comparison of smectite and illite rich gouge frictional properties application to the updip limit of the seismogenic zone along subduction megathrusts along plate boundary subduction thrusts the transformation of smectite to illite within fault gouge at temperatures of 150 c is one of the key mineralogical changes thought to control the updip limit of seismicity if correct this hypothesis requires illite rich gouges to exhibit frictionally unstable velocity weakening behavior here we report on laboratory experiments designed to investigate the frictional behavior of natural and synthetic clay rich gouges we sheared 5 mm thick layers of commercially obtained pure ca smectite a suite of smectite quartz mixtures and natural illite shale grain size ranging from 2 to 500 m in the double direct shear geometry to shear strains of 7 30 at room humidity and temperature xrd analyses show that the illite shale contains dominantly clay minerals and quartz within the clay sized fraction 40 mpa our data specifically the velocity strengthening behavior of illite shale under a wide range of conditions do not support the hypothesis that the smectite illite transition is responsible for the seismic aseismic transition in subduction zones we suggest that other depth and temperature dependent processes such as cementation consolidation and slip localization with increased shearing may play an important role in changing the frictional properties of subduction zone faults and that these processes in addition to clay mineralogy should be the focus of future investigation

thermochronological investigation of fault zones abstract the timing of faulting episodes can be constrained by radiometric dating of fault zone rocks fault zone material suitable for dating is produced by tectonic processes such as 1 fragmentation of host rocks followed by grain size reduction and recrystallization to form mica and clay minerals 2 secondary heating melting of host rocks by frictional fault motions and 3 mineral vein formation as a result of fluid advection associated with the fault motions the thermal regime of fault zones consists primarily of the following three factors a regional geothermal structure across the fault zone and background thermal history of studied province bounded by fault systems b frictional heating of wall rocks by fault motions and c heating of host rocks by hot fluid advection in and around the fault zone thermochronological methods widely applied in fault zones are k ar 40ar 39ar fission track and u th methods for which methodological principles as well as analytical procedures are briefly described the thermal sensitivities of individual thermochronological systems are then reviewed which critically control the response of each method against the thermal processes based on the knowledge above representative examples as well as key issues are highlighted to date fault gouges pseudotachylytes mylonites and carbonate veins placing new constraints upon geological geomorphological and seismological frames finally the nojima fault is presented as an example for multiple applications of thermochronological methods in a complex fault zone

performance of an eddy diffusivity mass flux scheme for shallow cumulus boundary layers comparisons between single column scm simulations with the total energy mass flux boundary layer scheme temf and large eddy simulations les are shown for four cases from the gulf of mexico atmospheric composition and climate study gomaccs 2006 field experiment in the vicinity of houston texas the scm simulations were run with initial soundings and surface forcing identical to those in the les providing a clean comparison with the boundary layer scheme isolated from any other influences good agreement is found in the simulated vertical transport and resulting moisture profiles notable differences are seen in the cloud base and in the distribution of moisture between the lower and upper cloud layer by the end of the simulations temf has dried the subcloud layer and moistened the lower cloud layer more than les temf gives more realistic profiles for shallow cumulus conditions than traditional boundary layer schemes which have no transport above the dry convective boundary layer changes to the formulation and its parameters from previous publications are discussed

experimental study for noble gas release and exchange under high speed frictional melting abstract isotope ratios of noble gases in certain minerals are believed to be modified easily by their ambient reservoirs when the minerals reach temperatures that are higher than their closure temperatures the thermal history of a rock or a geologic event even a fault movement can therefore be determined quantitatively by application of radiometric dating methods to different minerals however neither traditional k ar nor ar ar dating methods are readily applicable to faulted rocks because in the case of faulting it is difficult to prove that the temperature of an event was greater than the closure temperatures of minerals frictional melting experiments performed on fine grain homogeneous gabbroid with high temperatures induced by frictional heating using a high velocity friction apparatus were performed to test whether rapid fault movement can reset the noble gas isotope ratio of fault rocks the temperature on the artificial fault plane is much higher than the closure temperature of the k ar system as inferred from the calculated cooling age the anticipated rapid equilibration of volatiles during the frictional melting of rocks implies that the noble gas isotope composition ratio was reset to an atmospheric value during this experiment we measured noble gas isotopes in a gabbroid sample using laser fusion analysis the resetting of noble gases is only observed in glass that had melted completely rejuvenation and or apparent increases in the k ar ages were only observed in a narrow 3 mm wide zone around the fault plane which appears to be thermally altered and mechanically fractured in thin sections because of frictional heating such glassy materials called pseudotachylytes sometimes form along the fault plane in natural faults as a result of complete melting of rock induced by frictional heating thus these results suggest that k ar ages of fault activity can be quantitatively obtained from the analysis of pseudotachylytes

large eddy simulation of shallow cumulus over land a composite case based on arm long term observations at its southern great plains site abstractbased on long term observations by the atmospheric radiation measurement program at its southern great plains site a new composite case of continental shallow cumulus shcu convection is constructed for large eddy simulations les and single column models the case represents a typical daytime nonprecipitating shcu whose formation and dissipation are driven by the local atmospheric conditions and land surface forcing and are not influenced by synoptic weather events the case includes early morning initial profiles of temperature and moisture with a residual layer diurnally varying sensible and latent heat fluxes which represent a domain average over different land surface types simplified large scale horizontal advective tendencies and subsidence and horizontal winds with prevailing direction and average speed observed composite cloud statistics are provided for model evaluation the observed diurnal cycle is well reproduced by les however the cloud amount liquid water path and shortw

k ar illite age constraints on the proterozoic formation and reactivation history of a brittle fault in fennoscandia k ar ages of authigenic illite from two drill core gouge samples of a fault in the palaeoproterozoic basement of finland record two distinct faulting events the older sample yields apparent ages from 1240 26 to 1006 21 ma for four grain size fractions between 6 and 0 1 m the second sample is structurally younger and yields statistically distinct ages ranging from 978 20 to 886 18 ma we interpret the ages of the 0 1 m fractions which are the youngest as representing the actual time of faulting xrd analysis and age modelling exclude significant age contamination of the finest dated fractions with inherited host rock components these results provide therefore an example of meaningful isotopic dating of illite type clay material formed during precambrian faulting demonstrate and constrain fault reactivation and give evidence for brittle sveconorwegian mesoproterozoic shortening and neoproterozoic extension in fennoscandia

characteristics of fluid inclusions and implications for the timing of hydrocarbon accumulation in the cretaceous reservoirs kelasu thrust belt tarim basin china abstract the kelasu thrust belt is a key area for oil and gas exploration within the tarim basin of china an area containing abundant oil and gas resources but where the processes that controlled hydrocarbon accumulation remain unclear this study reconstructs the accumulation history of hydrocarbons within the kelasu thrust belt by studying multiple sets of fluid inclusions from the cretaceous reservoirs using laser raman infrared spectroscopy fluorescence spectroscopy total scanning fluorescence and ptv simulation analyses the resulting data yield the following results 1 three types of cretaceous hydrocarbon bearing fluid inclusions are present and they record three periods of hydrocarbon accumulation period i involved low maturity medium oil as recorded by the presence of yellow green fluorescent oil inclusions with this accumulation occurring between the neogene jidike and kangcun stages 20 5 ma period ii involved high maturity light oils or condensates that are recorded by the presence of blue white fluorescent oil inclusions with this accumulation occurring during the early kuche stage 5 2 5 ma period iii involved the significant accumulation of gas as recorded by non fluorescent gas inclusions during and after the late kuche stage 2 5 0 ma 2 inclusion pvt simulations indicate that the pressures during the trapping of oil inclusions within the west kelasu reservoirs increase with increasing capture temperature suggesting that west kelasu cretaceous oil reservoirs formed over a short period of time in contrast the trapping pressures of oil inclusions within the east kelasu area are invariant with increasing trapping temperature indicating that the formation of east kelasu cretaceous oil reservoirs was a relatively slow and gradual process this most likely relates to the fact that the east kelasu reservoirs are close to the hydrocarbon generation centre in an area with sufficient hydrocarbon supply with hydrocarbon accumulation processes involving all of the stages of hydrocarbon generation recorded by the source rocks in this area in comparison the west kelasu reservoirs are far from the hydrocarbon generation centre and as such record only one phase of oil filling 3 significant tectonism associated with the uplift of the south tianshan mountain during the late kuche stage caused widespread changes to cretaceous paleo oil reservoirs in this area this led to some cretaceous paleo oils being transported to shallower traps to form secondary oil reservoirs whereas others were transported to the surface and were lost with residual paleo oils were also changed to condensate gas as a result of gas washing after the addition of large amounts of late stage gas

water washing of proterozoic oil in the midcontinent rift system whole oil gas chromatography shows that petroleum inclusions trapped in 1 05 ga veins in the midcontinent rift experienced variable water washing but no significant biodegradation or phase separation by comparing our results with published experimental data we estimate that water petroleum ratios varied from 200 1 to much greater than 9000 1 extreme water washing with water petroleum ratios very much greater than 9000 1 likely produced pyrobitumen solid hydrocarbon that was locally trapped as primary inclusions in vein calcite hydrothermal ore deposits with their extremely high water rock ratios are one of the best places to search for end member water washed petroleum sedimentary basins however with their variable water rock ratios also have a wide range of water petroleum ratios which significantly affect the composition of crude oils along the flow path between source rock and trap water petroleum ratios may be a useful concept to help evaluate crude oil compositions in a variety of settings

on the mechanical role of smectite in subduction zones smectites a group of hydrated phyllosilicate minerals are often a main component of sediments entering a subduction zone they are common in hemipelagic sediments and consist of an authigenetic component that arises from the alteration of volcanic ash intercalated in the sediment and a detrital component smectite rich strata are structurally weak retain water and are highly porous a review of sediment lithology in subduction zones around the world suggests that decollement zones may preferentially form in smectite rich horizons one consequence of this observation is that the assignment of high frictional resistance to materials in a decollement may be unwarranted at deeper structural levels smectite is transformed to illite a mechanically stronger mineral estimates of the depth of this transition coincide with the depth at which earthquakes are first detected along plate interfaces i speculate that the smectite illite transition in subduction zones may be an important component of sediment consolidation processes that trigger interplate seismicity

assessing the maturity of oil trapped in fluid inclusions using molecular geochemistry data and visually determined fluorescence colours abstract the thermal maturity of oils extracted from inclusions and the fluorescence colours of oil bearing fluid inclusions have been measured in 36 sandstone samples from australasian oil fields the inclusion oils were analysed using an off line crushing technique followed by gc ms a maturity assessment was made for each inclusion oil using 25 molecular maturity ratios including a newly defined dimethyldibenzothiophene ratio dmdr each inclusion oil was placed in one of 4 maturity brackets approximately equivalent to early mid peak and post oil generation windows the fluorescence colours of oil inclusions were visually discriminated into blue white and yellow plus orange and their proportions estimated using point counting techniques sixteen samples have 85 of oil inclusions with blue fluorescence whilst other samples have more variable fluorescence colours one sample has 100 of oil inclusions with yellow plus orange fluorescence the results show that samples containing mainly blue fluorescing oil inclusions have thermal maturities anywhere within the oil window in particular the molecular geochemical data strongly suggests that oil inclusions with blue fluorescence can have relatively low maturities calculated reflectance

the k ar and 40ar 39ar methods revisited for dating fine grained k bearing clay minerals abstract the strengths and weaknesses of the two ar isotopic methods k ar and 40ar 39ar were evaluated on the basis of respective recent applications mainly on low temperature k bearing illite type clay minerals this review includes a presentation of basic analytical and technical aspects for both methods as well as a discussion of varied claims on the two methods and of requests about sample preparation and characterization whenever possible the advantages and weaknesses of each method were compared on coeval results obtained by both methods on the same mineral separates the comparative review examines stratigraphic dating of glauconites indirect dating of low temperature ore deposits dating of burial related illitization and dating of polyphased tectono thermal activity more specifically of fault gouges some pending questions such as the necessary encapsulation due to 39ar recoil and its restoration into step heating patterns are also raised together with the new potential of ar dating of nanometric illite crystals weakness of the k ar method is in its pioneering status that makes many believe that it is no longer accurate because of its traditional analytical aspects and of the k determinations leading to somewhat large uncertainties however precise evaluation of varied applications points to a k ar method having probably larger applicability in sedimentary to diagenetic environments than the 40ar 39ar method the drawbacks become less important if the method is applied to nanometer sized clay minerals in diagenetic to low grade metamorphic environments in this instance the extracted size fractions are generally homogeneous and the relative uncertainty given by the age calculations if mathematically justified can be reduced by duplicate analyses weakness of the 40ar 39ar method is in its basics such as the 39ar recoil the necessary encapsulation the reintegration of the 39ar into the step heating patterns and the meaning of the step heating patterns that are more suggestive of variable 39ar reservoirs created among the clay particles by irradiation than of meaningful geologic ages if the k ar method is the preferred method for dating diagenetic clay processes such as glauconitization illite crystal nucleation and growth or low temperature hydrothermal activities then the 40ar 39ar method has more potential in dating low temperature tectono thermal activities and in detailing mixtures of multi generation illite

40ar 39ar dating of white micas from an alpine high pressure metamorphic belt on naxos greece the resetting of the argon isotopic system overprinting of white micas from high pressure low to medium temperature m1 metamorphic assemblages in pelitic schists on naxos during subsequent thermal dome m2 metamorphism ranges from minor in the southeast of the island to complete recrystallization in the amphibolite facies rocks near the migmatites in the centre of the dome the original m1 minerals are phengites si4 6 7 7 0 and the overprinting minerals are muscovites si4 6 0 6 45 40ar 39ar step heating analyses of white mica separates from rocks in the area where phengite and muscovite occur together yield complex age spectra characterized by low apparent ages in the first and the last stages of gas release and high apparent ages in between these upward convex age spectra are shown to be caused by mixing of two generations of micas each of which has a different age spectrum and argon release pattern seemingly good plateaus in some age spectra from white micas of the area must be interpreted as providing meaningless intermediate ages further the upward convex age spectra have been used to trace the isotopic signature of phengites toward increasing m2 metamorphic grade and suggest that as long as phengites can be observed in the rocks upward convex age spectra occur on naxos crystallization of muscovite at the expense of phengite appears to be the main mechanism of resetting argon isotopic ages in white micas however there is also good evidence for argon loss by volume diffusion from phengites simple diffusion calculations suggest that the m2 metamorphism was caused by a shortlived heat source

timing of alpine fault gouges k ar ages from clay rich fault gouges in the european alps are consistent internally with established field constraints and with fission track ages demonstrating the applicability of this method for direct dating of brittle deformation illite grown by retrograde hydration of granitic and or high grade metamorphic protoliths is the major k bearing mineral in the fractions that have been separated 0 1 to 6 10 m the ages obtained are bracketed by apatite and zircon fission ages from adjacent localities this together with the interpreted cooling curve for one well constrained sample from the simplon fault indicates that illite grew or the k ar isotopic system in illite closed at temperatures in the range 120 150 c consistent with the stability of illite alone rather than illite smectite average ages obtained for fractions finer than 2 m were 1 5 2 2 6 ma 2 for 11 analyses from the detachment and footwall of the simplon fault 2 8 8 0 6 ma for four analyses from the centovalli fault at trontano 3 19 9 2 6 ma for two analyses from a major riedel fault related to the periadriatic fault offsetting the tertiary bergell tonalite at gesero 4 21 5 5 5 ma for two analyses from a zone parallel to the periadriatic fault in the adjacent southern alps in val morobbia and 5 14 5 3 9 ma for two analyses from a gouge zone on the northern rim of the tertiary mauls tonalite in the eastern alps the ages from the simplon centovalli and periadriatic faults are not identical and do not lend support to models linking these three faults as a single coeval structure

paleofluid flow circulation within a triassic rift basin evidence from oil inclusions and thermal histories the migration of subsurface fluid flow within continental rift basins has been increasingly recognized to significantly affect the thermal history of sediments and petroleum information to gain insight into these paleofluid flow effects the thermal history of the taylorsville basin in virginia was reconstructed from fluid inclusion studies apatite fission track data and vitrinite reflectance data models of thermal history indicate that the basin was buried to the thermal maximum at 200 ma a cooling event followed during which the eastern side of the basin cooled earlier and faster than the western side suggesting that there was a differential uplift and topographically driven fluid flow this hypothesis is supported by analyses of secondary oil and aqueous inclusions trapped in calcite and quartz veins during the uplift stage gas chromatograms of inclusion oils exhibit variable but extensive depletion of light molecular weight hydrocarbons the relative abundance of n alkanes petrographic observations and the geological data indicate that the alteration process on these inclusion oils was probably neither phase separation nor biodegradation but water washing water oil ratios necessary to produce the observed alteration are much greater than 10 000 1 these exceedingly high ratios are consistent with the migration of inclusion oils along with fluid flow during themore early stages of basin evolution the results provide significant evidence about the role of a subsurface flow system in modifying the temperature structure of the basin and the composition of petroleum generated within the basin less

characterisation of fluid inclusion oil in a mid proterozoic sandstone and dolerite roper superbasin australia detailed geochemical analysis has been carried out on fluid inclusion oils trapped for over 1 billion years in the roper superbasin northern australia in two different geological settings in healed microfractures in a quartz arenite and within partially altered plagioclase laths in a dolerite sill the oil inclusions and co occurring solid bitumens record multiple oil migration events postdating an intrusive episode ca 1300 ma most likely during neoproterozoic basin inversion solid bitumen represents the oldest migration event and occurs in secondary pore space within the bessie creek sandstone and in veins cross cutting the dolerite sill it is interpreted to represent thermally altered oil that may have at least partly been generated by contact metamorphism near the igneous intrusion inclusion oils in both the dolerite feldspar and in the transgranular fractures in the bessie creek sandstone are pristine nonbiodegraded fluids with a great similarity to other bitumens oils and sediment extracts from the roper superbasin biomarkers indicate that the oils were mainly sourced from prokaryotic cyanobacterial organic matter with a small contribution from eukaryotes based on migration distance organic richness geochemistry and similarity of source rock maturity the velkerri formation which directly overlies the dolerite sill and the bessie creek sandstone is the most likely source rock for the higher molecular weight hydrocarbons preserved in the fluid inclusion oils geochemical data indicate that the oil inclusions in clusters in albitised zones of labradorite crystals in the dolerite matrix represent a different migration event from oil inclusions in transcrystalline fractures in vein calcite in the dolerite sill and in transgranular fractures in quartz in the bessie creek sandstone the bessie creek sandstone fluid inclusion oil was generated in the peak to late oil window 0 9 1 0 vre the higher molecular weight c13 proportion of the dolerite feldspar fluid inclusion oil is of lower maturity 0 8 vre than the same molecular weigh range fluid in the bessie creek sandstone fluid inclusion oil both of these oils were most likely generated in the overlying velkerri formation however the volumetrically dominant low molecular weight hydrocarbons in the dolerite feldspar fluid inclusion oils have a higher maturity 1 3 vre and may have been generated from the deeper ca 1600 ma barney creek formation in the underlying mcarthur group this study shows that oil trapped in fluid inclusions has a greater potential to preserve pristine organic geochemical information than porosity bound oils and dispersed kerogen if oil inclusions occur in sufficient abundance the analysis of these tiny oil encapsulations is technically feasible and can give valuable information on the composition of the earth s early biosphere and precambrian petroleum systems

the recognition of reactivation during continental deformation reactivation involves the accommodation of geologically separable displacement events intervals 1 ma along pre existing structures the definition of a significant period of quiescence is central to this phenomenological definition and the duration of the interval chosen represents the resolution limit of reactivation criteria found in most ancient settings in neotectonic environments reactivation can be further defined as the accommodation of displacements along structures that formed prior to the onset of the current tectonic regime this mechanistic definition cannot always be applied to ancient settings due to the uncertainties in constraining relative plate motion vectors four sets of criteria may be used to recognize reactivation in the geological record stratigraphic structural geochronological and neotectonic some structural criteria may not be reliable if used in isolation to identify reactivated structures much of the previously published evidence cited to invoke structural inheritance is equivocal as it uses similarities in trend dip or three dimensional shape of structures numerous fault and shear zone processes can cause significant weakening both synchronously with deformation and in the long term and may be invoked to explain reactivation the collage of fault bounded blocks forming most continents therefore carries a long term architecture of inheritance which can explain much of the observed complexity of continental deformation zones

geochemistry of oil in fluid inclusions in a middle proterozoic igneous intrusion implications for the source of hydrocarbons in crystalline rocks abstract the ca 1280 ma dolerite sill within the mesoproterozoic roper group in the roper superbasin australia contains evidence for at least two episodes of hydrocarbon migration represented respectively by solid bitumen with a ketone rich extract and a mixture of a high maturity gas condensate and a lower maturity oil within oil bearing fluid inclusions the ketone isomers are formed by flash pyrolysis of kerogen during the intrusion of the dolerite sill org geochem 21 1994 829 and represent the first and oldest phase of hydrocarbon migration the gas condensate and oil were subsequently trapped as a mixture within fluid inclusions at diagenetic temperatures and pressures of around 110 c and 250 bars significantly after cooling of the sill and likely during the neoproterozoic reactivation of the roper superbasin either 1 these fluids migrated together and mixed in the reservoir or 2 an earlier oil charge was flushed by a later condensate charge and the oil condensate mixture was trapped within single fluid inclusions oil inclusions occur chiefly within albitised zones of labradorite laths within the dolerite matrix and within transcrystalline microfractures cutting vein calcite and rarely vein quartz oil inclusions trapped in the vein calcite are accompanied by hypersaline ca mg brines gas chromatography mass spectrometry of oil extracted from inclusions within the dolerite matrix shows that the oil is non biodegraded and was therefore trapped relatively quickly within the host minerals trace amounts of biomarkers indicate that the inclusion oil is of a biogenic origin and excludes any abiotic processes that are apparent sources of hydrocarbons in many crystalline rocks monomethylalkanes pentacyclic terpanes chiefly comprising hopanes and diahopanes and very low concentrations of steranes and diasteranes indicate input from cyanobacterial organic matter with a minor contribution from eukaryotes the hydrocarbons are likely derived from proterozoic source rocks such as the directly overlying velkerri formation and or the underlying barney creek formation from the mcarthur group the study has implications for the source of hydrocarbons in non sedimentary rocks and suggests that fluid inclusions can be used not only to distinguish between biogenic and abiogenic sources of hydrocarbons but also to provide critical information about the composition of the biomass fluid migration events and conditions under which hydrocarbons in different geological settings are trapped

k ar dating of synkinematic clay gouges from neoalpine faults of the central western and eastern alps abstract with ongoing alpine convergence and deformation during exhumation there is a general progression from ductile to brittle behaviour on the periadriatic fault and kinematically related faults farther north e g the simplon rhone fault and a diffuse discontinuous zone of generally dextral strike slip movement on the southern boundary of the aar massif k ar dating of fine grained illite from clay fault gouges provides a reliable method for establishing the maximum age of this transition to brittle faulting and for short lived faults the approximate time of faulting itself the new results establish that brittle faulting on the northeastern segment of the canavese fault i e the part of the periadriatic fault southwest of lago maggiore occurred around 20 ma with south side up kinematics a k ar age of ca 17 ma for the crosscutting giudicarie fault in the eastern alps is effectively identical with an already published pseudotachylyte age and places a lower limit on major and continuous strike slip movements of the periadriatic fault the age of brittle faulting farther north on the southern border of the aar massif is from 13 6 0 3 to 8 3 1 1 ma consistent with the younger cooling and exhumation in this area the dominantly dextral brittle faulting becoming younger to the north reflects the continued indentation and anticlockwise rotation of adria as alpine units become exhumed and progressively welded to the southern block in contrast to the eastern alps there is no field evidence for westward lateral extrusion of alpine units relative to adria and the european foreland

laser ablation gc ms analysis of oil bearing fluid inclusions in petroleum reservoir rocks abstract the hydrocarbon composition of co occurring blue and yellow fluorescing fluid inclusions fis in ordovician reservoirs of the tarim basin nw china have been separately analyzed by laser microprobe gas chromatography mass spectrometry gc ms using a 193 nm excimer laser to drill through the host quartz a newly designed gc inlet system enabled detection of c4 c30 hydrocarbons extending the molecular weight significantly beyond the c21 limit of previous online laser based hydrocarbon analysis of oil inclusions the blue fluorescing inclusions contain notably higher proportions of aliphatic hydrocarbons e g n alkanes cycloalkanes and gaseous range products whereas the yellow fluorescing inclusions contain relatively more aromatic hydrocarbons e g alkylnaphthalenes hydrocarbon based parameters also indicate that the blue fluorescing inclusions are of higher thermal maturity than the yellow fluorescing inclusions consistent with maturity estimates based on fluorescence colors the compositional differences of the co occurring inclusions are indicative of different oil types and charge events this highlights the capacity of the new laser ablation technology to separately analyse specific inclusions amongst a mixture of inclusions of different fluorescing colors in the future integration of this new compositional detail with other inclusion and reservoir data will help reconstruct the oil charge history of the tarim basin

comparative 40ar 39ar and k ar dating of illite type clay minerals a tentative explanation for age identities and differences abstract the 40 k 40 ar k ar and 40 ar 39 ar dating methods are applied here to the same very small micrometric illite type particles that crystallized under low temperature 5 9 ma the same size fractions dated by the 40 ar 39 ar method give total gas ages ranging from 173 3 2 0 to 228 8 1 6 ma nearly all 40 ar 39 ar total gas ages are slightly older which cannot be explained by the recoil effect only the impact of which being amplified by the inhomogeneous shape of the clay minerals and their crystallographic characteristics with varied crystallinity indices and a particle width about 10 times large than thickness the 40 ar 39 ar data outline some advantages such as the plateaus obtained by incremental step heating of the various size fractions even if not translatable straight as ages of the illite populations they allow identification of two generations of authigenic illite that formed at about 200 and 175 ma and one detrital generation however 40 ar 39 ar dating of clay minerals remains challenging as technical factors such as the non standardized encapsulation may have potential unexpected effects both dating methods have their limitations 1 k ar dating requires relatively large samples ca 10 20 mg incurring potential sample homogeneity problems with two aliquots required for k and ar analysis for an age determination also inducing a higher analytical uncertainty 2 an identified drawback of 40 ar 39 ar dating is ar recoil and therefore potential loss that occurs during neutronic creation of 39 ar from 39 k mostly in the finer mineral particles if all the recoiled 39 ar is redistributed into adjacent grains minerals the final 40 ar 39 ar age of the analyzed size fraction remains theoretically identical but it is not systematic in clay type material the finest grain sizes e g 39 ar recoil and are therefore only datable by the 40 ar 39 ar method using an encapsulation technique that still needs to be technically evaluated in this study 39 ar recoil during irradiation was quantified by encapsulation it ranged from about 20 of the total 39 ar for the 39 ar recoil confirms that grain size increasing minimizes the recoil effect but how it proceeds has still to be explained despite recent developments in 40 ar 39 ar dating the conventional k ar method is still a valuable tool for clay dating due to a convenient and straightforward use supported by a standardized and well controlled technical approach the present comparison of the two ar dating methods as applied to clay material shows that neither method is presently outdated and that they are even of reciprocal use both methods have distinct application fields in clay geochronology and complementary application fields in clay crystallography

a dual mass flux framework for boundary layer convection part ii clouds this paper presents the extension of the eddy diffusivity mass flux edmf framework for turbulent transport into the statistical modeling of boundary layer clouds the advection diffusion decomposition that defines edmf is projected onto the turbulent distribution as used in the statistical cloud model each edmf component is thus assigned its own independent probability density function pdf resulting in an updraft pdf and a diffusive pdf this double pdf system is configured and integrated in conserved variable space with the position and orientation of each pdf determined by its unique nature the parameterization of the associated updraft diffusion decomposition of variance introduces close ties to the transport scheme whereas the grid box mean variance is reconstructed using a prognostic variance budget the variance of the updraft component is parameterized as a function of the spread among various resolved model updrafts individual model components and the scheme as a whole are evaluated in detail against large eddy simulations of a number of prototype subtropical trade wind cases the results show that various structures in cloud fraction condensate and variance are reproduced the diffusive pdf acts to represent stratiform clouds the advective pdf represents cumuliform clouds in conditionally unstable layers this allows representation of complex scenarios in which both cloud forms occur such as the transitional trade wind regime featuring cumulus rising into stratocumulus

episodic mineralization of hydrothermal illite in the soultz sous forets granite upper rhine graben france episodic and localized illite mineralization is documented in the hydrothermally altered soultz sous forets granite upper rhine graben france separated grain size fractions of altered granite and argillite vein samples contain mixtures of 2m1 and 1m trans vacant illite varieties the platy pseudohexagonal 2m1 illite phases dominate the vein fillings whereas the 1m illite occurs largely as a fibrous pore filling variety which is particularly abundant in the granite matrix multiple phases of fluid injections into the granite body have resulted in different illite assemblages each sample containing a mixture of polytype generations formed during different crystal growth events on the basis of mineralogical and k ar isotopic constraints the ages of these vein mineralizing events are determined by plotting the k ar values of the various grain size fractions against polytype abundance and the fitted volume weighted crystallite thickness distributions the results suggest a permian age for the formation of the studied argillite veins characterized by successive injections of hydrothermal fluids secondary episodes of illite crystallization occurred during jurassic and cretaceous or even younger times in both the veins and the granite matrix there are indications that the polytype structure and composition of illite were strongly influenced by variations in fluid chemistry and the degree of fluid rock interaction as the granite was progressively sealed during post variscan episodic hydrothermal activity

the effect of sub seismic fault slip processes on the isotopic signature of clay minerals implications for k ar dating of fault zones abstract clay minerals are abundant in fault gouges and isotope dating of the radiogenic noble gases that they contain may be used to constrain timing of fault initiation reactivation and to estimate recurrence intervals of earthquakes the potential influence of fault slip and ambient temperature on the isotope signature of authigenic clay minerals however remains unknown this study reports measurements of the k ar isotope signature of samples that have been sheared experimentally at sub seismic slip rates within a range of ambient temperatures as well as of samples undergoing standardised clay heating degas experiments in the investigation and comparison of the influence of sub seismic frictional slip and external heating on clay gouge the age data confirm that the sub seismic frictional slip of clay gouge affects the clay microstructures and releases radiogenic 40ar the experimental data indicate that radiogenic 40ar release due to external heating can be disregarded until 350 c which is supported by ar diffusion modelling frictional slip at sub seismic slip rates and at room temperature results in a significant radiogenic 40ar loss of 56 and the remaining clay will inherit 44 of radiogenic 40ar sub seismic frictional slip experiments at imposed elevated temperatures from 150 to 450 c increase the amount of radiogenic 40ar loss and decrease the amount of inherited radiogenic 40ar at a relatively high temperature of 450 c about 16 of radiogenic 40ar will be present in the remaining sample portion reinforcing the importance of rigorous clay grain size separation processes required prior to fault gouge dating

large eddy simulation of the diurnal cycle of shallow cumulus convection over land summary large eddy simulations of the development of shallow cumulus convection over land are presented many characteristics of the cumulus layer previously found in simulations of quasi steady convection over the sea are found to be reproduced in this more strongly forced unsteady case furthermore the results are shown to be encouragingly robust with similar results obtained with eight independent models and also across a range of numerical resolutions the datasets produced are already being used in the development and evaluation of parametrizations used in numerical weather prediction and climate models

hydrogeologic constraint on the origin of deep subsurface microorganisms within a triassic basin the thermal history of the taylorsville basin indicates that the thermophilic anaerobic bacteria extracted from triassic strata at 2800 m below the land surface within the basin probably migrated to their current location in order to ascertain the most probable scenario for microbial transport a two dimensional transient fluid flow and heat transport model of the taylorsville basin was developed using the finite element method the numerical model was constrained by tectonic and thermal histories of the basin coupled with the permeability and porosity data extracted from core samples the model demonstrates that a topographically driven groundwater flow system caused by the tectonic uplift and erosion during the jurassic can explain the observed differential cooling of the basin the computed groundwater flow rates during this period were on the order of 1 to 100 mm yr combined with the cooling history of the microbially sampled strata such rates provided a possible mechanism for the introduction of ancient surface or subsurface microorganisms to the deep subsurface this tectogenetic mechanism may explain the origins of deep subsurface microorganisms for other regions of the earth

the effect of land surface heterogeneity and background wind on shallow cumulus clouds and the transition to deeper convection abstractidealized large eddy simulations less with prescribed heterogeneous land surface heat fluxes are performed to study the impact of the heterogeneity length scale and background wind speed

illite k ar dating and crystal growth processes in diagenetic environments a critical review k ar dating of illitic minerals is commonly used in studies of diagenetic series applied to oil prospecting in spite of a great number of specialized papers some problems remain unresolved these are mostly due to a misunderstanding of the argon accumulation process during illitization criteria for identifying detrital authigenic mineral mixtures crystal ripening fast precipitation or continuous nucleation growth processes are discussed using k ar data available in the literature using different parameters such as age agek ar agestrati cryst diagenetic agek ar agestrati or frac agek arfraction agek arfinest it is shown that the k ar age significance depends on the illite nucleation growth processes a diagenetic age is obtained when these processes are rapid the k2o accumulation period is shorter than 2 if lower than this value the k ar ratio depends on the proportions of new and old particles respectively which are controlled by the relative rates of nucleation crystal growth and ripening

subsiding shells around shallow cumulus clouds abstract in this study large eddy simulations les are used to gain more knowledge on the shell of subsiding air that is frequently observed around cumulus clouds first a detailed comparison between observational and numerical results is presented to better validate les as a tool for studies of microscale phenomena it is found that horizontal cloud profiles of vertical velocity humidity and temperature are in good agreement with observations they show features similar to the observations including the presence of the shell of descending air around the cloud second the availability of the complete 3d dataset in les has been exploited to examine the role of lateral mixing in the exchange of cloud and environmental air the origin of the subsiding shell is examined by analyzing the individual terms of the vertical momentum equation buoyancy is found to be the driving force for this shell and it is counteracted by the pressure gradient force this shows that evaporative cooling at the cloud edge

using argon as a temporal tracer of large scale geologic processes abstract argon ar has proven to be one of the most useful elements in understanding the timing and duration of geological processes because of its chemical and physical properties ar is a particularly sensitive indicator of temperature variations associated with large scale geological events ar mobility in minerals is commonly described using solid state diffusion theory volume diffusion which has been used extensively to model diffusion profiles and closure temperatures in minerals because 40 ar is the radiogenic daughter product of radioactive 40 k and therefore occurs in many common rock forming minerals ar has been used effectively as a temporal tracer to understand a wide variety of geological phenomena ar isotopes have been applied with great success in three broad fields of earth science the origin and evolution of the earth s atmosphere the tectonothermal history of geologic terranes and the timing and duration of large scale tectonic events from ar isotopic data the earth s atmosphere is now known to be mainly secondary in nature although evolutionary models have undergone a recent paradigm shift due to geophysical evidence moving away from the earlier notion of a chemically layered upper and lower mantle to a whole earth mantle structure that may be chemically inhomogeneous although recent models are growing in sophistication by integrating additional information and measurements reflecting the behaviour of other noble gases through time the temporal evolution of the earth s atmosphere still remains ambiguous because measured compositions of ancient atmosphere are sparse and remain difficult to obtain 40 ar 39 ar thermochronology is one of the most commonly used tools in tectonothermal investigations because of the large range of ar closure temperatures recorded by various common k bearing minerals although more recent thermochronological models such as multidiffusion domain mdd modelling remain controversial the combination of 40 ar 39 ar thermochronology with both higher and lower temperature thermochronological methods utilizing other isotopic systems makes this an extremely versatile method of understanding the temperature time evolution of geologic regions recent developments involving the numerical modelling of ar diffusion coupled with the geodynamic modelling of orogens have led to new ways of estimating the timing and duration of a complete tectonic cycle of subduction and exhumation by applying these new methods to rocks from the bergen arcs in norway studies have shown that this cycle can be so rapid that the subducted and exhumed crust can remain relatively cool never achieving thermal equilibrium with its ambient environment throughout the entire process in summary the versatility of the 40 ar 39 ar dating method combined with the effective application of various techniques e g laser spot dating and step heating and a detailed understanding of the diffusional behaviour of ar has proven to be a powerful research tool in elucidating the timing and duration of many large scale earth system processes

a combined eddy diffusivity mass flux approach for the convective boundary layer a better conceptual understanding and more realistic parameterizations of convective boundary layers in climate and weather prediction models have been major challenges in meteorological research in particular parameterizations of the dry convective boundary layer in spite of the absence of water phase changes and its consequent simplicity as compared to moist convection typically suffer from problems in attempting to represent realistically the boundary layer growth and what is often referred to as countergradient fluxes the eddy diffusivity ed approach has been relatively successful in representing some characteristics of neutral boundary layers and surface layers in general the mass flux mf approach on the other hand has been used for the parameterization of shallow and deep moist convection in this paper a new approach that relies on a combination of the ed and mf parameterizations edmf is proposed for the dry convective boundary layer it is shown that the edmf approach follows naturally from a decomposition of the turbulent fluxes into 1 a part that includes strong organized updrafts and 2 a remaining turbulent field at the basis of the edmf approach is the concept that nonlocal subgrid transport due to the strong updrafts is taken into account by the mf approach while the remaining transport is taken into account by an ed closure large eddy simulation les results of the dry convective boundary layer are used to support the theoretical framework of this new approach and to determine the parameters of the edmf model the performance of the new formulation is evaluated against les results and it is shown that the edmf closure is able to reproduce the main properties of dry convective boundary layers in a realistic manner furthermore it will be shown that this approach has strong advantages over the more traditional countergradient approach especially in the entrainment layer as a result this edmf approach opens the way to parameterize the clear and cumulus topped boundary layer in a simple and unified way

the evolution of illite to muscovite mineralogical and isotopic data from the glarus alps switzerland thirty five illite and muscovite concentrates were extracted from triassic and permian claystones shales slates and phyllites along a cross section from the diagenetic alpine foreland tabular jura and borehole samples beneath the molasse basin to the anchi and epimetamorphic helvetic zone of the central alps concentrates and thin sections were investigated by microscopic x ray infrared mossbauer thermal dta and tg wet chemical electron microprobe k ar rb sr 40ar 39ar and stable isotope methods with increasing metamorphic grade based on illite crystallinity data xrd and ir the following continuous changes are observed i the 1md 2m1 polymorph transformation is completed in the higher grade anchizone ii k2o increases from 6 8 wt diagenetic zone to 8 5 10 anchizone to 10 11 5 epizone reflecting an increase in the total negative layer charge from 1 2 to 2 0 iii a decrease of the chemical variation of the mica population with detrital muscovite surviving up to the anchizone epizone boundary iv a shift of an endothermic peak in differential thermal curves from 500 to 750 c v k ar and rb sr apparent ages of the fraction 2 m decrease from the diagenetic zone to the epizone k ar ages being generally lower than rb sr ages the critical temperature for total ar resetting is estimated to be 260 30 c k ar and rb sr ages become concordant when the anchizone epizone boundary is approached the stable isotope data on the other hand show no change with metamorphic grade but are dependent on stratigraphic age these results suggest that the prograde evolution from 1 md illite to 2m1 muscovite involves a continuous lattice restructuration without rupture of the tetrahedral and octahedral bonds and change of the hydroxyl radicals however this is not a recrystallization process this restructuration is completed approximately at the anchizone epizone boundary the isotopic data indicate significant diffusive loss of 40ar and 87sr prior to any observable lattice reorganization the restructuration progressively introduces a consistent repartition of ar and k in the mineral lattices and is outlined by the 40ar 39ar age spectra concordant k ar and rb sr ages of around 35 30 ma with concomitant concordant 40ar 39ar release spectra are representative for the main phase of alpine metamorphism calanda phase in the glarus alps a second age group between 25 and 20 ma can probably be attributed to movements along the glarus thrust ruchi phase while values down to 9 ma in regions with higher metamorphic conditions suggest thermal conditions persisting at least until the middle tortonian

a dual mass flux framework for boundary layer convection part i transport abstract this study considers the question of what is the least complex bulk mass flux framework that can still conceptually reproduce the smoothly varying coupling between the shallow convective cloud layer and the subcloud mixed layer to this end the model complexity of the classic single bulk mass flux scheme is enhanced inspired by recent large eddy simulation results the authors argue that two relatively minor but key conceptual modifications are already sufficient to achieve this goal i retaining a dry transporting updraft in the moist limit and ii applying continuous updraft area partitioning to this dual mass flux dualm framework the dry updraft represents all internal mixed layer updrafts that terminate near the mixed layer top whereas the moist updraft represents all updrafts that condense and rise out of the mixed layer as buoyant cumulus clouds the continuous area partitioning between the dry and moist updraft is a function of moist convective inhibition above the mixed layer top

alternative methods for specification of observed forcing in single column models and cloud system models we discuss alternative methods for prescribing advective tendencies in single column models scms and cloud system models these include revealed forcing in which the total advective tendency is prescribed from observations horizontal advective forcing in which the horizontal advective tendencies are prescribed together with the observed vertical motion which is combined with the predicted sounding to determine the tendencies due to vertical advection and relaxation forcing in which the horizontal advective tendencies are computed by relaxing the sounding toward the observed upstream sounding with a relaxation timescale determined by the time required for the wind to carry parcels across the grid column when relaxation forcing is used the horizontal advective tendencies can be diagnosed from the model output and compared with the corresponding observed tendencies we present scm results to illustrate these three forcing methods based on data from several field experiments in both the tropics and the midlatitudes each method is shown to have its strengths and weaknesses overall the results presented here do not show unambiguous differences between revealed forcing and horizontal advective forcing the two methods appear to be generally comparable revealed forcing may therefore be preferred for its simplicity relaxation forcing guarantees realistic soundings of the state variables but can produce large errors in parameterized processes which are driven by rates e g fluxes rather than states in particular relaxation forcing gives large errors in the precipitation rate in this model we demonstrate that relaxation forcing leads to unrealistically high low precipitation in versions of the model which tend to produce unrealistically dry humid soundings the observed horizontal advective tendencies in the tropics are so weak especially for temperature that small absolute errors in the diabatic tendencies diagnosed with relaxation forcing can lead to large relative errors in the diagnosed horizontal advective tendencies

direct dating of eocene reverse faulting in northeastern tibet using ar dating of fault clays and low temperature thermochronometry abstract paired together fault gouge dating and low temperature thermochronometry overcome the limitations and assumptions inherent in each independent technique here we establish timing of brittle faulting along the west qinling fault of northeastern tibet by dating several size fractions of fault gouge clay that represent variable populations of illite polytypes results show that the authigenic or fault generated component of illite formed at 50 8 ma and that the detrital component formed at 236 7 ma indicating a middle eocene age of faulting and a middle triassic age of the wall rocks comparing this dataset with published thermochronology from hanging wall rocks supports the interpretation that the west qinling fault initiated at 50 ma and continued until at least middle miocene time and that authigenic clay growth occurred at ambient temperatures of 110 c lack of overprinting of younger clay ages at this site may indicate that rocks were out of the thermal window for authigenic clay formation during later faulting episodes the potential for temperature to control illite growth has implications for interpretation of authigenic illite ages and their relationship to deformation episodes within fault zones

a thermal plume model for the convective boundary layer representation of cumulus clouds abstract the thermal plume model a mass flux scheme combined with a classical diffusive approach originally developed to represent turbulent transport in the dry convective boundary layer is extended here to the representation of cloud processes the modified parameterization is validated in a 1d configuration against results of large eddy simulations les as well as in a 3d configuration against in situ measurements for a series of cases of dry and cloudy convective boundary layers accounting for coherent structures of the mixed layer with the mass flux scheme improves the representation of the diurnal cycle of the boundary layer particularly its progressive deepening during the day and the associated near surface drying results also underline the role of the prescription of the mixing of air between the plume and its environment and of submean plume fluctuations

timing of brittle deformation within the nojima fault zone japan abstract k ar ages from clay fault gouges of outcrop and core samples ug500 well from the nojima fault zone awaji island japan are consistent internally with established field constraints and with apatite and zircon fission track ages demonstrating the suitability of this method for dating of brittle deformation six unspiked and thirty conventional k ar data of clay minerals separated from gouge zones were analysed characterized by protoliths of high grade metamorphic and magmatic rocks the samples from the nojima fault zone offer the opportunity to distinct identify newly grown illite in the fault planes all dated sample fractions were characterized by xrd sem and tem k ar ages of 29 separates have an age range from 63 4 1 3 ma early palaeocene danian to 42 2 1 0 palaeogene middle eocene lutetian some

cretaceous reactivation of the deokpori thrust taebaeksan basin south korea constrained by k ar dating of clayey fault gouge 1 the deokpori thrust juxtaposing the early paleozoic yeongwol type joseon supergroup yeongwol group against the duwibong type joseon supergroup taebaek group in the okcheon belt is an important regional structure in the phanerozoic tectonic evolution of korea although the initiation of the thrust has recently been conjectured to occur during the middle jurassic daebo tectonic event in a continental magmatic arc setting its movement history has never been studied we report timing of brittle reactivation of the thrust obtained from k ar dating of fault gouges in the core of the deokpori thrust zone k ar illite age data of fault gouges suggest reactivation of the thrust at ca 72 ma after a contact metamorphism around 94 ma our result is the first documentation of the reactivation of a major jurassic daebo structure and the reactivation may represent a significant contractional tectonic event during the late cretaceous in the korean peninsula

new constraints on megathrust slip stability under subduction zone p t conditions abstract to understand and model subduction zone seismogenesis data are needed on the frictional properties of meta pelitic subduction zone materials under in situ megathrust conditions here we report the results of rotary shear friction experiments on simulated illite quartz fault gouge at an effective normal stress of 170 mpa a pore fluid pressure of 100 mpa at 150 500 c and sliding velocities of 1 100 m s the results show three temperature dependent regimes characterized by velocity strengthening at 150 250 c velocity weakening at 250 400 c and velocity strengthening at 400 500 c the regimes are defined by a decrease in the rate and state friction rsf parameter a b at 150 300 c followed by an increase at 300 500 c these trends correlate with systematic changes in other rsf parameters as well as an increase in friction coefficient above 300 c we explain the effects of increasing temperature in terms of a transition from frictional granular flow 150 250 c through granular flow whereby dilatation is balanced by thermally activated compaction involving stress corrosion cracking scc of quartz clasts 250 400 c to non dilatant slip on the phyllosilicates with accommodation at quartz clasts by scc 400 500 c taking into account the effects of sliding velocity the observed velocity weakening regime broadly explains the extent of the seismogenic zone within subduction megathrusts