geochronology of early to middle paleozoic tectonic development in the southwest newfoundland gander zone southwest newfoundland s gander zone was once considered part of the collided eastern margin of an early paleozoic iapetus ocean distinguished from the rest of the gander zone by the extensive exposure of a polydeformed amphibolite to greenschist facies sequence considered devonian in age overlying presumed precambrian basement it was later found that truly devonian strata were confined to the cape ray fault system the local northwestern boundary of the zone u pb zircon isotopic ages of 452 13 51 ma and 458 22 29 ma on metavolcanic rocks in the upper part of the sequence southeast of the fault system indicate that ordovician and possibly older rocks underlie the gander zone itself a temporal framework for the three main stages of regional deformation corresponding to pre metamorphic recumbent folding d 1 and transpression d 2 and d 3 is presented using u pb and 40 ar 39 ar dates of granitoid and metamorphic rocks d 1 is bracketed as late o

geochemistry reservoir characterization and hydrocarbon generation potential of lacustrine shales a case of yq 1 well in the yuqia coalfield northern qaidam basin nw china abstract ever since a breakthrough of marine shales in china lacustrine shales have been attracting by the policy makers and scientists organic rich shales of the middle jurassic strata are widely distributed in the yuqia coalfield of northern qaidam basin in this paper a total of 42 shale samples with a burial depth ranging from 475 5 m to 658 5 m were collected from the shimengou formation in the yq 1 shale gas borehole of the study area including 16 samples from the lower member and 26 samples from the upper member geochemistry reservoir characteristics and hydrocarbon generation potential of the lacustrine shales in yq 1 well were preliminarily investigated using the experiments of vitrinite reflectance measurement maceral identification mineralogical composition carbon stable isotope low temperature nitrogen adsorption methane isothermal adsorption and rock eval pyrolysis the results show that the shimengou shales have rich organic carbon averaged 3 83 which belong to a low thermal maturity stage with a mean vitrinite reflectance ro of 0 49 and an average pyrolytic temperature of the generated maximum remaining hydrocarbon tmax of 432 8 c relative to marine shales the lacustrine shales show low brittleness index averaged 34 9 but high clay contents averaged 55 1 high total porosities averaged 13 71 and great langmuir volumes averaged 4 73 cm 3 g unlike the marine and marine transitional shales the quartz contents and brittleness index bi values of the lacustrine shales first decrease then increase with the rising toc contents the kerogens from the upper member shales are dominant by the oil prone types whereas the kerogens from the lower member shales by the gas prone types the sedimentary environment of the shales influences the toc contents thus has a close connection with the hydrocarbon potential mineralogical composition kerogen types and pore structure additionally in terms of the hydrocarbon generation potential the upper member shales are regarded as very good and excellent rocks whereas the lower member shales mainly as poor and fair rocks in overall the shales in the top of the upper member can be explored for shale oil due to the higher free hydrocarbon amount s1 whereas the shales in the lower member and the upper member with the depths greater than 1000 m can be suggested to explore shale gas

stable carbon isotopes of coal derived gases sourced from the mesozoic coal measures in china coal derived large scale gas fields derived from the mesozoic coal measures in china are mainly distributed in the middle lower jurassic coal measures in the tarim junggar and turpan hami basins in northwest china and the upper triassic xujiahe formation coal measure in sichuan basin central china in 2011 the annual production was 21 6 109 m3 and the proved geological reserves were 2485 109 m3 accounting for 21 and 30 of the total in china respectively based on analyses of gas composition and stable carbon isotopes ratios of 203 samples and stable carbon isotopes of 102 co2 samples the following conclusions were made a based on diagnostic plots using the stable carbon isotopic and molecular composition of gas samples alkane gas from the mesozoic coal measures in china is shown to be coal derived b according to the 13c2 vs c2h6 plot of a great number of oil derived and coal derived gases in china it is concluded that gases with 13c2 28 5 are coal derived and those with 13c2 28 5 are oil derived in most cases c among the natural gases from the mesozoic coal measures in china primary coal derived gases with normal carbon isotopic distribution pattern among the c1 c4 alkanes i e 13c1 13c2 13c3 13c4 are dominant d carbon isotopic pattern reversal mainly results from the mixing of coal derived gases having different maturities but the same source and secondly from microbial oxidation of propane e g mu 3 and mu 4 wells in the gumudi gas field junggar basin e co2 in the coal derived gases from the mesozoic coal measures in china has both biogenic and abiogenic origins the biogenic origin is dominant and the abiogenic co2 is mainly found in the kuqa depression in the tarim basin and western sichuan basin f isotopic differences between heavy hydrocarbon gases and methane become less with increasing maturity

the palaeolatitude controversy in the silurian of newfoundland resolved new palaeomagnetic results from the central mobile belt abstract a detailed palaeomagnetic investigation of early silurian volcanics of the lawrenceton formation in the central mobile belt cmb of newfoundland reveals primary remanence that places the sampled part of the cmb on the margin of laurentia in low southerly latitudes in the early silurian the palaeomagnetic data indicate large vertical axis net clockwise rotations within the cmb and between the cmb and cratonic laurentia the volcanics were folded faulted and in places cleaved in silurian to early devonian times anisotropy of magnetic susceptibility measurements on lava flow samples verify field observations of a primary flow parallel foliation and confirm field measurements of the palaeo horizontal a well developed tectonic fabric was detected at one sampling site near the reach fault silurian redbeds of the big indian pond formation were also sampled for palaeomagnetic study the sediments are folded faulted and cleaved a statistically sound syn folding remanence was identified which in a tectonically corrected state is consistent in direction with the remanence in the silurian volcanics the sampled sediments are more intensely deformed than the volcanics and magnetic anisotropy measurements indicate both primary layering and secondary cleavage related fabrics in varying degrees from site to site it is possible that cleavage development resulted in remanence reorientation leading to the illusion of syn folding remanence when in fact the remanence was acquired prior to folding previously published palaeomagnetic investigations of silurian rocks in the cmb revealed a discrepancy in palaeofield inclination between volcanic and sedimentary rock types the sedimentary rocks yielded shallow inclinations and the volcanics intermediate inclinations inclination shallowing in the sediments was put forward as an explanation as well as contamination of the sedimentary results with a shallow overprint others argued that the results from the volcanics were in error the present investigation demonstrates that key volcanics carry a shallower remanence than previously thought bringing them into approximate agreement with the majority of the results from sediments steep results from the springdale volcanics and very shallow results from the king george iv lake sediments are at variance with the rest of the data the springdale result has large error limits that overlap with the other data the anomalous king george iv result remains an outlier

curved vein fibres an alternative explanation abstract veins occurring at the edge of the dextral indian islands fault newfoundland are folded in response to a fault parallel ductile shear the veins which locally constitute a penetrative fabric element at outcrop scale are composed mainly of calcite and have a narrow rim of quartz and chlorite both the calcite and quartz are generally fibrous and lattice distortion in the calcite is not commensurate with the observed degree of fibre curvature this observation supports the popular view that curved fibres grow curved as they track the vein opening vector it is demonstrated however that the curvature in the material described here is due to deformation and that the lack of strong lattice distortion is due in part to polygonization and to recrystallization all observations are consistent with both the calcite and the quartz fibres having grown perpendicular to the vein walls the chlorite orientation is controlled by the orientation of mica grains in the country rock in some veins markers make it possible to define the net opening direction and in all examples it is demonstrated that the direction has not been tracked by the fibres since this conclusion may be more generally applicable caution should be exercised in interpreting kinematics on the basis of fibre geometry where vein density is high the veins and country rock screens separating them form a multilayer sequence that is folded into fairly harmonic folds the folds appear to have a cleavage transected relationship to the regional cleavage but the cleavage is shown to predate the folds

variations of natural gas carbon isotope type curves and their interpretation a case study natural gas is dominated by low molecular weight gaseous hydrocarbons c1 c5 whose genetic and diagenetic information is mainly obtained from stable carbon isotope compositions ordos basin is one of the largest natural gas provinces in china by means of examining the carbon isotope compositions of the ordos basin gases altered patterns of the isotopetype curves due to secondary cracking thermochemical sulphate reduction tsr and mixing of gases generated from different sources are recognized and discussed a typical carbon isotope type curve is nearly linear on the natural gas plot chung h m gormly j r squires r m 1988 origin of gaseous hydrocarbons in subsurface environments theoretical considerations of carbon isotope distribution chemical geology 71 97 103 our results show that the isotope type curve pattern of tsr and gas secondary cracking in coal is convex due to catalysis while the isotope type curve of gas secondary cracking in reservoirs is concave the natural gas of yulin suligemiao and wushenqi gas fields is coal derived gas both coal derived gas and mixed gas from oil and gas prone sources exist in the ordovician reservoirs of the jingbian gas field depending on the borehole locations in the ordovician carbonate reservoirs tsr is recorded but uncommon whereas secondary cracking in reservoirs is often observed 2007 elsevier ltd all rights reserved

composition and origin of natural gases accumulated in the polish and ukrainian parts of the carpathian region gaseous hydrocarbons noble gases carbon dioxide and nitrogen abstract ten natural gas samples associated and non associated with oil in the polish and ukrainian flysch carpathians and mesozoic basement of the carpathian foredeep were analysed for molecular and stable isotope compositions as follows 12 13c in ch4 c2h6 c3h8 and co2 1 2h in ch4 14 15n in n2 and 3 4he 20 21 22ne 36 38 40ar 84kr and 132xe in noble gases the gaseous hydrocarbons both in the silesian unit of the outer flysch carpathians and mesozoic basement are generally genetically related to thermogenic processes and occasionally to microbial carbon dioxide reduction these gases were mainly generated from mixed type ii iii kerogen during middle stage of the low temperature thermogenic processes gaseous hydrocarbons from starunia in the boryslav pokuttya unit were generated from type ii kerogen during middle stage of the low temperature thermogenic processes he is generally of crustal origin with more than 99 2 of radiogenic 4he but appreciable amount of 3he is probably derived from the upper mantle the 3he might have been derived from the pieniny klippen belt deep seated fault system or neogene and pleistocene andesitic and basaltic volcanism occurred in the eastern carpathian area nucleogenic 21ne and 22ne were analysed in all the samples the nucleogenic 21ne shows good correlation with radiogenic 4he with the production ratio of 4he 21ne 1 3 107 in the crust these isotopic values indicate a common source for these gases where both the nuclear reactions of decay and n are occurring concentrations of radiogenic 4he and 40ar and excess 21ne in the samples from the mesozoic basement are generally higher and more scattered compared with those in the silesian unit the larger concentrations of radiogenic and nucleogenic isotopes in the natural gases from the mesozoic basement is probably related to older geological formations than younger formations of the silesian unit carbon dioxide was generally generated during the thermal transformation of organic matter and occasionally during microbial processes nitrogen was mainly generated during thermal transformation of organic matter and also originated from atmosphere a least part of carbon dioxide and nitrogen may have been produced in crust

oil oil and oil source rock correlations in the carpathian foredeep and overthrust south east poland abstract the chemical composition of 35 crude oils and the extracts of potential source rock samples from south east poland were studied in detail by geochemical methods in order to understand their genetic relationships twenty six oils including three seep samples were collected from cretaceous to oligocene reservoirs within the carpathian overthrust nine oils originated from carboniferous to miocene reservoirs within the carpathian foredeep the rock samples studied were selected after rock eval pyrolysis screening of a large suite of samples and consist of one lower cretaceous sample and five oligocene menilite shale samples from three different outcrop locations all within the carpathian overthrust geochemical fingerprinting indicates at least two families of crude oils the first represented only by one oil has no specific characteristics except for a light carbon isotope composition the second family is characterized by the presence of 28 30 dinor hopane oleanane and a highly branched isoprenoid c25 alkane within this latter family four subfamilies were recognized a 19 oils having the aforementioned characteristics b seven oils similar to subfamily a but with a relatively high sulphur content c one oil with high abundance of higher plant derived triterpanes and d seven oils with abundant 28 30 dinor hopane although maturity influences the relative abundance of 28 30 dinor hopane it suggested that subfamilies a b and c had an initial low 28 30 dinor hopane content whereas subfamily d an initial high 28 30 dinor hopane content only one oil of subfamily a could potentially be a high maturity counterpart of subfamily d a palaeozoic source rock is suggested for the first family and the second family including the majority of the pils from the carpathian foredeep is most likely derived from the oligocene menilite shales an oil source rock relationship with the menilite shale is supported by the presence although not in all samples studied of 28 30 dinor hopane oleanane or its precursors and the highly branched isoprenoid alkane the strong facies variations observed within this shale gave rise to the different types of crude oils in the second family

molecular and isotopic compositions and origin of natural gases from cambrian and carboniferous lower permian reservoirs of the onshore polish baltic region natural gases from middle cambrian and carboniferous lower permian reservoirs of the onshore polish baltic region were studied for their molecular and stable isotope compositions the following gas species were analysed 12 13c in ch4 c2h6 c3h8 n c4h10 i c4h10 and co2 1 2h in ch4 14 15n in n2 and stable isotopes of all noble gases due to significantly different geological settings and genetic types of source rocks of eastern and western pomerania the molecular and isotopic compositions of natural gases of these two regions exhibit distinct differences hydrocarbon gases associated with oil accumulated in the middle cambrian reservoir of eastern pomerania were generated during low temperature thermogenic processes from a single source rock containing type ii kerogen at one phase of petroleum generation non associated hydrocarbon gases accumulated in the carboniferous mississippian and pennsylvanian lower permian rotliegend reservoirs of western pomerania originated during at least two phases of gas generation by thermogenic processes from mainly type iii kerogen and a small component of mixed type iii ii kerogen noble gases are in general heavily enriched in radiogenic and nucleogenic isotopes such as 4he 40ar and 21ne accumulated in the reservoirs weak contributions of mantle derived he and ne are observed radiogenic 4he 40ar ratios are higher than the average production rate ratio of about 5 for radiogenic 4he 40ar in crustal materials which might have been caused by a selective supply of 4he that is lighter than 40ar from crustal rocks or u th k ratio might be higher than the average in crustal block carbon dioxide from gases of both the western and eastern pomerania were mainly generated during thermogenic processes of transformation of organic matter although gases of western pomerania can contain an endogenic component molecular nitrogen from the eastern pomeranian natural gases was mainly generated during low temperature thermal transformation of organic matter and derived from nh3 and nh4 of crustal fluid whereas molecular nitrogen from western pomeranian natural gases contains a significant component from the destruction of organic matter at a higher maturity level which may have been caused by a high heat flux from the volcanic activity during late pennsylvanian early rotliegend ages and has a bigger component release from nh4 rich illites

sedimentology of upper ordovician silurian sequences on new world island newfoundland separate fault controlled basins discussion amott s interpretation of new world island nwi stratigraphy suggests that upper ordovician and silurian sedimentation took place in three distinct sedimentary basins that were bounded by synsedimentary faults the stratigraphic and sedimentologic data offer a significant contribution to nwi geology but in view of the geologic complexity of this area of the northern appalachians the paper would have benefitted by a presentation of paleocurrent data in rose diagrams or spherical projections rather than as azimuths by a discussion of how paleocurrent data were rotated to inferred pre deformational positions and by an addition of error bars showing uncertainties in age determinations of fossils

silurian deformation in eastern notre dame bay newfoundland eastern notre dame bay newfoundland is divided into five fault bounded terranes they are from north to south the twillingate terrane the chanceport terrane the new world island terrane the dildo run terrane and the port albert terrane the new world island terrane is characterized by fault repeated sequences of middle ordovician to early silurian turbiditic sandstones sansom formation and conglomerates goldson formation the chanceport terrane has a lower volcanic unit and an upper sedimentary unit consisting of red and green siltstones shales overlain by turdiditic sandstones this sequence is structurally overlain by a mafic and felsic volcanic unit the clastic sedimentary rocks of the chanceport new world island and port albert terranes best record the silurian deformation in the area silurian deformation is divided into two deformation events an early silurian d1 thrusting event and a late silurian d2 dextral ductile faulting event the early silurian joey s cove melange constrains th

collision along an irregular margin a regional plate tectonic interpretation of the canadian appalachians discussion stockmal et al recently presented a simple three dimensional plate tectonic model by which they attempted to explain the pre carboniferous evolution of the northern appalachians this model which in part follows the basic principles of the two stage collision model of colman sadd 1982 is mainiy based on the results of a marine seismic profile across northem newfoundland and on large scale geometrical considerations such models are useful because they provide geologists with a framework that can be tested against field data however in this case the existing geological data base in our opinion is incompatible with the model we will discuss the inconsistencies and present an altemative model the main thesis of the stockmal et al model is that the taconian and acadian orogenies are explained in terms of continuous southeastward subduction of iapetus oceanic lithosphere during the collision between the taconic magmatic arc and the irregular margin of north america the benioff zone clogged first in newfoundland and then in mainland canada the continuing convergence between the taconic arc and north america in newfoundland was then achieved by delamination of lithospheric mantle while b subduction continued between the taconic arc and north america in mainland canada evidence in support of this model includes the 300 400 km right hand offset of equivalent tectono stratigraphic zones between newfoundland and mainland canada and a difference in style and vergence of the acadian structures in newfoundland and new brunswick the idea of a diachronous collision is not a new one but the sense of diachronism remains unresolved see e g dallmey er 1977 clague et al 1981 lux 1986 considered the allochthonous ophiolites in the humber zone and argued in favour of a north to south diachronism his conclusion is consistent with the fact that the oldest fossil dated autochthonous flysch is younger in quebec than in newfoundland since there is no overstepping autochthonous cover in quebec stockmal et al argue that the timing of the final emplacement of the allochthons and the closure of iapetus is not well constrained there and they explain the acadian orogeny in mainiand canada as

determination of crustal fluid residence times using nucleogenic 39ar abstract argon 39 is a radioactive isotope of ar with a half life of 269 years there are two natural sources of 39 ar on earth cosmogenic production in the upper atmosphere and nucleogenic production in rocks cosmogenic 39 ar has been recognized as an ideal tracer for groundwater residence times and oceanic circulation nucleogenic 39 ar has generally been considered problematic for groundwater studies in this work we developed simple models for the evolution of 39 ar 40 ar ratios where 40 ar denotes radiogenic 40 ar produced in the model system in rocks and fluids in rocks both 39 ar and 40 ar are produced and a fraction of the 39 ar and 40 ar is released into the mobile fluid phase in both reservoirs 39 ar reaches production or supply decay equilibrium whereas 40 ar accumulates with time thereby the 39 ar 40 ar ratio in rocks and fluids generally decreases with time our models suggest that the co evolution of these two isotopes in rocks and fluids provides a new chronometer of fluid migration and reaction in the crust this chronometer is relevant to a much wider time range than that limited by radioactive decay of cosmogenic 39 ar i e 1400 years at the current detection limit of 3 modern atmospheric value the 39 ar 40 ar chronometer is applicable to estimating residence times of very old groundwater as well as for studying fluid rock interactions and fluid migration rates such as those occurring during co 2 sequestration and the formation of hydrocarbon reservoirs

redefinition of the wild bight group newfoundland implications for models of island arc evolution in the exploits subzone the wild bight group and correlative plutonic rocks of the south lake igneous complex comprise one of the accreted ordovician peri gondwanan oceanic terranes of the newfoundland appalachians recent field work and isotopic ages from the eastern wild bight group require that the stratigraphic sequence be redefined a package of bimodal volcanic rocks which forms the oldest part of the group and contains all of its volcanogenic massive sulphide deposits is redefined as the glovers harbour formation this formation is correlative with intra oceanic ophiolitic sequences elsewhere in the exploits subzone previous stratigraphic nomenclature for the upper wild bight group is largely retained although the lithological variation within and spatial distribution of the omega point seal bay brook and pennys brook formations are revised and the side harbour formation is included as part of the seal bay brook formation the upper wild bight group is interpreted to represent a second and distinct arc sequence

noble gases in crude oils from the paris basin france implications for the origin of fluids and constraints on oil water gas interactions in order to investigate the potential of noble gases to trace the dynamics of oil reservoirs we have analysed the abundance and isotopic composition of all noble gases he ne ar kr and xe in crude oils from the paris basin france using a new extraction and purification procedure the main oil reservoirs are presently located in the jurassic dogger limestone and in the triassic keuper sandstone but hydrocarbons originated from a common source rock formation located in the interbedded liassic sequence despite this common origin the abundance and isotopic ratios of the noble gases differ between the dogger and the keuper the isotopic compositions of kr and xe are indistinguishable from that of air 3he 4he ratios higher than those predicted from radiogenic production in the sediments or in the crust are attributed to the occurrence of mantle derived 3he in the basin each sedimentary sequence is characterised by well defined and homogeneous 21ne 22ne and 40ar 36ar ratios which average 0 0306 0 0008 and 312 10 for the dogger and 0 0367 0 0012 and 664 30 for the keuper respectively the main source of radiogenic noble gases appears to be the continental crust underlying the basin with possible regional contributions of noble gas isotopes produced in the sediments the helium and argon isotopic ratios of the dogger oils are very similar to those observed in geothermal waters flowing in the dogger aquifer throughout the basin demonstrating that noble gases in oils derive from associated groundwaters oil reservoirs in the paris basin therefore accumulate noble gases from wide regions of the continental crust through cross formational flow of groundwaters and subsequent partitioning into oil this observation implies that noble gases cannot be directly used to date oils but can provide time constraints if 1 water oil interactions are quantified and 2 the residence time as well as the noble gas characteristics of associated groundwaters are known oil water gas partitioning processes are well recorded in the fractionation of noble gas elemental abundance two distinct processes have been identified 1 accumulation of atmosphere derived ang and radiogenic noble gases both initially dissolved in groundwaters resulting in a positive correlation between absolute amount of ang and the extent of heavy noble gas fractionation and 2 subsequent fractional degassing resulting in a negative correlation between ang abundance and heavy noble gas fractionation degassing is particularly evident for the keuper oils and might have occurred in the reservoirs following hydrodynamic gas stripping the ang abundance in the dogger reservoirs requires that about one order of magnitude more water than presently observed has interacted with the oil given current estimates of the residence time for groundwaters in the dogger aquifer the duration of oil water interaction is in qualitative agreement with a palaeocene oligocene age for the major episode of secondary oil migration in the paris basin high xenon contents in keuper reservoirs suggest that they have experienced hydrodynamic interactions between flowing waters and oils for long time and that the trias might have reached hydrostatic condition only recently

mineral forming and diagenetic processes related to tertiary hydrocarbon seepage at the bohemian massif outer western carpathians interface evidence from the hrabůvka quarry moravia czech republic v lomu hrab vka situovanem p i hranici ceskeho masivu reprezentovan m zvrasn n mi spodnokarbonsk mi siliciklastiky kulmske facie a terciernim sedimentarnim pokryvem zapadnich karpat tvo enem spodnobadensk mi siliciklastiky a vapnit mi jily byl v geologickem zaznamu zjist n fosilni v v r uhlovodik v clanku jsou prezentovany mineralogicke izotopove a geochemicke udaje a take data ze studia fluidnich inkluzi ktere umo nily vyhodnotit genezi dan ch hornin il a jejich fluid

silurian extension in the upper connecticut valley united states and the origin of middle paleozoic basins in the quebec embayment pre silurian strata of the bronson hill arch bha in the upper connecticut valley nh vt are host to the latest ludlow comerford intrusive suite consisting east to west of a mafic dike swarm with sheeted dikes and an intrusive complex the rocks are mostly mafic but with compositions ranging from gabbro to leucocratic tonalite the suite is truncated on the west by the monroe fault a late acadian thrust that carries rocks of the bha westward over silurian devonian strata of the connecticut valley gaspetrough cvgt dikes intrude folded strata with a pre intrusion metamorphic fabric taconian but they experienced acadian deforma tion twenty fractions of zircon and baddeleyite from three sample sites of gabbro diorite spanning nearly 40 km yield a weighted 207 pb 206 pb age of 419 1m a greenschist facies dikes sampled over a strike distance of 35 km were tholeiitic basalts formed by partial melting of asthenospheric mantle with little or no influence from mantle or crustal lithosphere the dike chemistry is similar to mid ocean ridge within plate and back arc basin basalts parent magmas originated in the astheno sphere and were erupted through severely thinned lithosphere adjacent to the cvgt extensive middle paleozoic basins in the internides of the appalachian orogen are restricted to the quebec embayment of the laurentian rifted margin and include the cvgt and the central maine trough cmt separated from the bha by a silurian tectonic hinge the ne trending comerford intrusions parallel the cvgt cmt and the tectonic hinge and indicate nw se extension during post taconian convergence the irregular margins of composite laurentia and avalon permitted continued colli sion in newfoundland st lawrence promontory and coeval extension in the quebec embayment extension may be related to hinge retreat of the northwest directed brunswick subduction complex and rise of the asthenosphere following slab break off an alternative hypothesis is that the basins originated as pull apart basins between northwest trending left stepping sinistral strike slip faults along the southern flanks of the new york and st lawrence promontories

origin of gaseous hydrocarbons noble gases carbon dioxide and nitrogen in carboniferous and permian strata of the distal part of the polish basin geological and isotopic approach abstract sixteen natural gas samples collected from pennsylvanian and permian rotliegend and zechstein limestone strata of the distal part of the polish basin in wielkopolska and lower silesia were analysed for molecular composition and stable carbon isotope composition of hydrocarbons ch 4 c 2 h 6 c 3 h 8 n c 4 h 10 and i c 4 h 10 and co 2 stable hydrogen isotope composition of methane stable nitrogen isotope composition of n 2 and stable isotope composition of noble gases he ne ar kr and xe thirteen of analysed hydrocarbon gases reveal complete 13 c ch 4 13 c c 2 h 6 13 c c 3 h 8 and partial inversed isotopic trends from methane to propane thus they have a very complicated generation migration and accumulation history and range of their source rock horizons two source rock horizons occur ne from wolsztyn ridge they contain mixed types iii ii and ii iii kerogens of pennsylvanian age and mississippian and or devonian age respectively one source rock horizon occurs sw from wolsztyn ridge it contains type iii and mixed type iii ii kerogens of pennsylvanian age the kerogens in all source rock horizons generated gaseous hydrocarbons at two separate maturity stages about 0 5 to 0 8 in vitrinite reflectance scale at the first maturity stage and over 1 3 in vitrinite reflectance scale at the second maturity stage high concentrations of he in analysed gases are mostly a product of decay of u and th enriched in crustal materials a small contribution of he and ne of mantle origin to the gas reservoirs was inferred radiogenic 4 he 40 ar ratios are higher than the average production rate ratio of about 5 for crustal materials which might have been caused by a selective supply of lighter he through crustal rocks surrounding the gas reservoirs or higher u th k ratio than the crustal average co 2 from analysed gases was mainly generated during thermogenic processes of transformation of organic matter although some gases can contain components from endogenic processes and from thermal destruction of zechstein limestone and probably precambrian carbonates n 2 was mainly generated during thermal transformation of organic matter and had a large component released from nh 4 rich illites very high n 2 40 ar for the gases might be caused by accelerated thermogenic production of n 2 under the condition of high heat flux from volcanic activity at late pennsylvanian and early permian age deep seated faults mainly framing the wolsztyn ridge perform important role in migration and mixed in different proportions of noble gases originated from upper mantle and from mineralisation by radioactive minerals their fault surfaces and occurrence of pennsylvanian lower permian volcanites in crust as well as hydrocarbon gases co 2 and n 2 also from thermal destruction of nh 4 rich illites from gas generation kitchens of source rock horizons to the traps

fingerprinting coal derived gases from the uk abstract the large scale extraction of unconventional hydrocarbons in the united states has led to fears of methane contamination of shallow groundwaters differentiating between the deep gas released during extraction shale gas coal bed methane and underground coal gasification and natural shallow sourced methane is imperative for the monitoring and managing of environmental risks related to the extraction process here for the first time we present measurements of the major gas and stable and noble gas isotope composition of coal bed methane cbm from central scotland and coal mine methane cmm from central england uk the molecular c1 c2 c3 21 to 121 and stable isotope compositions 13cch4 39 5 to 51 1 dch4 163 to 238 indicate a thermogenic origin for the methane they are distinct from the majority of shallow sourced gases in uk both sample suites exhibit high he concentrations 338 to 2980 ppmv that are considerably above atmospheric and groundwater levels simple modelling shows that these high 4he concentrations cannot be solely derived from in situ production since coal deposition and hence the majority is derived from the surrounding crust the scottish cbm contains a resolvable mantle he ne and ar contribution that may originate from melts in the deep crust demonstrating the uk coals have acted as a store for deep volatiles for 10s of millions of years the high 4he in the coal derived gases has the potential to be used as a novel diagnostic fingerprint to track fugitive release of deep methane from future unconventional gas extraction operations in the uk

sources and mechanisms of formation of gaseous hydrocarbons in sedimentary rocks abstract accepted concepts of principal stages of hydrocarbon formation fail to satisfactorily explain the accumulation of supergiant gasfields in west siberia u s s r such as for example urengoy which comprise 30 of the proven gas reserves of the world a new mathematical model has been developed which applies the concept of activation energy distribution to the formation of gases characteristic differences in the molecular structure of humic and sapropelic source organic matter are expressed in different activation energy distributions the model allows the calculation of isotope values for different types of organic matter and their dependence on maturity application of the model to west siberia suggests that the supergiant gas accumulations in urengoy are more likely formed from terrestrial organic matter through thermochemical reactions at moderate depths and are not the result of either deep overmature or bacteriogenic processes the new mathematical model suggests that humic organic matter in general has a high methane generating capacity at comparably low maturities of organic matter equivalent to 0 5 0 7 on the vitrinite reflectance scale

oblique cleavage folds a critical discussion with examples from the canadian appalachians abstract examples of transected folds from three localities in notre dame bay north central newfoundland are described and analyzed the oblique relationship of cleavage and folds is the result of overprinting of the folds by the cleavage in two of the three localities and the result of overprinting of the cleavage by the folds in the third locality thus it is argued that transected folds need not form synchronously with the oblique cleavage an axial plane cleavage associated with the folds may be completely obliterated by the oblique cleavage or may never have existed the term oblique cleavage folds is introduced as a geometric term to describe folds with a cleavage oblique to their hinges transected fold models are generally based on the orientation of cleavage and folds with respect to the strain ellipsoids on the scale of the deforming zones or on the scale of layers of variable competence here we follow a different approach transected fold models and the geometry of oblique cleavage folds are discussed in terms of the progressive development of the folds and cleavage we assume no special relationships to strain oblique cleavage folds are most commonly reported from shear zones where the strain path is non coaxial and the deformation is progressive such zones produce overprinting relationships even where only one deformation event is involved and commonly have a long history of reactivation we suggest that the significance of this correlation is that transected folds are generally and perhaps always a product of overprinting the age of folds and cleavage however may be very similar and both may be a product of the same protracted deformation event thus in studying oblique cleavage folds the possibility that the cleavage is pre syn or post folding should be considered even where there is only one recognisable generation of both folds and cleavage

transects of the ancient and modern continental margins of eastern canada abstract rocks of the west flank of the northern appalachian orogen miogeocline record the history of the late precambrian early paleozoic passive continental margin of eastern north america the ancient margin was destroyed by ophiolite obduction and arc collision during the ordovician taconic orogeny the present sinuous form of the miogeocline is interpreted to reflect ancient promontories and re entrants of a previous orthogonal margin bounded by rifts and transforms four major terranes are recognized east of the miogeocline in newfoundland and nova scotia from west to east these are the dunnage gander avalon and meguma the dunnage and gander terranes were linked to the miogeocline during the middle ordovician taconian orogeny the avalon terrane arrived later possibly during the mid paleozoic acadian orogeny the meguma terrane of southern nova scotia had docked with the avalon terrane by carboniferous time the dunnage terrane contains arc volcanics which lie above an ophiolitic substrate the gander terrane comprises a thick sequence of clastic sedimentary rocks underlain by basement rocks with continental affinities it has been interpreted as a continental margin perhaps once on the eastern side of the paleozoic iapetus ocean the avalon terrane consists of belts of sedimentary and volcanic rocks which are probably underlain by grenvillian basement its tectonic affinities are unclear the meguma terrane comprises a thick sequence of sediments derived from the south east it is found only in southeastern atlantic canada the boundaries between terranes are compressional in the west and steep transcurrent faults in the east the surface extent of the geological terranes is grossly correlative with deep structural zones although no direct evidence exists for linking the two because most surface structures can be traced geophysically to only a few kilometres depth a striking feature of the deep crustal structure is a lower high velocity crustal layer beneath the dunnage and gander terranes the modern margin of atlantic canada developed by rifting and by transform motion between adjacent continents stretching and thinning of the lithosphere and the consequent production of basaltic magma that in places intrudes or underplates the thinned continental crust are the most likely processes responsible for the evolution of the modern margin these processes predict the observed deep sedimentary basins along the margin the thinning of continental crust and the high seismic velocities found within the ocean continent transition zones rifting adjacent to nova scotia began in late triassic early jurassic time between the present african and north american plates these plate motions are also responsible for the major transform margin south of the grand banks separation between iberia and the eastern grand banks occurred in mid cretaceous time before the late cretaceous opening of the labrador sea while the rifted segments of the margin exhibit deep sedimentary basins and thinned continental crust the grand banks transform segment is characterized by a sharp transition zone and a relatively thin sediment cover numerous volcanic seamounts are built on the ocean crust adjacent to this transform segment mimicry of paleozoic promontories and re entrants by modern rift and transform margin segments the location of mesozoic sedimentary basins on ancestral appalachian structures and the reactivation and propagation of major precambrian and paleozoic structural boundaries during the latest phase of ocean opening attest to ancestral controls of the modern margins the rift phase of both the ancient and modern passive margins is characterized by volcanism mafic dike intrusion and by the development of basins filled with clastic sediments the drift phase of both the ancient margin and the present nova scotia margin is marked by a change in sedimentary environment such that carbonates replaced the rift phase clastic sediments two of the markers used to delineate the ancient ocean continent transition zone carbonate banks and steep gravity anomaly gradients should be used with caution as the modern analogs of these markers may lie 100 km or more of this transition zone furthermore it is naive to view the ancient transition as simple and narrow for the modern margins exhibits complex transition zones between 30 and 300 km wide in general the evolution of the ancient and modern passive margins appear to be remarkably similar predictably closing the present atlantic will mimic the evolution of the appalachian orogen

synthesis of palaeozoic deformational events and terrane accretion in the canadian appalachians plate tectonic theory predicts that most deformation is associated with subduction and terrane accretion with some deformation associated with transform transcurrent movements deformation associated with subduction varies between two end members 1 where the tectonic regime is dominated by subduction of oceanic lithosphere containing small terranes a narrow surface zone of accretionary deformation along the subduction zone starts diachronously on the subducting plate at the trench as material is transferred from the subducting plate to the over riding plate and 2 where continent continent collision is occurring a wide surface zone of accretionary deformation starts synchronously or with limited diachronism palaeozoic deformational events in the canadian appalachians correspond to narrow diachronous events in the ordovician and silurian whereas devonian carboniferous and permian deformational events are widespread and broadly synchronous along the western side of the canadian appalachians the taconian deformational event starts diachronously throughout the ordovician and corresponds to the north north west accretion of the notre dame ascot weedon st victor and various ophiolitic massifs volcanic arc and peri arc terranes over cratonic north america within the eastern half of the central mobile belt the late cambrian early ordovician penobscotian deformational event corresponds to the south easterly accretion of the exploits subzone various volcanic are and peri arc terranes over the gander zone continental rise in the centre of the orogen the late ordovician silurian beothukan deformational event corresponds to the south easterly accretion of the notre dame over the exploits gander subzones along the south eastern side of the central mobile belt the silurian ganderian deformational event corresponds to the north north east sinistral transcurrent accretion of the avalon composite terrane microcontinent over the gander exploits zones along the south eastern half of the orogen the late silurian middle devonian acadian deformation event corresponds to the westerly accretion of the meguma terrane intradeep or continental rise over the avalon composite terrane affecting the entire orogen the late devonian carboniferous and permian acadian alleghanian deformational events correspond to the east west convergence between laurentia and gondwana continent continent collision

regional groundwater focusing of nitrogen and noble gases into the hugoton panhandle giant gas field usa the hugoton panhandle giant gas field located across sw kansas and the texas and oklahoma panhandles in the usa is the case type example of high nitrogen concentrations in a natural gas being linked with high helium concentrations we collected 31 samples from producing wells in a north south traverse of the 350 km long field the samples reflect the previously observed north south change in 4he n2 with values changing from 0 020 to 0 049 respectively 3he 4he 21ne 22ne and 40ar 36ar vary between 0 14 0 25 ra 0 0373 0 0508 and 818 1156 respectively and are caused by quantifiable contributions from mantle crustal and atmosphere derived sources the atmosphere derived 20ne 36ar ratios are indistinguishable from groundwater values the crustal 4he 21ne and 4he 40ar ratios show a 60 excess of 4he compared to predicted production ratios in the crust and are typical of noble gases released from the shallow crust the mantle 3he n2 and groundwater recharge 36ar n2 ratios enable us to rule out significant magmatic or atmosphere contributions to the gas field n2 which is dominantly crustal in origin correlated 20ne n2 and 4he n2 shows mixing between two distinct crustal n2 components one n2 component n2 is associated with the crustal 4he and groundwater derived 20ne and the other with no resolvable noble gas contribution measured 15nn2 values vary from 2 7 to 9 4 the n2 and non he associated n2 endmembers are inferred to have 15nn2 3 and 13 and contribute from between 25 60 and 75 40 of the nitrogen respectively the non he associated nitrogen is probably derived from relatively mature organic matter in the sedimentary column the 15nn2 value is not compatible with a crystalline or high grade metamorphic source and similar to the 4he is inferred to be from a shallow or low metamorphic grade source rock 4he mass balance requires a regional crustal source its association with significant magmatic 3he pointing to a tectonically active source to the west of the hugoton system the volume of groundwater required to source the 20ne in the gas field demonstrates the viability of the groundwater system in providing the collection transport and focusing mechanism for the 4he and n2 the n2 20ne ratio shows that the n2 transport must be in the aqueous phase and that the degassing mechanism is probably contact between the regional groundwater system and the preexisting reservoir hydrocarbon gas phase

oil source rock correlations in the polish flysch carpathians and mesozoic basement and organic facies of the oligocene menilite shales insights from hydrous pyrolysis experiments the oligocene menilite shales in the study area in the polish flysch carpathians are organic rich and contain varying mixtures of type ii type iis and type iii kerogen the kerogens are thermally immature to marginally mature based on atomic h c ratios and rock eval data this study defined three organic facies i e sedimentary strata with differing hydrocarbon generation potentials due to varying types and concentrations of organic matter these facies correspond to the silesian unit and the eastern and western portions of the skole unit analysis of oils generated by hydrous pyrolysis of outcrop samples of menilite shales demonstrates that natural crude oils reservoired in the flysch sediments appear to have been generated from the menilite shales natural oils reservoired in the mesozoic basement of the carpathian foredeep appear to be predominantly derived and migrated from menilite shales with a minor contribution from at least one other source rock most probably within middle jurassic strata definition of organic facies may have been influenced by the heterogeneous distribution of suitable menilite shales outcrops and producing wells and subsequent sample selection during the analytical phases of the study

composition and origin of coalbed gases in the lower silesian basin southwest poland abstract coalbed gases in the lower silesian coal basin lscb of poland are highly variable in both their molecular and stable isotope compositions geochemical indices and stable isotope ratios vary within the following ranges hydrocarbon chc index chc ch4 c2h6 c3h8 from 1 1 to 5825 wet gas c2 index c2 c2h6 c3h8 c4h10 c5h12 ch4 c2h6 c3h8 c4h10 c5h12 100 from 0 0 to 48 3 co2 ch4 cdmi index cdmi co2 co2 ch4 100 from 0 1 to 99 9 13c ch4 from 66 1 to 24 6 d ch4 from 266 to 117 13c c2h6 from 27 8 to 22 8 and 13c co2 from 26 6 to 16 8 isotopic studies reveal the presence of 3 genetic types of natural gases thermogenic ch4 higher gaseous hydrocarbons and co2 endogenic co2 and microbial ch4 and co2 thermogenic gases resulted from coalification processes which were probably completed by late carboniferous and early permian time endogenic co2 migrated along the deep seated faults from upper mantle and or magma chambers minor volumes of microbial ch4 and co2 occur at shallow depths close to the abandoned mine workings late stage microbial processes have commenced in the upper cretaceous and are probably active at present however depth related isotopic fractionation which has resulted from physical and physicochemical e g diffusion and adsorption desorption processes during gas migration cannot be neglected the strongest rock and gas outbursts occur only in those parts of coal deposits of the lscb which are dominated by large amounts of endogenic co2

origin and secondary processes in petroleum in the eastern part of the polish outer carpathians a geochemical study of crude oil and natural gas from producing wells and seeps within the lower cretaceous oligocene sandstone reservoirs of the most eastern part of the polish outer carpathians was conducted for the evaluation of their origin migration pathways and the effects of secondary processes biodegradation water washing and evaporative fractionation the petroleum was generated from mixed marine terrigenous organic matter type ii iii kerogen occurring mostly in oligocene menilite beds in the silesian and skole nappes shales within upper cretaceous palaeocene istebna and lower cretaceous ve ovice lgota and spas beds are considered as an additional source of hydrocarbons mainly gaseous biodegradation processes were recorded in numerous oils especially occurring in seeps but the extent of these processes is not severe because steranes and terpanes were not affected all oils are more or less water washed while the evaporative fractionation processes are developed only on a minimal scale the natural gases are primarily of thermogenic origin usually co genetic with oil and often contain components of secondary microbial degradation of both oil and natural gas 13c enriched co2 and 13c depleted ch4 gases with the highest microbial methane contribution have been recorded in petroleum accumulated in dwernik and odyna fields

southwest new world island stratigraphy new fossil data new implications for the history of the central mobile belt newfoundland the identification of fossils from 16 new localities on southwestern new world island has resulted in the refinement and simplification of local stratigraphy and in the correlation of rock units across an intensely deformed area complex stratigraphic classifications of earlier workers are replaced by a simpler scheme consisting of four formations the summerford formation oldest rogers cove formation sansom formation and goldson formation mclange units are fault related and cannot be included in the stratigraphy fossil and lithological data provided here confirm previous indications that the rocks of the summerford formation are the remains of a long lived volcanic island complex this complex is overlain by a markedly diachronous coarsening upwards sequence of marine clastic sediments now represented by the rogers cove sansom and goldson formations the new stratigraphic data combined with structural evidence indicate that the stratigraphy is repeated across several bedding parallel faults significant diachroneity of formation boundaries and the absence of syndepositional high angle faults suggest deposition in one large rnid paleozoic basin rather than in a number of small dynamic basins

progressive folding and foliation development in a sheared coticule bearing phyllite abstract an evolutionary sequence of fold and foliation development interpreted to be the result of a single progressive deformation is seen in exposures of strongly sheared phyllite and coticule 10 km south of the e w trending chedabucto fault in the meguma terrane of nova scotia canada transposition sensu sander at mesoscopic and microscopic scales is fundamental to this development as are fold hinge rotation and migration the transposition process is cyclic with folds of layering and foliation developing rotating and being refolded fold hinges and axial surfaces repeatedly tend towards stable end orientations but do not reach them due to the cyclic transposition process the foliation is a steady state feature continually reconstituted by microscale transposition and dynamic recrystallization several important consequences of these contemporaneous processes are 1 geometrical relationships between folds and foliation are variable in the same outcrop even though both developed synchronously and many folds have the geometrical relationships of cleavage transected folds 2 the foliation is transient in orientation and therefore cannot track the xy principal plane of total finite strain and 3 fold hinge migration may be a common process especially in deformations involving a large component of simple shearing the observed relationships may be applicable to study of fold and foliation development in orogenic belts in general

correlation of carbon dioxide abundance with temperature in clastic hydrocarbon reservoirs relationship to inorganic chemical equilibrium the mol co2 of gas reservoired in sandstones tends to increase with increasing temperature along both the us gulf coast and the norwegian continental shelf each of these provinces displays identical linear correlations between temperature and the log of the partial pressure of co2 i e pco2 in the reservoir fluid that is the product of the mol co2 the reservoir pressure this correlation is the same both in gulf coast reservoirs younger than 17 ma and in norwegian reservoirs of jurassic to triassic age 144 245 ma indicating that it is not dependent on reaction kinetics norwegian shelf data indicate that the same correlation also applies for gas condensate and oil reservoirs we suggest that the log pco2versus temperature correlation is the result of inorganic chemical equilibria between feldspar clay and carbonate minerals a trend of decreasing ph with increasing temperature is fixed by equilibria between aluminosilicate minerals feldspar kaolinite at lower temperatures followed by various reactions between kaolinite illite chlorite and feldspar as temperatures exceed 110 140 c responding to the ph set by the aluminosilicate system co2 activity in the formation water and thereby co2 partial pressure in any gas phase present is controlled by equilibrium with carbonate minerals this model predicts that co2 released by organic maturation will in general result in precipitation of carbonate minerals below 100 120 c and that there should be widespread carbonate dissolution at higher temperatures

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

quantification of co2 generation in sedimentary basins through carbonate clays reactions with uncertain thermodynamic parameters abstract we develop a methodological framework and mathematical formulation which yields estimates of the uncertainty associated with the amounts of co 2 generated by carbonate clays reactions ccr in large scale subsurface systems to assist characterization of the main features of this geochemical process our approach couples a one dimensional compaction model providing the dynamics of the evolution of porosity temperature and pressure along the vertical direction with a chemical model able to quantify the partial pressure of co 2 resulting from minerals and pore water interaction the modeling framework we propose allows i estimating the depth at which the source of gases is located and ii quantifying the amount of co 2 generated based on the mineralogy of the sediments involved in the basin formation process a distinctive objective of the study is the quantification of the way the uncertainty affecting chemical equilibrium constants propagates to model outputs i e the flux of co 2 these parameters are considered as key sources of uncertainty in our modeling approach because temperature and pressure distributions associated with deep burial depths typically fall outside the range of validity of commonly employed geochemical databases and typically used geochemical software we also analyze the impact of the relative abundancy of primary phases in the sediments on the activation of ccr processes as a test bed we consider a computational study where pressure and temperature conditions are representative of those observed in real sedimentary formation our results are conducive to the probabilistic assessment of i the characteristic pressure and temperature at which ccr leads to generation of co 2 in sedimentary systems ii the order of magnitude of the co 2 generation rate that can be associated with ccr processes

distribution of methane and carbon dioxide concentrations in the near surface zone and their genetic characterization at the abandoned nowa ruda coal mine lower silesian coal basin sw poland abstract the closure of hard coal mines in the lower silesian coal basin sw poland resulted in migration of coal bed gases mostly methane and carbon dioxide towards the surface the gases were driven out by rising groundwater table in the pennsylvanian aquifer so called water piston effect because such migration may be a hazard for inhabitants living in the post mining lands a surface geochemical survey was carried out in the area of the closed nowa ruda hard coal mine the research aimed at i evaluating the distribution of methane and carbon dioxide concentrations in the near surface zone ii determining the genetic characteristics of soil gases and iii comparing their characteristics with that of coal bed gases the surface geochemical survey included sampling of soil gases and chromatographic analyses of samples for methane and carbon dioxide concentrations and for stable carbon isotope composition in samples of increased methane and carbon dioxide concentrations samples were collected along 8 sampling lines located in the mining fields piast slupiec and waclaw in total 390 soil gas samples were collected from 1 2 m depth maximum methane and carbon dioxide concentrations were 7 8 and 5 8 vol respectively almost all methane encountered in the analyzed samples of soil gases are of microbial origin and were generated during recent anaerobic processes in the near surface zone high concentration of carbon dioxide was generated by aerobic biodegradation of organic matter in abandoned mines moreover carbon dioxide was originated during the near surface oxidation of methane only sometimes insignificant thermogenic component of coal bed methane and carbon dioxide which migrated to near surface zone from pennsylvanian coal bed strata occurs moreover an insignificant component of endogenic carbon dioxide also migrated though the faults from deep seated volcanic chambers and or even from upper mantle in the piast mining field the results of our research revealed that the changes of soils gas concentrations in the slupiec field do not indicate water piston effect the highest state of gas emergency by inflow of deep gases to near surface zone could take place in the years 2008 2010 therefore much later than the near surface measurement sessions in 2004 in the piast field a relatively high number of anomalous concentrations of methane and carbon dioxide were measured such values results from degassing of groundwaters the table of which stabilized within the pennsylvanian aquifer in 2000 gases migrated towards the surface along the fracture systems and faults particularly along the main and the great faults a great number of anomalously high carbon dioxide concentrations were measured in the waclaw field which is an effect of groundwater table stabilization within the pennsylvanian rocks carbon dioxide migrates towards the surface along the bedding planes of pennsylvanian coal bearing strata and along the linings of remediated waclaw and wanda shafts the highest state of gas emergency by inflow of deep gases to near surface zone caused by the uprising of pennsylvanian water table piston effect could take place in piast mining field in the years 1998 2000 and in waclaw mining field in the years 1978 1980 therefore much earlier than the near surface measurement sessions in 2004

carbon dioxide in clastic rocks and silicate hydrolysis the amount of carbon dioxide in clastic rocks in sedimentary basins increases with depth organic matter dissolved organic species and dissolution of carbonate minerals have been suggested as sources of co sub 2 which increases in abundance with depth and temperature isotopic compositions of aqueous hco sub 3 sup minus gaseous co sub 2 and calcite from conventional hydrocarbon wells and steam assisted recovery of heavy oil suggest that calcite or other carbonate minerals are the source of co sub 2 particularly at higher temperatures detailed examination of the stability of diagenetic minerals such as kaolinite smectite and analcime among others relative to the coexisting waters indicates that silicate hydrolysis is the driving force for dissolution of carbonate minerals and the ultimate source of abundant co sub 2 in clastic rocks in diagenetic environments at temperatures over approximately 100 c

geochemical characteristics and origins of natural gas in the zhu iii sub basin pearl river mouth basin china abstract the zhu iii sub basin is an important petroliferous region in the south china sea where hydrocarbon distribution shows strong heterogeneity with oil primary produced from the wenchang b depression and gases from the wenchang a depression however a mixture of oil and gases are produced from the surrounding qionghai and shenhu uplifts the origin generation history and migration pathway of oil have been intensively studied but no study have been done directly on the gas which restricts future petroleum exploration in this study natural gas molecular compositions were measured on 46 samples stable carbon isotopic composition were measured on 39 samples and light hydrocarbon composition were measured on 30 samples results indicate that natural gases in the zhu iii sub basin are mainly composed of hydrocarbon gases with abundant co2 and n2 the hydrocarbon gases are all thermogenic gases which are mainly derived from the oligocene enping formation e3e 35 30 ma the contribution of the eocene wenchang formation e2w 56 35 ma to natural gases increases from the wenchang a depression to the south boundary fault sbf and surrounding uplifts this is caused by the early generated natural gases with more contribution from the e2w and dissolved in oils that migrated to the surrounding qionghai and shenhu uplifts natural gases and oil in the surrounding uplifts and near the sbf therefore avoided secondary cracking due to the high gas migration rate through the sbf and lateral sandstone carrier beds whereas natural gases in the wenchang a depression mainly originated from the secondary cracking of oil the equivalent vitrinite reflectance values of source rocks when the natural gases were generated varied from 0 6 to 1 5 based on carbon isotope differences between hydrocarbons indicating mature to high mature stage co2 with abundance less than 10 mainly originated from organic matter decomposition co2 with abundance more than 15 was sourced from the deep mantle and crust and mainly concentrated in the deep layers near the sbf which cuts into the basement n2 is probably the product of in situ reservoir alteration such as biodegradation in shallower layers our study on the geochemical characteristics and origins of the natural gas will enable a better understanding of petroleum system in the zhu iii sub basin and provide theoretical basis for optimizing future petroleum exploration strategy detailed study on shallow layers in the qionghai and shenhu uplifts and deep layers near the sbf are needed because exploration risks are relatively high in these plays

diagenetic source of fluids causing the hydrothermal alteration of teschenites in the silesian unit outer western carpathians czech republic petroleum bearing vein mineralization from the střibrnik site calcite pyrite veinlets containing a small amount of quartz chlorite sphalerite and marcasite occur in teschenite which is situated within the lower cretaceous flysch siliciclastics of the silesian unit fluid inclusion study demonstrated the presence of a heterogeneous mixture of a low salinity aqueous solution and mature methane rich petroleum during precipitation of calcite and quartz the 13c values of methane and dissolved carbonate 34s values of pyrite and 18o values of parent hydrothermal solutions are all consistent with the external source of the fluid phase derived from diagenetically modified flysch sediments the vein formation occurred during an increase in both temperature from 80 c to 220 c and pressure 100 700 bar the observed discrepancy between the maximum fluid temperature and the regional burial temperature together with fluctuations in petroleum density and significant variations in chemical and isotopic compositions of fluids are interpreted in terms of episodic tectonically induced generation of the fluid phase related to deeper burial the observed ree patterns of hydrothermal calcite and pyrite can be attributed to increased concentrations of organic ligands in the fluid phase and or involvement of sorption desorption processes

crustal profiles of active continental collisional belt czechoslovak deep seismic reflection profiling in the west carpathians summary czechoslovak deep seismic reflection profiles across the west carpathiam the first in the alpine himalayan belt and surface geological data suggest that the passive margin of the eurasian plate was obliquely overriden by the upper carpatho pannonian plate during the end of the krosno sea subduction some 17 14 ma ago the following period was dominated by slight oblique continental collision transpression and transtension of the west carpathian east alpine continental material escaping from the east alpine collision zone and eurasian brunovistulic passive margin crustal shortening in the north was accommodated by significant northerly dipping backthrusting and crustal thickening backthrusting is clearly observable on deep seismic lines 2t and 3t different subsidence features are present on the deep seismic line 3t there are active pull apart graben in the vienna basin mid miocene 16 10 ma low angle normal faulting in the danube basin and there is a normal simple shear zone offsetting the moho boundary beneath the danube basin

composition and origin of coalbed gases in the upper silesian and lublin basins poland abstract coalbed gases in the upper silesian coal basin uscb are highly variable in molecular and stable isotope composition geochemical indices and stable isotope ratios for coalbed gases from uscb vary within the following ranges ch4 c2h6 c3h8 hydrocarbon index from 122 to more than 10 000 cdmi carbon dioxide methane index cdmi co2 co2 ch4 100 from 0 0 to 21 0 13c ch4 from 79 9 to 44 5 d ch4 from 202 to 153 13c c2h6 from 24 6 to 22 3 13c c3h8 24 7 one sample and 13c co2 from 27 2 to 2 8 only two coalbed gases were collected from the lublin coal basin lcb geochemical indices and stable isotope ratios for these samples show the following values hydrocarbon index more than 10 000 cdmi 4 3 and 34 6 13c ch4 67 3 and 52 5 d ch4 201 one sample and 13c co2 13 7 and 11 9 methane higher gaseous hydrocarbons c2 to c5 and carbon dioxide occurring in the coalbed gases in both the uscb and the lcb were generated during the bituminous stage of the coalification process and probably during microbial reduction of carbon dioxide however depth related isotopic fractionation which has resulted from physical e g diffusion and adsorption desorption processes during gas migration cannot be neglected in both basins the coalification process lasted no longer than several ma and was completed at the end of the variscan orogeny at the turn of carboniferous and permian

helium and neon isotope systematics in carbon dioxide rich and hydrocarbon rich gas reservoirs the isotopic compositions and elemental abundances of helium and neon were measured in three natural gas reservoirs in the pannonian sedimentary basin of hungary kismarja a co2 rich reservoir and szeghalom south and szeghalom north both ch4 dominated reservoirs are located on topographic basement highs close to the derecske sub basin in eastern hungary mantle derived neon has been identified in mixed ch4 co2 reservoirs in the vienna basin austria this study establishes that mantle derived neon and helium are a characteristic feature of gas reservoirs throughout the neogene extensional basins of hungary and austria regardless of the dominant active gas composition 3he4he ratios within these samples are attributable to a two component mixing between mantlederived and crustal radiogenic helium the percent contribution of mantle derived 4he varies from 2 3 to 17 in contrast neon isotopic ratios indicate that the gases contain a significant component of atmosphere derived neon in addition to the mantle and crustal derived components 20ne 21ne and 22ne abundances can be corrected for this atmospheric contribution calculated contributions of mantle and crustal derived 21ne are between 3 6 21 and 1 37 respectively 20ne22nec and 21ne22nec ratios derived for these atmosphere corrected components correlate with measured r ra values and plot along a single two component mixing line between crustal and mantle isotopic endmembers this is consistent with a model in which simple mixing occurs between crustal and mantle endmembers with fixed he ne ratios the mixing line is defined by a hyperbolic constant k where k 4he22ne rad 4 he22ne mntl with a mean value of 67 3 11 8 based on estimated values of 0 47 for 21ne22nerad and 1 62 0 03 107 for 4he21ne rad kennedy et al 1990 values of 7 61 106 for he22ne rad and 11 3 104 for 4he22ne mntl can be calculated for the pannonian basin gases this 4he22ne mntl value is indistinguishable within error from the value of 8 04 104 calculated for rare gases in natural gases from the vienna basin these results clearly establish that the continental expression of mantle derived rare gases in continental extensional systems in austria and hungary is distinct and consistently different from that of gases discharging at the spreading ridges where best estimates of 4he22ne mntl are 8 1 11 3 times higher 9 10 105 staudacher et al 1989 given the remarkable agreement in the continental expression of mantle derived gases throughout the pannonian and vienna basins it is difficult to attribute the observed neon enrichment helium depletion with respect to morb gases to fractionation related to lithospheric transport processes kinetic fraction ation processes involved in transport through the crust might be expected to produce a much wider variation in the observed he ne elemental ratios the consistent order of magnitude neon enrichment observed throughout these gas fields instead implies that mantle derived fluids in these continental extensional systems may be sourced in a region of the mantle distinct from that supplying the mid ocean spreading ridges

noble gas isotopic variations and geological implication of longmaxi shale gas in sichuan basin china the large difference in carbon isotopic compositions of shale gases from the lower silurian longmaxi formation marine organic rich shales between changning and weiyuan areas in sichuan basin china is a still debate issue in this study 30 produced shale gas samples were collected during 3 years production period and analyzed for noble gas he ne and ar abundances and isotopic compositions to reveal the origin and variation causes of shale gases the results show that the longmaxi shale gases show low 3he 4he and 20ne 22ne and varied but high 21ne 22ne and 40ar 36ar ratios the weiyuan shale gases are characterized by low 3he 4he high 40ar 36ar ratios and varied 4he and 40ar abundances and a large increase in 40ar contents and a slight decrease in 40ar 36ar ratios display during 3 years shale gas production period from jan 2014 to jun 2016 whereas the changning shale gases are characterized by low and varied 3he 4he ratios and high 4he and 40ar abundances and small fluctuations in 40ar contents and 40ar 36ar ratios exhibit during 3 years production period in addition the shale gases produced from horizontal wells in the weiyuan area possessed higher 40ar and 40ar 36ar ratio than that those from vertical wells at same well site the noble gas isotopic compositions and variation of longmaxi shale gases suggested that they are originated mainly from crust air saturated fluid asf and radiogenic accumulation the variation of 40ar and 4he contents during shale gas production mainly reflects the degree of shale gas source supply from mineral matrix to fracture network and the greater increases in 40ar and 4he contents with production time show less abundant shale gas supply therefore the increase trend of 40ar contents with shale gas production time in the weiyuan area during 3 years production period possibly suggests less adequate shale gas supply in contrast the uniform or nearly constant of 40ar content through production time in the changing area indicates abundant supply of shale gas sources from mineral matrix resulting in less production decline variation in 4he and 40ar contents through shale gas production time could be sensitive indicators of abundant or depleted shale gas source supply

characteristics of molecular nitrogen generation from overmature black shales in south china preliminary implications from pyrolysis experiments abstract high content of molecular nitrogen n2 is one of the natural gas exploration risks in petroliferous basins where black shales act as source rocks of either hydrocarbon gas or molecular nitrogen in this study two overmature and one low maturity shale samples and their kerogens were investigated to determine the generation characteristics of molecular nitrogen as well as methane and the differences in the release processes of inorganic nitrogen fixed in ammonium bearing minerals and organic nitrogen bound in kerogen the results illustrate that with increasing pyrolysis temperature the yield of methane first increases and then decreases with an inflection temperature of 650 c eqvro 3 4 whereas the yield of molecular nitrogen shows a continuous increase throughout the pyrolysis experiment the molecular nitrogen during the stage of methane generation i e eqvro 3 4 the results also reveal that at the experimental maxima of thermal maturity eqvro 4 9 the generation potential of inorganic molecular nitrogen mg g ninorg is much lower than that of organic molecular nitrogen mg g norg indicating that in our experiments the organic nitrogen in kerogen is more easily to be converted into molecular nitrogen than the inorganic nitrogen in ammonium bearing minerals all these results indicate that molecular nitrogen content in shale gas may change dramatically during thermal evolution and source rocks with exceptionally high maturity and high abundance of organic nitrogen likely lead to a high molecular nitrogen risk particularly in regions of poor preservation conditions of shale gas which may be the main reasons for the high molecular nitrogen content in the lower cambrian shale gas in south china

origin and migration of oil and natural gas in the western part of the ukrainian outer carpathians geochemical and geological approach abstract we established the generation and migration processes as well as the influence of secondary processes of oil and natural gas accumulated in lower cretaceous oligocene strata of the western part of the ukrainian outer carpathians based on the results of organic geochemical analyses of oil and natural gas related to the geological setting and source organic matter the oligocene menilite beds from the boryslav pokuttya nappe are the main source rock for oil and natural gas accumulated in the fields of the boryslav pokuttya and skiba nappes co sourcing of oils and natural gas accumulated in the skiba nappe in the study area by both menilite and spas beds of this nappe cannot be excluded in some cases e g novoshidnytsya field oil and natural gas originated within the oligocene menilite beds of the boryslav pokuttya nappe migrated through thrusts and fissure zones and accumulated in the lower cretaceous reservoirs of the skiba nappe oil from small vovche field and pohar seep of the krosno nappe was generated by menilite source rocks of this tectonic unit and migrated to the traps sporadically oils underwent secondary processes mainly biodegradation and occasionally water washing hydrocarbon gases and carbon dioxide were generated mainly during low temperature thermogenic processes from type ii kerogen and partly during the microbial co2 reduction process only natural gas from the mala volosyanka oil and gas seep of the krosno nappe was documented to have undergone biodegradation

organic geochemical study and genetic correlation of natural gas oil and menilite source rocks in the area between san and stryi rivers polish and ukrainian carpathians abstract we studied the source rocks and petroleum accumulations in the carpathian mountains of the polish ukrainian border area between the san and stryi rivers a total of 108 oligocene menilite formation rock samples 12 oil and 15 gas samples accumulated in the oligocene reservoirs and one oil and gas sample from an upper cretaceous reservoir were analysed the aim of this study was to evaluate the petroleum potential of the menilite formation in this area and to evaluate potential genetic correlations between source rock and petroleum the menilite formation represents a prolific source rock with toc content ranging from 2 to 7 wt locally exceeding 20 wt algal type ii and mixed type ii iii kerogens dominate but sometimes type iii kerogen and rarely type i kerogen occur thermal maturity of the oligocene menilite formation increases from outer to inner tectonic units from the immature in the boryslav pokuttya and skole units to the overmature in the southern parts of silesian and dukla units as a consequence petroleum potential decreases in the same order geochemical analyses reveal that oil and gas generation and migration processes within the carpathian flysch succession are complicated all analysed oils were generated from the menilite formation during early and peak stages of the oil window associated gas is of low temperature thermogenic origin sometimes containing an admixture of microbial gas high temperature thermogenic gas occurs only in the polish part of the silesian unit

structural interpretation of the eastern notre dame bay area newfoundland regional post middle silurian thrusting and asymmetrical folding the structural geometry of the eastern notre dame bay area is that of an allochthonous sequence related to f1 thrusting and folding folded by f2 asymmetrical folds and offset by f3 related high angle faults f1 folds are isoclinal and commonly intrafolial f2 folds are asymmetrical generally tight with axial surfaces that dip 30 85 southeast the prominent northeast striking penetrative cleavage s2 is axial planar to f2 folds f3 structures include chevron folds box folds kink bands and local s3 crenulation cleavage f1 folds are overprinted by f2 folds producing coaxial and mushroom interference patterns this and the subhorizontal enveloping surface of f2 indicate that f1 folds were recumbent prior to f2 a zone of f1 folds separating silurian turbidites from subaerial volcanics on the port albert peninsula suggests f1 was related to macroscopic thrusting as does the association of f1 with mesoscopic thrust faults f2 folds are the most obvious structures in the area macroscopic examples in

timing and spatial distribution of deformation in the newfoundland appalachians a multi stage collision history van der plmjm b a 1987 timing and spatial distribution of deformation in the newfoundland appalachians a multi stage collision history in h j zwart m martens i van der molen c w passchier c spiers and r l m vissers editors tectonic and structural processes on a macro meso and micro scale tectonophysics 135 15 24 the newfoundland appalachians have been interpreted as an area where lower paleozoic plate convergence culminated in collision between an ordovician volcanic chain and the north american craton in middle ordovician times closure of the intervening proto atlantic iapetus ocean was considered incomplete subsequent deformation gave rise to regional folding and faulting recent studies in the newfoundland dunnage zone have revealed that the deformation history is far more complex than previously recognized large scale thrusting folding and faulting occurred in silurian devonian times furthermore it has been suggested that the dunnage zone is an allochthonous terrane underlain by dominantly continental crust rather than representing remnants of a rooted ocean basin in view of these results a revision of tectonic scenarios and zonal subdivision is warranted and a multi stage collision history will be discussed with emphasis on the spatial distribution and significance of silurian devonian deformation in central newfoundland subduction in lower paleozoic times gave rise to the formation of a volcanic terrane concurrently to the southeast a marginal sea was formed mariana type subduction in middle ordovician times the volcanic terrane collided with the north american craton first stage collision and back arc spreading terminated continued crustal shortening resulted in the formation of a silurian accretionary terrane telescoped marginal sea and its subsequent deformation second stage collision devonian carboniferous strike slip faulting represents the third stage in the collision history the model is applicable to large tracts of the caledonian appalachian chain its main characteristics are a the revised zonal subdivision of the area is based on characteristics of silurian and older rocks rather than middle ordovician and older rocks only b the central part of the orogen represents a telescoped marginal sea that formed to the southeast of the ordovician volcanic chain rather than a remnant of the incompletely closed iapetus ocean c the earliest deformation is progressively younger toward the southeast d the appalachian collision history is a result of the activity of a single deformation regime over a long period of at least 75 ma

mantle derived helium in foreland basins in xinjiang northwest china abstract hydrocarbon rich natural gases from the tarim junggar turpan hami and santanghu basins in xinjiang northwest china have measured 3he 4he ratios from 0 01 to 0 6 times higher than the atmospheric value indicating 0 7 helium derived from the mantle the mantle derived helium is high in foreland basins associated with the tianshan kunlun and zhayier halalate orogenic mountains but low towards the center of basins this spatial distribution suggests that the mantle derived helium originates either from fluids or small scale melts in the upper asthenospheric or lithospheric mantle which have found pathways into the root zones of the major faults defining these mountains but do not significantly move into the basins themselves during upward transport to near the surface the mantle derived helium is significantly diluted by radiogenic helium produced in the crust despite the lack of recent magmatic activity or extensional tectonics within the basins this pattern shows strong evidence that the major faults play an important role in mantle derived components degassing from the mantle to the surface

the isotopic compositions of molecular nitrogen implications on their origins in natural gas accumulations abstract the isotopic compositions of n2 15 n atm imply the geochemical origins of molecular nitrogen in natural gas accumulations but the irregular variation of 15 n n 2 for most petroliferous basins puzzles scientists we believe that this is due to multiple origins of n2 which are often mixed together and leads to the irregularities in gas pools the four petroliferous basins the west siberian basins in russia the yinggehai basin of china the californian great valley basin of usa and the mid european basin have significantly different isotope characteristics of n2 which may provide insight into the isotope geochemical implications of n2 in natural gas accumulations n2 with 19 15 n n 2 10 may be from sedimentary organic matter at the immature and the early mature stage ro 0 6 values of 10 15 n n 2 2 may indicate that n2 originates from mature including high mature sedimentary organic matter ro 0 6 2 0 values of 2 15 n n 2 15 n n 2 0 and n2 ar 38 84 suggest that the atmosphere is the origin values of 1 15 n n 2 15 n n 2 4 is the feature of n2 from saltpeter in evaporites values of 4 15 n n 2 18 indicate that n2 maybe derived from post mature sedimentary organic matter ro 2 0

origin and migration of oil and natural gas in the central part of the ukrainian outer carpathians geochemical and geological approach the generation and migration processes as well as the influence of secondary processes on oil and natural gas accumulated in lower cretaceous lower miocene strata of the central part of the ukrainian outer carpathians are discussed type ii and ii iii kerogens from the oligocene lower menilite beds of the boryslav pokuttya nappe generated oil and natural gas mainly during the middle stage of the oil window these hydrocarbons accumulated in the fields of the boryslav pokuttya and skiba nappes water washing is the dominant secondary process occurring in many accumulations regardless of reservoir rock whereas biodegradation is insignificant and is clearly evident only in natural gas from one seep in the abandoned starunia ozocerite mine all hydrocarbon gases are thermogenic and were generated from mixed organic matter containing various proportions of type ii and iii kerogens only one natural gas accumulation in the pivnichna dolyna field contains some microbial hydrocarbon contribution carbon dioxide mainly originated from thermogenic kerogen decarboxylation and sporadically from microbial processes molecular nitrogen was mainly generated during low temperature thermal transformation of organic matter and could also partly originate from nh4 rich illites of the clayey facies of the oligocene lower miocene menilite beds the integration of the geochemical data with geological setting and maturation history of source rocks enabled us to reconstruct hydrocarbon migration paths revealing the complicated trap filling process

effects of terrigenic he components on tritium helium dating a case study of shallow groundwater in the saijo basin abstract dating using a combination of 3h and 3he is believed to be the most practical method for estimating the short residence time of shallow groundwater however this method must estimate tritiogenic 3he alone and tends to overestimate the residence time of groundwater if terrigenic 3he from the mantle cannot be excluded from the total dissolved 3he we demonstrate the exclusion of terrigenic 3he in the saijo basin where mantle he is easily released along the major active fault median tectonic line the 3he 4he ratios suggest that the west bank of the kamo river which lies within the basin has experienced greater emanations of mantle he than the east bank we estimate the residence times to be 1 1 96 years by the proposed exclusion method

origin of hydrocarbon and noble gases carbon dioxide and molecular nitrogen in the miocene strata of the eastern part of the polish carpathian foredeep isotopic and geological approach abstract fifteen natural gas samples were collected from the autochthonous miocene strata between debica and przemy l towns in the eastern sector of the polish carpathian foredeep the samples were analysed for the molecular and stable isotope compositions of carbon 13c in ch4 c2h6 c3h8 i c4h10 n c4h10 and co2 hydrogen 2h in ch4 c2h6 and c3h8 nitrogen 15n in n2 and all stable isotopes of noble gases he ne ar kr and xe in order to reveal the origin and migration pathway of these gases methane concentrations usually exceeded 90 vol methane was mainly generated by microbial carbon dioxide reduction the rhythmic and cyclic deposition of clays muds and sands in the miocene marine basin facilitated and intensified microbial processes microbial ethane can be produced by methanogenic archaea from acetate via reduction ethane partly contains a minor component generated from early mature thermogenic process propane and butanes were also generated thermogenically the hydrocarbon gases in the miocene horizons iia and iiia of the gora ropczycka field were generated at higher maturity thermogenic process than the rest of the analysed miocene gases probably from the middle jurassic type iii kerogen they migrated to the miocene horizons from the underlying upper jurassic horizon iv of the same field along a fault carbon dioxide of the analysed miocene gases was mainly generated by primary microbial processes moreover the total carbon constrained in the analysed miocene gases from 0 1 to 6 wt contained mantle derived carbon and thus carbon dioxide mantle component molecular nitrogen was mainly generated during low temperature thermal transformation of organic matter it might also involve a relatively insignificant component released from nh4 rich illites of the clayey facies of miocene strata and an atmospheric component delivered by recharge of air saturated seawater to the reservoir inorganic fluid supply from greater lithospheric depth would not be responsible for the promotion of thermal transformation of organic matter molecular nitrogen from miocene horizons in the gora ropczycka field was generated during the thermal transformation of organic matter of higher maturity than the rest of miocene gases and migrated from the upper jurassic horizon along a fault helium is dominated by its radiogenic component with a minor contribution from the mantle the almost constant mixing ratios of the two helium components in the natural gases from miocene horizons of various depths suggest that he migrated from a common inorganic deep seated source in the lithosphere the other noble gases are dominated by atmospheric components delivered to the hydrocarbon reservoirs by recharge of air saturated seawater with minor nucleogenic 21ne radiogenic 40ar and sedimentary kr and xe contributions the atmospheric component is isotopically fractionated for ne and elementally fractionated with various degrees the ratios of radiogenic 4he to nucleogenic 21ne or radiogenic 40ar are higher than the crustal production ratios suggesting fractionation during thermal release from their host minerals and or phase related fractionation during their transport to the gas reservoirs the striking similarity in noble gas isotopic elemental ratios of the gora ropczycka gas from the miocene horizon iiia to the nearby reservoir in mesozoic strata is consistent with gas migration along a fault system

origin secondary processes and migration of oil and natural gas in the central part of the polish outer carpathians abstract the origin migration pathways and the influence of secondary processes of oil and natural gas accumulated in lower cretaceous to lower miocene strata of the central part of the polish outer carpathians are investigated based on organic geochemical analyses oil and thermogenic hydrocarbon gases were mainly generated from both types ii and iii kerogens in the oligocene menilite beds of the silesian skole and dukla nappes moreover some gases originated from type iii kerogen of lower cretaceous ve ovice shales in the silesian nappe and lower cretaceous spas shales in the skole nappe these gases migrated and subsequently mixed with oil and gas produced from type ii kerogen in the menilite beds the most extensive biodegradation and water washing were observed in oils from harklowa and iwonicz fields and in oil from the bf franek dug well in bobrka rogi field one of the world s oldest with exploitation started in 1854 of the silesian nappe oils most affected by evaporative fractionation come from kro cienko and iwonicz zdroj fields natural gas originated mainly from low mature thermogenic processes oil window with some primary microbial gas contribution primary carbon dioxide reduction and many gas samples show secondary alteration caused by biodegradation carbon dioxide originated from both thermogenic kerogen decarboxylation and microbial processes

origin of hydrocarbon and non hydrocarbon h2s co2 and n2 components of natural gas accumulated in the zechstein main dolomite carbonate reservoir of the western part of the polish sector of the southern permian basin abstract the origin and migration of hydrocarbon and non hydrocarbon hydrogen sulphide carbon dioxide and molecular nitrogen components of natural gas accumulated within the zechstein pz2 stassfurt main dolomite ca2 carbonate reservoir in the western part of the polish sector of the southern permian basin spb were established based on molecular and isotopic compositions 13c ch4 c2h6 c3h8 n c4h10 i c4h10 n c5h12 i c5h12 and co2 2h ch4 15n n2 and 34s h2s related to geological settings and 1 d modelling of generation processes hydrocarbon gases were generated during both microbial and thermogenic processes primary microbial processes ended at the turn of the late permian and early triassic when oil and thermogenic gas generation processes began the reconstruction of the thermal evolution and transformation of organic matter in this part of the spb shows that thermogenic processes ended in the late jurassic in the grotow peninsula zone c and in the late cretaceous in the western part of the wielkopolska platform and gorzow platform zones a and b the presence of the microbial component in analysed accumulations indicates that traps within the ca2 carbonate strata were formed and sealed by the overlying impermeable anhydrites and salts of pz2 stassfurt pz3 leine and pz4 aller cycles preventing its escape accumulation of natural gas in ca2 traps took place in at least two stages and had a cumulative character first microbial gases accumulated then thermogenic gases associated with oil were generated from type ii kerogen in the oil window an insignificant methane component was generated from type iii kerogen and migrated to ca2 reservoir from carboniferous strata h2s was most probably generated during both microbial msr and thermochemical sulphate reduction tsr of anhydrites in the pz1 werra cycle and additionally from thermal decomposition of organic sulphur components of oil and kerogen in the ca2 carbonate rocks msr ended during the late permian tsr was temporarily halted as a result of early cretaceous uplift and probably resumed on a minor scale after the late cretaceous co2 was predominantly generated during thermogenic processes of kerogen decarboxylation carbonate dissolution processes and tsr and msr together with h2s a lesser contribution of co2 from microbial fermentation was also observed to a large extent n2 was mainly generated during thermal transformation of type ii kerogen dispersed in the ca2 carbonate strata and probably partly migrated from carboniferous high maturity type iii kerogen to ca2 reservoirs through fault systems

generation of nitrogen and methane from sedimentary organic matter implications on the dynamics of natural gas accumulations nitrogen n2 contents of natural gases in rotliegend and buntsandstein reservoirs of the north german basin regionally approach 100 a review is given of the various hypotheses primordial origin volcanic or magmatic origin radiogenic origin atmospheric origin organic origin inorganic nitrogen in sedimentary rocks presented to account for nitrogen anomalies in this area and other parts of the world the objective of the present study was to investigate sedimentary organic matter in particular coals as a potential source of molecular nitrogen in the subsurface comparison of reservoir sizes and gas generation potentials indicates that carboniferous coal measures which are considered as the source of the natural gas in the north german basin can readily account for the nitrogen quantities found in present day reservoirs laboratory pyrolysis experiments were carried out to investigate the kinetics of generation of methane and molecular nitrogen from coals of different type and rank under experimental conditions nitrogen is formed at higher temperatures than methane supporting the concept of a fractional generation of methane and nitrogen in natural systems based on the kinetic parameters derived from laboratory experiments methane and nitrogen generation rates from coals were calculated for geologic heating rates gas containing more than 50 nitrogen is generated under these conditions at temperatures in excess of 300 c nitrogen rich gases are thus formed only in the final stage of gas generation after methane generation has practically ceased it is concluded that the amounts of gas encountered in nitrogen rich gas accumulations represent only a small fraction possibly 1 of the total gas generation potential of this area while the bulk of the generated gas has escaped to the atmosphere the present day composition of the reservoir gases reflects the composition of only the most recently generated gas on a geologic time scale

origin of hydrocarbon and noble gases carbon dioxide and molecular nitrogen in devonian pennsylvanian and miocene strata of the polish lublin and ukrainian lviv basins southern part of the upper silesian coal basin and western part of the carpathian foredeep poland abstract sixteen natural gas samples were collected from devonian pennsylvanian and miocene strata of the polish lublin and ukrainian lviv basins from the southern area of the upper silesian coal basin uscb and western part of the carpathian foredeep cf in poland the samples were analysed for the molecular composition and stable isotope compositions of gaseous hydrocarbons ch4 c2h6 and c3h8 and co2 n2 and noble gases he ne ar kr and xe in order to reveal the origin and migration pathways of these gases hydrocarbon gases and the majority of the of co2 were generated during two stages of thermogenic processes from type ii and ii iii kerogens in the lublin basin and during both thermogenic and microbial processes in the lviv basin the thermogenic component was generated from type ii kerogen coal bed hydrocarbon gases accumulated in the pennsylvanian strata of the southern part of the uscb originated from both thermogenic and microbial processes isotopically light microbial methane may have migrated from miocene upper badenian skawina formation of the cf to carboniferous coal bearing strata and or might result from diffusion and adsorption desorption processes during the migration of thermogenic gases from deeper lying coal seams through the microporous coal structure hydrocarbon gases and carbon dioxide which accumulated in the sandstone reservoirs of upper badenian skawina formation of the western part of the cf most probably were generated from dispersed organic matter within the claystones and mudstones of these strata and at least partly migrated from the carboniferous coal bearing strata of the uscb n2 could have been produced as a result of various biogenic and abiogenic processes and contributed to the atmospheric component characteristic radiogenic 4he composition of the analysed gases suggest the accumulation of particles formed from u and th radioactive decay in the crustal gas reservoirs radiogenic 40ar and nucleogenic 21ne with abundance ratios characteristic of crustal reservoirs were also observed addition of mantle derived he to the gases from miocene strata is evident from elevated 3he 4he ratios ranging between 0 2 and 1 6 10 6 a small contribution of ne from the mantle along with he is also suggested by the slightly elevated 20ne 22ne ratios relative to atmosphere the mantle component is most likely to have migrated from the upper mantle to the gas reservoirs through the deep seated bzie czechowice fault zone

investigation of the pyrolytic liberation of molecular nitrogen from palaeozoic sedimentary rocks open system non isothermal pyrolysis up to 1 200 c in combination with elemental analysis was used to study the thermal liberation of molecular nitrogen n2 from sedimentary rocks and kerogen concentrates of palaeozoic age from the central european basin system and an eocene shale liaohe basin china with a high content 36 of ammonium feldspar buddingtonite the n corg atomic ratios of the kerogen concentrates ranged from 0 005 to 0 014 which represents the range commonly observed for coals bulk n corg ratios of the palaeozoic shales extended from 0 035 to 0 108 indicating the presence of significant amounts of inorganic nitrogen namurian a and a b cna cna b samples typically exhibited the earliest onset of n2 generation with intense characteristic peaks around 600 c n2 liberation from the buddingtonite rich sample occurred at higher temperatures with a broad peak around 700 c pyrograms of the kerogen concentrates showed no or strongly reduced n2 generation in the 500 700 c range on line isotope specific analysis of the pyrolytically liberated n2 on one sample revealed a variability of 10 in the 15n values and a steady increase in 15n with temperature during the main phase of n2 generation

organic geochemical study of source rocks and natural gas and their genetic correlation in the eastern part of the polish outer carpathians and palaeozoic mesozoic basement abstract geochemical characteristics of organic matter in the profiles of dukla silesian sub silesian and skole units of the polish outer carpathians and of the palaeozoic mesozoic basement in the debica rzeszow lezajsk sanok area were established based on rock eval vitrinite reflectance isotopic and biomarker analyses of 485 rock samples the oligocene menilite beds have the best hydrocarbon potential of all investigated formations within the dukla silesian and skole units the ordovician silurian lower devonian and locally middle jurassic strata of the palaeozoic mesozoic basement are potential source rocks for oil and gas accumulated in palaeozoic and mesozoic reservoirs thirty one natural gas samples from sandstone reservoirs of the lower cretaceous lower miocene strata within the outer carpathian sequence and eight from sandstone and carbonate reservoirs of the palaeozoic mesozoic basement were analysed for molecular and isotopic compositions to determine their origin natural gases accumulated both in the outer carpathian and the palaeozoic mesozoic basement reservoirs are genetically related to thermogenic and microbial processes thermogenic gaseous hydrocarbons that accumulated in the dukla and silesian units were generated from the menilite beds thermogenic gaseous hydrocarbons that accumulated in the sub silesian unit most probably migrated from the silesian unit initial and probably also secondary microbial methane component has been generated during microbial carbon dioxide reduction within the oligocene menilite beds in the dukla unit and oligocene lower miocene krosno beds in the silesian unit natural gases that accumulated in traps within the middle devonian mississippian upper jurassic and upper cretaceous reservoirs of the palaeozoic mesozoic basement were mainly generated during thermogenic processes and only sporadically from initial microbial processes the thermogenic gases were generated from kerogen of the ordovician silurian and middle jurassic strata the microbial methane component occurs in a few fields of the dukla and silesian units and in the two accumulations in the middle devonian reservoirs of the palaeozoic mesozoic basement

predicting co2 occurrence on a regional scale southeast asia example abstract prediction of co 2 occurrence in natural gases is difficult owing to the interplay among basinal sources e g volcanic emanations carbonate hydrolysis and metamorphism organic diagenesis and maturation reservoir processes e g mineralogical transformations and poorly understood physicochemical phenomena e g differential solubility of gas components carbonate buffering phase segregation published approaches to assessing co 2 risk are based either on circumstantial evidence of basinal influences or statistical analysis of reservoir attributes the present study presents the results of empirical statistical and neural network analysis of co 2 abundance in natural gas and discusses potentially influential basinal and reservoir attributes to quantify risk factors for anomalous co 2 occurrences in southeast asia the results of this study indicate that tectonic setting including basement crustal age basement fault density reservoir temperature and reservoir pressure are key elements controlling co 2 abundance assignment of co 2 risk at the basin level can be roughly approximated using the results of this study more accurate assessments of co 2 risk at the basin play field and reservoir levels require more comprehensive geological and geochemical data as well as consideration of potentially influential physico chemical processes

mica beards in three slates morphology formation and bearing on the strain history beards are intergrowths of mica chlorite and quartz or feldspar on detrital grains in weakly metamorphosed sedimentary rocks the three samples studied contain beards of mica and quartz or feldspar their internal morphology shows a variation in mica orientation related to the external foliation matrix formation occurred during foliation development with a syntaxial growth history in three dimensions the beards have oblate shapes so that they are present in all planes cut parallel to the shortening direction this indicates flattening strain conditions around the detrital grains during the beard formation

geochemistry and tectonic significance of the mafic volcanic blocks in the dunnage melange north central newfoundland abundant volcanic blocks are present in the dunnage melange these mafic volcanic rocks consist predominantly of pillow lava tuff breccia isolated pillow tuff breccia and minor amounts of ropy lava major and trace element compositions of the basalts reveal that these volcanics do not resemble calc alkaline or low potassium island arc suites rather the majority of the samples are enriched type ocean floor tholeiites whereas some show alkali basalt affinities discrimination diagrams suggest that these basalts may have been erupted as within plate basalts however the chemical composition of the volcanic blocks is most similar to that of basalts generated at bathymetric highs located astride or slightly off mid ocean ridges the geochemistry of the dunnage melange basalts is very similar to that of the mafic volcanic rocks from the nearby summerford group and the lawrence head formation this correlation is further supported by sedimentary and petrographic evidence and by partial age equivalency

stable isotope geochemistry of the nitrogen rich gas from lower cambrian shale in the yangtze gorges area south china abstract the organic rich marine shales from the lower cambrian niutitang formation in the yangtze gorges area are characterized by their high toc values 0 54 5 13 types i and ii organic matter and high ro values 2 4 2 6 geochemical parameters of 19 gas samples from the lower cambrian shale formation from well zd 1 were analyzed in this study the gases are dominated by methane with small amounts of ethane and no propane or butane the 13 c ch 4 values range from 31 7 to 27 9 the 13 c c 2 h 6 values range from 35 2 to 33 4 and the 2 h ch 4 values range from 214 to 187 furthermore carbon isotopic compositions of the alkane gases from the lower cambrian shale are characterized by 13 c 1 13 c 2 these results indicate that the gases are of thermogenic origin and are oil derived moreover methane with heavy carbon isotopic and light hydrogen isotopic values may be produced when water reacts with inorganic carbon the isotopic reversal of alkane gases was probably due to destructive redox reactions at maximum burial resulting in rayleigh type fractionation and or mixing by gases from the same source but at a different maturity nitrogen occurs in the analyzed gases at concentrations from 8 15 to 96 52 and the 15 n n 2 values vary from 3 2 to 7 4 the 15 n n 2 values and high illite content suggest that nitrogen was mainly generated during thermal transformation of organic matter and or from nh 4 rich illites of the clayey facies of the lower cambrian shale carbon dioxide concentrations vary from 1 13 to 4 96 and the 13 c co 2 values range from 8 9 to 13 6 this suggests that carbon dioxide was mainly generated during thermogenic processes of transformation of organic matter moreover the major reason for the change in nitrogen and methane contents in the studied well zd 1 is probably due to the development of micro cracks in core samples with high contents of nitrogen a high nitrogen content may be caused by the strong adsorption capacity of nitrogen which leads to the retention of nitrogen and the diffusion of methane in shale