Clumped isotopes are heavy isotopes that are bonded to other heavy isotopes. The relative abundance of clumped isotopes (and multiply-substituted isotopologues) in molecules such as methane, nitrous oxide, and carbonate is an area of active investigation. The carbonate clumped-isotope thermometer, or "13C–18O order/disorder carbonate thermometer", is a new approach for paleoclimate reconstruction, based on the temperature dependence of the clumping of 13C and 18O into bonds within the carbonate mineral lattice. This approach has the advantage that the 18O ratio in water is not necessary (different from the δ18O approach), but for precise paleotemperature estimation, it also needs very large and uncontaminated samples, long analytical runs, and extensive replication. Commonly used sample sources for paleoclimatological work include corals, otoliths, gastropods, tufa, bivalves, and foraminifera. Results are usually expressed as Δ47 (said as "cap 47"), which is the deviation of the ratio of isotopologues of CO2 with a molecular weight of 47 to those with a weight of 44 from the ratio expected if they were randomly distributed.
Molecules made up of elements with multiple isotopes can vary in their isotopic composition, these different mass molecules are called isotopologues. Isotopologues such as 12C18O17O, contain multiple heavy isotopes of oxygen substituting for the more common 16O, and are termed multiply-substituted isotoploluges. The multiply-substituted isotopologue 13C18O16O contains a bond between two of these heavier isotopes (13C and 18O), which is a "clumped" isotope bond.
The abundance of masses for a given molecule (e.g. CO2) can be predicted using the relative abundance of isotopes of its constituent atoms (13C/12C, 18O/16O and 17O/16O). The relative abundance of each isotopologue (e.g. mass-47 CO2) is proportional to the relative abundance of each isotopic species.
- 47R/44R = (2×[13C][18O][16O]+2×[12C][18O][17O]+[13C][17O][16O])/([12C][16O][16O])
This predicted abundance assumes a non-biased stochastic distribution of isotopes, natural materials tend to deviate from these stochastic values, the study of which forms the basis of clumped isotope geochemistry.
When a heavier isotope substitutes for a lighter isotope (e.g., 18O for 16O), the chemical bond's vibration will be slower, lowering its zero-point energy. In other words, thermodynamic stability is related to the isotopic composition of the molecule.
12C16O32− (≈98.2%), 13C16O32− (≈1.1%), 12C18O16O22− (≈0.6%) and 12C17O16O22− (≈0.11%) are the most abundant isotopologues (≈99%) for the carbonate ions, controlling the bulk δ13C, δ17O and δ18O values in natural carbonate minerals. Each of these isopotologes has different thermodynamic stability. For a carbonate crystal at thermodynamic equilibrium, the relative abundances of the carbonate ion isotopologues is controlled by reactions such as:
13C16O32− + 12C18O16O22− ⇌ 12C16O32− + 13C18O16O22−
The equilibrium constants for this reactions are temperature-dependent, with a trend that heavy isotopes tend to "clump" with each other (increasing the proportions of multiply substituted isotopologues) as temperature decreases. Reaction 1 will be driven to the right with decreasing temperature, to the left with increasing temperature. Therefore, the equilibrium constant for this reaction can be used as an paleotemperature indicator, as long as the temperature dependence of this reaction and the relative abundances of the carbonate ion isotopologues are known.
Differences from the conventional δ18O analysis
In conventional δ18O analysis, both the δ18O values in carbonates and water are needed to estimate paleoclimate. However, for many times and places, the δ18O in water can only be inferred, and also the 16O/18O ratio between carbonate and water may vary with the change in temperature. Therefore, the accuracy of the thermometer may be compromised.
Whereas for the carbonate clumped-isotope thermometer, the equilibrium is independent of the isotope compositions of waters from which carbonates grew. Therefore, the only information needed is the abundance of bonds between rare, heavy isotopes within the carbonate mineral.
- Extract CO
2 from carbonates by reaction with anhydrous phosphoric acid. (there are no direct way to measure the abundances of CO32−s in Reaction 1 with high enough precision). The phosphoric acid temperature is often held between 25° to 90 °C and can be as high as 110 °C.
- Purify the CO
2 that has been extracted. This step removes contaminant gases like hydrocarbons and halocarbons which can be removed by gas chromatography.
- Mass spectrometric analyses of purified CO
2, to obtain δ13C, δ18O, and Δ47 (Abundances of mass-47 CO
2) value. (precision need to be as high as ≈10−5, for that isotope signals of interest are often less than ≈10−3)
Clumped isotopes analyses have traditionally been used in lieu of conventional δ18O analyses when the δ18O of seawater or source water is poorly constrained. While conventional δ18O analysis solves for temperature as a function of both carbonate and water δ18O, clumped isotope analyses can provide temperature estimates that are independent of the source water δ18O. Δ47-derived temperature can then be used in conjunction with carbonate δ18O to reconstruct δ18O of the source water, thus providing information on the water with which the carbonate was equilibrated.
Clumped isotope analyses thus allow for estimates of two key environmental variables: temperature and water δ18O. These variables are especially useful for reconstructing past climates, as they can provide information on a wide range of environmental properties. For example, temperature variability can imply changes in solar irradiance, greenhouse gas concentration, or albedo, while changes in water δ18O can be used to estimate changes in ice volume, sea level, or rainfall intensity and location.
Studies have used temperatures derived from clumped isotopes for varied and numerous paleoclimate applications — to constrain δ18O of past seawater, pinpoint the timing of icehouse-hothouse transitions, track changes in ice volume through an ice age, and to reconstruct temperature changes in ancient lake basins.
Clumped isotope analyses have recently been used to constrain the paleoaltitude or uplift history of a region. Air temperature decreases systematically with altitude throughout the troposphere (see lapse rate). Due to the close coupling between lake water temperature and air temperature, there is a similar decrease in lake water temperature as altitude increases. Thus, variation in water temperature implied by Δ47 could indicate changes in lake altitude, driven by tectonic uplift or subsidence. Two recent studies derive the timing of the uplift of the Andes Mountains and the Altiplano Plateau, citing sharp decreases in Δ47-derived temperatures as evidence of rapid tectonic uplift.
Measurements of Δ47 can be used to constrain natural and synthetic sources of atmospheric CO2, (e.g. respiration and combustion), as each of these processes are associated with different average Δ47 temperatures of formation.
Measurements of Δ47 can be used to better understand the physiology of extinct organisms, and to place constraints on the early development of endothermy, the process by which organisms regulate their internal body temperatures. Prior to the development of clumped isotope analysis, there was no straightforward way to estimate either the body temperature or body water δ18O of extinct animals. Eagle et al., 2010 measure Δ47 in bioapatite from a modern Indian elephant, white rhinoceros, Nile crocodile and American alligator. These animals were chosen as they span a wide range in internal body temperatures, allowing for the creation of a mathematical framework relating Δ47 of bioapatite and internal body temperature. This relationship has been applied to analyses of fossil teeth, in order to predict the body temperatures of a woolly mammoth and a sauropod dinosaur. The latest Δ47 temperature calibration for (bio)apatite of Löffler et al. 2019 covers a wide temperature range of 1 to 80 °C and was applied to a fossil Megalodon shark tooth for calculating seawater temperatures and δ18O values.
Petrology and metamorphic alteration
A key premise of most clumped isotope analyses is that samples have retained their primary isotopic signatures. However, isotopic resetting or alteration, resulting from elevated temperature, can provide a different type of information about past climates. For example, when carbonate is isotopically reset by high temperatures, measurements of Δ47 can provide information about the duration and extent of metamorphic alteration. In one such study, Δ47 from late Neoproterozoic Doushantou cap carbonate is used to assess the temperature evolution of the lower crust in southern China.
Primitive meteorites have been studied using measurements of Δ47. These analyses also assume that the primary isotopic signature of the sample has been lost. In this case, measurements of Δ47 instead provide information on the high-temperature event that isotopically reset the sample. Existing Δ47 analyses on primitive meteorites have been used to infer the duration and temperature of aqueous alteration events, as well as to estimate the isotopic composition of the alteration fluid.
An emerging body of work highlights the application potential for clumped isotopes to reconstruct temperature and fluid properties in hydrothermal ore deposits. In mineral exploration, delineation of the heat footprint around an ore body provides critical insight into the processes that drive transport and deposition of metals. During proof of concept studies, clumped isotopes were used to provide accurate temperature reconstructions in epithermal, sediment hosted, and Mississippi Valley Type (MVT) deposits. These case studies are supported by measurement of carbonates in active geothermal settings.
The temperature dependent relationship is subtle (−0.0005%/°C) (Quade 2007).
13C18O16O22− is a rare isotopologue (≈60 ppm ).
Therefore, to obtain adequate precision, this approach requires long analyses (≈2–3 hours) and very large and uncontaminated samples.
Clumped isotope analyses assume that measured Δ47 is composed of 13C18O16O22−, the most common isotopologue of mass 47. Corrections to account for less common isotopologues of mass 47 (e.g. 12C18O17O 16O2−) are not completely standardized between labs.
- Isotopic signature
- Isotope analysis
- Isotope geochemistry
- Isotopic labeling
- Eiler JM (2007) ‘Clumped-isotope’ geochemistry – The study of naturally-occurring, multiply-substituted isotopologues. Earth and Planetary Science Letters 262: 309–327.
- Lea D.W. (2014) Elemental and Isotopic Proxies of Past Ocean Temperatures. In: Holland H.D. and Turekian K.K. (eds.) Treatise on Geochemistry, Second Edition, vol. 8, pp. 373-397. Oxford: Elsevier.
- Ghosh P, Adkins J, Affek H, et al. (2006) 13C-18O bonds in carbonate minerals: A new kind of paleothermometer. Geochimica et Cosmochimica Acta 70: 1439–1456.
- Ghosh P, Eiler J, Campana SE, and Feeney RF (2007) Calibration of the carbonate ‘clumped isotope’ paleothermometer for otoliths. Geochimica et Cosmochimica Acta 71: 2736–2744.
- Tripati AK, Eagle RA, Thiagarajan N, et al. (2010) 13C-18O isotope signatures and ‘clumped isotope’ thermometry in foraminifera and coccoliths. Geochimica et Cosmochimica Acta 74: 5697–5717
- Affek, Hagit (2012). "Clumped isotope paleothermometry: Principles, applications, and challenges". Reconstructing Earth's Deep-Time Climate—The State of the Art in 2012, Paleontological Society Short Course, November 3, 2012. 8: 101–114.
- Urey, H.C., 1947. The thermodynamic properties of isotopic substances. J. Chem. Soc. London 1947, 561–581.
- Bigeleisen, J., Mayer, M.G., 1947. Calculation of equilibrium constants for isotopic exchange reactions. J. Chem. Phys. 15, 261–267.
- Wang, Z., Schauble, E.A., Eiler, J.M., 2004. Equilibrium thermodynamics of multiply substituted isotopologues of molecular gases. Geochim. Cosmochim. Acta 68, 4779–4797.
- Chappell, J., Shackleton, N.J., 1986. Oxygen isotopes and sea level. Nature 324, 137–140.
- C. Waelbroeck, L. Labeyrie, E. Michel, et al., (2002) Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records. Quaternary Science Reviews. 21: 295-305
- McCrea, J.M., 1950. On the isotopic chemistry of carbonates and a paleotemperature scale. J. Chem. Phys. 18, 849–857.
- Swart, P.K., Burns, S.J., Leder, J.J., 1991. Fractionation of the stable isotopes of oxygen and carbon in carbon dioxide during the reaction of calcite with phosphoric acid as a function of temperature and technique. Chem. Geol. (Isot. Geosci. Sec.) 86, 89–96.
- Eiler, John M. (2011-12-01). "Paleoclimate reconstruction using carbonate clumped isotope thermometry". Quaternary Science Reviews. 30 (25–26): 3575–3588. Bibcode:2011QSRv...30.3575E. doi:10.1016/j.quascirev.2011.09.001. ISSN 0277-3791.
- Wacker, Ulrike; Rutz, Tanja; Löffler, Niklas; Conrad, Anika C.; Tütken, Thomas; Böttcher, Michael E.; Fiebig, Jens (December 2016). "Clumped isotope thermometry of carbonate-bearing apatite: Revised sample pre-treatment, acid digestion, and temperature calibration". Chemical Geology. 443: 97–110. Bibcode:2016ChGeo.443...97W. doi:10.1016/j.chemgeo.2016.09.009.
- Löffler, N.; Fiebig, J.; Mulch, A.; Tütken, T.; Schmidt, B.C.; Bajnai, D.; Conrad, A.C.; Wacker, U.; Böttcher, M.E. (May 2019). "Refining the temperature dependence of the oxygen and clumped isotopic compositions of structurally bound carbonate in apatite". Geochimica et Cosmochimica Acta. 253: 19–38. Bibcode:2019GeCoA.253...19L. doi:10.1016/j.gca.2019.03.002.
- Eiler, J.M., Schauble, E., 2004. in earth's atmosphere. Geochim. Cosmochim. Acta 68, 4767–4777.
- Huntington, K. W.; Budd, D. A.; Wernicke, B. P.; Eiler, J. M. (2011-09-01). "Use of Clumped-Isotope Thermometry To Constrain the Crystallization Temperature of Diagenetic Calcite". Journal of Sedimentary Research. 81 (9): 656–669. Bibcode:2011JSedR..81..656H. doi:10.2110/jsr.2011.51. ISSN 1527-1404.
- Came, Rosemarie E.; Eiler, John M.; Veizer, Ján; Azmy, Karem; Brand, Uwe; Weidman, Christopher R. (September 2007). "Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era" (PDF). Nature. 449 (7159): 198–201. Bibcode:2007Natur.449..198C. doi:10.1038/nature06085. ISSN 1476-4687. PMID 17851520.
- Finnegan, S.; Bergmann, K. D.; Eiler, J.; Jones, D. S.; Fike, D. A.; Eisenman, I. L.; Hughes, N.; Tripati, A. K.; Fischer, W. W. (2010-12-01). "Constraints on the duration and magnitude of Late Ordovician-Early Silurian glaciation and its relationship to the Late Ordovician mass extinction from carbonate clumped isotope paleothermometry". AGU Fall Meeting Abstracts. 54: B54B–04. Bibcode:2010AGUFM.B54B..04F.
- "New constraints on water temperature at Lake Bonneville from carbonate clumped isotopes - ProQuest". Retrieved 2018-02-04.
- Ghosh, Prosenjit; Garzione, Carmala N.; Eiler, John M. (2006-01-27). "Rapid Uplift of the Altiplano Revealed Through 13C-18O Bonds in Paleosol Carbonates". Science. 311 (5760): 511–515. Bibcode:2006Sci...311..511G. doi:10.1126/science.1119365. ISSN 0036-8075. PMID 16439658.
- Huntington, K. W.; Wernicke, B. P.; Eiler, J. M. (2010-06-01). "Influence of climate change and uplift on Colorado Plateau paleotemperatures from carbonate clumped isotope thermometry" (PDF). Tectonics. 29 (3): TC3005. Bibcode:2010Tecto..29.3005H. doi:10.1029/2009TC002449. ISSN 1944-9194.
- Quade, Jay; Breecker, Daniel O.; Daëron, Mathieu; Eiler, John (2011-02-01). "The paleoaltimetry of Tibet: An isotopic perspective". American Journal of Science. 311 (2): 77–115. Bibcode:2011AmJS..311...77Q. doi:10.2475/02.2011.01. ISSN 0002-9599.
- Hren, Michael T.; Sheldon, Nathan D. (2012-07-01). "Temporal variations in lake water temperature: Paleoenvironmental implications of lake carbonate δ18O and temperature records". Earth and Planetary Science Letters. 337-338: 77–84. Bibcode:2012E&PSL.337...77H. doi:10.1016/j.epsl.2012.05.019. ISSN 0012-821X.
- Garzione, Carmala N.; Hoke, Gregory D.; Libarkin, Julie C.; Withers, Saunia; MacFadden, Bruce; Eiler, John; Ghosh, Prosenjit; Mulch, Andreas (2008-06-06). "Rise of the Andes". Science. 320 (5881): 1304–1307. Bibcode:2008Sci...320.1304G. doi:10.1126/science.1148615. ISSN 0036-8075. PMID 18535236.
- Eiler, John M.; Schauble, Edwin (2004-12-01). "18O13C16O in Earth's atmosphere". Geochimica et Cosmochimica Acta. 68 (23): 4767–4777. Bibcode:2004GeCoA..68.4767E. doi:10.1016/j.gca.2004.05.035. ISSN 0016-7037.
- Laskar, Amzad H.; Mahata, Sasadhar; Liang, Mao-Chang (2016). "Identification of Anthropogenic CO2 Using Triple Oxygen and Clumped Isotopes". Environmental Science & Technology. 50 (21): 11806–11814. Bibcode:2016EnST...5011806L. doi:10.1021/acs.est.6b02989. PMID 27690222.
- Eagle, Robert A.; Schauble, Edwin A.; Tripati, Aradhna K.; Tütken, Thomas; Hulbert, Richard C.; Eiler, John M. (2010-06-08). "Body temperatures of modern and extinct vertebrates from 13C-18O bond abundances in bioapatite". Proceedings of the National Academy of Sciences. 107 (23): 10377–10382. Bibcode:2010PNAS..10710377E. doi:10.1073/pnas.0911115107. ISSN 0027-8424. PMC 2890843. PMID 20498092.
- Eagle, Robert A.; Tütken, Thomas; Martin, Taylor S.; Tripati, Aradhna K.; Fricke, Henry C.; Connely, Melissa; Cifelli, Richard L.; Eiler, John M. (2011-07-22). "Dinosaur Body Temperatures Determined from Isotopic (13C-18O) Ordering in Fossil Biominerals". Science. 333 (6041): 443–445. Bibcode:2011Sci...333..443E. doi:10.1126/science.1206196. ISSN 0036-8075. PMID 21700837.
- Passey, Benjamin H.; Henkes, Gregory A. (2012-10-15). "Carbonate clumped isotope bond reordering and geospeedometry". Earth and Planetary Science Letters. 351-352: 223–236. Bibcode:2012E&PSL.351..223P. doi:10.1016/j.epsl.2012.07.021. ISSN 0012-821X.
- Guo, Weifu; Eiler, John M. (2007-11-15). "Temperatures of aqueous alteration and evidence for methane generation on the parent bodies of the CM chondrites". Geochimica et Cosmochimica Acta. 71 (22): 5565–5575. Bibcode:2007GeCoA..71.5565G. CiteSeerX 10.1.1.425.1442. doi:10.1016/j.gca.2007.07.029. ISSN 0016-7037.
- Halevy, Itay; Fischer, Woodward W.; Eiler, John M. (2011-10-11). "Carbonates in the Martian meteorite Allan Hills 84001 formed at 18 ± 4 °C in a near-surface aqueous environment". Proceedings of the National Academy of Sciences. 108 (41): 16895–16899. Bibcode:2011PNAS..10816895H. doi:10.1073/pnas.1109444108. ISSN 0027-8424. PMC 3193235. PMID 21969543.
- Mering, John; Barker, Shaun; Huntington, Katherine; Simmons, Stuart; Dipple, Gregory; Andrew, Benjamin; Schauer, Andrew (2018-12-01). "Taking the Temperature of Hydrothermal Ore Deposits Using Clumped Isotope Thermometry". Economic Geology. 113 (8): 1671–1678. doi:10.5382/econgeo.2018.4608. ISSN 0361-0128.
- Kirk, Ruth; Marca, Alina; Myhill, Daniel J.; Dennis, Paul F. (2018-01-01). "Clumped isotope evidence for episodic, rapid flow of fluids in a mineralized fault system in the Peak District, UK". Journal of the Geological Society. 176 (3): jgs2016–117. doi:10.1144/jgs2016-117. ISSN 0016-7649.
- Kluge, Tobias; John, Cédric M.; Boch, Ronny; Kele, Sándor (2018). "Assessment of Factors Controlling Clumped Isotopes and δ18O Values of Hydrothermal Vent Calcites". Geochemistry, Geophysics, Geosystems. 19 (6): 1844–1858. doi:10.1029/2017GC006969. hdl:10044/1/63564. ISSN 1525-2027.
- Kele, Sándor; Breitenbach, Sebastian F.M.; Capezzuoli, Enrico; Meckler, A. Nele; Ziegler, Martin; Millan, Isabel M.; Kluge, Tobias; Deák, József; Hanselmann, Kurt; John, Cédric M.; Yan, Hao; Liu, Zaihua; Bernasconi, Stefano M. (2015). "Temperature dependence of oxygen- and clumped isotope fractionation in carbonates: A study of travertines and tufas in the 6–95°C temperature range" (PDF). Geochimica et Cosmochimica Acta. 168: 172–192. Bibcode:2015GeCoA.168..172K. doi:10.1016/j.gca.2015.06.032.