Jan Jehlička

Application of Raman microspectrometry in the study of structural changes in Precambrian kerogens during regional metamorphism

Abstract A series of kerogens, isolated from Upper Proterozoic shales and schists from a regionally metamorphosed complex (Barrandian region, Czechoslovakia), were examined by Raman microspectrometry. Changes in the spectra indicate evolution in the chemical structure of the kerogen in the direction of the metamorphic gradient.

First and second order Raman spectra of natural highly carbonified organic compounds from metamorphic rocks

Abstract Major structural differences observed while studying highly carbonified natural organic matter from rocks using Raman microspectrometry reflect postsdiagenetic transformation processes. The mode of occurrence of organic matter is however another important factor governing structural changes. Raman microspectrometry is a useful tool for the estimation of the structural order and the presence of structural defects in carbonaceous matter. Obtained parameters are to be compared carefully especially in the study of homogeneous series of carbonaceous samples – those having the same geological age, originating from rocks of similar lithology and mode of occurrence. Not only frequencies of major Raman first and second order bands but also the evolution of parameters as half band of the O (E2g2) and G′ are to be measured to describe the transformation of the structure in connection with metamorphism.

Terrestrial and Extraterrestrial Fullerenes

Abstract This paper reviews reports of occurrences of fullerenes in circumstellar media, interstellar media, meteorites, interplanetary dust particles (IDPs), lunar rocks, hard terrestrial rocks from Shunga (Russia), Sudbury (Canada) and Mitov (Czech Republic), coal, terrestrial sediments from the Cretaceous‐Tertiary‐Boundary and Permian‐Triassic‐Boundary, fulgurite, ink sticks, dinosaur eggs, and a tree char. The occurrences are discussed in the context of known and postulated processes of fullerene formation, including the suggestion that some natural fullerenes might have formed from biological (algal) remains.

RAMAN MICROSPECTROMETRY OF ACCUMULATED NON-GRAPHITIZED SOLID BITUMENS

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 differ 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 differ from dispersed kerogens, isolated from regionally metamorphosed black shales of the same primary sedimentary basin. First-order Raman spectra of both ALSB and HSB differ considerably from those obtained on dispersed carbonaceous matter forms from black shales and schists (from non-metamorphic 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-1 (E2g) Raman band (65–73 cm-1) in comparison with dispersed forms (0.1–1.2 and 21–55 cm-1, respectively). Only HSB display second-order Raman spectra: the first band at 2680 cm-1 is broad and the second band at 2930 cm-1 is sharp. These features of the Raman spectra confirm the low structural order of SB, which is in agreement with X-ray and TEM results.

Evidence for fullerenes in solid bitumen from pillow lavas of Proterozoic age from Mítov (Bohemian Massif, Czech Republic)

Abstract Andesitic pillow lavas containing biogenic, solid bitumen (SB) are a constituent of a Neoproterozoic volcanosedimentary sequence (Tepla-Barrandian unit, Bohemian Massif) in the Mitov area of the Czech Republic. A black shale formation that is crosscut by these andesitic basalts is 565 Ma old. Carbon disulfide extracts of two powdered samples of SB contain 0.2 and 0.3 ppm of C 60 , respectively, as determined by high-pressure liquid chromatography. The peak assignment based on retention time is fully supported by high-resolution electron ionization mass spectrometry (EI-MS). No C 70 was detected, nor was C 60 found in two other SB samples from this locality. Other investigated carbonaceous samples from Bohemia (coals and anthracites of Upper Paleozoic age and anthraxolite, graphitoids, and graphite of Upper Proterozoic age) did not contain fullerenes at concentrations above the detection limit of 0.01 ppm. The absence of C 60 in these samples was confirmed by EI-MS. The proposed mechanism of fullerene formation involves a primary algal phase, generation of a hydrocarbonaceous mixture in the course of thermal evolution of the sedimentary series, and their high-temperature transformation related to the extrusion of basalt. An important feature for fullerene conservation was the enclosure of fullerenes in SB with a structure similar to glasslike carbon, where the fullerene was protected against oxidation.

The leaching behaviour of lead metallurgical slag in high-molecular-weight (HMW) organic solutions

Abstract The reactivity of primary Pb metallurgical slags in high-molecular-weight (HMW) organic solutions has been studied in order to determine the processes of release and attenuation of metal and metalloid contaminants (Pb, Zn, Cu, As) in ‘soil-like’ environments. Slag was submitted to a 112-day batch leaching experiment in Suwannee River fulvic acid solution and peat water (~50 mg DOC 1-1). The leaching was coupled with investigation of the secondary phases (SEM/EDS, Raman microspectrometry) and thermodynamic speciation-solubility modelling using MINTEQA2. Metals and As are released in large amounts during the early stage of the experiment, followed by a decrease in the concentrations in the leachate as a result of adsorption on secondary (hydrous) ferric oxides (HFO/FO), predicted by MINTEQA2 calculations and confirmed on the leached slag surface by SEM and Raman spectrometry. Compared to other contaminants, Zn exhibits more pronounced mobility and is adsorbed on HFO/FO only at pH >7. Such a scavenging process may be predominant during the long-term interaction of slag with an HMW organic solution of real soil. As a result, the soil cover and subsequent re-vegetation of slag dumps may be considered as a possible scenario for slag management.

Organic geochemistry of precambrian shales and schists (Bohemian massif, Central Europe)

Abstract The composition and the structure of kerogens and subgraphitic materials from Upper Proteroic regionally metamorphosed black shales were investigated by different physico-chemical method. The isotopic composition of carbon changes with the intensity of the regional metamorphism. Kerogens from low-grade metasediments have averaged δ 13 C values—35%, kerogens from chlorite and biotite zones—31%. Samples display high diversity of primary sedimentary materialos. Details were obtained using transmission electron microscopy (TEM). Crystalline order improves with the intensity of the regional metamorophism. Turbostratic carbonacveous matter is described from low-grade metasediments, graphite occurs at the end of the biotite zone; however, both metallogenetic and contact metamorphic processes can be involved. In some samples the second form of graphite has been identified, probably of detrital origin, inherited from some high-grade metamorphic area existing at the time of sedimentation of primary rocks.

Fullerenes in Solid Bitumens from Pillow Lavas of Precambrian Age (MÍTOV, Bohemian Massif)

Abstract At Mitov solid bitumens occur in pillow lavas cutting black shale formation of Precambrian age. They represent non-graphitised carbons and contain about 0.2 ppm of C60.

Transmission Electron Microscopy of Carbonaceous Matter in Precambrian Shungite from Karelia

Shungite is a solid bitumen which represents highly condensed carbonaceous matter from a Precambrian regionally metamorphosed area in Shunga (Karelia, USSR). Its chemical structure differs considerably in comparison with other types of solid bitumen. Structural inhomogeneity is a characteristic feature of this carbonaceous matter. The structure of shungite is a result of some process which oxidized primary organic matter of probably algal origin, and of the conditions of regional metamorphism.

Fullerene C60 in Solid Bitumen Accumulations in Neo-Proterozoic Pillow-Lavas at Mítov (Bohemian Massif)

Fullerene C60 occurs at extremely low concentration (0.2—0.3 ppm) in hard solid bitumen that was accumulated in the pillow lava bodies exposed at Mitov (Tepla-Barrandian Neo-proterozoic of the Bohemian Massif). No higher fullerenes were documented. The C60 fullerene and its precursors are present in non-graphitic and non-graphitizable carbonaceous matter. Inclusions of fullerene are found embedded within glass-like carbons that are found within the pillow lava bodies. Rare fullerenes in Mitov were probably preserved in the closed micropores and mesopores of the glass-like, solid bitumen. Pyrolysis of biogenic PAHs precursors seems a plausible way to form fullerenes in geological environments.