Radiolytic alteration of biopolymers in the Mulga Rock (Australia) uranium deposit

Jaraula, Caroline M.B.; Schwark, Lorenz; Moreau, Xavier; Pickel, W.; Bagas, Leon; Grice, Kliti

doi:10.1016/j.apgeochem.2014.11.012

Cited by 29 publications

(33 citation statements)

References 76 publications

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“…Purportedly the radiolytic cleavage of water yields highly reactive OHradicals which quickly react with the in-situ organic matter during diagenesis (Court et al, 2006;Jaraula et al, 2015), leading to enhanced oxygen contents in the kerogen structure. Alternatively, peroxides can also be formed in response of irradiation (Gebicki and Gebicki, 1993) which can further oxidize the kerogen quickly (McDonald et al, 1998).…”

Section: Oxygen-containing Moietiesmentioning

confidence: 99%

“…The most common isotopes of natural uranium are 238 U (99.27%) and 235 U (0.72%) (Osmond and Cowart, 1976). Most of the radiation resulting from 238 U decay in natural systems is emitted in the form of α-radiation followed by less intensive γ-radiation (Jaraula et al, 2015). With a half-life of 4.5 billion years, 238 U decays exponentially ( Fig.…”

Section: Radiation Dosagementioning

confidence: 99%

“…may have been formed by incipient thermal cleavage reactions or by irradiation-induced maturation Jaraula et al (2015). reported that the odd/even carbon preference of n-alkanes in an immature deposit (R o =0.26%) decreases with increasing uranium contents, and thus proposed an alternative radiolytic cracking pathway of petroleum generation in addition to thermal and microbial mechanisms.…”

mentioning

confidence: 99%

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On the changing petroleum generation properties of Alum Shale over geological time caused by uranium irradiation

Yang

Schulz

Horsfield

et al. 2018

Geochimica et Cosmochimica Acta

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An interdisciplinary study was carried out to unravel organic-inorganic interactions caused by the radiogenic decay of uranium in the immature organic-rich Alum Shale (Middle Cambrian-Lower Ordovician). Based on pyrolysis experiments, uranium content is positively correlated with the gas-oil ratios and the aromaticities of both the free hydrocarbons residing in the rock and the pyrolysis products from its kerogen, indicating that irradiation has had a strong influence on organic matter composition overall and hence on petroleum potential. The Fourier Transform Ion Cyclotron Resonance mass spectrometry data reveal that macro-molecules in the uranium-rich Alum Shale samples are less alkylated than less irradiated counterparts, providing further evidence for structural alteration by αparticle bombardment. In addition, oxygen containing-compounds are enriched in the uranium-rich samples but are not easily degradable into low-molecular-weight products due to irradiation-induced crosslinking. Irradiation has induced changes in organic matter composition throughout the shale's entire ca. 500 Ma history, irrespective of thermal history. This factor has to be taken into account when reconstructing petroleum generation history. The Alum Shale's kerogen underwent catagenesis in the main petroleum kitchen area 420 to 340 Ma bp. Our calculations suggest the kerogen was much more aliphatic and oil-prone after deposition than that after extensive exposure to radiation. In addition, the gas sorption capacity of the organic matter in the Alum Shale can be assumed to have been less developed during Palaeozoic times, in contrast to results gained by sorption experiments performed at the present day, for the same reason. The kerogen reconstruction method developed here precludes overestimations of gas generation and gas retention in the Alum Shale by taking irradiation exposure into account and can thus significantly mitigate charge risk when applied in the explorations for both conventional and unconventional hydrocarbons.

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Section: Oxygen-containing Moietiesmentioning

confidence: 99%

Section: Radiation Dosagementioning

confidence: 99%

mentioning

confidence: 99%

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On the changing petroleum generation properties of Alum Shale over geological time caused by uranium irradiation

Yang

Schulz

Horsfield

et al. 2018

Geochimica et Cosmochimica Acta

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“…Specific reaction and structural rearrangement of hydrocarbons attributed to radiolysis include: (1) an impedance of the hydrogenated production of aliphatic C-H bonds and C-OH groups (Landais, 1996); (2) increased cleavage of aliphatic substituents (Forbes et al, 1988) or cracking of aliphatic chains (Dahl et al, 1988;Jaraula et al, 2015); (3) greater oxidative degradation of OM leading to an increase in oxygenated functional groups and higher O/C ratios (Krǐbek et al, 1999); and (4) a general increase in complexation and redox reactions (Spirakis, 1996;Court et al, 2006;Douglas et al, 2011;Jaraula et al, 2015). A 13 C enrichment of OM exposed to radiation has also been measured and attributed to the higher stability of the heavier isotope to polymerisation (Leventhal and Threlkeld, 1978;Court et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

The composition and radiolysis impact on aromatic hydrocarbons in sedimentary organic matter from the Mulga Rock (Australia) uranium deposit

Greenwood

Shan

Holman

et al. 2018

Organic Geochemistry

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“…For example, uranium radiolysisinduced carbonization of organic matter has been reported for the 500 Ma Alum black shale in Sweden, in which α-decay was interpreted to be the cause of the decomposition of the organic matter and the corresponding decrease in the amount of extractable organic matter (Dahl et al, 1988;Lewan and Buchardt, 1989). Similarly, uranium-induced radiolysis is interpreted to have led to the cleavage of long straight chains in organic matter in the Mulga Rock uranium deposit, forming medium chain-length n-alkyl moieties (Jaraula et al, 2015). However, these studies inferred a relationship between the changes in the organic matter and the presence of uranium but did not demonstrate it directly.…”

Section: Effects Of Natural Uranium Decaymentioning

confidence: 93%

Uranium Mineralization and Its Radioactive Decay-Induced Carbonization in a Black Shale-Hosted Polymetallic Sulfide Ore Layer, Southwest China

Zhu

Luo

et al. 2015

Economic Geology

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The black shale in the Lower Cambrian Niutitang Formation, southwest China, which has been dated to 532.3 ± 0.7 Ma by U-Pb radiometric measurements, hosts a sedimentary layer with abnormally high Ni-Mo-PGE-Au contents. This layer is enriched in Ni (up to 3.8 wt %), Mo (up to 7.7 wt %), and U (up to 595 ppm), but its genesis is still controversial. Here we report the first direct observation of uranium-bearing minerals and their radioactive effects on the surrounding matter in the polymetallic sulfide ore. X-ray absorption fine structure analyses confirmed the reduced valence state of uranium. In combination with high-resolution electron microscopy and electron probe microanalysis, the mineral was identified as coffinite (USiO4). A strong positive correlation between the sizes of the coffinite crystals and their surrounding carbonized rings reveals that the coffinite is authigenic, and its crystallization-produced radiation resulted in the radiolysis of surrounding organic matter. The association of various biogenic metal sulfides, phosphates, and abundant organic substances within the Ni-Mo sulfide-enriched ore suggests that biological adsorption may have participated in the enrichment of soluble U(VI), and that microbial sulfate reduction might have facilitated the uranium mineralization.

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Radiolytic alteration of biopolymers in the Mulga Rock (Australia) uranium deposit

Cited by 29 publications

References 76 publications

On the changing petroleum generation properties of Alum Shale over geological time caused by uranium irradiation

On the changing petroleum generation properties of Alum Shale over geological time caused by uranium irradiation

The composition and radiolysis impact on aromatic hydrocarbons in sedimentary organic matter from the Mulga Rock (Australia) uranium deposit

Uranium Mineralization and Its Radioactive Decay-Induced Carbonization in a Black Shale-Hosted Polymetallic Sulfide Ore Layer, Southwest China

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