maturation and bulk chemical properties of a suite of solid hydrocarbons abstract in this paper we present strong correlations of solid hydrocarbon reflectance shro to vitrinite reflectance vro and bulk chemical properties aromaticity tmax h c etc these correlations suggest that like kerogen in coals and sedimentary rocks solid hydrocarbons vary systematically during maturation as a consequence shro is especially useful as a maturity indicator in rocks lacking vitrinite such as pre devonian rocks and many organic rich marine rocks unlike other organic maturationv indicators the utility of solid hydrocarbons is not limited by botanical evolution but rather the generative potential of the petroleum system solid hydrocarbons also known as solid bitumen asphalt dead oil migrabitumen and pyrobitumen are genetically defined as solid phase accumulations of predominantly hydrocarbons produced by petroleum generation in source rocks they may occur over a range of concentrations in outcrop and well samples in all components of petroleum systems although accumulations of solid hydrocarbons from exhumed reservoirs are well reported the extent and utility of disseminated solid hydrocarbons in shales is less understood solid hydrocarbons are found in organic rich to very lean mature rocks as a residual product of generation disseminated solid hydrocarbons exhibit three optical forms anisotropic coked granular and relatively uniform homogenous only the homogenous solid hydrocarbons are recommended for correlation purposes with other thermal indicators

the ktb apatite fission track profiles building on a firm foundation abstract deep boreholes serve as natural laboratories for testing thermochronometers under geological conditions the kontinentale tiefbohrung ktb is an interesting candidate because the geological evidence suggests that approximate isothermal holding since the last documented exhumation in the late cretaceous to palaeocene is a reasonable assumption for the thermal histories of the ktb samples we report 30 new apatite fission track ages and 50 new mean confined track lengths determined on cores from the 4 km deep pilot hole the and external detector ages are consistent with the population ages from earlier studies and together define a clear age profile the mean track lengths from this and earlier studies reveal the effects of experimental factors the measured age and length profiles are compared with the predictions of 24 annealing models for isothermal holding there are clear discrepancies between the measured and calculated profiles down to 1 5 km depth the measured mean track lengths are shorter than the predicted the balance of methodological evidence indicates that this is due to seasoning i e a shortening of the fossil confined tracks without attendant age reduction from 2 5 to 4 0 km depth the mean track lengths are longer than the predictions this suggests that the bias model that weights the probabilities of observing tracks of different length and which is based on experiments relating surface track densities to mean track lengths is not appropriate for confined tracks experimental and methodological factors are sometimes difficult to disentangle but present a sufficient margin for there to be no need to go against the independent geological evidence unknown geological events cannot be ruled out but their existence cannot be inferred from the fission track data alone much less can the nature or magnitude of such events be specified

an empirical determination of the minimum number of measurements needed to estimate the mean random vitrinite reflectance of disseminated organic matter abstract in coal samples published recommendations based on statistical methods suggest 100 measurements are needed to estimate the mean random vitrinite reflectance r v r to within 2 our survey of published thermal maturation studies indicates that those using dispersed organic matter dom mostly have an objective of acquiring 50 reflectance measurements this smaller objective size in dom versus that for coal samples poses a statistical contradiction because the standard deviations of dom reflectance distributions are typically larger indicating a greater sample size is needed to accurately estimate r v r in dom however in studies of thermal maturation using dom even 50 measurements can be an unrealistic requirement given the small amount of vitrinite often found in such samples furthermore there is generally a reduced need for assuring precision like that needed for coal applications therefore a key question in thermal maturation studies using dom is how many measurements of r v r are needed to adequately estimate the mean our empirical approach to this problem is to compute the reflectance distribution statistics mean standard deviation skewness and kurtosis in increments of 10 measurements this study compares these intermediate computations of r v r statistics with a final one computed using all measurements for that sample vitrinite reflectance was measured on mudstone and sandstone samples taken from borehole m 25 in the cerro prieto mexico geothermal system which was selected because the rocks have a wide range of thermal maturation and a comparable humic dom with depth the results of this study suggest that after only 20 30 measurements the mean r v r is generally known to within 5 and always to within 12 of the mean r v r calculated using all of the measured particles thus even in the worst case the precision after measuring only 20 30 particles is in good agreement with the general precision of one decimal place recommended for mean r v r measurements on dom the coefficient of variation v standard deviation mean is proposed as a statistic to indicate the reliability of the mean r v r estimates made at n 20 this preliminary study suggests a v v 0 2 suggests an unreliable mean in such small samples

fluid inclusion and vitrinite reflectance geothermometry compared to heat flow models of maximum paleotemperature next to dikes western onshore gippsland basin australia abstract nine basalt dikes ranging from 6 cm to 40 m thick intruding the upper jurassic lower cretaceous strzelecki group western onshore gippsland basin were used to study maximum temperatures t max reached next to dikes t max was estimated from fluid inclusion and vitrinite reflectance geothermometry and compared to temperatures calculated using heat flow models of contact metamorphism thermal history reconstruction suggests that at the time of dike intrusion the host rock was at a temperature of 100 135 c fracture bound fluid inclusions in the host rocks next to thin dikes t max systematically increases towards the dike margin to at least 500 c the estimated t max next to the thickest dike thickness d 40 m suggests an extended zone of elevated r v r to at least a distance from the dike contact x of 60 m or at x d 1 5 using a normalized distance ratio used for comparing measurements between dikes regardless of their thickness in contrast the pattern seen next to the thin dikes is a relatively narrow zone of elevated r v r heat flow modeling along with whole rock elemental and isotopic data suggests that the extended zone of elevated r v r is caused by a convection cell with local recharge of the hydrothermal fluids the narrow zone of elevated r v r found next to thin dikes is attributed to the rise of the less dense heated fluids at the dike contact causing a flow of cooler groundwater towards the dike and thereby limiting its heating effects the lack of extended heating effects suggests that next to thin dikes an incipient convection system may form in which the heated fluid starts to travel upward along the dike but cooling occurs before a complete convection cell can form close to the dike contact at x d r v r often decreases even though fluid inclusion evidence indicates that t max is still increasing further fluid inclusion evidence indicates that the evolution of water vapor or supercritical fluids in the rock pores corresponds to the zone where r v r begins to decrease the generation of the water vapor or supercritical fluids near the dike contact seems to change vitrinite evolution reactions these metamorphic conditions closer to the dike than x d 0 3 make vitrinite reflectance unreliable as a geothermometer the form of the r v r profile as it indicates t max can be interpreted using temperature profiles estimated from various heat flow models to infer whether the dike cooled by conduction incipient convection or a convection cell a contact aureole that consists of decreasing r v r or t max extending out to x d 2 and that has a t contact t magma t host 2 appears to be a signature of simple conductive cooling incipient convection is indicated by a r v r profile that decreases to background levels at x d r v r profile and consistently high r v r that may not decrease to background levels until beyond distances of x d 1 5

standardization of reflectance measurements in dispersed organic matter results of an exercise to improve interlaboratory agreement vitrinite reflectance generally is considered the most robust thermal maturity parameter available for application to hydrocarbon exploration and petroleum system evaluation however until 2011 there was no standardized methodology available to provide guidelines for vitrinite reflectance measurements in shale efforts to correct this deficiency resulted in publication of astm d7708 standard test method for microscopical determination of the reflectance of vitrinite dispersed in sedimentary rocks i n 2012e2013 an interlaboratory exercise was conducted to establish precision limits for the d7708 measurement

petrographic and reflectance analysis of solvent swelled and solvent extracted south african vitrinite rich and inertinite rich coals maceral transitions during solvent swelling and extraction of two south african coals similar in rank and age but different in maceral composition were evaluated inertinite rich highveld coal dominated by semifusinite and vitrinite rich waterberg coal were used maceral group analysis of solvent extracted and solvent swelled residues showed no changes in the maceral composition for both coals solvent extracted residues exhibited significant observable changes of some particles particle fracturing decrease in reflectance and rounding of particle edges inertinite rich coal exhibited extensive fracturing during solvent treatment random reflectance analyses of both coals showed that solvent treatment reduces reflectance values of both vitrinite and inertinite vitrinite reflectograms showed a shift from the dominant reflecting v types to lower reflecting v types the inertinite reflectograms exhibited an increase in the number of reflecting inertinite types i types with solvent treatment resulting in a broadening of the reflectograms the changes in reflectance between the original and solvent treated coal may be attributed to a combination of structural elemental or surface changes current data for these south african coals suggests a relationship between solvent extraction and mean random reflectance the higher the extraction yields the lower the mean random reflectance

extending a thickened crustal bulge toward a new geodynamic evolution model of the paleozoic nw bohemian massif german continental deep drilling site se germany abstract fault bounded tectonic metamorphic complexes assembling the nw bohemian massif around the german continental deep drilling ktb site are seen to be extremely heterogeneous in tectonic and metamorphic histories in current models the different complexes were supposed to reflect a puzzle of small pre devonian microplates and the related collision events supposedly lasted until the carboniferous opposed to these models it will be shown that all the boundaries among the complexes were formed by detachment late in a prolonged overall geodynamic history of a thickened crustal bulge during extensional tectonics and associated thermal events that outlasted the onset of collision in the silurian lower devonian by about 70 80 ma micro structures petrological and geochronological data of individual complexes predominantly preserve the late stages rather than the unbroken record of their tectonometamorphic histories such partial histories strongly different among individual complexes depict diverse snapshots taken at different places in the evolving thickened crustal bulge and at different instants in its overall evolution and do not define different precollisional microplates predominantly p t and deformation episodes after terrane juxtaposition are preserved this article presents an integrated view of the structural geology microscopic fabrics p t data and geochronology of such diverse metamorphic complexes this integrated view provides a new understanding of 1 the tectonic evolution during upper silurian devonian collision of the gondwana derived central european lithosphere with laurussia 2 the postaccretionary events that lasted through the upper carboniferous and 3 the earlier lower ordovician metamorphic and magmatic history which is only locally recorded metamorphic complexes occupying the structurally highest position upper tectonic complexes record devonian and earlier tectonometamorphic and magmatic events after the mid devonian such complexes did not experience any metamorphism the recorded devonian events consist of subduction and exhumation of hp rocks and their exhumation involved thrusting and extensional tectonics upper tectonic complexes comprise fragments of both the plate that was subducted in this period and the overriding plate in the footwall carboniferous extension has brought upper tectonic complexes against metamorphic complexes that essentially record lower and upper carboniferous tectonometamorphic and magmatic events lower tectonic complexes in the lower tectonic complexes such events are 1 consecutive extensional stages that created at least three sets of ductile normal detachment systems intersecting each other and various associated thermal pulses as well as 2 predetachment events that are only recorded as petrologic and structural relics transposed during extension inferred as predetachment events are crustal subduction as well as stacking that outlasted thrusting and exhumation of the upper tectonic complexes in the deeper portion of the thickened crustal bulge represented by the lower tectonic complexes spatial variations of p t t d histories during decompression occurred as a result of continued differential exhumation on the three sets of detachment systems and also from various thermal pulses that have affected different parts of this section during progressive shearing and exhumation to various degrees whereas the lower tectonic complexes of the erzgebirge gneiss dome preserve the record of a lower carboniferous history of hp metamorphism and crustal thickening followed by extension in those of the oberpfalz region ktb site a major upper carboniferous thermal pulse mostly erased the pre upper carboniferous strain fabrics and metamorphic record in the oberpfalz region ongoing extension emplaced mid crustal rocks that pervasively equilibrated in the upper carboniferous at high temperatures and low pressures low p t ratio against rocks not exposed to high temperatures at that time in summary a prolonged postaccretionary history concealed large scale structural relationships linked to crustal subduction and thickening associated with former juxtaposition of gondwana lithosphere to laurussia polyphase crustal extension and strike slip created the variety of different metamorphic tectonic complexes observed in the nw bohemian massif

thermal tectonic history of the baogutu porphyry cu deposit west junggar as constrained from zircon u pb biotite ar ar and zircon apatite u th he dating abstract understanding postmineralization tectonic movements in porphyry deposits is critical to interpreting the complete thermal tectonic history this study reports new zircon u pb ages hydrothermal biotite 39ar 40ar age and zircon and apatite u th he ages from the baogutu porphyry copper deposit which in conjunction with pre existing geochronology and thermochronology and inverse modeling simulations constrain the thermal tectonic history of the deposit zircon la icp ms u pb concordia ages indicate a late carboniferous age of 320 1 2 2 ma for the diorite complex and 309 8 2 2 ma for the mineralized granodiorite porphyry hydrothermal biotite selected from a quartz biotite chalcopyrite vein yields a plateau age of 311 0 1 8 ma which agrees with the age of the granodiorite porphyry and a previously reported molybdenite re os age and suggests that hydrothermal fluid circulated about 310 m y ago diorite and granodiorite porphyry yield weighted mean zircon u th he ages of 200 6 5 7 ma and 241 1 8 1 ma respectively with ages ranging from 221 0 ma to 174 3 ma and 225 9 to 261 6 ma weighted mean diorite and granodiorite porphyry apatite u th he ages of 87 4 2 3 ma and 120 0 4 2 ma were obtained with ages ranging from 68 9 ma to 100 8 ma and from 91 0 ma to 152 0 ma respectively the wide range of zircon u th he ages may be due to the combined effects of u and th zonation and radiation damage and radiation damage effect may also account for the wide range of apatite u th he ages the combined effects of depth and cooling due to meteoric water circulation contribute to an older u th he age for the granodiorite porphyry relative to the diorite a five episode cooling rate history for the diorite can be deduced by inverse model simulation fast cooling moderate fast cooling relatively slow cooling fast cooling again very slow cooling the thermal and tectonic history of the wall rock indicates that it suffered significant far field effects from the qiangtang eurasia and lhasa qiangtang collision however no visible thermal effect from the india asia collision is observed

the cretaceous and younger thermal history of the ktb site germany apatite fission track data from the vorbohrung a detailed fission track analysis was carried out on 41 apatite samples from the 4001 m deep pilot hole of the german continental deep drilling program ktb the investigations include dating by the population method and length measurements of horizontal confined tracks age and length information indicate that all samples above the present day partial annealing zone cooled from temperatures above 120 c in the cretaceous the top two kilometres of the profile show less variation of age with depth than was expected modelling of the profile indicates that the distribution of fission track ages with depth requires that the profile was disturbed during or after cooling through the partial annealing zone modelling of individual samples reveals that at least the upper 2 km experienced reverse faulting effectively thickening the upper part of the rock column by up to 1000 m in the tertiary a present day partial annealing zone for apatite was observed between 2000 and 4000 m 60 110 c this confirms earlier in situ observations of the position of the partial annealing zone

thermochronological constraints on the long term erosional history of the karkonosze mts central europe abstract a combination of zircon u th he zhe apatite fission track aft and apatite u th sm he ahe thermochronology is used to constrain the long term exhumation and erosional history of the karkonosze mts in north eastern bohemian massif by analyzing samples from the highly elevated summit planation surface zhe ages from the south eastern part of the planation surface are 285 19 295 20 and 308 21 ma indicating that the area remained at temperatures below 190 c since the permian in contrast zhe ages in the western part of the planation surface are mid cretaceous proving that this part was residing at temperatures above 190 c prior to exhumation the exhumation occurred in the late cretaceous as evidenced by aft and ahe ages ranging from 82 5 to 90 8 ma and from 77 5 to 91 6 ma respectively modelled cooling trajectories are characterized by a two stage cooling history fast cooling through the apatite partial annealing zone and helium partial retention zone to surface conditions between 90 and 75 ma and slow cooling or even thermal stagnation from 75 ma to present although our data do not allow us to resolve the age of the planation surface completely we narrowed down the number of explanatory options and propose two alternative solutions for the formation of the planation surface i the planation surface represents the remnant of a permian peneplain which was buried by mesozoic sediments of the central european basin system and was re exposed in the late cretaceous or ii the planation surface formed after 75 ma after termination of a period of massive erosion documented by thermochronological data and by the sedimentary record in adjacent basins cenozoic relief production and uplift of the planation surface evident from regional landforms and the sedimentary record is not recorded by thermochronological data this shows that erosion on the uplifted planation surface since 75 ma was less than 1 2 km

petrography geochemistry and depositional setting of the san pedro and santo tomas coal zones anomalous algae rich coals in the middle part of the claiborne group eocene of webb county texas two coal zones the san pedro and the overlying santo tomas are present for nearly 35 km in outcrop surface and underground mines and shallow drill holes along the strike of the middle part of the claiborne group eocene in webb county texas a sandstone dominated interval of 25 to 35 m separates the two coal zones which range up to 3 m in thickness each coal zone contains carbonaceous shales thin 0 75 m impure coal beds and thin 0 85 m but commercially significant nonbanded coal beds the nonbanded coals are different from other tertiary coals of the gulf of mexico coastal plain unlike lignites that are typical of the older wilcox group paleocene eocene and younger jackson group eocene nonbanded coals of the claiborne group have high vitrinite reflectance values 0 53 rmax and high calorific yields average 6670 kcal kg or 12 000 btu dry basis the coals are weakly agglomerating free swelling index is 1 5 2 0 and have an apparent rank of high volatile bituminous the coal bearing portion of the middle claiborne group in the rio grande area represents a fining upward transition from sandstone dominated marine influenced lower delta plain depositional environments to more inland mudstone rich predominantly freshwater deltaic settings discontinuities within the san pedro coal zone are attributed mainly to the influence of contemporaneous deposition of distributary mouth bar sand bodies the less variable nature of the santo tomas coal zone reflects its origin in the upper part of an interlobe basin that received only minor clastic influx petrographic attributes of the nonbanded coals indicate that they formed subaqueously in fresh to possibly brackish waters a highly degraded groundmass composed of eugelinite is the main petrographic component approximately 71 mineral matter free basis an enriched liptinite fraction approximately 23 probably accounts for unusually high calorific values there is negligible inertinite petrographic study of polished blocks indicates that approximately 10 percent of the nonbanded coal from both coal zones is composed of green algae fructifications which also occur in clastic rocks of the coal bearing interval such algal material cannot be identified or quantified by conventional coal petrographic techniques that utilize particle pellets or by palynological analyses that include acid preparation

constraining long term denudation and faulting history in intraplate regions by multisystem thermochronology an example of the sudetic marginal fault bohemian massif central europe 1 the rychlebske hory mountain region in the sudetes ne bohemian massif provides a natural laboratory for studies of postorogenic landscape evolution this work reveals both the exhumation history of the region and the paleoactivity along the sudetic marginal fault smf using zircon u th he zhe apatite fission track aft and apatite u th he ahe dating of crystalline basement and postorogenic sedimentary samples most significantly and in direct contradiction of traditional paleogeographic reconstructions this work has found evidence of a large cretaceous sea and regional burial to 6 5 km of the carboniferous permian basement in the late cretaceous 95 80 ma during the burial by sediments of the bohemian cretaceous basin system the smf acted as a normal fault as documented by offset zhe ages across the fault at 85 70 ma the basin was inverted cretaceous strata eroded and basement blocks were exhumed to the near surface at a rate of 300 m ma as evidenced by late cretaceous paleocene aft ages and thermal modeling results there is no appreciable difference in aft and ahe ages across the fault suggesting that the smf acted as a reverse fault during exhumation in the late eocene oligocene the basement was locally heated to 70 c by magmatic activity related to opening of the eger rift system neogene or younger thermal activity was not recorded in the thermochronological data confirming that late cenozoic uplift and erosion of the basement blocks was limited to less than 1 5 km in the study area

post variscan tectonic and landscape evolution of the elbe fault zone and the lusatian block based on apatite fission track data and geomorphologic constraints abstract the elbe fault zone is a continental scale nw striking structure that contains faults of different kinematics some faults were active at different times since at least the variscan orogenesis in the late carboniferous the lusatian fault lf was one of the major structures of the elbe fault zone in the late cretaceous when nw striking faults of central europe experienced basin inversion and thrusting during a short lived pulse of contraction the lf displays a curved appearance on earth surface what is not compatible with its activity at only one well defined event possibly different faults where active along strike of the lf at different times apatite fission track thermochronology can distinguish differential exhumation or burial of neighbouring fault blocks if the vertical difference comprised at least 1 2 km this study presents apatite fission track data from the footwall and the hangingwall block of the lf and some other faults in its vicinity our new data show a clear difference between the hangingwall block of the lf the lusatian block with uniform 70 85 ma apparent ages and relatively long track lengths and the footwall block of the lf with 66 173 ma apparent ages and shorter and more variable track lengths for one section of the lf we can show that the cretaceous fault is not visible geomorphologically but was substituted by a neighbouring cenozoic reverse fault with a distinct fault scarp we used thermal history modelling to determine the timing and magnitude of exhumation and burial events from apparent apatite fission track ages and track length distributions we infer that the present morphological expression of the lf consist of smaller faults of different kinematics and age and present an evolution model for this section of the lf this study establishes the existence of similar striking reverse faults in direct vicinity and partly intersecting each other in the elbe fault zone this observation emphasizes the significance of the elbe fault zone as a continental scale zone of crustal weakness it has not only been reactivated several times since the variscan orogenesis but represents a cluster of similar striking faults of different age and kinematics

trapped charge thermochronometry and thermometry a status review abstract trapped charge dating methods including luminescence and electron spin resonance dating have high potential as low temperature 200 c ma 1 or elevated temperature underground settings 30 c despite this limitation trapped charge thermochronometry comprises a diverse suite of versatile methods and we explore potential future applications and research directions

fission track thermochronology of the ruhla crystalline complex new constraints on the post variscan thermal evolution of the nw saxo bohemian massif abstract to help clarify the relative and absolute timing of post variscan cooling and exhumation processes in the ruhla crystalline complex rcc situated in the nw part of the saxo bohemian massif eight zircon and eleven apatite fission track ages and nine apatite track length measurements have been obtained zircon fission track ages support an existing model of post variscan exhumation of the rcc as three discrete blocks the eastern and western blocks show cooling from peak metamorphic conditions to below 260 30 c by ca 300 ma and exposure by 296 ma the central block shows a later cooling to below 260 30 c by ca 270 ma and exposure at the surface by ca 256 ma apatite fission track data reveal late cretaceous accelerated cooling through the apatite partial annealing zone 120 to 60 c this can be correlated with tectonic inversion at this time the apatite data also indicate that the rocks of the rcc were at temperatures above 110 10 c before ca 85 ma this requires either an anomalously high palaeo geothermal gradient of ca 60 c km 1 during the late cretaceous or that the rcc region was originally covered by up to 1400 m of now eroded jurassic and cretaceous sedimentary rocks we favour a combination of both factors with accelerated erosion of missing overburden during a period of increased heat flow initiated at ca 85 ma

fission track dating of phosphate minerals and the thermochronology of apatite several phosphate minerals have been investigated for their usefulness in geochronology and thermochronology by the fission track method of these apatite ca5 po4 3 f cl oh has proved pre eminently suitable for this purpose for reasons discussed below apatite was one of the first minerals amongst many others to be investigated for fission track dating by fleischer and price 1964 and has subsequently become by far the most important of all the minerals used for dating by this method the usefulness of apatites for fission track dating arises from their near universal tendency to concentrate uranium within their structure at the time of crystallization and their widespread occurrence in all of the major rock groups price and walker 1963 first recognized the possibility that the accumulation of radiation damage tracks in natural minerals from the spontaneous nuclear fission of 238u within their lattices could be used for geological dating they also demonstrated that a simple chemical etching procedure served to enlarge these fission tracks to optical dimensions so that they could be observed and measured under an ordinary optical microscope price and walker 1962b 1963 this simple procedure quickly opened the way for a wide range of nuclear particle track studies in natural minerals and glasses e g fleischer et al 1975 the most important of which was fission track dating fleischer et al 1964 also showed that spontaneous or fossil fission tracks provided an explanation for various anomalous etch pits in apatite which had puzzled crystallographers over many years the essence of a fission track age determination involves measuring the number of tracks that have accumulated over the lifetime of the mineral along with an estimate of the amount of uranium that is present knowing the rate of spontaneous fission decay a geological age can be calculated detailed

on the calibration of fission track annealing models to obtain thermal histories from fission track length data the rates at which track lengths are reduced must be estimated the usual method is to use empirical equations calibrated via laboratory analogues a major concern is the extrapolation of the equations to predict temperatures on the geological time scale which is far outside the range of the calibration data using objective statistical criteria it is shown that the inclusion of geological data from age standards and deep boreholes is an important measure to ensure that model predictions of geological annealing rates are at least close to being correct it is shown that high temperature geological data should be the preferential target in the search for new field evidence a discussion on the use and limitations of geological data and their consequences is presented

petrography and geochemistry of the san miguel lignite jackson group eocene south texas the san miguel lignite deposit late eocene lower jackson group of south texas consists of four or more thin generally 1 m thick lignite benches that are separated by claystone and mudstone partings the partings are composed of altered volcanic air fall ash that has been reworked by tidal or channel processes associated with a back barrier depositional environment the purpose of this study is to examine the relationship between the ash yield and the petrographic and geochemical characteristics of the san miguel lignite as mined particular attention is given to 12 of the environmentally sensitive trace elements as be cd cr co hg mn ni pb sb se and u that have been identified as possible hazardous air pollutants haps by the united states clean air act amendments of 1990 a total of 29 rock and lignite samples were collected and characterized by geochemical and petrographic methods the major conclusions of the study are as follows 1 the distribution of mn is inversely related to the ash yield of the lignite samples this indicates an organic affinity or an association with finely disseminated minerals in the lignite that contain this element 2 on a whole coal basis the concentration of the haps element pb is positively related to ash yield in lignite samples this indicates an inorganic affinity for pb 3 average whole coal concentrations of as be sb and u in the san miguel samples are greater than published averages for these elements in other u s lignites 4 the upper and lower lignite benches of the san miguel deposit are both ash and algal rich indicating that these intervals were probably deposited in wetter conditions than those in which the middle intervals formed 5 the dominance of the eugelinite maceral subgroup over the huminite subgroup indicates that the san miguel lignites were subjected to peat forming conditions either biogenic or chemical that enabled degradation of wood cellular material into matrix gels or that the plants that formed these lignite benches were less woody and more prone to formation of matrix gels 6 an inertinite rich layer top of the b bed might have formed from widespread oxidation of the san miguel peat as a result of a volcanic ash fall which was subsequently reworked

fission track analysis and thermotectonic history of the main borehole of the chinese continental scientific drilling project abstract the chinese continental scientific drilling ccsd project part of the international continental drilling program icdp has completed drilling a 5158 m hole in the eastern part of the dabie sulu ultrahigh pressure metamorphic belt this study reports on an apatite fission track analysis of core samples from 0 to 4000 m depth in the ccsd main hole ccsd mh we determined the fission track ages of 38 apatite samples from different depths the ages range between 98 6 17 0 and 3 2 1 3 ma showing a general decreasing trend with depth from 87 1 11 2 ma at the surface to 3 2 1 3 ma at 3899 m depth as a first approximation an average uplift rate of 35 m ma is calculated for the period 90 30 ma the trend in ages within the borehole shows some fluctuations and indicates movements along major faults it is inferred that the highest level major normal fault occurs at a depth of 350 m recording a vertical displacement of 400 m movement along another prominent normal fault at a depth of 2150 m occurred subsequent to 25 ma three major reverse faults occur at about 2450 3050 and 3250 m depth testing geological constrains against the fission track data set indicated an agreement with a reheating of the area during the late cretaceous and eocene followed by cooling to 80 c during the eocene and a low cooling until the samples reached their present day position in the donghai area

fission track dating of the south eastern bohemian massif waldviertel austria thermochronology and long term erosion apatite fission track thermochronology was applied to the outcropping variscan basement of the south eastern bohemian massif in order to resolve its post variscan cooling and denudation history nineteen samples could be dated by the grain population method the ages range from 235 to 90 ma middle triassic to middle cretaceous neglecting some local variations they show a decrease from the western edge of the moravian thaya window towards the west and the south fission track length histograms mainly exhibit broad distributions with arithmetic means between 12 3 and 13 4 m and standard deviations between 1 5 and 2 0 m thermochronological model calculations of the measured data demonstrate that the apatite fission track memory of the samples reaches back until the begin of the cretaceous and for some samples even until the permian the regional fission track cooling pattern is not related to the limitations and the internal structure of the moravian thaya window which appears to be an elder probably late carboniferous to permian tectonic feature also the vitis fault does not delimit areas of different thermochronological behaviour therefore significant vertical offset on that fault can be excluded for the cretaceous and cenozoic thermochronological model calculations of fission track ages and length data are consistent with the assumption of regional sedimentary reburial during the late cretaceous the amount of reburial could have attained 1 km the cenozoic bulk denudation was in the order of 1 to 3 km

post variscan thermal history of the moravo silesian lower carboniferous culm basin ne czech republic sw poland abstract apatite fission track analysis aft and zircon u th he thermochronology zhe have been carried out for a lower carboniferous greywacke succession of the moravo silesian culm basin in the nizk jesenik mountains the range of apparent zircon helium ages is 303 233 ma late carboniferous to early triassic in the eastern part of the basin whilst they are significantly younger in the western part ranging from 194 to 163 ma early middle jurassic apatite fission track central ages range from 152 latest jurassic to 44 ma eocene with the majority being grouped between 114 aptian and 57 ma paleocene all samples experienced substantial post depositional thermal reset both the aft ages and the zhe are considerably younger than the depositional ages the mean track length varies in the range between 12 5 and 15 4 m the unimodal track length distribution the relatively short mean track length in most samples and their rather low standard deviation values 1 2 to 2 1 m indicate that their thermal history was determined by variscan and post variscan heating event s followed by a prolonged residence in the apatite partial annealing zone in the mesozoic and finally by cooling in the paleogene geological evidence combined with thermal modeling based on aft and zhe data indicate that the lower carboniferous strata had already reached maximum palaeotemperatures in the late carboniferous however they were presumably later re heated during the permian triassic post variscan extensional tectonics events were responsible for high heat flow that together with carboniferous burial could account for the reset of both thermochronometers a major phase of cooling occurred in the late cretaceous finally exhumation was probably faster in the paleogene causing the present day exposure of the studied rocks

apatite fission track dating and low temperature history of the bavarian forest southern bohemian massif apatite fission track aft dating applied to uplifted variscan basement blocks of the bavarian forest is employed to unravel the low temperature history of this segment of the bohemian massif twenty samples were dated and confined track lengths of four samples were measured most samples define cretaceous apt ages between 110 and 82 ma albian to campanian and three samples give older 148 140 ma jurassic cretaceous boundary ages no discernible regional age variations exist between the areas north east and south west of the pfahl shear zone but 500 m post jurassic and post cretaceous vertical offsets along this and other faults can be inferred from elevation profile analyses the aft ages clearly postdate the variscan exhumation history of the bavarian forest thermal modeling reveals that the ages are best explained by a slight reheating of the basement rocks to temperatures within the apatite partial annealing zone during the middle and late jurassic and or by late cretaceous marine transgression causing burial heating which affected marginal low lying areas of the bohemian massif and the bavarian forest late jurassic period was followed by enhanced cooling through the 120 60 c temperature interval during the subsequent exhumation phase for which denudation rates of 100 m myr 1 were calculated on a regional scale jurassic cretaceous aft ages are ubiquitous in marginal structural blocks of the bohemian massif and seem to reflect the exhumation of these zones more distinctly compared to central parts

suppression of thermal maturity indicators in lacustrine source rocks a case study of dongying depression eastern china abstract the paleogene shahejie formation of the dongying depression in eastern china is a unique region and can offer insights into the suppression of thermal maturity in a large set of successive lacustrine shales this study focuses on the paleogene shahejie formation of n 38 well in the dongying depression the unusual distribution of thermal maturity indicators such as vitrinite reflectance vro and c29 sterane thermal parameters was investigated through geochemical analysis the research interval 2770 3376 m was divided into three parts the upper part of es32 2770 2990 m the lower part of es32 2990 3190 m and the es31 3190 3376 m the es31 mainly contained organic matter type i and some type ii which included mostly good and excellent source rocks meanwhile the upper es32 mainly contained organic matter type iii which included mostly poor and moderate source rocks the parameters g c30h c35h c31 35h c31m c31h c29 20s 20s 20r c31 22s 22s 22r and c32 22s 22s 22r showed a different distribution corresponding to the different lake sedimentary environments various organic facies were developed at the different evolution stages of the lake basin which showed a noticeable influence on the parameters the thermal maturity indicator vro and molecular thermal parameters such as c29 20s 20s 20r c31 22s 22s 22r c32 22s 22s 22r and c31m c31h presented abnormal distributions in the large set of lacustrine shales especially in the es31 this observation suggested suppression of several thermal maturity indicators vro suppression positively correlated well with the corrected hydrogen index and alginite content in maceral composition the high content of alginite group was considered to be the primary reason behind the evident negative vro anomaly

vitrinite and vitrinite like solid bitumen reflectance in thermal maturity studies correlations from diagenesis to incipient metamorphism in different geodynamic settings abstract vitrinite reflectance vr is a useful and reliable parameter to monitor the level of organic matter maturation from the immature stage to graphite additionally vr is a useful and essential tool in modelling the temperature maturation time path huminite vitrinite bearing sedimentary and meta sedimentary rocks can be used to reconstruct the thermal history of basins or orogenic terranes throughout their geological history the usefulness of vr evidently depends on the presence of huminite vitrinite phytoclasts however pre upper silurian rocks and many organic rich marine rocks e g sapropelic sediments lack of huminite vitrinite particles furthermore vitrinite is sparse in carbonate sediments however the presence of bitumen in rocks lacking type iii kerogen provides a valuable aid via its reflectance vitrinite like solid bitumen reflectance vlbr and or solid bitumen reflectance br to fulfil the above described tasks that vr enables this study presents basically a relationship between br vlbr and vr for various types of geodynamic settings and over the largest possible range of maturation levels so that vlbr may be used as a substitute for vr whereas the effort to correlate vr with br is not novel it is the first time that the vr br correlation is re judged discriminating bitumen from vlb moreover for the first time the correlation is established for various geodynamic settings the investigated geological contexts are 1 sedimentary basins e g the saar ruhr ohio west virginia and petrosani basins 2 metasedimentary terranes occurring as inverted basins in orogenic belts e g from the subalpine molasse helvetic austroalpine and danubian nappe systems and having suffered from very low to low grade metamorphism from anchizone to greenschist facies 3 metasedimentary terranes e g slates and schists from the franciscan and alpine belts that were subducted at anchizone to blueschist facies conditions and 4 metasedimentary rocks affected by contact metamorphism together the frequent geological settings are referred and most of the earth geothermal conditions and heat fluxes considered despite temperature pressure and heating time also heat flow gradient dependences cannot be ignored

positioning the titanite fission track partial annealing zone abstract as part of the ktb kontinentale tiefbohrung programme in germany titanite sphene fission track data were acquired for samples to a depth of 9000 m where the host rock temperature is 265 c at this depth age and confined track length information suggest that the partial annealing zone for the fission tracks in titanite was not reached by reconstructing the thermal history and backstacking of an uplifted partial annealing zone it is suggested that the in situ partial annealing zone is likely to be found in the region 265 310 c this value is more precise than previous estimates of the titanite partial annealing zone and it is also higher than previous estimates microprobe analysis indicates that the chemical composition of the titanites is rather homogeneous throughout the whole drilled section

fission track dating of the western border of the bohemian massif thermochronology and tectonic implications since 1985 apatite fission track analysis was applied to more than 70 samples from surface outcrops and shallow boreholes at the western margin of the bohemian massif apatite ages were determined by the grain population method additional information from the frequency distributions of fully confined spontaneous tracks was used for modelling of t t paths in the low temperature range 120 c seven zircon samples were dated by the external detector method zircon ages between 283 and 215 ma indicate unroofing during the permian molasse stage and the triassic tectonic quiescence and slow subsidence prevailed from the jurassic until the middle cretaceous in the basement area south of weiden a mesozoic partial annealing zone for apatite fission tracks is now exposed at the surface farther north the basement was affected by stronger cretaceous and palaeogene erosion which yielded cooling ages between 110 and 49 ma this second period of post variscan denudation was correlated to reverse faulting along the franconian line

suppressed vitrinite reflectance in the ferron coalbed gas fairway central utah possible influence of overpressure chemical and thermoplastic properties of coals in the ferron coalbed methane fairway indicate that coals in the north are of higher rank than coals in the south measured vitrinite reflectance does not accurately show this variation of coal rank although vitrinite reflectance in the southern and central part of the fairway is consistent with other measures of coal rank suppressed vitrinite reflectance is observed in the north where methane contents are relatively high this coincidence of suppressed reflectance and relatively high coalbed methane yields may be significant we speculate that the suppressed reflectance values result from a burial history where overpressure developed during the early stages of coalification and persisted until recent uplift and cooling such instances may be diagnostic of prospective coalbed methane targets elsewhere

empirical constraints on the titanite u th he partial retention zone from the ktb drill hole we analyzed u th he ages of titanite from both the initial pilot hole 4 km depth and the main drill hole 9 km depth of the german continental deep drilling project ktb to empirically evaluate the titanite u th he partial retention zone heprz and laboratory helium diffusion data laser u th he ages on single titanite fragments from the ktb drill hole uncorrected for emission range from 94 to 2 ma with reproducibility better than 9 nearly invariant titanite u th he ages concordant with reported apatite fission track data suggest that rocks from the upper 3 km of the ktb drill hole rapidly cooled from temperatures 200 to 110 c between 75 and 85 ma followed by protracted cooling below 3 km mean titanite u th he ages decrease systematically with increasing borehole depth and down hole temperature in a pattern similar to the titanite heprz predicted on the basis of laboratory determined he diffusivities our results demonstrate that experimental titanite he diffusion data are applicable in the natural setting and that titanite u th he thermochronometry provides a means to reliably reconstruct and quantify thermal histories between 100 and 180 c bridging the temperature ranges constrained by other techniques such as 40 ar 39 ar k feldspar multi diffusion domain modeling 350 150 c and apatite fission track dating 110 c

reconstructing the phytoplankton community of the cariaco basin during the younger dryas cold event using chlorin steryl esters 1 a record of the downcore distribution of chlorin steryl esters cses through the younger dryas was produced from cariaco basin sediments in order to assess the potential use of cses as recorders of the structure of phytoplankton communities through time using an improved high performance liquid chromatography method for the separation of cses we find significant changes in the distribution of cses during the younger dryas in the cariaco basin during the younger dryas enhanced upwelling in the cariaco basin caused an increase in the diatom population and therefore an increase in the relative abundance of cses derived from diatoms in contrast the dinoflagellate population and therefore cses derived from dinoflagellates decreased in response to the climate change during the younger dryas these community shifts agree well with the shifts observed in the present day on a seasonal basis that result from the north south migration of the intertropical convergence zone over the cariaco basin we also identify changes in the abundance of several cses that seem to reflect rapid warming and cooling events this study suggests that cses are useful proxies for reconstructing phytoplankton communities and paleoenvironments index terms 1055 geochemistry organic geochemistry 4267 oceanography general paleoceanography 4855 oceanography biological and chemical plankton keywords younger dryas cariaco basin chlorin steryl esters

osl thermochronometry of feldspar from the ktb borehole germany the reconstruction of thermal histories of rocks thermochronometry is a fundamental tool both in earth science and in geological exploration however few methods are currently capable of resolving the low temperature thermal evolution of the upper 2 km of the earth s crust here we introduce a new thermochronometer based on the infrared stimulated luminescence irsl from feldspar and validate the extrapolation of its response to artificial radiation and heat in the laboratory to natural environmental conditions specifically we present a new detailed na feldspar irsl thermochronology from a well documented thermally stable crustal environment at the german continental deep drilling program ktb there the natural luminescence of na feldspar extracted from twelve borehole samples 0 1 2 3 km depth corresponding to 10 70 c can be either i predicted within uncertainties from the current geothermal gradient or ii inverted into a geothermal palaeogradient of 29 2 c km 1 integrating natural thermal conditions over the last 65 ka the demonstrated ability to invert a depth luminescence dataset into a meaningful geothermal palaeogradient opens new venues for reconstructing recent ambient temperatures of the shallow crust 200 c ma 1 range although na feldspar irsl is prone to field saturation in colder or slower environments the method s primary relevance appears to be for borehole and tunnel studies where it may offer remarkably recent 0 3 ma information on the thermal structure and history of hydrothermal fields nuclear waste repositories and hydrocarbon reservoirs

the origin and distribution of haps elements in relation to maceral composition of the a1 lignite bed paleocene calvert bluff formation wilcox group calvert mine area east central texas abstract the origin and distribution of twelve potentially hazardous air pollutants haps as be cd cr co hg mn ni pb sb se and u identified in the 1990 clean air act amendments were examined in relation to the maceral composition of the a1 bed paleocene calvert bluff formation wilcox group of the calvert mine in east central texas the 3 2 m thick a1 bed was divided into nine incremental channel samples 7 lignite samples and 2 shaley coal samples on the basis of megascopic characteristics results indicate that as cd cr ni pb sb and u are strongly correlated with ash yield and are enriched in the shaley coal samples we infer that these elements are associated with inorganic constituents in the coal bed and may be derived from a penecontemporaneous stream channel located several kilometers southeast of the mining block of the haps elements studied mn and hg are the most poorly correlated to ash yield we infer an organic association for mn hg may be associated with pyrite the rest of the trace elements be co and se are weakly correlated with ash yield further analytical work is necessary to determine the mode of occurrence for these elements overall concentrations of the haps elements are generally similar to or less than those reported in previous studies of lignites of the wilcox group east central region texas petrographic analysis indicates the following ranges in composition for the seven lignite samples liptinites 5 8 huminites 88 95 and inertinites trace amounts to 7 samples from the middle portion of the a1 bed contain abundant crypto eugelinite compared to the rest of the samples this relationship suggests that the degradation of plant material was an important process during the development of the peat mire with the exception of hg and mn relatively low levels of the haps elements studied are found in the samples containing abundant crypto eugelinite we infer that the peat forming environment for this portion of the coal bed was very wet with minimal detrital input relatively high concentrations of crypto humotelinite were found in samples from the top and base of the coal bed the presence of abundant crypto humotefinite in this part of the coal bed suggests the accumulation of wood rich peat under conditions conducive to a high degree of tissue preservation in the peat mire although several of the trace elements be co ni and sb exhibit enrichment in these samples they are not necessarily chemically associated with humotelinite we infer that these elements with the exception of be are possibly associated with deposition of the roof and floor rock of the coal bed however further analytical work would be necessary to confirm this hypothesis beryllium may have an organic origin

upper cretaceous feldspars in the cenozoic limagne basin a key argument in reconstructing the palaeocover of the massif central france abstract the northern part of the n s trending basin of the limagne graben located in the northern part of the massif central france contains oligocene and miocene calcareous lacustrine deposits the area is known for its stromatolite reefs surrounded by marl clay and uncemented carbonate sand with oncolites because the origin of the carbonate accumulated by cyanobacteria has long been debated the clayey deposits associated with the stromatolites were analysed using xrd sem and k ar dating methods the results show a monotonous assemblage of carbonates dioctahedral smectite illite smectite reichweite r 0 glauconitic illite and abundant orthoclase detrital minerals such as quartz and detrital illite are found near the basin s borders but are very scarce in its central part indicating a lack of detrital input from the regional basement hence the abundant orthoclase found in all the clayey deposits of the limagne basin cannot be linked to erosion of the surrounding hercynian basement the sem analysis showed the orthoclase crystals to have a tabular morphology with sharp boundaries and to be embedded within a clay matrix whilst the k ar dating of the orthoclase and glauconitic illite yielded ages ranging from 90 to 66 2 ma i e turonian to maastrichtian these two results clearly indicate that the fill of the limagne basin composed mainly of carbonate clay and orthoclase must have been partly due to the erosion of an upper cretaceous sedimentary blanket once covering the massif central basement this cover was probably constituted of chalk dioctahedral smectite i s and glauconitic illite associated with authigenic orthoclase and flint flints are found reworked in the alluvial formations of the late pliocene lower bourbonnais sands and clays sables et argiles du bourbonnais and in the pleistocene terraces moreover relicts of the upper cretaceous cover were preserved during the sedimentary filling of the cenozoic limagne basin authigenic orthoclase of similar shape has been described in the chalk group of the paris basin and from localities in northern france and belgium the mineral is rare in the turonian chalk but increases rapidly at the base of the coniacian to campanian chalk it has also been noted that the number of orthoclase crystals increases as the quantity of clastic components decreases similar orthoclase crystals were found associated with dioctahedral smectite in the decarbonated residues of the coniacian to santonian chalk from fecamp and etretat northern france moreover our results are consistent with other data from within and around the paris basin such as the palaeogeography and facies distribution of the chalk formations the residual flints in the clay with flints of the southern paris basin and around the morvan and apatite fission track thermochronology data from the hercynian basement of the massif central and the morvan all these data indicate a major connection between the paris basin and the tethys and an extensive palaeocover on the massif central and morvan basement

extraction of whole versus ground source rocks fundamental petroleum geochemical implications including oil source rock correlation abstract in petroleum geochemistry extractable hydrocarbons hcs in source rocks have typically been studied by grinding the rock to a fine powder 100 mesh and then extracting the hcs from the rock with a solvent this procedure carries the implicit assumption that the hcs are homogeneously distributed throughout the rock however sequential soxhlet extractions of whole unpowdered source rocks have shown that progressive extracts from the same rock can be quite different and may not even correlate with each other a crude oil like material clearly has been fractionated from indigenous bitumen in these rocks has moved to cracks and parting laminae in the rocks is ready for expulsion from the rocks and is thus most accessible to the first extracting solvents this process which we believe is largely due to hc gases and carbon dioxide generated over all maturation ranks in source rocks carries petroleum geochemical implications of a fundamental nature for oil source rock correlations and gives insight into primary migration mechanisms origin of oil deposits and use of maturity and organic facies indices

rheology predictions across the western carpathians bohemian massif and the pannonian basin implications for tectonic scenarios on the basis of extrapolation of failure criteria lithology and temperature models we predict the rheology of the lithosphere for several sections through the carpathians and surrounding regions our models show significant lateral variations in rheology for the different tectonic units with important implications for the tectonic evolution the theologically strong lithosphere of the polish platform area contrasts with the weak lithosphere of the pannonian basin indicating that the arcuate shape of the carpathian orogen is primarily caused by an inherited curvature of an ancient embayment in the foreland with the pannonian units passively filling the space the polish platform and the moesian platform exhibit a similar rheological anisotropy caused by nw se trending weakness zones paralleling the tornquist teisseyre zone this anisotropy was the main controlling factor on the behavior of the lithosphere in this area since cadomian times as documented by the geological evolution of the sudety mountains and the mesozoic polish trough including the late cretaceous alpine inversion and the neogene development of the carpathian foreland this rheological anisotropy appears to have a major controlling impact on the development of at least the eastern part of the european lithosphere rheology predictions for the bohemian massif support the idea that the rigid lithosphere of the bohemian massif governed the bending of the alpine carpathian transition zone expressed in the large scale wrench movements opening the vienna basin in the foreland area detachment levels are predicted for upper and lower crustal levels leading to a decoupling of crustal and subcrustal flexure in most areas comparison with basin formation models indicates that our predictions for effective elastic thickness eet are similar to those derived from flexural models for the foreland area also eet predictions from extensional basin models in the pannonian region yield values close to our findings

long term landscape evolution of the northeastern margin of the bohemian massif apatite fission track data from the erzgebirge germany to study the relative and absolute timing of post variscan cooling and denudation processes in the erzgebirge of the mid european variscides eight samples for apatite fission track aft analysis were collected from a 1 300 m drill core the fission track data reveal two stages of accelerated cooling through the apatite partial annealing zone apaz i e 110 10 60 c in the late jurassic late cretaceous and in the late cenozoic respectively late jurassic late cretaceous cooling corresponding to denudation of 1 5 5 9 km has been related to wrench tectonics along the elbe zone during triassic jurassic pangea breakup late cenozoic exhumation of 2 1 5 6 km and the increase of the geothermal gradient from 17 5 c km 1 oligocene miocene to 25 27 c km 1 recent is likely connected to the formation of the eger graben starting from the oligocene as a result of the late alpine orogenic phases

the franciscan complex california usa the model case for return flow in a subduction channel put to the test the model of return flow in a subduction channel rfsc is put to the test by opposing key assumptions of the model to an integrated review of field data petrology geochronology and structures of high p melanges of the franciscan subduction complex fsc to which rfsc has been first applied key assumptions are i the subduction channel sc is a low viscosity zone of finite width restrained by the rigid subducted and overriding plates ii forced return flow in the sc is associated with formation and km scale displacements of small tectonic blocks 1 km in a highly deformable matrix iii this results in apparently random distributions and close associations of blocks exhumed from different depths hence the block in matrix structures and exotic blocks in high p melanges would reflect the structural state at depth of the sc on the basis of the predictions ensuing from the key assumptions of the rfsc model on the rock record it is detailed why the actual record of the high p melanges of the fsc does not comply with this perception the record rather reflects recurring subduction underplating associated decollement erosion and mingling of high p rocks by sedimentary processes in the trench all occurring in an 80 m y lasting period distributed deformation of the melange matrix is unrelated to formation of apparently chaotic block in matrix structures since i creation subduction ascent and cooling of exotic blocks on counterclockwise p t paths predates deposition of the bulk of the metasediments constituting the matrix by 20 40 m y ii deformation of the matrix occurs during a second loop of high p metamorphism postdating creation and ascent of the exotic blocks by at least 20 40 m y iii the magnitudes of distributed deformation of the matrix are too low to cause juxtaposition of blocks different in p t paths against each other from km scale vertical distances instead narrow few tens of metres wide fault shear and decollement zones formed at locally high pore fluid pressures accumulate the major tectonic transport during high p metamorphism they bound several 100s of metres wide tabular tectonic bodies that are coherent sedimentary processes at the active continental margin formed the bulk of the melanges tectonically formed block in matrix structures within the shear and decollement zones are unrelated to juxtaposition of exotic blocks universal diagnostic criteria are developed to identify return rfsc as a mechanism that potentially amalgamates heterogeneous metamorphic terrains by using field data petrology and geochronology

variations in vitrinite reflectance with organic facies examples from pennsylvanian cyclothems of the midcontinent u s a abstract significant variations in vitrinite reflectance r0 with organic facies have been demonstrated from pennsylvanian aged cyclothems of the midcontinent u s a thermal alteration index tai and rock eval tmax values remain relatively constant through these thin lithologic successions irregardless of facies and are in reasonable agreement with r0 measurements on interbedded coal organic rich black and phosphatic black shales which contain a significant component of liptinitic organic matter of presumed marine algal derivation display r0 values which are suppressed relative to the coal benchmark a distinct correlation between increased hydrogen index hi and liptinite content with suppressed reflectivities is apparent more oxic facies e g calcareous and fosiliferous gray shales and limestones often display r0 s that are considerably higher than for coal soxhlet extraction prior to maceration yielded no variation in reflectance compared to non extracted kerogens suggesting bitumen adsorption was not the cause of the apparent suppression in the organic rich black shales lower total organic carbon toc normalized bitumen contents and rock eval transformations ratios in liptinite rich facies suggest different reaction kinetics for kerogen types with terrestrial organic matter maturing at an earlier stage than hydrogen rich marine derived organic matter

40ar 39ar thermochronometry of k feldspar from the ktb borehole germany abstract the great depth and relatively steep geothermal gradient 29 c km of the ktb deep crustal borehole located in the bavarian region of germany provides the basis for our study of diffusive argon loss in k feldspar the observed borehole temperature at 9 km is 265 c which reaches well into the argon closure interval for k feldspar 125 350 c four microcline and two adularia samples distributed relatively evenly down the 9 1 km deep borehole were analyzed by the 40ar 39ar method the thermal histories of the shallow samples are consistent with existing thermochronologic data from the borehole after correction for chlorine correlated excess 40ar the deepest two samples result in age spectra that record zero apparent ages over the first few percent of 39ar released which is predicted by diffusion theory where a range of diffusion volumes are present inverse modeling of the argon kinetics of these two deep samples reveals that the present elevated geothermal gradient in the borehole has existed for only the last approximately one million years recent volcanism within 30 km of the borehole is likely the source of this present day thermal pulse

the influence of extractable organic matter on vitrinite reflectance suppression a survey of kerogen and coal types abstract the vitrinite reflectance suppression literature shows that while bitumen impregnation of the vitrinite group is often invoked as a significant contributor to suppression its existence is not often supported by petrological evidence this study examines bitumen impregnation as a factor in vitrinite suppression by comparing the vitrinite reflectance of source rock and coal samples before and after solvent extraction bitumen often defined as organic matter soluble or extractable in certain organic solvents should be removed by soxhlet method solvent extraction using chloroform removing the extractable bitumen should restore the suppressed reflectance to its true higher value however the solvent extracted samples averaged 0 014 r v less than that of the unextracted samples we conclude from these results and from other published data that reflectance suppression by bitumen impregnation in the vitrinite maceral group above the huminite stage of gelification is seemingly a rare phenomenon and whose effect on suppressing vitrinite reflectance is typically negligible

composition and organic maturity of middle jurassic coals north east greenland evidence for liptinite induced suppression of huminite reflectance abstract middle jurassic coals from kuhn o north east greenland may contain up to 85 vol liptinite principally resinite up to 68 6 vol the coals are thus petrographically comparable to the middle jurassic muslingebjerg formation coals at hochstetter forland approximately 40 50 km to the north and they are inherently excellent petroleum source rocks liptinite poor 6 0 vol coal samples from both kuhn o and hochstetter forland yield mean random huminite reflectance values of 0 49 0 53 ro implying a rank of sub bituminous a above a threshold value somewhere between 3 and 24 vol resinite and 6 and 35 vol total liptinite significant reflectance suppression is induced and between 24 and 69 vol resinite and 35 and 85 vol total liptinite a nearly linear inverse relationship exists between the content of liptinite resinite and the mean random reflectance values at the highest liptinite resinite contents reflectance suppression may be up to 0 23 ro the reflectance suppression is related to bitumen adsorption caused by bitumen expulsion from resinite and total reflectance distributions of the huminite fractions suggest that the reflectance of all huminite macerals is lowered with increasing liptinite resinite content

petrography and geochemistry of selected lignite beds in the gibbons creek mine manning formation jackson group paleocene of east central texas this study examined the petrographic and geochemical characteristics of two lignite beds 3500 and 4500 beds manning formation jackson group eocene that are mined at the gibbons creek mine in east central texas the purpose of the study was to identify the relations among sample ash yield coal petrography and trace element concentrations in lignite and adjoining rock layers of the gibbons creek mine particular interest was given to the distribution of 12 environmentally sensitive trace elements as be cd cr co hg mn ni pb sb se and u that have been identified as potentially hazardous air pollutants haps in the united states clean air act amendments of 1990 eleven lignite floor and rock parting samples were collected from incremental channel samples of the 3500 and 4500 beds that were exposed in a highwall of pit a3 at the gibbons creek mine short proximate and ultimate and forms of sulfur analyses were performed on all lignite samples and lignite and rock samples were analyzed for 60 major minor and trace elements representative splits of all lignite samples were ground and cast into pellets and polished for petrographic analyses in blue light fluorescence and reflected white light to determine liptinite inertinite and huminite maceral group percentages the following observations summarize our results and conclusions about the geochemistry petrography and sedimentology of the 3500 and 4500 beds of the gibbons creek lignite deposit 1 weighted average dry db ash yield for the two beds is 29 7 average total sulfur content is 2 6 and average calorific value is 7832 btu 18 22 mj kg ash yields are greatest in the lower bench 59 33 db of the 3500 bed and in the upper bench of the 4500 bed 74 61 db 2 for lignite samples on a whole coal basis the distributions of two of the haps pb and sb are positively related to ash yield probably indicating an inorganic affinity for these elements by using cluster analysis we found that be and cd were poorly associated with ash yield indicating a possible organic affinity and that ni se hg u and pb cluster with most of the rare earth elements 3 the dominance of the crypto eugelinite maceral subgroup over the crypto humotelinite subgroup suggests that all gibbons creek lignites were subjected to peat forming conditions either biogenic or chemical conducive to the degradation of wood cellular material into matrix gels or that original plant material was not very woody and was prone to formation of matrix gels the latter idea is supported by pollen studies of gibbons creek lignite beds results indicate that the peat was derived in part from marsh plants low in wood tissue 4 the occurrence of siliceous sponge spicules in the lower benches of the 3500 bed suggests the original peat in this part of the bed was deposited in standing fresh water 5 the petrographic data indicate that the upper sample interval of the 3500 bed contains more inertinite 3 than the other samples studied increases in inertinite content in the upper part of the 3500 bed may have been associated with alteration of the peat by acids derived from the volcanic ash or could have been caused by fire oxidation and drying or biologic alteration of the peat in the paleo mire