Experimental calibration of clumped isotope reordering in dolomite

Lloyd, Max K.; Ryb, Uri; Eiler, John M.

doi:10.1016/j.gca.2018.08.036

Cited by 79 publications

(94 citation statements)

References 61 publications

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“…Given the thermodynamic basis for the carbonate clumped isotope thermometer, it is expected that the Δ 47 value of a carbonate mineral that initially grows at low-temperature and then is subjected to a higher temperature will monotonically decrease in ∆ 47 until it approaches the new, higher temperature equilibrium state of a lower Δ 47 value ( Figure 1a). This behavior was previously observed in calcite, apatite, and dolomite reordering experiments (Passey & Henkes, 2012;Henkes et al, 2014;Stolper & Eiler, 2015;Lloyd et al, 2018;Brenner et al, 2018). The reaction progress of solid-state isotopic reordering we observe in aragonite violates this expectation.…”

Section: Clumped Isotope Reordering Of Low-temperature Aragonitesupporting

confidence: 86%

“…The application of carbonate clumped isotope thermometry to the reconstruction of climate, water δ 18 O values, or the thermal histories of rocks is complicated by the alteration of Δ 47 values at elevated burial temperatures through solid-state reordering of C-O bonds (Passey & Henkes, 2012;Henkes et al, 2014;Stolper & Eiler 2015;Lloyd et al, 2017;Shenton et al, 2015;Gallagher et al, 2017;Lacroix & Niemi, 2019;Ryb et al, 2017;Ingalls, 2019). Previous studies have used controlled heating experiments to constrain the kinetics of solid-state isotope reordering of calcite (Passey & Henkes, 2012;Henkes, et al, 2014;Stolper & Eiler, 2015;Brenner et al, 2018), apatite (Stolper & Eiler, 2015) and dolomite (Lloyd et al, 2018). In these experiments, aliquots of the mineral of interest were held at a constant temperature for different amounts of time to create a time series over which the mineral Δ 47 values could be observed to gradually approach equilibrium appropriate for that temperature.…”

Section: Introductionmentioning

confidence: 99%

“…This unresolved aspect of the reaction-diffusion model is one of the inspirations for the present study. While both the defect-annealing and reaction-diffusion models have been successfully applied to natural samples (Henkes et al, 2014;Shenton et al, 2015;Lloyd et al, 2017;Ryb et al, 2017, Ingalls, 2019, it has been argued that the reaction-diffusion model is favored by the observation that the kinetics of isotopic reordering in optical calcite, brachiopods, and deformed and undeformed natural marbles are indistinguishable from one another (the idea being that these diverse materials might be expected to differ in their initial defect populations; Stolper & Eiler, 2015;Ryb et al, 2017;Lloyd et al, 2018). Nevertheless, there is a strong motivation to establish which of these two interpretations (or perhaps some other not yet proposed) is correct.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of solid-state clumped isotope reordering in carbonate minerals from aragonite heating experiments

Chen

Ryb

Piasecki

et al. 2019

Geochimica et Cosmochimica Acta

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The clumped isotope compositions of carbonate minerals are subject to alteration at elevated temperatures. Understanding the mechanism of solid-state reordering in carbonate minerals is important in our interpretations of past climates and the thermal history of rocks. The kinetics of solid-state isotope reordering has been previously studied through controlled heating experiments of calcite, dolomite and apatite. Here we further explore this issue through controlled heating experiments on aragonite. We find that Δ 47 values generally decrease during heating of aragonite, but increase by 0.05-0.15‰ as aragonite starts to transform into calcite. We argue that this finding is consistent with the presence of an intermediate pool of immediately adjacent singly-substituted carbonate ion isotopologues ('pairs'), which back-react to form clumped isotopologues during aragonite to calcite transformation, revealing the existence of kinetically preferred isotope exchange pathways. Our results reinforce the 'reaction-diffusion' model as the mechanism for solid-state clumped isotope reordering in carbonate minerals. Our experiments also reveal that the reordering kinetics in aragonite is faster than in calcite and 2 dolomite, making its clumped isotope composition highly susceptible to alteration during early diagenesis, even before conversion to calcite.

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Section: Clumped Isotope Reordering Of Low-temperature Aragonitesupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanism of solid-state clumped isotope reordering in carbonate minerals from aragonite heating experiments

Chen

Ryb

Piasecki

et al. 2019

Geochimica et Cosmochimica Acta

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“…Such differences could reflect thermal equilibration of ∆ 47 temperatures through solid‐state reordering either by cryptic dissolution or recrystallization (Mangenot et al ., ). The temperature at which solid‐state reordering occurs in dolomite is still not fully understood, but most studies agree that it happens at much slower rates and higher temperatures in dolomite than calcite (Ryb et al ., ; Lloyd et al ., ; and references therein) probably >250 to 300°C (Ferry et al ., ; Ryb et al ., ). Since ∆ 47 values in calcite the Mount Whyte Formation suggest a temperature of 165°C at maximum burial, the ∆ 47 values for dolomite are most likely not thermally re‐equilibrated or altered by solid‐state reordering.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Evaluating new fault‐controlled hydrothermal dolomitization models: Insights from the Cambrian Dolomite, Western Canadian Sedimentary Basin

et al. 2020

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Fault‐controlled hydrothermal dolomitization in tectonically complex basins can occur at any depth and from different fluid compositions, including ‘deep‐seated’, ‘crustal’ or ‘basinal’ brines. Nevertheless, many studies have failed to identify the actual source of these fluids, resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitization. With development of new concepts in hydrothermal dolomitization, the study aims in particular to test the hypothesis that dolomitizing fluids were sourced from either seawater, ultramafic carbonation or a mixture between the two by utilizing the Cambrian Mount Whyte Formation as an example. Here, the large‐scale dolostone bodies are fabric‐destructive with a range of crystal fabrics, including euhedral replacement (RD1) and anhedral replacement (RD2). Since dolomite is cross‐cut by low amplitude stylolites, dolomitization is interpreted to have occurred shortly after deposition, at a very shallow depth (<1 km). At this time, there would have been sufficient porosity in the mudstones for extensive dolomitization to occur, and the necessary high heat flows and faulting associated with Cambrian rifting to transfer hot brines into the near surface. While the δ18Owater and 87Sr/86Sr ratios values of RD1 are comparable with Cambrian seawater, RD2 shows higher values in both parameters. Therefore, although aspects of the fluid geochemistry are consistent with dolomitization from seawater, very high fluid temperature and salinity could be suggestive of mixing with another, hydrothermal fluid. The very hot temperature, positive Eu anomaly, enriched metal concentrations, and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks, potentially as a result of interaction between the underlying Proterozoic serpentinites and CO2‐rich fluids. This study highlights that large‐scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses, providing a potential explanation for the mass balance problem often associated with their genesis.

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“…This protocol was adopted by various researchers 27,30,31 for the analysis of clumped isotopes in carbonates 32 . The prime advantage of the CAB method is that acid digestion occurs at 90°C 23,33,34 or even higher temperature (110°C) 35 . This decreases the reaction time and increases the sample throughput, and avoids any types of post‐digestion isotope exchange possibilities.…”

Section: Introductionmentioning

confidence: 99%

Ab initio quantum chemical studies of isotopic fractionation during acid digestion reaction of dolomite for clumped isotope application

Pramanik

Ghosh

Banerjee

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale In ‘clumped isotope paleothermometry’ carbonates are reacted with anhydrous phosphoric acid to extract CO2 that carries the isotopic signature of the reacting carbonates, and the amount of clumping in the product CO2 is measured. Previous theoretical models for determining clumped isotopic fractionation in product CO2 during acid digestion of carbonates are independent of the cations present in the carbonate lattice. Hence further study is required to understand the cationic effect. Methods We studied the acid reaction mechanism based on the protonation of carbonates, calculated the acid fractionation factor for dolomite using the partition functions and vibrational frequencies obtained for the transition state structure, and determined the effect of cations on the acid fractionation factor. Experimentally, carbonates are reacted using the modified sealed vessel method and analyzed in the dual inlet of a ThermoFinnigan MAT 253 isotope ratio mass spectrometer. Results The oretically obtained acid fractionation factor can be expressed as Δ47 acid fractionation in dolomite = −0.28563 + 0.49508 * (105/T2) − 0.08231 * (105/T2)2 for a temperature range between 278.15 and 383.15 K. The theoretical slope of the dolomite–acid digestion curve is lower than that of the calcite–acid digestion curve obtained using the identical reaction mechanism. Our theoretical slope is consistent with the result from the common acid bath experiments but higher than the slope obtained in our experimental study using the modified sealed vessel method and in a previous theoretical study using the H2CO3 model. Conclusions The transition state structure, obtained in our study, includes the cations present in the carbonate minerals and provides distinct acid fractionation factors for calcite and dolomite. The observed gentler slope of the theoretically calculated dolomite–acid digestion curve than of the calcite curve is expected considering the stronger Mg–O bond. Our experimental approach invokes post‐digestion isotopic exchange and agrees with the previous theoretical estimates where post‐digestion isotopic fractionation was considered.

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Experimental calibration of clumped isotope reordering in dolomite

Cited by 79 publications

References 61 publications

Mechanism of solid-state clumped isotope reordering in carbonate minerals from aragonite heating experiments

Mechanism of solid-state clumped isotope reordering in carbonate minerals from aragonite heating experiments

Evaluating new fault‐controlled hydrothermal dolomitization models: Insights from the Cambrian Dolomite, Western Canadian Sedimentary Basin

Ab initio quantum chemical studies of isotopic fractionation during acid digestion reaction of dolomite for clumped isotope application

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