H.W. Hagemann

Geological controls on the coal quality of the Mequinenza subbituminous coal deposit, northeast Spain

Abstract The results of geological, petrographical, geochemical and mineralogical studies, performed to determine the coal-forming paleo-environmental conditions which gave rise to anomalous enrichments in organic sulphur, molybdenum and uranium in the Oligocene Mequinenza subbituminous coal deposit of northeastern Spain, are summarized. This paper demonstrates the major influence exerted by the paleohydrology of the depositional framework on the early diagenetic evolution of the precursor peat deposits. The S, Mo and U enrichments, the preservation of aragonite and chlorophillinite, and the high degree of gelification of the Mequinenza coal are a consequence of alkaline syngenetic conditions in the depositional environment. Similar conditions can be inferred for many Mesozoic and Tertiary coal deposits in the Mediterranean region (Mallorca, Sardinia, Hungary, Bulgaria, Serbia, Greece and Turkey). However, the source of sulphur may have been different and have included Triassic and Early Jurassic sulphate recycling scenarios or volcanic sources. Whatever the source, sulphur enrichment is always influenced by the alkaline depositional environments developed in basins generated during the Alpine Cycle in circum-Mediterranean mobile belts.

Influence of organic material on mineralization processes in the Permian Kupferschiefer formation, Poland

Abstract The Permian Kupferschiefer horizon in Southwest Poland acted as a geochemical trap by accumulating metals from an ascending oxidizing brine. The hydrogen-rich organic material in the Kupferschiefer supplied sufficient reduction equivalents for the precipitation of base and precious metals from these brines by redox reactions. This is indicated by regular changes in the molecular composition of the extractable organic material in a set of samples collected from a 1.4 m thick horizon in a Polish mine. The degree of oxidation is shown to change drastically from the bottom to the top of the horizon. In the bottom section, saturated hydrocarbons are diminished and heteroaromatic systems containing oxygen and sulphur are enriched significantly; alkylated aromatic hydrocarbon abundances are relatively low. The ratio of phenanthrene/sum of methylphenanthrenes varies with the degree of oxidation. Spectral fluorescence measurements reveal an increase in fluorescence intensities of the extracts with increasing oxidation. Moreover, the green shift of fluorescence maxima is related to oxidation effects. Parallel to the intensity of oxidation, as observed from changes in the extractable organic matter, the content of copper and silver changes within the horizon. The results confirm that organic matter in sediments, under appropriate geological conditions, can play a significant role in ore formation processes.

New interpretations of the facies of the rhenish brown coal of West Germany

Abstract New ideas concerning the understanding of the facies of the Rhenish brown coal of West Germany are discussed. These new interpretations are based on a significantly larger number of samples and refined procedures for analysis within the field of paleobotany, palynology, coal petrology and organic geochemistry than were available to P. W. Thomson and M. Teichmuller. The light and dark bands in the coal are mainly the result of different degrees of plant decomposition. The influence of the peat-forming plant communities plays a subordinate role in the petrographical composition of these particular strata of the Rhenish brown coal.

Extraction of polycyclic aromatic hydrocarbons from polluted soils with binary and ternary supercritical phases

Abstract Supercritical fluid extractions (SFE) using carbon dioxide and modifiers (n-hexane, cyclohexane, toluene, methyl tert.-butyl ether, methoxybenzene, dichloromethane, propanone, pyridine, methanol) as well as modifier mixtures (methanol-containing diethylamine, 2-aminoethan-1-ol, acetic acid) were performed to extract polycyclic aromatic hydrocarbons (PAHs) from real environmental samples polluted to a minor extent by mineral oil products and highly contaminated by brown coal tar. Comparing the results with those from Soxhlet extraction utilizing dichloromethane and SFE using pure carbon dioxide show that acidic or basic co-solvents give the highest PAH yields in all cases. Extraction efficiency decreases with reduced polarity of the modifier used and increases at higher concentrations of co-solvent. To explain the SFE results we discuss several mechanisms of disruption of matrix–PAH interactions: first the competition between the modifier molecules and the active sites of soils organic and inorganic matter to interact with non-covalent bondings to the analytes; and second the splitting of electron donor–acceptor complexes between humic substances and PAHs induced by Lewis acids or Lewis bases.

The Pliensbachian (Early Jurassic) “anoxic” event in Asturias, northern Spain: Santa Mera Member, Rodiles Formation

The Pliensbachian rhythmite of Asturias (Northern Spain) consists of alternating layers of limestone and marl of postdepositional origin. The sediments are organized in shallowing upwards parasequences of varying energy. Minor scale microcycles are found within the parasequences which probably represent the record of sudden high energy events alternating with quiet hemipelagic or pelagic sedimentation. Organic petrographic and geochemical study of different marly samples throughout the sections did not show significant compositional differences. There are three laterally equivalent intervals with higher TOC and total sulphur contents, higher concentration of aromatic compounds and heterocompounds, higher Pr/n-C 17 and Phy/n-C 18 ratios, and lower Pr/Phy ratio and CPI values. These intervals correspond to the end of the jamesoni zone, the boundary of the ibex and davoei zones and especially the lower part of the margaritatus zone. The uniformity of petrographic and qualitative chemical composition throughout the sections indicates that the nature of the organic matter supply did not change significantly during sedimentation, implying that changes in the conditions of preservation were likely responsible for the formation of the organic-rich intervals. Lower dissolved oxygen conditions probably produced a higher preservation of both organic carbon and aromatic and hetero-compounds, as indicated by the fluorescence properties and the infrared spectra of the extracts.

The geology, petrology, palynology and geochemistry of Permian coal basins in Tanzania. 1. Namwele-Mkomolo, Muze and Galula coalfields

Abstract Permian coal-bearing strata occur in a number of intracratonic rift basins in Tanzania. This study examines coals, shales and mudstones of the Namwele-Mkomolo, Muze and Galula coalfields (Rukwa basin) by coal petrological, palynological and rock eval techniques. For the coals the focus was on the establishment of coal seam characteristics and related quality and utilization potentials, whereas the shales and mudstones were examined for age relationships, flora and related palaeodepositional environments and source rock potential. The coal seams, which have a thickness of up to 2.95 m are high in ash yields (25–63 wt%) and have calorific values ranging from 5344 to 18947 J/g. Typical for many of the seams is their detrital nature as indicated by the high content in finely disseminated clay minerals, quartz and detrital macerals. Pyrite content is variable (0.60–5.81 wt%). Vitrinite reflectance ranges from 0.43 to 0.66% Rrandom (subbituminous to high volatile B bituminous). Use of the coals in small-scale power generations and for domestic use would greatly reduce the dependency of rural Tanzania on wood and wood-derived charcoal as the main source of fuel. Palynomorph assemblages are characterized by the predominance of nontaeniate and taeniate pollen, and trilete spores in the Namwele-Mkomolo and Muze coalfields. At Galula coalfield the palynomorph assemblages were poor (rare trilete, alete and monolete spores). On the basis of age correlations with Karoo basins to the south and the Collie Basin of western Australia, an Artinskian to Kungurian(?) age is suggested for the coal measures in the Rukwa basin. The diversity of palynomorph assemblages suggests a variety of floras and contemporary depositional environments throughout deposition of the Karoo strata. This is consistent with coal petrographic parameter, which would indicate that peat accumulation occurred in upper delta plain, braided plain and lacustrine depositional environments. Rock eval parameters indicate kerogen type III for all samples investigated and indicate very poor hydrocarbon source rock potential.

Palaeogene lacustrine record in Mallorca (NW Mediterranean, Spain): depositional, palaeogeographic and palaeoclimatic implications for the ancient southeastern Iberian margin

Abstract Middle Bartonian (Middl1e Eocene) and Chattian (Upper Oligocene) lacustrine and alluvial-lacustrine successions exist in Mallorca (northwestern Mediterranean). They yield a significant palaeobiological record comprising fossil land plants and vertebrates and constitute the best available depositional record for a preliminary palaeogeographic and palaeoclimatic analysis of the northeastern part of the Palaeogene southern Iberian Margin (western Tethys). Both lacustrine systems developed under similar warm and humid climatic conditions, increasingly affected by seasonal and/or pluriannual rhythms marked by changing precipitation patterns. These climatic conditions were mainly caused by the low palaeolatitude where the lacustrine systems evolved, the still probable although decreasing influence of Indo-Pacific warm surface currents, and the occurrence of very extensive marine water masses adjacent to wide, emerged continental zones. The Palaeogene lacustrine systems were shallow, and characterised by low gradient depositional conditions. They were perennial, open freshwater-oligosaline carbonate lakes where eutrophy, thermal meromixis and anoxic bottom conditions could develop, allowing the accumulation and preservation of macrophytic plant remains of the circum-lacustrine marginal belt and neighbouring terrestrial mesophytic zones. The higher plant/algal-bacterial organic contribution balance favoured the generation of mineable huminitic coal seams, carbominerites and of gas-prone, kerogene type III and IIb source rocks. The hydrogen-bicarbonate-rich waters led to high biogenic and inorganic bio-induced carbonate sediment production. Biogenic muds, cyanobacterial incrustations and travertine and tufa precipitation constituted the major carbonate products. Moreover, the high pH conditions in the lacustrine water bodies and in the lacustrine sediment pore waters favoured bacterial sulphate reduction, contributing to organic sulphur enrichment in coals. These highly alkaline conditions also resulted, in some cases, in the exceptionally good preservation of chlorophyllinite, a rare liptinite maceral recorded in the Eocene coal deposits. The Middle Eocene lacustrine system did not evolve in a very well defined tectonic setting, characterised by the generation of low uplifts and gently subsiding basins. Terrigenous contributions from the source areas and clastic sedimentation were restricted to river mouths. High autochthonous carbonate production and accumulation characterised most of the remaining lacustrine zones. A significant spring recharge of the lacustrine zones is suggested by the well developed spring-related travertine deposits. By contrast, the Oligocene lacustrine zones developed both in fluvial-related floodplains and in the distal zones of a major alluvial system, which was fed from tectonically active source areas located to the NW of the island. A more significant water runoff contribution is suggested for this system although underground recharge could also be substantial.

The geology, petrology, palynology and geochemistry of Permian coal basins in Tanzania: 2. Songwe-Kiwira Coalfield

Abstract This study provides coal quality, petrological, palynological and geochemical (Rock Eval) data on Permian coal seams and associated shales and mudstones of the Karoo Supergroup of the Songwe-Kiwira Coalfield, Tanzania. The coal seams, which have a cumulative thickness of 6.80 m, occur in the shale–coal–sandstone facies of the Mchuchuma Formation of Artinskian to Kungurian(?) age. Coal quality data (calorific values, volatile matter contents) and vitrinite reflectances indicate high volatile C bituminous to high volatile A bituminous coals, having relatively high ash yields (22–49 wt.%) and highly variable sulphur contents (0.17–9.2 wt.%). They could be used to fuel small-scale power generation units thereby providing electricity to nearby towns and villages. Also, the coals could be used as a substitute for wood, which is becoming increasingly scarce. In rural Tanzania, charcoal is still the main energy source for cooking, and wood is used extensively in brick kilns and for making roofing tiles. Petrological analysis indicated that the coals are dominated by dull to banded dull lithotypes, with seams at the base of the Mchuchuma Formation enriched in inertinite macerals (up to 83 vol.%), whereas up-section vitrinite contents increase. Palynological analyses indicated that the assemblage in the lower Mchuchuma Formation ( Scheuringipollenites assemblage) is dominated by trilete spores, whereas in the remainder of the section, non-taeniate disaccates dominate ( Scheuringipollenites–Protohaploxypinus assemblage). Facies critical macerals suggest for most seams a marsh/wet forest swamp depositional setting, which is consistent with the palynological data. Rock Eval analyses indicate type II/III kerogen, with Tmax (°C) values ranging from 426 to 440, corresponding to the early stage of hydrocarbon generation. Thermal Alteration Indices (2 to 2+) and vitrinite reflectance levels (0.60–0.83 Ro (%) support the Rock Eval maturity assessment, and despite the predominance of terrestrial-derived organic matter, there is evidence of oil generation and expulsion in the form of cavity and fracture filling exsudatinite.

Isoarborinol through geological times: Evidence for its presence in the Permian and Triassic

Abstract Optical rotation measurements and HPLC chiral separations using a β-cyclodextrin phase, performed on aromatic hydrocarbons isolated from diverse geological sources, and belonging to the arborane or fernane triterpenoid series, have shown that isoarborinol, one of the possible biological precursors, was abundantly present at the time of deposition of Permian and Triassic sediments. This fact considerably reinforces the hypothesis that arborane derivatives in sediments, often found in abundance in lacustrine or lagoonal environments, must originate from microorganisms such as aerobic bacteria or algae rather than from angiosperms, a group of higher plants whose evolution dates from the Cretaceous and currently believed to be the principal source of isoarborinol.

Facies and rank of the Permian Kupferschiefer from the lower Rhine basin and NW Germany

Abstract The Kupferschiefer of the Lower Rhine Basin and of NW Germany is a typical black shale containing C org values between 0.5 and 9.1%. On average it contains 4% C org . In coal petrographic terms the organic matter of the Kupferschiefer is characterized by well preserved liptinite as sporinite - especially derived from the pollen grains of conifers - in the area of the Lower Rhine Basin and as alginite towards the centre of the Kupferschiefer sea. The high content of bituminite in all of the samples shows that the main source of organic matter is derived from plancton and bacteria. Vitrinite and inertinite are rare. The rank of the organic matter in the sediment varies between the lignite stage (Lower Rhine Basin) and the bituminous coal stage (NW Germany). Geochemical investigations have shown that residual heat from the Krefeld High was active until the lower Zechstein. This has caused a change in the chemical composition of the organic matter but did not express itself in the optical parameters. Inhomogeneities of the organic matter in low-rank and bituminization in higher-rank materials influence the vitrinite reflectance. Fluorescence measurements are more sensitive in sapropelic sediments and oil shales than vitrinite reflectance. It is evident that the red/green ration is more reliable in view of diagenesis studies than the lambda max of the fluorescence spectra. Geochemical parameters are partly much more sensitive towards thermal stress as compared to vitrinite reflectance, e.g. metalloporphyrin concentrations decrease with increasing temperatures. The parameter covers a temperature range from ca. 40°C to 80°C. The weighted average mass of the vanadyl-cycloalkano-porphyrins is suitable to characterize the influence of temperature on the Kupferschiefer between ca. 40°C and 150°C. Summing up, the Kupferschiefer of the Lower Rhine Basin in NW Germany is a sidiment very well suited for parallel petrographic and organic-geochemical research. The results of this might be also of interest in the field of oil prospecting.