geochemical characteristics of the extremely high thermal maturity transitional shale gas in the southern north china basin sncb and its differences with marine shale gas abstract a great number of studies have been carried out on the geochemical characteristics of marine shale gas from the lower silurian longmaxi formation in the sichuan basin however a systematic study on geochemical and isotopic characteristics of transitional shale gas gas from the alternating marine terrigenous shale facies has not been well addressed in the present study transitional shale gas from the lower permian shanxi p1s and taiyuan p1t formation in the southern north china basin sncb were collected and analyzed for their geochemical and isotopic compositions the hydrocarbon gases are dominated by methane with small amounts of ethane without propane and butane which is consistent with the extremely high thermal maturity of the gas shales ro values between 3 2 and 4 2 compared with marine shale gas the relatively high non hydrocarbon components may be associated with the humic source rocks the 13c1 values range from 31 6 to 21 0 and the 13c2 values range from 35 9 to 26 1 the 2hch4 values range from 221 to 138 these results indicate that the gases are of thermogenic origin methane with anomalous heavy carbon isotopic and light hydrogen isotopic values was interpreted as redox reactions of gases with transition metals and water at maximum burial resulting in rayleigh type fractionation the difficulties of identifying marine and transitional shale gas may be due to the complete or partial carbon isotopic reversal caused by secondary alteration and the extremely high thermal maturity of the gas shales co2 concentration and 13c co2 values suggest that co2 in the transitional shale gas was mainly thermogenic origin and formed together with hydrocarbon generation furthermore significant differences can be observed from the co2 in different types of shale gas co2 in the transitional shale gas is mainly distributed in areas with co2 5 and 13c co2 8 the 15n n2 values and high illite and illite smectite mixed clay i s content suggest that nitrogen in transitional shale gas was possibly generated during thermo ammoniation of organic matter and or the breakdown of nh4 rich clay minerals in addition based on the geochemical characteristics of marine and transitional shale gas a geochemical pattern of shale gas is presented in this paper

high thermal maturity in the lower saxony basin intrusion or deep burial abstract the lower saxony basin lsb is situated at the southern rim of the northern permian basin the most important hydrocarbon bearing province in europe in its southern part areas of high thermal maturation up to 6 rr occur which were previously explained as being caused by magmatic intrusions of turonian to santonian age that affected carboniferous to lower cretaceous rocks in this area 2d numerical basin modelling was carried out in order to reconstruct the temperature histories along two parallel n s trending seismic sections along these sections new data about maturity distribution and temperature history were obtained by vitrinite reflectance measurements and apatite fission track analysis for the areas with highest maturity values low coalification gradients were established which agree well with earlier published data on wells further towards the west this new information does not support previous hypotheses on high heat flows from magmatic intrusions even if lateral heat transport is taken into account instead comparisons with a recently published map of the subsurface structure of the lsb indicate that maturity distribution may be closely related to major tectonic structures deep burial of individual structures of the lsb which are bordered by deep e w to ese wnw trending faults is further suggested by a rapidly increasing thicknesses of preserved cretaceous strata towards the south and b structural restoration of one of the seismic sections to achieve a fit between measured and calculated palaeo temperature and vitrinite reflectance data deep burial of carboniferous source rocks during cretaceous time has to be assumed due to an inversion phase in the early and middle upper cretaceous major amounts of sediment were removed and further uplift occurred in tertiary times in contrast the northern part of the lsb experienced maximum burial and temperatures during tertiary times

hydrocarbon composition of authigenic inclusions application to elucidation of petroleum reservoir filling history abstract geochemical analysis of petroleum inclusions trapped in authigenic feldspar and quartz in the ula formation in the north sea ula oil field revealed a petroleum of markedly different composition than the oil presently in the reservoir using microthermometry and the burial history as a dating tools it is concluded that the petroleum in the k feldspar inclusions was present in the more porous and permeable parts of the ula formation as early as 45 75 my bp when the field was at a depth of about 1 0 1 5 km as compared with the current depth of 3 4 km this early petroleum which was trapped as inclusions in authigenic k feldspar shows a distinctly different distribution of tricyclic terpanes and pentacyclic triterpanes from that of the current petroleum charge in the ula formation which was derived from the mandal formation source rock in late neogene time molecular parameters show that the oil in the k feldspar inclusions is significantly less mature than the crude oil in the present reservoir the approximate 90 c temperature increase occurring after entrapment of the early petroleum in kfeldspar the field is currently at 143 c appears not to have reset the low maturity signature of the oil in the k feldspar inclusions this could suggest that the temperature in the inclusions is too low for isomerization selective thermal degradation to occur lack of catalysts or that there are other controls on the ratio of some of these parameters still parameters like the ratio of c21 to c28 triaromatic steroids and those based on dimethyl and trimethyl naphthalenes are comparatively similar in both the inclusions and in the reservoir crude the oil inclusions in authigenic quartz and albite formed from about 10 my bp burial depth 2 5 km until the present burial depth 3 4 km are interpreted as representing a palaeo petroleum charge having a composition intermediate between the oil found in k feldspar inclusions and the oil charge in the present reservoir our data suggest strongly that the petroleum trapped in the inclusions in quartz and plagioclase represents progressive dilution of the early reservoired oil now found only in k feldspar inclusions with oil from the mandal formation analysis of solution gas in these inclusions suggests that the first petroleum associated gas to arrive at the trap from the progressively maturing mandal formation had a much wetter composition than the current reservoir solution gas to explain the present comparatively drier and isotopically lighter reservoir solution gas composition the inference is made that there has been a recent during formation of k feldspar inclusions 45 75 my bp maturation of the upper jurassic mandal formation the main source rock in this region was limited possibly to the graben axis this suggests that the petroleum found in the k feldspar inclusions was most likely derived from a deeper post caledonian palaeozoic formation

permo carboniferous magmatism of the northeast german basin abstract variscan continent continent collision in central europe was followed by a period of syn to late tectonic magmatism involving the extrusion of large volumes of permosilesian age volcanic rocks particularly in the northeast german basin the volcanic suite up to ca 2000 m thick comprises rhyolites acid and basic andesites and tholeiitic and alkali basalts tectono geochemical analysis in conjunction with volume calculations and petrography reveals changes in volcanic activity over time a total of five eruptive stages are recognised beginning in the stephanian and extending up into the upper rotliegend permian these include the stephanian late carboniferous andesite pre ignimbrite stage i lower rotliegend permian age explosive ignimbrite stage ii post ignimbrite stage iii late rhyolite stage iv and upper rotliegend permian age late basalt stage v in addition several volcanic centres including at least two large caldera like structures are recognised the total calculated volume for the northeast german basin volcanics is ca 48 000 km3 comprising rhyolitic rocks and ignimbrites ca 70 andesitic rocks ca 26 and basalts with cogenetic dolerites ca 4 regional variations in composition and geochemistry are related to diverse crust mantle regimes which correlate with differing positions relative to the heterogeneous basement of the variscan foredeep or within the rhenohercynian orogenic zone the crustal thickening and increasing generation depth of the mafic magmas from north to south may reflect the presence of a pre existing subduction influenced basaltic magma source

impacts of hydrothermal dolomitization and thermochemical sulfate reduction on secondary porosity creation in deeply buried carbonates a case study from the lower saxony basin northwest germany the role of deep burial dissolution in the creation of porosity in carbonates has been discussed controversially in the recent past we present a case study from the upper permian zechstein 2 carbonate reservoirs of the lower saxony basin in northwest germany these reservoirs are locally characterized by high amounts of carbon dioxide co2 and variable amounts of hydrogen sulfide h2s which are derived from thermochemical sulfate reduction tsr and inorganic sources to study the contribution of these effects on porosity development we combine petrography stable isotope and rare earth and yttrium rey analyses of fracture cements with raman spectroscopy and 13c analyses of fluid inclusions it is shown that fluid migration along deep fault zones created and redistributed porosity fluid inclusion analyses of vein cements demonstrate that hydrothermal fluids transported inorganic co2 into the reservoir where it mixed with minor amounts of tsr derived organic co2 the likely source of inorganic co2 is the thermal decomposition of deeply buried devonian carbonates the rey distribution patterns support a hydrothermal origin of ascending iron and co2 rich fluids causing dolomitization of calcite and increasing porosity by 10 16 along fractures this porosity increase results from hydrothermal dolomitization and dissolution by acids generated from the reaction of fe2 with h2s to precipitate pyrite in contrast hydrothermal dolomite cements reduced early diagenetic porosity in dolomitic intervals by approximately 17 however the carbonate dissolution in the predominantly calcitic host rock results in a net increase in porosity and permeability in the vicinity of the fracture walls which has to be considered for modeling reservoir properties and fluid migration pathways

predicted bulk composition of petroleum generated by lower cretaceous wealden black shales lower saxony basin germany the berriasian wealden shale provides the favourable situation of possessing immature to overmature source rock intervals due to differential subsidence within the lower saxony basin hydrocarbon generation kinet ics and petroleum physical properties have been investi gated on four immature wealden shale samples situated in different depth intervals and following the phaseki netics approach of di primio and horsfield aapg bull 90 7 1031 1058 2006 kinetic parameters and phase prediction were applied to a thermally calibrated 1d model of the geodynamic evolution at the location of an overmature well the immature source rocks of all depth intervals comprise kerogen type i being derived from the lacustrine algae botryococcus braunii bulk kinetics of the lower three depth intervals sample 2 4 can be described by one single activation energy ea typical for homogene ous lacustrine organic matter om whereas sample 1 from the uppermost interval shows a slightly broader ea distribution which hints to a more heterogeneous less sta ble om but still of lacustrine origin predicted physical

modeling and mechanistic interpretation of creep of rock salt below 200 c abstract upper and lower bound estimates of the steady state strain rates of rock salt from five locations are analyzed the measurements were obtained in triaxial creep tests including systematic changes in stress and temperature the various data sets are correlated in activation analyses and fitted by models and combinations of models for power law creep cross slip and dislocation glide to show that a cross slip model yields the best mechanistically most credible fit good fits for cross slip and high power law stress exponents rule out the possibility that pressure solution affected the data in a major way to the lowest recorded strain rates of order 10 10s 1

rheology of synthetic polycrystalline halite in torsion abstract motivated by the need for halite rheology we investigated the stress strain strain rate behaviour of halite to high shear strains in torsion using polymer jackets whose strength does not influence halite rheology the experimental results show that 1 halite strength decays exponentially with temperature increase being very weak at 300 c ca 2 nm 2 power laws fit the stress strain rate data from which we determined the stress exponent n between ca 13 60 c and ca 3 200 c indicating that n decreases exponentially with temperature increase 3 the activation energy q decreases exponentially with temperature increase from ca 159 kj mol 38 kcal mol at 60 c to ca 59 kj mol 14 kcal mol at 200 c 4 q depends linearly on n with a slope of ca 10 the empirical constitutive equation 12 1 exp 9 6 7 1 e 6 exp 1 t 1 9 e 4 2 5 9 3 e6exp t 24 3 describes the experimental results comparison of the present and previous experimental results shows that halite is much weaker in shear than in axial compression or extension this difference likely results from the rotational component of simple shear

natural fracking and the genesis of five element veins hydrothermal ag co ni bi as five element vein type ore deposits show very conspicuous textures of the native elements silver bismuth and arsenic indicating formation from a rapid far from equilibrium process such textures include up to dm large tree and wire like aggregates overgrown by co ni fe arsenides and mostly carbonates despite the historical and contemporary importance of five element vein type deposits as sources of silver bismuth and cobalt and despite of spectacular museum specimens their process of formation is not yet understood and has been a matter of debate since centuries we propose based on observations from a number of classical european five element vein deposits and carbon isotope analyses that natural fracking i e liberation of hydrocarbons or hydrocarbon bearing fluids during break up of rocks in the vicinity of an active hydrothermal system and mixing between these hydrocarbons e g methane and or methane bearing fluids and a metal rich hydrothermal fluid is responsible for ore precipitation and the formation of the unusual ore textures and assemblages thermodynamic and isotope mixing calculations show that the textural chemical and isotopic features of the investigated deposits can entirely be explained by this mechanism

propagation of slow slip leading up to the 2011 mw 9 0 tohoku oki earthquake many large earthquakes are preceded by one or more foreshocks but it is unclear how these foreshocks relate to the nucleation process of the mainshock on the basis of an earthquake catalog created using a waveform correlation technique we identified two distinct sequences of foreshocks migrating at rates of 2 to 10 kilometers per day along the trench axis toward the epicenter of the 2011 moment magnitude mw 9 0 tohoku oki earthquake in japan the time history of quasi static slip along the plate interface based on small repeating earthquakes that were part of the migrating seismicity suggests that two sequences involved slow slip transients propagating toward the initial rupture point the second sequence which involved large slip rates may have caused substantial stress loading prompting the unstable dynamic rupture of the mainshock

weakening of rock salt by water during long term creep the rheological properties of rock salt are of fundamental importance in predicting the long term evolution of salt based radioactive waste repositories and strategic storage caverns and in modelling the formation of salt diapirs and associated oil traps1 2 the short term high stress rheology of rock salt is well known from laboratory experiments however extrapolation to appropriately low stresses fails to predict the rapid flow seen in certain natural structures furthermore experiments have failed to reproduce the recrystallized microstructure of naturally deformed salt here we report experiments indicating that the above discrepancies can be explained by taking into account the influence of trace amounts of brine trace brine is always present in natural salt but sometimes escapes during experiments our tests on dry dilated salt show more or less conventional dislocation creep behaviour but brine bearing samples show marked weakening at low strain rates this is associated with dynamic recrystallization and a change of deformation mechanism to solution transfer creep because natural rock salt always contains some brine these results cast substantial doubt on the validity of presently accepted dislocation creep laws for predicting the long term rheological behaviour of salt in nature

diagenesis and fluid mobilisation during the evolution of the north german basin evidence from fluid inclusion and sulphur isotope analysis abstract samples of diagenetic and hydrothermal minerals from drillcores along the dekorp 9601 seismic traverse in the north german basin were investigated for their fluid inclusion and sulphur isotope composition to reconstruct the thermal and chemical evolution of fluid systems during basin evolution the stages of basin subsidence and subsequent inversion are marked by fluid systems of distinct composition the basinwide zechstein evaporite units formed an aquiclude disconnecting convecting fluids in the underlying rotliegend volcanics from the overlying units 34 s ratios of sulphides suggest a sedimentary sulphur source 34 s ratios of diagenetic and hydrothermal sulphates indicate that sulphur was derived partly from rotliegend volcanic units and partly from the evaporitic zechstein

anomalous pre seismic transmission of vhf band radio waves resulting from large earthquakes and its statistical relationship to magnitude of impending earthquakes summary to confirm the relationship between anomalous transmission of vhf band radio waves and impending earthquakes we designed a new data collection system and have documented the anomalous vhf band radio wave propagation beyond the line of sight prior to earthquakes since 2002 december in hokkaido northern japan anomalous vhf band radio waves were recorded before two large earthquakes the tokachi oki earthquake mj 8 0 mj magnitude defined by the japan meteorological agency on 2003 september 26 and the southern rumoi sub prefecture earthquake mj 6 1 on 2004 december 14 radio waves transmitted from a given fm radio station are considered to be scattered such that they could be received by an observation station beyond the line of sight a linear relationship was established between the logarithm of the total duration time of anomalous transmissions te and the magnitude m or maximum seismic intensity i of the impending earthquake for m4 m5 class earthquakes that occurred at depths of 48 54 km beneath the hidaka mountains in hokkaido in 2004 june and 2005 august similar linear relationships are also valid for earthquakes that occurred at different depths the relationship was shifted to longer te for shallower earthquakes and to shorter te for deeper ones numerous parameters seem to affect te including hypocenter depths and surface conditions of epicentral area i e sea or land this relationship is important because it means that pre seismic anomalous transmission of vhf band waves may be useful in predicting the size of an impending earthquake

fluid inclusion evidence for low temperature thermochemical sulfate reduction tsr of dry coal gas in upper permian carbonate reservoirs zechstein ca2 in the north german basin abstract upper permian zechstein carbonate ca2 gas reservoirs in the southern part of the pompeckj block in the north german basin locally contain up to 36 vol hydrogen sulfide h2s produced by thermochemical sulfate reduction tsr tsr was triggered by migration of dry to extremely dry coal gas from upper carboniferous into the zechstein carbonate reservoirs methane reacted with dissolved sulfate at temperatures of the results of this study decipher three major stages of gas migration in the pompeckj block stage i commenced in the late triassic during burial when zechstein ca2 reservoirs were charged with dry ch4 co2 n2 gas sourced from mature upper carboniferous coals burial continued through the jurassic and caused alteration of ca2 reservoir gas by sulfate reduction reactions due to increasing temperatures entrapment of ch4 h2s co2 n2 gases in fluid inclusions hosted in cements and fracture filling minerals occurred at temperatures between 100 and 152 c and was related to stage ii uplift in the early lower cretaceous in the late cretaceous stage iii deep burial of the pompeckj block led to charge of the zechstein ca2 carbonate reservoirs with upper carboniferous derived ch4 co2 n2 c2 coal gas and or dilution of existing reservoir gas at temperatures of 144 167 c highly variable 13cch4 values from 18 7 to 8 7 and very negative 13cco2 values 22 4 to 18 9 of h2s rich fluid inclusion gases as well as negative 13c values 10 4 to 4 6 of host calcites reveal compelling evidence for participation of methane in tsr fluid inclusions imply that ch4 dominated tsr proceeded at tmin of 135 c in the presence of catalyzers such as h2s and dissolved mg2 this study demonstrates that fluid inclusions serve as an excellent and accurate tool for tracing h2s concentrations in hydrocarbon gases through time and space which is not possible using the present day compositions of natural reservoir gases it also contributes to the understanding of carbonate reservoir hosted hydrocarbon bearing fluid systems and processes that significantly control the quality of reservoir gases

evolution of the lower saxony basin abstract the lower saxony basin is a 300 km long and 65 km wide late jurassic and early cretaceous trough which parallels the northern margin of the rhenish massif this basin became inverted during the senonian and paleocene the lower saxony basin is the most important oil province of germany past production amounts to 200 10 6 t of oil 1 5 10 9 bbl the lower saxony basin is superimposed on the late carboniferous variscan foredeep basin and the frontal structures of the variscan fold belt during the permian to middle jurassic the area formed part of the northwest european basin differential subsidence of the lower saxony basin was initiated during the late jurassic and persisted till albian time this involved reactivation of permo carboniferous fracture systems by divergent wrenching a major aptian deep seated laccolith is evident in the western part of the lower saxony basin during the senonian and paleocene sinistral convergent wrenching induced uplift of the basin floor and folding of its sedimentary fill the margins of the inverted lower saxony basin are thrust over the adjacent stable platform areas the differential subsidence of the lower saxony basin can be related to a period of major crustal extension in the north sea rift basin inversion coincides with important orogenic events in the alpine system and is thought to have been induced by intra plate compressional stresses

coalescing microstructure and fabric transitions with ams data in deformed limestone implications on deformation kinematics abstract the microstructures of the heterogeneously deformed limestones of the kolhan group singhbhum craton sc eastern india are investigated to study deformation mechanism grain size and shape preferred orientation spo development the texture of the deformed rocks is analyzed by electron back scattered diffraction ebsd in order to determine crystallographic preferred orientation cpo development in calcite grains the c axis pattern in protomylonite and mylonite define girdle patterns developed perpendicular to local shear planes showing monoclinic symmetry the latter is interpreted in terms of a top to south shear which is consistent with the observed microstructural and fabric data from the deformed rocks the anisotropy of magnetic susceptibility ams studies are performed on 22 heterogeneously strained limestone specimens to document strain variation within the kolhan rocks the field fabric spo data measured from calcite and mica grains cal and mi and calcite cpo data are compared with observed variation in ams fabric intensity pj across the kolhan basin integration of these data sets help to establish presence of large internal thrust planes within the kolhan basin which form a part of the regional foreland vergent thrust system developed along the northern margin of the sc

do co2 charged fluids contribute to secondary porosity creation in deeply buried carbonates abstract carbonate dissolution by acidic co2 charged fluids is one possible mechanism leading to the creation of burial porosity the late permian carbonates of the lower saxony basin nw germany are a suitable target to study the influence of such co2 charged fluids on porosity evolution the so called zechstein 2 carbonates ca2 consist of alternating dolomitic and calcitic intervals and contain locally very high amounts of co2 80 and variable amounts of h2s in reservoir gas and vein cement hosted fluid inclusions composition and isotope data from fluid inclusions suggest that the co2 is sourced from the thermal decomposition of underlying devonian carbonates far reaching fault systems connect the devonian co2 source with the permian ca2 reservoir while thick rock salt deposits above the zechstein 2 carbonates prohibit an influence of surface derived meteoric fluids the aim of the study is to evaluate the contribution of co2 on carbonate dissolution seven wells were preferentially sampled along mineral veins which are interpreted as the preferred migration pathways for the present gas classic petrography methods such as transmitted light microscopy and cathodoluminescence were combined with fluid inclusion analysis and porosity data petrographic analysis reveals no great impact of the massive co2 presence on porosity creation as fluids get quickly saturated with respect to ca2 minor vuggy porosity is associated with fractures in only one of the studied wells but the dominant porosity types are early diagenetic fabric selective oomoldic and intercrystal porosity to evaluate whether the porosity values are higher than usual a comparison with a global porosity dataset is included which however shows no increase in average porosities compared to global values the results of this case study suggest that the contribution of co2 alone on carbonate dissolution and therefore reservoir quality is negligible as long as other processes such as late dolomitization or pyrite formation by thermochemical sulphate reduction derived h2s are absent

rheology of rocksalt abstract we review progress in experimental determinations of transient and steady state flow properties and processes of natural rocksalt aggregates focusing primarily on results from avery island louisiana domal salt the steady state flow field established from constant stress and constant strain rate tests at temperatures from 50 to 200 c strain rates from 10 5 to 10 9 s 1 and differential stresses from 20 7 to 2 5 mpa has been separated into two flow regimes each fit by a power law relation at the higher stresses and strain rates this relation is e 1 6 10 4 exp 68 1 rt 10 3 5 3 for which the pre exponential constant is expressed in mpa 5 3 s 1 and the apparent activation energy is in j mol 1 creep rates predicted by equation a do not differ appreciably from those predicted previously the relatively low stress low strain rate data are very well fit by e 8 1 10 5 exp 51 6 rt 10 3 2 4 which is comparable conditions predicts creep rates higher and equivalent viscosities lower than does equation a by two orders of magnitude the change in behavior from a to b is ascribed to a change in rate limiting mechanism from cross slip of screw dislocations to the climb of edge dislocations in this dry material subgrain formation dominates microstructural development during steady state flow of salt and from determinations of average subgrain diameters in crystals from 20 different rocksalt bodies flow stress levels between 0 6 and 1 4 mpa have been estimated these values do not bear directly on arguments concerning the nature of forces initiating salt pillow growth because apparently evidence relating to the early deformational history has been overprinted at that stage fluid assisted grain boundary diffusional processes might dominate dislocation creep leading to a linear stress strain rate mechanical response considering buoyancy forces alone behavior described by equation b rather than a reduces the relief necessary to initiate pillow growth but a 1000 fold amplification is required to produce stress differences near 1 mpa that forces other than buoyancy are important is indicated by the occurrence of these same paleostress levels in bedded salts and in shallow offshore concordant intrusions differential loading generally provides the most plausible initial driving force for the growth of diapiric salt structures

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

on the origin of the southern permian basin central europe abstract a detailed study of the structural and stratigraphic evolution of the southern permian basin during latest carboniferous to early jurassic times supported by quantitative subsidence analyses and forward basin modelling for 25 wells leads us to modify the conventional model for the rotliegend zechstein development of this basin the late permian early jurassic tectonic subsidence curves are typical for a permian to early triassic extensional stage that is followed by thermal subsidence however a purely extensional model is extremely problematic because active faulting during this time is minor and generally hard to document using inverse techniques to model the subsidence curves we quantitatively show that a significant component of late permian and triassic tectonic subsidence can be explained by thermal relaxation of early permian lithospheric thinning and by delayed infilling of paleo topographic depressions that developed during the early permian in this interpretation stephanian autunian wrenching resulted in thermal destabilisation of the lithosphere deep fracturing of the crust disruption and erosion of its sedimentary cover and regional uplift of the area of the future southern permian basin upon termination of wrench tectonics and associated volcanism towards the end of the autunian the southern permian basin began to subside in response to thermal contraction of the lithosphere the evolving basin was isolated from the world oceans and had subsided possibly up to some 700 m below their level at the beginning of upper rotliegend sedimentation after catastrophic flooding of this paleo topographic depression at the beginning of the zechstein changing sea level sedimentation and subsidence rates remained essentially in balance although the effects of triassic rifting overprinted parts of the southern permian basin its overall subsidence pattern persisted well into the jurassic in contrast to the remainder of the southern permian basin permian and triassic crustal extension contributed significantly to the subsidence of the polish trough

characterization of coal derived hydrocarbons and source rock potential of coal beds san juan basin new mexico and colorado u s a coal beds are considered to be a major source of nonassociated gas in the rocky mountain basins of the united states in the san juan basin of northwestern new mexico and southwestern colorado significant quantities of natural gas are being produced from coal beds of the upper cretaceous fruitland formation and from adjacent sandstone reservoirs analysis of gas samples from the various gas producing intervals provided a means of determining their origin and of evaluating coal beds as source rocks the rank of coal beds in the fruitland formation in the central part of the san juan basin where major gas production occurs increases to the northeast and ranges from high volatile b bituminous coal to medium volatile bituminous coal rm values range from 0 70 to 1 45 on the basis of chemical isotopic and coal rank data the gases are interpreted to be thermogenic gases from the coal beds show little isotopic variation 13c1 values range 43 6 to 40 5 ppt are chemically dry c1 c1 5 values are 0 99 and contain significant amounts of co2 as much as 6 these gases are interpreted to have resulted from devolatilization of the humic type bituminous coal that is composed mainly of vitrinite the primary products of this process are ch4 co2 and h2o the coal generated methane rich gas is usually contained in the coal beds of the fruitland formation and has not been expelled and has not migrated into the adjacent sandstone reservoirs in addition the coal bed reservoirs produce a distinctive bicarbonate type connate water and have higher reservoir pressures than adjacent sandstones the combination of these factors indicates that coal beds are a closed reservoir system created by the gases waters and associated pressures in the micropore coal structure in contrast gases produced from overlying sandstones in the fruitland formation and underlying pictured cliffs sandstone have a wider range of isotopic values 13c1 values range from 43 5 to 38 5 ppt are chemically wetter c1 c1 5 values range from 0 85 to 0 95 and contain less co2 2 these gases are interpreted to have been derived from type iii kerogen dispersed in marine shales of the underlying lewis shale and nonmarine shales of the fruitland formation in the underlying upper cretaceous dakota sandstone and tocito sandstone lentil of the mancos shale another gas type is produced this gas is associated with oil at intermediate stages of thermal maturity and is isotopically lighter and chemically wetter at the intermediate stage of thermal maturity as compared with gases derived from dispersed type iii kerogen and coal this gas type is interpreted to have been generated from type ii kerogen organic matter contained in coal beds and carbonaceous shales of the fruitland formation has hydrogen indexes from rock eval pyrolysis between 100 and 350 and atomic h c ratios between 0 8 and 1 2 oxygen indexes and atomic o c values are less than 24 and 0 3 respectively extractable hydrocarbon yields are as high as 7 000 ppm these values indicate that the coal beds and carbonaceous shales have good potential for the generation of liquid hydrocarbons voids in the coal filled with a fluorescent material that is probably bitumen is evidence that liquid hydrocarbon generation has taken place preliminary oil source rock correlations based on gas chromatography and stable carbon isotope ratios of c15 hydrocarbons indicate that the coals and or carbonaceous shales in the fruitland formation may be the source of minor amounts of condensate produced from the coal beds at relatively low levelsof thermal maturity rm 0 7

critical evaluation of an upper carboniferous tight gas sandstone reservoir analog diagenesis and petrophysical aspects upper carboniferous sandstones are one of the most important tight gas reservoirs in central europe we present data from an outcrop reservoir analog piesberg quarry in the lower saxony basin of northern germany this field based study focuses on the diagenetic control on spatial reservoir quality distribution the investigated outcrop consists of fluvial 4th order cycles which originate from a braided river dominated depositional environment westphalian c d stratigraphy sedimentary thicknesses and exposed fault orientations nnw sse and w e reflect tight gas reservoir properties in the region further north diagenetic investigations revealed an early loss of primary porosity by pseudomatrix formation present day porosity 7 on average and matrix permeability 0 0003 md on average reflect a high temperature overprint during burial the entire remaining pore space is occluded with authigenic minerals predominantly quartz and illite this reduces reservoir quality and excludes exposed rocks as tight gas targets the correlation of petrographic and petrophysical data show that expected facies related reservoir quality trends were overprinted by high temperature diagenesis the present day secondary matrix porosity reflects the telogenetic dissolution of mesogenetic ankerite cements and unstable alumosilicates faults are associated with both sealed and partially sealed veins near the faults indicating localized mass transport around w e striking faults dissolution is higher in leached sandstones with matrix porosities of up to 26 3 and matrix permeabilities of up to 105 md the dissolution of ankerite and lithic fragments around the faults indicates focused fluid flow however a telogenetic origin cannot be ruled out the results of this work demonstrate the limits of outcrop analog studies with respect to actual subsurface reservoirs of the greater area whereas the investigated outcrop forms a suitable analog with respect to sedimentological stratigraphic and structural inventory actual reservoirs at depth generally lack telogenetic influences these alter absolute reservoir quality values at the surface however the temperature overprint and associated diagenetic modification which caused the unusually low permeability in the studied outcrop may pose a reservoir risk for tight gas exploration as a consequence of locally higher overburden or similar structural positions

biodegradation of oil in uplifted basins prevented by deep burial sterilization biodegradation of crude oil by bacterial activity which has occurred in the majority of the earth s oil reserves is known to reduce greatly the quality of petroleum in reservoirs for economically successful prospecting for oil it is therefore important to understand the processes and conditions in geological formations that lead to oil biodegradation although recent studies speculate that bacterial activity can potentially occur up to temperatures as high as 150 degrees c refs 3 4 it is generally accepted that effective petroleum biodegradation over geological timescales generally occurs in reservoirs with temperatures below 80 degrees c ref 2 this appears however to be at odds with the observation that non degraded oils can still be found in reservoirs below this temperature here we compile data regarding the extent of oil biodegradation in several oil reservoirs and find that the extensive occurrence of non biodegraded oil in shallow cool basins is restricted to those that have been uplifted from deeper hotter regions of the earth we suggest that these petroleum reservoirs were sterilized by heating to a temperature around 80 90 degrees c during deep burial inactivating hydrocarbon degrading organisms that occur in the deep biosphere even when such reservoirs are subsequently uplifted to much cooler regions and filled with oil degradation does not occur implying that the sterilized sediments are not recolonized by hydrocarbon degrading bacteria

petroleum inclusions atop unayzah gas condensate reservoir signpost for an undocumented chapter of the arabian basin filling history abstract the carboniferous permian unayzah gas condensate reservoir of the ghazal field in eastern saudi arabia contains abundant oil inclusions indicative of a palaeo oil column the molecular composition of a fluid inclusion rich zone at the top of the reservoir revealed a mid mature biomarker distribution 0 80 vitrinite reflectance equivalent vre that is considerably lower than that of the co occurring reservoired fluid 1 41 vre side chain cracking of the triaromatic steroids evident in the produced condensate is significantly less advanced in the inclusion oil as is also reflected in their alkylnaphthalene distributions the lower maturity signal in the inclusion oil is combined with calcareous related biomarkers that include relatively abundant 30 nor 17 hopane c24 tetracyclic terpane and alkyldibenzothiophenes in contrast to the reservoir hydrocarbon fluid derived from the lower silurian qusaiba shale inclusion gas is enriched in the higher hydrocarbons which might be attributed to a high proportion of oil or wet gas inclusions fluid inclusion ethane and propane 13c are very close to the mean of the produced gases but carbon dioxide 13c is about 5 and methane 13c 2 less negative than the average of the produced ghazal gases which may signify more than one hydrocarbon generation population within the fluid inclusions an earlier contribution into the unayzah reservoir from a non qusaiba source may therefore be inferred to have had preceded the volumetrically more significant and more mature qusaiba charges further research is needed to elucidate the source of this oil charge and its extent which could include deep cambrian or neoproterozoic sources that might be present in the region

carbon isotope fractionation during natural gas generation from kerogen abstract in petroleum exploration it is important to be able to determine the origin of any gas which is found this paper describes a new method of estimating the source type and maturity of a gas based on a rayleigh fractionation model kerogen is divided conceptually into a labile dominantly oil generating fraction and a refractory gas prone component 13 c of methane from either kerogen type and ethane propane and butane for gases from labile kerogen can be defined as a function of 13 c of the gas precursor groups in kerogen a kinetic isotope fractionation factor k and the extent of gas generation the isotopic ratio of the methane precursors relative to bulk kerogen determined from laboratory pyrolysis are 17 5 for labile kerogen and 1 4 for refractory kerogen values for ethane propane and butane from labile kerogen based on field correlations are 4 9 2 2 and 1 6 respectively the corresponding fractionation factors are 0 9892 0 9919 0 9947 and 0 9975 for methane ethane propane and butane respectively from labile kerogen and 0 9984 for methane from refractory kerogen using these parameters summary diagrams are constructed which allow differentiation of these sources from each other and from biogenic gases and cracked oil and recognition of gases of mixed origin if an independent estimate of 13 c for the source kerogen is possible then 13 c of the gas components can be used to estimate maturity in terms of the gas generation index the fraction of gas potential which has been realized

zagros phantom earthquakes reassessed the interplay of seismicity and deep salt flow in the simply folded belt unraveling the contributions of main shock slip aftershocks aseismic afterslip and postseismic relaxation to the deformation observed in earthquake sequences heightens our understanding of crustal rheology triggering phenomena and seismic hazard here we revisit two recent earthquakes in the zagros mountains iran which exhibited unusual and contentious aftereffects the mw 6 earthquakes at qeshm 2005 and fin 2006 are both associated with large interferometric synthetic aperture radar insar signals consistent with slip on steep reverse faults in carbonate rocks of the middle sedimentary cover but small aftershocks detected with local seismic networks were concentrated at significantly greater depths this discrepancy can be interpreted in one of two ways either 1 there is a genuine vertical separation between main shock and aftershocks reflecting a complex stress state near the basement cover interface or 2 the aftershocks delimit the main shock slip and the insar signals were caused by shallow updip afterslip phantom earthquakes with very similar magnitudes mechanisms and geographical positions as the original earthquakes here we show that main shock centroid depths obtained from body waveform modeling which in this instance is the only method that can reveal for certain the depth at which seismic slip was centered strongly support the first interpretation at qeshm microseismic aftershock depths are centered at the level of the hormuz formation an infracambrian sequence of intercalated evaporitic and nonevaporitic sediments these aftershocks may reflect the breaking up of harder hormuz sediments and adjacent strata as the salt flows in response to main shock strain at the base of the cover this work bolsters recent suggestions that most large earthquakes in the zagros are contained within carbonate rocks in the midlower sedimentary cover and that the crystalline basement shortens mostly aseismically

tracing deep fluids in the bozhong sag evidence from integrated petrography and geochemistry data abstract the bozhong sag is a mature exploration area for petroleum in the bohai bay basin china which is a typical oil bearing basin and hosts the penglai pl 19 3 and qinhuangdao qhd 32 6 giant oil fields xue 2018 despite 60 years of hydrocarbon exploration in the basin only few large gas fields have been discovered the discovery of the bozhong bz 19 6 gas field not only indicated that the bozhong sag has great potential for natural gas exploration but also raised questions regarding the formation of large scale natural gas fields in typical oil prone basins and in sapropelic source rocks the present study therefore performs a detailed investigation of the sources and migration pathways of the deep fluids in the bozhong sag area as a means of shedding light into this scientific challenge the bozhong sag is located in the thinnest crust and tectonic transition zone of the bohai bay basin intense extension and thinning of lithosphere led to the upward ejection of deep crust and mantle materials under diapirism improvements in this tectonic setting and the fluid migration path occurred as a result of early faults that were formed by compressive thrust in the indosinian yanshan orogenies in addition to a process of extensional development and reactivation of himalayan faults we obtained cores from 13 wells in the bozhong sag and subsequently observed their petrography and analyzed samples for fluid inclusions also volcanic rock samples were analyzed for major and trace elements and carbonate rock samples were analyzed for 13c 18o and 87sr 86sr previously reported 13cco2 and he isotopic data were are also discussed our results showed that petrography was characterized by thermal fading and hydrothermal breccia around fractures filled with quartz and calcite deep fluid activity was mainly reflected by petrographic assemblages of quartz ankerite pyrite plus calcite and volcanic eruptive rocks that were i enriched with large ion lithophile elements lile ii enriched with light rare earth elements lree iii relatively deficient in high field strength elements hfse and iv relatively deficient heavy rare earth elements hree thermal anomaly events were reflected by the homogenization temperature of fluid inclusions and characteristics of magmatic hydrothermal fluids were exhibited by 13c 18o and 87sr 86sr our findings indicated that deep fluids were mainly derived from the deep parts of the upper mantle and that they were slightly contaminated by crustal materials combining our results with those of previous studies on deep xenoliths and xenolithic fluid compositions in eruptive rocks of eastern china zhang et al 1999 han et al 2008 we interpreted that deep fluid properties in the study region were characterized by high h2 and low total volatile gases we conclude that the deep fluids in the bozhong sag was mainly derived from deep material in the upper mantle and that the fluid activity pattern was aided by the deep fracture fault systems in addition to central and fissure type wide area eruption activities

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

intrusion of lamprophyre dyke and related deformation effects in the host rock salt a case study from the loule diapir portugal abstract a rock salt lamprophyre dyke contact zone sub vertical ne sw strike was investigated for its petrographic mechanic and physical properties by means of anisotropy of magnetic susceptibility ams and rock magnetic properties coupled with quantitative microstructural analysis and thermal mathematical modelling the quantitative microstructural analysis of halite texture and solid inclusions revealed good spatial correlation with ams and halite fabrics the fabrics of both lamprophyre and rock salt record the magmatic intrusion plastic flow and regional deformation characterized by a nw se trending steep foliation ams and microstructural analysis revealed two deformation fabrics in the rock salt 1 the deformation fabrics in rock salt on the nw side of the dyke are associated with high temperature and high fluid activity attributed to the dyke emplacement 2 on the opposite side of the dyke the emplacement related fabric is reworked by localized tectonic deformation the paleomagnetic results suggest significant rotation of the whole dyke probably during the diapir ascent and or the regional tertiary to quaternary deformation

anomalous behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 there have been many reports on ultra low frequency ulf electromagnetic phenomena associated with earthquakes in a very wide frequency range in this study unusual behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 have been reported ratios of diurnal variation range between the target station esashi esa which is about 135 km from the epicenter and the remote reference station kakioka kak about 302 km distant to the epicenter have been computed the results of 10 day running mean of the ratios showed a clear anomaly exceeding the statistical threshold in the vertical component about 2 months before the mega event this anomaly is unique over a 3 year background and the further stochastic test indicates that this anomaly is unlikely a random anomaly which is highly suggestive of correlation with the mega event the original records of geomagnetic fields of the esa station also exhibit continuous anomalous behaviors for about 10 days in the vertical component approximate 2 months prior to the mw9 0 earthquake

methane and the origin of five element veins mineralogy age fluid inclusion chemistry and ore forming processes in the odenwald sw germany abstract five element veins ag bi co ni as have been valuable mineral deposits since medieval times the characteristic occurrence of large aggregates of native metals up to several dm surrounded by a succession of arsenides makes this vein type attractive for mining industry natural history museums and private mineral collectors nevertheless the exact formation process of these specific vein types has not been fully understood this is the first case study applying a new model which includes methane as a reducing agent to two typical examples of such mineralisations from the odenwald sw germany we analysed all mineralogical varieties ag as and bi dominated of the five element veins in the odenwald sw germany in terms of ore textures mineral chemistry fluid inclusion compositions microthermometry and raman spectroscopy stable isotopes c o and s and in situ u pb age dating of calcite and prehnite a variety of ag bi and as dominated native metal arsenide calcite veins sulphide calcite veins and arsenide free ag hg barite veins occurs in the odenwald and has been examined in this study all arsenide veins have in common that up to dm sized often dendritic native metals are overgrown by a succession of arsenides followed by carbonate and finally sulphides the succession of arsenides shows a distinct spatial and temporal chemical trend in their composition this trend evolves from ni to co and finally fe dominated compositions from the core to the rim in contrast spatially closely related ag hg barite veins consist of almost mono mineralic amalgam inter grown with barite in situ u pb age dating of low u calcite and prehnite was applied to constrain the age of hydrothermal mineralisation the results imply that the five element veins formed at 170 180 ma from na ca cl fluids at 290 c salinities of 27 wt and ca ca na of 0 30 to 0 35 in the presence of methane the age data clearly relate the relevant fluid migration to extension and crustal thinning caused by the opening of the north atlantic ternary mixing of a deep seated metal rich basement brine fluid a a sulphide bearing h2s and hs basinal sedimentary brine fluid b and methane dominated fluid gas fluid c induce ore formation mixing of such chemically contrasting fluids results in a strong chemical disequilibrium of the mixed fluid which potentially leads to rapid precipitation of native metals and arsenides with these specific ore textures in contrast sulphide bearing calcite veins formed under similar p t conditions due to mixing of fluid a and b while fluid c was absent additionally u pb analyses of post ore calcite yields ages of 60 ma which indicates that a second calcite formation event is associated with the onset of the upper rhine graben rifting veins with amalgam and barite form as a consequence of post ore oxidation of ag2s at 135 c conspicuously this secondary silver ii has hg contents of up to 30 wt in contrast to hg contents below 1 wt of primary silver i and ag2s the formation of amalgam was most likely related to decrease of the s2 so42 ratio due to cooling of the late hydrothermal fluid resulting in the destabilisation of hg bisulphide complexes in this fluid

fluid and gas migration in the north german basin fluid inclusion and stable isotope constraints fluid inclusions have been studied in minerals infilling fissures quartz calcite fluorite anhydrite hosted by carboniferous and permian strata from wells in the central and eastern part of the north german basin in order to decipher the fluid and gas migration related to basin tectonics the microthermometric data and the results of laser raman spectroscopy reveal compelling evidence for multiple events of fluid migration the fluid systems evolved from a h2o nacl kcl type during early stage of basin subsidence to a h2o nacl cacl2 type during further burial locally fluid inclusions are enriched in k cs li b rb and other cations indicating intensive fluid rock interaction of the saline brines with lower permian volcanic rocks or sediments fluid migration through carboniferous sediments was often accompanied by the migration of gases aqueous fluid inclusions in quartz from fissures in carboniferous sedimentary rocks are commonly associated with co genetically trapped ch4 co2 inclusions p t conditions estimated via isochore construction yield pressure conditions between 620 and 1 650 bar and temperatures between 170 and 300 c during fluid entrapment the migration of ch4 rich gases within the carboniferous rocks can be related to the main stage of basin subsidence and stages of basin uplift a different situation is recorded in fluid inclusions in fissure minerals hosted by permian sandstones and carbonates aqueous fluid inclusions in calcite quartz fluorite and anhydrite are always h2o nacl cacl2 rich and show homogenization temperatures between 120 and 180 c co genetically trapped gas inclusions are generally less frequent when present they show variable n2 ch4 compositions but contain no co2 p t reconstructions indicate low pressure conditions during fluid entrapment always below 500 bar the entrapment of n2 ch4 inclusions seems to be related to phases of tectonic uplift during the upper cretaceous a potential source for nitrogen in the inclusions and reservoirs is corg rich carboniferous shales with high nitrogen content intensive interaction of brines with carboniferous or even older shales is proposed from fluid inclusion data enrichment in li ba pb zn mg and sulfur isotopic compositions of abundant anhydrite from fissures the mainly light 34s values of the fissure anhydrites suggest that sulfate is either derived through oxidation and re deposition of biogenic sulfur or through mixing of so42 rich formation waters with variable amounts of dissolved biogenic sulfide an igneous source for nitrogen seems to be unlikely since these rocks have low total nitrogen content and furthermore even extremely altered volcanic rocks from the study area do not show a decrease in total nitrogen content

some aspects of the late and post variscan development of the northwestern german basin abstract the crust of northern germany can be subdivided into three provinces that are evident by differences in crustal density seismic velocity reflectivity magnetic characteristics thermal history and electric conductivity these provinces are limited by the elbe river and the northern foothills of the mittelgebirge during the pre and post variscan evolution the tectonic setting of northern germany has changed repeatedly each of the three recognized basement provinces differs in the timing of basement consolidation caledonian variscan the sequence of basin development during permian mesozoic and cenozoic times and the timing and intensity of magmatic activity permian cretaceous cenozoic

stable carbon isotopic ratios of ch4 co2 bearing fluid inclusions in fracture fill mineralization from the lower saxony basin germany a tool for tracing gas sources and maturity abstract the stable carbon isotopic ratios 13 c of methane ch 4 and carbon dioxide co 2 of gas rich fluid inclusions hosted in fracture fill mineralization from the southern part of the lower saxony basin germany have been measured online using a crushing device interfaced to an isotopic ratio mass spectrometer irms the data reveal that ch 4 trapped in inclusions seems to be derived from different source rocks with different organic matter types the 13 c values of ch 4 in inclusions in quartz hosted by carboniferous rocks range between 25 and 19 suggesting high maturity coals as the source of methane methane in fluid inclusions in minerals hosted by mesozoic strata has more negative carbon isotope ratios 45 to 31 and appears to represent primary cracking products from type ii kerogens i e marine shales there is a positive correlation between increasing homogenization temperatures of aqueous fluid inclusions and less negative 13 c ch 4 values of in co genetic gas inclusions probably indicating different mtaturity of the potential source rocks at the time the fluids were released the co 2 isotopic composition of ch 4 co 2 bearing inclusions shows slight negative or even positive 13 c values indicating an inorganic source e g water rock interaction and dissolution of detrital marine calcite for co 2 in inclusions we conclude that the 13 c isotopic ratios of ch 4 co 2 bearing fluid inclusions can be used to trace migration pathways sources of gases and alteration processes furthermore the 13 c values of methane can be used to estimate the maturity of the rocks from which it was sourced results presented here are further supported by organic geochemical analysis of surface bitumens which coexist with the gas inclusion rich fracture fill mineralization and confirm the isotopic interpretations with respect to fluid source type and maturity

geochemistry and accumulation of carbon dioxide gases in china we propose the following identification indicators for co2 of different origins based on data obtained from analyzing the molecular composition of 1198 gas samples the co2 carbon isotope values of 390 samples and the helium isotope composition of 256 samples collected from wells of 16 oil and gas bearing basins and gas seepages in china and reviewing literature on organic and inorganic co2 throughout the world co2 is of organic origin if co2 content 13cco22 is of inorganic origin if dgr13cco2 8 pmil or co2 60 and co2 is of either organic or inorganic origin or a mixtur of organic and inorganic origins if 10 pmil 13cco213cco2 values of organic co2 mainly range from 10 to 22 pmil in tectonically stable oil and gas bearing basins where deep faults and magmatism are undeveloped organic co2 occurs almost exclusively in tectonically active oil and gas bearing basins where active faults and magmatism are present or in areas of modern volcanic activity the dgr13cco2 values of inorganic co2 range from 2 to 8 pmil and are distributed along faults the inorganic co2 with a dgr13cco2 value of 0 3 pmil is of metamorphic origin and that with dgr13cco2 values of 6 2 pmil is mantle derived and of magmatic origin in china the dgr13cco2 values of inorganic co2 gas pools range from 3 41 to 8 44 pmil and the helium ratio r ra is 1 which indicates that these gases are typically derived from the mantle

large strain shearing of halite experimental and theoretical evidence for dynamic texture changes abstract we report results from torsion experiments on polycrystalline halite nacl to shear strains 8 and observe a very complex texture evolution the same behavior was reproduced with polycrystal plasticity simulations suggesting that we capture the underlying mechanisms while crystal shapes gradually rotate into the shear plane crystal orientations change continuously and dynamic texture patterns evolve with increasing shear this is highly significant for ultra large deformation as for example implied from geodynamic modeling for the deep earth where seismic anisotropy patterns may develop and locally disappear again as material is deformed during convection the study also suggests that caution is required when interpreting deformation mechanisms from simple shear preferred orientation patterns

rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones emphasized in this paper are the deformation processes and rheologies of rocks at high temperatures and high effective pressures conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones much recent progress has been made in understanding the flexure of the oceanic lithosphere using rock mechanics based yield criteria for the inelastic deformations at the top and base at mid plate depths stresses are likely to be supported elastically because bending strains and elastic stresses are low the collisional tectonic regime however is far more complex because very large permanent strains are sustained at mid plate depths and this requires us to include the broad transition between brittle and ductile flow moreover important changes in the ductile flow mechanisms occur at the intermediate temperatures found at mid plate depths two specific contributions of laboratory rock rheology research are considered in this paper first the high temperature steady state flow mechanisms and rheology of mafic and ultramafic rocks are reviewed with special emphasis on olivine and crystalline rocks rock strength decreases very markedly with increases in temperature and it is the onset of flow by high temperature ductile mechanisms that defines the base of the lithosphere the thickness of the continental lithosphere can therefore be defined by the depth to a particular isotherm tc above which at geologic strain rates the high temperature ductile strength falls below some arbitrary strength isobar e g 100 mpa for olivine tc is about 700 800 c but for other crustal silicates tc may be as low as 400 600 c suggesting that substantial decoupling may take place within thick continental crust and that strength may increase with depth at the moho as suggested by a number of workers on independent grounds put another way the moho is a rheological discontinuity a second class of laboratory observations pertains to the general phenomenon of ductile faulting in which ductile strains are localized into shear zones ductile faults have been produced in experiments of five different rock types and is generally expressed as strain softening in constant strain rate tests or as an accelerating creep rate stage at constant differential stress a number of physical mechanisms have been identified that may be responsible for ductile faulting including the onset of dynamic recrystallization phase changes hydrothermal alteration and hydrolytic weakening microscopic evidence for these processes as well as larger scale geological and geophysical observations suggest that ductile faulting in the middle to lower crust and upper mantle may greatly influence the distribution and magnitudes of differential stresses and the style of deformation in the overlying upper continental lithosphere

thermal maturity limit for primary thermogenic gas generation from humic coals as determined by hydrous pyrolysis hydrous pyrolysis experiments at 360 c 680 f for 72 h were conducted on 53 humic coals representing ranks from lignite through anthracite to determine the upper maturity limit for hydrocarbon gas generation from their kerogen and associated bitumen i e primary gas generation these experimental conditions are below those needed for oil cracking to ensure that generated gas was not derived from the decomposition of expelled oil generated from some of the coals i e secondary gas generation experimental results showed that generation of hydrocarbon gas ends before a vitrinite reflectance of 2 0 this reflectance is equivalent to rock eval maximum yield temperature and hydrogen indices his of 555 c 1031 f and 35 mg g total organic carbon toc respectively at these maturity levels essentially no soluble bitumen is present in the coals before or after hydrous pyrolysis the equivalent kerogen atomic h c ratio is 0 50 at the primary gas generation limit and indicates that no alkyl moieties are remaining to source hydrocarbon gases the convergence of atomic h c ratios of type ii and i kerogen to this same value at a reflectance of indicates that the primary gas generation limits for humic coal and type iii kerogen also apply to oil prone kerogen although gas generation from source rocks does not exceed vitrinite reflectance values greater than trapped hydrocarbon gases can remain stable at higher reflectance values distinguishing trapped gas from generated gas in hydrous pyrolysis experiments is readily determined by of the hydrocarbon gases when a depleted water is used in the experiments water serves as a source of hydrogen in hydrous pyrolysis and as a result the use of depleted water is reflected in the generated gases but not pre existing trapped gases

creep of rocksalt abstract a review is presented of the fundamental flow properties and processes in experimentally deformed natural and synthetic halite single crystals and polycrystalline aggregates included in the summary are discussions of a microstructures induced during steady state creep b creep rupture of rocksalt c experiments associated with project salt vault and more recent field studies and d brine migration a representative steady state flow law determined for natural aggregates and maximum natural deviatoric stresses deduced from subgrain sizes are applied briefly to considerations of creep in waste repositories and of salt dome dynamics while the mechanical behavior of rocksalt is probably better understood than for all other rock types further investigations especially on load path stress history and creep rupture are clearly mandated furthermore additional investigations of brine migration and of bench and field scale deformations are needed the latter incorporating realistic rocksalt flow properties into numerical simulations of natural rock mass response

rheological behaviour of synthetic rocksalt the interplay between water dynamic recrystallization and deformation mechanisms abstract the ductile deformation of rocks in nature can be greatly enhanced by the presence of water part of the water induced weakening of rocks at depth may come from fluid assisted deformation or recrystallization mechanisms that are absent in dry rocks in this study we investigate the effect of water on the rheological behaviour of rocksalt we focus on quantification of the contribution of individual deformation and recrystallization mechanisms to deformation we also aim to calibrate a flow law that incorporates the effect of all the relevant microphysical processes and hence more accurately describes the flow of rocksalt in nature for this purpose the mechanical behaviour and microstructural evolution of synthetic rocksalt samples that are similar except for differences in water content determined using ftir analysis are investigated the samples are deformed to natural strains of 0 07 0 46 at 50 mpa confining pressure strain rates of 5 10 7 1 10 4 s 1 and temperatures of 75 240 c resulting in flow stresses of 7 22 mpa the flow stress of samples with a water content below 5 ppm dry is higher than that of samples with a water content of 9 46 ppm wet at all strains under the investigated conditions the difference in flow stress can be explained as due to the operation of only work hardening dislocation creep without dynamic recrystallization in the dry material versus combined dislocation and solution precipitation creep plus fluid assisted grain boundary migration in the wet material the results allow us to calibrate a flow law for wet rocksalt that incorporates the effects of solution precipitation creep and fluid assisted grain boundary migration the results also suggest that strain localization in natural rocksalt is more likely to be localized due to fluid infiltration and associated rheological weakening than due to progressive removal of strain hardening substructure by grain boundary migration

organic geochemistry and mineralogy i characterisation of organic matter associated with metal deposits abstract as geochemical appraisals of mineral regions of commercial prospectivity evolve the organic matter associated with metal rich ores has attracted greater attention petroleum basin and modern seafloor hydrothermal vent studies have suggested that organic matter can have a significant influence on the behaviour of mineralising fluids there have been many isolated reports of certain organic compositional or morphological e g pyrobitumen features showing an apparent relationships with hydrothermal fluids or minerals raising expectations that organic based parameters might be useful to mineral exploration however the understanding of organic inorganic relationships in earth systems is far from complete for example the detailed mechanics of the interaction of organics with hydrothermal fluids over geological time remain largely undefined organic geochemistry studies have traditionally involved the measurement and interpretation of the hydrocarbon composition of sedimentary rocks here we review the types of aliphatic hydrocarbons aromatic hydrocarbons and metalloporphyrins often detected from organic geochemical investigations in mineral rich regions such molecular data can be particularly diagnostic of biochemical sources and the palaeo environments at the time mineral associated organic matter was deposited sub surface trends of hydrocarbon alteration may also reflect major biogeochemical processes such as thermal maturity and biodegradation organic geochemistry data can also occasionally provide information about the nature e g origin composition temperatures and migration pathways of hydrothermal fluids and can make a contribution to holistic ore genesis models the well preserved organic matter associated with the economic here s your chance pb zn ag mine paleoproterozoic barney creek formation mcarthur basin australia and the transition metal rich early permian kupferschiefer formation germany poland have attracted significant attention a more detailed summary of the organic character of these deposits is provided to highlight the contribution organic geochemistry can make to understanding mineralisation processes most organic geochemical studies of highly mineralised regions however have not adequately addressed the significance of organic matter to mineralisation a slightly different analytical focus than traditionally used for exploration appraisal of petroleum hydrocarbons may be required to properly evaluate the significance of organic species to the mobilisation transport and deposition of ore metals the characterisation and subsequent thermodynamic modeling of organic substances and complexes within metalliferous hydrothermal systems will contribute to a better understanding of the nature and role of organic inorganic fluids or other affiliated organics in ore systems

from shale oil to biogenic shale gas retracing organic inorganic interactions in the alum shale furongian lower ordovician in southern sweden methane rich gas occurs in the total organic carbon rich alum shale furongian to lower ordovician in southern sweden the lower part of the thermally immature alum shale was impregnated by bitumen locally generated by heating from magmatic intrusions from the carboniferous to the permian organic geochemical data indicate that the migrated bitumen is slightly degraded in the upper alum shale where methane is the main hydrocarbon in thermovaporization experiments centimeter size calcite crystals occur that contain fluid inclusions filled with oil gas or water the alum shale is thus considered a mixed shale oil biogenic shale gas play the presented working hypothesis to explain the biogenic methane occurrence considers that water soluble bitumen components of the alum shale were converted to methane a hydrogeochemical modeling approach allows the quantitative retracing of inorganic reactions triggered by oil degradation the modeling results reproduce the present day gas and mineralogical composition the conceptual model applied to explain the methane occurrence in the alum shale in southern sweden resembles the formation of biogenic methane in the antrim shale michigan basin united states in both models melting water after the pleistocene glaciation and modern meteoric water may have diluted the contents of total dissolved solids tds in basinal brines such pore waters with low tds contents create a subsurface aqueous environment favorable for microbes that have the potential to form biogenic methane today biogenic methane production rates with shale as the substrate using different hydrocarbon degrading microbial enrichment cultures in incubation experiments range from 10 to 620 nmol per gram and per day

technical note on the strength of copper versus polymer jackets in torsion tests on halite up to 300 c abstract when deforming soft materials in torsion like halite aggregates at temperatures up to 300 c the strength of the jacket must be taken into account because the most external part of the assembly supports most of the torque therefore we carried out mechanical tests on non annealed copper jackets of 15 mm internal diameter and 0 25 mm wall thickness the results show that this metal supported large torques up to 300 c ca 18 nm at 100 c 17 nm at 200 c and 9 nm at 300 c if the purpose is to deform soft rocks alternative materials such as polymers should therefore be used at 250 mpa confining pressure and 100 c the strength of the tested polymers was below the detection limit of the internal load cell 1 nm the present results also show that when deforming soft rock as halite in torsion correction for copper strength is valid for 100 c at 200 and 300 c copper became much stronger than halite and the stress strain curves do not represent the sum of the halite and copper strengths thus making the correction for copper strength not possible in contrast testing using polymers does not need any torque corrections the results of our testing indicate that polyethylene pe and polytetrafluorethylene ptfe are the most appropriate materials to serve as jackets for temperatures

short term earthquake prediction current status of seismo electromagnetics abstract loss of human lives as a result of earthquakes is caused overwhelmingly by the collapse of buildings within less than a few minutes of main shocks the most urgent countermeasure consists of two key elements one is strengthening of weak structures and the other is short term earthquake prediction short term prediction needs precursors although some promising precursors are reported the prevailing views in japan and elsewhere are overly pessimistic the pessimism largely roots in the fact that short term precursors are generally non seismic and tools developed for seismology are not designed to detect them nonetheless nationally funded large scale earthquake prediction programs always emphasize the need to reinforce seismometer networks they do not take into account the views of those in the science community who point to the importance of non seismic precursors while there are well founded causes to be skeptical the situation needs to be improved one reason for skepticism is that the observations of precursors have not yet been perfect enough and another is that some important fundamental aspects of non seismic precursors are still unresolved we review some of these problems

reduction of electron temperature in low latitude ionosphere at 600 km before and after large earthquakes 1 we examine ionospheric electron temperatures te observed by hinotori satellite during three earthquakes m6 6 occurred in november 1981 m7 4 and m6 6 in january 1982 over philippine respectively it is found that t e around the epicenters significantly decreases in the afternoon periods within 5 days before and after the three earthquakes the region of ionosphere disturbance extends to 80 120 degrees in longitude a tendency exists that duration of the disturbance becomes longer as the increase of earthquake magnitude f 2 peak frequency f o f 2 and virtual height h f from a chain of 4 ionosonde stations located in the longitude zone of 120 e 130 e are used together with electron density n e that is observed simultaneously onboard hinotori satellite to find possible cause mechanisms of the abnormal reduction of electron temperatures behavior of hinotori t e n e and ionosonde f o f 2 h f implies the existence of westward electric field over epicentre our finding suggests that simple two plasma instruments might be able to play a fundamental role to study ionosphere disturbance associated with earthquake if the constellation of small mini satellites is organized and the orbits are properly chosen

stable carbon isotope ratios of ch4 rich gas inclusions in shale hosted fracture fill mineralization a tool for tracing hydrocarbon generation and migration in shale plays for oil and gas abstract fluid inclusion gases in minerals from shale hosted fracture fill mineralization have been analyzed for stable carbon isotopic ratios of ch 4 using a crushing device interfaced to an isotope ratio mass spectrometer irms the samples of paleozoic strata under study originate from outcrops and wells in the rhenish massif and campine basin harz mountains and the upper slope of the southern permian basin fracture fill mineralization hosted by mesozoic strata was sampled from drill cores in the lower saxony basin some studied sites are candidates for shale gas exploration in germany samples of mesozoic strata are characterized by abundant calcite filled horizontal fractures which preferentially occur in toc rich sections of the drilled sediments only rarely are vertical fractures filled with carbonates and or quartz in drill cores from mesozoic strata but in paleozoic shale they occur frequently the 13 c ch 4 values of fluid inclusions in calcite from horizontal fractures hosted by mesozoic strata suggest that gaseous hydrocarbons were generated during the oil early gas window and that the formation of horizontal fractures seems to be related to hydraulic expulsion fracturing the calculated maturity of the source rocks at the time of gas generation lies below the maturity derived from measured vitrinite reflectance thus the formation of horizontal fractures and trapping of gas that was generated in the oil and or early gas window obviously occurred prior to maximal burial rapidly increasing vitrinite reflectance data seen locally can be explained by hydrothermal alteration as indicated by increasing 13 c ch 4 co 2 values in fluid inclusions the formation of vertical fractures in studied mesozoic sediments is related to stages of post burial inversion gas rich inclusions in fracture filling minerals recorded the migration of gas that had probably been generated instantaneously rather than cumulatively from high to overmature source rocks since no evidence is given for the presence of early generated gas in studied paleozoic shale it appears likely that major gas loss from shales occurred due to deformation and uplift of these sediments in response to the variscan orogeny

current affairs in earthquake prediction in japan abstract as of mid 2014 the main organizations of the earthquake eq hereafter prediction program including the seismological society of japan ssj the mext headquarters for eq research promotion hold the official position that they neither can nor want to make any short term prediction it is an extraordinary stance of responsible authorities when the nation after the devastating 2011 m9 tohoku eq most urgently needs whatever information that may exist on forthcoming eqs japan s national project for eq prediction started in 1965 but it has made no success the main reason for no success is the failure to capture precursors after the 1995 kobe disaster the project decided to give up short term prediction and this stance has been further fortified by the 2011 m9 tohoku mega quake this paper tries to explain how this situation came about and suggest that it may in fact be a legitimate one which should have come a long time ago actually substantial positive changes are taking place now some promising signs are arising even from cooperation of researchers with private sectors and there is a move to establish an eq prediction society of japan from now on maintaining the high scientific standards in eq prediction will be of crucial importance

using petroleum inclusions to trace petroleum systems a review abstract petroleum bearing fluid inclusions are small encapsulations of oil and gas that offer an invaluable opportunity to better constrain the evolution of petroleum systems insights into palaeo fluid compositions complement observations on present day fluid compositions which represent only the end point of complex cumulative processes throughout basin history in this contribution we review a wide range of approaches used to extract geochemical information from petroleum inclusions and how these can be used to better constrain petroleum systems these techniques can be grouped into optical spectrographic and thermometric non destructive methods or destructive chemical analyses of bulk samples or individual inclusions typically optical methods documenting the distribution and visual properties of petroleum inclusions are used to provide petrographic context for subsequent specialised geochemical analyses of petroleum inclusions additional non destructive techniques such as raman spectroscopy can then be applied to provide some further insights into the composition of the trapped fluids although the complex nature of petroleum generally requires direct access to the fluid for a more complete understanding of geochemical aspects a variety of destructive techniques have been developed initially to analyse bulk samples released by mechanical crushing and more recently through ablation type techniques that allow the composition of individual inclusions to be characterised screening geochemical techniques that utilise mechanical crushing of bulk samples to analyse petroleum inclusions using mass spectrometry without prior chromatographic separation have become routine analyses other geochemical techniques more geared towards detailed molecular information such as biomarkers utilise chromatographic separation prior to mass spectrometry evaluation of the isotopic composition of petroleum inclusions is also possible for both bulk samples and compound specific analyses the use of lasers to open individual inclusions allows the released contents to be analysed by thermal extraction gas chromatography mass spectrometry gc ms or mass spectrometric mapping of minerals using time of flight secondary ion mass spectrometry tof sims a surface sensitive analytical method that uses ion beams to ablate into minerals the continued evolution of techniques to analyse the incredibly small volume of hydrocarbons trapped within fluid inclusions has progressed to a point where there is little that can be done to evaluate a live oil or gas sample that cannot be achieved for a fluid inclusion sample the full power for tracing petroleum systems is however only realised where there is an effective integration of fluid inclusion data with a more conventional approach to petroleum systems analysis

mechanics microstructure and ams evolution of a synthetic porphyritic calcite aggregate deformed in torsion in order to investigate the mechanical microstructural and ams evolution of porphyritic mylonites we made a synthetic aggregate composed of 70 fine calcite 3 mm in length defined a conspicuous

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

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

deformation related recrystallization processes abstract recrystallization is a common microstructural transformation that occurs during deformation metamorphism and diagenesis of rocks studies on minerals and rock analogues have demonstrated that a wide range of recrystallization mechanisms can occur the range of mechanisms is related to the various ways in which two basic processes grain boundary migration and new grain boundary formation combine to transform the microstructure two recent papers drury et al 1985 urai et al 1986 have proposed different schemes for the description of recrystallization mechanisms the purpose of this paper is to provide a unified framework for the description of mechanisms recrystallization mechanisms are divided into three main types rotation mechanisms which principally involve the formation of new grain boundaries migration mechanisms which principally involve grain boundary migration and general mechanisms which involve both basic processes a further distinction is made on the basis of the continuity of the microstructural transformation with respect to time each of the three main types of mechanism can be divided into a number of sub types depending on whether the processes of grain boundary migration new grain boundary formation and new grain formation occur in a discontinuous or continuous manner with respect to time as the terms continuous and discontinuous have been used in the metallurgical literature to signify the spatial continuity of the microstructural transformation the terms discontinuai and continual are used to refer to the temporal continuity of the transformation it is recommended that the following aspects should be specified if possible in a general description of recrystallization mechanisms 1 1 how do the basic processes combine to transform the microstructure 2 2 if new grain development occurs what is the development mechanism and does new grain formation occur in a continual or discontinuai manner 3 3 if grain boundary migration is involved in the transformation what is the migration mechanism i e fast solute escape migration slow solute loaded migration fluid assisted migration etc and is migration a continual or discontinuai process the application of the unified scheme is illustrated by reviewing studies that have provided detailed information on the recrystallization mechanisms involved the complicating effects of solid solution impurities dispersed second phase particles and grain boundary fluid films are also considered and it is demonstrated that variations in content of these types of impurity can significantly effect the types of recrystallization that occur in a given material

transient and steady state deformation of synthetic rocksalt abstract synthetic rocksalt with a porosity less than 2 5 and an average grain size of about 0 35 mm was made by warm pressing at 100 c 150 mpa and for 15 min cylinders of this material 25 mm in diameter by 50 mm long were deformed at strain rates of 0 1 ksec 1 at confining pressures of 20 50 100 and 200 mpa and at temperatures of 100 200 and 300 c the resulting stress time data show transient stress behavior before steady state stress occurs very little variation in the stress time data occurs for the above confining pressures at a constant temperature many of the tests reach steady state at 10 strain where all the experiments were terminated the differential stress at 10 varies from about 22 mpa at 100 c to about 6 mpa at 300 c these strengths are slightly less than those measured by heard 1972 also on synthetic polycrystalline rocksalt and are similar to those measured by wawersik and hannum 1980 and by hansen and mellegard 1980 in modified creep tests on coarse grained natural rocksalt under similar pressure and temperature conditions activation energies computed from these steady state stresses vary between 7 5 and 25 kcal mole and are consistent with those obtained by heard 1972 and by parrish and gangi 1977 1981 the stress time data were fit using one and two mechanism transient stress functions which assume independent mechanisms or processes the rms errors decrease from about 1 mpa for the one mechanism fits to about 0 2 mpa for the two mechanism fits indicating at least two mechanisms are operative in these tests similar one and two mechanism fits were made to creep tests performed by w wawersik et al on new mexico bedded rocksalt similar improvements in the fits were obtained for those tests that lasted long enough so that the effect of a second mechanism could be noted it was found that the steady state strain rate found in creep tests could be interpreted as the beginning of another mechanism this raises the question of whether the steady state phenomena exist at all or whether it is just an approximation to a mechanism with a time constant that is long compared to the length of the test