Sr-Nd-Pb isotopes of fluids in diamond record two-stage modification of the continental lithosphere
Affiliations | Corresponding Author | Cite as | Funding information
Published by the European Association of Geochemistry
under Creative Commons License CC BY-NC-ND 4.0
Keywords: fibrous diamonds, Sr-Nd-Pb isotopes, high-density fluid (HDF), metasomatism, continental lithosphere
- Share this article
Article views:420Cumulative count of HTML views and PDF downloads.
- Download Citation
- Rights & Permissions
top
Abstract
Figures
 Figure 1 Major and trace element composition of HDF microinclusions in fibrous diamonds. (a) SiO2 + Al2O3–Na2O + K2O–MgO + FeO + CaO ternary diagram (in wt. %, on carbon- and water-free basis), showing the compositional range of HDFs in the studied diamonds (see key for sample symbols). Each datapoint represents an individual microinclusion. Data compared to the global variation between silicic, carbonatitic and saline HDF types (shaded area – Weiss and Goldstein, 2018). (b) Primitive mantle normalised (McDonough and Sun, 1995) trace element patterns of the HDFs compared to microinclusion-bearing diamonds (shaded area – Klein-BenDavid et al., 2010, 2014). White-filled symbols are data falling between LOQ and LOD (between 10× σ and 3 × σ of the TPBs), and are regarded as qualitative (see details in the Supplementary Information). |  Figure 2 Isotopic and trace element relationships of the HDFs. (a) 143Nd/144Nd vs. 87Sr/86Sr. Also plotted are the range of South African kimberlite and lamproites (Becker and Le Roex, 2006), bulk silicate Earth (BSE; Zindler and Hart, 1986), and the vector toward continental crust (CC arrow; Rudnick, 1990; Thompson et al., 2007). (b) 143Nd/144Nd vs. 147Sm/144Nd; the latter is calculated from isotope dilution data (Table S-3). (c) 143Nd/144Nd vs. primitive mantle normalised La/NbPM ratios; the inset includes diamond 516, which deviates from the general trend. Error bars represent ±2 SE and in most cases are smaller than the symbols. |  Figure 3 Relationship between Pb and Sr isotope compositions of the HDFs. 206Pb/204Pb ratios are shown in the main panel and 207Pb/204Pb ratios in the inset. Error bars represent ±2 SE, which in most cases are smaller than the symbols. |  Figure 4 Sr-Nd-Pb isotope compositions of HDF in fibrous diamonds. (a) 143Nd/144Nd vs. 87Sr/86Sr. Measured values (large coloured symbols) and initial ratios corrected for a maximum possible emplacement age of 550 Ma (small coloured symbols) are presented. Available published data for 5 diamonds from Botswana (UNK; all duplicate analyses are presented), Snap Lake (SL) and Congo (CNG) are also shown (small open symbols; Klein-BenDavid et al., 2010, 2014). The isotopic range of cratonic continental lithosphere determined on whole rock xenolith data (dotted white area - measured values, and lined shaded area – age corrected initial values, based on the PetDB database; http://www.earthchem.org/petdb), and BSE (Zindler and Hart, 1986) are presented for comparison. (b) 208Pb/204Pb vs. 206Pb/204Pb, and (c) 207Pb/204Pb vs. 206Pb/204Pb; symbols and areas as in (a). The locus of compositions that developed undisturbed from primitive-mantle lead since Earth’s formation is shown for reference (geochron; long dashed black line); the regression line through all the HDF data yields an age of 3214 ± 369 Ma (dashed orange line and 95 % confidence interval). |
| Figure 1 | Figure 2 | Figure 3 | Figure 4 |
top
Introduction
Carbon- and water-rich fluids involved in large-scale tectonic processes carry incompatible element-enriched chemical fingerprints, which are common in metasomatised mantle-derived samples (e.g., Dawson, 1984
Dawson, J.B. (1984) Contrasting Types of Upper-Mantle Metasomatism? In: Kornprobst, J. (Ed.), Developments in Petrology, 11, 289–294. https://doi.org/10.1016/B978-0-444-42274-3.50030-5
; Turner et al., 2021Turner, S., Turner, M., Bourdon, B., Cooper, K., Porcelli, D. (2021) Extremely young melt infiltration of the sub-continental lithospheric mantle. Physics of the Earth and Planetary Interiors 313, 106325. https://doi.org/10.1016/j.pepi.2019.106325
). Diamonds are a primary target for studying mantle metasomatic processes, as they form during fluid-rock interaction and often encapsulate ambient minerals and high-density fluids (HDFs; either melt or supercritical fluid). The most common HDFs are found as microinclusions in ‘fibrous diamonds’ (a fast-growing form of diamond that is usually translucent or opaque with cuboid faces; see Graphical Abstract), which vary in composition between four major types: hydrous-silicic, rich in Si, Al, K and H2O; low-Mg carbonatitic and high-Mg carbonatitic, both rich in Ca, Mg, Fe, K and CO2; and hydrous-saline, rich in Cl, K, Na and H2O (Weiss et al., 2022aWeiss, Y., Czas, J., Navon, O. (2022a) Fluid inclusions in fibrous diamonds. Reviews in Mineralogy and Geochemistry 88, 475–532. https://doi.org/10.2138/rmg.2022.88.09
). These HDFs provide the opportunity to directly examine the nature of carbon- and water-rich media in the deep Earth and constrain their varying origins (e.g., Smith et al., 2012Smith, E.M., Kopylova, M.G., Nowell, G.M., Pearson, D.G., Ryder, J. (2012) Archean mantle fluids preserved in fibrous diamonds from Wawa, Superior craton. Geology 40, 1071–1074. https://doi.org/10.1130/G33231.1
; Klein-BenDavid et al., 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
; Kempe et al., 2021Kempe, Y., Weiss, Y., Chinn, I., Navon, O. (2021) Multiple metasomatic diamond-forming events in a cooling lithosphere beneath Voorspoed, South Africa. Lithos, 106285. https://doi.org/10.1016/j.lithos.2021.106285
).Radiogenic isotopes preserve their signature during mantle processes such as melting and immiscible separation, and are therefore an important tool in tracing mantle sources. Available HDFs Sr isotope data range between 0.703 to 0.723, indicating sources ranging from ‘depleted’ oceanic mantle to old continental lithosphere (Akagi and Masuda, 1988
Akagi, T., Masuda, A. (1988) Isotopic and elemental evidence for a relationship between kimberlite and Zaire cubic diamonds. Nature 336, 665–667. https://doi.org/10.1038/336665a0
; Klein-BenDavid et al., 2010Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
; Smith et al., 2012Smith, E.M., Kopylova, M.G., Nowell, G.M., Pearson, D.G., Ryder, J. (2012) Archean mantle fluids preserved in fibrous diamonds from Wawa, Superior craton. Geology 40, 1071–1074. https://doi.org/10.1130/G33231.1
; Weiss et al., 2015Weiss, Y., McNeill, J., Pearson, D.G., Nowell, G.M., Ottley, C.J. (2015) Highly saline fluids from a subducting slab as the source for fluid-rich diamonds. Nature 524, 339–342. https://doi.org/10.1038/nature14857
). To date, only a handful of diamond HDFs have been analysed for their Nd and Pb isotope compositions (n = 5 and 3, respectively; Klein-BenDavid et al., 2010Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
), which hinders unambiguous evaluation of possible mantle sources or recycled surface materials in metasomatic events.Here, we combine major, trace element and Sr-Nd-Pb isotope compositions of a suite of 7 HDF-bearing fibrous diamonds from Canada to constrain their petrogenesis. Together with the available isotopic data of similar HDF types in diamonds from different lithospheric provinces, we investigate possible HDF origin in the context of large-scale mantle reservoirs and processes, which control the spectrum of HDF compositions and the long-term evolution of the deep carbon cycle.
top
Samples and Methods
Seven fibrous diamonds from a single source in Canada (exact origin is unknown; see Supplementary Information, Sample Description) were cut by laser to create ∼500 μm slabs, polished on both sides, and analysed for their nitrogen characteristics and microinclusion compositions. FTIR (Fourier-transform infrared) spectroscopy establishes they carry 850 to 1250 ppm nitrogen and all exclusively exhibit absorption due to nitrogen in A-centers (a neighbouring pair of substitutional N atoms; pure Type IaA spectrum). Major element compositions were determined by EPMA (Electron probe micro-analysis, Kempe et al., 2021
Kempe, Y., Weiss, Y., Chinn, I., Navon, O. (2021) Multiple metasomatic diamond-forming events in a cooling lithosphere beneath Voorspoed, South Africa. Lithos, 106285. https://doi.org/10.1016/j.lithos.2021.106285
; Weiss et al., 2022aWeiss, Y., Czas, J., Navon, O. (2022a) Fluid inclusions in fibrous diamonds. Reviews in Mineralogy and Geochemistry 88, 475–532. https://doi.org/10.2138/rmg.2022.88.09
). We used the ‘diamond-in-water’ ablation approach to prepare the samples for solution trace element analyses by ICP-MS (Inductively coupled plasma mass spectrometry) and isotope analyses by TIMS (Thermal ionisation mass spectrometry, Weiss et al., 2022bWeiss, Y., Jockusch, S., Koornneef, J.M., Elazar, O., Davies, G.R. (2022b) Laser ablation of ‘diamonds-in-water’ for trace element and isotopic composition analysis. Journal of Analytical Atomic Spectrometry 37, 1431–1441. https://doi.org/10.1039/D2JA00088A
). As total procedural blanks (TPBs) were too small for the determination of isotope compositions, all isotopic data are presented as measured values. Additional details are given in the Supplementary Information.top
High-Density Fluid (HDF) Compositions
Major element compositions of microinclusions in the studied diamonds vary from silicic to low-Mg carbonatitic HDFs and fall within the range of HDF types in fibrous diamonds globally (Fig. 1a). They display a characteristic negative correlation between SiO2 and CaO, as well as negative covariance between SiO2 and FeO. There are positive relationships between SiO2 and Al2O3 as well as CaO and P2O5. K2O is relatively uniform (Table S-1), but correlates positively with Cl and negatively with MgO. No systematic spatial (core to rim) compositional change is observed and in most cases microinclusions within a single diamond show variation ≤15 % (1σ) for SiO2 and K2O, and ≤20 % for CaO (Table S-1).
Figure 1 Major and trace element composition of HDF microinclusions in fibrous diamonds. (a) SiO2 + Al2O3–Na2O + K2O–MgO + FeO + CaO ternary diagram (in wt. %, on carbon- and water-free basis), showing the compositional range of HDFs in the studied diamonds (see key for sample symbols). Each datapoint represents an individual microinclusion. Data compared to the global variation between silicic, carbonatitic and saline HDF types (shaded area – Weiss and Goldstein, 2018
Weiss, Y., Goldstein, S.L. (2018) The involvement of diamond-forming fluids in the metasomatic ‘cocktail’ of kimberlite sources. Mineralogy and Petrology, 1–19. https://doi.org/10.1007/s00710-018-0613-8
). (b) Primitive mantle normalised (McDonough and Sun, 1995McDonough, W.F., Sun, S.S. (1995) The composition of the Earth. Chemical Geology 120, 223–253. https://doi.org/10.1016/0009-2541(94)00140-4
) trace element patterns of the HDFs compared to microinclusion-bearing diamonds (shaded area – Klein-BenDavid et al., 2010Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
). White-filled symbols are data falling between LOQ and LOD (between 10× σ and 3 × σ of the TPBs), and are regarded as qualitative (see details in the Supplementary Information).The trace element compositions of the HDFs (Table S-2) were published previously by Weiss et al. (2022b)
Weiss, Y., Jockusch, S., Koornneef, J.M., Elazar, O., Davies, G.R. (2022b) Laser ablation of ‘diamonds-in-water’ for trace element and isotopic composition analysis. Journal of Analytical Atomic Spectrometry 37, 1431–1441. https://doi.org/10.1039/D2JA00088A
. Their primitive mantle (PM) normalised patterns are mostly similar and comparable to previously analysed HDFs (Fig. 1b). They exhibit overall decreasing levels from the most incompatible to compatible elements with characteristic anomalies (negative in most cases) of Rb, Nb, Sr, Zr, Hf and Ti, and trace element ratios indicating the involvement of accessory mantle phases in their formations (Weiss et al., 2013Weiss, Y., Griffin, W.L., Navon, O. (2013) Diamond-forming fluids in fibrous diamonds: The trace-element perspective. Earth and Planetary Science Letters 376, 110–125. https://doi.org/10.1016/j.epsl.2013.06.021
). There are no distinctive differences in trace element compositions between the silicic to low-Mg carbonatitic compositions; some trace element ratios show continuous variations irrespective of the major element compositional change (e.g., La/Nb, Zr/Eu; Fig. 1, 2c; Table S-2).Figure 2 Isotopic and trace element relationships of the HDFs. (a) 143Nd/144Nd vs. 87Sr/86Sr. Also plotted are the range of South African kimberlite and lamproites (Becker and Le Roex, 2006
Becker, M., Le Roex, A.P. (2006) Geochemistry of South African on- and off-craton, Group I and Group II kimberlites: Petrogenesis and source region evolution. Journal of Petrology 47, 673–703. https://doi.org/10.1093/petrology/egi089
), bulk silicate Earth (BSE; Zindler and Hart, 1986Zindler, A., Hart, S. (1986) Chemical Geodynamics. Annual Review of Earth and Planetary Sciences 14, 493–571. https://doi.org/10.1146/annurev.ea.14.050186.002425
), and the vector toward continental crust (CC arrow; Rudnick, 1990Rudnick, R.L. (1990) Nd and Sr isotopic compositions of lower-crustal xenoliths from north Queensland, Australia: Implications for Nd model ages and crustal growth processes. Chemical Geology 83, 195–208. https://doi.org/10.1016/0009-2541(90)90280-K
; Thompson et al., 2007Thompson, R.N., Riches, A.J.V., Antoshechkina, P.M., Pearson, D.G., Nowell, G.M., Ottley, C.J., Dickin, A.P., Hards, V.L., Nguno, A.-K., Niku-Paavola, V. (2007) Origin of CFB Magmatism: Multi-tiered Intracrustal Picrite–Rhyolite Magmatic Plumbing at Spitzkoppe, Western Namibia, during Early Cretaceous Etendeka Magmatism. Journal of Petrology 48, 1119–1154. https://doi.org/10.1093/petrology/egm012
). (b) 143Nd/144Nd vs. 147Sm/144Nd; the latter is calculated from isotope dilution data (Table S-3). (c) 143Nd/144Nd vs. primitive mantle normalised La/NbPM ratios; the inset includes diamond 516, which deviates from the general trend. Error bars represent ±2 SE and in most cases are smaller than the symbols.The HDF’s Sr and Nd isotope compositions vary between 87Sr/86Sr = 0.70438 ± 1 (2SE) to 0.71340 ± 3 and 143Nd/144Nd = 0.5126 ± 1 to 0.51177 ± 3 (ɛNd = −0.2 to −16.9; Fig. 2a; Table S-3). They show a general inverse Sr-Nd isotope correlation from bulk silicate Earth (BSE; Zindler and Hart, 1986
Zindler, A., Hart, S. (1986) Chemical Geodynamics. Annual Review of Earth and Planetary Sciences 14, 493–571. https://doi.org/10.1146/annurev.ea.14.050186.002425
) and South African kimberlite (Becker and Le Roex, 2006Becker, M., Le Roex, A.P. (2006) Geochemistry of South African on- and off-craton, Group I and Group II kimberlites: Petrogenesis and source region evolution. Journal of Petrology 47, 673–703. https://doi.org/10.1093/petrology/egi089
) values to more radiogenic 87Sr/86Sr and unradiogenic 143Nd/144Nd ratios, which trend through South African olivine lamproites (formerly Group II kimberlites or orangeite; Becker and Le Roex, 2006Becker, M., Le Roex, A.P. (2006) Geochemistry of South African on- and off-craton, Group I and Group II kimberlites: Petrogenesis and source region evolution. Journal of Petrology 47, 673–703. https://doi.org/10.1093/petrology/egi089
) towards the range of continental crust compositions (Rudnick, 1990Rudnick, R.L. (1990) Nd and Sr isotopic compositions of lower-crustal xenoliths from north Queensland, Australia: Implications for Nd model ages and crustal growth processes. Chemical Geology 83, 195–208. https://doi.org/10.1016/0009-2541(90)90280-K
; Thompson et al., 2007Thompson, R.N., Riches, A.J.V., Antoshechkina, P.M., Pearson, D.G., Nowell, G.M., Ottley, C.J., Dickin, A.P., Hards, V.L., Nguno, A.-K., Niku-Paavola, V. (2007) Origin of CFB Magmatism: Multi-tiered Intracrustal Picrite–Rhyolite Magmatic Plumbing at Spitzkoppe, Western Namibia, during Early Cretaceous Etendeka Magmatism. Journal of Petrology 48, 1119–1154. https://doi.org/10.1093/petrology/egm012
). 147Sm/144Nd ratios vary between 0.0669 ± 2 to 0.0970 ± 1 and show a general negative relationship with 143Nd/144Nd (Fig. 2b; Table S-3). The analysed diamond samples with a TPB contribution of <10 % for Pb (4 of 7; Table S-3), vary between 17.516 ± 2 and 18.149 ± 3 for 206Pb/204Pb, 15.53 ± 3 and 15.680 ± 3 for 207Pb/204Pb and 37.424 ± 6 and 38.412 ± 8 for 208Pb/204Pb. These Pb isotope variations are between depleted to enriched mantle components for 208Pb/204Pb vs. 206Pb/204Pb, but extend to more radiogenic 207Pb/204Pb values above the Pb mantle array (Fig. S-1; Hart et al., 1992Hart, S.R., Hauri, E.H., Oschmann, L.A., Whitehead, J.A. (1992) Mantle plumes and entrainment – isotopic evidence. Science 256, 517–520. https://doi.org/10.1126/science.256.5056.517
; Stracke, 2012Stracke, A. (2012) Earth’s heterogeneous mantle: A product of convection-driven interaction between crust and mantle. Chemical Geology 330, 274–299. https://doi.org/10.1016/j.chemgeo.2012.08.007
). They exhibit a strong positive correlation with Sr isotope compositions (Fig. 3).Figure 3 Relationship between Pb and Sr isotope compositions of the HDFs. 206Pb/204Pb ratios are shown in the main panel and 207Pb/204Pb ratios in the inset. Error bars represent ±2 SE, which in most cases are smaller than the symbols.
The samples define a broad linear negative correlation between 143Nd/144Nd and La/Nb (Fig. 2c). Similar inverse relationships are observed between 143Nd/144Nd and La/Rb or La/Zr, whereas direct relationships are observed with Sr* (Sr/√(Pr×Nd)) and Zr/Eu ratios (not shown; Tables S-2, S-3). Sr and Pb isotopes plotted against the same trace element ratios exhibit opposite correlations to those with Nd isotopes. These relationships are consistent with the general positive relationship between Sr isotopes and (La, Ba)/(Nb, Zr) ratios in HDFs (Klein-BenDavid et al., 2014
Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
). In comparison, no relationship is observed between Sr, Nd, or Pb isotopes and major element compositions; for example, HDF of silicic and low-Mg carbonatitic compositions (diamond 505 and 508) have almost identical Sr and Nd isotope ratios, whereas similar silicic HDFs (diamond 502 and 505) exhibit varying isotopic compositions (Fig. 1, 2, 3; Tables S-1, S-3). These major element-radiogenic isotope systematics are similar to the decoupling between major and trace elements of HDFs from different lithospheric provinces worldwide (Weiss et al., 2022aWeiss, Y., Czas, J., Navon, O. (2022a) Fluid inclusions in fibrous diamonds. Reviews in Mineralogy and Geochemistry 88, 475–532. https://doi.org/10.2138/rmg.2022.88.09
).Considering the concentration and unaggregated nature of nitrogen in the studied diamonds, and a likely average mantle residence temperature of ≥950 °C (Stachel and Harris, 2008
Stachel, T., Harris, J.W. (2008) The origin of cratonic diamonds — Constraints from mineral inclusions. Ore Geology Reviews 34, 5–32. https://doi.org/10.1016/j.oregeorev.2007.05.002
; Weiss et al., 2022aWeiss, Y., Czas, J., Navon, O. (2022a) Fluid inclusions in fibrous diamonds. Reviews in Mineralogy and Geochemistry 88, 475–532. https://doi.org/10.2138/rmg.2022.88.09
), their formation could take place from immediately prior to kimberlite eruption up to a maximum of 1 Ga before eruption (Taylor et al., 1996Taylor, W.R., Canil, D., Milledge, H.J. (1996) Kinetics of Ib to IaA nitrogen aggregation in diamond. Geochimica et Cosmochimica Acta 60, 4725–4733. https://doi.org/10.1016/S0016-7037(96)00302-X
). As the exact timing is unknown, a conservative correction for the isotopic composition of the HDFs is the possible range for the diamond emplacement age between 45–550 Ma, i.e. the age range of their possible Canadian host kimberlites (see Supplementary Information). Initial ratios corrected for 45 Ma are almost indistinguishable from measured values. Initial ratios based on 550 Ma are lower by 0.0005 to 0.0010 for 87Sr/86Sr compared to the measured values, 0.00024 to 0.00035 for 143Nd/144Nd, 0.009 to 0.116 for 206Pb/204Pb, 0.0005 to 0.0068 for 207Pb/204Pb, and 0.008 to 0.073 for 208Pb/204Pb (Fig. 4). The important observation, however, is that the relationships and variations between Sr, Nd and Pb isotopes and between isotopes and trace element compositions persist and all samples have relatively high 207Pb/204Pb (Figs. S1 and S2). This remains even if 1 Ga initial ratios are calculated.Figure 4 Sr-Nd-Pb isotope compositions of HDF in fibrous diamonds. (a) 143Nd/144Nd vs. 87Sr/86Sr. Measured values (large coloured symbols) and initial ratios corrected for a maximum possible emplacement age of 550 Ma (small coloured symbols) are presented. Available published data for 5 diamonds from Botswana (UNK; all duplicate analyses are presented), Snap Lake (SL) and Congo (CNG) are also shown (small open symbols; Klein-BenDavid et al., 2010
Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
). The isotopic range of cratonic continental lithosphere determined on whole rock xenolith data (dotted white area - measured values, and lined shaded area – age corrected initial values, based on the PetDB database;Zindler, A., Hart, S. (1986) Chemical Geodynamics. Annual Review of Earth and Planetary Sciences 14, 493–571. https://doi.org/10.1146/annurev.ea.14.050186.002425
) are presented for comparison. (b) 208Pb/204Pb vs. 206Pb/204Pb, and (c) 207Pb/204Pb vs. 206Pb/204Pb; symbols and areas as in (a). The locus of compositions that developed undisturbed from primitive-mantle lead since Earth’s formation is shown for reference (geochron; long dashed black line); the regression line through all the HDF data yields an age of 3214 ± 369 Ma (dashed orange line and 95 % confidence interval).top
HDF Sources
The combined Sr-Nd-Pb isotope signature is not related to radiogenic ingrowth after HDFs were encapsulated in the diamonds during formation, but rather indicates the involvement of two sources with distinct isotopic compositions. This conclusion is established by the inverse correlation on the Sm-Nd isochron diagram (Fig. 2b), the spectrum of Sr and Nd isotopes and the linear relationship between Pb and Sr isotopes that indicate mixing of different endmember components (Fig. 2a and Fig. 3). The covariations of isotopic composition and trace element ratios further support mixing of two components (e.g., Fig. 2c). Klein-BenDavid et al. (2010
Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014)Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
also argued for two-component mixing to explain the Sr isotope variations of HDFs, and suggested the involvement of convecting mantle and ancient sub-continental lithospheric mantle (SCLM). Indeed, an SCLM that experienced long-term LREE enrichment (low Sm/Nd) and increased Rb/Sr and U/Pb is required to explain the unradiogenic Nd and radiogenic Sr and Pb isotope endmember compositions of the HDFs studied here. However, the radiogenic 207Pb/204Pb values of all of these HDFs, including those with Sr-Nd isotope compositions closest to BSE values, are significantly higher than the compositions of recent ocean island basalts. This is evidence of elevated U/Pb ratios in early Earth history for the source of both endmembers, and precludes major involvement of mantle of asthenospheric origin (Fig. S-1).Figure 4a shows that the Sr and Nd isotope spectrum of the SCLM, as inferred by global whole rock xenolith data from cratons, covers the complete isotopic range of the HDFs studied here. A comparable picture is revealed for 208Pb/204Pb and 206Pb/204Pb variations, but not for 207Pb/204Pb, which reach higher values than recorded in SCLM whole-rock initial values (Fig. 4a,b). There is, however, evidence of ancient U enrichment in SCLM-derived xenoliths (Cohen et al., 1984
Cohen, R.S., O’Nions, R.K., Dawson, J.B. (1984) Isotope geochemistry of xenoliths from East Africa: Implications for development of mantle reservoirs and their interaction. Earth and Planetary Science Letters 68, 209–220. https://doi.org/10.1016/0012-821X(84)90153-5
; Davies and Lloyd, 1986Davies, G., Lloyd, F. (1986) Sub-continental lithosphere beneath Katew-Kikorongo, SW Uganda. International Kimberlite Conference: Extended Abstracts 4, no. 1, 229–231. https://doi.org/10.29173/ikc1126
) and magmas (i.e. Western Australian lamproites; Fraser et al., 1985Fraser, K.J., Hawkesworth, C.J., Erlank, A.J., Mitchell, R.H., Scott-Smith, B.H. (1985) Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites. Earth and Planetary Science Letters 76, 57–70. https://doi.org/10.1016/0012-821X(85)90148-7
) that are characterised by highly radiogenic 207Pb/204Pb at relatively unradiogenic 206Pb/204Pb compositions, some of which overlap the HDFs values.A strong connection has previously been established between hydrous/carbonated eclogite lithologies (and pyroxenites) with silicic to low-Mg carbonatitic HDF types, comparable in composition to HDFs in the present study (Weiss et al., 2022a
Weiss, Y., Czas, J., Navon, O. (2022a) Fluid inclusions in fibrous diamonds. Reviews in Mineralogy and Geochemistry 88, 475–532. https://doi.org/10.2138/rmg.2022.88.09
). The Sr-Nd-Pb isotope compositions of eclogite and pyroxenite xenoliths (occasionally diamondiferous) are extremely diverse, from highly unradiogenic to highly radiogenic values (e.g., Jacob, 2004Jacob, D. (2004) Nature and origin of eclogite xenoliths from kimberlites. Lithos 77, 295–316. https://doi.org/10.1016/j.lithos.2004.03.038
; Xu et al., 2009Xu, W.-L., Gao, S., Yang, D.-B., Pei, F.-P., Wang, Q.-H. (2009) Geochemistry of eclogite xenoliths in Mesozoic adakitic rocks from Xuzhou-Suzhou area in central China and their tectonic implications. Lithos 107, 269–280. https://doi.org/10.1016/j.lithos.2008.11.004
; Aulbach et al., 2019Aulbach, S., Heaman, L.M., Jacob, D.E., Viljoen, K.S. (2019) Ages and sources of mantle eclogites: ID-TIMS and in situ MC-ICPMS Pb-Sr isotope systematics of clinopyroxene. Chemical Geology 503, 15–28. https://doi.org/10.1016/j.chemgeo.2018.10.007
). Although there is limited available data from such xenoliths, their isotope variation overlaps most of the SCLM spectrum and HDFs (Fig. S-2). In addition, a large isotopic range was documented for eclogites from individual locations (Jacob, 2004Jacob, D. (2004) Nature and origin of eclogite xenoliths from kimberlites. Lithos 77, 295–316. https://doi.org/10.1016/j.lithos.2004.03.038
; Aulbach et al., 2019Aulbach, S., Heaman, L.M., Jacob, D.E., Viljoen, K.S. (2019) Ages and sources of mantle eclogites: ID-TIMS and in situ MC-ICPMS Pb-Sr isotope systematics of clinopyroxene. Chemical Geology 503, 15–28. https://doi.org/10.1016/j.chemgeo.2018.10.007
). Such sources for the HDF studied here can explain their silicic to low-Mg carbonatitic major element compositions and their varying radiogenic isotope signatures (Fig. 1a and Fig. 4; Table S-1 and S-3).Previously published Sr-Nd (±Pb) isotope data are limited to 5 additional microinclusion-bearing diamonds from Canada, Botswana and Congo, all with silicic to low-Mg carbonatitic HDF compositions (Klein-BenDavid et al., 2010
Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
; Timmerman et al., 2019Timmerman, S., Yeow, H., Honda, M., Howell, D., Jaques, A.L., Krebs, M.Y., Woodland, S., Pearson, D.G., Ávila, J.N., Ireland, T.R. (2019) U-Th/He systematics of fluid-rich ‘fibrous’ diamonds – Evidence for pre- and syn-kimberlite eruption ages. Chemical Geology 515, 22–36. https://doi.org/10.1016/j.chemgeo.2019.04.001
). Figure 4 shows that these HDFs overlap and expand the isotopic trends of the studied HDFs towards more unradiogenic Nd and radiogenic Sr and Pb compositions. These Sr-Nd isotope ratios overlap sediments derived from old continental crust (Goldstein and Jacobsen, 1987Goldstein, S.J., Jacobsen, S.B. (1987) The Nd and Sr isotopic systematics of river-water dissolved material: Implications for the sources of Nd and Sr in seawater. Chemical Geology: Isotope Geoscience Section 66, 245–272. https://doi.org/10.1016/0168-9622(87)90045-5
), suggesting their possible contribution to the formation of HDFs through subduction. Such a connection is consistent with the correlation between La/Nb and isotopes (Fig. 2c and Fig. 6e in Klein-BenDavid et al., 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
), implying the involvement of a recycled component, and may also explain the radiogenic 207Pb/204Pb signature of all of these HDFs (Fig. 4c, Fig. S-1 and Fig. 8 of Klein-BenDavid et al., 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
). Remarkably, the 207Pb/204Pb vs. 206Pb/204Pb composition of the HDFs define a positive trend (Fig. 4c). Klein-BenDavid et al. (2014)Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
suggested that the Pb isotope signature of the most radiogenic HDF indicates a multi-stage evolution of its source, characterised by an Archean enrichment event, which increased the U/Pb ratios (μ), followed by a more recent event that led to lower μ. Although there is no unique solution to explain the data, such a scenario fits all of the HDF data. Thus, the 207Pb/204Pb vs. 206Pb/204Pb trend may be interpreted as an age that corresponds to 3214 ± 369 Ma (Fig. 4c). However, this trend is more likely the manifestation of mixing of two isotopic endmember source components that differ in age significantly. Calculated Nd TDM model ages for the HDFs sources suggest an age range between 0.5 and 1.8 Ga (although these ages are minimum estimates because HDF formation produces LREE enrichment which reduces the model ages; Goldstein et al., 1984Goldstein, S.L., O’Nions, R.K., Hamilton, P.J. (1984) A Sm-Nd isotopic study of atmospheric dusts and particulates from major river systems. Earth and Planetary Science Letters 70, 221–236. https://doi.org/10.1016/0012-821X(84)90007-4
). The most unradiogenic HDF sample reported by Klein-BenDavid et al. (2014)Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
yields a TDM of 2.6 Ga.In summary, the relationships between isotope and trace element ratios of silicic to low Mg-carbonatitic HDFs indicate the involvement of two distinct eclogite/pyroxenite-dominated sources within the continental lithosphere: one with a relatively primitive Sr-Nd isotope composition and another with unradiogenic Nd and radiogenic Sr and Pb isotope ratios. We propose that the latter source reflects an old metasomatic event in the Canadian continental root by fluid addition from a subducting slab (most probably involving the Slave Craton in the Paleoproterozoic, ≥1.8 Ga, e.g., Wopmay collisional event). Near-solidus melting of this source during a subsequent tectono-magmatic event led to the formation of HDFs with unradiogenic Nd and radiogenic Sr and Pb isotope ratios. Simultaneous melting of a more primitive source introduced HDFs with less enriched Sr-Nd isotope signature, and mixing of the two HDF endmember components formed silicic to low-Mg carbonatitic HDFs with the observed range of Sr-Nd-Pb isotope compositions (Fig. 4). Formation of either HDF endmember in one of the sources, which percolates through and interacts with the other source, would lead to equivalent results. Either way, the HDFs’ host diamonds crystallised during this event. The relatively short mantle residence time of these diamonds, indicated by their unaggregated nitrogen, suggests that the Sr-Nd-Pb isotopic signature of the subducting component, most notably the relatively elevated 207Pb/204Pb was formed in, or was added to, the cratonic continental lithosphere long before HDF formation and inclusion in diamonds. Comparable isotope-trace element relationships in silicic- to low-Mg carbonatitic-bearing diamonds from different continents suggest that the same processes, including sediment subduction, impacted other SCLM provinces producing the source of diamond-forming fluids.
top
Acknowledgements
We thank S. Jockusch for help with the ablations of diamond-in-water, O. Elazar for help with column chemistry and Sr isotope analyses, and M. Schrauder for the donation of diamonds used in this study. We thank Graham Pearson, Emma Tomlinson and an anonymous reviewer, as well as GPL Editor Ambre Luguet for detailed and constructive reviews. Y.W. acknowledges support by ISF Grants No. 2015/18 and 779/22, NSF Grant EAR-1348045 and Europlanet 2020 RI Grant 18-EPN5-002. Europlanet 2020 RI has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 654208.
Editor: Ambre Luguet
top
References
Akagi, T., Masuda, A. (1988) Isotopic and elemental evidence for a relationship between kimberlite and Zaire cubic diamonds. Nature 336, 665–667. https://doi.org/10.1038/336665a0
Show in contextAvailable HDFs Sr isotope data range between 0.703 to 0.723, indicating sources ranging from ‘depleted’ oceanic mantle to old continental lithosphere (Akagi and Masuda, 1988; Klein-BenDavid et al., 2010, 2014; Smith et al., 2012; Weiss et al., 2015).
View in article
Aulbach, S., Heaman, L.M., Jacob, D.E., Viljoen, K.S. (2019) Ages and sources of mantle eclogites: ID-TIMS and in situ MC-ICPMS Pb-Sr isotope systematics of clinopyroxene. Chemical Geology 503, 15–28. https://doi.org/10.1016/j.chemgeo.2018.10.007
Show in contextThe Sr-Nd-Pb isotope compositions of eclogite and pyroxenite xenoliths (occasionally diamondiferous) are extremely diverse, from highly unradiogenic to highly radiogenic values (e.g., Jacob, 2004; Xu et al., 2009; Aulbach et al., 2019).
View in article
In addition, a large isotopic range was documented for eclogites from individual locations (Jacob, 2004; Aulbach et al., 2019).
View in article
Becker, M., Le Roex, A.P. (2006) Geochemistry of South African on- and off-craton, Group I and Group II kimberlites: Petrogenesis and source region evolution. Journal of Petrology 47, 673–703. https://doi.org/10.1093/petrology/egi089
Show in context Also plotted are the range of South African kimberlite and lamproites (Becker and Le Roex, 2006), bulk silicate Earth (BSE; Zindler and Hart, 1986), and the vector toward continental crust (CC arrow; Rudnick, 1990; Thompson et al., 2007).
View in article
They show a general inverse Sr-Nd isotope correlation from bulk silicate Earth (BSE; Zindler and Hart, 1986) and South African kimberlite (Becker and Le Roex, 2006) values to more radiogenic 87Sr/86Sr and unradiogenic 143Nd/144Nd ratios, which trend through South African olivine lamproites (formerly Group II kimberlites or orangeite; Becker and Le Roex, 2006) towards the range of continental crust compositions (Rudnick, 1990; Thompson et al., 2007).
View in article
Cohen, R.S., O’Nions, R.K., Dawson, J.B. (1984) Isotope geochemistry of xenoliths from East Africa: Implications for development of mantle reservoirs and their interaction. Earth and Planetary Science Letters 68, 209–220. https://doi.org/10.1016/0012-821X(84)90153-5
Show in contextThere is, however, evidence of ancient U enrichment in SCLM-derived xenoliths (Cohen et al., 1984; Davies and Lloyd, 1986) and magmas (i.e. Western Australian lamproites; Fraser et al., 1985) that are characterised by highly radiogenic 207Pb/204Pb at relatively unradiogenic 206Pb/204Pb compositions, some of which overlap the HDFs values.
View in article
Davies, G., Lloyd, F. (1986) Sub-continental lithosphere beneath Katew-Kikorongo, SW Uganda. International Kimberlite Conference: Extended Abstracts 4, no. 1, 229–231. https://doi.org/10.29173/ikc1126
Show in contextThere is, however, evidence of ancient U enrichment in SCLM-derived xenoliths (Cohen et al., 1984; Davies and Lloyd, 1986) and magmas (i.e. Western Australian lamproites; Fraser et al., 1985) that are characterised by highly radiogenic 207Pb/204Pb at relatively unradiogenic 206Pb/204Pb compositions, some of which overlap the HDFs values.
View in article
Dawson, J.B. (1984) Contrasting Types of Upper-Mantle Metasomatism? In: Kornprobst, J. (Ed.), Developments in Petrology, 11, 289–294. https://doi.org/10.1016/B978-0-444-42274-3.50030-5
Show in contextCarbon- and water-rich fluids involved in large-scale tectonic processes carry incompatible element-enriched chemical fingerprints, which are common in metasomatised mantle-derived samples (e.g., Dawson, 1984; Turner et al., 2021).
View in article
Fraser, K.J., Hawkesworth, C.J., Erlank, A.J., Mitchell, R.H., Scott-Smith, B.H. (1985) Sr, Nd and Pb isotope and minor element geochemistry of lamproites and kimberlites. Earth and Planetary Science Letters 76, 57–70. https://doi.org/10.1016/0012-821X(85)90148-7
Show in contextThere is, however, evidence of ancient U enrichment in SCLM-derived xenoliths (Cohen et al., 1984; Davies and Lloyd, 1986) and magmas (i.e. Western Australian lamproites; Fraser et al., 1985) that are characterised by highly radiogenic 207Pb/204Pb at relatively unradiogenic 206Pb/204Pb compositions, some of which overlap the HDFs values.
View in article
Goldstein, S.J., Jacobsen, S.B. (1987) The Nd and Sr isotopic systematics of river-water dissolved material: Implications for the sources of Nd and Sr in seawater. Chemical Geology: Isotope Geoscience Section 66, 245–272. https://doi.org/10.1016/0168-9622(87)90045-5
Show in contextThese Sr-Nd isotope ratios overlap sediments derived from old continental crust (Goldstein and Jacobsen, 1987), suggesting their possible contribution to the formation of HDFs through subduction. Such a connection is consistent with the correlation between La/Nb and isotopes (Fig. 2c and Fig. 6e in Klein-BenDavid et al., 2014), implying the involvement of a recycled component, and may also explain the radiogenic 207Pb/204Pb signature of all of these HDFs (Fig. 4c, Fig. S-1 and Fig. 8 of Klein-BenDavid et al., 2014).
View in article
Goldstein, S.L., O’Nions, R.K., Hamilton, P.J. (1984) A Sm-Nd isotopic study of atmospheric dusts and particulates from major river systems. Earth and Planetary Science Letters 70, 221–236. https://doi.org/10.1016/0012-821X(84)90007-4
Show in contextHowever, this trend is more likely the manifestation of mixing of two isotopic endmember source components that differ in age significantly. Calculated Nd TDM model ages for the HDFs sources suggest an age range between 0.5 and 1.8 Ga (although these ages are minimum estimates because HDF formation produces LREE enrichment which reduces the model ages; Goldstein et al., 1984).
View in article
Hart, S.R., Hauri, E.H., Oschmann, L.A., Whitehead, J.A. (1992) Mantle plumes and entrainment – isotopic evidence. Science 256, 517–520. https://doi.org/10.1126/science.256.5056.517
Show in contextThese Pb isotope variations are between depleted to enriched mantle components for 208Pb/204Pb vs. 206Pb/204Pb, but extend to more radiogenic 207Pb/204Pb values above the Pb mantle array (Fig. S-1; Hart et al., 1992; Stracke, 2012).
View in article
Jacob, D. (2004) Nature and origin of eclogite xenoliths from kimberlites. Lithos 77, 295–316. https://doi.org/10.1016/j.lithos.2004.03.038
Show in contextThe Sr-Nd-Pb isotope compositions of eclogite and pyroxenite xenoliths (occasionally diamondiferous) are extremely diverse, from highly unradiogenic to highly radiogenic values (e.g., Jacob, 2004; Xu et al., 2009; Aulbach et al., 2019).
View in article
In addition, a large isotopic range was documented for eclogites from individual locations (Jacob, 2004; Aulbach et al., 2019).
View in article
Kempe, Y., Weiss, Y., Chinn, I., Navon, O. (2021) Multiple metasomatic diamond-forming events in a cooling lithosphere beneath Voorspoed, South Africa. Lithos, 106285. https://doi.org/10.1016/j.lithos.2021.106285
Show in contextThese HDFs provide the opportunity to directly examine the nature of carbon- and water-rich media in the deep Earth and constrain their varying origins (e.g., Smith et al., 2012; Klein-BenDavid et al., 2014; Kempe et al., 2021).
View in article
Major element compositions were determined by EPMA (Electron probe micro-analysis, Kempe et al., 2021; Weiss et al., 2022a).
View in article
Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
Show in context
Available HDFs Sr isotope data range between 0.703 to 0.723, indicating sources ranging from ‘depleted’ oceanic mantle to old continental lithosphere (Akagi and Masuda, 1988; Klein-BenDavid et al., 2010, 2014; Smith et al., 2012; Weiss et al., 2015).
View in article
To date, only a handful of diamond HDFs have been analysed for their Nd and Pb isotope compositions (n = 5 and 3, respectively; Klein-BenDavid et al., 2010, 2014), which hinders unambiguous evaluation of possible mantle sources or recycled surface materials in metasomatic events.
View in article
(b) Primitive mantle normalised (McDonough and Sun, 1995) trace element patterns of the HDFs compared to microinclusion-bearing diamonds (shaded area – Klein-BenDavid et al., 2010, 2014).
View in article
Available published data for 5 diamonds from Botswana (UNK; all duplicate analyses are presented), Snap Lake (SL) and Congo (CNG) are also shown (small open symbols; Klein-BenDavid et al., 2010, 2014).
View in article
The covariations of isotopic composition and trace element ratios further support mixing of two components (e.g., Fig. 2c). Klein-BenDavid et al. (2010, 2014) also argued for two-component mixing to explain the Sr isotope variations of HDFs, and suggested the involvement of convecting mantle and ancient sub-continental lithospheric mantle (SCLM).
View in article
Previously published Sr-Nd (±Pb) isotope data are limited to 5 additional microinclusion-bearing diamonds from Canada, Botswana and Congo, all with silicic to low-Mg carbonatitic HDF compositions (Klein-BenDavid et al., 2010, 2014; Timmerman et al., 2019).
View in article
Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
Show in contextThese HDFs provide the opportunity to directly examine the nature of carbon- and water-rich media in the deep Earth and constrain their varying origins (e.g., Smith et al., 2012; Klein-BenDavid et al., 2014; Kempe et al., 2021).
View in article
Available HDFs Sr isotope data range between 0.703 to 0.723, indicating sources ranging from ‘depleted’ oceanic mantle to old continental lithosphere (Akagi and Masuda, 1988; Klein-BenDavid et al., 2010, 2014; Smith et al., 2012; Weiss et al., 2015).
View in article
To date, only a handful of diamond HDFs have been analysed for their Nd and Pb isotope compositions (n = 5 and 3, respectively; Klein-BenDavid et al., 2010, 2014), which hinders unambiguous evaluation of possible mantle sources or recycled surface materials in metasomatic events.
View in article
(b) Primitive mantle normalised (McDonough and Sun, 1995) trace element patterns of the HDFs compared to microinclusion-bearing diamonds (shaded area – Klein-BenDavid et al., 2010, 2014).
View in article
These relationships are consistent with the general positive relationship between Sr isotopes and (La, Ba)/(Nb, Zr) ratios in HDFs (Klein-BenDavid et al., 2014).
View in article
Available published data for 5 diamonds from Botswana (UNK; all duplicate analyses are presented), Snap Lake (SL) and Congo (CNG) are also shown (small open symbols; Klein-BenDavid et al., 2010, 2014).
View in article
The covariations of isotopic composition and trace element ratios further support mixing of two components (e.g., Fig. 2c). Klein-BenDavid et al. (2010, 2014) also argued for two-component mixing to explain the Sr isotope variations of HDFs, and suggested the involvement of convecting mantle and ancient sub-continental lithospheric mantle (SCLM).
View in article
Previously published Sr-Nd (±Pb) isotope data are limited to 5 additional microinclusion-bearing diamonds from Canada, Botswana and Congo, all with silicic to low-Mg carbonatitic HDF compositions (Klein-BenDavid et al., 2010, 2014; Timmerman et al., 2019).
View in article
These Sr-Nd isotope ratios overlap sediments derived from old continental crust (Goldstein and Jacobsen, 1987), suggesting their possible contribution to the formation of HDFs through subduction. Such a connection is consistent with the correlation between La/Nb and isotopes (Fig. 2c and Fig. 6e in Klein-BenDavid et al., 2014), implying the involvement of a recycled component, and may also explain the radiogenic 207Pb/204Pb signature of all of these HDFs (Fig. 4c, Fig. S-1 and Fig. 8 of Klein-BenDavid et al., 2014).
View in article
Klein-BenDavid et al. (2014) suggested that the Pb isotope signature of the most radiogenic HDF indicates a multi-stage evolution of its source, characterised by an Archean enrichment event, which increased the U/Pb ratios (μ), followed by a more recent event that led to lower μ.
View in article
The most unradiogenic HDF sample reported by Klein-BenDavid et al. (2014) yields a TDM of 2.6 Ga.
View in article
These Sr-Nd isotope ratios overlap sediments derived from old continental crust (Goldstein and Jacobsen, 1987), suggesting their possible contribution to the formation of HDFs through subduction. Such a connection is consistent with the correlation between La/Nb and isotopes (Fig. 2c and Fig. 6e in Klein-BenDavid et al., 2014), implying the involvement of a recycled component, and may also explain the radiogenic 207Pb/204Pb signature of all of these HDFs (Fig. 4c, Fig. S-1 and Fig. 8 of Klein-BenDavid et al., 2014).
View in article
McDonough, W.F., Sun, S.S. (1995) The composition of the Earth. Chemical Geology 120, 223–253. https://doi.org/10.1016/0009-2541(94)00140-4
Show in context(b) Primitive mantle normalised (McDonough and Sun, 1995) trace element patterns of the HDFs compared to microinclusion-bearing diamonds (shaded area – Klein-BenDavid et al., 2010, 2014).
View in article
Rudnick, R.L. (1990) Nd and Sr isotopic compositions of lower-crustal xenoliths from north Queensland, Australia: Implications for Nd model ages and crustal growth processes. Chemical Geology 83, 195–208. https://doi.org/10.1016/0009-2541(90)90280-K
Show in contextAlso plotted are the range of South African kimberlite and lamproites (Becker and Le Roex, 2006), bulk silicate Earth (BSE; Zindler and Hart, 1986), and the vector toward continental crust (CC arrow; Rudnick, 1990; Thompson et al., 2007).
View in article
They show a general inverse Sr-Nd isotope correlation from bulk silicate Earth (BSE; Zindler and Hart, 1986) and South African kimberlite (Becker and Le Roex, 2006) values to more radiogenic 87Sr/86Sr and unradiogenic 143Nd/144Nd ratios, which trend through South African olivine lamproites (formerly Group II kimberlites or orangeite; Becker and Le Roex, 2006) towards the range of continental crust compositions (Rudnick, 1990; Thompson et al., 2007).
View in article
Smith, E.M., Kopylova, M.G., Nowell, G.M., Pearson, D.G., Ryder, J. (2012) Archean mantle fluids preserved in fibrous diamonds from Wawa, Superior craton. Geology 40, 1071–1074. https://doi.org/10.1130/G33231.1
Show in contextThese HDFs provide the opportunity to directly examine the nature of carbon- and water-rich media in the deep Earth and constrain their varying origins (e.g., Smith et al., 2012; Klein-BenDavid et al., 2014; Kempe et al., 2021).
View in article
Available HDFs Sr isotope data range between 0.703 to 0.723, indicating sources ranging from ‘depleted’ oceanic mantle to old continental lithosphere (Akagi and Masuda, 1988; Klein-BenDavid et al., 2010, 2014; Smith et al., 2012; Weiss et al., 2015).
View in article
Stachel, T., Harris, J.W. (2008) The origin of cratonic diamonds — Constraints from mineral inclusions. Ore Geology Reviews 34, 5–32. https://doi.org/10.1016/j.oregeorev.2007.05.002
Show in contextConsidering the concentration and unaggregated nature of nitrogen in the studied diamonds, and a likely average mantle residence temperature of ≥950 °C (Stachel and Harris, 2008; Weiss et al., 2022a), their formation could take place from immediately prior to kimberlite eruption up to a maximum of 1 Ga before eruption (Taylor et al., 1996).
View in article
Stracke, A. (2012) Earth’s heterogeneous mantle: A product of convection-driven interaction between crust and mantle. Chemical Geology 330, 274–299. https://doi.org/10.1016/j.chemgeo.2012.08.007
Show in contextThese Pb isotope variations are between depleted to enriched mantle components for 208Pb/204Pb vs. 206Pb/204Pb, but extend to more radiogenic 207Pb/204Pb values above the Pb mantle array (Fig. S-1; Hart et al., 1992; Stracke, 2012).
View in article
Taylor, W.R., Canil, D., Milledge, H.J. (1996) Kinetics of Ib to IaA nitrogen aggregation in diamond. Geochimica et Cosmochimica Acta 60, 4725–4733. https://doi.org/10.1016/S0016-7037(96)00302-X
Show in contextConsidering the concentration and unaggregated nature of nitrogen in the studied diamonds, and a likely average mantle residence temperature of ≥950 °C (Stachel and Harris, 2008; Weiss et al., 2022a), their formation could take place from immediately prior to kimberlite eruption up to a maximum of 1 Ga before eruption (Taylor et al., 1996).
View in article
Thompson, R.N., Riches, A.J.V., Antoshechkina, P.M., Pearson, D.G., Nowell, G.M., Ottley, C.J., Dickin, A.P., Hards, V.L., Nguno, A.-K., Niku-Paavola, V. (2007) Origin of CFB Magmatism: Multi-tiered Intracrustal Picrite–Rhyolite Magmatic Plumbing at Spitzkoppe, Western Namibia, during Early Cretaceous Etendeka Magmatism. Journal of Petrology 48, 1119–1154. https://doi.org/10.1093/petrology/egm012
Show in context Also plotted are the range of South African kimberlite and lamproites (Becker and Le Roex, 2006), bulk silicate Earth (BSE; Zindler and Hart, 1986), and the vector toward continental crust (CC arrow; Rudnick, 1990; Thompson et al., 2007).
View in article
They show a general inverse Sr-Nd isotope correlation from bulk silicate Earth (BSE; Zindler and Hart, 1986) and South African kimberlite (Becker and Le Roex, 2006) values to more radiogenic 87Sr/86Sr and unradiogenic 143Nd/144Nd ratios, which trend through South African olivine lamproites (formerly Group II kimberlites or orangeite; Becker and Le Roex, 2006) towards the range of continental crust compositions (Rudnick, 1990; Thompson et al., 2007).
View in article
Timmerman, S., Yeow, H., Honda, M., Howell, D., Jaques, A.L., Krebs, M.Y., Woodland, S., Pearson, D.G., Ávila, J.N., Ireland, T.R. (2019) U-Th/He systematics of fluid-rich ‘fibrous’ diamonds – Evidence for pre- and syn-kimberlite eruption ages. Chemical Geology 515, 22–36. https://doi.org/10.1016/j.chemgeo.2019.04.001
Show in contextPreviously published Sr-Nd (±Pb) isotope data are limited to 5 additional microinclusion-bearing diamonds from Canada, Botswana and Congo, all with silicic to low-Mg carbonatitic HDF compositions (Klein-BenDavid et al., 2010, 2014; Timmerman et al., 2019).
View in article
Turner, S., Turner, M., Bourdon, B., Cooper, K., Porcelli, D. (2021) Extremely young melt infiltration of the sub-continental lithospheric mantle. Physics of the Earth and Planetary Interiors 313, 106325. https://doi.org/10.1016/j.pepi.2019.106325
Show in contextCarbon- and water-rich fluids involved in large-scale tectonic processes carry incompatible element-enriched chemical fingerprints, which are common in metasomatised mantle-derived samples (e.g., Dawson, 1984; Turner et al., 2021).
View in article
Weiss, Y., Griffin, W.L., Navon, O. (2013) Diamond-forming fluids in fibrous diamonds: The trace-element perspective. Earth and Planetary Science Letters 376, 110–125. https://doi.org/10.1016/j.epsl.2013.06.021
Show in contextThey exhibit overall decreasing levels from the most incompatible to compatible elements with characteristic anomalies (negative in most cases) of Rb, Nb, Sr, Zr, Hf and Ti, and trace element ratios indicating the involvement of accessory mantle phases in their formations (Weiss et al., 2013).
View in article
Weiss, Y., McNeill, J., Pearson, D.G., Nowell, G.M., Ottley, C.J. (2015) Highly saline fluids from a subducting slab as the source for fluid-rich diamonds. Nature 524, 339–342. https://doi.org/10.1038/nature14857
Show in contextAvailable HDFs Sr isotope data range between 0.703 to 0.723, indicating sources ranging from ‘depleted’ oceanic mantle to old continental lithosphere (Akagi and Masuda, 1988; Klein-BenDavid et al., 2010, 2014; Smith et al., 2012; Weiss et al., 2015).
View in article
Weiss, Y., Goldstein, S.L. (2018) The involvement of diamond-forming fluids in the metasomatic ‘cocktail’ of kimberlite sources. Mineralogy and Petrology, 1–19. https://doi.org/10.1007/s00710-018-0613-8
Show in contextData compared to the global variation between silicic, carbonatitic and saline HDF types (shaded area – Weiss and Goldstein, 2018).
View in article
Weiss, Y., Czas, J., Navon, O. (2022a) Fluid inclusions in fibrous diamonds. Reviews in Mineralogy and Geochemistry 88, 475–532. https://doi.org/10.2138/rmg.2022.88.09
Show in contextThe most common HDFs are found as microinclusions in ‘fibrous diamonds’ (a fast-growing form of diamond that is usually translucent or opaque with cuboid faces; see Graphical Abstract), which vary in composition between four major types: hydrous-silicic, rich in Si, Al, K and H2O; low-Mg carbonatitic and high-Mg carbonatitic, both rich in Ca, Mg, Fe, K and CO2; and hydrous-saline, rich in Cl, K, Na and H2O (Weiss et al., 2022a).
View in article
Major element compositions were determined by EPMA (Electron probe micro-analysis, Kempe et al., 2021; Weiss et al., 2022a).
View in article
These major element-radiogenic isotope systematics are similar to the decoupling between major and trace elements of HDFs from different lithospheric provinces worldwide (Weiss et al., 2022a).
View in article
Considering the concentration and unaggregated nature of nitrogen in the studied diamonds, and a likely average mantle residence temperature of ≥950 °C (Stachel and Harris, 2008; Weiss et al., 2022a), their formation could take place from immediately prior to kimberlite eruption up to a maximum of 1 Ga before eruption (Taylor et al., 1996).
View in article
A strong connection has previously been established between hydrous/carbonated eclogite lithologies (and pyroxenites) with silicic to low-Mg carbonatitic HDF types, comparable in composition to HDFs in the present study (Weiss et al., 2022a).
View in article
Weiss, Y., Jockusch, S., Koornneef, J.M., Elazar, O., Davies, G.R. (2022b) Laser ablation of ‘diamonds-in-water’ for trace element and isotopic composition analysis. Journal of Analytical Atomic Spectrometry 37, 1431–1441. https://doi.org/10.1039/D2JA00088A
Show in contextWe used the ‘diamond-in-water’ ablation approach to prepare the samples for solution trace element analyses by ICP-MS (Inductively coupled plasma mass spectrometry) and isotope analyses by TIMS (Thermal ionisation mass spectrometry, Weiss et al., 2022b).
View in article
The trace element compositions of the HDFs (Table S-2) were published previously by Weiss et al. (2022b).
View in article
Xu, W.-L., Gao, S., Yang, D.-B., Pei, F.-P., Wang, Q.-H. (2009) Geochemistry of eclogite xenoliths in Mesozoic adakitic rocks from Xuzhou-Suzhou area in central China and their tectonic implications. Lithos 107, 269–280. https://doi.org/10.1016/j.lithos.2008.11.004
Show in contextThe Sr-Nd-Pb isotope compositions of eclogite and pyroxenite xenoliths (occasionally diamondiferous) are extremely diverse, from highly unradiogenic to highly radiogenic values (e.g., Jacob, 2004; Xu et al., 2009; Aulbach et al., 2019).
View in article
Zindler, A., Hart, S. (1986) Chemical Geodynamics. Annual Review of Earth and Planetary Sciences 14, 493–571. https://doi.org/10.1146/annurev.ea.14.050186.002425
Show in contextAlso plotted are the range of South African kimberlite and lamproites (Becker and Le Roex, 2006), bulk silicate Earth (BSE; Zindler and Hart, 1986), and the vector toward continental crust (CC arrow; Rudnick, 1990; Thompson et al., 2007).
View in article
They show a general inverse Sr-Nd isotope correlation from bulk silicate Earth (BSE; Zindler and Hart, 1986) and South African kimberlite (Becker and Le Roex, 2006) values to more radiogenic 87Sr/86Sr and unradiogenic 143Nd/144Nd ratios, which trend through South African olivine lamproites (formerly Group II kimberlites or orangeite; Becker and Le Roex, 2006) towards the range of continental crust compositions (Rudnick, 1990; Thompson et al., 2007).
View in article
The isotopic range of cratonic continental lithosphere determined on whole rock xenolith data (dotted white area - measured values, and lined shaded area – age corrected initial values, based on the PetDB database;
View in article
top
Supplementary Information
The Supplementary Information includes:
- Sample Description
- Fourier-transform infrared (FTIR) spectroscopy
- Microinclusion major elements analyses
- Diamond ablation and processing
- Trace elements and radiogenic isotopes analyses
- Tables S-1 to S-3
- Figures S-1 to S-2
- Supplementary Information References
Download the Supplementary Information (PDF)
Figures
Figure 1 Major and trace element composition of HDF microinclusions in fibrous diamonds. (a) SiO2 + Al2O3–Na2O + K2O–MgO + FeO + CaO ternary diagram (in wt. %, on carbon- and water-free basis), showing the compositional range of HDFs in the studied diamonds (see key for sample symbols). Each datapoint represents an individual microinclusion. Data compared to the global variation between silicic, carbonatitic and saline HDF types (shaded area – Weiss and Goldstein, 2018
Weiss, Y., Goldstein, S.L. (2018) The involvement of diamond-forming fluids in the metasomatic ‘cocktail’ of kimberlite sources. Mineralogy and Petrology, 1–19. https://doi.org/10.1007/s00710-018-0613-8
). (b) Primitive mantle normalised (McDonough and Sun, 1995McDonough, W.F., Sun, S.S. (1995) The composition of the Earth. Chemical Geology 120, 223–253. https://doi.org/10.1016/0009-2541(94)00140-4
) trace element patterns of the HDFs compared to microinclusion-bearing diamonds (shaded area – Klein-BenDavid et al., 2010Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
). White-filled symbols are data falling between LOQ and LOD (between 10× σ and 3 × σ of the TPBs), and are regarded as qualitative (see details in the Supplementary Information).
Figure 2 Isotopic and trace element relationships of the HDFs. (a) 143Nd/144Nd vs. 87Sr/86Sr. Also plotted are the range of South African kimberlite and lamproites (Becker and Le Roex, 2006
Becker, M., Le Roex, A.P. (2006) Geochemistry of South African on- and off-craton, Group I and Group II kimberlites: Petrogenesis and source region evolution. Journal of Petrology 47, 673–703. https://doi.org/10.1093/petrology/egi089
), bulk silicate Earth (BSE; Zindler and Hart, 1986Zindler, A., Hart, S. (1986) Chemical Geodynamics. Annual Review of Earth and Planetary Sciences 14, 493–571. https://doi.org/10.1146/annurev.ea.14.050186.002425
), and the vector toward continental crust (CC arrow; Rudnick, 1990Rudnick, R.L. (1990) Nd and Sr isotopic compositions of lower-crustal xenoliths from north Queensland, Australia: Implications for Nd model ages and crustal growth processes. Chemical Geology 83, 195–208. https://doi.org/10.1016/0009-2541(90)90280-K
; Thompson et al., 2007Thompson, R.N., Riches, A.J.V., Antoshechkina, P.M., Pearson, D.G., Nowell, G.M., Ottley, C.J., Dickin, A.P., Hards, V.L., Nguno, A.-K., Niku-Paavola, V. (2007) Origin of CFB Magmatism: Multi-tiered Intracrustal Picrite–Rhyolite Magmatic Plumbing at Spitzkoppe, Western Namibia, during Early Cretaceous Etendeka Magmatism. Journal of Petrology 48, 1119–1154. https://doi.org/10.1093/petrology/egm012
). (b) 143Nd/144Nd vs. 147Sm/144Nd; the latter is calculated from isotope dilution data (Table S-3). (c) 143Nd/144Nd vs. primitive mantle normalised La/NbPM ratios; the inset includes diamond 516, which deviates from the general trend. Error bars represent ±2 SE and in most cases are smaller than the symbols.
Figure 3 Relationship between Pb and Sr isotope compositions of the HDFs. 206Pb/204Pb ratios are shown in the main panel and 207Pb/204Pb ratios in the inset. Error bars represent ±2 SE, which in most cases are smaller than the symbols.
Figure 4 Sr-Nd-Pb isotope compositions of HDF in fibrous diamonds. (a) 143Nd/144Nd vs. 87Sr/86Sr. Measured values (large coloured symbols) and initial ratios corrected for a maximum possible emplacement age of 550 Ma (small coloured symbols) are presented. Available published data for 5 diamonds from Botswana (UNK; all duplicate analyses are presented), Snap Lake (SL) and Congo (CNG) are also shown (small open symbols; Klein-BenDavid et al., 2010
Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P. (2010) Mixed fluid sources involved in diamond growth constrained by Sr–Nd–Pb–C–N isotopes and trace elements. Earth and Planetary Science Letters 289, 123–133. https://doi.org/10.1016/j.epsl.2009.10.035
, 2014Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V. (2014) The sources and time-integrated evolution of diamond-forming fluids – Trace elements and isotopic evidence. Geochimica et Cosmochimica Acta 125, 146–169. https://doi.org/10.1016/j.gca.2013.09.022
). The isotopic range of cratonic continental lithosphere determined on whole rock xenolith data (dotted white area - measured values, and lined shaded area – age corrected initial values, based on the PetDB database;Zindler, A., Hart, S. (1986) Chemical Geodynamics. Annual Review of Earth and Planetary Sciences 14, 493–571. https://doi.org/10.1146/annurev.ea.14.050186.002425
) are presented for comparison. (b) 208Pb/204Pb vs. 206Pb/204Pb, and (c) 207Pb/204Pb vs. 206Pb/204Pb; symbols and areas as in (a). The locus of compositions that developed undisturbed from primitive-mantle lead since Earth’s formation is shown for reference (geochron; long dashed black line); the regression line through all the HDF data yields an age of 3214 ± 369 Ma (dashed orange line and 95 % confidence interval).