active methanogenesis and acetate utilization in powder river basin coals united states coal deposits of the powder river basin prb in wyoming united states contain significant reserves of natural gas proven to be of biogenic origin the timing of gas generation in this basin and many others is either unknown or questionable luca technologies evaluated the prospect that methanogenesis is ongoing in prb coals using a combined laboratory and field approach the anaerobic bioconversion of coal to methane in laboratory experiments was observed in multiple samples indicating that indigenous microorganisms can generate methane from prb coal acetate was found to be a quantitatively important intermediate in methane formation the detection of microbial metabolites including acetate in coalbed methane formation waters and the ability of prb methanogenic consortia to convert the detected metabolites to methane is also consistent with in situ methanogenesis field tests revealed in situ microbial acetate utilization and significant dilution dispersion and migration of injected water and solutes in the coal seam this is believed to be important for contacting significant coal surface area and important for the measurement of in situ microbial activities collectively this information indicates that methanogenesis is active in the coal seams evaluated in the prb and that all of the methane present in the coals need not be a remnant of past methanogenesis

relocation and assessment of seismicity in the iran region summary more than 2000 instrumentally recorded earthquakes occurring in the iran region during the period 1918 2004 have been relocated and reassessed with special attention to focal depth using an advanced technique for 1 d earthquake location a careful review of starting depths association of teleseismic depth phases and the effects of reading errors on these phases are made and when necessary waveforms have been examined to better constrain ehb focal depths uncertainties in ehb epicentres are on the order of 10 15 km in the iran region owing to the earth s lateral heterogeneity and uneven station distribution uncertainties of reviewed ehb focal depth estimates are on the order of 10 km as compared to about 4 km for long period p and sh body waveform inversions nevertheless these ehb depth estimates are sufficiently accurate to resolve robust differences in focal depth distribution throughout the iran region and within their errors show patterns that are in agreement with the smaller number of earthquakes whose depths have been confirmed by body wave modelling or local seismic networks the importance of this result is that future earthquakes with apparently anomalous depths can easily be identified and checked if necessary most earthquakes in the iranian continental lithosphere occur in the upper crust with the crustal shortening produced by continental collision accommodated entirely by thickening and distributed deformation in the zagros mountains nearly all earthquakes are confined to the upper crust depths 20 km and there is no evidence for a seismically active subducted slab dipping ne beneath central iran by contrast in southeastern iran where the arabian seafloor is being subducted beneath the makran coast low level earthquake activity occurs in the upper crust as well as to depths of at least 150 km within a northward dipping subducting slab near the oman line a region transitional between the zagros and the makran seismicity extends to depths of up to 30 45 km in the crust consistent with low angle thrusting of arabian basement beneath central iran in north central iran along the alborz mountain belt seismic activity occurs primarily in the upper crust but with some infrequent events in the lower crust particularly in the western part of the belt the talesh where the south caspian basin underthrusts nw iran earthquakes that occur in a band across the central caspian following the apscheron balkhan sill between azerbaijan and turkmenistan have depths in the range 30 100 km deepening northwards these are thought to be connected with either incipient or remnant northeast subduction of the south caspian basin basement beneath the east west trending apscheron balkhan sill curiously in this region of genuine mantle seismicity there is no evidence for earthquakes shallower than 30 km

the 2013 wyoming upper mantle earthquakes tomography and tectonic implications on 21 september 2013 two earthquakes m 4 8 and 3 0 focal depths 70 km occurred in the lithospheric mantle beneath central wyoming which provide a rare opportunity to investigate the lithosphere rheology and dynamics we determined a detailed 3 d p wave tomography in the source area of the wyoming earthquakes using a large number of high quality travel time data of local earthquakes and teleseismic events our results show that the 2013 wyoming earthquakes occurred in an isolated high velocity high v anomaly which extends down to a depth of 160 km we propose two possible scenarios about the cause of the 2013 wyoming earthquakes one is that the high v anomaly reflects a remnant of the subducted oceanic slab which fractured under long term negative buoyancy and heating by the infilling asthenosphere the other is removing of a dense mantle lithospheric root the present results shed new light on the rheology and seismotectonics of the continental lithosphere

grain size assisted thermal runaway as a nucleation mechanism for continental mantle earthquakes impact of complex rheologies abstract thermal runaway has been proposed as a potential mechanism to initiate intermediate depth earthquakes as well as lithospheric scale shear zones at depths of 50 300 km where brittle failure is inhibited due to the confining pressure microstructural analyses of mantle shear zones and pseudotachylites experimental results as well as numerical models suggest that grain size reduction plays a significant role in this process and facilitates the initiation of thermal runaway and thus also the nucleation of intermediate depth earthquakes as well as the formation of lithosphere scale shear zones here i investigate the impact of complex composite rheologies on grain size assisted thermal runaway using numerical models results indicate that diffusion creep dislocation accommodated grain boundary sliding as well as low temperature plasticity do have a significant impact on the deformation of mantle rocks under lithospheric conditions and that peak stresses as well as the timing of grain size assisted thermal runaway ductile deformation in the shear zone leads to weakening of the rock due to grain size reduction and shear heating due to this weakening the rheological contrasts between the shear zone and the surrounding rock are increased and the critical stress required to initiate thermal runaway is progressively decreased until the rock fails by self localizing thermal runaway however dislocation accommodated grain boundary sliding reduces the temperatures at which this process is feasible as it weakens the rock to such an extent that critical runaway stresses are never reached application of these numerical models to the 2013 wind river earthquake wyoming suggests that grain size assisted thermal runaway is a feasible mechanism for the nucleation of this earthquake

subsidence of the aru trough and the aru island irian java indonesia abstract the aru trough structurally on trend with the timor trough is located in the northwestern edge of the australian platform southwest of irian jaya and east of the imbricated sediment wedge of the strong gravity gradient of the banda arc the isostatic anomalies based on the airy heiskanen system show that this part of the region is in subsidence a crustal extension may be active in a zone east of the aru trough resulting in a graben formation the root of the aru island is being pulled downward to the east so that this island is likely to sink geological investigations in the aru island strengthen this phenomenon and show a subsidence rate of 1 cm yr this crustal extension indicates that there is a separation underway of a block of the australian continental crust from the australian platform

geological interpretation of gas content trends walloon subgroup eastern surat basin queensland australia abstract the middle jurassic walloon subgroup is a prolific low rank coal seam gas csg resource in the surat basin australia this study applied a regionally consistent stratigraphic framework model to open file gas desorption and coal property data from 69 cored csg wells to assess spatial trends in gas content and test the influence of large scale geological heterogeneity on present day gas distribution continued successful exploration and production and possible future microbial regeneration of the walloon csg resource require an improved understanding of the controls on gas content distribution across the core region of production in the eastern surat basin the walloon subgroup can be subdivided into upper juandah and lower taroom coal measures separated by a relatively coal barren and sandstone dominated unit tangalooma sandstone within these units lateral variation in coal character is high precluding a regionally agreed coal group or seam correlation while the total dataset shows a general increase in gas content dry ash free d a f with increasing depth as a function of hydrostatic pressure there is considerable scatter in the distribution within individual wells gas content follows one of three trends gas content either 1 increases 2 increases then decreases or 3 decreases with depth trend 2 parabolic wells predominate with the gas content maxima coinciding with the tangalooma sandstone regardless of depth as such gas content layering follows rather than cross cuts the stratigraphy in the majority of wells the change in gas content with depth between the different units and the wells was used to identify domains of different gas gradients which could relate to differing gas saturations and geological setting the well profiles and gas gradients were analysed against available open file coal quality data without strong correlation to rank or type parameters the majority of very high gas gradient values occur in coals within or above the tangalooma sandstone suggesting that it forms a regional scale barrier both to possible gas migration from underlying and higher rank coals and to meteoric and biogenic recharge from above increased ethane values in the upper taroom and tangalooma csg support this interpretation alternatively this distribution may be the result of alternating adsorption desorption cycles linked to burial and uplift the wells containing the highest mean gas gradients span a range of subtle rank and structural domains but generally occur in structural highs under topographic lows with hydrostatic head wells from smaller scale anticlines not associated with topographic surface lows mainly exhibit lower mean gas gradients the study significantly expands the number of published gas content trends and proposes several factors influencing their formation and geographical distribution the results form the basis for future targeted sampling to test for gas origins migration retention and biogenic recharge processes within the surat basin

microbial controls on the origin and evolution of coal seam gases and production waters of the walloon subgroup surat basin australia abstract the walloon subgroup coal seam gas csg play in the surat basin queensland is australia s pre eminent onshore gas field concerted multi disciplinary research is underway investigating the distribution origin and composition of waters and gases in this dominantly microbial csg reservoir to guide both continued production and potential microbially enhanced coal bed methane mecom applications however prior to the present research a detailed study of co produced waters and gases from across the surat basin was not available in the public domain this study tested whether co produced water compositional and stable isotopic data show relationships with production gas stable isotope compositions to elucidate further evidence for microbial co2 reduction and explore the down dip geochemical evolution of walloon coal bed waters and gases a total of 41 wells were sampled with 50 water and 25 gas samples spanning the 3 major production areas of the surat basin detailed isotopic and hydrochemical analysis of these samples revealed distinct spatial trends between the different production locales water compositions were distinct for each of the production regions reflecting the different lithologies of adjacent recharge zones differing fluid rock interactions likely different microbial consortia and the extent of methanogenesis on the western side of the basin near roma waters were the freshest with the lowest median values for alkalinity 861 mg l and cl 588 mg l and a 13cdic of 14 2 on the eastern side of the basin the kogan nose waters were the most saline with the highest median values for na 1955 mg l cl 2280 mg l and 13cdic 20 0 also in the east in the present gas fairway the undulla nose waters had the highest median alkalinity 1841 mg l and were found to have a na excess median 1050 mg l and a lower than expected median 13cdic 14 0 co mingled produced methane carbon isotope values 13c 57 0 to 44 5 from both the upper juandah and lower taroom coal measures plot within the mixed thermogenic microbial genetic field by contrast deuterium isotopic difference 2h h2o ch4 values and cross plots of 2h h2o and 18o h2o suggest that microbially mediated co2 reduction is the dominant methane generation process in situ at a given depth the undulla nose waters in the east are more depleted in 2h and 18o than elsewhere in the surat basin which may suggest these samples have been more heavily impacted by water rock microbial reactions 14c values from the 3 production regions 0 115 to 1 769 pmc age 32 400 to 50 000 years before present b p suggest that walloon coals likely recharged in the last 50 000 years limit of radiocarbon dating consistent with these dates 2h h2o and 18o h2o values for the surat basin 2h 32 to 56 18o 5 9 to 9 0 echo the stable isotopic composition of meteoric waters during the initial part of the last glacial period in southeast queensland based on a strong correlation between 2h ch4 and 2h h2o we suggest that methane was generated since the late pleistocene pca analysis showed a degree of positive correlation between total alkalinity and both the 13cdic median 14 2 and 13c ch4 median 52 1 vectors that is consistent with finite reservoir effects the results inform ongoing studies of gas distribution and origins and mecom potential in the surat basin and underpin a broader study examining aquifer interactions

upper mantle earthquakes beneath the arafura sea and south aru trough implications for continental rheology 1 the extent and controls of long term elastic strength and seismicity in the upper continental lithospheric mantle uclm are controversial topics in continental tectonics one key issue is the scarcity of uclm earthquakes even where the uclm is likely to be colder than 600 c the rarity of these earthquakes could be because the uclm generally relatively hydrous causing it to deform aseismically even when colder than 600 c unless it is deforming at exceptionally high strain rates alternatively the uclm could be relatively anhydrous and potentially seismogenic at temperatures below 600 c in which case the rarity of uclm earthquakes may be because areas where the uclm is colder than 600 c have such a thick seismogenic layer and such a cool mantle root that they deform exceptionally slowly the identification and study of uclm earthquakes allows us to distinguish between these possibilities here we show that two earthquakes occurred in the uclm beneath the epicontinental arafura sea both earthquakes occurred where the uclm is probably cooler than 600 c and one of these earthquakes lies 25 km below the moho in an region where there is no evidence of unusually high strain rates there at least it is probable that the uclm is relatively anhydrous and seismogenic at temperatures below 600 c we also find evidence that regions where the uclm is colder than 600 c also have a seismogenic lower crust this results in a single extremely strong layer comprising the entire crust and the uclm down to the 600 c isotherm

effective elastic thickness of the northern australian continental lithosphere subducting beneath the banda orogen indonesia inelastic failure at the start of continental subduction abstract pliocene recent continent island arc collision of the northern australian continental lithosphere across the banda orogen from roti to the kai plateau 121 137 e longitude has formed an underfilled foreland basin within the timor tanimbar aru trough continental collision on northern australian lithosphere is most advanced near central timor island in terms of shortening and absorbing the forearc basin savu basin within the accretionary prism australian continental lithosphere north of area around central timor island is believed to be detached from the oceanic lithosphere effective elastic thickness eet of the northern australian continental lithosphere from roti to the kai plateau are derived using an elastic half beam model modeled deflection is matched to the seafloor bathymetry and the marine complete 3d bouguer gravity anomalies the eet varies from 27 to 75 km across the northern australian continental lithosphere from roti to kai plateau when the thickness of the elastic half beam is kept constant the highest eet values lies near central timor from the shelf to beneath the banda orogen the eet of the northern australian continental lithosphere is reduced from 90 to 30 km when the thickness of the elastic half beam is allowed to vary down dip elastic half beam modeling approximates the banda orogen as a triangular load and hidden subsurface loads as end point loads wider triangular loads modeling the load contribution from banda orogen need higher values of eet such an observation highlights the role of high eet in thin skinned collisional tectonics by promoting the support of wider accretionary prisms by parts of foreland basins with higher eet variations in eet may result from inelastic yielding in the northern australian continental lithosphere oroclinal bending of the australian continental lithosphere in the east from tanimbar to the kai plateau may create additional yielding and further decrease the eet change in eet occurred at the start of continental subduction in the late miocene early pliocene boundary due to change in curvature of the northern australian lithosphere near the shelf slope both in map and cross sectional view evidence for the inelastic yielding of the northern australian continental lithosphere near the present day shelf slope at the continental subduction is found in 1 the maximum change of eet near shelf slope in laterally variable eet calculations and 2 in the almost cessation of normal faulting in late miocene early pliocene seen on seismic reflection data from northern australian continental shelf slope elastic half beam models across central timor do not require end point loads and may imply that there are no slab pull forces from the oceanic lithosphere that are acting on the leading edge of the subducted northern australian continental lithosphere

implications of diapir derived detritus and gypsic paleosols in lower triassic strata near the castle valley salt wall paradox basin utah gypsum bearing growth strata and sedimentary facies of the moenkopi formation on the crest and ne flank of the castle valley salt wall in the paradox basin record salt rise evaporite exposure and salt withdrawal subsidence during the early triassic detrital gypsum and dolomite clasts derived from the middle pennsylvanian paradox formation were deposited in strata within a few kilometers of the salt wall and indicate that salt rise rates roughly balanced sediment accumulation resulting in long term exposure of mobile evaporite deposition took place primarily in flood basin or inland sabkha settings that alternated between shallow subaqueous and subaerial conditions in a hyperarid climate matrix supported and clast supported conglomerates with gypsum fragments represent debris flow deposits and reworked debris flow deposits respectively interbedded with flood basin sandstone and siltstone during development of diapiric topography mudstone rich flood basin deposits with numerous stage i to iii gypsic paleosols capped by eolian gypsum sand sheets accumulated during waning salt withdrawal subsidence association of detrital gypsum eolian gypsum and gypsic paleosols suggests that the salt wall provided a common source for gypsum in the surrounding strata this study documents a previously unrecognized salt weld with associated growth strata containing diapir derived detritus and gypsic palesols that can be used to interpret halokinesis

seismicity and one dimensional velocity structure of the himalayan collision zone earthquakes in the crust and upper mantle 1 earthquakes beneath the himalayan collision zone occur at depths between near surface and around 100 km below sea level after relocating earthquakes with two one dimensional 1 d velocity models we found a clear bimodal depth distribution for earthquakes in the himalayas of eastern nepal and the southern tibetan plateau and evidence that some earthquakes originate at upper mantle depths seismicity in nepal shows an accumulation of earthquakes along the front of the himalayan arc with a seismic gap between longitudes 87 3 e and 87 7 e although upper crustal seismicity along the topographic front of the high himalaya is consistent with a region of high strain accumulation associated with convergence on the main himalayan thrust fault microearthquakes do not necessarily occur on this fault instead they concentrate in the hanging wall seismic activity in the sub himalaya and the terai plains is almost exclusively limited to the vicinity of the location of the magnitude 6 5 20 august 1988 udayapur earthquake with most of the earthquakes in the lower crust and the upper mantle clusters of earthquakes in the lesser and high himalayas and south tibet tethyan himalayas mark very well defined zones of seismicity at depths between 50 and 100 km confirming the presence of earthquakes in the upper mantle in the region of continental collision the occurrence of earthquakes at sub moho depths favors the idea that the continental upper mantle deforms by brittle processes

hydrogeochemical study in the main ethiopian rift new insights to the source and enrichment mechanism of fluoride the central main ethiopian rift suffers a severe water quality problem characterized by an anomalously high fluoride f content that causes an endemic fluorosis disease the current study conducted in the ziway shala lakes basin indicates that the f content exceeds the permissible limit for drinking prescribed by the world health organization who 1 5 mg l in many important wells up to 20 mg l with even more extreme f concentration in hot springs and alkaline lakes up to 97 and 384 mg l respectively the groundwater and surface water from the highlands typically characterized by low total dissolved solids tds and ca mg hco3 hydrochemical facies do not show high f content the subsequent interaction of these waters with the various rocks of the rift valley induces a general increase of the tds and a variation of the chemical signature towards na hco3 compositions with a parallel enrichment of f the interacting matrixes are mainly rhyolites consisting of volcanic glass and only rare f bearing accessory minerals such as alkali amphibole comparing the abundance and the composition of the glassy groundmass with other mineral phases it appears that the former stores most of the total f budget this glassy material is extremely reactive and its weathering products i e fluvio volcano lacustrine sediments further concentrate the fluoride the interaction of these weathered reworked volcanic products with water and carbon dioxide at high ph causes the release of fluoride into the interacting water this mainly occurs by a process of base exchange softening with the neo formed clay minerals i e ca mg uptake by the aquifer matrix with release of na into the groundwater this is plausibly the main enrichment mechanism that explains the high f content of the local groundwater as evidenced by positive correlation between f ph and na and inverse correlation between f and ca mg saturation indices si have been calculated using phreeqc 2 for the different water groups highlighting that the studied waters are undersaturated in fluorite in these conditions fluoride cannot precipitate as caf2 and so mobilizes freely without forming other complexes these results have important implications for the development of new exploitation strategies and accurate planning of new drilling sites

the influence of dynamically supported topography on estimates of te abstract the effective elastic thickness t e of continental lithosphere can be estimated from the relationship between gravity and topography in the spectral domain two methods have been used one of which depends on the coherence between bouguer gravity anomalies and topography whereas the other uses the transfer function commonly known as the admittance between the free air gravity and topography the two methods give estimates of t e which differ by as much as an order of magnitude in those continental regions where variations in elevation are small this problem has led to much controversy an important concern is the extent to which estimates of t e are affected by dynamically maintained gravity and topography arising from mantle convection and postglacial recovery unlike elastically supported anomalies these processes can generate gravity and topographic long wavelength 500 km anomalies if such anomalies are modelled as being supported by elastic forces the resulting values of t e are overestimated often by a large amount

geochemistry of rare earth elements in a neutral mine drainage environment anjir tangeh northern iran abstract this study investigates the geochemical characteristics of rare earth elements and yttrium ree y in the neutral mine drainage nmd and river water in the vicinity of the anjir tangeh coal washing plant mazandaran province northern iran the nmd water had a neutral ph along with high sulphate and bicarbonate concentrations the total concentrations of ree in the nmd water were lower than in the river water according to the north american shale composite nasc normalised concentrations the patterns of nmd showed heavy ree hree enrichment while the river water represented middle ree mree enhancement both negative europium eu and positive gadolinium gd anomalies were observed in the drainage and river water within the study area the sum of ree concentration increased gradually downstream of the discharging point of the plant reject water in contrast to decreasing of al fe mn and cu pb zn concentrations the river sediment with high fe concentrations was enriched with lanthanum la and cerium ce the overall ree pattern of the nmd approximates those of coal except for the depletion in light ree lree and the enrichment of eu dominant inorganic ree species in the river water included ln co3 2 and lnco3 while lnco3 ln co3 2 and ln so4 were the main complexes in the nmd the saturation index indicated that al and fe were both oversaturated in the drainage and river water which can control the fractionation of ree by the sorption process according to both hierarchical cluster analysis hca and principal component analysis pca ph al and p were the significant parameters in the ree distribution

seismic evidence for a moderately thick lithosphere beneath the siberian platform 1 we have built a sv wavespeed tomographic model for the upper mantle beneath the siberian platform and surrounding region derived from the analysis of more than 13 000 fundamental and higher mode regional waveforms the dense path coverage and rich higher mode content of the data allow building an upper mantle image with an horizontal resolution of a few hundred kilometers extending to 400 km depth the high velocity upper mantle lid or seismic lithosphere is 200 km thick beneath most of the siberian platform but may extend to 250 km depth beneath small areas a high velocity seismic lid also underlies a large region west of the siberian platform our observation of a 200 thick seismic lithosphere beneath the siberian platform on the slow moving eurasian plate similar to the thickness of the seismic lithosphere beneath precambrian terrains on the fast moving australian plate suggests that a moderately thick seismic lithosphere beneath precambrian terrains may be more common than previously supposed

application of multivariate statistical methods and inverse geochemical modeling for characterization of groundwater a case study ain azel plain algeria abstract multivariate statistical methods and inverse geochemical modeling were jointly used to define the variation and the genetic origin of chemical parameters of groundwater in the ain azel plain algeria interpretation of analytical data shows that the abundance of the major ions is as follows ca mg na k and hco 3 cl so 4 q mode hierarchical cluster analysis hca was employed for partitioning the water samples into hydrochemical facies also known as water groups or water types three major water groups resulted from the hca analysis the samples from the area were classified as recharge area waters group 1 ca mg hco 3 water transition zone waters group 2 ca mg cl hco 3 water and discharge area waters group 3 mg ca hco 3 cl water inverse geochemical models of the statistical groups were developed using phreeqc to elucidate the chemical reactions controlling water chemistry the inverse geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area in a broad sense the reactions responsible for the hydrochemical evolution in the area fall into three categories 1 dissolution of evaporite minerals 2 precipitation of carbonate minerals and 3 weathering reactions of silicate minerals

hydrogeochemistry of sodium bicarbonate type bedrock groundwater in the pocheon spa area south korea water rock interaction and hydrologic mixing the pocheon spa land area south korea occurs in a topographically steep fault bounded basin and is characterized by a hydraulic upwelling flow zone of thermal water up to 44 c in its central part hydrogeochemical and environmental isotope data for groundwater in the study area suggested the occurrence of two distinct water types a ca hco3 type and a na hco3 type the former water type is characterized by relatively high concentrations of ca so4 and no3 which show significant temporal variation indicating a strong influence by surface processes in contrast the na hco3 type waters have high and temporally constant temperature ph tds na cl hco3 and f indicating the attainment of a chemical steady state with respect to the host rocks granite and gneiss oxygen hydrogen and tritium isotope data also indicate the differences in hydrologic conditions between the two groups the relatively lower 18o d and tritium values for na hco3 type waters suggest that they recharged at higher elevations and have comparatively long mean residence times considering the geologic and hydrogeologic conditions of the study area na hco3 type waters possibly have evolved from ca hco3 type waters mass balance modeling revealed that the chemistry of na hco3 type water was regulated by dissolution of silicates and carbonates and concurrent ion exchange particularly low ca concentrations in na hco3 water was mainly caused by cation exchange multivariate mixing and mass balance modeling m3 modeling was performed to evaluate the hydrologic mixing and mass transfer between discrete water masses occurring in the shallow peripheral part of the central spa land area where hydraulic upwelling occurs based on q mode factor analysis and mixing modeling using phreeqc an ideal mixing among three major water masses surface water shallow groundwater of ca hco3 type deep groundwater of na hco3 type was proposed m3 modeling suggests that all the groundwaters in the spa area can be described as mixtures of these end members after mixing the net mole transfer by geochemical reaction was less than that without mixing therefore it is likely that in the hydraulic mixing zone geochemical reactions are of minor importance and therefore that mixing regulates the groundwater geochemistry

clay mineral authigenesis in coal and shale from the anthracite region pennsylvania textural chemical and mineralogical analyses of authigenic clays in anthracite rank coal and associated shale from eastern pennsylvania have allowed a better understanding of the parameters controlling diagenesis and perhaps coalification in this region minerals in anthracite occur in distinct assemblages associated with the following microenvironments coal matrix two orthogonal joint sets termed systematic and nonsystematic cleat and a third joint set mineralogical differences among microenvironments allow inferences about clay mineral origins and the parameters that controlled mineral authigenesis kaolinite occurs in the shale and all microenvironments within the coal seam authigenic minerals that replaced preexisting kaolinite during the latest stage ofcoalification anthracitization at t 200 c include nhu rich illite pyrophyllite and the following minerals which are primarily restricted to the systematic cleat set tosudite rl ordered dioctahedral mixed layer chlorite smectite sudoite di trioctahedral chlorite and rectorite rlordered mixedjayer paragonite smectite alteration of smectite to illite may be responsible for formation of authigenic illite and na bearing illite which are present only in the shale and coal matrix and fe al rich chlorite and quartz in the third joint set the chemical components for authigenesis appear to have multiple sources ai and si from preexisting kaolinite and quartz n from local organic matter mg and na for tosudite sudoite and rectorite largely from metasomatic hydrothermal fluids fe and mg for fe al rich chlorite from smectite illitization minerals in the shale the coal matrix and the nonsystematic cleat set are interpreted to represent authigenesis in a low permeability environment closed system alteration however the assemblage sudoite tosudite rectorite in the systematic cleat set is interpreted to be the result ofone or two stages ofhydrothermal alteration open system alteration we suggest hat differences in minerals between the two nearly perpendicular cleat sets are the result of permeability differences which were maintained by an anisotropic lateral stress field created by plate convergence during the alleghanian orogeny hydrothermal alteration may be related to large scale basinal flow induced by alleghanianage uplift such migrating fluids could also have transported heat from depth and thereby significantly increased the rate and rank ofcoalification in this region

new seismic model of the upper mantle beneath africa we present a seismic model of the upper 400 km of the mantle beneath africa and surrounding regions this model is constructed by inverse modeling of fundamental mode rayleigh wave phase velocities 40 200 s for about 8000 propagation paths among the most pronounced anomalies are high shear velocity structures as much as 6 higher than in the preliminary reference earth model beneath the west african congo and kalahari cratons that extend to about 250 km depth these structures have near vertical margins across which the shear velocity changes by as much as 6 over 500 km distance anomalous low shear velocities 3 4 lower than in the preliminary reference earth model structures are observed beneath the east african red sea and gulf of aden rifts and beneath the northwestern indian ocean these structures extend to a depth of at least 250 km our model cannot be reconciled with models that invoke a large number of plumes that have impinged on the base of the lithosphere nor does our seismic model indicate that high temperature low density material beneath the lithosphere is responsible for the uplift of southern africa

microbial precipitation of dolomite in methanogenic groundwater we report low temperature microbial precipitation of dolomite in dilute natural waters from both field and laboratory experiments in a freshwater aquifer microorganisms colonize basalt and nucleate nonstoichiometric dolomite on cell walls in the laboratory ordered dolomite formed at near equilibrium conditions from groundwater with molar mg ca ratios of 1 dolomite was absent in sterile experiments geochemical and microbiological data suggest that methanogens are the dominant metabolic guild in this system and are integral to dolomite precipitation we hypothesize that the attached microbial consortium reacts with the basalt surface releasing mg and ca into solution which drives dolomite precipitation via nucleation on the cell wall these findings provide insight into the long standing dolomite problem and suggest a fundamental role for microbial processes in the formation of dolomite across a wide range of environmental conditions

coal petrology and coal seam gas contents of the walloon subgroup surat basin queensland australia abstract core exploration and appraisal drilling over the last four years have targeted the juandah upper and taroom lower coal measures of the middle jurassic walloon subgroup of the injune creek group these wells have shown that the high volatile bituminous perhydrous coals of the walloon subgroup have gas contents of between 1 and 14 m 3 t and some wells have encountered gas flows at rates of over 30 000 m 3 day this recent work has confirmed the initial supposition that the coals within the walloon subgroup contain sufficient quantities of gas to be economically viable as a coal seam gas source coal volumes depth and structure have also been confirmed from the initial work what has become apparent during this work is the variability in gas content across each of the seams in the juandah and taroom coal measures and the variability in coal petrographic composition of these two units are controlled by many factors what has also become apparent is that the taroom coal measures have a lower average gas content than the overlying juandah coal measures the obvious conclusion is that the difference in gas content is related to a difference in coal petrology not only do the gas contents of these coal intervals differ their gas adsorption capacities also differ with the taroom coal measures coals displaying on average lower gas content and lower gas adsorption capabilities again the obvious cause would be coal petrological differences but the juandah and taroom coal measures coals have similar maceral percentages an understanding of the relationship between gas desorption gas adsorption and coal composition is vital in determining which areas in the basin offers the most economically viable targets for the commercialisation of coal seam gas in the surat basin

new views on the structure and rheology of the lithosphere over the last 10 years a series of developments have led to a new understanding of what controls the variations in lithosphere strength structure and evolution that produce dramatic contrasts between the geological histories of oceans ancient shields and young orogenic belts those developments involve a wide range of observations from a great diversity of geological geophysical and geochemical disciplines that none the less provide a mutually consistent and coherent overall picture this paper summarizes in one place the essential stages in the evolution of the relevant ideas and observations that have led to this situation

study of hydrochemical characteristics of cbm co produced water of the shizhuangnan block in the southern qinshui basin china on its implication of cbm development abstract coalbed methane cbm co produced water is primarily coal seam water it may be mixed with fracturing fluids especially during the early drainage stage or with other aquifer water if the coal seam is connected with an aquifer via artificial or natural fractures faults if the impacts of fracturing fluids and other aquifer water can be removed the chemical characteristics of cbm co produced water can act as effective indicators for cbm exploration and development based on the water chemistry analyses of 119 samples collected from 47 cbm wells over four years quarterly sampling in the shizhuangnan block qinshui basin the dynamic characteristics of the cbm co produced water chemistry that were influenced by fracturing fluids were studied in this study relationships between the major cbm co produced water ions were determined and the relationship between the cbm co produced water ions and gas production were investigated the results suggest that the cbm co produced water chemical signature of the shizhuangnan block is similar to that of other coal seam waters from around the world being characterized by the sodium chloride bicarbonate water types that are depleted in calcium and magnesium ions and exhibit highly lowered sulfate concentrations due to the mixing with the fracturing fluids and coal seam water the tds sodium chloride and calcium and magnesium ion concentrations decrease during the early drainage stage following a power law function however bicarbonate and sulfate concentrations do not significantly vary the na and cl na cl and alkalinity cl and na cl and na alkalinity ratios exhibit a positive linear relationship strong positive linear relationship and exponentially decaying relationship respectively additionally 10 meq l of cl may serve as a dividing line for the presence or absence of the fracturing fluid affect na and cl may release organic bound chlorine complexes from the coal during coal metamorphism the tds and bicarbonate concentration of the cbm co produced water produced by the gas production wells are all 1000 mg l and 8 meq l respectively the bicarbonate concentration is influenced by both the lch which is the height of the liquid level compared to the coal bed surface at the onset of water production at a cbm well and hydraulic conductivity fault and its distribution controls the distribution of the high gas yield wells

a reassessment of spectral te estimation in continental interiors the case of north america 1 conventional spectral te studies use the real part of the admittance between gravity anomalies and topography or alternatively the square of the magnitude of the coherency i e coherence here we show the utility of treating both the admittance and coherency as complex quantities inverting the real parts to estimate te we use the imaginary parts to tell if the inversion is biased by noise one method inverts the square of the real coherency with the internal to total load ratio f derived as a function of wave number directly from the gravity and topography the other method inverts the real part of the admittance assuming that f is wave number independent we test the methods using synthetic elastic plate models loaded at the surface and moho in such a way that the final relief is the actual north american topography in some of the models we add gravity noise generated by a model having both surface and internal loads such that the final topography is zero and find that both methods are susceptible to noise application of the two methods to north america gives te maps showing substantial agreement except in regions affected by noise but these are not a dominant part of the total area given the suggested mechanisms by which noise might arise it is not surprising that it is not a more widespread feature of the north american craton importantly both methods show that large parts of the canadian shield are characterized by te 100 km

stable isotopic and molecular composition of desorbed coal seam gases from the walloon subgroup eastern surat basin australia this study used compositional and stable isotopic analysis to test hypotheses on the distribution and origins of walloon subgroup coal seam gas csg in the eastern surat basin queensland australia the middle jurassic walloon subgroup play differs from many other low rank csg plays particularly in methane carbon isotopic signature i e the csg is not as microbial as could be expected the carbon isotope compositions of desorbed methane from three cored appraisal wells fall within the generally accepted range for thermogenic or mixed gas 13c 58 5 to 45 3 the 13c ch4 values from stratigraphically placed coal core samples increased became more thermogenic from the top of the upper juandah coal measures to the base of the tangalooma sandstone below the tangalooma sandstone in the lower taroom coal measures the 13c ch4 values decreased with increasing depth these positively parabolic 13c profiles tracked total measured gas content in two out of the three wells studied the third well displayed lower variance of 13c ch4 and gas content increased uniformly with depth a genetic classification based on methane stable carbon isotopes alone might interpret this pattern as a transition from microbially to thermogenically sourced methane in the central coal seams however a 13c co2 profile for one well tracks total gas content and 13c ch4 and exhibits an inverse relationship with d ch4 these results together with the mostly dry nature of the gas samples c1 c2 c3 ratios up to 10 000 and relatively uniform d ch4 values d 238 to 202 suggest that microbial co2 reduction is the primary source of walloon subgroup methane as such stratigraphic variations in gas content mainly reflect the extent of microbial methanogenesis we suggest that peak microbial utilisation of h2 co2 occurred at the tangalooma sandstone level enriching the residual co2 pool and derived methane in 13c carbon 13c co2 ch4 and deuterium isotopic differences d h2o ch4 and cross plots of d h2o and 18o h2o are also consistent with kinetic isotope fractionation during microbial mediated carbonate reduction the results are relevant for applying microbially enhanced coal bed methane mecom in the surat basin

hydrogeologic factors affecting gas content distribution in coal beds gas content in coal is not fixed but changes when equilibrium conditions within the reservoir are disrupted therefore gas content distribution in coal varies laterally within individual coal beds vertically among coal beds in a single well and within thicker coal beds major hydrogeologic factors affecting gas content variability include gas generation coal properties and reservoir conditions gas generation affects gas content variability on a regional scale whereas coal properties influence gas content distribution on a regional and local scale reservoir conditions affect gas content more locally within specific fields or individual wells the potential for high gas content is controlled directly by the amount of thermogenic and secondary biogenic gases generated from the coal which in turn are controlled by burial history maceral composition and basin hydrodynamics variability in mineral matter ash and moisture content sorption behavior among macerals diffusion coefficients and permeability result in heterogeneous gas content distribution gas content decreases with decreasing pressure and temperature and coal beds become undersaturated with respect to methane during basin uplift and cooling gas content generally increases where conventional and hydrodynamic trapping of coal gases occur and may decrease in areas of active recharge with downward flow potential and or convergent flow where there is no mechanism for entrapment

geology of the kai islands implications for the evolution of the aru trough and weber basin banda arc indonesia abstract the kai archipelago is situated at the apex of the 180 bend in the banda island arc topographically the islands occupy a forearc position between the aru trough to the east and the weber forearc basin to the west however the structural style of the eastern kai islands is very different from the rest of the banda forearc being dominated by normal faults downthrowing to the aru trough with no sign of earlier compressive forearc deformation the aru trough is an extensional feature although it is in direct bathymetric continuity with the compressional timor tanimbar trough to the south the banda arc thrust front does not continue simply northward from the timor tanimbar trough but steps westward as a result of extension in the aru trough the thrust front runs n s through the kai group separating an inactive accretionary complex to the west from active extension in the east the weber basin results from e w extension with pre existing thrust faults probably reactivated in extension as low angle normal faults both the compressional and extensional deformation phases have occurred since the pliocene a period of less than 5 my

earthquake depth distributions in central asia and their relations with lithosphere thickness shortening and extension this paper examines the relationship between seismogenic thickness lithosphere structure and rheology in central and northeastern asia we accurately determine earthquake depth distributions which reveal important rheological variations in the lower crust these variations exert a fundamental control on the active tectonics and the morphological evolution of the continents we consider 323 earthquakes across the tibetan plateau the tien shan and their forelands as well as the baikal rift ne siberia and the laptev sea and present the source parameters of 94 of these here for the first time these parameters have been determined through body wave inversion the identification of depth phases or the modelling of regional waveforms lower crustal earthquakes are found to be restricted to the forelands in areas undergoing shortening and to locations where rifting coincides with abrupt changes in lithosphere thickness such as the ne baikal rift and w laptev sea the lower crust in these areas is seismogenic at temperatures that may be as high as 600 c suggesting that it is anhydrous and is likely to have great long term strength lower crustal earthquakes are therefore a useful proxy indicating strong lithosphere in places that are too small in areal extent for this to be confirmed independently by estimating effective elastic thickness from gravity topography relations the variation in crustal rheology indicated by the distribution of lower crustal earthquakes has many implications ranging from the support of mountain belts and the formation of steep mountain fronts to the localization and orientation of rifting in combination these processes can also be responsible for the separation of the front of the thin skinned mountain belts from their hinterlands when continents separate

multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system summary the study of groundwater hydrogeochemistry of the paleozoic basses laurentides sedimentary rock aquifer system in quebec produced a large geochemical dataset groundwater samples were collected at 153 sites over a 1500 km2 study area and analyzed for major and minor ions the large number of data can lead to difficulties in the integration interpretation and representation of the results two multivariate statistical methods hierarchical cluster analysis hca and principal components analysis pca were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry this subgroup consisted of 144 samples and 14 parameters ca2 mg2 na k hco 3 cl so 4 2 fe2 mn2 br sr2 f ba2 hs seven geochemically distinct clusters c1 c7 resulted from the hca samples from clusters c3 c4 c6 and c7 are mostly located in preferential recharge areas the majority of these samples have ca mg hco3 recharge groundwater c3 c6 c7 and na hco3 evolved groundwater c4 samples from the other three clusters c1 c2 c5 are characteristic of an aquifer system under confined conditions the majority of these samples have na hco3 evolved groundwater c1 c5 and na cl ancient groundwater that exhibits elevated concentrations in br c2 in addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry the distribution of clusters also showed the importance of the geological formations on minor and trace elements such as fe2 mn2 sr2 f and ba2 the first five components of the pca account for 78 3 of the total variance in the dataset component 1 is defined by highly positive loadings in na cl and br and is related to groundwater mixing with champlain sea water and solute diffusion from the marine clay aquitard the high positive loadings in ca2 and mg2 of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system from their characteristic loadings the first two components are defined as the salinity and hardness components respectively components 3 5 are related to more local and geological effects the integration of the hca and the pca with conventional classification of groundwater types as well as with the hydrogeological and geological contexts allowed the division of the region into four main geochemical areas providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater the following factors were recognized as influencing the evolution of groundwater identified in every geochemical area 1 geological characteristics including sedimentary rock type and till mineralogy 2 hydrogeological characteristics represented by the level of confinement and the hydraulic gradient and 3 the geological history including the latest glaciation and the champlain sea invasion with its integrated approach this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems and provides an example of the long term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion

geochemical signature of formation waters associated with coalbed methane formation waters associated with coalbed methane have a common chemical character that can be an exploration tool regardless of formation lithology or age effectively devoid of sulfate calcium and magnesium the waters contain primarily sodium and bicarbonate and where influenced by water of marine association also contain chloride the distinct geochemical signature evolves through the processes of biochemical reduction of sulfate enrichment of bicarbonate and precipitation of calcium and magnesium cation exchange with clays may also deplete the dissolved calcium and magnesium but is not prerequisite low sulfate bicarbonate ratios characterize these waters and are also common but less pronounced with occurrences of conventional oil and gas waters rich in sulfate calcium and magnesium occur in many coalbed aquifers but are not found in association with methane users of total dissolved solids data should ensure that the values reflect adjustments of bicarbonate concentrations to simulate evaporation residues results that erroneously sum the entire bicarbonate content can be far too high in these bicarbonate rich waters thereby exacerbating the issues of disposal evaluations of prospects and choices of exploration targets can be enhanced by an added focus on the geochemical signature that should be expected in association with methane knowledge of the geochemical signature may also be useful in the commonly protracted testing of wells the appearance of high sulfate concentrations in water analyses can justify early curtailment of test pumping and can prompt the siting of subsequent drill holes farther from areas of recharge

the long wavelength admittance and effective elastic thickness of the canadian shield the strength of the cratonic lithosphere has been controversial on the one hand many estimates of effective elastic thickness te greatly exceed the crustal thickness but on the other the great majority of cratonic earthquakes occur in the upper crust this implies that the seismogenic thickness of cratons is much smaller than te whereas in the ocean basins they are approximately the same leading to suspicions about the large te estimates one region where such estimates have been questioned is the canadian shield where glacial isostatic adjustment gia and mantle convection are thought to contribute to the long wavelength undulations of the topography and gravity to date these have not been included in models used to estimate te from topography and gravity which conventionally are based only on loading and flexure here we devise a theoretical expression for the free air gravity topography admittance that includes the effects of gia and convection as well as flexure and use it to estimate te over the canadian shield we use wavelet transforms for estimating the observed admittances after showing that multitaper estimates which have hitherto been popular for te studies have poor resolution at the long wavelengths where gia and convection predominate compared to wavelets our results suggest that te over most of the shield exceeds 80 km with a higher te core near the southwest shore of hudson bay this means that the lack of mantle earthquakes in this craton is simply due to its high strength compared to the applied stresses

earthquake distribution patterns in africa their relationship to variations in lithospheric and geological structure and their rheological implications we use teleseismic waveform inversion along with depth phase analysis to constrain the centroid depths and source parameters of large african earthquakes the majority of seismic activity is concentrated along the east african rift system with additional active regions along stretches of the continental margins in north and east africa and in the congo basin we examine variations in the seismogenic thickness across africa based on a total of 227 well determined earthquake depths 112 of which are new to this study seismogenic thickness varies in correspondence with lithospheric thickness as determined from surface wave tomography with regions of thick lithosphere being associated with seismogenic thicknesses of up to 40 km in regions of thin lithosphere the seismogenic thickness is typically limited to 20 km larger seismogenic thicknesses also correlate with regions that have dominant tectonothermal ages of 1500 ma where the east african rift passes around the archean cratons of africa through the older proterozoic mobile belts these correlations are likely to be related to the production affected by method and age of basement formation and preservation affected by lithospheric thickness of a strong anhydrous lower crust the congo basin contains the only compressional earthquakes in the continental interior simple modelling of the forces induced by convective support of the african plate based on long wavelength free air gravity anomalies indicates that epeirogenic effects are sufficient to account for the localization and occurrence of both extensional and compressional deformation in africa seismicity along the margins of africa reflects a mixture between oceanic and continental seismogenic characteristics with earthquakes in places extending to 40 km depth

relationships between major ions in coal seam gas groundwaters examples from the surat and clarence moreton basins abstract using a combination of multivariate statistical techniques and the graphical assessment of major ion ratios the influences on hydrochemical variability of coal seam gas or coal bed methane groundwaters from several sites in the surat and clarence moreton basins in queensland australia were investigated several characteristic relationships between major ions were observed 1 strong positive linear correlation between the na cl and alkalinity cl ratios 2 an exponentially decaying trend between the na cl and na alkalinity ratios 3 inverse linear relationships between increasing chloride concentrations and decreasing ph for high salinity groundwaters and 4 high residual alkalinity for lower salinity waters and an inverse relationship between decreasing residual alkalinity and increasing chloride concentrations for more saline waters the interpretation of the hydrochemical data provides invaluable insights into the hydrochemical evolution of coal seam gas csg groundwaters that considers both the source of major ions in coals and the influence of microbial activity elevated chloride and sodium concentrations in more saline groundwaters appear to be influenced by organic bound chlorine held in the coal matrix a sodium and chloride ion source that has largely been neglected in previous csg groundwater studies however contrastingly high concentrations of bicarbonate in low salinity waters could not be explained and are possibly associated with a number of different factors such as coal degradation methanogenic processes the evolution of high bicarbonate nahco 3 water types earlier on in the evolutionary pathway and variability in gas reservoir characteristics using recently published data for csg groundwaters in different basins the characteristic major ion relationships identified for new data presented in this study were also observed in other csg groundwaters from australia as well as for those in the illinois basin in the usa this observation suggests that where coal maceral content and the dominant methanogenic pathway are similar and where organic bound chlorine is relatively abundant distinct hydrochemical responses may be observed comparisons with published data of other nahco 3 water types in non csg environments suggest that these characteristic major ion relationships described here can i serve as an indicator of potential csg groundwaters in certain coal bearing aquifers that contain methane and ii help in the development of strategic sampling programmes for csg exploration and to monitor potential impacts of csg activities on groundwater resources

characterization of the origin of coalbed gases in southeastern illinois basin by compound specific carbon and hydrogen stable isotope ratios abstract coalbed gases and waters from exploratory and production gas wells in the southeastern illinois basin were sampled to assess geochemically the origin of coalbed gases with an emphasis on the springfield and seelyville coal members that are commercially targeted for coalbed methane production in indiana on line analyses of hydrocarbon gases methane to butanes c 1 c 2 c 3 n c 4 i c 4 and co 2 yielded gas concentrations plus d and 13 c values the low thermal maturity of indiana coals with vitrinite reflectance r 0 0 6 is in agreement with an overwhelmingly biogenic isotopic signature of coalbed gases containing 96 methane generated via bacterial co 2 reduction in contrast thermogenic gas was generated in the stratigraphically equivalent coal beds in western kentucky s rough creek graben zone where higher maturities of up to r 0 0 8 were reached owing to tectonic and hydrothermal activity no secondary biogenic methane was observed in more mature western kentucky coal beds where greater burial depth limits the recharge of meteoric water biogenic and thermogenic coalbed gases represent two end members that are compositionally and isotopically distinct microbial biodegradation of thermogenic c 2 hydrocarbon gases in indiana coal beds preferentially targets c 3 and introduces isotope fractionation whereby remaining c 3 is enriched in deuterium and 13 c

bacterial production of methane and its influence on ground water chemistry in east central texas aquifers geochemical and isotopic data for methane and ground water indicate that gaseous hydrocarbons in eocene aquifers in east central texas form by bacterial processes the 13c values of methane from five wells in the clay rich yegua and cook mountain formations range from 71 to 62 methane from ten wells in the cleaner sands of the sparta and queen city formations have 13c values between 57 and 53 the carbon isotopic difference between methanes from the yegua and sparta aquifers is comparable to the isotopic difference in sedimentary organic matter from outcrops of the units suggesting substrate control on the 13c of bacterial methane hydrogen isotopic compositions of methane from the aquifers are similar averaging 181 this high value suggests methane production predominantly by co2 reduction the 13c of dissolved inorganic carbon dic in high bicarbonate waters increases from about 20 to 0 with increasing dic mass balance calculations indicate that the dic added to the ground water has 13c values as high as 10 this 13c enriched carbon is predominantly derived from co2 production by fermentation and anaerobic oxidation reactions combined with co2 consumption by co2 reduction this process is responsible for high bicarbonate contents in these and probably other gulf coast ground waters

apparently deep events in the middle atlas resolved to be shallow implications for lithospheric deformation abstract the occurrence of intermediate depth seismicity in intracontinental settings is rare but it has been postulated with various degrees of certainty in several regions one such region is the middle atlas of morocco since 1960 75 intermediate depth earthquakes have been reported in this region by spain s national geographic institute ign the apparent deep nature of these events is hard to reconcile with well established geophysical evidence of a thin lithosphere under the middle atlas but has been associated with mantle delamination processes we relocate 4 events with ign reported depths 80 km that were recorded by a relatively dense temporary deployment using a recent regional 3d velocity model obtained through teleseismic body and surface wave tomography the relocation procedure uses a grid search approach to minimize the mean normalized misfit where each travel time misfit is normalized by the estimated pick uncertainty we find that our observed arrivals are much better fit by shallow 80 km we propose that these shallow foci earthquakes are the result of regional crustal deformation of this region caused by the present convergence between africa and eurasian plate we infer that if there are any ongoing delamination processes in the area they are aseismic this study is an example of how local earthquake locations in tectonically complex areas can be significantly improved by using a dense local seismic array and a well constrained 3 d velocity model

mineral matter and trace elements in coals of the gunnedah basin new south wales australia abstract the concentrations of major and trace inorganic elements in a succession of permian coals from the gunnedah basin new south wales have been determined by x ray fluorescence techniques applied to both whole coal and high temperature ash samples the results have been evaluated in the light of quantitative data on the minerals in the same coals determined from x ray diffraction study of whole coal samples using a rietveld based interpretation program siroquant to determine relationships of the trace elements in the coals to the mineral species present comparison of the chemical composition of the coal ash interpreted from the quantitative mineralogical study to the actual ash composition determined by xrf analysis shows a high degree of consistency confirming the validity of the xrd interpretations for the gunnedah basin materials quartz illite and other minerals of detrital origin dominate the coals in the upper part of the sequence whereas authigenic kaolinite is abundant in coals from the lower part of the permian succession these minerals are all reduced in abundance however and pyrite is a dominant constituent in coals formed under marine influence at several stratigraphic levels calcite and dolomite occur as cleat and fracture infillings mostly in seams near the top and bottom of the sequence the potassium bearing minerals in the detrital fraction are associated with significant concentrations of rubidium and the authigenic kaolinite with relatively high proportions of titanium zirconium is also abundant with associated p and hf in the gunnedah basin coal seams relationships exhibited by ti zr nd and y are consistent with derivation of the original sediment admixed with the seams from an acid volcanic source pyrite in the coals is associated with high concentrations of arsenic and minor proportions of thallium no other element commonly associated with sulphides in coals however appears to occur in significant proportions with the pyrite in the sample suite small concentrations of cl present in the coal are inversely related to the pyrite content and appear to represent ion exchange components associated with the organic matter strontium and barium are strongly associated with the cleat filling carbonate minerals ge and ga appear to be related to each other and to the coal s organic matter cr and v are also related to each other as are ce la nd and pr but none of these show any relationship to the organic matter or a particular mineral component

upper mantle s wave speed heterogeneity and anisotropy beneath the north atlantic from regional surface wave tomography the iceland and azores plumes summary we present a high resolution sv wave velocity and azimuthal anisotropy model for the upper mantle beneath the north atlantic and surrounding region derived from the analysis of over 3000 fundamental and higher mode rayleigh waveforms much of the data set comes from global and national digital seismic networks but to improve the path coverage we have also deployed a number of instruments at coastal sites in northwest europe iceland and eastern greenland the dense path coverage wide azimuthal distribution substantial higher mode content and the relatively short path lengths in the data set have enabled us to build an upper mantle model for the region with a horizontal resolution of a few hundred kilometres extending to 400 km depth three major hotspots iceland azores and eifel exist within the region of the model and slow upper mantle velocities are associated with each of these areas the best depth resolution in our model occurs in nw europe and in this area low sv velocities in the vicinity of the eifel hotspot extend to approximately 400 km depth major negative velocity anomalies exist in the north atlantic upper mantle beneath both iceland and the azores hotspots both anomalies are above 200 km depth 5 7 per cent slow with respect to prem and are elongated along the mid atlantic ridge low velocities extend to the south of iceland beneath the reykjanes ridge where other geophysical and geochemical observations have indicated the presence of hot plume material a similar but somewhat weaker feature exists beneath the kolbeinsey ridge north of iceland where there is also supporting evidence for the presence of hot plume material this observation might also be associated with a plume beneath jan mayen the low velocity structure beneath the azores hotspot is also elongated along the mid atlantic ridge the fast propagation direction of horizontally propagating sv waves in the atlantic south of iceland correlates well with the east west ridge spreading direction at all depths and changes to a direction close to ns in the vicinity of iceland

determination of rank and petrographic composition of jurassic coals from eastern surat basin australia abstract petrographic analysis and rank determination were carried out on coals from a jurassic sequence in eastern surat basin australia the coals consist mainly of exinite rich clarite with desmocollinite as dominant maceral of the vitrinite group petrographically there is no significant variation in the composition of the coals a herbaceous swamp type free from severe oxidation dehydration appears to have been a dominant depositional environment during the peat accumulation the coal rank ranges from sub bituminous b to high volatile bituminous c b vitrinite reflectance depth profile shows a uniform increase in coalification with depth of burial

using multivariate statistical analysis of groundwater major cation and trace element concentrations to evaluate groundwater flow in a regional aquifer groundwater samples were collected from 11 springs in ash meadows national wildlife refuge in southern nevada and seven springs from death valley national park in eastern california concentrations of the major cations ca mg na and k and 45 trace elements were determined in these groundwater samples the resultant data were subjected to evaluation via the multivariate statistical technique principal components analysis pca to investigate the chemical relationships between the ash meadows and death valley spring waters to evaluate whether the results of the pca support those of previous hydrogeological and isotopic studies and to determine if pca can be used to help delineate potential groundwater flow patterns based on the chemical compositions of groundwaters the results of the pca indicated that groundwaters from the regional paleozoic carbonate aquifers all of the ash meadows springs and four springs from the furnace creek region of death valley exhibited strong statistical associations whereas other death valley groundwaters were chemically different the results of the pca support earlier studies where potentiometric head levels 18o and d geological relationships and rare earth element data were used to evaluate groundwater flow which suggest groundwater flows from ash meadows to the furnace creek springs in death valley the pca suggests that furnace creek groundwaters are moderately concentrated ash meadows groundwater reflecting longer aquifer residence times for the furnace creek groundwaters moreover pca indicates that groundwater may flow from springs in the region surrounding scotty s castle in death valley national park to a spring discharging on the valley floor the study indicates that pca may provide rapid and relatively cost effective methods to assess possible groundwater flow regimes in systems that have not been previously investigated copyright 1999 john wiley sons ltd

three dimensional geological modelling and multivariate statistical analysis of water chemistry data to analyse and visualise aquifer structure and groundwater composition in the wairau plain marlborough district new zealand summary concerns regarding groundwater contamination with nitrate and the long term sustainability of groundwater resources have prompted the development of a multi layered three dimensional 3d geological model to characterise the aquifer geometry of the wairau plain marlborough district new zealand the 3d geological model which consists of eight litho stratigraphic units has been subsequently used to synthesise hydrogeological and hydrogeochemical data for different aquifers in an approach that aims to demonstrate how integration of water chemistry data within the physical framework of a 3d geological model can help to better understand and conceptualise groundwater systems in complex geological settings multivariate statistical techniques e g principal component analysis and hierarchical cluster analysis were applied to groundwater chemistry data to identify hydrochemical facies which are characteristic of distinct evolutionary pathways and a common hydrologic history of groundwaters principal component analysis on hydrochemical data demonstrated that natural water rock interactions redox potential and human agricultural impact are the key controls of groundwater quality in the wairau plain hierarchical cluster analysis revealed distinct hydrochemical water quality groups in the wairau plain groundwater system visualisation of the results of the multivariate statistical analyses and distribution of groundwater nitrate concentrations in the context of aquifer lithology highlighted the link between groundwater chemistry and the lithology of host aquifers the methodology followed in this study can be applied in a variety of hydrogeological settings to synthesise geological hydrogeological and hydrochemical data and present them in a format readily understood by a wide range of stakeholders this enables a more efficient communication of the results of scientific studies to the wider community

variability of geochemical properties in a microbially dominated coalbed gas system from the eastern margin of the illinois basin usa this study outlines gas characteristics along the southeastern margins of the illinois basin and evaluates regional versus local gas variations in seelyville and springfield coal beds our findings suggest that high permeability and shallow 100 250 m depths of these indiana coals allowed inoculation with methanogenic microbial consortia thus leading to widespread microbial methane generation along the eastern marginal part of the illinois basin low maturity coals in the illinois basin with a vitrinite reflectance ro 0 6 contain significant amounts of coal gas 3 m 3

age dependence of oceanic intraplate seismicity and implications for lithospheric evolution we have determined depths for 16 oceanic intraplate earthquakes using body wave modeling a data set composed of these and 11 other well constrained depths shows that the maximum depth of seismicity deepens with increasing lithospheric age and appears to be bounded by a 700 800 c isotherm the maximum depth to which intraplate earthquakes occur is approximately equal to the flexural elastic thickness but much less than the seismic thickness from surface wave dispersion the maximum faulting depth is consistent with the predictions of rapid weakening at high temperatures for dry olivine rheologies determined by experimental rock mechanics oceanic intraplate earthquakes can occur at greater depths and temperatures than has previously been reported for continental crustal events presumably because oceanic lithosphere is stronger at high temperatures both the number of earthquakes and the cumulative seismic moment decrease with lithospheric age the cause of this trend is unclear possibilities include nonrandom location of preexisting weak zones with respect to the age provinces fault strengthening with age or a decrease in the stress level a decrease in intraplate stress with age is opposite that expected from ridge push stresses which increase with age but may result either from thermoelastic stresses which are greatest in young lithosphere or near ridge stress concentrations due to local heterogeneities in the spreading process

stable isotope geochemistry of coal bed and shale gas and related production waters a review coal bed and shale gas can be of thermogenic microbial or of mixed origin with the distinction made primarily on the basis of the molecular and stable isotope compositions of the gases and production waters methane ethane carbon dioxide and nitrogen are the main constituents of coal bed and shale gases with a general lack of c2 hydrocarbon species in gases produced from shallow levels and more mature coals and shales evidence for the presence of microbial gas include 13c ch4 values less than 50 covariation of the isotope compositions of gases and production water carbon and hydrogen isotope fractionations consistent with microbial processes and positive 13c values of dissolved inorganic carbon in production waters the co2 reduction pathway is distinguished from acetate methyl type fermentation by somewhat lower 13c ch4 and higher d ch4 but can also have overlapping values depending on the openness of the microbial system and the extent of substrate depletion crossplots of 13c ch4 versus 13c co2 and d ch4 versus 13c h2o may provide a better indication of the origin of the gases and the dominant metabolic pathway than the absolute carbon and hydrogen isotope compositions of methane in the majority of cases microbial coal bed and shale gases have carbon and hydrogen isotope fractionations close to those expected for co2 reduction primary thermogenic gases have 13c ch4 values greater than 50 and 13c values that systematically increase from c1 to c4 and define a relatively straight line when plotted against reciprocal carbon number although coals and disseminated organic matter in shales represent a continuum as hydrocarbon source rocks current data suggest a divergence between these two rock types at the high maturity end in deep basin shale gas reversals or rollovers in molecular and isotopic compositions are increasingly reported in what is effectively a closed shale system as opposed to the relative openness in coal measure environments detailed geochemical studies of coal bed and shale gas and related production waters are essential to determine not only gas origins but also the dominant methanogenic pathway in the case of microbial gases

active tectonics of the eastern sunda and banda arcs the tectonics of the eastern sunda and banda arcs of eastern indonesia are inferred from the centroid depths seismic moments and fault plane solutions of 63 large earthquakes that occurred between 1962 and 1984 source parameters are estimated by inverting long period teleseismic p and sh waves earthquakes show that the collision of the australian continent with the banda arc shortens the upper plate beneath the forearc and back arc basin over the broad area between the timor and seram troughs along the eastern end of the sunda arc and along the southern banda arc earthquakes reveal that the arc and forearc respond to collision by shortening in the direction of convergence by elongating in the direction perpendicular to convergence and by thrusting over the back arc basin shallow thrust and strike slip earthquakes beneath the banda basin the back arc basin demonstrate that deformation within the back arc accommodates some of the northward motion of the australian continent the rate of north south shortening of the entire upper plate at the longitude of timor calculated from the seismic moments of the earthquakes over the 22 year period is roughly 20 of the predicted convergence rate between australia and southeast asia strike slip faulting within the banda basin results also in eastward motion of the banda arc with respect to western indonesia and australia eastward extrusion of the banda arc results in thrusting at the aru trough earthquakes due to thrusting of the back arc basin beneath the volcanic arc are too shallow to corroborate that the arc s polarity has reversed although the wetar back arc thrust zone at present has a high seismic slip rate earthquakes and their mechanisms provide evidence that the lithosphere of the weber basin a 7500 m deep forearc basin rests on the subducting lithosphere without intervening asthenosphere so that the weber basin subsides in response to sinking of the subducting lithosphere closure of the banda basin is geometrically incompatible with the australian plate subducting simultaneously beneath both the timor and seram troughs instead the bird s head which subducts beneath seram is decoupled from the australian plate in western new guinea and probably moves west or southwest with respect to australia in the eastern indonesian example strike slip faulting plays a major role in the evolution of the collision zone and clearly demonstrates the complexity in three dimensions of continental accretion and mountain building by arc continent collision

crustal motion in indonesia from global positioning system measurements terrestrial reference frame 2000 we compute poles of rotation for the australia eurasia and pacific plates based on our analysis of the global gps data we find that regional tectonics is dominated by the interaction of four discrete rotating blocks spanning significant areas of the sunda shelf the south banda arc the bird s head region of new guinea and east sulawesi the largest the sunda shelf block ssh is estimated to be moving 6 3 mm yr se relative to eurasia the south banda block sbb rotates clockwise relative to both the ssh and australia plate resulting in 15 8 mm yr of motion across the timor trough and 60 3 mm yr of shortening across the flores sea southern new guinea forms part of the australia plate from which the bird s head block bhb moves rapidly wsw subducting beneath the seram trough the east sulawesi block rotates clockwise about a nearby axis with respect to the sunda shelf thereby transferring east west shortening between the pacific and eurasia plates into north south shortening across the north sulawesi trench except for the sunda shelf the crustal blocks are all experiencing significant internal deformation in this respect crustal motion in those regions does not fit the microplate tectonics model index terms 1206 geodesy and gravity crustal movements interplate 8155 1243 geodesy and gravity space geodetic surveys 8150 tectonophysics plate boundary general 3040 8158 tectonophysics plate motions present and recent 3040 9320 information related to geographic region asia keywords crustal motion indonesia tectonics gps current plate motions southeast asia

the long term strength of europe and its implications for plate forming processes field based geological studies show that continental deformation preferentially occurs in young tectonic provinces rather than in old cratons this partitioning of deformation suggests that the cratons are stronger than surrounding younger phanerozoic provinces however although archaean and phanerozoic lithosphere differ in their thickness and composition their relative strength is a matter of much debate one proxy of strength is the effective elastic thickness of the lithosphere te unfortunately spatial variations in te are not well understood as different methods yield different results the differences are most apparent in cratons where the bouguer coherence method yields large te values 60 km whereas the free air admittance method yields low values or 1 5 gyr old is much larger mean te 60 km than that of younger lithosphere mean te 30 km we propose that this strength difference reflects changes in lithospheric plate structure thickness geothermal gradient and composition that result from mantle temperature and volatile content decrease through earth s history

compositional data analysis as a robust tool to delineate hydrochemical facies within and between gas bearing aquifers isometric log ratios of proportions of major ions derived from intuitive sequential binary partitions are used to characterize hydrochemical variability within and between coal seam gas csg and surrounding aquifers in a number of sedimentary basins in the usa and australia these isometric log ratios are the coordinates corresponding to an orthonormal basis in the sample space the simplex the characteristic proportions of ions as described by linear models of isometric log ratios can be used for a mathematical descriptive classification of water types this is a more informative and robust method of describing water types than simply classifying a water type based on the dominant ions the approach allows a compositional distinctions between very similar water types to be made and b large data sets with a high degree of variability to be rapidly assessed with respect to particular relationships compositions that are of interest a major advantage of these techniques is that major and minor ion components can be comprehensively assessed and subtle processes which may be masked by conventional techniques such as stiff diagrams piper plots and classic ion ratios can be highlighted results show that while all csg groundwaters are dominated by na hco3 and cl ions the proportions of other ions indicate they can evolve via different means and the particular proportions of ions within total or subcompositions can be unique to particular basins using isometric log ratios subtle differences in the behavior of na k and cl between csg water types and very similar na hco3 water types in adjacent aquifers are also described a complementary pair of isometric log ratios derived from a geochemically intuitive sequential binary partition that is designed to reflect compositional variability within and between csg groundwater is proposed these isometric log ratios can be used to model a hydrochemical pathway associated with methanogenesis and or to delineate groundwater associated with high gas concentrations

stable isotope and water quality analysis of coal bed methane production waters and gases from the bowen basin australia abstract coal bed methane cbm is a significant growing industry in queensland s energy sector it is however a relatively new industry with little local water quality data and stable isotope compositions of production waters and gases available in the public domain this study aims to determine whether water quality and stable isotope data can be correlated with gas and groundwater production and flow pathways and identify zones of recharge and water mixing stable isotope analysis and accessory water quality tests were conducted on cbm production gas and water samples collected from two cbm producing bituminous coal seams within a single field in the bowen basin in the production field the reservoir seams are gently folded with eastwardly dipping fold axes and compartmentalised by an ene normal fault on the flank of a broad central anticline that contains minor faults for one seam splitting and a change in coal quality parallels the fault and fold axes although virgin reservoir conditions were similar differing production performance north and south of the main fault suggests it acts as a barrier to water and gas flow along strike the stable isotope analysis on the production water showed that waters with more positive d and 18o compositions were associated with areas of higher water production and shallower depths whereas more negative d and 18o compositions were associated with lower water production and high gas production the gas isotope analysis showed that production gases had both biogenic and thermogenic origins and that secondary biogenic gas generated through co2 reduction comprises a significant portion of the cbm produced from this field more negative ch4 13c values characterize the zones of meteoric recharge in shallow up dip areas gas production data and co2 13c values suggest that this may result from 13ch4 stripping by the recharge waters and or increased biogenic activity in this area smaller co2 ch4 carbon isotopic fractionation values characterized zones of meteoric recharge whereas higher isotopic fractionation values characterized the high gas production domain

methanogenic pathways of coal bed gas in the powder river basin united states the geologic factor abstract coal bed gas of the tertiary fort union and wasatch formations in the powder river basin in wyoming and montana u s was interpreted as microbial in origin by previous studies based on limited data on the gas and water composition and isotopes associated with the coal beds to fully evaluate the microbial origin of the gas and mechanisms of methane generation additional data for 165 gas and water samples from 7 different coal bed methane bearing coal bed reservoirs were collected basinwide and correlated to the coal geology and stratigraphy the c1 c2 c3 ratio and vitrinite reflectance of coal and organic shale permitted differentiation between microbial gas and transitional thermogenic gas in the central part of the basin analyses of methane 13c and d carbon dioxide 13c and water d values indicate gas was generated primarily from microbial co2 reduction but with significant gas generated by microbial methyl type fermentation aceticlastic in some areas of the basin microbial co2 reduction occurs basinwide but is generally dominant in paleocene fort union formation coals in the central part of the basin whereas microbial methyl type fermentation is common along the northwest and east margins isotopically light methane 13c is distributed along the basin margins where d is also depleted indicating that both co2 reduction and methyl type fermentation pathways played major roles in gas generation but gas from the latter pathway overprinted gas from the former pathway more specifically along the northwest basin margin gas generation by methyl type fermentation may have been stimulated by late stage infiltration of groundwater recharge from clinker areas which flowed through highly fractured and faulted coal aquifers also groundwater recharge controlled a change in gas composition in the shallow eocene wasatch formation with the increase of nitrogen and decrease of methane composition of the coal bed gas other geologic factors such as burial thermal and maturation history lateral and vertical continuity and coalification of the coal beds also played a significant role in controlling methanogenic pathways and provided new perspectives on gas evolution and emplacement the early stage gas produced by co2 reduction has mixed with transitional thermogenic gas in the deeper central parts of the powder river basin to form old gas whereas along the basin margins the overprint of gas from methyl type fermentation represents new gas thus a clear understanding of these geologic factors is necessary to relate the microbiological biogeochemical and hydrological processes involved in the generation of coal bed gas

olivine friction at the base of oceanic seismogenic zones 1 we investigate the strength and frictional behavior of olivine aggregates at temperatures and effective confining pressures similar to those at the base of the seismogenic zone on a typical ridge transform fault triaxial compression tests were conducted on dry olivine powder grain size 60 m at effective confining pressures between 50 and 300 mpa using argon as a pore fluid temperatures between 600 c and 1000 c and axial displacement rates from 0 06 to 60 m s axial strain rates from 3 10 6 to 3 10 3 s 1 yielding shows a negative pressure dependence consistent with predictions for shear enhanced compaction and with the observation that samples exhibit compaction during the initial stages of the experiments a combination of mechanical data and microstructural observations demonstrate that deformation was accommodated by frictional processes sample strengths were pressure dependent and nearly independent of temperature localized shear zones formed in initially homogeneous aggregates early in the experiments the frictional response to changes in loading rate is well described by rate and state constitutive laws with a transition from velocity weakening to velocity strengthening at 1000 c microstructural observations and physical models indicate that plastic yielding of asperities at high temperatures and low axial strain rates stabilizes frictional sliding extrapolation of our experimental data to geologic strain rates indicates that a transition from velocity weakening to velocity strengthening occurs at approximately 600 c consistent with the focal depths of earthquakes in the oceanic lithosphere

active deformation in the new guinea fold and thrust belt seismological evidence for strike slip faulting and basement involved thrusting the new guinea fold and thrust belt forms a 1000 km long mountain chain running the length of new guinea but its trend is oblique to the predicted convergence direction a large component of left lateral shear across the mountain belt is expected but geological evidence for such motion is ambiguous surface structures in the fold and thrust belt show mountain building by folding and thrusting supposedly thin skinned of pre pliocene continental shelf sediments although some evidence indicates that active faulting penetrates the basement we examine the active deformation of this mountain belt by using teleseismic long period p and sh waveforms short period p waveforms and p wave first motions to determine reliable focal mechanisms and source depths for the 18 largest earthquakes in the new guinea fold and thrust belt since 1964 eight thrust events with seismic moments m0 between 1017 and 2 1018 n m are distributed throughout the thrust belt at depths ranging from 0 5 to 45 km and have steeply dipping fault planes that strike parallel to surface structural trends six of the eight events are between 11 and 25 km deep the steep dips of nodal planes the depths of these earthquakes and the known thicknesses of the sedimentary section show that thrust faulting is not exclusively thin skinned i e confined above a shallow detachment surface but penetrates the crystalline basement at high angles most earthquakes in the western half of the thrust belt including the three largest earthquakes examined m0 5 1018 n m show strike slip faulting with the probable fault plane oriented east west so that displacement is left lateral the nine strike slip earthquakes account for almost 90 of the observed seismic moment in the period 1964 1985 and indicate a seismic slip rate of 5 25 mm a all but one of these strike slip earthquakes are shallower than the thrust earthquakes suggesting that east northeast convergence across the fold and thrust belt is accommodated by a decoupled system of strike slip and dip slip faults while the great height of the mountain belt is an obvious indication that crustal thickening is an important consequence of plate motion in new guinea seismological evidence suggests that translation by strike slip faulting may play a much greater role than previously recognized by analogy in older collisional orogens whose motions can be inferred only from remnant structures and not from seismicity strike slip faulting may have been equally important in accommodating convergence we estimate from seismic moments of earthquakes and from the volume of the mountains that deformation of the new guinea highlands may account for 5 20 of the total convergence between the pacific plate and australia in new guinea

an enigmatic earthquake in the continental mantle lithosphere of stable north america abstract the existence of earthquakes within continental lithospheric mantle remains a highly controversial topic here we present a detailed set of seismological analyses confirming the occurrence of a mantle earthquake beneath the wind river range of central wyoming combining regional waveform inversion with the analysis of the delay and relative amplitudes of teleseismically observed depth phases we demonstrate that the 2013 wind river earthquake a m w 4 7 highly oblique thrust faulting event occurred at 75 8 km well beneath the base of the crust the magnitude mechanism and location of this earthquake suggest that it represents simple brittle failure at relatively high temperatures within the mantle lithosphere as a result of tectonic rather than magmatic processes

two stage red sea rifting inferred from mantle earthquakes in neoproterozoic lithosphere abstract we use earthquake geothermometry measured heat flow and structural constraints from p wave receiver functions to model the thermal evolution of the lithosphere beneath harrat lunayyir we suggest that the lithosphere thinned to its present 60 km thickness in a second stage of lithospheric thinning at 15 12 ma following initial red sea extension at 27 ma harrat lunayyir is an active volcanic field located in the arabian shield 150 km east of the red sea rift axis in the lithospheric mantle beneath harrat lunayyir we locate 64 high frequency earthquakes at depths of 42 48 km all with m l 2 5 these brittle failure earthquakes must have nucleated at relatively low temperatures based upon global maximum nucleation depths and temperature dependent deformation experimental results therefore the mantle earthquakes show that the upper mantle lithosphere is not in thermal equilibrium with the shallow 60 km underlying asthenosphere our thermal modeling indicates that the lithosphere beneath harrat lunayyir thinned to its current 60 km thickness at 12 2 ma as constrained by thermal modeling of 1 surface heat flow 2 the depth to the mid crustal brittle ductile transition and 3 the depth to the upper mantle brittle ductile transition