was found to be linked to much later post-depositional alteration.In addition to 138La-138Ce dating, 176Lu-176Hf isotope data (Fig. 3c) yield no isochron, which also argues for REE mobilisation. As outlined in Figure 2, the 176Lu-176Hf data reflect depletion of the HREE relative to Zr-Hf. The large deviation of our 176Lu-176Hf data from the 3 Ga reference line suggests that it does not reflect Archean Lu-Hf fractionation. If we take the calculated ages at face value and assume both La-Ce and Lu-Hf were fractionated by the same process, the REE mobility could be recent to as old as Neoproterozoic in age, which is in agreement with late Mesozoic and Cenozoic alteration patterns previously reported for BIFs from the Koira Group higher up in the stratigraphy (Beukes et al., 2008
Beukes, N.J., Mukhopadhyay, J., Gutzmer, J. (2008) Genesis of High-Grade Iron Ores of the Archean Iron Ore Group around Noamundi, India. Economic Geology 103, 365–386. https://doi.org/10.2113/gsecongeo.103.2.365
). However, the modern-day 176Hf/177Hf values are unradiogenic and almost indistinguishable, only differing within 20 % from one another, and this might suggest that Lu and Hf were barely mobilised and fractionated since protolith emplacement. This is also supported by the constant Hf/Al ratios in our sampled palaeosol profile, showing hardly any evidence for element mobilisation (Fig. 1b). Compared to the other REE, Lu also shows the smallest depletion relative to the protolith (Figs. 1h and 2). The immobility of Hf and Lu could be related to residual mineral phases in the palaeosol, which are more resistant to alteration, as for example Lu and Hf bearing zircon.In addition to the clearly post-Archean alteration of 138La-138Ce, the 147Sm-143Nd system yields an isochron age of 1765 ± 180 Ma (Fig. 3b) and therefore indicates Proterozoic LREE mobility. This is in line with the elemental depletion of LREE relative to the protolith, displayed in both palaeosol datasets (Figs. 1, 2). Also, it implies that Sm-Nd and Lu-Hf (considering the similar Lu/Hf ratios to the protolith) were less fractionated by younger alteration events than La-Ce, as suggested by 138La-138Ce dating. This difference can be explained by selective LREE complexation during hydrothermal alteration events as discussed above (e.g., Yongliang and Yusheng, 1991
Yongliang, X., Yusheng, Z. (1991) The mobility of rare-earth elements during hydrothermal activity: A review. Chinese Journal of Geochemistry 10, 295–306. https://doi.org/10.1007/BF02841090
). Potentially, this is because of the immobile character of Ce4+ among the REE, which probably triggers a more pronounced fractionation of La-Ce than of Sm-Nd and Lu-Hf during alteration events.Altogether, our data indicate a complex alteration history for the Keonjhar Palaeosol, including multiple element mobilisation events and depletion of mobile major and trace elements, and REE in the palaeosol profile. This depletion is reflected in datasets from this study and Mukhopadhyay et al. (2014)
Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
, and illustrated in Figures 1, 2 and S-4. Element depletion is likely due to fluid flow along the unconformity plane separating the former palaeosol-surface and the overlying quartzites at various times in the long geological history of the succession. Clear field evidence (Hofmann et al., 2022Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
), suggesting hydrothermal overprint and later deformation of the palaeosol, in combination with geochemical evidence (Fig. 3), indicate alteration events that cannot reflect Mesoarchean palaeo-weathering conditions. Rather, our combined 147Sm-143Nd and 138La-138Ce data argue for multiple, post-Archean alteration events of the palaeosol, when LREE were mobilised and fractionated in order to generate the observed patterns. The REE patterns and negative Ce anomalies observed by Mukhopadhyay et al. (2014)Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
were likely generated then.top
Conclusions
Combined 138La-138Ce, 147Sm-143Nd and 176Lu-176Hf isotope systematics demonstrate that the Ce anomalies in the Keonjhar Palaeosol cannot be taken as evidence for an elevated Archean oxygen partial pressure. 138La-138Ce and 176Lu-176Hf analyses indicate post-Mesoproterozoic REE mobilisation, including La-Ce fractionation, during alteration of the palaeosol. The observed REE patterns and Ce anomalies in the palaeosol suggest hydrothermal alteration and alteration processes at oxidising conditions. In addition, 147Sm-143Nd measurements argue for Proterozoic alteration and LREE mobilisation. Altogether, our data indicate multiple and complex element mobilisation processes during post-Archean alteration and hydrothermal overprint of the Keonjhar Palaeosol.
top
Acknowledgements
We thank A. Katzemich, Niklas Kallnik and Timo Lange for their support in the Lab and Mario Fischer-Gödde is thanked for the maintenance of the MC-ICP-MS. We thank the editor, Maud Boyet and an anonymous reviewer for constructive reviews that substantially improved the manuscript.
Editor: Gavin Foster
top
References
Bandopadhyay, P.C., Eriksson, P.G., Roberts, R.J. (2010) A vertic paleosol at the Archean-Proterozoic contact from the Singhbhum-Orissa craton, eastern India. Precambrian Research 177, 277–290. https://doi.org/10.1016/j.precamres.2009.12.009
Show in context One of the oldest preserved palaeosols is the ca. 3.0 Ga old Keonjhar Palaeosol from the Singhbhum Craton, India (Bandopadhyay et al., 2010; Das et al., 2012; Dzombak and Sheldon, 2022), for which Mukhopadhyay et al. (2014) reported the presence of negative Ce anomalies.
View in article
Alkaline elements are strongly depleted relative to Al and Ti, as well as compared to their concentrations in the protolith (Figs. 1, S-4; Bandopadhyay et al., 2010; Mukhopadhyay et al., 2014).
View in article
Banfield, J.F., Eggleton, R.A. (1989) Apatite Replacement and Rare Earth Mobilization, Fractionation, and Fixation During Weathering. Clays and Clay Minerals 37, 113–127. https://doi.org/10.1346/CCMN.1989.0370202
Show in context Soil horizons may show such a decoupling, with upper oxic zones showing positive Ce anomalies due to immobility of Ce4+, whereas lower, reduced soil horizons may inherit negative anomalies due to mineral authigenesis from REE3+-enriched groundwaters (e.g., Banfield and Eggleton, 1989).
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The dissolution of REE (and Th)-rich accessory mineral phases during alteration, such as apatite, monazite, xenotime or allanite, as indicated by Th depletion in both datasets (Fig. 2), could explain the (L)REE depletion relative to the protolith in both palaeosol profiles (e.g., Banfield and Eggleton, 1989; Braun et al., 1993).
View in article
Barrat, J.-A., Bayon, G., Lalonde, S. (2023) Calculation of cerium and lanthanum anomalies in geological and environmental samples. Chemical Geology 615, 121202. https://doi.org/10.1016/j.chemgeo.2022.121202
Show in context (i) Ce/Ce*CI values calculated after Barrat et al. (2023) (Table S-2).
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Lanthanum anomalies and Ce anomalies were calculated using a geometric extrapolation after Barrat et al. (2023) (Fig. 1i, Tables S-2, S-3) and are displayed in a PAAS-normalised plot in Figure S-5 (Pourmand et al., 2012).
View in article
Beukes, N.J., Mukhopadhyay, J., Gutzmer, J. (2008) Genesis of High-Grade Iron Ores of the Archean Iron Ore Group around Noamundi, India. Economic Geology 103, 365–386. https://doi.org/10.2113/gsecongeo.103.2.365
Show in context If we take the calculated ages at face value and assume both La-Ce and Lu-Hf were fractionated by the same process, the REE mobility could be recent to as old as Neoproterozoic in age, which is in agreement with late Mesozoic and Cenozoic alteration patterns previously reported for BIFs from the Koira Group higher up in the stratigraphy (Beukes et al., 2008).
View in article
Bonnand, P., Lalonde, S.V., Boyet, M., Heubeck, C., Homann, M., Nonnotte, P., Foster, I., Konhauser, K.O., Köhler, I. (2020) Post-depositional REE mobility in a Paleoarchean banded iron formation revealed by La-Ce geochronology: A cautionary tale for signals of ancient oxygenation. Earth and Planetary Science Letters 547, 116452. https://doi.org/10.1016/j.epsl.2020.116452
Show in context However, care needs to be taken by applying palaeo-redox proxies to rocks that have potentially experienced multiple episodes of alteration, including prolonged recent surface exposure (e.g., Bonnand et al., 2020).
View in article
However, the application of the 138La-138Ce chronometer (Tanaka and Masuda, 1982) has been challenging so far, and there are only few pilot studies available (e.g., Hayashi et al., 2004; Bonnand et al., 2020).
View in article
Furthermore, this result aligns with evidence from Hayashi et al. (2004) and Bonnand et al. (2020), also applying 138La-138Ce chronometry to date purported Archean Ce anomalies.
View in article
Braun, J.-J., Pagel, M., Herbilln, A., Rosin, C. (1993) Mobilization and redistribution of REEs and thorium in a syenitic lateritic profile: A mass balance study. Geochimica et Cosmochimica Acta 57, 4419–4434. https://doi.org/10.1016/0016-7037(93)90492-F
Show in context The dissolution of REE (and Th)-rich accessory mineral phases during alteration, such as apatite, monazite, xenotime or allanite, as indicated by Th depletion in both datasets (Fig. 2), could explain the (L)REE depletion relative to the protolith in both palaeosol profiles (e.g., Banfield and Eggleton, 1989; Braun et al., 1993).
View in article
Catling, D.C., Zahnle, K.J. (2020) The Archean atmosphere. Science Advances 6, eaax1420. https://doi.org/10.1126/sciadv.aax1420
Show in context The reconstruction of oxygen levels in Earth’s atmosphere and hydrosphere through deep time is typically based on various palaeo-redox proxies in terrestrial and marine sedimentary rocks and palaeosols (e.g., Rye and Holland, 1998; Lyons et al., 2014; Catling and Zahnle, 2020).
View in article
Das, M., Monalisa, S.M., Paul, A.K., Mishra, R.K., Mohanty, J.K., Pradhan, A.A., Goswami, S. (2012) Geochemistry and Petrogenesis of Pyrophyllite Deposit of Madrangjodi, Keonjhar District, Orissa. Journal of the Geological Society of India 79, 460–466. https://doi.org/10.1007/s12594-012-0070-7
Show in context One of the oldest preserved palaeosols is the ca. 3.0 Ga old Keonjhar Palaeosol from the Singhbhum Craton, India (Bandopadhyay et al., 2010; Das et al., 2012; Dzombak and Sheldon, 2022), for which Mukhopadhyay et al. (2014) reported the presence of negative Ce anomalies.
View in article
The up to 10 m thick alteration zone is predominantly composed of quartz and pyrophyllite and subordinate muscovite, illite, orthoclase, plagioclase, chloritoid and tourmaline (Das et al., 2012; Mukhopadhyay et al., 2014; Hofmann et al., 2022).
View in article
Dzombak, R.M., Sheldon, N.D. (2022) Terrestrial records of weathering indicate three billion years of dynamic equilibrium. Gondwana Research 109, 376–393. https://doi.org/10.1016/j.gr.2022.05.009
Show in context One of the oldest preserved palaeosols is the ca. 3.0 Ga old Keonjhar Palaeosol from the Singhbhum Craton, India (Bandopadhyay et al., 2010; Das et al., 2012; Dzombak and Sheldon, 2022), for which Mukhopadhyay et al. (2014) reported the presence of negative Ce anomalies.
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Farquhar, J., Peters, M., Johnston, D.T., Strauss, H., Masterson, A., Wiechert, U., Kaufman, A.J. (2007) Isotopic evidence for Mesoarchean anoxia and changing atmospheric sulphur chemistry. Nature 449, 706–709. https://doi.org/10.1038/nature06202
Show in context The evolution of complex life on Earth is closely linked to the presence of free oxygen in the atmosphere. The Great Oxidation Event (GOE) describes the first rise in free oxygen from >10−5 PAL to >10−2 PAL (Present Atmospheric Level), starting at ca. 2.45 Ga (e.g., Farquhar et al., 2007).
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Haas, J.R., Shock, E.L., Sassani, D.C. (1995) Rare earth elements in hydrothermal systems: Estimates of standard partial molal thermodynamic properties of aqueous complexes of the rare earth elements at high pressures and temperatures. Geochimica et Cosmochimica Acta 59, 4329–4350. https://doi.org/10.1016/0016-7037(95)00314-P
Show in context Based on experimental studies, selective REE mobility occurs during hydrothermal alteration, depending on prevailing pH-values and available ligands (e.g., Yongliang and Yusheng, 1991; Haas et al., 1995).
View in article
Hayashi, T., Tanimizu, M., Tanaka, T. (2004) Origin of negative Ce anomalies in Barberton sedimentary rocks, deduced from La–Ce and Sm–Nd isotope systematics. Precambrian Research 135, 345–357. https://doi.org/10.1016/j.precamres.2004.09.004
Show in context However, the application of the 138La-138Ce chronometer (Tanaka and Masuda, 1982) has been challenging so far, and there are only few pilot studies available (e.g., Hayashi et al., 2004; Bonnand et al., 2020).
View in article
Furthermore, this result aligns with evidence from Hayashi et al. (2004) and Bonnand et al. (2020), also applying 138La-138Ce chronometry to date purported Archean Ce anomalies.
View in article
Hofmann, A., Jodder, J., Xie, H., Bolhar, R., Whitehouse, M., Elburg, M. (2022) The Archean geological history of the Singhbhum Craton, India – a proposal for a consistent framework of craton evolution. Earth-Science Reviews 228, 103994. https://doi.org/10.1016/j.earscirev.2022.103994
Show in context The Keonjhar Palaeosol formed on top of the Keonjhar Bhaunra Granite (Tait et al., 2011), a porphyritic feldspar-biotite granite which is part of the Singhbhum Granitoid Complex (SGC), one of the main crustal units of the Singhbhum Craton (e.g., Hofmann et al., 2022).
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The overlying, cross-bedded quartzites form the base of the Koira Group, which unconformably overlies the SGC (Hofmann et al., 2022).
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These shallow-marine quartzites represent clastic sediments that formed during craton-wide transgression of the Singhbhum Craton, associated with crustal extension (e.g., Hofmann et al., 2022).
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The up to 10 m thick alteration zone is predominantly composed of quartz and pyrophyllite and subordinate muscovite, illite, orthoclase, plagioclase, chloritoid and tourmaline (Das et al., 2012; Mukhopadhyay et al., 2014; Hofmann et al., 2022).
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The presence of a foliation and evidence for shearing indicate late-stage deformation of the palaeosol (Hofmann et al., 2022).
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Therefore, considering the prevalence of pyrophyllite, and the abundance of quartz veins in the alteration zone (e.g., Hofmann et al., 2022), hydrothermal alteration likely played an important role in the alteration history of the Keonjhar Palaeosol rather than weathering-related processes.
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Rather, our finding agrees with observations arguing for post-depositional overprint of the Keonjhar Palaeosol (Hofmann et al., 2022).
View in article
Clear field evidence (Hofmann et al., 2022), suggesting hydrothermal overprint and later deformation of the palaeosol, in combination with geochemical evidence (Fig. 3), indicate alteration events that cannot reflect Mesoarchean palaeo-weathering conditions.
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Ludwig, K.R. (2001) User’s Manual for Isoplot/Ex rev. 2.49. A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology Center Special Publication 1a, 1–55.
Show in context Errorchrons and age reference lines were calculated using MS Excel and Isoplot 2.49 for MS Excel (Ludwig, 2001).
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Lyons, T.W., Reinhard, C.T., Planavsky, N.J. (2014) The rise of oxygen in Earth’s early ocean and atmosphere. Nature 506, 307–315. https://doi.org/10.1038/nature13068
Show in context The reconstruction of oxygen levels in Earth’s atmosphere and hydrosphere through deep time is typically based on various palaeo-redox proxies in terrestrial and marine sedimentary rocks and palaeosols (e.g., Rye and Holland, 1998; Lyons et al., 2014; Catling and Zahnle, 2020).
View in article
Mukhopadhay, J., Crowley, Q.G., Ghosh, S., Gosh, G., Chakrabarti, K., Misra, B., Heron, K., Bose, S. (2014) Oxygenation of the Archean atmosphere: New paleosol constraints from eastern India. Geology 42, 923–926. https://doi.org/10.1130/G36091.1
Show in context One of the oldest preserved palaeosols is the ca. 3.0 Ga old Keonjhar Palaeosol from the Singhbhum Craton, India (Bandopadhyay et al., 2010; Das et al., 2012; Dzombak and Sheldon, 2022), for which Mukhopadhyay et al. (2014) reported the presence of negative Ce anomalies.
View in article
The palaeosol formation age is constrained by the crystallisation of the granite at ca. 3.29 Ga (Tait et al., 2011) and the deposition age of the overlying quartzites at ca. 3.02 Ga (Mukhopadhyay et al., 2014).
View in article
The up to 10 m thick alteration zone is predominantly composed of quartz and pyrophyllite and subordinate muscovite, illite, orthoclase, plagioclase, chloritoid and tourmaline (Das et al., 2012; Mukhopadhyay et al., 2014; Hofmann et al., 2022).
View in article
Alkaline elements are strongly depleted relative to Al and Ti, as well as compared to their concentrations in the protolith (Figs. 1, S-4; Bandopadhyay et al., 2010; Mukhopadhyay et al., 2014).
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(Top panels) Palaeosol samples SIN17A-E from this study (digestion no. 4). (Lower panels) Data from Mukhopadhyay et al. (2014).
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Mukhopadhyay et al. (2014) did not provide sufficient information on outcrop location and palaeosol stratigraphy, but we assume that the authors collected the palaeosol samples from the same outcrop albeit from a different section (see text and Fig. S-1).
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The dataset from Mukhopadhyay et al. (2014) shows remarkably strong negative Ce anomalies from Ce/Ce*CI of 0.76 up to 0.20, while our samples show somewhat smaller Ce/Ce*CI of 0.82 up to 1.21 (Fig. S-5).
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Protolith-normalised incompatible element data for the Keonjhar palaeosol samples from this study (digestion no. 4) and data from Mukhopadhyay et al. (2014).
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Mukhopadhyay et al. (2014) did not provide sufficient information on outcrop location and palaeosol stratigraphy, but we assume that their samples were collected from the same outcrop albeit from a different section (see text and Fig. S-1).
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These results are in good agreement with the element mobilisation patterns in the palaeosol profile studied by Mukhopadhyay et al. (2014) (see also Figs. 1, 2 and S-4), whereby the authors interpreted these patterns to reflect palaeo-weathering.
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Notably, the data from Mukhopadhyay et al. (2014) and our study display somewhat distinct geochemical signatures in terms of HREE mobilisation and magnitude of Ce anomalies (Figs. 1i, S-5, Tables S-2, S-3).
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Unfortunately, Mukhopadhyay et al. (2014) did not provide detailed information on outcrop location, and we assume that their samples reflect a different profile from the same outcrop (Fig. S-1).
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The Ce-depleted and REE-enriched fluids might have migrated to different portions of the palaeosol at different redox or pH conditions, thereby generating slightly enriched REE patterns as observed for the palaeosol profile from Mukhopadhyay et al. (2014), and negative Ce anomalies as observed for both datasets (Figs. 1i, S-5, Tables S-2, S-3).
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Notably, our sampled portion of the palaeosol shows a lower magnitude of negative Ce anomalies and no HREE enrichment compared to the sampled section from Mukhopadhyay et al. (2014), which is probably due to alteration at different fluid conditions or simply less fluid alteration.
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Even though this result neither rules out the possibility of previously formed Ce anomalies nor the influence of recent weathering, it demonstrates unambiguously that the Ce anomalies in the Keonjhar Palaeosol cannot be taken as direct evidence for an elevated Mesoarchean oxygen partial pressure, as suggested by Mukhopadhyay et al. (2014).
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This depletion is reflected in datasets from this study and Mukhopadhyay et al. (2014), and illustrated in Figures 1, 2 and S-4.
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The REE patterns and negative Ce anomalies observed by Mukhopadhyay et al. (2014) were likely generated then.
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Planavsky, N.J., Asael, D., Hofmann, A., Reinhard, C.T., Lalonde, S.V., Knudsen, A., Wang, X., Ossa Ossa, F., Pecoits, E., Smith, A.J.B., Beukes, N.J., Bekker, A., Johnson, T.M., Konhauser, K.O., Lyons, T.W., Rouxel, O.J. (2014) Evidence for oxygenic photosynthesis half a billion years before the Great Oxidation Event. Nature Geoscience 7, 283–286. https://doi.org/10.1038/ngeo2122
Show in context The source of oxygen is generally ascribed to oxygenic photosynthesis, which led to the development of local oxygen oases in the marine realm well before the GOE (e.g., Planavsky et al., 2014).
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Pourmand, A., Dauphas, N., Ireland, T.J. (2012) A novel extraction chromatography and MC-ICP-MS technique for rapid analysis of REE, Sc and Y: Revising CI-chondrite and Post-Archean Australian Shale (PAAS) abundances. Chemical Geology 291, 38–54. https://doi.org/10.1016/j.chemgeo.2011.08.011
Show in context Lanthanum anomalies and Ce anomalies were calculated using a geometric extrapolation after Barrat et al. (2023) (Fig. 1i, Tables S-2, S-3) and are displayed in a PAAS-normalised plot in Figure S-5 (Pourmand et al., 2012).
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Rye, R., Holland, H.D. (1998) Paleosols and the evolution of atmospheric oxygen: A critical review. American Journal of Science 298, 621–672. https://doi.org/10.2475/ajs.298.8.621
Show in context The reconstruction of oxygen levels in Earth’s atmosphere and hydrosphere through deep time is typically based on various palaeo-redox proxies in terrestrial and marine sedimentary rocks and palaeosols (e.g., Rye and Holland, 1998; Lyons et al., 2014; Catling and Zahnle, 2020).
View in article
Schnabel, C., Münker, C., Strub, E. (2017) La-Ce isotope measurements by multicollector-ICPMS. Journal of Analytical Atomic Spectrometry 32, 2360–2370. https://doi.org/10.1039/C7JA00256D
Show in context Ion exchange chromatography and measurements of La and Ce using MC-ICP-MS were performed following the protocol of Schnabel et al. (2017) (see methods in the Supplementary Information for more details).
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Tait, J., Zimmermann, U., Miyazaki, T., Presnyakov, S., Chang, Q., Mukhopadhyay, J., Sergeev, S. (2011) Possible juvenile Palaeoarchaean TTG magmatism in eastern India and its constraints for the evolution of the Singhbhum craton. Geological Magazine 148, 340–347. https://doi.org/10.1017/S0016756810000920
Show in context The Keonjhar Palaeosol formed on top of the Keonjhar Bhaunra Granite (Tait et al., 2011), a porphyritic feldspar-biotite granite which is part of the Singhbhum Granitoid Complex (SGC), one of the main crustal units of the Singhbhum Craton (e.g., Hofmann et al., 2022).
View in article
The palaeosol formation age is constrained by the crystallisation of the granite at ca. 3.29 Ga (Tait et al., 2011) and the deposition age of the overlying quartzites at ca. 3.02 Ga (Mukhopadhyay et al., 2014).
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In Figure S-6, we show normalised data for all samples and additional data from Tait et al. (2011) for the Keonjhar Bhaunra Granite, which is compositionally very similar to our sample of the palaeosol protolith.
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Tanaka, T., Masuda, A. (1982) The La-Ce geochronometer: a new dating method. Nature 300, 515–518. https://doi.org/10.1038/300515a0
Show in context However, the application of the 138La-138Ce chronometer (Tanaka and Masuda, 1982) has been challenging so far, and there are only few pilot studies available (e.g., Hayashi et al., 2004; Bonnand et al., 2020).
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Tostevin, R. (2021) Cerium Anomalies and Paleoredox. Cambridge University Press, Cambridge. https://doi.org/10.1017/9781108847223
Show in context In this regard, the anomalous behaviour of Ce relative to other REE provides a key palaeo-redox proxy, as Ce can be oxidised to highly insoluble Ce4+ (e.g., Tostevin, 2021).
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Yongliang, X., Yusheng, Z. (1991) The mobility of rare-earth elements during hydrothermal activity: A review. Chinese Journal of Geochemistry 10, 295–306. https://doi.org/10.1007/BF02841090
Show in context Based on experimental studies, selective REE mobility occurs during hydrothermal alteration, depending on prevailing pH-values and available ligands (e.g., Yongliang and Yusheng, 1991; Haas et al., 1995).
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This difference can be explained by selective LREE complexation during hydrothermal alteration events as discussed above (e.g., Yongliang and Yusheng, 1991).
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Supplementary Information
The Supplementary Information includes:
- Methods
- Results
- Tables S-1 to S-6
- Figures S-1 to S-12
- Supplementary Information References
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