Structural order and disorder in Precambrian kerogens

Buseck, Peter R.; Huang, Bojun; Miner, B.

doi:10.1016/0146-6380(88)90260-4

Cited by 39 publications

(19 citation statements)

References 20 publications

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“…Because carbon has a much lower atomic mass and scatters electrons less effi ciently than silicon, it appears bright against the microcrystalline quartz. Graphite lattice fringes, as seen in poorly graphitized kerogen (Buseck et al 1988;Miner 1988), are absent from high-resolution images.…”

Section: Resultsmentioning

confidence: 94%

“…Transmission electron microscopy (TEM) and associated techniques are powerful tools for the study of structural order and bonding in kerogens and other carbon phases (Buseck et al 1988). Electron energy loss spectroscopy (EELS) provides information about the electronic structure of elements in the sample (i.e., carbon) and is very sensitive to the bonding differences between disordered forms of carbon.…”

Section: Introductionmentioning

confidence: 99%

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The structure and distribution of carbon in 3.5 Ga Apex chert: Implications for the biogenicity of Earth's oldest putative microfossils

Gregorio

Sharp

2006

American Mineralogist

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The oldest putative microfossils on Earth occur in the 3.5 Ga Apex chert of the Warrawoona Group, Western Australia. We have analyzed disseminated interstitial carbon found within Apex chert using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) to address the controversy regarding its state of structural disorder. We found that the carbonaceous material is structurally amorphous, with no evidence of graphitization, and contains aromatic domains, most likely as polyaromatic ring structures, similar to preserved kerogen in bona fi de microfossils. In addition, amorphous carbonaceous material occurs as a grain boundary phase between quartz crystals and within fl uid inclusions in quartz crystals, indicating that hydrocarbons moved through the chert during crystallization and hydrothermal alteration. The results suggest that the carbonaceous material is similar in structure to microfossil kerogen, implying the microbe-like features within Apex chert are also microfossils. However, this kerogen-like material may also be produced abiotically via FischerTropsch-type (FTT) synthesis reactions in an ancient hydrothermal vent.

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Section: Resultsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

The structure and distribution of carbon in 3.5 Ga Apex chert: Implications for the biogenicity of Earth's oldest putative microfossils

Gregorio

Sharp

2006

American Mineralogist

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“…3 The subscript (c) denotes the crystalline state. Although immature type-II kerogens with relatively high (H/C)s are generally amorphous (Tissot and Welte, 1984), it has been demonstrated that kerogen crystallinity increases with decreasing H/C of the kerogen during the maturation process (e.g., see Oberlin et al, 1974;Wedeking and Hayes, 1983;Buseck and Bo-Jun, 1985;Buseck et al, 1988;Koch and Christiansen, 1993;Wopenka and Pasteris, 1993;Jehlička et al, 1997;Beyssac et al, 2002). Because kerogens with relatively high (H/C)s cannot achieve metastable equilibrium with crude oil and mature kerogen (see below), their degree of crystallinity has no effect on thermodynamic description and interpretation of metastable equilibrium states among mature kerogen, crude oil, and CO 2 gas like the one represented by the right side of Reaction (A).…”

Section: Reconnaissance Calculation Of the Relative Metastabilities Omentioning

confidence: 98%

A chemical and thermodynamic model of oil generation in hydrocarbon source rocks

Helgeson

Richard

McKenzie

et al. 2009

Geochimica et Cosmochimica Acta

115

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“…Such microtextural heterogeneity has been described also for di †erent Precambrian kerogens. 30 This heterogeneity has been well described for many solid bitumens from the Bohemian Massif, especially for the M• tov bitumens.…”

Section: Resultsmentioning

confidence: 97%

Raman microspectrometry of accumulated non-graphitized solid bitumens

Jehlička

Beny

Rouzaud

1997

J. Raman Spectrosc.

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Solid bitumens (SB) occur accumulated in sedimentary, metasedimentary and volcanic rocks from the central and western part of the Bohemian Massif (Czech Republic). Structural features of asphaltic-like (ALSB) and hard (HSB) solid bitumens from sedimentary and metasedimentary rocks of Paleozoic and Precambrian age have been obtained using Raman microspectrometry. Structural and microtextural imaging were carried out using the lattice fringes mode of transmission electron microscopy (TEM). Weakly carbonized ALSB of sedimentary origin are characterized by a relatively high H/C atomic ratio (about 1) and di †er from highly carbonized HSB from basaltic rocks (H/C atomic ratio about 0.1) which cross-cut a black shale formation of Upper Proterozoic age. Both these groups of accumulated forms of SB di †er from dispersed kerogens, isolated from regionally metamorphosed black shales of the same primary sedimentary basin. First-order Raman spectra of both ALSB and HSB di †er considerably from those obtained on dispersed carbonaceous matter forms from black shales and schists (from nonmetamorphic to medium range biotite metamorphic zone). SB display a higher surface ratio of the 1350 to the 1582 cm-1 Raman bands (0.8-2.2) and higher half-width of the 1582 cm-1Raman band (65-73 cm-1) in (E 2g ) comparison with dispersed forms (0.1-1.2 and 21-55 cm-1, respectively). Only HSB display second-order Raman spectra : the Ðrst band at 2680 cm-1 is broad and the second band at 2930 cm-1 is sharp. These features of the Raman spectra conÐrm the low structural order of SB, which is in agreement with X-ray and TEM results. 1997

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Structural order and disorder in Precambrian kerogens

Cited by 39 publications

References 20 publications

The structure and distribution of carbon in 3.5 Ga Apex chert: Implications for the biogenicity of Earth's oldest putative microfossils

The structure and distribution of carbon in 3.5 Ga Apex chert: Implications for the biogenicity of Earth's oldest putative microfossils

A chemical and thermodynamic model of oil generation in hydrocarbon source rocks

Raman microspectrometry of accumulated non-graphitized solid bitumens

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