concentration and character of pahs and other hydrocarbons in coals of varying rank implications for environmental studies of soils and sediments containing particulate coal abstract particulate coal can occur in soils and sediments from both natural and anthropogenic sources its presence can influence the concentrations of regulated and more bioavailable pollutants through its geosorbent qualities and its own contribution of total extractable hydrocarbons teh including polycyclic aromatic hydrocarbons pahs and biomarkers extractable pahs in coal also can potentially affect pah based source and maturity ratios of soil or sediment extracts which can be used to assess the source s of pahs this study reports on the absolute concentrations of teh the 16 priority pollutant pahs 27 alkylated pahs and sulfur containing aromatics and selected biomarkers in 15 coals ranging in rank from lignite to anthracite unlike most previous studies in the fuel science or geochemical literature the coals herein were extracted using dichloromethane at room temperature an epa method 3500 type method common in environmental laboratories thereby allowing comparison of these results to environmental studies the concentrations of teh ranged from 8 2 to 2500 g g coal dry wt with a maximum yield among high volatile bituminous coals the teh fingerprints were variable and some of these resembled those of other forms of contamination the concentrations of priority pollutant pahs ranged from 35 to 11 000 ng g coal dry wt or 38 to 12 000 ng g carbon and varied with coal rank reaching a maximum within the high volatile bituminous rank the distributions of extractable pahs and numerous pah ratios conventionally used as source and or maturity parameters also varied with coal rank emphasizing that particulate coal in soils and sediments cannot be universally represented by a single set of diagnostic parameters hopanoid and sterane biomarker yields also varied with rank reaching a maximum in high volatile bituminous coals and were low relative to pahs because particulate coal often co occurs with other sources of hydrocarbons in soils and sediments the data presented herein may prove useful in allocating coal versus non coal sources on a mass balance basis

radiation and self ignition induced alterations of permian uraniferous coal from the abandoned novator mine waste dump czech republic abstract the effects of uranium mineralization and self burning processes on inorganic and organic components of coal have been studied at a waste pile of the former novator coal and uranium mine at beckov intrasudetic basin czech republic in order to characterize physical and chemical properties of wastes as a basis for further environmental studies unaltered bituminous coal was composed predominantly of vitrinite with random reflectance values between 0 72 and 0 86 and inertinite less common liptinite macerals and a low level of organic solvent extractable material 0 01 1 33 wt uranium minerals caused local radioactive alterations in the uranium enriched coal matrix the diameter of rounded radiation induced haloes ranged from 0 35 to 100 m with higher reflectance 0 84 3 44 compared with bulk coal structural changes in radiation induced altered organic coal matter were characterized by low values of raman band disorder fewer aliphatic c h bonds and higher levels of oxygenated functional groups in micro infrared spectra zones of higher reflectance were also confined to veinlets of epigenetic chalcopyrite galena and sphalerite mineralization oriented perpendicularly to the coal bedding the methylnaphthalene ratios mnr of extracted organic matter correlated with uranium concentrations in individual samples in self ignition affected samples the higher reflectance 1 31 1 71 and values of raman band disorder mirrored the intensity of burning processes organic matter samples located at unburnt and burnt coal interfaces were composed of a mixture of coal macerals char and solid bitumens in the waste heap burning zone coal and claystone were transformed to clinkers composed of plagioclase pyroxenes tremolite hematite magnetite anatase and aluminosilicate glass or to paralava formed by porous cordierite and hematite organic components in the burnt out zone were represented by small dense and massive coke particles with reflectance of 4 48 fusinite with reflectance of 3 05 and rare coke droplets of solid bitumen r 1 90 only traces of phenanthrene and alkanes were identified in organic extracts of burnt out rock

spin states and hyperfine interactions of iron in mg fe sio3 perovskite under pressure abstract with the guidance of first principles phonon calculations we have searched and found several metastable equilibrium sites for substitutional ferrous iron in mgsio 3 perovskite in the relevant energy range there are two distinct sites for high spin one for low spin and one for intermediate spin iron because of variable d orbital occupancy across these sites the two competing high spin sites have different iron quadrupole splittings qs at low pressure the high spin iron with qs of 2 3 2 5 mm s is more stable while the high spin iron with qs of 3 3 3 6 mm s is more favorable at higher pressure the crossover occurs between 4 and 24 gpa depending on the choice of exchange correlation functional and the inclusion of on site coulomb interaction hubbard u our calculation supports the notion that the transition observed in recent mossbauer spectra corresponds to an atomic site change rather than a spin state crossover our result also helps to explain the lack of anomaly in the compression curve of iron bearing silicate perovskite in the presence of a large change of quadrupole splitting and provides important guidance for future studies of thermodynamic properties of this phase

trace element behaviour during migmatization evidence for a complex melt residuum fluid interaction in the st malo migmatitic dome france the st malo migmatitic dome represents an interesting example wherein migmatites arise from the anatexis of the surrounding gneisses petrographical and chemical data suggest that leucosome compositions are compatible with partial melting of the quartzo feldsphathic fraction of the parent gneiss the contribution of the incongruent melting of biotite to the melt does not exceed 5 of the parent rock

source apportionment of the hydrocarbon background in sediment cores from hecate strait a pristine sea on the west coast of british columbia canada abstract significant reserves of oil and gas have been predicted for hecate strait a pristine semi enclosed sea on the continental shelf adjacent to british columbia on the west coast of canada to establish a baseline for the natural background of hydrocarbons in sediment prior to any further offshore oil and gas development or increase in oil tanker traffic in the hecate strait region three sediment box cores were collected along a west to east transect across southern hecate strait in september 2003 210 pb measurements established that the bottom sections date to 1920 pre 1800 and 1870 respectively which predate any significant industrial development on the coast alkane and polycyclic aromatic hydrocarbon pah concentrations are low in most sediment samples and both the concentrations and fluxes differ little between surface and bottom core sections pah profiles exhibit a dominance of alkyl pahs for each alkyl pah homologous series with varying amounts of parent unsubstituted pahs while alkane chromatograms show no unresolved complex mixture ucm and there is little change in composition between present day and pre 1800 sediments for most parameters principal components analysis pca models and pah and biomarker ratios indicate that composition patterns are consistent with low and varying natural petrogenic and pyrogenic inputs with little or no anthropogenic input the most likely primary source of petrogenic pahs to the sediments is cenozoic lignites from the skonun formation which outcrops on haida gwai and underlies most of hecate strait two subsurface sections deposited in 1990 and 1930 in the core from milbanke sound on the east side of the transect have elevated concentrations for the alkyl phenanthrene anthracenes and dibenzothiophenes with no ucm and most likely also have a source in immature coal this study suggests that the hecate strait environment has low hydrocarbon concentrations with an apparent minor role for oil seeps and a likelihood that most of the petrogenic pah sources are shales or immature coals with limited pah bioavailability if these characteristics are representative of hecate strait sediments overlying the queen charlotte basin it may mean that biota are likely unadapted to the presence of oil and thus would be more sensitive to exposure to oil from an oil spill than those in a more impacted environment

a hypothesis for the origin of perylene based on its low abundance in sediments of green bay wisconsin abstract perylene a polycyclic aromatic hydrocarbon pah that is common in sediments is believed to originate principally from anaerobic diagenesis of organic matter but its precursor material remains enigmatic we have investigated the formation of perylene in a dated sediment core from green bay wi comparisons of sedimentary profiles of perylene anthropogenic pahs land plant derived hydrocarbons and aquatic contributions of organic matter rule out a specific industrial terrigenous or aquatic precursor for perylene instead perylene seems to be formed from any kind of organic matter as a consequence of a specific type of microbial activity in sub bottom sediments despite an abundance of organic matter the amount of perylene is low in green bay and in other organic carbon rich lake sediments the abundant availability of organic matter that stimulates microbial activity in green bay sediments would seem to favor perylene formation in such sediments we therefore hypothesize that the microorganisms responsible for perylene formation do not compete successfully with those that flourish in sediments rich in organic matter perylene formation consequently does not become significant until deeper in sediments after the more reactive types of organic matter have been consumed

a review of the biogeochemical controls on the occurrence and distribution of polycyclic aromatic compounds pacs in coals abstract the organic matter in coal contains polycyclic aromatic compounds pacs of varying quantities in diverse soluble and insoluble forms pacs in coal are of special interest for organic geochemical studies because they have been successfully used as biological marker compounds biomarkers and indicators of thermal maturity in addition they could provide critical information to understand the structural and compositional evolution of the coal organic matters during coalification and to predict pac releasing characteristics during coal utilization the main purpose of this paper is to provide a critical review on the current state of knowledge on the potential use of pac composition to understand the underlying biogeochemical factors that control pac occurrence and distribution in coal the published pac data of world coal are first compiled according to their ranks natural coke anthracite semi anthracite bituminous coal low volatile bituminous coal medium volatile bituminous coal high volatile bituminous coal sub bituminous coal lignite countries brazil canada china france germany japan usa formation periods carboniferous permian jurassic cretaceous early middle cenozoic then the biogeochemical factors affecting the occurrence and distribution of pacs in coal including biogenic precursor materials coal rank maceral composition depositional environment and geological settings are comprehensively reviewed the results show that the geochemical parameters of pacs in coal are robust tools to trace the coalification processes from the molecular perspectives and to understand the corresponding biogeochemical process e g depositional environment geological settings igneous intrusion occurring during coal formation

thermal constraints on the tectonic evolution of a metamorphic core complex santa catalina mountains arizona abstract we present an analysis of the thermal evolution of the metamorphic core complex of the santa catalina rincon and tortolita mountains in south arizona the structural and kinematic data are briefly reviewed granite mylonites result from three successive shearing events respectively compressional top west during paleocene and top ne during mid eocene and extensional top sw after eocene in a preliminary part of the paper available radiometric data are reviewed in detail for both deformed and undeformed granites with closing temperatures from 565 to 105 c these data are then used to constrain the temperature history for three intrusions which were emplaced respectively during paleocene eocene and miocene times the general temperature time curve shows 1 rapid cooling for the three intrusions just after emplacement and 2 a large and rapid cooling of the entire complex between 35 and 22 ma from 530 to 100 c in the final part this thermal history is used to constrain the tectonic history of the metamorphic core complex the thermal effects of erosion tectonic denudation homogeneous and heterogeneous thinning are computed using a finite difference scheme in one dimension an analysis of the parameters involved in the models shows that the crust of the santa catalina metamorphic core complex has undergone mainly a thinning of its upper part of at least 15 km and more reasonably 20 25 km in less than 10 ma this estimation is discussed considering thermal effects of magmatism

the genesis of coal from the viewpoint of coal petrology abstract the genesis of the microscopic constituents of coal macerals and of maceral associations microlithotypes representing various coal facies is discussed in the light of recent advances that have been made in the study of coals and modern peats peat microscopy especially promoted the understanding of humification and biological gelification both of which are decisive for the genesis of huminites vitrinites in brown coals and hard coals respectively microbial activity during peatification has been documented by chemists microbiologists and petrologists and recently by electron microscopical observations in coals this activity leads to the incorporation of lipid substances into the humic matter and later influences the chemical physical and technological properties of vitrinites geochemical gelification transforms the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal in this process the hydrogel brown coal is transformed to the bitumogel bituminous coal coal as a source rock for oil has become an important research subject for coal petrologists and oil exploration the formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to the coalification jumps of the macerals especially liptinites and vitrinites and to the generation of secondary macerals like exsudatinite bitumen and micrinite dead carbon bituminization in coal has been revealed by the use of fluorescence microscopy which also found the presence of new liptinite macerals bituminite fluorinite and exsudatinite and suggests a higher proportion of algal material in coals than was thought earlier the genesis of various types of inertinite macerals will probably become an increasingly important subject of research especially with regard to rank inertinites that seem to attain their high inertinitic reflectance initially during coalification besides the origin of macerals the origin of various coal facies in terms of maceral associations is considered in relation to the palaeogeographic depositional milieu the peat forming vegetation palaeoclimate water and nutrient supply acidity marine and calcareous influence and fire with examples from euramerican carboniferous coals gondwana coals and tertiary brown coals vegetation water and oxygen supply eh conditions are most important for the generation of coal facies vegetation has been reconstructed with the help of palaeobotany including palynology cuticular analysis and wood anatomy in brown coals and with the study of petrified permineralized peats preserved in coal balls the microscopical investigations of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative however the results of palynological and cuticular analyses should be evaluated with caution considering the varying resistance of palynomorphs and cuticles and in the case of palynomorphs their possible extrapaludal origin microscopical studies of modern peats that were derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies especially in brown coals the much disputed origin of brown coal lithotypes is considered in detail for hard coals there seems to be agreement that coal layers rich in vitrites and liptinite poor clarite were deposited in wet forest swamps that microlayered liptinite rich clarites are sub aquatic humic muds and that inertinite rich durites represent oxidized peats the origin of liptinite rich durites is controversial either subaquatic muds or oxidized peats the latter perhaps from raised bogs a recent trend in the literature is the assumption that many if not all mineable coal seams have been deposited in raised bogs under ombrogenous oligotrophic conditions although raised bogs with a dense arborescent vegetation are known from borneo it seems not probable that most seams which were deposited in foredeeps or steadily sinking graben zones are of ombrogenous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for occasional seams but as in modern peats striking changes of coal facies are commonly caused by hydrological events e g inundations as a consequences of crevasses or of fires that burned the peat the origin of the inertinite rich gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub arctic peats is recommended coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite as well as by hydrogen rich vitrinites with a relatively low reflectance and high fluorescence all due to a strong bacterial activity in peats of low acidity proposals for further research are made in the conclusions

middle to late holocene environmental changes in the depositional system of the tropical brackish bolgoda lake coastal southwest sri lanka abstract the tropical bolgoda lake is one of the largest lagoonal estuaries in sri lanka organic constituents in this lake were investigated using 28 surface sediments three cores from the lake and four short cores from mangrove mud elemental and molecular compositions of sediments and living organic matter om were determined using cns elemental analysis and gas chromatography mass spectrometry respectively chronology of events was determined using accelerated mass spectrometry ams 14 c data for bulk oms woods and mollusk shells the history of bolgoda lake can be divided into two major chrono stratigraphic divisions namely a lower sedimentary succession from ca 7 0 cal ky b p to 2 5 cal ky b p and an upper sedimentary succession from ca 2 5 cal ky b p to the recent according to the sapropelic depositional system concentrations of the mangrove biomarker taraxone increased significantly at ca 7 0 cal ky b p the lower part of the sediment sequence had moderate productivity and was mainly deposited under marine terrestrial influence in oxygen poor anoxic conditions during mid holocene sea level highstands a drastic increase in total organic carbon toc content reaching 29 was found in one of the bolgoda cores this increase occurred because of sea level regression at about 2 5 cal ky b p this change was probably caused by development of a beach rock sandbar and the estuary system changed to a semi closed lake due to the sea level regression as a result aquatic vascular plants predominate in this depositional system after ca 2 5 cal ky b p toc content decreased slightly but relatively high toc contents were maintained in the muddy sediments in moderately sized and shallow 1 2 m tropical estuaries lagoons such as bolgoda lake drastic changes in toc contents may be the most sensitive indicator of sea level variations increase in higher plant om with higher n c 29 n c all and n c 37 n c all alkane ratios also suggest a climatic transition from wetter to somewhat drier after the middle holocene accumulations of pyrogenic polycyclic aromatic hydrocarbons pahs in the modern sediments record anthropogenic activity after european settlement in the 15th century

variable variscan thermal rejuvenation in the st malo region cadomian orogen france evidence from 40ar 39ar mineral ages abstract the st malo region in north west france contains migmatites and anatectic granites derived by partial melting of metasedimentary protoliths during cadomian orogenesis at c 540 ma previously reported rb sr model ages for muscovite and biotite range from c 550 to c 300 ma and suggest variable resetting of mineral isotopic systems these rocks display microscopic evidence for variably intense cadomian intracrystalline plastic strain but record no obvious evidence of penetrative palaeozoic regional deformation 40ar 39ar mineral ages have been determined to evaluate better the extent timing and significance of palaeozoic overprinting eleven muscovite concentrates and one whole rock phyllite have been prepared from various units exposed in the st malo and adjacent mancellian regions in the mancellian region muscovite from two facies of the bonnemain granite complex record 40ar 39ar plateau ages of c 527 and 521 ma an internally discordant 40ar 39ar release spectrum characterizes muscovite from protomylonitic granite within the cadomian alexain deux evailles ize granite complex and probably records the effects of variscan displacement along the north armorican shear zone muscovite concentrates from anatectic granite and from cadomian mylonites along ductile shear zones within the north western sector of the st malo region exhibit internally discordant 40ar 39ar release spectra which suggest variable and partial late palaeozoic rejuvenation by contrast muscovite concentrates from samples of variably mylonitic brioverian metasedimentary rocks exposed within the south eastern sector of the st malo region display internally concordant apparent age spectra which define plateaux of 326 320 ma a whole rock phyllite sample from brioverian metasedimentary rocks exposed along the eastern boundary of the st malo region displays an internally discordant argon release pattern which is interpreted to reflect the effects of a partial late palaeozoic thermal overprint muscovite from the plelan granite part of the variscan plelan bobital granite complex yields a 40ar 39ar plateau age of c 307 ma the 40ar 39ar results indicate that cadomian rocks of the st malo region have undergone a widespread and variable palaeozoic carboniferous rejuvenation of intracrystalline argon systems which apparently did not affect the mancellian region this rejuvenation was not accompanied by penetrative regional deformation and was probably of a static thermal hydrothermal origin the heat source for rejuvenation was probably either the result of heating during variscan extension or advection from variscan granites which are argued to underlie the st malo region

source apportionment of elevated pah concentrations in sediments near deep marine outfalls in esquimalt and victoria bc canada is coal from an 1891 shipwreck the source abstract previous studies have suggested that coal from the 1891 shipwreck of a collier off victoria bc canada is responsible for elevated parent unsubstituted pah concentrations in sediments near deep marine outfalls from esquimalt and victoria in the strait of juan de fuca to resolve this question we analysed a comprehensive suite of resolved and unresolved complex mixture ucm alkanes tricyclic terpane hopane and sterane biomarkers and parent and alkyl polycyclic aromatic hydrocarbons pahs in samples of coal wastewater and sediments composition patterns principal components analysis pca models and pah and biomarker ratios all indicate that coal from the collier does not make a dominant contribution to any sediment sample mass balance calculations based on the n c 24 content and 24 4 tetracyclic terpane to 26 3r tricyclic terpane ratio in coal provide a particularly good match between predicted and observed alkyl pah concentrations for sediments with high alkyl naphthalenes and phenanthrene anthracenes and low ucm but the predicted coal contribution substantially underestimates the measured parent pahs for all sediment samples methylbenz a anthracene chrysene profiles for sediments with a dominance of parent pahs are very close to coal tar with a marked predominance of methylbenz a anthracenes and the possible 10 methylbenz a anthracene as a major constituent while the methylchrysenes predominate in coal hence coal from the collier could account for most alkyl pahs in the sediments but dredged sediment containing pyrolised coal waste from a former coal gas plant in victoria harbour is a more likely source for the samples with elevated parent pahs pah ratios indicate that these sources are superimposed on combustion pahs introduced by a combination of atmospheric deposition and delivery via stormwater and the outfalls parent pah distributions also suggest that pahs in wastewater that originate from oils and soot in liquid fossil fuel combustion are dispersed and degraded while the larger wood char particles containing pahs more protected from degradation settle closer to the outfalls overall results suggest that pahs have predominant sources in wood combustion coal and possibly coke with a likelihood of much lower bioavailability than would be expected from wastewater dominated by oils and soot from vehicle combustion

the cadomian granites of mancellia northeast armorican massif of france relationship to the st malo migmatite belt petrogenesis and tectonic setting abstract the north armorican shear zone nasz divides the cadomian belt of the armorican massif of france into two major terranes the north armorican composite terrane nact and the central armorican terrane cat the nact is a pastiche of displaced blocks and terranes st brieuc terrane st malo terrane and mancellian terrane which results from the amalgamation of cadomian continental arc and basin complexes by sinistral transpression along a continental margin above a southerly dipping subduction zone in the nact the neoproterozoic brioverian succession was deformed and metamorphosed during the cadomian orogeny and intruded by syn to post tectonic plutonic complexes the st malo migmatite belt is a syn tectonic suite of anatectic migmatites derived through partial melting of the brioverian succession using the t test on whole rock geochemical data there is no evidence to suggest that a sample of st malo diatexites comes from a population with a different mean than some samples of the brioverian succession sandstones resulting homogeneous diatexites anatectic granites of the core were emplaced syn kinematically into cadomian strike slip shear zones thus the age of anatexis of 540 ma is also the date of strike slip shearing and provides a minimum age for the sinistral transpression which amalgamated the terranes of the nact the mancellian granites to the southeast of the st malo migmatites were emplaced at 540 ma and are overlain unconformably by cambrian sediments overall geochemistry and a variety of specific geochemical parameters show that the mancellian granites are similar to the diatexites and anatectic granites of the st malo migmatite belt using the t test on whole rock geochemical data there is no evidence to suggest that the sample of mancellian granites comes from a population with a different mean than the sample of st malo diatexites additionally both suites of rocks are peraluminous they have similar distributions of rb sr and ba they have k rb ratios around 225 and they plot largely within the vag field using trace element discrimination diagrams for the interpretation of tectonic setting samples of the brioverian succession sandstones the st malo migmatites and the mancellian granites all exhibit similar primordial mantle normalized element patterns preliminary results of nd and sr isotope studies reveal a similar restricted range of values for nd between 4 0 and 7 3 and sr between 3 and 42 and depleted model ages in the range 1 7 to 1 5 ga tdmur for both mancellian granites and st malo migmatites isotopic features which set these rock types apart from other cadomian granites within the nact the st malo migmatite belt and the mancellian granites are coeval at 540 ma and both developed by anatexis at intermediate crustal depths of the brioverian succession within an inverted but only moderately overthickened behindarc basin in comparison with the st malo migmatites the mancellian granites represent farther travelled products of intracrustal melting but their geochemistry still preserves the characteristic signature of the source

the petrology organic geochemistry and palynology of tertiary age eureka sound group coals arctic canada abstract tertiary age lignites from arctic canada were analysed by petrographical palynological and organic geochemical methods results from petrographic analyses indicate the predominance of wood derived macerals humotelinite group in seams from the strathcona and stenkul fiord areas whereas in the bache peninsula area many seams are characterized by the predominance of detrital macerals humodetrinite and have also higher inertinite contents palynological assemblages are dominated by taxodiaceae pollen whereas pinaceae pollen and pteridophyte spores are less common angiosperm derived pollen contents are quite variable organic geochemical results indicate that norisopimarane and pimarane are the most abundant diterpenoids cadalene was present in the aromatic fractions of all samples with other components such as simonellite and retene in variable abundance rock eval data obtained from stenkul fiord area samples indicate low petroleum generation potential for this predominantly woody material the depositional environment at strathcona and stenkul fiords was that of a forested swamp which formed in a lagoonal alluvial plain setting palynomorph assemblages petrographic indices and the abundance of diterpenoids suggest that the mire flora was dominated by gymnosperms although locally angiosperms may also have been abundant as indicated by the occurrence of tetra and pentacyclic aromatic hydrocarbons at bache peninsula the mire was less forested as indicated by palynological assemblages typical for a marsh environment and petrographic characteristics such as low tissue preservation and the abundance of detrial macerals

evidence for multiple high t metamorphism and regional migmatization within the cadomian belt of northern brittany france the cadomian orogeny is characterized by two major tec tonometamorphic events one that pre dates 570 ma and another at c 540 ma until recently the majority of migmatites occurring within the cadomian belt of northern brittany were interpreted as having been formed during the second event the discovery of the jouguet migmatites which have been hornfelsed by the st brieuc diorite emplaced at 533 l2 ma suggests that a migmatitic event occurred before 540 ma these data demand a reinterpretation of the structural sketch of the cadomian orogeny

relationship between rank and composition of aromatic hydrocarbons for coals of different origins distributions of di and tricyclic aromatics were determined for upper carboniferous to oligocene coals of various origins in addition to upper carboniferous ruhr coals wealden lower creataceous coals from north west germany lower cretaceous coals from western canada and tertiary coals from japan and colombia were studied the coals ranged from sub bituminous to anthracite in rank and showed vitrinite reflectance from 0 4 to 4 9 rm the previously established relationship between the rank of coal in terms of vitrinite reflectance and the distribution patterns of individual aromatic hydrocarbon isomers has been verified and refined it is demonstrated how the above relationships can be used to calculate vitrinite reflectance from the methylphenanthrene index mpi 1 the chemical rank levels of coals can now be defined in terms of the calculated vitrinite reflectance rc

isotopic data upb rbsr pbpb and smnd on mafic granulites from finnish lapland abstract a combined approach using several methods pb pb u pb rb sr sm nd on granulitic rocks selected from classic areas in northern finland is presented the results show that the emplacement of igneous rocks and the granulitic metamorphism occurred nearly coevally 1 9 2 0 ga this result which is supported by field observations means that these rocks are not ideal for comparing the response of the various parent daughter pairs to the high grade metamorphism or for checking the special geochronological possibilities of each method nevertheless because of the coherence of results from rocks of different origins a discussion is possible the bulk of the mafic granulite was certainly derived from upper mantle sources or short lived crustal mafic materials granulites of the granulitic belt and anorthosites are thought to have originated from two distinct mantle sources reflecting mantle heterogeneities at that time

behaviour of rb sr whole rock and u pb zircon systems during partial melting as shown in migmatitic gneisses from the st malo massif ne brittany france the age of regional metamorphism and partial melting in the late proterozoic succession of the st malo area has been established at around 540 ma whole rock homogenization of the sr isotope systems has been achieved only in the anatectic granites whereas the associated metatexitic and diatexitic gneisses remain highly heterogeneous at lower grade than the sillimanite isograd metasedimentary gneisses contain detrital zircons which record the regional metamorphic event as a u pb lower intercept age 536 14 ma in the sillimanite zone u pb zircon lower intercept ages are around 500 10 ma and suggest a recent loss of radiogenic pb from the observed overgrowths zircons from the anatectic granites do not yield u pb intercept ages due to the presence of inherited radiogenic pb but the finer fractions define a discordant array whose upper intercept on concordia yields 555 13 ma an age significantly older than the partial melting event indicated by the lower grade zircon ages the lower intercept defined by the fine grained anatectic zircons yields a date in the future negative ordinate value in their regional context the st malo migmatites can be considered as resulting from late stage crustal melting in the cadomian orogenic belt following genesis of calc alkaline magma at an active margin around 600 ma ago an age of 540 ma for partial melting in the st malo migmatites places the end of the cadomian orogeny near the precambrian cambrian boundary

precadomian relicts in the armorican massif their age and role in the evolution of the western and central european cadomian hercynian belt abstract well dated precambrian is mostly developed in the north of the armorican massif in which area voluminous cadomian magmatism is dated at between 650 and 550 ma much older relicts occur at cap de la hague in guernsey and in the tregor and are also found in the northern continental margin of the iberian peninsula in all these occurrences whole rock systems have been opened so that the true ages cannot be determined by the rb sr whole rock isochron method four u pb zircon ages are between 1 8 and 2 ga in guernsey icart orthogneisses in tregor port beni trebeurden morguignen orthogneisses there is no evidence from strontium isotopes that these isolated and scattered relicts have a wide extension or that such ancient continental crust played an important role in magma genesis from 650 ma to 270 ma ago on the contrary the evolution of initial 87sr 86sr ratios with time shows that the observed mid and west european continental crust is probably not older than 700 ma the increase of the initial 87sr 86sr ratios of the magmas with time suggests that after its formation in cadomian times this segment of continental crust evolved virtually as a closed system and hercynian magmatism arose principally from re melting of relatively young sialic components

u pb investigations on zircons from pre variscan gneisses i a study from the schwarzwald west germany abstract field observations in the schwarzwald indicate that pre variscan rocks were formed by the following events 1 1 intrusion of granitic to granodioritic magma into sediments 2 2 a sequence of two anatectic events with an intervening regional metamorphism and development of a gneissic schistosity the absolute chronology of these older gneisses and migmatites has not yet been satisfactorily resolved we collected several samples of a coarse grained homogeneous orthogneiss of granodioritic composition and one sample of a metasedimentary source rock related to this orthogneiss body in the einetwald forest north of steinach kinzig valley the metasedimentary rock corresponds to the biotitepoor paragneisses in the schwarzwald the zircons in the latter sample are detrital and only very small specimens 45 m are euhedral the zircons from the orthogneiss samples are euhedral some are zoned and some have dark inclusions analyses of the three coarser fractions of the paragneiss form a linear array on a concordia diagram with upper and lower intercepts of about 2000 myr and 524 20 myr respectively the 2000 myr value is interpreted as the average age of the sedimentary source rocks for this material the 524 myr intercept defines an event responsible for most of the lead loss in the zircons as well as new zircon growth analyses of the zircons from the orthogneiss samples do not show a linear array on the concordia diagram because of inclusions of older inherited zircons stepwise leaching of two zircon fractions shows newly grown u rich zircon rims around old cores a 207 pb 206 pb age of 517 15 myr was found for the first dissolution steps about 50 of the zircons dissolved in subsequent steps with progressive dissolution of the residue 207 pb 206 pb age increased to 950 myr the u pb zircon data for the paragneiss and the orthogneiss establish an age of 520 15 myr for the magma intrusion

the distribution of 3 0 ga and 2 7 ga volcanic episodes in the yilgarn craton of western australia abstract the results of a conventional zircon u pb investigation of the ages of felsic volcanic rocks in a number of greenstone belts in the yilgarn craton of western australia indicate that volcanism took place during two distinct episodes at ca 3 0 and ca 2 7 ga each episode spans a time period of about 75 ma and the two ages of volcanism are spatially separated 3 0 ga volcanic rocks are found in greenstone belts in the northern part of the western gneiss terrain and in the murchison province whereas 2 7 ga volcanic rocks are present in the southern part of the western gneiss terrain and in the southern cross and eastern goldfields provinces there is no evidence of inheritance in the zircon u pb systems which would support an older crustal origin for these rocks present results together with previous studies of the ages of granites and gneisses suggest that the volcanic episodes were accompanied by broadly contemporaneous granite plutonism it is suggested that the evolution of the yilgarn craton took place in three main stages the first was the development of a stable 3 4 ga granitic nucleus which incorporated earlier generations of granitoid a 3 7 ga layered complex and possibly 4 2 ga primitive crust this was followed by the two separate granite greenstone episodes at ca 3 0 and ca 2 7 ga involving the addition of significant amounts of new crust each episode was characterised by the accretion of extensive granite greenstone terranes at the margins of the stable craton the intrusion of granite plutons into the evolving craton and the reworking of older cratonic rocks to form granites and gneisses with inherited isotopic systems

alkane and pah biomarkers as tracers of terrigenous organic carbon in arctic ocean sediments abstract we present the first sedimentary biomarker study encompassing the entire arctic ocean a large data set of organic markers for terrigenous petroleum and combustion inputs alkanes hopanes and steranes parent and alkyl polycyclic aromatic hydrocarbons pahs is examined for patterns in space and time using principal components analysis pca and partial least squares pls biomarker patterns reveal the central arctic ocean basin sediments to be compositionally distinct from those of the mackenzie river beaufort sea and barents sea but similar to those of the laptev sea pah distributions reflected in pah ratios and pca projections demonstrate that arctic ocean sediment is dominated by natural inputs to the extent that anthropogenic combustion pahs are not significant we find only modest changes between the glacial and post glacial sediments for atmospherically transported hydrocarbon biomarkers while particle associated biomarkers were captured strongly at basin edges during the glacial period and much more evenly transported across basins during the post glacial period the orders of magnitude decreases in particle associated petrogenic alkanes and pahs in central basins during glacial times coupled with the uniformity of most petrogenic biomarker parameters for most basin and shelf locations reflect a massive reduction in ice transport that makes the margins the most likely source of petrogenic material for the pleistocene holocene central arctic basins the proximity of large coal deposits of various maturity levels along the lena river the overlap in pah and biomarker composition of the laptev sea and surficial sediments from the central arctic ocean and the location of the laptev sea at the origin of the main transpolar drift all point to eroded coals from the lena river laptev sea as the likely source of petrogenic hydrocarbons to the central arctic ocean the ubiquitous presence of allochthonous coal in arctic ocean surface sediments provides a major constraint on the use of petrogenic biomarkers to infer the presence of subsurface petroleum reserves

late precambrian thrust and wrench zones in northern brittany france abstract brioverian units of northern brittany armorican massif france were deformed and metamorphosed during a late precambrian tectonic episode the cadomian orogeny kinematic study strain and displacement in the st cast st brieuc area shows that this tectonic episode was characterized by the obduction of a back arc basin over a continental margin around 580 590 ma ago strain pattern analysis reveals a constant interaction between ssw directed imbricated thrust zones and ductile sinistral wrench zones trending n 50 e the arcuate pattern of cadomian structures in this area results from such an interaction thickening as a result of the thrusts induced migmatization and the development of a high temperature belt around 540 ma in the st malo guingamp area

petrology of a magma chamber the plutonic complex of guernsey channel islands uk the northern plutonic complex of guernsey is a calc alkaline intrusion emplaced within a metamorphic complex composed mainly of the icart gneiss and the perelle gneiss the northern plutonic complex is made up of four distinct bodies the st peter port gabbro the bordeaux diorite group the l ancresse granodiorite and the cobo granite which are roughly contemporaneous emplaced at the end of the cadomian orogeny at around 550 560 ma the st peter port gabbro and the bordeaux diorite group are relicts of a magma chamber characterized by layered rocks along the margins and heterogeneous rock associations in the core of the chamber resulting from stirring by convection oxygen isotopic data are consistent with melting of the country rock possibly the perelle gneiss in response to the intrusion of the gabbro diorite magma chamber the resulting acidic melts mixed with crystallizing gabbro diorite magma to yield the cobo granite and the l ancresse granodiorite this mechanism of acid magma genesis can probably be extended to other late cadomian magmatic events in the northern armorican massif suggesting that basic plutonism in this area may be more important than previously considered

diterpanes triterpanes steranes and aromatic hydrocarbons in natural bitumens and pyrolysates from different mimic coals abstract there is a significant difference in the distribution of terpanes in natural bitumen extracted from four coals identified as rocky mountain coal rmc australian gippsland latrobe eocene coal gec australian gippsland latrobe cretaceous coal gcc and texas wilcox lignite wl whereas pentacyclic triterpanes are dominant in gec gcc and wl diterpanes strongly predominate in the bitumen of rmc this indicates that resin is a more important constituent of rmc than in the other coals and releases the diterpenoids at an early stage of diagenesis furthermore the composition of diterpanes is also different among these coals for example tricyclic diterpanes are the only diterpanes present in rmc whereas tetracyclic and tricyclic diterpanes are both present in gec and gcc and tetracyclic diterpanes are most abundant in gec however diterpanes are nearly absent in wl surprisingly the diterpenoid content is negligible in the pyrolysates of all coals the sterane and triterpane distributions in the natural bitumen of coals are very different from those in pyrolysates c 31 22r hopane predominates in the m z 191 mass fragmentograms of the natural bitumens whereas a homologous series of hopanes c 27 c 35 except c 28 is present in the coal pyrolysates c 29 steranes dominate in all of the coal bitumens as well as pyrolysates c 27 steranes are absent in the natural bitumen but are generated in pyrolysates during lengthy heating of coal kerogen this indicates that formation of secondary steranes occurs by cracking the side chain c 29 monoaromatic steroid hydrocarbons are abundant in the natural bitumen of the four coals the m z 253 distribution is similar for gec rmc and wl but it differs from the more mature ggc which has a lower content of 20r of both 5 and 5 c 29 ma steroids triaromatic steroid hydrocarbons are only present in gcc whereas significant amounts of tetra and triaromatic triterpenoid hydrocarbons are present in the other three coals gec rmc and wl the ratio of benzo e pyrene perylene may be potentially useful as a maturity parameter because the amount of benzo e pyrene increases with thermal stress whereas perylene decreases with heating time benzohopanes are widely present in four humic coals but become unstable after 10 h heating at 300 c

variations of concentration and composition of polycyclic aromatic hydrocarbons in coals in response to dike intrusion in the huainan coalfield in eastern china abstract although extensive studies have been conducted on coals influenced by igneous intrusion the changes of concentration and composition of polycyclic aromatic hydrocarbons pahs in coals responding to this kind of geological rapid heating are largely unknown in the present study thirteen coal samples including unaltered coal thermally altered coal and a dike coal contact sample were collected along a transect approaching an igneous dike intrusion from the no 3 coal seam of the zhuji coal mine in huainan coalfield china these samples represent a broad range of coal ranks ranging from high volatile a bituminous to anthracite vitrinite reflectance ro profiles indicate a progressive increase in ro value from ambient levels of 0 87 1 02 to 5 16 and include an alteration occurring out to 3 6 m from the dike bulk chemical composition from proximate and ultimate analyses shows the typical trend with distance from the dike the total amount of extractable pahs pah35 us epa priority pollutant pahs pah16 and carcinogenic pahs pah8 range from 3 4 81 1 g g 2 5 28 7 g g and 0 7 16 9 g g respectively pah concentrations vary regularly with coal rank reaching a maximum in low volatile bituminous coal 1 62 ro located 3 5 m from the dike this rank is higher than reported for coals not affected by contact metamorphism contact metamorphism has a dramatic effect on the coalification process and results in a different relationship between the pah maximum concentration and coal rank the igneous dike intrusion also has a significant effect on pah distributions where the proportions of 4 6 ring pahs decrease toward the coal dike contact and pahs are dominated by those with 2 and 3 rings the thermally altered coals show a decrease in alkylation compared with that of the unaltered coals and the dealkylation process is apparently accompanied by the cross linking reaction of pahs to form a more compact structure of organic macromolecule

metamorphic zircons from north cameroon implications for the pan african evolution of central africa morphoscopic studies of zircons including optical microscopic and sem backscattered electron mode from the roniers valley west poli northern cameroon indicate an important crystallization of zircon during a medium grade garnet kyanite metamorphic event this was associated with a deformation d1 and with the emplacement of a basic and intermediate plutonic suite bip u pb dating of these zircon gave almost concordant pan african ages 630 ma which contribute to a solution of a major regional uncertainty about the age of the regional d1 event which in the mobile belt of central africa has been considered previously either as pan african or as lower to middle proterozoic a chronological framework is proposed for the evolution of northern cameroon

polycyclic aromatic hydrocarbons pahs in late eocene to early pleistocene mudstones of the sylhet succession ne bengal basin bangladesh implications for source and paleoclimate conditions during himalayan uplift abstract distribution and possible sources of polycyclic aromatic hydrocarbons pahs have been investigated in 23 late eocene to early pleistocene mudstones from the sylhet succession of the northeastern bengal basin bangladesh paleoclimatic conditions in the southern himalaya region throughout the himalayan uplift were reconstructed based on combustion derived pahs and aromatic land plant derived biomarkers phenanthrene fluoranthene fla pyrene py benz a anthracene baan chrysene triphenylene chry tpn benzofluoranthenes bflas benzo e pyrene bepy benzo a pyrene bapy perylene pery indeno 1 2 3 cd pyrene inpy benzo ghi perylene bghip coronene cor and retene ret were the identified pahs fla fla py ratios 0 5 and inpy inpy bghip 0 2 from almost all sylhet samples suggest occurrence of natural wildfires low contents of baan and bapy indicate decomposition by long exposure to sunlight before sedimentation or early diagenetic weathering increased cor inpy and bghip contents suggest occurrence of larger high temperature wildfires correlation coefficients of the pahs and p values for statistical hypothesis testing showed that the positive and negative correlations within the pahs may be indicative of high or low temperatures in wildfires fungi derived pery showed negative correlations with py r 0 67 p 4 6 10 4 and fla r 0 56 p 5 0 10 3 but not with cor bflas inpy and bghip based on the correlation coefficients for all pahs and their p values five statistical groups py fla cor bflas inpy bghip baan chry tpn bapy pery and ret were recognized these groups are probably correlated with origins and depositional processes according to the results the sylhet succession was deposited in three differing paleoclimatic regimes 1 first phase late eocene to early miocene early to middle stage of himalayan uplift high contents of combustion derived pahs fla py and bepy significant gymnosperm derived ret and low pery abundances in the jaintia and barail groups indicate arid climatic conditions although wildfires could often occur 5 or 6 ring combustion pahs cor inpy and bghip contents are low suggesting that the wildfires were relatively low temperature 2 second phase middle to late miocene middle to late stage of himalayan uplift combustion derived pahs and fungi derived pery were dominant in the surma group the climate was arid to humid and seasonal with a dry season giving conditions suitable for combustion abundant fla bflas bepy cor inpy and bghip imply high temperatures in large wildfires however frequency of the wildfires decreased because of wet climate 3 third phase late miocene to pleistocene late stage of himalayan uplift moderate to high pery contents and low fla py and bepy abundances in the tipam and dupitila groups indicate establishment of more humid climate inpy bghip cor bflas and bapy were predominant intensified humid and seasonal climate arising from the himalayan monsoon decreased the incidence and frequency of general wildfires but increased the ratio of large to small wildfires

application of aromatic compounds as maturity indicators in source rocks and crude oils concentration ratios of aromatic compounds such as naphthalenes phenanthrenes and dibenzothiophenes are at present attracting increasing attention as maturity indicators in sedimentary rocks and crude oils generally these indicators rely either on an increase with maturity in the degree of alkylation of a given parent compound or a shift in the isomer distribution of alkyl aromatic homologues towards thermally more stable isomers a combination of both concepts in the methylphenanthrene index mpi resulted in an excellent maturity parameter as demonstrated for rock extracts by an improved correlation with mean vitrinite reflectance rm between 0 65 and 1 4 i e in the zone of oil formation in cases that rm measurements were ambiguous this empirical relationship has proved useful in the calculation of theoretical vitrinite reflectance rc values from the mpi on the other hand for potential petroleum source rocks reaching maturity at relatively low temperatures the influence of the organic matter type on the aromatic distributions cannot be neglected consequently organic facies effects should be taken into account in the interpretation of aromatic distributions of such source rocks and related crude oils since the impact of the organic facies is strongly reduced with increasing maturity aromatic maturity parameters are particularly useful in the maturity evaluation of post mature crude oils and condensates in contrast to biological markers substantially higher concentrations of the key alkyl aromatics persist at elevated maturation levels thus aromatic maturity parameters should be considered as versatile tools in organic maturation studies and can complement established maturity indicators based on steranes and terpanes

timing of post tectonic cadomian magmatism on guernsey channel islands evidence from 40ar 39ar mineral ages the channel island of guernsey exposes pre and post tectonic calc alkaline plutonic rocks attributed to late precambrian cadomian subduction activity 40 ar 39 ar mineral cooling ages presented here clarify the age and time span of post tectonic intrusions amphibole from the bon repos meladiorite yields an isotope correlation age of 605 3 4 6 ma indicating emplacement during late stages of the tectonothermal event recorded within its host rocks igneous hornblendes from the northern igneous complex record consistent isotope correlation ages st peter port gabbro 570 2 1 1 ma bordeaux diorite complex 569 0 1 1 and 565 3 2 2 ma and a comagmatic enclave within cobo granite 570 2 1 5 ma hornblende and biotite from contact metamorphosed host rocks adjacent to the cobo granite yield isotope correlation ages of 569 6 1 1 and 563 8 3 3 ma respectively these ages together with field data demonstrate that the various members of the northern igneous complex were emplaced contemporaneously at c 570 ma significantly earlier than a c 500 ma rb sr whole rock isochron age previously reported for the cobo granite the 40 ar 39 ar ages indicate that post tectonic magmatism on guernsey was broadly coeval with post metamorphic cooling around the baie de st brieuc on the adjacent french mainland and occurred c 30 ma prior to peak cadomian deformation and metamorphism in the st malo area

coal related sources of organic contamination in sediments and water from the bierawka river poland abstract river sediments mixed with coaly material occur all along the length of the bierawka river poland to identify the origin of the coal in the sediment the coaly material was investigated by reflected light microscopy and rock eval pyrolysis and solvent extracts by gas chromatography mass spectrometry gc ms organic compounds dissolved in water were separated by solid phase extraction spe and analyzed by gc ms the results point to a kerogen iii source petrographic analyses confirm abundant coal charred and coked particles in the sediments vitrinite reflectance varied between 0 66 0 80 r r without any large spatial variation the coaly particles have different sources generally the primary origin of coal particles is from coal processing and the dumping the ash with unburned coal particles from a glass factory near the river source later this material was redeposited along the entire river course in addition hard coal processing crushing washing features are visible in larger coal pieces a second source of coaly organic matter is a coal waste dump at szczyglowice where intensive erosion of steep slopes has delivered copious amounts of organic matter into the river the mixing of this organic matter with that from the glass factory is clearly identified on a ternary diagram pah distributions also show differences between sections the coal particle input from the waste dump increased the relative content of naphthalene relative content downstream as in the coal waste 4 5 ring pahs predominate in the sediments the pyrogenic origin of pahs and aromatic compounds such as methylbiphenyls and dibenzofurane in the sediment is indicated by diagnostic pah ratios burned particles were identified petrographically the river water contains only 2 3 ring pahs possibly of industrial origin or leached from coal particles in the river sediments

isotopic equilibration during partial melting an experimental test of the behaviour of sr abstract experiments using isotopically enriched sr doped minerals designed to test for isotopic equilibrium between source and melt during partial melting reveal that 87 sr 86 sr ratios of the liquids are primarily determined by the proportions of minerals consumed and vary with the advancement of the melting reaction the experiments were performed at 1 atm on model crustal assemblages composed of pairs of natural plagioclase an 68 87 sr 86 sr 0 701 and synthetic fluorphlogopite doped with 90 ppm sr having 87 sr 86 sr 4 2 sims traverses showed that during the initial stages of the reaction liquids are isotopically zoned all the analyzed melts have 87 sr 86 sr markedly higher than that of the bulk starting assemblage i e the source because of the faster melting rate of fluorphlogopite at 1200 c and 1250 c melting occurs above a critical temperature wherein the dissolution rates of the crystals are controlled by diffusion of species in the melt and reactants and reaction products are out of isotopic equilibrium this is due to faster melt crystal boundary migration when compared to sr diffusion in the crystals equilibration is possible only if melting stops calculations show that total equilibration between melt and residue by sr tracer diffusion in the crystals takes 10 4 10 6 yr for temperature and grain size ranging respectively from 800 c to 1000 c and 0 1 to 1 cm when compared to the proposed residence time of crustal magmas at their sources this result strongly suggests that magmas that do not reflect the bulk isotopic characteristics of their source regions can be produced

geochemical characteristics of crustal anatexis during the formation of migmatite at the southern sierra nevada california we provide data on the geochemical and isotopic consequences of nonmodal partial melting of a thick jurassic pelite unit at mid crustal levels that produced a migmatite complex in conjunction with the intrusion of part of the southern sierra nevada batholith at ca 100 ma field relations suggest that this pelitic migmatite formed and then abruptly solidified prior to substantial mobilization and escape of its melt products hence this area yields insights into potential mid crustal level contributions of crustal components into cordilleran type batholiths major and trace element analyses in addition to field and petrographic data demonstrate that leucosomes are products of partial melting of the pelitic protolith host compared with the metapelites leucosomes have higher sr and lower sm concentrations and lower rb sr ratios the initial 87sr 86sr ratios of leucosomes range from 0 7124 to 0 7247 similar to those of the metapelite protoliths 0 7125 0 7221 however the leucosomes have a much wider range of initial end values which range from 6 0 to 11 0 as compared to 8 7 to 11 3 for the metapelites sr and nd isotopic compositions of the leucosomes migmatites and metapelites suggest disequilibrium partial melting of the metapelite protolith based on their sr nd and other trace element characteristics two groups of leucosomes have been identified group a leucosomes have relatively high rb pb ba and k2o contents rb sr ratios 0 15 rb sr 1 0 and initial end values group b leucosomes have relatively low rb pb ba and k2o contents rb sr ratios 0 15 and initial end values the low rb concentrations and rb sr ratios of the group b leucosomes together suggest that partial melting was dominated by water saturated or h2o fluxed melting of quartz feldspar assemblage with minor involvement of muscovite breakdown of quartz and plagioclase with minor contributions from muscovite resulted in low rb sr ratios characterizing both group a and group b leucosomes in contrast group a leucosomes have greater contributions from k feldspar which is suggested by 1 their relatively high k concentrations 2 positive or slightly negative eu anomalies and 3 correlation of their pb and ba concentrations with k2o contents it is also shown that accessory minerals have played a critical role in regulating the partitioning of key trace elements such as sm nd nb and v between melt products and residues during migmatization the various degrees of parent daughter fractionations in the rb sr and sm nd isotopic systems as a consequence of nonmodal crustal anatexis would render melt products with distinct isotopic signatures which could profoundly influence the products of subsequent mixing events this is not only important for geochemical patterns of intracrustal differentiation but also a potentially important process in generating crustal scale as well as individual pluton scale isotopic heterogeneities

comparative geochronology in the reversely zoned plutons of the bottle lake complex maine u pb on zircons and rb sr on whole rocks the bottle lake complex is a composite granitic batholith emplaced into cambrian to lower devonian metasedimentary rocks both plutons whitney cove and passadumkeag river are very coarse grained hornblende and biotite bearing granites showing petrographic and geochemical reverse zonation two linear whole rock rb sr isochrons on xenolith free whitney cove and passadumkeag river samples indicate ages of 379 5 m y and 381 4 m y respectively in close agreement with published k ar ages for biotite from whitney cove of 377 m y and 379 m y and for hornblende 40ar 39ar determinations from passadumkeag river which indicate an age of 378 4 m y the initial sr isotopic ratio for whitney cove is 0 70553 and for passadumkeag river is 0 70414 a whole rock isochron on a suite of xenoliths from the passadumkeag river granite indicates a whole rock rb sr age of 496 14 m y with an initial sr isotopic ratio of 0 70262 two types of zircon exhibiting wide petrographic diversity are evident in variable proportions throughout the batholith one of these types is preferentially found in a mafic xenolith and it is widely dispersed in the host granites forming discrete grains and probably as inclusions in the other type of zircon u pb analyses of zircons give concordia intercept ages of 399 8 m y for whitney cove 388 6 m y for passadumkeag river 415 m y for a mafic xenolith in passadumkeag river and 396 32 for combined whitney cove and passadumkeag river granite the zircons show a spread of up to 20 m y in the 207pb 206pb ages omitting the finest zircon fraction in the passadumkeag river results in a concordia intercept age of 381 3 m y in better agreement with the whole rock rb sr and mineral k ar ages for the whitney cove pluton exclusion of the finest fraction does not bring the zircon age into agreement with the rb sr data age estimates by the whole rock rb sr mineral k ar and ar ar methods suggest that the crystallization age of the plutons is about 380 m y slightly younger than the u pb zircon intercept ages a possible reason for this discrepancy is that the zircons contain inherited lead thus zircon u pb ages might represent a mixture of newly developed zircon and older inherited zircon whereas the rb sr whole rock age 380 m y reflects the time of crystallization and the argon ages result from rapid cooling after emplacement

a new model for the hercynian orogen of gondwanan france and iberia abstract the hercynian orogen of gondwanan france and iberia is a collage of disparate terranes separated by faults plate reconstructions indicate that the orogen developed during a massive dextral transpression as laurentia slid along the boundary of gondwana and as laurentia baltica and east avalonia rotated clockwise to form pangea it is proposed therefore that the collage is the result of this transpression and that it is an amalgamation of displaced tectonostratigraphic terranes which represent the dismembering of the gondwanan shelf with its stable platform ordovician devonian sedimentary sequence and the neighbouring rheic ocean specifically it is proposed that 1 the slice of the gondwanan shelf that now forms north brittany was displaced dextrally from nw africa around iberia by more than 2000 km 2 the ophiolites oceanic material and volcanic arcs of south armorica and the massif central represent slices of the rheic ocean displaced dextrally along the gondwana margin and shuffled in amongst slices of gondwanan shelf 3 the convergent component of the transpression is represented by thrusts throughout the region the leon terrane of france and ophiolite bearing klippe in nw iberia the ibero armorican arc was formed by wrapping the mobile dextral shear belts about a rigid iberian basement block the dextral porto tomar shear zone represents the more important shearing in iberia and the iberian sinistral shears are interpreted as bookshelf type structures subsidiary to the dextral shearing

geochemical and isotopic disequilibrium in crustal melting an insight from the anatectic granitoids from toledo spain in the hercynian anatectic complex of toledo act the anatectic granitoids include leucogranitic leucosomes leucogranitic massifs and restite rich granites they show a broad range of initial sr and nd isotope ratios from 0 711 to 0 720 and 0 51164 to 0 51203 respectively which clearly indicate the absence of isotopic homogenization in the melts broadly the ranges reflect the isotopic variation of the metapelitic protoliths if crustal melting occurs under water undersaturated conditions as is the case of the act the generated melts do not isotopically and chemically equilibrate with the granulitic residuum the preservation of heterogeneities could arise through a number of processes 1 duration of the process in which the presence of melts with disequilibrium features and the high solid content of several of the granites in the act point to a very short lived magmatic system 2 limited diffusion in which poorly segregated and volatile undersaturated granitoids have a very restricted opportunity for isotopic and chemical homogenization and 3 magma dynamics in which the low melting rates the high restite and low water contents and the silica rich composition of these granites together with the small volume and high viscosity values of the melts seriously restrict the physical processes leading to homogenization

neoproterozoic shear zone tectonics within the icartian basement of guernsey and sark channel islands the channel islands of guernsey and sark are amongst the few localities within the neoproterozoic cadomian orogenic belt where palaeoproterozoic basement is exposed basement units collectively referred to as icartian comprise orthogneisses e g the c 2000 ma icart granite gneiss metasediments and amphibolites on guernsey the protolith to the icart granite gneiss was intruded into metasediments already deformed during a d 1 deformation event both were variably deformed during a d 2 event within an approximately north south trending steeply dipping oblique dextral shear zone on sark metasediments and amphibolites carry a d 1 fabric not necessarily correlatable with that on guernsey which was deformed during d 2 to form recumbent gently inclined folds and tectonic fabrics which locally carry top to the south kinematic indicators early cadomian quartz diorites which intruded the icartian basement carry variably developed magmatic and moderate temperature 400 550 c ls solid state fabrics which are similarly oriented to d 2 basement structures this indicates that the quartz diorites were emplaced and deformed during a protracted d 2 event published 40 ar 39 ar amphibole cooling ages of c 600 ma from guernsey and sark quartz diorites and a host icartian amphibolite are consistent with reworking of basement units during the cadomian orogeny the contrasting kinematic pattern during cadomian deformation implies that a flat lying shear zone on sark may have accommodated oblique dextral strike slip movement on guernsey with an overall southerly direction of tectonic transport deformation most likely occurred in the hanging wall of a major south dipping neoproterozoic subduction zone

schlieren formation in diatexite migmatite examples from the st malo migmatite terrane france schlieren are trains of platy or blocky minerals typically the ferromagnesian minerals and accessory phases that occur in granites and melt rich migmatites such as diatexites they have been considered as 1 unmelted residue from xenoliths or the source region 2 mineral accumulations formed during magma flow 3 compositional layering and 4 sites of melt loss in order to help identify schlieren forming processes in the diatexites at st malo differences in the size shape orientation distribution and composition of the biotite from schlieren and from their hosts have been investigated small biotite grains are much less abundant in the schlieren than in their hosts schlieren biotite grains are generally larger have greater aspect ratios and have except in hosts with low 10 biotite contents a much stronger shape preferred orientation than host biotite the compositional ranges of host and schlieren biotite are similar but schlieren biotite defines tighter sharper peaks on composition frequency plots hosts show magmatic textures such as imbricated tiled unstrained plagioclase some schlieren show only magmatic textures tiled biotite no crystal plastic strain features but many have textures indicating submagmatic and subsolidus deformation e g kinked grains and these schlieren show the most extensive evidence for recrystallization magmas at st malo initially contained a significant fraction of residual biotite and plagioclase crystals smaller biotite grains were separated from the larger plagioclase crystals during magma flow since plagioclase was also the major early crystallizing phase the plagioclase rich domains developed rapidly and reached the rigid percolation threshold first forcing further magma flow to be concentrated into narrowing melt rich zones where the biotite had accumulated hence increasing shear strain and the degree of shape preferred orientation in these domains schlieren formed in these domains as a result of grain contacts and tiling in the grain inertia regime final amalgamation of the biotite aggregates into schlieren involved volume loss as melt trapped between grains was expelled after the rigid percolation threshold was reached in the biotite rich layers

alkane and pah provenance and potential bioavailability in coastal marine sediments subject to a gradient of anthropogenic sources in british columbia canada abstract marine coastal areas of british columbia canada are subject to a gradient of increasing anthropogenic sources from pristine areas in the north to the more urbanised areas of the south along the gradient the relative contributions of polycyclic aromatic hydrocarbons pahs from multiple natural and anthropogenic sources are not well understood but concerns linger about bioavailability and consequent risks to marine biota composition patterns and principal components analysis pca models for surface sediment and core samples collected along this transect indicate that samples from the urbanised vancouver area have the highest proportions of tricyclic terpane hopane and sterane biomarkers ucm unresolved complex mixture the alkyl fluoranthene pyrene and benz a anthracene chrysene series and most parent pahs those from hecate and queen charlotte straits and other locations in the strait of georgia have on the other hand higher proportions of the resolved alkanes and petrogenic alkyl naphthalene fluorene dibenzothiophene and phenanthrene anthracene series pah ratios clearly indicate a predominance of combustion sources for the four ring and higher parent pahs for all the sediments most samples have values close to the biomass solid fuel and liquid fuel combustion borderline for ratios of the major pahs but liquid fuel combustion input dominates closer to urbanised locations ratios also suggest similar pyrogenic and petrogenic inputs between central hecate strait and reference sediments from hecate strait through to queen charlotte strait which indicates that biomass combustion and immature coal formations are the major putative respective sources for the reference areas alkyl pah ratios for the c3 and c4 naphthalenes c2 and c3 phenanthrenes and 3 and 2 methylchrysene reflecting terrigenous vascular plant sources and petroleum maturity exhibit marked differences between comox bituminous coal and alberta sweet mixed blend asmb oil and reveal that the petrogenic input in all of the sediments is non biodegraded ratios of these alkyl pahs with multiple substituents indicate that the sediment samples in the northern strait of georgia closest to the comox coal field receive relatively constant input of eroded coal while those in the southern strait of georgia and vancouver harbour show a composition closest to asmb oil pahs associated with liquid fossil fuel combustion and petroleum discharges adjacent to urbanised areas are expected to be fully bioavailable to marine food webs while the char from biomass combustion and coal from immature deposits in more remote areas would have limited bioavailability this implies that biota in remote areas of hecate strait queen charlotte sound are likely not adapted to the presence of oil and thus would be more sensitive to exposure to spilled oil than those in the more impacted environments in southern british columbia

helium trapping in apatite damage insights from u th sm he dating of different granitoid lithologies apatite u th sm he ahe thermochronometry is widely used to constrain thermal histories and rates of tectonic exhumation and erosion processes however data interpretation is often challenging especially when the thermal history includes extended residence time in the he partial retention zone heprz with highly dispersed dates revealing the complexity of diffusion processes in natural systems this study investigates chemical and physical factors that may have impacted he diffusion in apatite over long timescales in a context of protracted residence in the heprz nine samples from the ploumanac h pluton and north tregor armorican massif france were collected in granitoids differing in petrography and chemisty this area was chosen because these samples underwent a similar thermal history since 300 ma we report new u th sm he dates along with apatite fission track aft data as well as lithological and chemical characterization the results show dispersed u th sm he dates ranging from 87 7 to 291 23 ma whereas central aft dates vary from 142 6 to 199 9 ma current predictive models for he diffusion and fission track annealing in apatite could not reproduce the two datasets together however this apparent discrepancy gives insight into the parameters influencing he diffusion at geological timescales the data confirm that radiation damage enhances he trapping as the ahe dates are positively correlated to effective uranium eu concentration the he age dispersion for constant eu content cannot be explained just by variations in grain size or chemical composition to explore the potential influence of recoil damage trapping behavior and annealing kinetics on ahe dates we tested a new diffusion model from gerin et al 2017 given the expected model of the thermal history provided by aft inversion we investigated the influence of the trapping energy on ahe dates the ahe date variations can be explained only if the trapping energy evolves from one crystal to another increasing with the amount of damage for a given trapping energy minor variations in the recoil damage annealing rate can consistently explain most of the remaining dispersion of the ahe dates

precise u pb zircon ages from alderney channel islands growing evidence for discrete neoproterozoic magmatic episodes in northern cadomia the northernmost exposures of rocks formed during the late neoproterozoic cadomian orogeny in the channel islands northern france region occur on alderney the island mainly comprises foliated quartz diorite once considered to be 2 ga pre cadomian basement and an undeformed basic to intermediate plutonic complex a precise age of 610 2 ma based on u pb analyses of single and small groups of zircons for the foliated fort tourgis quartz diorite demonstrates that the oldest rocks were emplaced and deformed during a cadomian magmatic event the age is virtually identical to ages from similar foliated syntectonic quartz diorite bodies on the islands of guernsey and sark and at la hague north normandy indicating that this magmatic and deformational event was regional in extent discordant zircon xenocrysts define an upper intercept age of c 2 ga indicating the presence of palaeoproterozoic basement at depth single zircons from the undeformed bibette head granodiorite give a precise u pb age of 572 1 ma this age is closely similar to that for the emplacement of the northern igneous complex of guernsey the emerging data indicate that cadomian magmatism in the northern channel islands region was not a protracted continuum but occurred during two distinct short lived events separated by c 30 40 my

aliphatic and aromatic triterpenoid hydrocarbons in a tertiary angiospermous lignite abstract the hydrocarbon biomarker assemlage of a liptinite rich early tertiary angiospermous lignite has been characterized the biomarker fistribution for the lignite confirms the low maturity and previous paleobotanic interpretations the aliphatic hydrocarbon fraction consists predominantly of n alkanes showing a strong odd carbon predominance and numerous de a triterpenoids and triterpenoids derived from higher plants bacterially derived triterpenoids were represented primarily by homohopanes and hopenes the aromatic hydrocarbon fraction contains a series of mono di and triaromatic de a triterpenoids and mono tri and tetraaromatic triterpenoids derived from higher plants the concentration and abundance of monoaromatic triterpenoids containing one to three additonal degress of unsaturation have not seen previously observed in a single deposit as such a diagenetic scheme for angiosperm derived triterpenoids is presented which confirms and extends previous hypothesis

geochemical and geochronological cross section of the deep variscan crust the cabo ortegal high pressure nappe northwestern spain the high pressure rocks of the cabo ortegal nappe and related massifs are represented by several tectonometamorphic units which underwent separate histories before regional overthrusting and amphibolite facies recrystallization at 380 ma the occurrence of final cooling is recorded by 40ar 39ar and rb sr mica ages of up to 350 ma u pb zircon dating and sm nd and rb sr isotope data together with ree and major and trace element geochemistry provide constraints on the timing of earlier tectonothermal events and the nature of the protoliths the earliest tectonothermal event occurred at 490 480 ma and corresponds to the emplacement of lree enriched magmas of probable calc alkaline affinity and their metamorphism in the granulite facies this occurred at approximately the same time as the eclogite facies metamorphism of morb like protholiths associated with basic to intermediate granulites together this suggests formation of syn accretion granulites in an active margin setting a second high grade metamorphic event is recorded at 420 ma in metasedimentary formations associated with eclogite like assemblages garnet omphacite plagioclase this event is possibly related to a collisional plate tectonic setting in a back arc basin the age and origin of the associated ultrabasic rocks remains unclear but a late pyroxenite vein has yielded an emplacement age of 390 ma

organic geochemistry and petrography of tertiary coals and carbonaceous shales from argentina a series of eight tertiary coal and carbonaceous shale samples with vitrinite reflectance values between 0 50 and 0 58 were extracted fractionated and the saturated and aromatic hydrocarbons analysed for characteristic components by gc and gc ms additionally a microscopical study was undertaken in order to obtain a more precise picture of the samples under investigation the saturated hydrocarbon fractions displayed the typical n alkane distribution for coals of this rank with cpi values between 2 0 and 3 1 among the branched cyclic compounds pristane and homohopane were recognised as relevant components pointing to an oxic depositional environment detection of benzohopanes c32 c35 in the aromatic hydrocarbon fractions suggests that bacteriohopanetetrol was a significant constituent of the coal biomass taking into consideration the pr ph ratios ash contents and microscopical characteristics of the samples aspects of the possible degradation of hopanetetrol to homohopane are discussed resin derived diterpenoids with the phyllocladane and kaurane skeleton were tentatively identified and although minor compounds they are interpreted to be a sign of the contribution of podocarpaceae and araucareaceae to the coal swamp aromatic compounds were dominated by alkylnaphthalene derivatives presumably formed by c ring cleavage and aromatisation of higher plant derived pentacyclic triterpenois which were main components in the high boiling range of the fractions investigated angiosperms especially fagaceae are postulated as source for these polycyclic compounds and hence for some of the polyalkylated aromatic bicyclics detected

the cadomian active margin north armorican massif france a segment of the north atlantic panafrican belt abstract within the european variscan belt the armorican massif northwestern france contains an isolated fragment of the north atlantic panafrican belt the cadomian block mostly unaffected by variscan deformation this block is composed of neoproterozoic rocks ranging in age from 620 to 540 ma brioverian locally overlying a composite basement of icartian 2000 ma or pentevrian 750 ma age the cadomian tectonics the last magmatic manifestations of which are dated at around 540 ma were sealed by a cover of early cambrian rocks in normandy and early ordovician rocks in brittany five units are distinguished in this cadomian block tregor saint brieuc guingamp saint malo and fougeres although the units are bound by major faults the overall coherence of their different protolithic characteristics suggests that they can be fitted into a simple geodynamic model the tregor unit represented by the north tregor batholith of crustal affinity and its icartian host rock probably reflects an early cadomian evolution the saint brieuc unit essentially made up of magmatic rocks of juvenile affinity includes two assemblages juxtaposed by the cadomian tectonics 1 a volcanosedimentary succession formed in a typical island arc setting reflecting subduction around 610 ma and 2 a volcanic plutonic complex emplaced around 590 ma in an extensional active continental margin of pentevrian age the guingamp unit predominantly migmatitic includes a tectonic slice of deep origin the extrusion of which accompanied the exhumation of the migmatites it may represent the trace of a possible suture the saint malo unit is composed of brioverian detrital rocks the significance of which is uncertain passive continental margin or accretionary prism it is structured around a late migmatitic dome 540 ma the fougeres unit corresponds to the outer domain of the cadomian orogeny it was only weakly deformed by cadomian tectonics and is intruded by the large mancellian batholith of crustal origin dated at 540 ma together the structural units are interpreted in the framework of an evolving active margin juxtaposing continental margin marginal basin and volcanic arc before being shortened during the cadomian convergent tectonics

petrographical and organic geochemical investigation of the oberpfalz brown coal deposit west germany abstract a detailed macro and micropetrographical investigation coupled with gc and gc ms analysis of the alkane fraction of tertiary brown coal samples from the oberpfalz region of bavaria west germany was undertaken distinctive petrographical and organic geochemical facies differences were evident in the coal seams investigated which came from two neighbouring open cast mines the lower seam was of a limnic nature while the upper seam in the neighbouring mine showed the more typical characteristics of terrestrial depositon both seams were generally characterized by high ash contents and extract yields microlayering and framboidal pyrite the predominance of texto ulminite a combined with relatively high resinite contents suggested that gymnosperms were the main peat forming plants additionally the coal extracts were characterized by the presence of the diterpane phyllocladane which made up to 60 of the alkane fraction in some samples bacterial activity in the coal swamp was marked by the presence of hopanes mainly 17a h 21 h homohopane and biodegradation of the n alkanes

late proterozoic zircon ages from a basic ultrabasic complex a possible cadomian orogenic complex in the hercynian belt of western europe the basic ultrabasic complex of belle isie en terre northwestern part of the armorican massif france has been dated at 602 4 1 m y by the u pb zircon method the calc alkaline trend of the metabasic rocks and the geologic context suggest that this ophiolite like complex is related to a back arc orogenic setting similar to the geodynamic environment that has been proposed for pan african calc alkaline ophiolite like complexes of late proterozoic age around the west african craton our results are compatible with the closing in late proterozoic time of a channel ocean north of the basement and formed during the cadomian orogeny rather than with possible caledonian or hercynian subduction