the 2004 sumatra tsunami in the southeastern pacific ocean new global insight from observations and modeling the 2004 sumatra tsunami was an unprecedented global disaster measured throughout the world oceans the present study focused on a region of the southeastern pacific ocean where the westward circumferentially propagating tsunami branch converged with the eastward branch based on data from fortuitously placed chilean dart 32401 and tide gauges along the coast of south america by comparison of the tsunami and background spectra we suppressed the influence of topography and reconstructed coastal spectral ratios that were in close agreement with a ratio at dart 32401 and spectral ratios in other oceans findings indicate that even remote tsunami records carry spectral source signatures birth marks the 2004 tsunami waves were found to occupy the broad frequency band of 0 25 10 cph with the prominent ratio peak at period of 40 min related to the southern fast slip source domain this rupture hot spot of 350 km was responsible for the global impact of the 2004 tsunami data from dart 32401 provided validation of model results the simulated maximum tsunami wave height of 2 25 cm was a conservative approximation to the measured height of 2 05 cm the computed tsunami travel time of 25 h 35 min to dart 32401 although 20 min earlier than the actual travel time provided a favorable result in comparison with 24 h 25 min estimated from classical kinematic theory the numerical simulations consistently reproduced the wave height changes observed along the coast of south america including local amplification of tsunami waves at the northern stations of arica 72 cm and callao 67 cm

the nonseismic tsunami observed in the bulgarian black sea on 7 may 2007 was it due to a submarine landslide 1 a tsunami like sea disturbance of nonseismic origin was observed on 7 may 2007 on the bulgarian black sea coast the maximum wave amplitude was three meters and the sea oscillations lasted for several hours the anomalous behaviour was seen in many places of the coast of bulgaria and was stronger in the north several accounts of eyewitnesses as well as reports of local port authorities and three tide gauge recordings are available and have been collected and analysed the tsunami could have been produced by a submarine landslide or by atmospheric pressure pulses here we explore the former hypothesis i e the possibility that the tsunami was induced by a landslide that may have occurred on the shelf margin off bulgaria by making use of numerical modelling we find that submarine mass movements taking place within a certain delimited source area off bulgaria may have generated tsunamis compatible with the observations

igneous and metamorphic petrology of the eclogitic seljeneset meta anorthosite and related jotunites western gneiss region norway abstract the seljeneset meta anorthosite consists of deformed and metamorphosed anorthosite and mafic rocks is situated in the high grade western gneiss region wgr of norway and is adjacent to the 1 52 ga flatraket quartz monzonite mangerite the wgr was metamorphosed to eclogite fades during caledonian tectonism 414 16 ma ago the meta anorthosite contains 46 57 wt sio 2 and displays chondrite normalized ree patterns typical of anorthosite indicating that metamorphism did not significantly affect ree abundances norms indicate that igneous anorthosite consisted of 90 modal plagioclase minor mafic silicates and 1 fe ti oxide mafic rocks 43 48 wt sio 2 are rich in total fe 2 o 3 13 20 tio 2 3 4 and p 2 o 5 1 3 poor in cr jotunites which are characteristic of proterozoic anorthosite mangerite complexes jotunite originally consisted of 50 modal andesine 25 mafic silicates 10 fe ti oxide and up to 7 apatite ree patterns of jotunite are highly variable which reflects variable igneous abundances and modification by metasomatism filter pressing of residual liquid trapped between cumulus plagioclase may have been important in the evolution of anorthosite and jotunite anorthosite contains ultramafic xenoliths high mgo cr and ni and depleted in lree which suggests that some mantle derived peridotite was present in the baltic crust by mid proterozoic time this may extend the crustal history of norwegian garnet peridotites by over one billion years seljeneset rocks display evidence of retrogression from eclogite through amphibolite facies meta anorthosite consists of ovoidal clots of margarite quartz plagioclase and relict kyanite set in a matrix of zoisite clinozoisite plagioclase quartz hornblende and biotite phase equilibria analysis of sequential assemblages shows that meta anorthosite records a retrograde p t path from 15 17 kbar to 4 3 8 2 kbar at 450 600 c mafic rocks vary from moderately well preserved eclogite through varieties containing symplectite to dynamically recrystallized amphibolite in one sample the rare na ca amphibole magnesio alumino taramite appears to be part of the eclogite assemblage calculations indicate eclogite formation at p 16 18 kbar at 750 c some mafic rocks contain veins and segregations of biotite muscovite pyrite allanite and zircon that considered together with geochemical data indicate metasomatic introduction of k rb ba ga s and rare earth and other high field strength elements by channelized fluids during retrogression the seljeneset meta anorthosite associated jotunites and adjacent flatraket quartz monzonite likely constitute a single complex here named the nordpollen plutonic complex this complex was emplaced 1 52 ga ago metamorphosed to eclogite facies during silurian continent continent collision largely retrograded to amphibolite facies during uplift of the orogen and locally metasomatised during retrogression

magmatic and metamorphic controls on chemical variations within the eiksunddal eclogite complex sunnmore western norway the eiksunddal eclogite complex is one of the larger group b country rock eclogites within the western gneiss region wgr of norway whole rock chemical data suggest a magmatic origin for the rocks within the eclogite complex the chemical variations among the eclogitic rocks were controlled by accumulation of olivine fo80 and plagioclase an70 and probably magnetite the composition of the interstitial trapped liquid is derived by linear regression methods and is a high al orthopyroxene normative basalt the most likely conditions of crystallization are t 1150 c p 10 kbar the al rich nature of the interstitial liquid may have implications for the formation of anorthosites and leucogabbros associated with similar mafic rocks elsewhere in the wgr trace element characteristics are compatible with a continental origin of these rocks during the subsequent metamorphic history the marginal parts of the complex have suffered variable degrees of contamination abundant amphibole inclusions in large garnets in garnet websterites suggest local hydration at pre eclogitic stages this may be associated with introduction of radiogenic sr as previously reported by w l griffin and h k brueckner during prograde metamorphism alkali exchange occurred during growth of garnet clinopyroxene and biotite at the expense of pargasitic amphibole and orthopyroxene the most extensive metasomatism however was probably associated with the introduction of fluid during amphibolitization retrogression of the eclogitic rocks three model reactions eqs 5 7 qualitatively explain the relation between degree of retrogression and the observed metasomatic effects whether si and ca are gained or lost during retrogression seems to be controlled by the extent of amphibole growth in diopside plagioclase symplectites initially formed by breakdown of omphacite alumina has behaved in a more or less immobile way during metasomatism low mobility of al is also reflected by the formation of subsilic al rich amphiboles and al rich plagioclase during garnet breakdown this demonstrates the importance of kinetic factors in controlling mineral chemistry

formation of nanoporous pyrobitumen residues during maturation of the barnett shale fort worth basin abstract hydrocarbon generation reactions occur within organic rich shales as a response to thermal maturation here we report observations on samples from the organic rich mississippian barnett shale gas system fort worth basin texas usa at varying stages of thermal maturation a multiscale characterization was achieved using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm and transmission electron microscopy tem we document the chemical evolution of the macromolecular structure of barnett shale kerogen with increasing maturity from an immature kerogen containing a significant aliphatic component and an important concentration of oxygen and sulfur containing functional groups to an overmature kerogen dominated by poorly condensed aromatic structures in addition to the presence of bitumen in samples of oil window maturity very likely genetically derived from thermally degraded kerogen the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by secondary cracking of bitumen compounds

post oil solid bitumen network in the woodford shale usa a potential primary migration pathway abstract an important if not predominant component of porosity in many gas shales has been identified in organic matter an organic network in shales has been described in the literature as organic matter generalized term kerogen primary or bitumen secondary recognition of the type and origin of an organic network in shales has relevance in establishing the origin and timing of porosity and fracture development the pervasive nature of the organic network adopting the shape of pores in type ii kerogen rich woodford shale suggests it is the residue of primary oil migration we use the term post oil solid bitumen to distinguish this bitumen occurrence from pre oil solid bitumen defined as a precursor of oil three forms of this post oil solid bitumen network are recognized in reflected white light at 500 magnification and confirmed in backscattered scanning electron microscope images at 2500 magnification namely speckled 1 2 m wispy 2 5 m and connected 5 m the post oil solid bitumen network demonstrates the prior occurrence of oil generation and migration within this hydrocarbon source rock provides porosity for hydrocarbon storage sites and forms hydrocarbon migration pathways

eclogite facies relics and inferred ultrahigh pressure metamorphism in the north dabie complex central eastern china mineral assemblages and microstructures of a newly identified retrogressed eclogite sensu lato in the north dabie complex ndc central eastern china indicate early very high pressure metamorphic relics preserved in a dominant amphibolite facies host where no eclogite sensu stricto has been positively identified before the investigated eclogitic rock shows distinct multistage recrystallization with granulite and amphibolite facies assemblages overprinting eclogite facies relics the minimum temperature for the eclogite facies metamorphism is estimated to be 800 820 c a spectacular microstructure of oriented quartz needles 2 20 m wide 5 200 m long in matrix ca na clinopyroxene implies the prior existence of a non stoichiometric supersilicic omphacite stabilized at ultrahigh pressure uhp 25 kbar conditions although no coesite or coesite pseudomorphs have been found in the samples the absence of coesite may be due to the lack of free silica at uhp conditions or the consumption of silica during retrograde reactions the inferred uhp conditions metamorphism is further supported by sm nd ages that are equivalent to triassic metamorphic ages from uhp eclogites in the southeastern dabie mountains this finding expands the uhp terrane northward about 50 km spatial distribution of subduction collision related uhp rocks includes parts of the ndc

geochemistry of the extremely high thermal maturity longmaxi shale gas southern sichuan basin abstract the marine shale of the silurian longmaxi formation in southern sichuan basin china is characterized by its huge thickness 100 600 m high toc values 0 35 18 4 favorable types of organic matter i and ii1 high ro values 1 8 4 2 abundant brittle minerals average 56 3 and strong gas generation intensity particularly its bottom section which has toc 2 and thickness of 20 70 m has recently been a main target for shale gas exploration and development geochemical parameters of 13 gas samples from longmaxi shale from 10 wells were analyzed in this study wetness of the gas molar fraction of ethane through pentanes in total gaseous hydrocarbon is only 0 24 0 70 making the longmaxi shale gas among the driest in the world carbon isotopic compositions of the alkane gases from longmaxi shale are characterized by 13c1 13c2 13c3 with the most positive 13c1 values in the world a positive relationship was observed between its 13c1 and 13c2 values reflecting the extremely high thermal maturity of the source rock 2hch4 values range from 140 to 151 and the 2hc2h6 values range from 130 to 173 the hydrogen isotopic compositions were mainly characterized by 2hch4

a gabbro to eclogite transition on flemsoy sunnmore western norway the migmatitic gneisses on the nordoyane islands western norway enclose abundant inclusions of coronitic gabbros and different types of country rock eclogites gabbros on flemsoy show a prograde step wise transition to eclogite via a transitional stage in which garnet and orthopyroxene form coronas between igneous olivine and sodic plagioclase relics after igneous plagioclase cumulates eclogitization proceeds by a complex set of continuous and discontinuous reactions opx and spinel form as transient phases but are consumed in various omphacite forming reactions during eclogite recrystallization relict igneous clinopyroxene shows a continuous increase in jd content while garnet becomes less calcic and more homogeneous from the corona stage to recrystallized eclogite the reactions are strongly diffusion controlled and have been enhanced locally by oxidation and the presence of a fluid phase and deformation while low strain areas of the gabbros remained coronitic whole rock chemistry mineral parageneses and calculated p t conditions are similar for the gabbroeclogites and two types of country rock eclogites some of the layered country rock eclogites appear to have been derived from the coronite bodies p estimates are in the order 15 20 kbar while kgarcpxd values suggest maximum t values of 750 60 c for the eclogite metamorphism in the area

a review and technical summary of the aapg hedberg research conference on origin of petroleum biogenic and or abiogenic and its significance in hydrocarbon exploration and production a research conference originally scheduled as a hedberg research conference examining the origins of oil and gas was held in calgary june 2005 this report summarizes the 14 presentations made at the conference which discussed data and evidence regarding the abiogenic and biogenic origins of petroleum in addition the postpresentation discussion is summarized multiple concepts for the abiogenic formation of petroleum were presented these concepts fell mostly into two broad families mantle degassing associated with the polymerization of low molecular weight compounds and serpentization in association with fischer tropsch reactions the fischer tropsch reactions are catalyzed reactions in which carbon monoxide and hydrogen are converted into hydrocarbons the presentations on the biogenic origin presented a uniform model in which sedimentary organic matter is thermally converted to oil and gas little common ground was found to exist between the abiogenic and biogenic schools of petroleum formation with the possible exception of the importance of fluid flow in controlling the formation of hydrocarbon accumulations although few if any conference participants changed their perspectives most concluded that the meeting was informative and a useful exercise

importance of fracturing during retro metamorphism of eclogites presented textural and petrological data show that the deep to intermediate continental crust may fracture and that microfractures are the locus of fluid and mass transfer necessary for retrograde metamorphism kyanite eclogites from ulsteinvik norway underwent partial retrogression to granulite and amphibolite facies assemblages during near isothermal exhumation from depths equivalent to more than 2 0 gpa at temperatures of 700 800 c plagioclase bearing assemblages rich in hydrous phases formed along margins of eclogite lenses and along mesoscopic fracture systems hydrated zones are from 1 50 cm thick with adjacent wall rock eclogite replaced by symplectites at a low degree of reaction the secondary minerals in the wall rock are found along intra and intergranular microfractures typically 50 100 m wide minerals filling the microfractures include orthopyroxene plagioclase spinel in garnet plagioclase sapphirine plagioclase corundum and plagioclase spinel in kyanite and diopside plagioclase in omphacite the microfractures are often arranged en echelon and are connected through microfaults releasing bends filled with amphibole and spinel form along microfaults in garnet the faulting and fracturing caused localized chemical change in garnet the damage zones close to faults are enriched in feo and mno with steep compositional gradients 8 wt feo over 20 m these feo and mno enriched zones form wedge like structures around the tip of the faults horsetail structures and rose or flame like structures at sticking points along faults they may represent examples of stress induced chemical transport during fracture propagation the change from dry to amphibole bearing assemblages at the tip of the fracture and fractures ending in splays of fluid inclusions trails reflect the involvement of a fluid phase during fracture propagation this suggests that the dry granulite facies retrogression was also driven by fluid infiltration and that metamorphism at depth in collision zones may not be controlled by pressure and temperature alone

carbon isotopic fractionation by desorption of shale gases abstract geochemical studies of shale gas and conventional reservoirs within the triassic yanchang formation of xiasiwan and yongning field ordos basin show that methane is isotopically depleted in 13 c as compared to 13 c 1 calculated by the ro based on the relationship between 13 c 1 and ro geochemical fractionation during the adsorption desorption process of shale system may play a significant part in influencing 13 c 1 values of shale gas two shale core samples from confined coring of the yanchang formation were adopted segmented desorption experiments to examine this phenomenon the results show that the 13 c 1 of desorbed gas changes little in the first few phases of the experiments at low desorption levels but become less negative rapidly when the fraction of desorbed methane exceeds 85 the desorption process for the last 15 fraction of the methane from the shale samples shows a wide variation in 13 c 1 from 49 to 33 9 moreover 13 c 1 of all desorbed methane from the shale samples is substantially depleted in 13 c than that calculated by ro according to stahl and carey s 13 c 1 ro equation for natural gas generated from sapropelic organic matter this shows some gases with isotopically enriched in 13 c cannot be desorbed under the temperature and pressure conditions of the desorption experiments this observation may be the real reason for the 13 c 1 of shale gases and conventional reservoirs becomes more negative in xiasiwan and yongning fields ordos basin the magnitude of the deviation between the 13 c 1 of shale gas and that calculated by ro may be related to the adsorption capacity of shale or the proportion of absorbed gases in this way we may be able to evaluate the relative adsorption capacity of shale in geological conditions by 13 c 1 of the shale gas or by 13 c 1 of conventional gas which generated by the shale with certainty the 13 c 1 of conventional gas in dingbian and yingwang fields have no deviation because the toc value of the hydrocarbon source rock is relatively low

numerical modelling of the destructive meteotsunami of 15 june 2006 on the coast of the balearic islands a destructive tsunami like event locally known as rissaga waves occurring on 15 june 2006 in ciutadella harbour menorca balearic islands is reproduced by a numerical model forced by a travelling atmospheric disturbance the disturbance is reconstructed from microbarograph measurements being the only available instrumental data at the time of the event the model is verified based on two weaker 1997 events which were recorded by a number of bottom pressure recorders operating at that time on the menorca shelf in ciutadella inlet and adjacent platja gran inlet both 1997 events are numerically simulated and good agreement is achieved with observations in time frequency including eigenfrequencies of the affected inlets and wave heights subsequently the same model is applied to simulate the 2006 event the vigorous currents with speeds up to 400 cm s are found to occur specifically at those areas of the harbour where the most severe damage and sinking of boats had been reported maximum simulated sea level heights of 2 5 m were about one half of those reported by eyewitnesses this difference is apparently caused by quality and spatial resolution of bathymetry data however in general the model is capable of reproducing the event fairly well and can probably be used for future assessment and mitigation activities on the coasts of the balearic islands

smnd isotopic systematics of a gabbro eclogite transition abstract sm nd isotopic systems have been studied in 1 a sequence of coronitic olivine gabbros showing different degrees of transition to eclogite 2 coronitic leuco gabbro norite and 3 country rock eclogite all from the nordoyane brattvag area western norway isochrons defined by combinations of whole rock samples and relict igneous phases give ages of 1198 56 and 1289 48 ma olivine gabbro and 926 70 ma leuco gabbro norite and have been interpreted in terms of two different episodes of igneous intrusion in gabbro with advanced corona formation relict augite tends to retain its original nd isotopic composition while plagioclase may show selective disturbance related to recrystallization and partial replacement by garnet in completely eclogitized samples there is a correlation between the degree of isotopic equilibrium and microstructural equilibrium whole rock eclogites occurring within gabbro are characterized by pseudomorphs after igneous phases and preserve original igneous nd isotopic composition results for eclogite minerals suggest caledonian ages but these phases have not achieved complete isotopic equilibrium in contrast nd isotopic systems in texturally equilibrated and strongly deformed eclogite within adjacent gneisses have been disturbed on a whole rock scale minerals from an external eclogite define a sm nd isochron with an age of 400 16 ma which is interpreted to date synkinematic eclogite equilibration at high p and t conditions

odessa tsunami of 27 june 2014 observations and numerical modelling on 27 june a 1 2 m high wave struck the beaches of odessa the third largest ukrainian city and the neighbouring port town illichevsk northwestern black sea throughout the day prominent seiche oscillations were observed in several other ports of the black sea tsunamigenic synoptic conditions were found over the black sea stretching from romania in the west to the crimean peninsula in the east intense air pressure disturbances and convective thunderstorm clouds were associated with these conditions right at the time of the event a 1 5 hpa air pressure jump was recorded at odessa and a few hours earlier in romania we have utilized a barotropic ocean numerical model to test two hypotheses 1 a tsunami like wave was generated by an air pressure disturbance propagating directly over odessa experiment 1 2 a tsunami like wave was generated by an air pressure disturbance propagating offshore approximately 200 km to the south of odessa and along the shelf break experiment 2 both experiments decisively confirm the meteorological origin of the tsunami like waves on the coast of odessa and imply that intensified long ocean waves in this region were generated via the proudman resonance mechanism while propagating over the northwestern black sea shelf the odessa tsunami of 27 june 2014 was identified as a beach meteotsunami similar to events regularly observed on the beaches of florida usa but different from the harbour meteotsunamis which occurred 1 3 days earlier in ciutadella baleares spain mazara del vallo sicily italy and vela luka croatia in the mediterranean sea despite that they were associated with the same atmospheric system moving over the mediterranean black sea region on 23 27 june 2014

diffusion between olivine and spinel application to geothermometry abstract heating experiments were carried out at 1100 c and 1200 c under controlled oxygen fugacity on olivine spinel assemblages from new caledonia this mineral pair constitutes a perfect experimental material for such studies the result was a marked change in chemical composition of the minor phase olivine it becomes enriched in iron and chromium and the magnesium and nickel contents decrease careful studies of the influence of oxygen fugacity show that though it has a strong effect on the rate of re equilibration it does not affect the equilibrium composition of the phases the stability limits of the mineralogical assemblage used are also examined our results show the possibility of an important subsolidus re equilibration in natural assemblages containing olivine and spinel a new equation for the geothermometer based upon fe 2 mg 2 partitioning between olivine and spinel is proposed and some applications discussed

genetic and temporal relations between formation waters and biogenic methane upper devonian antrim shale michigan basin usa abstract controversy remains regarding how well geochemical criteria can distinguish microbial from thermogenic methane natural gas in most conventional deposits has migrated from a source rock to a reservoir rarely remaining associated with the original or cogenetic formation waters we investigated an unusual gas reservoir the late devonian antrim shale in which large volumes of variably saline water are coproduced with gas the antrim shale is organic rich of relatively low thermal maturity extensively fractured and is both source and reservoir for methane that is generated dominantly by microbial activity this hydrogeologic setting permits integration of chemical and isotopic compositions of coproduced water and gas providing a unique opportunity to characterize methane generating mechanisms the well developed fracture network provides a conduit for gas and water mass transport within the antrim shale and allows invasion of meteoric water from overlying aquifers in the glacial drift steep regional concentration gradients in chemical and isotopic data are observed for formation waters and gases dilute waters grade into dense brines 300 000 ppm over lateral distances of less than 30 km radiogenic 14c and 3h and stable isotope 18o and d analyses of shallow antrim shale formation waters and glacial drift groundwaters indicate recharge times from modern to 20 000 yr bp carbon isotope compositions of methane from antrim shale wells are typical of the established range for thermogenic or mixed gas 13c 47 to 56 however the unusually high 13c values of co2 coproduced with methane 22 and dissolved inorganic carbon dic in formation waters 28 require bacterial mediation the d values of methane and coproduced formation water provide the strongest evidence of bacterial methanogenesis methane ethane propane ratios and 13c values for ethane indicate 1 the presence of a thermogenic gas component that increases basinward and 2 progressive bacterial oxidation of ethane as the antrim shale subcrop is approached multiple episodes of pleistocene glaciation over northern michigan appear critical to the development of these gas deposits loading of thick ice sheets may have provided hydraulic head that enhanced dilation of preexisting fractures and influx of meteoric water the physical erosion cycle of repeated glacial advances and retreats exhumed the antrim shale around the northern margin of the michigan basin subjecting it to near surface physiochemical and biochemical processes the chemical and hydrologic relations demonstrated in the antrim shale reservoir suggest a dynamic connection between pleistocene glacial history of the midcontinent region and development of recoverable microbially generated natural gas reserves

thermal cracking of kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation abstract the purpose of the study is to compare artificial maturation of kerogens representative of the main types of organic matter kerogen types i ii ii s and iii in open and anhydrous closed pyrolysis systems the generated compounds are fractionated according to their thermal stability into six chemical classes c 1 c 2 c 5 c 6 c 14 c 15 saturates c 15 aromatics and nsos which include resins and asphaltenes in both systems primary cracking of kerogen can be described by two main reactions oil generation together with early gas generation followed by late gas production mass balances obtained in the two pyrolysis systems are reasonably similar although some secondary cracking of the nsos and underestimation of methane potential due to incomplete pyrolysis may occur in the open system kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies the resultant frequency factors are checked with those obtained for specific molecular tracers such as n c 12 and n c 24 alkanes generated from kerogens in open and closed systems under isothermal conditions the results show that using a unique frequency factor as determined by optimization is correct for type i ii and ii s kerogens this factor is more questionable however when the distribution of activation energies is very broad such as for type iii coals based on this study a strategy for determination of kinetic parameters on any new source rock sample is proposed

origin and accumulation of carbon dioxide in the huanghua depression bohai bay basin china the co2 content in natural gas in the huanghua depression bohai bay basin china is highly variable ranging from 0 003 to 99 6 understanding the origin and distribution of the co2 is important to assess risk prior to drilling this study uses gas geochemistry to identify the origins of co2 in the sedimentary basin and places these findings within a geologic context chemical compositions 3he 4he and 40ar 36ar were measured for 50 gas samples collected from gas and oil producing wells located in different tectonic regions in the depression from these analyses we determined that the co2 in the huanghua depression originated from three sources thermal decomposition of organic matter thermal decomposition of carbonate minerals and mantle degassing gases with low amounts 3 of co2 tend to be organogenic this organogenic co2 occurs in hydrocarbon accumulations and is characterized by values ranging from 20 to 10 and low 3he 4he r ra 1 herein r and ra represent the 3he 4he ratio of sample and air respectively carbon dioxide originating from thermal carbonate decomposition occurs as a minor component 10 in hydrocarbon gas accumulations and is characterized by a narrow range of 2 to 2 and r ra 1 huanghua depression natural gases with co2 content in excess of 15 resulted from mantle degassing and mainly occur at the intersection of faults these gases have 3he 4he ratios in excess of atmospheric value r ra 1 and ranging from 5 to 3 volatiles from mantle degassing during the postmagmatic stage are the most likely major source for co2 in these high co2 content reservoirs basement faults likely provide pathways for the upward migration of co2 rich mantle fluids consequently co2 rich gas pools are locally concentrated in the gangxi and dazhongwang fault zones within the depression

tsunamis in the black sea comparison of the historical instrumental and numerical data 1 the tsunami hazard in the black sea is discussed by comparing historical instrumental data and numerical results there are 22 tsunami events in the black sea documented since the first century and nine of them have occurred in twentieth century the numerical simulations of tsunami propagation for the 1966 and 1939 events are performed by using the framework of the shallow water theory the instrumental data from tide gauge records are used to compare and validate the simulation results and estimate the wave motion at other locations where the instrumental data are unavailable the distribution of maximum positive tsunami amplitudes along the north and south coasts are obtained for each event the arrival time tsunami amplitudes and directivity of tsunamis in the black sea are studied the probable source and target areas of tsunamis are discussed

fresh evidence relating the great adriatic surge of 21 june 1978 to mesoscale atmospheric forcing 1 on the morning of 21 june 1978 exceptional sea level oscillations with a trough to crest height of 6 m and a period of 10 20 min were observed in vela luka bay slightly less pronounced variability was observed in a wider middle and south adriatic east coastal area and with some delay along the west coast in this paper one of the original hypotheses put forward to interpret the event relating it to a mesoscale air pressure disturbance is reconsidered by using all the available data as well as state of the art meteorological and oceanographic models a fresh look at the meteorological data confirms that the atmospheric disturbance propagated at about 22 m s in a northeastward direction additionally the data suggest that it had the shape of the boxcar function characterized by an air pressure offset of 3 mbar and duration of 10 min the meteorological model employed weather research and forecasting wrf advanced research wrf proves unable to reproduce the mesoscale disturbance coinciding with the surge but it shows that the background atmospheric conditions were favorable for the development of such disturbances the oceanographic model advanced circulation model for shelves coasts and estuaries two dimensional depth integrated forced by the described air pressure disturbance successfully reproduces sea level variability in vela luka bay reaching a few meters and thus surpassing the inverted barometer response by two orders of magnitude the enhancement appears to be due to a four phase process the model also suggests that the scattering due to the variable bathymetry and the reflection from the east adriatic coast resulted in waves that returned towards the west coast and generated considerable sea level activity there

possible atmospheric origin of the 7 may 2007 western black sea shelf tsunami event 1 the paper examines the possibility that tsunami event recorded in the western black sea on 7 may 2007 was triggered by a traveling atmospheric disturbance as meteotsunamis are favored by specific synoptic conditions we inspected available ground and sounding observations european centre for medium range weather forecasts reanalysis fields and satellite based products and compared them to the documented mediterranean meteotsunamis we found an atmospheric disturbance traveling toward 30 nne with amplitude of 2 3 hpa and propagation speed of about 16 m s passing through few tens of kilometers wide pathway over the region affected by the tsunami this disturbance occurred in the lower troposphere but it was capped by instable convective cell that preserved gravity disturbance s coherence over a region at least 150 km long an ocean modeling study showed that such a disturbance is capable of generating large tsunami waves and strong currents over the shallow regions following the observations over the region where maximum sea level oscillations have been documented therefore this event has a potential to be classified as a meteotsunami the first of such kind in the black sea

genetic types of natural gas and gas source correlation in different strata of the yuanba gas field sichuan basin sw china abstract the chemical compositions and stable carbon and hydrogen isotopic compositions of natural gases in different strata of the yuanba gas field in the sichuan basin were analyzed to investigate their genetic types and source natural gases from the permian changxing and triassic feixianguan formations have dryness coefficients higher than 0 995 and contain h 2 s in most gas samples having a positive correlation between the h 2 s and co 2 contents the identification of gas origin and gas source correlation from this study indicate that natural gas in the ziliujing formation and most gas samples from the xujiahe formation are coal type gas produced from primary cracking of kerogen and they are self sourced reservoirs in relatively independent systems the natural gases in the 1st and 2nd members of the xujiahe formation were mixed with minor amounts of oil type gas from argillaceous carbonate rocks in the leikoupo formation in addition to the self accumulated oil type gas in the leikoupo formation natural gas mainly came from the overlying or lateral source rocks in the xujiahe formation the h 2 s bearing natural gases in the changxing and feixianguan formations were produced by the cracking of crude oil from source rocks in the underlying wujiaping formation with partial contributions from certain local source rocks in the permian dalong formation the h 2 s bearing natural gas has undergone the thermochemical sulfate reduction tsr which were dominated by heavy hydrocarbons the high 13 c values of co 2 in these gas reservoirs mainly result from the interaction between acidic fluids and carbonate rocks in the reservoirs

the mad sea phenomenon in the strait of sicily sea level observations at cape bon tunisia and mazara del vallo sicily show that large coherent oscillations exist across the strait of sicily with significant energy bands centered at periods of 35 3 41 6 50 6 75 8 and 134 5 min whose possible structure is confirmed by a numerical approximation to the gravitational barotropic normal modes with realistic topography it is observed that these oscillations are related to the passage of synoptic weather systems over the region an investigation on the configuration phase velocity and direction of approach of atmospheric disturbances over the region suggests that the oscillations in the strait of sicily could be forced by instabilities that develop in large scale low pressure fronts that propagate as pressure gravity waves with an approximate phase speed between 24 and 30 m s21

are meteotsunamis an underrated hazard meteotsunamis are generated by meteorological events particularly moving pressure disturbances due to squalls thunderstorms frontal passages and atmospheric gravity waves relatively small initial sea level perturbations of the order of a few centimetres can increase significantly through multi resonant phenomena to create destructive events through the superposition of different factors the global occurrence of meteotsunamis and the different resonance phenomena leading to amplification of meteotsunamis are reviewed results from idealized numerical modelling and field measurements from southwest australia are presented to highlight the relative importance of the different processes it is shown that the main influence that leads to amplification of the initial disturbance is due to wave shoaling and topographic resonance although meteotsunamis are not catastrophic to the extent of major seismically induced basin scale events the temporal and spatial occurrence of meteotsunamis are higher than those of seismic tsunamis as the atmospheric disturbances responsible for the generation of meteotsunamis are more common high energy events occur only for very specific combinations of resonant effects the rareness of such combinations is perhaps the main reason why destructive meteotsunamis are exceptional and observed only at a limited number of sites globally

tsr versus non tsr processes and their impact on gas geochemistry and carbon stable isotopes in carboniferous permian and lower triassic marine carbonate gas reservoirs in the eastern sichuan basin china abstract the palaeozoic and lowermost mesozoic marine carbonate reservoirs of the sichuan basin in china contain variably sour and very dry gas the source of the gas in the carboniferous permian and lower triassic reservoirs is not known for certain and it has proved difficult to discriminate and differentiate the effects of thermal cracking and tsr related processes for these gases sixty three gas samples were collected and analysed for their composition and carbon stable isotope values the gases are all typically very dry alkane gases being 97 5 methane with low 2 s and co 2 carboniferous gas is negligibly sour while the lower triassic gas tends to be most sour the elevated h 2 s up to 62 is due to thermochemical sulphate reduction with the most sour triassic and permian reservoirs being deeper than 4800 m the non tsr affected carboniferous gas is a secondary gas that was derived from the cracking of sapropelic kerogen derived oil and primary gas and is highly mature carboniferous and non sour triassic and permian gas has unusual carbon isotopes with methane and propane being isotopically heavier than ethane a reversal of typical low to moderate maturity patterns the gas in the non sour triassic and permian reservoirs has the same geochemical and isotopic characteristics and therefore the same source as the carboniferous gas tsr in the deepest triassic reservoirs altered the gas composition reaching 100 dryness in the deepest most sour reservoirs showing that ethane and propane react faster than methane during tsr ethane evolves to heavier carbon isotope values than methane during tsr leading to removal of the reversed alkane gas isotope trend found in the carboniferous and non sour triassic and permian reservoirs however methane was directly involved in tsr as shown by the progressive increase in its carbon isotope ratio as gas souring proceeded co 2 increased in concentration as gas souring proceeded but typical co 2 carbon isotope ratios in sour gases remained about 4 v pdb showing that it was not solely derived from the oxidation of alkanes instead co 2 may partly result from reaction of sour gas with carbonate reservoir minerals such as fe rich dolomite or calcite resulting in pyrite growth as well as co 2 generation

unravelling abiogenic and biogenic sources of methane in the earth s deep subsurface at four underground sites in precambrian shield rocks in canada and south africa hydrocarbon and hydrogen gases exsolving from saline fracture waters are analyzed for compositional and isotopic signatures dominated by reduced gases such as ch4 h 2 and higher hydrocarbons ethane propane butane the most 13 c enriched methane end members at all four sites show a pattern of carbon and hydrogen isotopic values similar to abiogenic gases produced by water rock interaction that have been identified previously at one site on the precambrian shield in canada the abiogenic nature of these gases was not previously recognized due to mixing with a second methane component produced by microbial processes the microbial methane end member is identified based on carbon and hydrogen isotopic signatures and dna gene amplification pcr data that indicate the presence of methanogens a framework is presented to estimate the relative contribution of abiogenic versus microbial hydrocarbon gases at these sites this approach has important implications for evaluation of potential abiogenic hydrocarbon reservoirs in a wide range of geologic settings including the longstanding controversy concerning the possible contribution of abiogenic gases to economic petroleum hydrocarbon reservoirs the association of high concentrations of h2 with 13 c enriched ch4 end members and h2 depletion in the 13 c depleted methanogenic end members further suggests the possibility that abiogenic gases may support h2 autotrophy linked to methanogenesis in the deep subsurface d 2005 elsevier b v all rights reserved

introduction to global tsunami science past and future volume ii twenty two papers on the study of tsunamis are included in volume ii of the pageoph topical issue global tsunami science past and future volume i of this topical issue was published as pageoph vol 173 no 12 2016 eds e l geist h m fritz a b rabinovich and y tanioka three papers in volume ii focus on details of the 2011 and 2016 tsunami generating earthquakes offshore of tohoku japan the next six papers describe important case studies and observations of recent and historical events four papers related to tsunami hazard assessment are followed by three papers on tsunami hydrodynamics and numerical modelling three papers discuss problems of tsunami warning and real time forecasting the final set of three papers importantly investigates tsunamis generated by non seismic sources volcanic explosions landslides and meteorological disturbances collectively this volume highlights contemporary trends in global tsunami research both fundamental and applied toward hazard assessment and mitigation

meteorological tsunami of 19 march 2017 in the persian gulf observations and analyses on 19 march 2017 destructive tsunami like waves impacted the northeast shore of the persian gulf pg the maximum surveyed runup of about 3 m was observed at dayyer in southern iran where damaging waves inundated the land for a distance of 1 km and resulted in the deaths of five people because the pg has always been considered safe from extreme oceanic waves the event was totally unexpected in this study we examined sea level data from 12 stations across the pg and a variety of meteorological information including satellite imagery high altitude isohypse maps and high resolution air pressure records from 47 instruments along the pg our results show that the event was very local with recorded maximum trough to crest wave heights of 197 cm at dayyer and 234 cm at asaluyeh near field cities in iran located 80 km apart the dominant wave periods were in the range of 15 20 min at all distant tide gauges the observed wave heights were 35 cm no earthquakes or landslides were evident at the time of the event on the other hand atmospheric processes during 18 22 march were very active and 10 distinctive tsunamigenic air pressure disturbances were observed propagating over the pg suggesting that the event of 19 march 2017 was a meteorological tsunami atmospheric conditions over the pg were highly favourable for the generation of meteotsunamis and very similar to those that caused a chain of strong meteotsunamis in the mediterranean and black sea regions during 23 27 june 2014 based on the 500 hpa wind we evaluated that the disturbances had propagation speeds of 21 38 m s with the disturbance at dayyer having a speed of 26 m s toward 77 true the froude number fr estimated as the ratio of the air disturbance speed to the long wave speed on 19 march 2017 in the dayyer asaluyeh region was close to resonance fr 0 9 to 1 1 which is highly favourable for meteotsunami generation our findings indicate that the dayyer asaluyeh area is a hot spot that is highly vulnerable to extreme weather induced tsunami like waves

microdiamond in high grade metamorphic rocks of the western gneiss region norway three grains of microdiamond were recovered from high grade gneiss exposed in the western gneiss region norway identification and characterization of the diamond grains by raman and infrared spectroscopy indicate the presence of substitutional impurities of h and n primary fluid inclusions in garnet and quartz in the diamond bearing rock demonstrate the evolution of metamorphic volatile fluids from reduced n 2 co 2 compositions during the peak phase of metamorphism to n 2 ch 4 h 2 o bearing compositions during retrograde metamorphism compatible geologic petrologic and fluid composition data imply a metamorphic origin for the microdiamonds if so the metamorphic and fluid conditions recorded by the microdiamonds and gneissic host may be applicable to microdiamond investigations in other high pressure regionally metamorphosed orogens

tectonics of the scandian orogeny and the western gneiss region in southern norway two crust forming events dominate the precambrian history of the western gneiss region wgr at about 1800 1600 ma and 1550 1400 ma the influence of the sveconorwegian orogeny 1200 900 ma is restricted to the region south of moldefjord romsdalen a series of anorthosites and related intrusives are present possibly derived from the now lost western margin of the baltic craton that may have been emplaced in the wgr as an allochthonous unit before the ordovician

isotope reversals and universal stages and trends of gas maturation in sealed self contained petroleum systems abstract isotope geochemistry is now a tool for shale gas exploration largely due to the association of isotope reversals with mature highly productive shale gas its utility however depends on an understanding of the isotope systematics for the particular region of interest as well as for shale gas maturation in general this paper reviews and re examines isotope data from four published papers that include shale gas from the barnett and fayetteville shales rodrigez and philp 2010 zumberge et al 2012 and gas from fractured reservoirs in the appalachians burruss and laughrey 2010 and the foothills of the western canada sedimentary basin wcsb tilley et al 2011 new shale and tight sandstone gas data are also presented for the wcsb comparisons of these data show that the progression through three stages of gas maturation pre rollover zone rollover zone and post rollover zone is universal in sealed self contained petroleum systems and that each zone has characteristic isotopic relationships and trends that are seen in all areas examined gases in the pre rollover zone are isotopically normal 13 c methane 13 c ethane 13 c propane unless mixing of gases from different sources has occurred in the rollover zone 13 c ethane and 13 c propane become progressively more negative as 13 c methane becomes less negative and ethane and methane are reversed 13 c ethane 13 c methane only towards the most mature portion of the rollover zone at the beginning of the post rollover zone 13 c ethane 13 c methane but as 13 c ethane and 13 c propane become increasingly less negative at varying rates ethane and propane may or may not be reversed with respect to each other at the highest maturities 2 h methane in gases of the post rollover zone approaches isotopic equilibrium with local formation water generally becoming more negative with increasing maturity correct assignment of maturity stage could be of importance because the rollover zone may represent the peak of high productivity shale gas whereas the post rollover zone may represent a decline in productivity burruss and laughrey 2010

source of the 2007 ist meteotsunami adriatic sea 1 siroka bay on the island of ist in the northern adriatic was struck by a severe inundation around 1530 utc on 22 august 2007 the maximum wave height reached 4 m and substantial material damage was induced this paper investigates the generating force of the inundation data analysis indicates that the inundation was provoked through a double resonance mechanism with initiation by a pronounced atmospheric disturbance that generated open ocean waves through the proudman resonance the waves were then further amplified inside the affected bay the air pressure disturbance which propagated at a speed of about 21 24 m s 1 over the northern adriatic shelf was investigated through both data analysis and atmospheric numerical modeling apparently the air pressure disturbance was a surface manifestation of a ducted gravity wave which propagated through the atmosphere from the apennines to the eastern adriatic coast over the northern adriatic according to the model simulation the wave was trapped in a stable layer adjacent to the ground which was capped by a dynamically unstable layer with wind speeds of about 22 m s 1 this made the unstable layer also a critical layer for gravity waves propagating with the same speed and allowed for their ducting in the layer below

gas isotope reversals in fractured gas reservoirs of the western canadian foothills mature shale gases in disguise isotopically reversed gases 13c methane 13c ethane 13c propane occur in fractured mixed clastic carbonate reservoirs of the permian and the triassic in the foothills at the western edge of the western canada sedimentary basin wcsb the 13c methane values 42 to 24 gas dryness and organic maturity ro 2 2 are indicative of mature gases and gas maturity generally increases with reservoir age and from the southeast to the northwest the 13c ethane values range from 44 to 25 with the less negative values in isotopically normal gases to the northeast of the gas fields we studied to explain the gas isotope reversals observed in the wcsb foothills we adopt the concept of a closed system shale in which simultaneous cooking of kerogen oil and gas yields gas with light 13c ethane and heavy 13c methane this gas was released from shales and trapped in fractured folds of brittle clastic carbonate rocks during deformation and thrust faulting of the laramide orogeny creating some of the most prolific gas pools these gases are actually mature shale gases local high abundances of h2s and co2 are most likely the products of thermochemical sulfate reduction tsr reactions in anhydrite rich interbeds and underbeds that admixed to the released shale gas during the tectonic event no evidence exists that tsr is responsible for the isotope reversals variations in 13c ethane are likely caused by local differences in thermal history the timing of gas release from shale and the timing of the fault and fold development less negative 13c ethane values resulting in isotopically normal gases to the northeast of the fields and in the underlying devonian carbonates likely reflect a more open shale system where the earliest generated gas was lost we suggest that isotopic reversals are restricted to closed system maturation and that their magnitude may be related to the relative volume of gas retained in shales

origin and carbon isotope fractionation of co2 in marine sour gas reservoirs in the eastern sichuan basin abstract according to gas chemical and carbon isotopic compositions for 75 gas samples from the eastern sichuan basin c 1 c 3 gaseous hydrocarbons are dominant with high dryness coefficient c 1 c 1 3 0 99 1 0 despite the presence of various contents of h 2 s and co 2 a reasonably good positive correlation is exhibited when both contents are 5 the carbon dioxide in the natural gas in the eastern sichuan basin mainly originated from carbonate dissolution by acid gases and thermochemical sulfate reduction tsr the content of co 2 produced at the early stage of acid gas dissolution is commonly 13 c co2 value 2 content exceeds 5 the 13 c co2 values range from 8 to 2 and the co 2 and h 2 s contents demonstrated a positive correlation the majority of co 2 is generated via tsr as well as acid gas dissolution during the late uplift of the basin particularly the co 2 with 13 c co2 value 2 generated via the tsr after it was partially precipitated to form calcite while the co 2 with 13 c co2 value 3 is a mixture of the co 2 produced early via tsr and the co 2 produced by the subsequent carbonate rock dissolution by acid gases

genetic origins of marine gases in the tazhong area of the tarim basin nw china implications from the pyrolysis of marine kerogens and crude oil abstract although abundant natural gases have been discovered in carboniferous and ordovician reservoirs in the tazhong area central tarim basin their genetic origins is still an open question because of significant variations in chemical and carbon isotopic compositions in the present study three samples representing the possible gas sources were pyrolyzed using sealed gold tubes to investigate their gas potentials and chemical and carbon isotopic signatures the samples were a crude oil a low maturity kerogen and a high maturity kerogen the results show that the chemical and isotopic compositions of gaseous pyrolysates from the three samples are quite different generally the gases from oil cracking are compositionally wetter and isotopically lighter than those from kerogen cracking at similar thermal levels the large quantities of methane experimentally observed in oil cracking gases are mainly associated with the re cracking of wet gases at very high maturity levels methane in gases derived from kerogen especially high maturity kerogen in contrary is mainly generated by the demethylation reaction the diagrams of 13c1 vs 13c2 13c3 and c2 c3 vs 13c2 13c3 along with natural gas plots have proven to be a very effective tool in the genetic interpretation of natural gases from kerogen and oil cracking in the tarim basin their combined application shows that two types of gas source can be identified in the tazhong area the first type is oil cracking gas mainly discovered in carboniferous reservoirs of the central fault horst area but also partly in ordovician reservoirs such as in the wells tz45 tz44b and tz 16 the other is kerogen cracking gas occurring largely in ordovician reservoirs especially in the north slope area the two types of gases however are mixed in many reservoirs as their generation is overlapped in time and or space this mixing process is especially obvious for methane

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

evidence for multiple stages of oil cracking and thermochemical sulfate reduction in the puguang gas field sichuan basin china the puguang gas field is the largest gas field found in marine carbonates in china marine carbonate reservoirs in this field were buried to a depth of about 7000 m 22 966 ft and experienced maximum temperature up to 220c before uplift to the present day depth of 5000 5500 m 16 404 18 045 ft with present day thermal maturity between 2 0 and 3 0 equivalent vitrinite reflectance ro sulfur rich pyrobitumens with reflectance up to 3 5 are widespread in the reservoirs and resulted from thermal cracking of crude oils most likely generated from upper permian source rocks and thermochemical sulfate reduction tsr natural gases in the puguang gas field have wide variations in nonhydrocarbon gas contents with h2s contents between 5 1 and 58 3 and co2 contents between 7 9 and 18 0 the hydrocarbon gases originated mainly from thermal cracking of accumulated oil but were altered by tsr thermochemical sulfate reduction in the study area exerted different effects on the isotope compositions of different hydrocarbon gas components at different tsr stages the differential increase of 13c values for different gas components reflects transformation from a heavy hydrocarbon gas dominated tsr stage to a methane dominated tsr stage this caused a decrease of 13cmethane13cethane values and a corresponding conversion from reversed to normal isotope distributions thermochemical sulfate reduction in the study area appears to have been limited by sulfate concentrations in the reservoirs a successive three stage tsr series namely liquid hydrocarbon involved tsr heavy hydrocarbon gas dominated tsr and methane dominated tsr occurred in reservoirs with sufficient sulfate concentration methane can be the dominant organic reactant for tsr but only at elevated temperature and after most c2 hydrocarbons are exhausted

cause of shale gas geochemical anomalies and mechanisms for gas enrichment and depletion in high maturity shales abstract this article reviews the abnormal characteristics of shale gases natural gases produced from organic rich shales and discusses the cause of the anomalies and mechanisms for gas enrichment and depletion in high maturity organic rich shales the reported shale gas geochemical anomalies include rollover of iso alkane normal alkane ratios rollover of ethane and propane isotopic compositions abnormally light ethane and propane 13 c values as well as isotope reversals among methane ethane and propane these anomalies reflect the complex histories of gas generation and associated isotopic fractionation as well as in situ mixing and accumulation of gases generated from different precursors at different thermal maturities a model was proposed to explain the observed geochemical anomalies gas generation from kerogen cracking at relatively low thermal maturity accounted for the increase of iso alkane normal alkane ratios and ethane and propane 13 c values normal trend simultaneous cracking of kerogen retained oil and wet gas and associated isotopic fractionation at higher maturity caused decreasing iso alkane normal alkane ratios lighter ethane and propane 13 c and corresponding conversion of carbon isotopic distribution patterns from normal through partial reversal to complete reversal relatively low oil expulsion efficiency at peak oil generation low expulsion efficiency at peak gas generation and little gas loss during post generation evolution are necessary for organic rich shales to display the observed geochemical anomalies high organic matter richness high thermal maturity high degrees of kerogen gas and oil gas conversions and late stage the stage of peak gas generation and post generation evolution closed system accounted for gas enrichment in shales loss of free gases during post generation evolution may result in gas depletion or even undersaturation total gas content lower than the gas sorption capacity in high maturity organic rich shales

geochemical characterization of gases from the mississippian barnett shale fort worth basin texas molecular and isotopic compositions of 51 gas and 7 condensate samples produced from the barnett shale were determined by gas chromatography isotope ratio mass spectrometry to investigate their origin and maturity at the time of generation additionally two hydrous pyrolysis experiments were performed to calibrate maturity values predicted for gas generation molecular and carbon and hydrogen isotopic compositions of the gases indicate that gas produced from the barnett is thermogenic to estimate generation maturity additional analyses were performed on the condensates and available core samples diamondoid indices combined with vitrinite reflectance ro measurements isotopic and molecular composition and hydrous pyrolysis experiments suggest that gas produced from the barnett shale was generated within the condensate wet gas window 1 3 2 0 ro at a later stage than hydrocarbons accumulated in shallower reservoirs the origin of the gas is thermogenic probably derived from both kerogen cracking and secondary cracking of previously generated nonmigrated hydrocarbons additionally the occurrence of a methane isotope reversal in group 1 gases corroborates that in situ oil or gas cracking is occurring in the easternmost part of the study area

incomplete high p t metamorphic transitions within the kvamsoy pyroxenite complex west norway a case study of disequilibrium the kvamsoy pyroxenite complex consists of olivine websterite olivine gabbro and leucogabbro norite which have been subjected to regional high p t hpt metamorphism the metamorphism has resulted in a range of disequilibrium textures with the development of coronas and pseudomorphism of the igneous phases reactions between felsic and mafic mineral domains have been controlled by variable and selective diffusion of elements resulting in a variety of local plagioclase breakdown reactions and in significant compositional variations for the product garnet restricted diffusion favours transient reaction stages with garnet spinel corundum zoisite after calcic plagioclase in olivine gabbro and olivine websterite and garnet spinel kyanite quartz sodic plagioclase in leucogabbro norite complete hpt reaction has produced garnet pyroxenite which consists of garnet diopside hornblende zoisite in gabbroic rocks while amphibolitization continued during the cooling and uplift history grt ky pl qtz geobarometry suggests pressures in the range 13 16 kbar for t 750 c comparable with the regional eclogite forming metamorphism

reduction of co2 during serpentinization of olivine at 300 c and 500 bar co 2 reduction processes occurring during experimental serpentinization of olivine at 300 c and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas data reveal that conversion of fe ii in olivine to fe iii in magnetite during serpentinization leads to production of h 2 and conversion of dissolved co 2 to reduced c species including methane ethane propane and an amorphous carbonaceous phase hydrocarbon gases generated in the process fit a schulz flory distribution consistent with catalysis by mineral reactants or products magnetite is inferred to be the catalyst for methanization during serpentinization because it has been previously shown to accelerate fischer tropsch synthesis of methane in industrial applications involving mixtures of h 2 and co 2 the carbonaceous phase was predominantly aliphatic but had a significant aromatic component although this phase should ultimately be converted to hydrocarbon gases and graphite if full thermodynamic equilibrium were established its formation in these experiments indicates that the pathway for reduction of co 2 during serpentinization processes is complex and involves a series of metastable intermediates

origin of methane in serpentinite hosted hydrothermal systems the ch4 h2 h2o hydrogen isotope systematics of the hakuba happo hot spring abstract serpentinite hosted hydrothermal systems have attracted considerable attention as sites of abiotic organic synthesis and as habitats for the earliest microbial communities here we report a systematic isotopic study of a new serpentinite hosted system the hakuba happo hot spring in the shiroumadake area japan 36 42 n 137 48 e we collected water directly from the hot spring from two drilling wells more than 500 m deep all water samples were strongly alkaline ph 10 and rich in h2 201 664 mol l and ch4 124 201 mol l despite the relatively low temperatures 50 60 c thermodynamic calculations suggest that the h2 was likely derived from serpentinization reactions hydrogen isotope compositions for happo 1 happo 3 were found to be as follows d h 2 700 710 d ch 4 210 300 and d h 2 o 85 84 the carbon isotope compositions of methane from happo 1 and 3 were found to be c 13 34 5 and 33 9 respectively the ch4 h2 h2o hydrogen isotope systematics indicate that at least two different mechanisms were responsible for methane formation happo 1 has a similar hydrogen isotope compositions to other serpentinite hosted systems reported previously the elevated d ch 4 with respect to the equilibrium relationship suggests that the hydrogen of the happo 1 methane was not sourced from molecular hydrogen but was derived directly from water this implies that the methane may not have been produced via the fischer tropsch type ftt synthesis but possibly by the hydration of olivine conversely the depleted d ch 4 with respect to the equilibrium relationship in happo 3 suggests the incorporation of biological methane based on a comparison of the hydrogen isotope systematics of our results with those of other serpentinite hosted hydrothermal systems we suggest that abiotic ch4 production directly from h2o without mediation by h2 may be more common in serpentinite hosted systems hydration of olivine may play a more significant role in abiotic methane production than previously thought

atmospheric origin of the devastating coupled air sea event in the east adriatic enhanced sea level oscillations with devastating effects occurred on 26 27 june 2003 in the east adriatic the phenomenon was recognized as a resonantly coupled air sea interaction where the sea wave is forced by the propagating atmospheric pressure disturbance this study examines the dynamics and predictability of the atmospheric component of the coupled system first the initiation amplification and maintenance of the system are examined the source of the perturbation is traced back to the alpine region where the potentially unstable air in the westerly current lifts over the alps resulting in convection and wave development the wave and convective activity apparently couple in a wave cisk manner and propagate southeastward down the eastern adriatic coast due to the potentially unstable air above the adriatic the system additionally amplifies along its track the dissipation of the system occurs after the landfall second the performance of the numerical model at the resolution that is similar to operational nwp model resolution is examined this severe event is highly susceptible to the details of the model configuration presumably due to the sensitivity in coupling of the wave and mcs thus although the model is able to reproduce and forecast this kind of event at a fairly coarse resolution the details of the spatial structure as well as the time of onset are questionable in this case the greatest sensitivity is primarily in the treatment of moist and convective processes

metamorphic evolution of the eiksunddal eclogite complex western norway and some tectonic implications the metamorphic evolution of the western gneiss region of norway wgr can be evaluated from examination of eclogites formed as an integral part of the gneiss terrain ie in situ petrologic data from one of the larger country rock eclogites within the northwestern part of wgr have been used to construct a p t t path for this crustal volume textural relations as well as mineral composition and zonation suggest an early period of amphibolite facies conditions followed by movement along a very steep positive p t gradient towards very high pressure p 25 kb and moderate temperature t 600 c orthopyroxene coexisting with garnet at such conditions was poor in al 0 5 wt al2o3 and is preserved in the cores of orthopyroxene grains in garnet websterites the increasing al content of orthopyroxene towards garnet and increasing edenite substitution rimwards in zoned amphiboles suggest a period of decompression accompanied by heating towards the metamorphic maximum at t 750 c p 20kb garnet zoning reflects a general prograde history but the reactions that control the zoning are insensitive to pressure changes jadeitic pyroxenes may have formed in the gneisses at p max but would revert to plagioclase subsequent to the metamorphic maximum giving rise to the observed mineralogy further decompression and cooling continued towards high rank amphibolite facies conditions this p t t path reflects crustal thickening to 80 90 km during caledonian time the uplift path is qualitatively similar to theoretically derived paths in which uplift is assumed to be controlled by erosion however uplift following the metamorphic maximum may have been accelerated by a period of suture progradation

resonant coupling of a traveling air pressure disturbance with the east adriatic coastal waters 1 exceptional sea level oscillations and strong current reversals observed in the east adriatic on 27 june 2003 are analyzed using available meteorological and tide gauge measurements and numerical model results it is shown that the variability in the atmosphere sea system was characterized by high frequencies 0 01 0 1 min 1 and sea level and current amplitudes surpassing 1 m and 1 m s 1 respectively the event was related to the occurrence of a gravity disturbance in the atmosphere above the adriatic the disturbance traveled toward the east southeast at a speed of 22 m s 1 and was resonantly coupled with a wave in the sea 50 m deep the resulting forced wave was further amplified when entering funnel shaped bays opened to it there are indications that the forcing disturbance and its counterpart in the sea excited normal modes of the bays and harbors in the area moreover nonlinear steepening of the forced wave seemingly occurred resulting in the formation of high frequency wave trains this process along with the generation of coastal seiches could explain the observed and modeled differences between the spectra of coastal variability and the spectrum of forcing wave

kyanite eclogite to amphibolite fades evolution of hydrous mafic and pelitic rocks adula nappe central alps in the southern adula nappe central alps two stages of regional metamorphism have affected mafic and pelitic rocks earlier eclogite facies with a regional zonation from glaucophane eclogites to kyanite hornblende eclogites was followed by a tertiary overprint which varied from greenschist to high grade amphibolite facies despite a common metamorphic history contrasting equilibration conditions are often recorded by high pressure mafic eclogite and adjacent predominantly lower pressure pelite assemblages this pressure contrast may be explained by different overprinting rates of the two bulk compositions during unloading the rates are controlled by a mechanism in which dehydrating metapelites provide the h2o required for simultaneous overprinting of enclosed mafic eclogites by hydration

multi meteotsunami event in the adriatic sea generated by atmospheric disturbances of 25 26 june 2014 a series of meteotsunamis hit a few locations in the mediterranean and black seas during 22 27 june 2014 meteotsunamis were particularly numerous on 25 and 26 june in the adriatic sea where at least six harbours and bays were stricken by powerful waves strongest events occurred in vela luka korcula island a known meteotsunami hot spot where waves reached height of 3 m and in rijeka dubrovacka bay where strong 5 m s currents accompanied 2 5 m high waves intensification of high frequency sea level activity was observed at both the eastern and western adriatic tide gauge stations with maximum recorded wave heights reaching 68 cm ortona italy a series of individual air pressure disturbances characterized by pronounced rates of air pressure change up to 2 4 hpa 5 min limited spatial extent 50 km and high temporal variability propagated over the adriatic on 2 days in question numerical hydrodynamic model schism forced by measured and idealised air pressure disturbances was utilised to reproduce the observed adriatic sea level response several important conclusions were reached 1 meteotsunamis occurring at various parts of the coast were generated by different atmospheric air pressure disturbances 2 topographic influence can be removed from sea level spectra by computing spectral signal to background ratios the result being related to the external forcing resembles atmospheric pressure spectra 3 sea response is strongly dependant on details of atmospheric forcing and 4 over complex bathymetries like the middle and south adriatic ones numerous effects including proudman resonance edge waves strong topographical enhancement and refractions on the islands placed on the pathway of atmospheric disturbances should be taken into account to fully understand meteotsunami generation and dynamics an in depth numerical study is planned to supplement the latter conclusion and to quantify contribution of each process

meteotsunami marrobbio of 25 26 june 2014 on the southwestern coast of sicily italy a major tsunami like event locally known as marrobbio impacted the southwestern coast of sicily on 25 26 june 2014 the event was part of a chain of hazardous episodes in the mediterranean and black seas during the last week of june 2014 resulting from an anomalous atmospheric system tumultuous atmosphere propagating eastward over the region the synoptic patterns and vertical structure of the atmosphere over sicily at the time of the event indicate that atmospheric wave ducting was responsible for the generation of tsunamigenic air pressure disturbances that produced especially high sea level responses meteotsunamis at certain sites along the sicilian coast the strongest sea level oscillations were observed at mazara del vallo where a 1 m meteotsunami bore propagating upstream in the mazaro river was generated the combined effects of external resonance proudman resonance on the western sicilian shelf and internal resonant conditions bathymetric and topographic characteristics of specific sites were found to be the key factors that caused the meteotsunami marrobbio phenomenon on the coast of sicily and the meteobore at mazara del vallo

methane dominated thermochemical sulphate reduction in the triassic feixianguan formation east sichuan basin china towards prediction of fatal h2s concentrations abstract new sour pools have recently found in the lower triassic feixianguan fm carbonate reservoirs in the east sichuan basin in china with h 2 s up to 17 4 by volume a recent blowout from a well drilled into this formation killed hundreds of people as a result of the percentage concentrations of h 2 s in order to assess the origin of fatal h 2 s as well as the cause of petroleum alteration h 2 s concentrations and the isotopes 34 s and 13 c have been collected and measured in gas samples from reservoirs anhydrite pyrite and elemental sulphur 34 s values have been measured for comparison the high concentrations of h 2 s gas are found to occur at depths 3000 m temperature now at 100 c in evaporated platform facies oolitic dolomite or limestone that contains anhydrite nodule occurrence within the reservoirs where h 2 s concentrations are greater than 10 its 34 s values lie between 12 0 and 13 2 cdt this is within the range of anhydrite 34 s values found within the feixianguan fm 11 0 to 21 7 average 15 5 3 5 cdt thus h 2 s must have been generated by thermochemical sulphate reduction tsr locally within the reservoirs burial history analysis and fluid inclusion data reveal that the temperature at which tsr occurred was greater than about 130 140 c suggesting that the present depth temperature minimum is an artifact of post tsr uplift both methane and ethane were actively involved in tsr since the petroleum became almost totally dry no alkanes except methane and methane 13 c values become significantly heavier as tsr proceeded methane 13 c difference thus reflects the extent of tsr while it is tempting to use a present day depth control 3000 m to predict the distribution of h 2 s in the feixianguan fm this is an invalid approach since tsr occurred when the formation was buried some 1000 2000 m deeper than it is at present the likelihood of differential uplift across the basin means that it is important to develop a basinal understanding of the thermal history of the feixianguan fm so that it is possible to determine which parts of the basin have been hotter than 130 140 c

metamorphic evolution of norwegian country rock eclogites as deduced from mineral inclusions and compositional zoning in garnets abstract detailed studies of pre early syn and post eclogite mineral associations in some west norwegian country rock eclogites have made it possible to reconstruct their metamorphic evolution pre eclogite stages are represented by various amphibolite facies associations found in the central parts of prograde zoned garnets early and syn eclogite stages are represented by various eclogitic assemblages containing low and high jd omphacites respectively the former located in the intermediate zones and the latter in the outermost rims of prograde zoned garnets and in the matrix post eclogite stages include granulite amphibolite and greenschist facies associations representing replacement phases after higher grade assemblages p t estimates indicate a prograde evolution along an extremely steep p t gradient 7 9 kbar over 100 200 c while the initial post eclogite evolution involved a nearly adiabatic decompression on the order of 10 kbar

geochemistry and occurrence of inorganic gas accumulations in chinese sedimentary basins abstract inorganic gases are commonly seen in eastern china and occasionally in southern china from the shallow water columns above hot and cold springs the gases contain 68 to nearly 100 co2 with 13 c co 2 and 13c1 values in the range of 1 18 to 6 00 and 19 48 to 24 94 respectively all of the 34 large inorganic co2 and one inorganic methane accumulations discovered in china are distributed in eastern parts of the country from both onshore and continental shelf basins no commercial inorganic gas accumulation has been found in central and western china this is a review of the occurrence and geochemical characteristics of inorganic gas accumulations in chinese sedimentary basins a detailed study of gas samples collected from four representative inorganic co2 pools and one possible inorganic methane pool indicates that inorganic alkane gases typically show 13c1 values greater than 10 versus pdb mostly 30 with a positive stable carbon isotope sequence of 13c1 13c2 13c3 13c4 inorganic gases also tend to show less negative 13 c co 2 values 10 than biogenic gases

distinguishing kerogen and oil cracked shale gas using h c isotopic fractionation of alkane gases abstract the formation mechanism of 23 shale gas samples from the fuling shale gas field in the upper ordovician wufeng o3w formation lower silurian longmaxi s1l formation marine shales was investigated based on the carbon and hydrogen isotopes of methane ethane and propane fuling shale gas is mainly composed of alkane gases and has a dryness coefficient c1 c1 3 of 0 992 0 993 the reversed carbon isotopic trend where 13c1 13c2 is a typical characteristic indicating mixing of kerogen cracked gas and crude oil cracked gas the empirical correlations between ln c1 c2 vs ln c2 c3 and ln c1 c2 vs 13c of alkane gases at different thermal maturity levels were used to distinguish kerogen cracked gas from crude oil cracked gas five stages of kerogen cracking and crude oil cracking were identified with a wide range of thermal maturities vitrinite reflectance ro 1 ro 13c2 4 ro of 1 8 2 5 residual kerogen cracking proceeded to generate ch4 and light oil cracking generated heavier gaseous hydrocarbons with a completely reversed carbon isotopic trend of alkane gases 13c1 13c2 13c3 5 ro 2 5 further cracking of heavier gaseous hydrocarbons generated ch4

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

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

isotopic reversals with respect to maturity trends due to mixing of primary and secondary products in source rocks abstract carbon isotopic composition 13 c reversals with respect to maturity trends have been reported for ethane and propane in barnett shale gas in the fort worth basin u s a this trend also exists in some conventional gas reservoirs such as in the ordos basin china and appalachian basin u s a fractionation during mass transport is unlikely to be a significant mechanism because its effect is minor under geological conditions it would have caused more obvious reversal for methane than for ethane and propane and mass transport can not account for the occurrence of the trend both inside and outside source rocks this paper demonstrates that the reversal may result from mixing of indigenous primary gas generated directly from kerogen and secondary gas generated from oil and condensate within source rocks and presents deconvolution results using end members derived from a kinetic isotope fractionation model the results including the wetness and mixing ratio of primary and secondary gases are consistent with geological conditions condensates may be the major precursor of the secondary gas in shale when the reversal occurs a complete trend of 13 c variations in methane and ethane with maturity is proposed that is based on the indigenous mixing mechanism

unique chemical and isotopic characteristics and origins of natural gases in the paleozoic marine formations in the sichuan basin sw china isotope fractionation of deep and high mature carbonate reservoir gases abstract large quantities of natural gases have recently been discovered in the marine carbonate formations in the sichuan basin southern china the origins and isotopic compositions of the gases are poorly understood and highly controversial we examined the chemical and isotopic compositions of the carbonate reservoir gases in marine formations from the sinian to lower triassic as well as shale gas from the silurian and cambrian formation in the sichuan basin it is found that the carbon isotopes of the carbonate reservoir gases had been evolved through three stages corresponding to pre rollover rollover and post rollover in the plot of 13c2 versus wetness which is consistent with that found in shale gas by tilley and muehlenbachs 2013 the unique carbon isotopic compositions indicate that both kerogen and oil cracking gas have contributed to the accumulation of the carbonate reservoir gases in the sichuan basin a mixing of two thermogenic gases with different maturities can cause the 13c reversal between methane and ethane which is commonly observed in the carbonate reservoir gases in the carboniferous permian and triassic formations and the shale gas in the silurian and cambrian formations in the sichuan basin we established two mixing models for quantitatively determining the contribution of each type gas for the natural gases in different formations kinetic extrapolation based on thermal history of the anyue gas field demonstrates that ethane cracking indeed occurred in the deep reservoir formations which may explain the disappearance of the 13c reversal for methane and ethane in the carbonate reservoir gases in the post rollover zone it is proposed that organic inorganic interactions may be responsible for the presence of d isotope rollover for methane in carbonate reservoir gases with ultra high maturity the organic inorganic interactions include thermal reactions between water and residual organic matters or carbons and hydrogen isotope exchange between water and methane and their mechanism needs further investigations in future

empirical relationship between gas composition and thermal maturity in eagle ford shale south texas organic rich and carbonate rich eagle ford shale is a self sourced oil and gas reservoir with little alteration of gas chemistry as might be affected by petroleum expulsion and migration as such it provides an ideal natural laboratory to quantify the compositional variation of gases generated from oil prone type ii kerogen during thermal maturation the chemical composition of the gas released from rock crushing was conducted and integrated with rock eval pyrolysis to define the empirical relationship between gas compositional parameters and thermal maturity in this study from 10 wells in the eagle ford shale in south texas we collected 74 core samples having a range of thermal maturity the measured maximum temperature tmax values of hydrocarbons generated in rock eval pyrolysis range from 427 c to 494 c 800 f to 921 f and the calculated equivalent vitrinite reflectance roe values range from 0 51 to 1 73 based on tmax values total organic carbon content ranges from 0 3 to 8 53 with an average of 3 12 standard deviation of 1 77 burial depth is from 2989 6 to 13 827 3 ft 911 2 to 4214 6 m our results showed that gas composition in the eagle ford shale is mainly controlled by thermal maturity and three stages of gas generation are identified based on the c1 and c2 concentrations of the gases released by rock crushing from eagle ford shale core samples the three stages of gas generation correspond to the following processes of organic matter conversion 1 kerogen and bitumen thermal cracking to crude oil 2 bitumen and heavy crude oil thermal cracking to light oil and 3 light oil cracking to gas methane rich gas and an abundance of branched butane and pentane are generated in light oil cracking to gas resulting in high c1 c2 c1 c2 c3 i c4 n c4 and i c5 n c5 ratios increased cracking of normal alkanes such as n butane and n pentane occurs in the light oil cracking to gas empirical equations between gas compositional parameters and thermal maturity tmax or roe are obtained for oil prone type ii the c1 c2 c1 c2 c1 c2 c3 and i c4 n c4 ratios are the five best parameters for determining thermal maturity with an exponentially derived r2 value of 0 74 the composition of gas produced from the eagle ford shale following hydraulic fracturing is used to validate the empirical equations calculated thermal regime for the oil production based on the produced gas is located at the peak of oil generation and the beginning of light oil cracking to gas corresponding to tmax from 454 c to 464 c 849 f to 867 f or at an roe ranging from 1 01 to 1 19 empirical equations provide a basis for interpretation of mud gas logging data and produced gas composition

evolution of metamorphic volatiles during exhumation of microdiamond bearing granulites in the western gneiss region norway fluid inclusions in garnet kyanite and quartz from microdiamond bearing granulites in the western gneiss region norway document a conspicuous fluid evolution as the rocks were exhumed following caledonian high and ultrahigh pressure hp uhp metamorphism the most important of the various fluid mixtures and daughter minerals in these rocks are n2 co2 magnesian calcite n2 co2 ch4 graphite magnesian calcite n2 ch4 n2 ch4 h2o co2 and h2o nacl cacl2 nahcolite rutile also occurs in the n2 co2 inclusions as a product of titanium diffusion from the garnet host into the fluid inclusions volatiles composed of n2 co2 magnesian calcite characterise the ambient metamorphic environment between hp uhp peak and early retrograde metamorphism during progressive decompression the mole fraction of n2 increased in the fluid mixtures as amphibolite facies conditions were reached ch4 and later h2o appeared in the fluids concomitant with the disappearance of co2 and magnesian calcite graphite is ubiquitous in the host lithologies and fluid inclusions thermodynamic modelling of the metamorphic volatiles in a graphite buffered c o h system demonstrates that the observed metamorphic volatile evolution was attainable only if the fo2 increased from c 3 5 0 3 to 0 8 0 3 log units relative to the fmq oxygen buffer external introduction of oxidising aqueous solutions along a system of interconnected ductile shear zones adequately explains the dramatic increase in the fo2 the oxidising fluids introduced during exhumation were likely derived from dehydration of oceanic crust and continental sediments previously subducted during an extended period of continental collision in conjunction with the caledonian orogeny

isotopic reversal rollover in shale gases produced from the mississippian barnett and fayetteville formations abstract ethane propane and carbon dioxide show reversed carbon isotopic maturity trends in natural gas produced from the barnett and fayetteville shales at thermal maturities greater than 1 5 vre at this high level of thermal maturity the iso butane to n butane ratio also reverses suggesting wet gas cracking has occurred generating more gas molecules in the same volume resulting in overpressure and increased stabilized production rates in the barnett hydrothermal fluids from the nearby ouachita thrust front apparently enhanced the maturity of the fayetteville and barnett shales water hydrocarbon reactions at these high maturities may account for the isotopic reversals