Predicting isotopologue abundances in the products of organic catagenesis with a kinetic Monte-Carlo model

Xie, Hao; Formolo, Michael J; Eiler, John M.

doi:10.1016/j.gca.2022.03.028

Cited by 17 publications

(5 citation statements)

References 128 publications

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“…5B). This process was supported by a prior model of catagenetic processes that simplified the reactions driving catagenesis into a few key ones: homolytic cleavage, β-scission, H-abstraction, radical recombination, and radical isomerization (Xie et al, 2022). Xie et al (2022) argued that the carbon isotopic fractionations associated with catagenesis could be simplified and that the main fractionating reactions driving C isotopic change were homolytic cleavage and β-scission, which both impart isotope effects of k 13 /k 12 = 0.975±0.001 at 180 °C on the reacting carbon of a first order bond (Xie et al, 2022).…”

Section: Catagenesis and Metagenesismentioning

confidence: 95%

“…This process was supported by a prior model of catagenetic processes that simplified the reactions driving catagenesis into a few key ones: homolytic cleavage, β-scission, H-abstraction, radical recombination, and radical isomerization (Xie et al, 2022). Xie et al (2022) argued that the carbon isotopic fractionations associated with catagenesis could be simplified and that the main fractionating reactions driving C isotopic change were homolytic cleavage and β-scission, which both impart isotope effects of k 13 /k 12 = 0.975±0.001 at 180 °C on the reacting carbon of a first order bond (Xie et al, 2022). As a result, the bond breaking events that produce oil and gas occur more favorably for 12 C than for 13 C and leave the residue enriched in 13 C. The k 13 /k 12 value can vary by 0.975±0.010 depending on the nature of the bond being broken at 180 °C, which can result in site-specific variations in the primary isotope effect that vary by up to 10‰ (Tang et al, 2000;Xie et al, 2022).…”

Section: Catagenesis and Metagenesismentioning

confidence: 95%

“…Xie et al (2022) argued that the carbon isotopic fractionations associated with catagenesis could be simplified and that the main fractionating reactions driving C isotopic change were homolytic cleavage and β-scission, which both impart isotope effects of k 13 /k 12 = 0.975±0.001 at 180 °C on the reacting carbon of a first order bond (Xie et al, 2022). As a result, the bond breaking events that produce oil and gas occur more favorably for 12 C than for 13 C and leave the residue enriched in 13 C. The k 13 /k 12 value can vary by 0.975±0.010 depending on the nature of the bond being broken at 180 °C, which can result in site-specific variations in the primary isotope effect that vary by up to 10‰ (Tang et al, 2000;Xie et al, 2022). Secondary and tertiary isotope effects are an order of magnitude smaller (Tang et al, 2000;Xie et al, 2022).…”

Section: Catagenesis and Metagenesismentioning

confidence: 99%

“…As a result, the bond breaking events that produce oil and gas occur more favorably for 12 C than for 13 C and leave the residue enriched in 13 C. The k 13 /k 12 value can vary by 0.975±0.010 depending on the nature of the bond being broken at 180 °C, which can result in site-specific variations in the primary isotope effect that vary by up to 10‰ (Tang et al, 2000;Xie et al, 2022). Secondary and tertiary isotope effects are an order of magnitude smaller (Tang et al, 2000;Xie et al, 2022).…”

Section: Catagenesis and Metagenesismentioning

confidence: 99%

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The Carbon Isotopic Composition of Archean Kerogen and Its Resilience Through the Rock Cycle

Zeichner,

Fischer,

Lotem

et al. 2024

American Journal of Science

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The Archean rock record is limited and there is minimal organic matter available to understand the origin and evolution of life on early Earth. Low carbon isotope ratios have been measured in organic and reduced carbon phases in Archean rocks and have been invoked as biosignatures. However, it can be challenging to distinguish whether these low values reflect biotic formation, abiotic reactions, or post-depositional processes. To re-address this long-standing question, we compiled a comprehensive dataset of carbon isotope ratio measurements from organic carbon phases from Archean units that were analyzed using a variety of geochemical techniques. Our compilation also includes available descriptions and measurements of the stratigraphy, mineralogy, elemental ratios, and metamorphic grade for each data point. Our statistical analyses re-enforce a result that has been noted by prior compilations, that the carbon isotopic composition of Archean organic matter (OM) is broadly more 13C-deplete than the composition of Phanerozoic OM: The median δ13C values ( ±SD) of Archean total organic carbon and kerogen were −30.5±8‰ (n=2421) and −33.7±11.3‰ (n=556; Phanerozoic OM δ13C ±SD = −26.7±4.6‰ with n=449 from a prior compilation). Our study also identifies a previously unrecognized bimodality within the δ13C values of Archean OM that is observed even with subsampling of the data to account for geographic and stratigraphic sampling bias. We describe and model the isotopic and structural changes associated with the transformation of marine Type II kerogen from formation through diagenesis, catagenesis and metagenesis, and metamorphism, as described by trends on a van Krevelin diagram. Empirically, early maturation of organic matter during diagenesis results in shifts up to a few per-mille, which can occur in either direction depending on selective preservation and degradation of compounds. Thermal cracking that occurs during catagenesis can drive increases in δ13C of 5–12‰. At temperatures above greenschist metamorphism, carbon atoms exchange with other reactive carbon pools, driving increases in δ13C of up to 20‰. Together, our analyses suggest that the most metamorphosed graphitic samples from the earliest Archean are likely signatures of alteration, while low and multimodal ranges of δ13C values may preserve records of Archean ecology.

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Section: Catagenesis and Metagenesismentioning

confidence: 95%

Section: Catagenesis and Metagenesismentioning

confidence: 95%

Section: Catagenesis and Metagenesismentioning

confidence: 99%

Section: Catagenesis and Metagenesismentioning

confidence: 99%

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The Carbon Isotopic Composition of Archean Kerogen and Its Resilience Through the Rock Cycle

Zeichner,

Fischer,

Lotem

et al. 2024

American Journal of Science

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“…16,18 Moreover, even δ 13 C PSIA signals of thermogenic propane is dependent on source materials characteristics, how and on what extend these parameters of precursors will influence propane's carbon PSIA patterns still remains unclear. Thus, resolving the isotopomers' signature of thermogenic propane definitely require more sophisticated models [19][20][21][22] in order to understand position specific isotope fractionation of thermogenic propane.…”

Section: Introductionmentioning

confidence: 99%

Modeling position specific carbon isotopologue fractionation of thermogenic propane and precursors

Jin,

Peng

2024

TIG

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<p>Position specific isotope analysis (PSIA) of thermogenic propane allows to track carbon isotopic compositions at different molecular positions, and thus providing new evidence to investigate propane��s origin, fate, and mechanisms of formation. However, the link between observed ��<sup>13</sup>C PSIA signals of propane and carbon isotopologue signatures of precursors in source organics still remains unclear, and understanding the underlying mechanisms requires a more sophisticated model. Here we developed a mathematical framework to simulate position specific carbon isotopologues of propane and its precursors based on mechanistic understanding of thermogenic propane��s bond-cleavage pathways. Besides, our model also allows integrating multiple signals including temperature, and isotopic characteristics of source compounds. Our model is validated by precisely reproducing propane��s experimental PSIA data obtained during cracking of different kerogens, and also correctly quantified the initial carbon isotopic signatures and the initial fraction of the different precursors in the source materials. Our model allows to include more complex reaction mechanisms to elucidate unknown reaction pathways, and could also guide and optimize future experimental studies to test different hypothesis.</p>

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Equilibrium and kinetic isotope effects in heterogeneous catalysis: A density functional theory perspective

Chen

2023

Catalysis Communications

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Predicting isotopologue abundances in the products of organic catagenesis with a kinetic Monte-Carlo model

Cited by 17 publications

References 128 publications

The Carbon Isotopic Composition of Archean Kerogen and Its Resilience Through the Rock Cycle

The Carbon Isotopic Composition of Archean Kerogen and Its Resilience Through the Rock Cycle

Modeling position specific carbon isotopologue fractionation of thermogenic propane and precursors

Equilibrium and kinetic isotope effects in heterogeneous catalysis: A density functional theory perspective

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