calcic amphibole equilibria and a new amphibole plagioclase geothermometer there is currently a dearth of reliable thermobarometers for many hornblende and plagioclase bearing rocks such as granitoids and amphibolites a semi empirical thermodynamic evaluation of the available experimental data on amphibole plagioclase assemblages leads to a new thermometer based on the aliv content of amphibole coexisting with plagioclase in silica saturated rocks the principal exchange vector in amphiboles as a function of temperature in both the natural and experimental studies is left na square 1 right a left alsi 1 right t1 we have analysed the data using 3 different amphibole activity models to calibrate the thermometer reactions 1 edenite 4 quartz tremolite albite 1 2 pargasite 4 quartz hornblende albite 2 the equilibrium relation for both 1 and 2 leads to the proposed new thermometer t frac 0 677p 48 98 y 0 0429 0 008314 ln k and k left frac si 4 8 si right x ab plag where si is the number of atoms per formula unit in amphiboles with p in kbar and t in k the term y represents plagioclase non ideality rtln ab from darken s quadratic formalism dqf with y 0 for xab 0 5 and y 8 06 25 5 1 xab 2 for xab 0 5 the best fits to the data were obtained by assuming complete coupling between al on the t1 site and na in the a site of amphibole and the standard deviation of residuals in the fit is 38 c the thermometer is robust to ferric iron recalculation procedures from electron probe data and should yield temperatures of equilibration for hornblende plagioclase assemblages with uncertainties of around 75 c for rocks equilibrated at temperatures in the range 500 1100 c the thermometer should only be used in this temperature range and for assemblages with plagioclase less calcic than an92 and with amphiboles containing less than 7 8 si atoms pfu good results have been attained on natural examples from greenschist to granulite facies metamorphic rocks as well as from a variety of mafic to acid intrusive and extrusive igneous rocks our analysis shows that the pressure dependence is poorly constrained and the equilibria are not suitable for barometry

a discussion on analytical and numerical modelling of the land subsidence induced by coal seam gas extraction coal seam gas csg is an increasingly important source of natural gas all over the world although the influence of conventional oil and gas extraction on surface subsidence has been widely recognized and studied few studies are carried out on the surface subsidence in coal seam gas fields and its impact on surface infrastructure and the environment this paper discusses modelling of the surface subsidence associated with coal seam gas production by applying both analytical and numerical methods by comparison of results from the numerical model and two analytical models i e the disc shaped reservoir model and the uniaxial compaction model the analytical solutions cannot describe the complex process of water and gas extraction and have the limitations to predict the surface subsidence while the numerical model can be better used in prediction of subsidence after applying the numerical model in numerical analysis the deformation characteristics of coupled fluid flow and the effects of permeability change of coal seam associated overlying and underlying layers and depressurization rates on surface subsidence are investigated the results demonstrate that the proposed model can simulate the production of water and gas from coal seams and the associated surface subsidence

inherited smnd isotope components preserved in monazite inclusions within garnets in leucogneiss from east antarctica and implications for closure temperature studies abstract application of the sm nd dating technique using garnet can be hampered by the presence of minor microscopic to submicroscopic ree rich inclusions in particular monazite and to a lesser extent zircon an acid leaching method using a mixture of hno 3 hcl has been used to tackle the monazite contamination problem with this leaching technique we demonstrate that inherited monazite inclusions have been preserved in garnet formed under high grade metamorphic conditions even very low levels of monazite contamination 0 001 wt have a profound effect on the sm nd system in the garnet analysis of a garnet from a leucogneiss dyke in the northern prince charles mountains eastern antarctica reveals that unleached garnet concentrates and the monazite inclusions as represented by the leachates define an apparent isochron of 1150 30 ma mswd 1 88 which represents a mixing age of inclusions preserving their inherited sm nd isotopic systematics in contrast analyses of the leached garnet concentrates yield much younger ages of 630 to 555 ma model calculations show that the presence of as little as 0 01 wt of monazite inclusions would swamp the sm nd isotope signature of the garnet concentrates this very low level of contamination is beyond the reach of physical purification processes and without leaching contamination is inevitable in inclusion bearing garnets such contamination can lead to older apparent ages than those of garnet formation and thus has profound implications for sm nd as well as u pb garnet chronometry

an analytical coal permeability model for tri axial strain and stress conditions coal permeability is sensitive to the effective stress and is therefore coupled to the geomechanical behaviour of the seam during gas migration as coal shrinks with gas desorption and swells with adsorption understanding this coupling to geomechanical behaviour is central to interpreting coal permeability existing coal permeability models such as those proposed by shi and durucan 2004 and palmer and mansoori 1996 simplify the geomechanical processes by assuming uni axial strain and constant vertical stress however it is difficult to replicate these conditions in laboratory tri axial permeability testing and during laboratory core flooding tests for enhanced coal bed methane often laboratory tests involve a hydrostatic stress state where the pressure in the confining fluid within the tri axial cell is uniformly applied to the sample exterior in this experimental arrangement the sample is allowed to undergo tri axial strain this paper presents two new analytical permeability model representations derived from the general linear poroelastic constitutive law that include the effects of tri axial strain and stress for coal undergoing gas adsorption induced swelling a novel approach is presented to the representation of the effect of coal sorption strain on cleat porosity and thus permeability this involves distinguishing between the sorption strain of the coal matrix the pores or cleats and the bulk coal the developed model representations are applied to the results from a series of laboratory tests and it is shown that the models can predict the laboratory permeability data as part of this characterisation the various sorption strains are identified and it is shown that the pore strain is significantly larger than approximately 50 times the bulk sorption strain the models also provide further insight into how coal permeability varies with coal shrinkage and swelling and how the permeability rebound pressure depends upon the effective stress applied

evaluation of in situ stress changes with gas depletion of coalbed methane reservoirs a sound knowledge of the stress path for coalbed methane cbm reservoirs is critical for a variety of applications including dynamic formation stability evaluation long term gas production management and carbon sequestration in coals although this problem has been extensively studied for traditional oil and gas reservoirs it is somewhat unclear for cbm reservoirs the difference between the stress paths followed in the two reservoir types is expected to be significant given the unique sorption induced deformation phenomenon associated with gas production from coal this results in an additional reservoir volumetric strain which induces a rather abnormal loss of horizontal stress with depletion leading to continuous changes in the subsurface formation stresses both effective as well as total it is suspected that stress changes within the reservoir triggers formation failure after significant depletion this paper describes an experimental study carried out to measure the horizontal stress under in situ depletion conditions the results show that the horizontal stress decreases linearly with depletion under in situ conditions the dynamic stress evolution is theoretically analyzed based on modified poroelasticity associated with sorption induced strain effect additionally the failure tendency of the reservoir under in situ conditions is analyzed using the traditional mohr coulomb failure criterion the results indicate that depletion may lead to coal failure particularly in deeper coalbeds and ones exhibiting large matrix shrinkage

carboniferous fault reactivation at the northern margin of the metal rich gawler craton south australia implications for ore deposit exhumation and preservation abstract the formation of major palaeoproterozoic and mesoproterozoic cu au deposits at the metal rich margins of the gawler craton south australia has received a lot of attention however the relationship between metal occurrences the exhumation level of the crust and the structural architecture of the craton margins is less clear here we present results from apatite fission track thermochronology applied to basement rocks at the northern margin of the gawler craton revealing a differential cooling history with respect to the karari shear zone ksz the ksz is a major shear zone that extends to the moho in reflection seismic images and has a prolonged history of high temperature activity during the paleoproterozoic and mesoproterozoic new apatite fission track data show that samples taken to the north of the ksz record a significant pulse of carboniferous cooling in contrast to the phanerozoic monotonic slow cooling history documented for the area just south of the ksz this carboniferous cooling signal coincides with a sedimentary hiatus between the neoproterozoic devonian officer basin and the late carboniferous to early permian arckaringa basin to the north of the ksz therefore carboniferous cooling can be linked with exhumation and fault reactivation of the ksz at that time which is interpreted to be associated with far field compression caused by the alice springs orogeny 450 300 ma of central australia following carboniferous exhumation a localized thermal overprint was observed in locations associated with palaeogene palaeochannels the extent of phanerozoic exhumation shows a spatial relation with the location of au and or cu fe mineralization in the northern gawler craton areas that were significantly modified by mesoproterozoic mineralizing events such as the olympic iocg province and the central gawler gold province record post silurian exhumation histories related to the alice springs orogeny to the west of these two major mineral provinces archaean early palaeoproterozoic terranes in the northwestern gawler craton with abundant au and cu fe mineral occurrences were not affected by phanerozoic exhumation and denudation these relations suggest that the mesoproterozoic mineralized terranes were more susceptible to phanerozoic deformation compared to the archaean palaeoproterozoic terranes within the stronger parts of the gawler craton hence understanding the timing of fault reactivation and the associated relative exhumation level may provide valuable constraints for ore deposit preservation and mineral exploration within the gawler craton

nd and sr isotopic systematics of central australian granulites chronology of crustal development and constraints on the evolution of lower continental crust nd and sr isotopic data are reported for a granulite terrain in the proterozoic arunta block of central australia sm nd data from a wide range of rock types define a crust formation age of 2 070 125 ma and provide further evidence for voluminous crustal growth in the proterozoic an nd value of 1 5 0 8 indicates a depleted mantle source for this crustal segment and there is no evidence for a large component of significantly older sialic crust field relationships geochemistry and rb sr data for mafic and felsic granulites indicate that intracrustal differentiation and polyphase deformation were followed by granulite facies metamorphism rb depletion at 1 800 ma rb sr data for strongly retrogressed granulites define an age of 1 700 ma which is interpreted as the time of retrograde biotite growth partial melting at the presently exposed crustal level and anatexis at deeper crustal levels were broadly coeval with the retrograde metamorphism sm nd and rb sr isotopic systematics of minerals indicate that the terrain cooled slowly did not experience significant uplift until 1 000 ma and remained at temperatures above 320 c until the late palaeozoic the mineral data are consistent with geological relationships and petrological evidence for a prolonged period of isobaric cooling followed by uplift late in the metamorphic evolution of the terrain the granulite protoliths appear to have formed in a rift which closed within 280 ma of initial separation deformation and granulite facies metamorphism at 1 800 ma are interpreted to be a consequence of collision between the continental blocks which defined the rift regional retrogression and granitoid magmatism at 1 700 ma are attributed to underthrusting of the granulites by lower grade rocks in the final stages of collision subsequent events in the cooling and uplift history appear to have been controlled by the presence of long lived major faults in the crust and a prolonged history of episodic compression in the continental lithosphere the results of this study suggest that granulite terrains in general cannot be equated with lower continental crust but instead represent assemblages of mainly supracrustal rocks which in some instances have been involved in major collision events

impact of geological complexity of the fruitland formation on combined co2 enhanced recovery sequestration at san juan basin pilot site abstract in this study we present well log and 3d seismic interpretations of a coalbed methane reservoir in the late cretaceous fruitland formation in the area surrounding the southwest regional partnership on carbon sequestration s san juan basin carbon sequestration pilot site in new mexico usa the interpretation incorporated geophysical logs from 38 wells located in a 23 km 2 area surrounding the pilot site which lies near the southern edge of the high rate fruitland coal production fairway located along the axis of the san juan basin log interpretations revealed three coal bearing zones upper middle and lower within the fruitland formation that are approximately 7 4 7 and 8 5 m 23 15 5 and 28 ft thick respectively the interpretations indicate that each of these coal zones is split by a parting into upper and lower beds making a total of six mappable coal beds in the area surrounding the co 2 injection well the combined thickness of the upper two coal beds in the upper coal zone varies between 3 5 and 4 8 m 11 5 to 15 7 ft and that of the middle beds from 2 to 4 3 m 6 6 to 14 1 ft thick the thickness of the individual coal beds in the lower coal zone varies from about 2 7 to 4 25 m 9 to 14 ft for the upper bed and from about 3 to 5 5 m 10 to 18 ft for the basal coal bed partings separating the upper and lower coal beds in each zone are on average about 2 m 7 ft in the upper and middle zones and about 1 m 3 5 ft in the lower zone seismic response of the upper middle and lower coal zones was interpreted and correlated through the 23 km 2 area the stratigraphic complexity of this coalbed methane reservoir is also accompanied by considerable structural disharmony between the three coal zones the reservoir complexity revealed in this study may account for lower than expected co 2 injectivity and preferential injection into the lower coal zone during the pilot test

swelling induced volumetric strains internal to a stressed coal associated with co2 sorption abstract it is generally accepted that typical coalbed gases methane and carbon dioxide are sorbed both adsorbed and absorbed in the coal matrix causing it to swell and resulting in local stress and strain variations in a coalbed confined under overburden pressure the swelling interactions of gases within the coal matrix and the resultant changes in the permeability sorption gas flow mechanics in the reservoir and stress state of the coal can impact a number of reservoir related factors these include effective production of coalbed methane degasification of future mining areas by drilling horizontal and vertical degasification wells injection of co2 as an enhanced coalbed methane recovery technique and concurrent co2 sequestration such information can also provide an understanding of the mechanisms behind gas outbursts in underground coal mines the spatio temporal volumetric strains in a consolidated pittsburgh seam coal sample were evaluated while both confining pressure and carbon dioxide co2 pore pressure were increased to keep a constant positive effective stress on the sample the changes internal to the sample were evaluated by maps of density and atomic number determined by dual energy x ray computed tomography x ray ct early time images as soon as co2 was introduced were also used to calculate the macroporosity in the coal sample scanning electron microscopy sem and photographic images of the polished section of the coal sample at x ray ct image location were used to identify the microlithotypes and microstructures the co2 sorption associated swelling and volumetric strains in consolidated coal under constant effective stress are heterogeneous processes depending on the lithotypes present in the time scale of the experiment vitrite showed the highest degree of swelling due to dissolution of co2 while the clay kaolinite and inertite region was compressed in response the volumetric strains associated with swelling and compression were between 15 depending on the location although the effective stress on the sample was constant it varied within the sample as a result of the internal stresses created by gas sorption related structural changes sem images and porosity calculations revealed that the kaolinite and inertite bearing layer was highly porous which enabled the fastest co2 uptake and the highest degree of compression

mauna loa s submarine western flank landsliding deep volcanic spreading and hydrothermal alteration four new remotely operated vehicle dives carried out by monterey bay aquarium research institute mbari reveal a heterogeneous distribution of lithologies and compositions along a transect across the submarine west flank of mauna loa from the outer scarp of the frontal bench to the upper flank the frontal bench is composed predominantly of volcaniclastic sediments ranging from very fine grained monomictic hyaloclastites to coarse grained compositionally mixed volcaniclastic breccias the predominance of subaerially derived clasts suggests accumulations of landslide deposits probably emplaced along a regional shear plane preserved in cataclastic breccias with local foliations and grain trails repeated packages of inversely graded strata are interpreted to reflect thrust imbrication of the resulting volcaniclastic apron during volcanic spreading of mauna loa s western flank similar to that now documented along k lauea s south flank many of the rocks from the bench show evidence for alteration ranging from low grade burial diagenesis to higher grade hydrothermal alteration including phases never before observed in submarine hawaiian rocks including epidote talc sphene and corrensite alteration is concentrated in deformed zones denoting pathways for fluid flow into or out of the volcanic edifice formed at depth the altered rocks were subsequently transported along low angle thrust faults into the bench and exposed along high angle fractures and faults the upper submarine flanks are draped by subaerially erupted submarine emplaced pillow lavas and interbedded hyaloclastites generated by shoreline crossing lava flows basalt glasses indicate mauna loa origin but imply earlier compositions than present day lavas consistent with ar ar ages suggesting eruption 0 28 0 10 ma late stage detachment of a nearshore slump produced the lika 2 debris avalanche that broke through the frontal bench perhaps portending the evolution of the active hilina slump now present on k lauea volcano s south flank

giant blocks in the south kona landslide hawaii a large field of blocky sea floor hills up to 10 km long and 500 m high are gigantic slide blocks derived from the west flank of mauna loa volcano on the island of hawaii these megablocks are embedded in the toe of the south kona landslide which extends 80 km seaward from the present coastline to depths of nearly 5 km a 10 15 km wide belt of numerous smaller 1 3 km long slide blocks separates the area of giant blocks from two submarine benches at depths of 2600 and 3700 m depth that terminate seaward 20 to 30 km from the shoreline similar giant blocks are found on several other major submarine hawaiian landslides including those north of oahu and molokai but the south kona blocks are the first to be examined in detail using high resolution bathymetry dredging and submersible diving dredging of two of the giant blocks brought up pillowed tholeiitic lava observations from the u s navy submersible sea cliff on the asymmetrically steep eastern flank of one block 10 km long and 300 m high revealed a succession of fractured massive basalt laminar lava flows hyaloclastite and pillow lavas chemical analyses of dredged lava identified 19 units that overlap compositionally with lavas from the south rift zone ridge of mauna loa sulfur content indicates that most of the lavas were erupted in subaerial and shallow submarine

stratigraphy and structure of coalbed methane reservoirs in the united states an overview stratigraphy and geologic structure determine the shape continuity and permeability of coal and are therefore critical considerations for designing exploration and production strategies for coalbed methane coal in the united states is dominantly of pennsylvanian cretaceous and tertiary age and to date more than 90 of the coalbed methane produced is from pennsylvanian and cretaceous strata of the black warrior and san juan basins investigations of these basins establish that sequence stratigraphy is a promising approach for regional characterization of coalbed methane reservoirs local stratigraphic variation within these strata is the product of sedimentologic and tectonic processes and is a consideration for selecting completion zones coalbed methane production in the united states is mainly from foreland and intermontane basins containing diverse compressional and extensional structures balanced structural models can be used to construct and validate cross sections as well as to quantify layer parallel strain and predict the distribution of fractures folds and faults influence gas and water production in diverse ways however interwell heterogeneity related to fractures and shear structures makes the performance of individual wells difficult to predict

crustal scale ductile fault systems in the arunta inlier central australia detailed geologic observations along three 100 km long traverses across the early proterozoic arunta inlier central australia indicate that paleozoic ductile shear zones are organized into crustal scale structural systems which control the map pattern and distribution of metamorphic zones two provinces can be distinguished 1 1 a southern one where shear zones form a series of hinterland dipping and south verging imbricate reverse faults in the west redbank area grading eastward into a foreland dipping duplex in the arltunga nappe complex directly north of this complex flat lying paleozoic south directed ductile shear affects a large portion of the crust a point which has been underestimated so far 2 2 the northern province is characterized by both south and north dipping shear zones showing reverse motion to produce a crustal scale pop up structure presumably resulting from a more coaxial deformation history strike slip shear zones become predominant in the eastern part of this province stratigraphic and cross cutting relationships indicate that the southern systems developed first the northern systems probably developed in response to the lock up stages of overthrusting in the southern province one important result of this work is that the distribution of granulite facies rocks and major geophysical anomalies throughout the arunta inlier is best explained by their position relative to the paleozoic ductile fault systems described above there is no need to invoke extensive proterozoic uplift of these lower crustal materials

monitoring and modelling of gas dynamics in multi level longwall top coal caving of ultra thick coal seams part ii numerical modelling abstract the longwall top coal caving method which enables the most productive exploitation of thick ultra thick coal seams may result in a distinct geomechanical response of strata and associated gas emission patterns around longwall layouts a two way sequential coupling of a geomechanical and a reservoir simulator for the modelling of gas emissions around a longwall top coal caving ltcc panels was developed building on the understanding established from the analysis of in situ gas pressure and concentration measurements carried out at coal mine velenje in slovenia model findings have shown that the modelling method implemented can reproduce the dynamic changes of stresses and gas pressure around a ltcc face and predict the total gas emissions and mixed gas concentrations accurately it was found that in ltcc panels although the rate of gas emission from mined coal depends highly on the coal face advance floor coal and roof goaf act as a constant and steady gas source accounting for a considerable part of the overall gas emission research has shown that at first and or second mining levels of multi level ltcc mining a notable stress relief and pore pressure drop induced by fracturing of the mined and roof coal can be experienced within 40 m ahead of the face line in the floor coal on the other hand the pore pressure change was found to extend to 20 m below the mining horizon model results have clearly shown the permeability enhancement and gas mobilisation zones around the ltcc panel which can be the target zones for gas drainage boreholes

unconventional geomechanical testing on coal for coalbed reservoir well design the alberta foothills and plains abstract one unconfined compressive strength ucs test and four high pressure triaxial stress tests were conducted on coal cores in order to best emulate the key issues regarding horizontal wellbore stability coal strength permeability change and coal fines generation during the life cycle of a coalbed methane reservoir the four non trivial stress paths were loading compression lc where the axial stress is increased while the confining stress is held constant loading extension le where the axial stress is held constant while the confining stress is increased unloading compression ulc in which the axial stress is held constant while the confining stress is decreased and unloading extension ule during which the confining stress is held constant while the axial stress is decreased the ucs test showed the expected fractured response of initial non linearity due to fracture closure followed by a linear portion at a certain axial stress and finally by brittle failure of the coal along each of the extension stress and also along the combined compression extension stress paths the coal did not show any visual signs of failure no coal fines were detected in the downstream accumulator subsequent to the permeability tests particle size distribution analysis following loading compression provided an estimate of the optimum diameter of the liner perforations test results showed that as the mean effective confining stress increased permeability decreased due to closure of cleats as the coal was loaded unloaded and reloaded along the same stress path a decrease in permeability below the original measured value permeability hysteresis was noted this could be attributed to one or a combination of two mechanisms deformation due to creep and or cleat damage from previous loading using the best fit approach a compressive hoek brown hb failure envelope was fit with intact parameters of geological strength index or gsi 85 d 1 0 ci 20 5 mpa m i 16 7 and a 0 5 assuming there was no anisotropy in the intact coal an extension envelope was fit using a gsi 55 thus the hb criterion in combination with the gsi can be used to capture the influence of both coal cleating and microfractures on its behaviour during drilling and production of the methane gas

emplacement mechanisms of the south kona slide complex hawaii island sampling and observations by remotely operated vehicle kaiko emplacement of a giant submarine slide complex offshore of south kona hawaii island was investigated in 2001 by visual observation and in situ sampling on the bench scarp and a megablock during two dives utilizing the remotely operated vehicle rov kaiko and its mother ship r v kairei topography of the bench scarp and megablocks were defined in 3 d perspective using high resolution digital bathymetric data acquired during the cruise compositions of 34 rock samples provide constraints on the landslide source regions and emplacement mechanisms the bench scarp consists mainly of highly fractured vesiculated and oxidized a a lavas that slumped from the subaerial flank of ancestral mauna loa the megablock contains three units block facies matrix facies and draped sediment the block facies contains hyaloclastite interbedded with massive lava which slid from the shallow submarine flank of ancestral mauna loa as indicated by glassy groundmass of the hyaloclastite low oxidation state and low sulfur content the matrix facies which directly overlies the block facies and is similar to a lahar deposit is thought to have been deposited from the water column immediately after the south kona slide event the draped sediment is a thin high density turbidite layer that may be a distal facies of the alika 2 debris avalanche deposit its composition overlaps with rocks from subaerial mauna loa the deposits generated by the south kona slide vary from debris avalanche deposit to turbidite spatial distribution of the deposits is consistent with deposits related to large landslides adjacent to other hawaiian volcanoes and the canary islands

a novel approach for modelling coal permeability during transition from elastic to post failure state using a modified logistic growth function abstract although many coal permeability models have been developed in the past decades to describe the coal permeability behaviour under elastic state few of them address the coal permeability change under plastic and post failure state which is often the case within the plastic region adjacent to the excavation face in underground coal mining in this study a methodology to model permeability change from elastic to post failure state is developed by using a modified logistic growth function in conjunction with the classic exponential coal permeability correlation the proposed coal permeability model is a function of mean effective stress which controls the coal compaction and deviatoric effective stress which controls coal fracturing the coal permeability may increase by up to several orders of magnitude after failure and then reaches a plateau during triaxial tests the new model is able to capture this behaviour by matching a set of permeability data in transition from elastic to post failure state under triaxial stress conditions this modelling approach may be used to better understand coal permeability changes associated with mining activities which have applications in the prediction of gas emission risk assessment of coal and gas outburst and analysis of gas drainage near mining openings it is anticipated that the current work may attract more attentions on coal permeability modelling under plastic condition a critical issue for mining safety

high strain deformation and fluid infiltration diachronism of the middle crust new devonian permian alice springs ages 365 290 ma of shear zones in the strangways metamorphic complex central australia abstract the proterozoic granulite facies strangways metamorphic complex smc in the arunta region of central australia was partially hydrated during the devonian carboniferous 380 320 ma alice springs orogeny by amphibolite greenschist facies high strain deformation stable and radiogenic isotope analyses on coeval muscovite and biotite from shear zone samples of the smc were performed to analyse the composition and date the timing of fluid circulation and cooling stable isotope data 18 o and d indicate that in the south of the smc the source of fluids appear to be the thick successions of neoproterozoic heavitree quartzite while another source in the north and central part of the smc may be related to meteoric fluids the heterogeneous 18 o fluid and homogenous d fluid values for muscovite reflect changes in water rock ratios with initial high values in the south and lower in the north possibly suggesting a migration of fluids from south to north as indicated by the evolving 18 o fluid and homogenous d fluid values rb sr muscovite ages of 365 340 ma approximate the time of crystallization and fluid infiltration they also indicate that the shear zones were active at different times during the alice springs orogeny and that some were active prior to the peak carboniferous amphibolite facies metamorphism 40 ar 39 ar muscovite ages of 350 325 ma are mostly interpreted as cooling ages rb sr biotite ages of 335 290 ma are interpreted as cooling ages at 300 c sr closure temperature for biotite and extend the activity of the alice springs orogeny until the permian cooling histories of the wallaby knob and harry creek shear zones which serve as the tectonic boundaries of the smc to the north and south respectively indicate slow cooling 1 for c 30 ma 360 330 ma at both boundaries continuing until 290 ma in the western portion of the harry creek shear zone this slow cooling is associated with passive exhumation i e erosion rapid cooling 20 10 c ma 1 then occurred over c 10 ma 330 320 ma in the wallaby knob shear zone and in the east portion of the harry creek shear zone this change in cooling rate is associated with the combined initiation in the carboniferous of dextral and thrusting deformation by the pinnacles bore and erontonga shear zones

modeling of cbm production co2 injection and tracer movement at a field co2 sequestration site sequestration of carbon dioxide in unmineable coal seams is a potential technology mainly because of the potential for simultaneous enhanced coalbed methane production ecbm several pilot tests have been performed around the globe leading to mixed results numerous modeling efforts have been carried out successfully to model methane production and carbon dioxide co sub 2 injection sensitivity analyses and history matching along with several optimization tools were used to estimate reservoir properties and to investigate reservoir performance geological and geophysical techniques have also been used to characterize field sequestration sites and to inspect reservoir heterogeneity the fate and movement of injected co sub 2 can be determined by using several monitoring techniques monitoring of perfluorocarbon pfc tracers is one of these monitoring technologies as a part of this monitoring technique a small fraction of a traceable fluid is added to the injection wellhead along with the co sub 2 stream at different times to monitor the timing and location of the breakthrough in nearby monitoring wells or offset production wells a reservoir modeling study was performed to simulate a pilot sequestration site located in the san juan coal basin of northern new mexico several unknown reservoir properties at the field site were estimatedmore by modeling the coal seam as a dual porosity formation and by history matching the methane production and co sub 2 injection in addition to reservoir modeling of methane production and co sub 2 injection tracer injection was modeled tracers serve as a surrogate for determining potential leakage of co sub 2 the tracer was modeled as a non reactive gas and was injected into the reservoir as a mixture along with co sub 2 geologic and geometric details of the field site numerical modeling details of methane production co sub 2 injection and tracer injection are presented in this paper moreover the numerical predictions of the tracer arrival times were compared with the measured field data results show that tracer modeling is useful in investigating movement of injected co sub 2 into the coal seam at the field site also such new modeling techniques can be utilized to determine potential leakage pathways and to investigate reservoir anisotropy and heterogeneity less

fracture and 3d seismic interpretations of the fruitland formation and cover strata implications for co2 retention and tracer movement san juan basin pilot test abstract this study presents data on faults and fractures in the fruitland formation and its cover strata at a carbon sequestration pilot site in the high rate fruitland coal fairway in the northeastern san juan basin the study incorporates satellite imagery fracture detection and shear wave anisotropy logs and 3d seismic to identify potential issues that could impact long term reservoir integrity co2 flow and retention the properties of fracture networks within the reservoir and sealing strata are important to understand in carbon sequestration and enhanced recovery efforts fracture networks exert significant control on the ability of a reservoir to retain co2 for long thousand year time frames with minimal leakage local structural complexity at the pilot site resulted in tracer migration patterns that differed from predictions based on regional descriptions of fracture and cleat orientations measured in areas several miles from the site perfluorocarbon pfc tracer breakthrough in the production stream of nearby producing wells for example occurred first in a well to the east in a direction close to the presumed butt cleat trend rather than in a well at equal distance along what had been assumed to be the more permeable face cleat trend the study reveals local tectonic complexity not suggested by well log derived structure maps of the area and suggests that fractures and faults disrupt the local fruitland coal reservoir and the overlying kirtland shale primary seal

submarine growth and internal structure of ocean island volcanoes based on submarine observations of mauna loa volcano hawaii a recent model for the submarine growth of hawaiian volcanoes indicates that these volcanoes are composed mainly of fragmental lava debris formed as lavas enter the ocean this model has major implications for locating earthquake hypocenters and for the landslide hazard potential of these and other ocean island volcanoes observations from submersible dives and analyses of volcanic glasses collected from the western submarine flank of mauna loa indicate that subaerially erupted pillow lavas are abundant at depths of 950 to 1900 m below sea level fragmental lava is an important component of ocean island volcanoes as witnessed during the most recent eruption of kilauea volcano but probably is the dominant lithology only in the upper 1 km of the submarine section a submarine dike complex was discovered 17 km west of the assumed axis of mauna loa9s southwest rift which indicates that its intrusive complex is much broader than previously suspected 20 km vs 8 km the great width of this dike complex may be a consequence of crustal unloading following the south kona landslide or a normal feature of hawaiian rift zones that was previously unrecognized

the giant submarine alika debris slide mauna loa hawaii probably represent multiple subsidence events before during and after the debris avalanches lower slopes of the slide contain distinctive lobate terraced deposits that are interpreted as having been emplaced more slowly prior to the debris avalanches estimated thicknesses of 50 200 m suggest volumes of 200 600 km 3 for the two lobes the combined volume of the entire slide and slump terrane is probably 1500 2000 km 3 the slide deposits predate a 13 ka coral reef and probably postdate the block faulted ninole basalt roughly dated as a few hundred thousand years old the alika slide or a similar deposit recognized on gloria images further north along the hawaiian ridge probably triggered a giant wave that washed 325 m high on lanai at about 100 ka slumping on mauna loa has been most intense adjacent to the large arcuate bend in its southwest rift zone as the rift zone migrated westward away from the growing kilauea volcano slumping events were probably triggered by seismic activity accompanying dike injection along the rift zone such massive slumps landslides and distal submarine turbidity flows appear to be widespread on the flanks of hawaiian volcanoes

metamorphic amphiboles composition and coexistence amphiboles have long been key players in metamorphic petrology the concept of facies was developed for rocks of basaltic composition eskola 1920 1939 fyfe et al 1958 and within this concept amphiboles had a leading role the first appearance of amphiboles the presence of amphiboles of certain compositions or last appearance of amphiboles that are replaced by pyroxene bearing assemblages mark a number of major facies boundaries the transition from greenschist to amphibolite facies is marked in part by hornblende replacing actinolite and the granulite facies is defined by the breakdown of hornblende to orthopyroxene bearing assemblages the blueschist facies is defined by the appearance of glaucophane while the transition from blueschist facies to eclogite facies conditions is indicated by the breakdown of glaucophane to omphacitic pyroxene bearing assemblages references to amphibole names actinolite glaucophane or rocks characterized by certain amphiboles amphibolite hornblende figure prominently in six facies names turner 1981 liou et al 1985 oh et al 1988 evans 1990 peacock 1993 a large part of the literature that is devoted to metamorphic petrology of amphiboles concerns reactions which produce amphiboles from more hydrated mafic igneous rocks or lead to the destruction of amphiboles as they break down to form anhydrous or nearly anhydrous mineral assemblages consequently amphiboles can be thought of as occupying the wide intermediate portion of p t xfluid space in which metamorphic rocks are found the number of citations of the published amphibole nomenclature serves as a yardstick meterstick of the interest in amphiboles and a minimum estimate of the amount of literature devoted to this mineral two versions of the nomenclature of amphiboles have appeared 1978 and 1997 leake 1978 leake et al 1997 and they have been cited a over 2300 times in the past 28 years this works out to a minimum

piggyback tectonics long term growth of kilauea on the south flank of mauna loa abstract compositional and age data from offshore pillow lavas and volcaniclastic sediments along with on land geologic seismic and deformation data provide broad perspectives on the early growth of kilauea volcano and the long term geometric evolution of its rift zones sulfur rich glass rinds on pillow lavas and volcaniclastic sediments derived from them document early underwater growth of a large compositionally diverse alkalic edifice the alkalic rocks yield 40ar 39ar ages as old as about 275 ka transitional composition lavas which mark beginning of the shield stage while most or all the edifice remained below sea level probably first erupted after about 150 ka and tholeiitic lavas of present day type are probably younger than 100 ka breccia clasts from papau seamount and along the lower southwest corner of the hilina bench are derived from subaerial mauna loa requiring that mauna loa s flank underlies western parts of kilauea at shallow depth the volume of the kilauea edifice is therefore smaller 10 000 km3 than previous estimates 15 40 000 km3 lava thickness accumulation rates appear to have remained nearly constant during edifice growth as effusion rates increased from 25 106 m3 yr at end of the alkalic stage to the present day tholeiite rate of 100 106 m3 yr seismic and gravity data show that the deep plumbing system for kilauea s magma supply extends nearly vertically through the oceanic crust at least to mantle depths of 30 35 km directly below its present day caldera proximity of kilauea s caldera to the surface boundary with mauna loa and the presence of mauna loa rocks at shallow depth beneath the south flank are difficult to reconcile with a submarine origin for early kilauea alkalic lavas unless geometric relations between the two volcanoes have changed substantially during growth of the kilauea shield seismic and ground deformation data suggest seaward spreading of the entire south flank of hawaii island independently of the boundary between kilauea and mauna loa along a landward dipping detachment fault system near the basal contact of the composite volcanic edifices with underlying oceanic crust current steady state horizontal displacements increase seaward at rates of 1 5 cm yr on the lower flank of mauna loa and reaching 5 8 cm yr at the kilauea coastline infrequent 100 yr large earthquakes generate similar geometries but 102 larger displacements per event present day kilauea is the more dynamic edifice but prior to inception of kilauea and during its early growth mauna loa is inferred to have undergone intense volcano spreading involving the kaoiki honuapo fault system considered a geometric analog of the hilina system on kilauea cumulative deformation of mauna loa s south flank during growth of kilauea since 200 300 ka is estimated to have involved 10 km of seaward spreading displacing the rift zones of k lauea while its deep plumbing system and summit magma reservoir remained nearly fixed in space kilauea s rift zones rather than migrating southward with time solely due to dike emplacement preferentially on the mobile seaward side alternatively are interpreted to have been transported passively southward piggyback style during shield stage growth of kilauea as a blister on the still mobile south flank of mauna loa such an evolution of kilauea accounts for the arcuate geometry of the present day rift zones proximity of the summit magma supply to the exposed flank of mauna loa initial submarine growth of the ancestral edifice and present day location of mauna loa rocks at shallow depth beneath the south flank of kilauea

geophysical evidence for thick skinned crustal deformation in central australia until now there has been no clear evidence from deep seismic reflection profiles of crustal faults that displace the moho new data from central australia show such a structure in a region characterized by large thrust structures large gravity anomalies and abrupt changes in teleseismic travel times here the principal thrust the redbank deformed zone cuts through the crust and the moho is significantly displaced across it the geological and geophysical evidence leads to a model of thick skinned crustal deformation which occurred in an intra cratonic environment in late devonian time

coupled flow and geomechanical processes during gas production from coal seams abstract permeability in coal seams is sensitive to stress and pore pressure changes an additional influence on this behaviour is the nature of the coal matrix to shrink with gas desorption and swell with adsorption concise relationships for permeability have been developed which incorporate these mechanisms some of which are derived from a geomechanical basis such as the shi durucan model and the palmer mansoori model while these expressions are attractive approaches for defining coal permeability during gas migration the geomechanical behaviour has been simplified by assuming uni axial strain and constant vertical stress in this paper a coupled numerical model is developed and used to investigate the applicability of these geomechanical assumptions for gas drainage from coal seams the modelling approach involved coupling the existing coal seam gas reservoir simulator simed ii with the geomechanical simulator flac3d while simed ii was used to simulate gas migration in a hypothetical coal seam and a series of production scenarios flac3d simulated the geomechanical response of the coal and the adjacent non coal geological formations to fluid pressure and gas content changes imported from simed ii the simulations which considered a range of property values relevant to the san juan basin found that while the assumption of uni axial strain introduced negligible discrepancy the assumption of constant vertical stress leads to significant differences between the shi durucan permeability estimate and that calculated from the simed flac3d simulation especially at early times during production these differences were a result of the pressure and sorption strain changes induced by production leading to arching of stresses in the vicinity of the production well the mechanism was shown to produce significant differences in the calculated gas rate particularly at early times during production

timing relationships between pegmatite emplacement metamorphism and deformation during the intra plate alice springs orogeny central australia in the harts range central australia the upper amphibolite facies to lower granulite facies c 480 460 ma harts range metamorphic complex hrmc and the upper amphibolite facies c 340 320 ma entia gneiss complex are cut by numerous generally peraluminous pegmatites and their deformed equivalents the pegmatites have previously been interpreted as locally derived partial melts however shrimp u pb monazite and zircon dating of 29 pegmatites or their deformed equivalents predominantly from the hrmc reveal that they were emplaced episodically throughout almost the entire duration of the polyphase c 450 300 ma intra plate alice springs orogeny episodes of pegmatite intrusion correlate with the age of major alice springs age structures and with deposition of syn orogenic sedimentary rocks in the adjacent centralian superbasin similar alice springs ages have not been obtained from anatectic country rocks in the hrmc suggesting that the pegmatites were not locally derived instead they are interpreted as highly fractionated granites and imply that much larger parental alice springs age granites exist at depth the mechanism to allow repeated felsic magmatism in an intraplate setting where all exposed rock types had a previous high temperature history is enigmatic however we suggest that episodic underthrusting and dehydration of unmetamorphosed centralian superbasin sedimentary rocks allowed crustal fertility to maintained over a c 140 ma interval during the intra plate alice springs orogeny

metamorphic events in the eastern arunta inlier part 2 nd_sr_ar isotopic constraints in the harts ranges the central province of the eastern arunta inlier is characterised by upper amphibolite facies ortho and paragneisses previously published u pb dating of zircons as well as new sm nd and rb sr data indicate that the intrusive ages of both mafic and felsic orthogneisses are in the range 1780 1740 ma strangways orogeny these rocks had initial nd values of 0 to 3 and depleted mantle model ages of 2 5 2 1 ga and they intruded supracrustal rocks which are now preserved as paragneisses with initial nd of about 15 sm nd and rb sr whole rock isotope data indicate that the hornblende rich amphibolitic gneisses and mylonites in the harts range detachment zone ding and james 1989 were equilibrated at 1473 ma 133 when the rocks experienced hydration isotopic homogenisation and thrust faulting this is the anmatjira event described elsewhere in the arunta inlier and is a predominantly structural influence with thrust faults and hydrous fluid flux accordingly the record of this event by radiogenic geochronometers has been diffuse a problem also exacerbated by the probable influence on these rocks of least one more subsequent lower temperature amphibolite facies metamorphic event in spite of the indications of 1470 ma isotopic homogenisation of amphibolites in the harts ranges rb sr isotopic analyses of all minerals and 40ar 39ar from hornblendes yield ages in the range 450 300 ma using the sm nd system a few garnet hornblende pairs give 1400 1250 ma ages but several of these pairs also yield early palaeozoic ages these data suggest that the central province of the eastern arunta inlier also experienced an early palaeozoic thermal event having cooled from temperatures 550 c during and immediately before the carboniferous alice springs orogeny in the southern province south of the illogwa shear zone micas record mesoproterozoic ages 1500 1250 ma for the rb sr k ar and ar ar systems equivalent to the whole rock ages obtained from the central province to the north of the illogwa shear zone clearly the exposed southern basement cooled to 350 c presumably as a result of uplift and exhumation during the anmatjira event when basement now exposed in the central province remained at depth undergoing one or more additional amphibolite facies events the spectacular contrast in cooling histories across the illogwa shear zone emphasises that this is an important crustal scale tectonic structure

identification of potential locations for well placement in developed coalbed methane reservoirs abstract this study investigates well placement in developed coalbed methane cbm reservoirs a workflow is developed to find potential locations for well placement within the reservoir it consists of a reservoir simulator and statistical analysis the application of this workflow is to reduce the need to perform computationally expensive simulations in large reservoirs to obtain potential locations for drilling an additional well the workflow is also used to study the role of dominant reservoir properties in finding potential locations for well placement the effects of permeability anisotropy gas and water relative permeabilities sorption time and water content in well placement are discussed results demonstrate that permeability anisotropy results in the formation of elliptical drainage areas around the wells when drainage patterns are orthogonal to the direction of placement of wells the drainage area of the reservoir is large and penetrated into distant locations this leads to a non uniform drainage area and extends well placement options to distant locations comparison between well placement in two scenarios with different gas and water relative permeabilities shows that potential locations tend to be on a border region between existing wells and virgin area when water mobility is restricted by water relative permeabilities this region has the advantage of having higher pressure and gas content compared to locations among existing wells in this study changing the sorption time does not affect the well placement within the reservoir except at very early times gas production from presented reservoir models is mainly controlled by darcy flow in cleat system permeability dominated rather than diffusion process in coal matrix

paleozoic deformation and isotopic disturbance in the southeastern arunta block central australia proterozoic metamorphic rocks of the arunta block central australia were thrusted southward over the northern margin of the neoproterozoic to mid paleozoic amadeus basin during the 400 300 ma alice springs orogeny the extent and nature of mid paleozoic ductile deformation in the southeastern arunta block is examined in light of available u pb 40ar39ar k ar rb sr and sm nd isotopic age data most of the proterozoic amphibolite and granulite facies rocks north of the zone of basement cover interaction were exhumed and cooled from above 500 to below 125 c as a result of mid paleozoic nappe formation this suggests that deformation early in the cooling history occurred at amphibolite facies conditions and progressed to greenschist facies conditions later in the cooling history in general shear zone rocks yield the youngest isotopic ages indicating that deformation induced recrystallization grain size reduction or localized thermal perturbations are responsible for the relatively young ages we conclude that shear zones of mid paleozoic age were active under greenschist and amphibolite facies conditions though further work is needed to differentiate whether amphibolite facies shear zones are paleozoic or proterozoic some proterozoic shear zones were uplifted passively in the mid paleozoic resulting in final closure and mixed ages in key minerals like hornblende

ups and downs on spreading flanks of ocean island volcanoes evidence from mauna loa and kīlauea submarine flank deposits of hawaiian volcanoes are widely recognized to have formed largely by gravitationally driven volcano spreading and associated landsliding observations from submersibles show that prominent benches at middepths on flanks of mauna loa and k lauea consist of volcaniclastic debris derived by landsliding from nearby shallow submarine and subaerial flanks of the same edifice massive slide breccias from the mature subaerial tholeiitic shield of mauna loa underlie the frontal scarp of its south kona bench in contrast coarse volcaniclastic sediments derived largely from submarine erupted preshield alkalic and transitional basalts of ancestral k lauea underlie its hilina bench both midslope benches record the same general processes of slope failure followed by modest compression during continued volcano spreading even though they record development during different stages of edifice growth the dive results suggest that volcaniclastic rocks at the north end of the kona bench interpreted by others as distal sediments from older volcanoes that were offscraped uplifted and accreted to the island by far traveled thrusts alternatively are a largely coherent stratigraphic assemblage deposited in a basin behind the south kona bench

permeability changes in coal analytical modeling abstract permeability changes can be very large during depletion of coalbed methane wells up to 100 times in the san juan basin analytic models of permeability increase during depletion are accessible easy to use and practical they are more transparent and less complicated than coupled numerical models however there are minor differences between the analytic models and these are reviewed here there are also discrepancies in attempting to match field data which is the final test of a model and these are discussed two different sets of san juan data have been modeled after suppressing the pressure dependent permeability with reasonably consistent reservoir parameters the matching parameters appear to be justifiable the small porosities do not seem to be ruled out by reservoir experts and the changes of elastic parameters including pore volume compressibility with depletion do not seem unreasonable the analytic models are used in reservoir simulators to model and predict injection of greenhouse gases in coal seams only when we can match the permeability increase of coalbed methane wells during depletion will we have the confidence to use the analytic models in reservoir simulators to match or predict sequestration of greenhouse gases such as co2

desorption induced shear failure of coal bed seams during gas depletion the recovery of natural gas from coal bed seams is usually accompanied by a significant increase of permeability induced by coal matrix shrinkage and stress relaxation upon gas desorption this advantageous increase in permeability may be impaired sometimes by mechanical failure of the reservoir rock and ensuing production of coal fines near wellbore stress concentration and reduction of lateral stresses are known to promote shear failure during depletion in oil and gas reservoir formations yet conventional analyses have shown limited success in predicting coal failure since other chemo physical mechanisms may be responsible in enhancing the conditions towards mechanical failure in the coal bed reservoir rock we show a set of triaxial experiments involving gas desorption from coal cores under zero lateral strain condition radial stress measured and controlled and constant total vertical stress meant to simulate the stress path during production far from the wellbore co2 is used as surrogate fluid for ch4 the experimental data indicates that desorption can significantly help reduce lateral stress and increasing deviatoric stress until shear failure occurs the results suggest that depletion induced shear failure is much more likely to occur in coal seams than in conventional non sorbing reservoir rocks the adsorptive mechanical coupling turns out to be a key phenomenon in the process numerical simulations at the representative elementary volume scale adopting a double porosity poromechanical model support the experimental findings and permit calculating a critical gas pressure for shear failure to happen this emergent phenomenon is comparable to the outcome of other situations such as mineral dissolution or thermal contraction where shrinkage relaxes lateral stress and acts as an intensifying driver for promoting shear failure within the reservoir rock coupled numerical simulation is needed to include near wellbore effects and validate our findings with actual field observations a thorough understanding of the coupled response of coal seams is necessary to enhance reservoir management and mitigate the effects of coal failure on fines production

hyaloclastites and the slope stability of hawaiian volcanoes insights from the hawaiian scientific drilling project s 3 km drill core abstract core samples recovered during the hawaiian scientific drilling project hsdp drilling project reveal that the upper 1 km of the submarine flank of mauna kea is comprised mainly of hyaloclastites progressive very low temperature alteration of these hyaloclastites has been accompanied by systematic transformations in physical properties of these deposits hyaloclastite deposits which directly underlie ca 1 km of subaerially emplaced lavas are very poorly consolidated but over a depth interval of ca 500 m compaction and especially precipitation of zeolitic pore filling cements associated with palagonitization of sideromelane have eliminated porosity as well as promoted the consolidation of these hyaloclastites the latter is reflected in unconfined compressive strengths which increase from mean values respectively of 2 5 and 4 6 mpa in weakly consolidated smectite rich hyaloclastites from the incipient 1080 to 1335 mbsl and smectitic 1405 1573 mbsl alteration zones to a mean value of 10 0 mpa in the more highly consolidated hyaloclastites of the palagonitic zone of alteration from 1573 mbsl to the bottom of the drill hole conversely overlying intercalated and underlying lava flows are generally much less altered and have mean compressive strengths which are 1 to 2 orders of magnitude greater then hyaloclastites at equivalent depths the shear strengths of the hyaloclastites also increase with depth and grade of alteration but are uniformly and substantially lower in the lavas those hyaloclastites exhibiting the highest grade of alteration i e palagonitic also exhibit the highest measured strengths and thus the alteration of hyaloclastites appears to strengthen as opposed to weaken the flanks of the edifice however the contrast in strength between hyaloclastites and lavas may be a primary factor in localizing destabilization and the zones of weak and poorly consolidated hyaloclastites may facilitate slumping by servings as hosts for shallow detachment surfaces on the unsupported flanks of these volcanoes

multi branched horizontal wells for coalbed methane production field performance and well structure analysis abstract horizontal wells such as multi lateral and multi branched horizontal wells mbhws have been effectively used in the development of coalbed methane cbm fields especially for coal beds with very low permeability and low compressive strength in which the performance of conventional fracture stimulated vertical wells is ineffective in this study the performance of mbhws in the liulin block of the ordos basin in central north china is analyzed and compared to that of hydraulically fractured vertical wells the field pilot data show that the gas production rate of most fractured vertical wells decreased rapidly after a short period of time far below expectation while the performance of mbhws is satisfactory and relatively stable during 3 years of production a numerical simulation model was established based on the coal reservoir characteristics the productivities of different well types are predicted and compared to the field data the poor performance of the fractured vertical wells is thought to be caused by the early closure of the fractures and proppant embedded in the coal matrix or by a poor proppant delivery inside the fractures the high and stable productivity of the mbhws is attributed to their large drainage volume and to the stability of the wellbores simulation results show that the parameters of a mbhw such as the branch angle length and spacing can be optimized to maximize its productivity though the drilling cost of a mbhw is relatively high in comparison to vertical wells its high and stable productivity can compensate for the drilling cost therefore mbhws are thought to be more appropriate than vertical wells for the successful exploitation of the cbm resource potential in the liulin block and surrounding area

coal failure during primary and enhanced coalbed methane production theory and approximate analyses abstract this paper presents a study on reservoir scale failure in coal seams during primary and enhanced coalbed methane production two sets of formulations for reservoir scale coal failure analysis are presented one is based on the routine effective stress definition while the other is based on an extended definition two application examples the fruitland reservoir in san juan basin and a reservoir in the sydney basin are investigated in terms of the approximate treatment proposed which employs the common uniaxial strain and constant vertical total stress assumptions the fruitland case study found that the reservoir scale friction angles fitted with the routine effective stress at a failure pressure equal to 1 9 mpa observed and with the assumed weakest low volatile medium volatile coal would be 22 24 if the extended effective stress definition is used the friction angle would be 12 15 the former results are apparently closer to some core scale laboratory results usually above 30 than the latter however as discussed in this paper using the routine effective stress for coal may result in some theoretical anomalies that seem to be fundamentally against the concept of the effective stress in a porous rock i e the pore fluid pressure reduces the effective stress in the rock in contrast the extended effective stress invoked in this text is theoretically more plausible for coal

the effective stress law for stress sensitive transversely isotropic rocks abstract this paper first presents a review of the development of the concept of effective stress followed by major experimental and theoretical studies carried out to estimate the biot s coefficient it then uses the constitutive equations for vertically transverse isotropic vti reservoirs like coal derived using the principles of thermodynamics for estimation of the biot s coefficients in the vertical and horizontal directions laboratory data for tests conducted on two coal types retrieved from different geologic settings and geographical locations was used to carry out the modeling and validation exercise evidence is presented that values of biot s coefficient can be greater than one proposed by biot to be the limiting value for sorptive rocks to address this the term biot s coefficient is replaced with effective stress coefficient finally this paper discusses the pressure and stress dependent behavior of the biot s coefficient the results clearly show that the estimated values of biot s coefficients in both vertical and horizontal directions are different varying with pressure for methane depletion but remaining constant for helium depletion at the same time the nature of biot s coefficient re termed as effective stress coefficient was found to be greater than unity for methane depletion as a last step a conceptual physical model is proposed to explain the pressure dependent variation of effective stress biot s coefficients in terms of the contact area between grains based on the findings that the effective stress coefficient decreases with pressure it is concluded that the effective vertical stress would increase significantly with depletion which in turn would result in shear failure and increased permeability

volcanic spreading on mauna loa volcano hawaii evidence from accretion alteration and exhumation of volcaniclastic sediments a transect of submersible dives across the submarine west flank of mauna loa volcano yields compelling evidence for volcanic spreading and associated hydrothermal circulation during volcano growth a frontal bench at the toe of the flank formerly thought to be a downdropped block of mauna loa contains a mix of volcaniclastic lithologies including distally derived siltstone mudstone and hyaloclastite the bench is overlain by bedded gravels and subaerially erupted pillow flows derived from local shoreline crossing lava flows the volcaniclastic strata in the bench were offscraped uplifted and accreted to the edge of the flank as it plowed seaward into the surrounding moat the accreted strata underwent significant diagenesis through deep burial and circulation of hydrothermal fluids expelled from porous sediments beneath the volcano timing constraints for bench growth and breakup suggest that catastrophic failure of the subaerial edifice ca 250 200 ka triggered volcanic spreading by reducing stresses resisting basal sliding and rift zone inflation increased eruptive activity and westward migration of mauna loa9s southwest rift zone gradually rebuilt the massive flank arresting slip prior to detachment of the alika 2 debris avalanche ca 120 ka

thermal history of the northern olympic domain gawler craton correlations between thermochronometric data and mineralising systems abstract multi method thermochronology applied to the northern olympic domain of south australia reveals a complex thermal evolution with multiple thermal events apatite u pb closure temperature 550 350 c and muscovite 40ar 39ar ages 400 350 c record post magmatic cooling from 1850 to 750 ma for the 1850 ma donington suite and from 1560 1500 ma for the 1590 ma hiltaba suite and the gawler range volcanics potassium feldspar 40ar 39ar ages 350 150 c record disturbed spectra that are likely related to hydrothermal alteration at 1000 650 ma in the neoproterozoic adelaide rift complex apatite fission track 60 120 c zircon u th sm he 180 200 c and apatite u th sm he 45 75 c ages reveal regional low temperature thermal events at 1000 ma 430 400 ma 350 330 ma and 200 ma in addition to localised thermal events during the cretaceous the 1000 ma apatite fission track ages are amongst the oldest recorded for south australia and are only preserved near the margins of the olympic domain the 430 400 ma and 350 330 ma cooling events are interpreted to be driven by the alice springs orogeny the mesozoic thermochronometric ages are interpreted to record localised thermal perturbations possibly related with hydrothermal activity within the northern olympic domain the presence of abundant iocg deposits near these young thermal anomalies may indicate that these zones record more favourable thermal conditions and or exposure levels for iocg discoveries in the study area

assessing the geochemical and tectonic impacts of fluid rock interaction in mid crustal shear zones a case study from the intracontinental alice springs orogen central australia the reynolds anmatjira ranges central australia form part of a high grade basement terrane dissected by intensely metasomatized transpressional shear zones active during the ordovician carboniferous alice springs orogeny unlike typical retrograde structures associated with discrete fluid flow the mid crustal setting and intracontinental nature of these shear systems present significant problems for the source and ingress mechanism of the fluid involved in their rehydration to address these issues we describe two detailed traverses across deformed and metasomatized basement rocks in this region and interrogate their record of fluid rock interaction from various perspectives both traverses combine structural and petrological observations with zr in rutile and ti in quartz thermobarometry oxygen and hydrogen stable isotope analysis and major trace and rare earth element mobility trends each technique is critically evaluated for its utility in this study and its more widespread applicability to alternative field areas providing a strategic framework for the general investigation of fluid affected shear zones ultimately the integrated data sets specify pressure temperature conditions of 530 c and 4 5 kbar implying average apparent thermal gradients of 29 36 c km 1 and depths of 14 18 km other characteristic features to emerge include strongly variable element mobilities and pronounced isotopic depletion fronts consistent with the alteration effects of an externally derived non equilibrium fluid this is confirmed by calculated fluid compositions indicative of contributions from a fluid of meteoric origin with estimated 18o and d values as low as 2 3 and 59 8 respectively we propose that these surficial fluid signatures are imposed on the mid crust by the prograde burial and dehydration of hydrothermally altered fault panels produced during pre orogenic basin formation progressive fluid release with continued subsidence then leads to the accumulation of increasing fluid volumes in the vicinity of the brittle ductile transition promoting extensive hydration metasomatism and reaction softening at the locus of stress transmission from plate boundary sources the sustained injection of externally derived fluids into refractory crustal material may thus stimulate a critical reduction in the long term strength of the lithosphere providing strong impetus for the initiation and advancement of intracontinental orogenesis

stability analysis of hawaiian island flanks using insight gained from strength testing of the hsdp core abstract hawaiian island flank failures are recognized as the largest landslide events on earth reaching volumes of several thousand cubic kilometers and lengths of over 200 km and occurring on an average of once every 100 000 years the 3 1 km deep hawaii scientific drilling project hsdp enabled an investigation of the rock mass strength variations on the island of hawaii schiffman p watters r j thompson n walton a w 2006 hyaloclastites and the slope stability of hawaiian volcanoes insights from the hawaiian scientific drilling project s 3 km drill core journal of volcanology and geothermal research 151 1 3 217 228 this study builds on that of schiffman et al schiffman p watters r j thompson n walton a w 2006 hyaloclastites and the slope stability of hawaiian volcanoes insights from the hawaiian scientific drilling project s 3 km drill core journal of volcanology and geothermal research 151 1 3 217 228 by considering more in depth rock mass classification and strength testing methods of the hsdp core geotechnical core logging techniques combined with laboratory strength testing methods show that rock strength differences exist within the edifice comparing the rock strength parameters obtained from the various volcano lithologies identified weak zones suggesting the possible location of future slip surfaces for large flank failures relatively weak rock layers were recognized within poorly consolidated hyaloclastite zones with increases in strength based on degree of alteration subaerial and submarine basalt flows are found to be significantly stronger with the aid of digital elevation models cross sections have been developed of key flank areas on the island of hawaii limit equilibrium slope stability analyses are performed on each cross section using various failure criteria for the rock mass strength calculations based on the stability analyses the majority of the slopes analyzed are considered stable in cases where instability i e failure is predicted decreased rock mass quality strength of the altered and highly poorly consolidated lithologies is found to have a significant influence these lithologies are present throughout the hawaiian islands representing potential failure surfaces for large flank collapses failure criterion input parameters are considered in sensitivity analyses as are the influences of certain external stability factors such as sea level variation and seismic loading

volcanotectonic interactions between mauna loa and kilauea insights from 2 d discrete element simulations abstract numerical simulations using the discrete element method dem are carried out to examine the dynamics and internal deformation of overlapping volcanoes constructed upon a weak decollement horizon as analogs to the kilauea mauna loa system of volcanoes in hawaii employing a frictional rheology the dem simulations capture much of the complex deformation behavior of mauna loa and kilauea volcanoes here referred to as the primary and secondary edifices respectively the models demonstrate incremental displacements of the outer flanks of the volcanoes and concurrent summit subsidence leading to characteristic low slopes and inward dipping strata slip discontinuities that develop within the piles define steeply dipping normal faults along the upper flanks and beneath the edifice summits that accommodate subsidence and flank spreading edifice overlap influences dynamic behavior significantly even small topographic perturbations restrict the internal deformation and spreading of the confined flanks the degree of buttressing depends on the relative positions of the two edifices if the secondary edifice grows high upon the flanks of the primary edifice outward spreading of the underlying flank is enhanced if the secondary edifice is built low upon the primary flanks spreading of the underlying flank is effectively prevented or possibly reversed furthermore as the second edifice grows it subsides into the underlying flank partitioning it into a mobile downslope region entrained by spreading of the second edifice and a comparatively stable upper flank region these results suggest that much of the mass of kilauea volcano may lie deeply buried within the underlying flank of mauna loa while older mauna loa rocks may lie far from their source beneath the mobile flank of the younger volcano

laboratory based mathematical modelling of graded proppant injection in cbm reservoirs abstract the graded proppant injection into a connected cleat system of coal bed methane cbm reservoir allows deeper particle penetration and straining in the remote open cleats yielding higher well productivity index the analytical model for axisymmetric flow has been derived for exponential stress permeability relationship and accounting for permeability variation outside the stimulated zone laboratory proppant injections into coal cores have been performed for different proppant sizes and water salinities it is shown that the proppant suspension based on low salinity water prevents the particle particle and particle coal attraction with the consequent core inlet plugging and external cake formation however low salinity of the injected water may cause mobilisation migration and straining of the natural reservoir fines resulting in high formation damage the interval where salinity is low enough for the rock inlet not to be plugged by the injected proppant and is high enough for large formation damage due to fine migration not to occur is proposed for the cores under investigation the analytical model is tuned from the laboratory data and used for well index prediction ignoring the model matching by the laboratory results causes the overestimation of the incremental productivity index as achieved by the graded proppant injection into coal beds below the fracturing pressure

numerical modelling of coal seam depressurization during coal seam gas production and its effect on the geomechanical stability of faults and coal beds abstract this coupled geomechanical fluid flow numerical modelling study investigates the geomechanical impact of depressurization of coal beds on fault and coal seam geomechanical stability during coal seam gas production using a simplified 3d reservoir structure based on the gloucester basin eastern australia the model examines transient stress pore pressure and fluid flow patterns during gas production under three different background regional stress scenarios with the aim of understanding possible geomechanical failure states in a fault and coal beds the model results show that depressurization leads to shear stress increase in normal faulting stress regimes but decreases in reverse faulting dominant in eastern australia and strike slip faulting stress regimes this is in combination with an overall effective stress increase associated with pore pressure reduction depressurization resultant fault failure appears to be possible only under normal stress regimes in addition a critically stressed fault segment is likely to be a precursor requirement for fault reactivation to occur as a result of depressurization fluid depletion within normal faulting stress conditions results further show fluid flow is dominated by lateral flow along coal beds converging towards depressurization locations wells fault permeability governs fluid transport along across the fault and development of pore pressure compartmentalisation across the fault under all three background stress scenarios flow velocities in coal beds are governed by coal permeability

north kona slump submarine flank failure during the early tholeiitic shield stage of hualalai volcano abstract the north kona slump is an elliptical region about 20 by 60 km 1000 km 2 area of multiple geometrically intricate benches and scarps mostly at water depths of 2000 4500 m on the west flank of hualalai volcano two dives up steep scarps in the slump area were made in september 2001 using the rov kaiko of the japan marine science and technology center jamstec as part of a collaborative japan usa project to improve understanding of the submarine flanks of hawaiian volcanoes both dives at water depths of 2700 4000 m encountered pillow lavas draping the scarp and bench slopes intact to only slightly broken pillow lobes and cylinders that are downward elongate dominate on the steepest mid sections of scarps while more equant and spherical pillow shapes are common near the tops and bases of scarps and locally protrude through cover of muddy sediment on bench flats notably absent are subaerially erupted hualalai lava flows interbedded hyaloclastite pillow breccia and or coastal sandy sediment that might have accumulated downslope from an active coastline the general structure of the north kona flank is interpreted as an intricate assemblage of downdropped lenticular blocks bounded by steeply dipping normal faults the undisturbed pillow lava drape indicates that slumping occurred during shield stage tholeiitic volcanism all analyzed samples of the pillow lava drape are tholeiite similar to published analyses from the submarine northwest rift zone of hual lai relatively low sulfur 330 600 ppm and water 0 18 0 47 wt contents of glass rinds suggest that the eruptive sources were in shallow water perhaps 500 1000 m depth in contrast saturation pressures calculated from carbon dioxide concentrations 100 190 ppm indicate deeper equilibration at or near sample sites at water depths of 3900 to 2800 m either vents close to the sample sites erupted mixtures of undegassed and degassed magmas or volatiles were resorbed from vesicles during flowage downslope after eruption in shallow water the glass volatile compositions suggest that the tholeiitic lavas that drape the slump blocks were erupted either 1 early during shield stage tholeiitic volcanism prior to emergence of a large subaerial edifice or alternatively 2 from submarine radial vents during subaerial shield building because no radial vents have been documented on land or underwater for the unbuttressed flanks of any hawaii volcano alternative 1 is favored in comparison to other well documented hawaiian slumps and landslides north kona structures suggest a more incipient slump event with smaller down slope motions and lateral displacements

modelling permeability for coal reservoirs a review of analytical models and testing data abstract as with other reservoir types permeability is a key controlling factor for gas migration in coalbed methane reservoirs the absolute permeability of coal reservoirs changes significantly during gas production often initially decreasing but then increasing as the reservoir pressure and gas content is drawn down it has also been observed to decrease markedly during co2 injection to enhance coalbed methane recovery in order to predict gas migration models for coal permeability must represent the mechanisms leading to these observed behaviours the permeability of coal reservoirs behaves in a similar fashion to other fractured reservoirs with respect to effective stress decreasing exponentially as the effective stress increases however a unique effect of coal is that it shrinks with gas desorption and swells with adsorption within the reservoir this swelling shrinkage strain leads to a geomechanical response changing the effective stress and thus the permeability modelling coal permeability incorporating the impacts from both effective stress and coal swelling shrinkage dates back about 25 years since then a number of permeability models have been developed in recent years this topic has seen a great deal of activity with a growing body of research on coal permeability behaviour and model development this article presents a review of coal permeability and the approaches to modelling its behaviour as an important part of this the field and laboratory data used to test the models are reviewed in detail this article also aims to identify some potential areas for future work

stress damage flow coupling model and its application to pressure relief coal bed methane in deep coal seam abstract long distance pressure relief gas drainage technology has recently been applied in mining areas with multiple coal seams of low permeability in china this study briefly described a coupled stress damage flow model which combined the evolution of stress damage and gas permeability with the deformation of coal and rock the coupled model was then used to investigate the deformation and fracture characteristics of overburden strata the evolution of gas permeability and gas flow in target coal seams the effectiveness of long distance pressure relief gas drainage was evaluated on the basis of the calculated results from a dynamic modelling of extraction of protective coal seam at great depths the numerical results revealed that the stress was remarkably relieved in the target coal seam above 67 m away from the coal seam being mined moreover the range of stress relief extended above 70 m and the gas permeability increased by more than 2000 times the modelled results reasonably well agreed with the field results observed in the panyi coal mine it was concluded that the long distance pressure relief gas drainage technology could effectively improve the safety and productivity in underground coal mines especially in mining areas with multiple coal seams of low permeability

metamorphic events in the eastern arunta inlier part 1 metamorphic petrology abstract in the entia dome of the eastern arunta inlier kyanite facies metamorphism is recorded over a substantial area at least 160 km 2 and thus contrasts with the regionally extensive belts of high temperature low pressure andalusite sillimanite facies metamorphism documented elsewhere in the arunta inlier this amphibolite facies event appears to postdate regional granulite facies metamorphism evidence for which is almost totally obliterated in the entia dome prograde kyanite occurs in meta basites in comparatively rare associations involving hornblende staurolite and anorthite and in other rocks in association with gedrite and hornblende or garnet and biotite these kyanite bearing assemblages equilibrated at intermediate temperatures 570 710 c at peak pressures of 7 kbar and are overprinted by lower pressure assemblages including hornblende gedrite cordierite and sillimanite while this sequence of reactions may be simply interpreted in terms of a single clockwise orogenic cycle textural evidence and the available mineral isotopic data suggest a more complex history involving multiple heating and cooling episodes during the mesoproterozoic and possibly the palaeozoic the occurrence of regional retrogressive kyanite facies assemblages in the eastern arunta inlier provides evidence that the widely held perception that proterozoic crustal evolution in australia involved a distinct ensialic orogenic style characterised by high geothermal gradients etheridge et al 1987 loosveld and etheridge 1990 sandiford and powell 1991 is not universally true rather petrological evidence presented here with isotopic constraints described by foden et al 1995 suggests that the harts range region has experienced substantial crustal reworking at elevated temperatures during both the proterozoic and palaeozoic under thermal regimes more familiar to modern continental collision zones

two new geobarometers for garnet amphibolites with applications to southeastern vermont two new geobarometers for the assemblage garnet hornblende plagioclase quartz have been calibrated on the basis of the equilibrium 6 anorthite 3 tremolite 2 grossular 1 pyrope 3 tschermakite 6 quartz and its fe end member equivalent data representing 37 natural samples that equilibrated at conditions of 2 5 to 13 kbar and 500 to 800 c were fitted to the general equation rt in keq a bt p i c by using a weighted least squares method multiple correlation coefficients are high 0 98 and 0 97 lines of constant keqhave extremely shallow slopes in p t space 2 to 8 bars per degree suggesting that pressures may be deduced precisely even where temperatures are only poorly constrained typical analytical errors and temperature imprecisions propagate to very small errors in pressure about 500 bars caution is advised in applying the barometers outside the range of calibrant mineral compositions application of the calibrations to samples from southeastern vermont near the strafford chester and athens domes documents relatively high pressure metamorphism 7 to 10 kbar for these structures

sm nd evidence for high grade ordovician metamorphism in the arunta block central australia sm nd ages from the harts range in the south eastern arunta inlier in central australia indicate that regional metamorphism up to granulite facies occurred in the early ordovician c 475 ma this represents a radical departure from previous tectonic models for the region and identifies a previously unrecognized intraplate event in central australia peak metamorphic assemblages 800 c and 10 5 kbar formed at around 476 14 ma and underwent approximately 4 kbar of near isothermal decompression at 475 4 ma a coarse grained unfoliated garnet clinopyroxene bearing marble inferred to have recrystallized late in the decompressional evolution gives an age of 469 7 ma two lines of evidence suggest the early ordovician tectonism occurred in an extensional setting first the timing of the high grade lower crustal deformation coincides with a period of marine sedimentation in the amadeus and georgina basins that was associated with a seaway that developed across central australia second isothermal decompression of lower crustal rocks was associated with the formation of a regional sub horizontal mid crustal foliation in the entia gneiss complex which forms the structurally lowest part of the harts range upper amphibolite facies metamorphism c 700 c 8 9 kbar occurred at 479 15 ma there is no evidence that p t conditions in the entia gneiss complex were as high as in the overlying units this implies that the extensional system was reworked during a later compressional event sm nd data from the mid amphibolite facies c 650 c and 6 kbar detachment zone that separates the irindina supracrustal assemblage and entia gneiss complex give an age of 449 10 ma this age corresponds to the timing of a change in the pattern and style of sedimentation in the amadeus and georgina basins and indicates that the change in basin dynamics was associated with mid crustal deformation it also suggests that compressional deformation culminating in the devonian to carboniferous 400 300 ma alice springs orogeny may have begun as early as c 450 ma at present the extent of early ordovician tectonism in central australia is unknown however granulite facies metamorphism and associated intense deformation imply an event of regional extent an implication of this work is that high grade lower crustal metamorphism and intense deformation occurred during the development of a broad shallow slowly subsiding intraplate basin

overthrusting and sediment accretion along kilauea s mobile south flank hawaii evidence for volcanic spreading from marine seismic reflection data a large intermittently active submarine landslide known as the hilina slump has been interpreted along the south flank of kilauea volcano seaward dipping faults on land mark its headwall and an offshore bench may define its uplifted toe geodetic data show that the entire south flank is also moving seaward by a process referred to as volcanic spreading this provides an alternative explanation for the bench i e overthrusting along the edge of the sliding flank the latter interpretation is consistent with new seismic reflection data across the submarine flank a prominent reflection near the top of the oceanic plate suggests the decollement upon which the mobile flank slides landward dipping reflections rise from this horizon and bound packages of bedded strata faulted and imbricated within the bench the absence of correlative seaward dipping faults and rotated strata on the upper flank suggests that the bench is not coupled to a slump moreover kinematic reconstructions of the bench indicate that it has accommodated 15 24 km of displacement this value is consistent with estimates for rift zone extension but too high for shortening at the toe of a slump we interpret the bench to result from overthrusting and accretion of volcaniclastic sediments to the edge of the mobile flank and suggest that morphologic benches develop preferentially where landslide debris has accumulated near the base of the volcano and can be accreted to its sliding edifice

flow simulations for carbon sequestration at a coal seam pilot site computer simulations of the flow and diffusion of h2 o ch4 and co2 through unmineable coal seams are integral parts of the design implementation and interpretation of carbon sequestration field projects although it has seldom been discussed in the literature coal seams may also effect ively serve as cap rock for sequestration into underlying formations brine saturated oil and gas reservoirs or other coal seams in this case the very large sorption capacities of coal even at low co2 pressures the blockage of co2 flow through cleats when they are saturated with h2 o and the tendency of coal to swell when it sorbs co2 thus reducing cleat apertures and darcy flow all may contribute to make coal seams effective caprock

coal seam failure during primary enhanced gas production how failure develops in fields abstract coal failure has been observed in many coal seam reservoirs during gas production which generated significant impacts to coal permeability and to the efficiency of gas recovery in this paper we develop a flow geomechanical coupled numerical approach and use two genuine field examples to discuss the relevant large scale coal failure behaviours in fields one example is with the cbm production in cedar hill reservoir san juan basin and the other one is with the co2 injected ecbm process in allison unit san juan basin major observations from the present work include 1 laboratory tests and analytical analyses based on uniaxial strain conditions may have considerable deviations in prediction of the coal failure during gas production in fields because such a condition would not hold there because of non uniform pressure distributions in the field due to gas production injection 2 field scale coal strength parameters e g the friction angle should be remarkably weaker than its counterparts measured with core samples because if otherwise the coal failure that has been observed would not occur 3 in cbm processes coal failure usually occurs first in the immediate vicinity of a wellbore and then may expand to the whole field with continuing gas depletion 4 ecbm processes can have complex strain history including inelastic coal failure due to primary production as well as elastic unloading due to co2 injection

an assessment based on u_pb zircon data of rb_sr dating in the arunta inlier central australia abstract the chronology of the arunta inlier was originally based mostly on rb sr dating although some of the ages derived from that technique are now shown to be erroneous those which were constrained by structural observations and which relied only on whole rock and not mineral analyses have proven to be remarkably realistic ion microprobe data show that even conventional multigrain u pb zircon analysis is not a particularly appropriate dating technique in a region of this complexity three new u pb zircon ages and others previously derived from the same isotopic system date three of the main tectonic events that were imposed on the arunta inlier the widespread strangways orogeny of the northern and central provinces occurred at 1760 1750 ma the argilke event is not older than 1680 ma demonstrating that the southern province is the youngest in the inlier the dominantly thermal ormiston event is dated at 1140 ma

temperature pressure conditions in coalbed methane reservoirs of the black warrior basin implications for carbon sequestration and enhanced coalbed methane recovery abstract sorption of gas onto coal is sensitive to pressure and temperature and carbon dioxide can be a potentially volatile supercritical fluid in coalbed methane reservoirs more than 5000 wells have been drilled in the coalbed methane fields of the black warrior basin in west central alabama and the hydrologic and geothermic information from geophysical well logs provides a robust database that can be used to assess the potential for carbon sequestration in coal bearing strata reservoir temperature within the coalbed methane target zone generally ranges from 80 to 125 f 27 52 c and geothermal gradient ranges from 6 0 to 19 9 f 1000 ft 10 9 36 2 c km geothermal gradient data have a strong central tendency about a mean of 9 0 f 1000 ft 16 4 c km hydrostatic pressure gradients in the coalbed methane fields range from normal 0 43 psi ft to extremely underpressured geothermal gradients within the coalbed methane fields are high enough that reservoirs never cross the gas liquid condensation line for carbon dioxide however reservoirs have potential for supercritical fluid conditions beyond a depth of 2480 ft 756 m under normally pressured conditions all target coal beds are subcritically pressured in the northeastern half of the coalbed methane exploration fairway whereas those same beds were in the supercritical phase window prior to gas production in the southwestern half of the fairway although mature reservoirs are dewatered and thus are in the carbon dioxide gas window supercritical conditions may develop as reservoirs equilibrate toward a normal hydrostatic pressure gradient after abandonment coal can hold large quantities of carbon dioxide under supercritical conditions and supercritical isotherms indicate non langmiur conditions under which some carbon dioxide may remain mobile in coal or may react with formation fluids or minerals hence carbon sequestration and enhanced coalbed methane recovery show great promise in subcritical reservoirs and additional research is required to assess the behavior of carbon dioxide in coal under supercritical conditions where additional sequestration capacity may exist

coupling of swelling internal stress evolution and diffusion in coal matrix material during exposure to methane we construct theoretical models for time dependent swelling of coal matrix material upon adsorption of a single gas taking into account a coupling between stress strain chemical potential and diffusion two models are developed the first model a corresponds to diffusion and hence swelling rates being controlled by the jump frequency of adsorbed molecules between closely spaced adsorption sites and the second model b to transport controlled by diffusion of unadsorbed molecules through diffusion paths linking distant adsorption sites to test these models we performed axial swelling experiments on a single 4 mm sized cylindrical sample of medium volatile bituminous coal exposed to ch4 at pressures up to 40 mpa at 40 c using 1 d high pressure dilatometry the models were calibrated to the experimental data by adjustment of a single valued diffusion coefficient independent of gas pressure and adsorbed concentration the results show that the data can be accurately explained only by model b the implication is that the gas transport the associated adsorption and hence time dependent swelling are controlled by the diffusion of unadsorbed molecules and not by molecules jumping between the adjacent adsorption sites our model describes a full coupling between stress strain sorption and diffusion in coal matrix material in terms of parameters that have clear physical meaning and are easily obtained from sorption and swelling experiments on coal of any rank exposed to any gas it therefore offers an important tool for modeling permeability evolution with time during enhanced coalbed methane operations 2017 american geophysical union all rights reserved

volumetric strain associated with methane desorption and its impact on coalbed gas production from deep coal seams the permeability of deep 1000 m 3300 ft coal seams is commonly low for deep coal seams significant reservoir pressure drawdown is required to promote gas desorption because of the langmuir type isotherm that typifies coals hence a large permeability decline may occur because of pressure drawdown and the resulting increase in effective stress depending on coal properties and the stress field during production however the permeability decline can potentially be offset by the permeability enhancement caused by the matrix shrinkage associated with methane desorption the predictability of varying permeability is critical for coalbed gas exploration and production well management we have investigated quantitatively the effects of reservoir pressure and sorption induced volumetric strain on coal seam permeability with constraints from the adsorption isotherm and associated volumetric strain measured on a cretaceous mesaverde group coal piceance basin and derived a stress dependent permeability model our results suggest that the favorable coal properties that can result in less permeability reduction during earlier production and an earlier strong permeability rebound increase in permeability caused by coal shrinkage with methane desorption include 1 large bulk or young s modulus 2 large adsorption or langmuir volume 3 high langmuir pressure 4 high initial permeability and dense cleat spacing and 5 low initial reservoir pressure and high in situ gas content permeability variation with gas production is further dependent on the orientation of the coal seam the reservoir stress field and the cleat structure well completion with injection of n2 and displacement of ch4 only results in short term enhancement of permeability and does not promote the overall gas production for the coal studied

a fully coupled coal deformation and compositional flow model for the control of the pre mining coal seam gas extraction abstract fully coupled compositional coal seam gas and air model of coal deformation coal gas flow and transport and air flow in coal seams is developed to better understand the gas drainage processes and the coal gas air mixing mechanisms during pre mining coal seem gas extraction the model was first verified by showing that the modelled gas concentration profiles match reasonably with the in situ measured ones the verified model was then applied to evaluate how the drained gas concentration could be controlled under different conditions of the sealing length the leakage rate and the leakage fracture width these modelled results provides the basis of a new in situ control technology of gas air mixing which uses fine expansive particles to seal the leakage fractures around the borehole this technology has been commercially applied to enhance the concentration of the pre mining gas drainage the field test shows that the characteristics of the leakage fractures are greatly changed after the particles are injected into the in seam drainage borehole when the gas concentration declines once the leakage fractures are blocked with the particles the outside air is prevented from entering the coal seam thus an ideal gas concentration can be maintained and the duration of higher gas concentration is extended for boreholes with an originally low gas concentration 0 30 the new technology can increase the gas concentration by 10 65 and extend the production time by approximately two to three months the total amount of gas drainage increases to 2000 3000 m 3 per borehole

thermal history and differential exhumation across the eastern musgrave province south australia insights from low temperature thermochronology abstract multi method geo and thermochronological data obtained for palaeo and mesoproterozoic granitoids traversing the main structural architecture of the eastern musgrave province within south australia reveal multiphase cooling histories apatite u pb dating on six samples yield consistent ages of 1075 1025 ma suggesting a thermal reset coinciding with mantle derived magmatism of the greater warakurna large igneous province 1080 1040 ma apatite fission track aft analysis indicate that four discrete thermal events affected the study area inducing cooling through the aft partial annealing zone 60 120 c supported by apatite and zircon u th sm he data late neoproterozoic cooling from deep crustal levels to temperatures the results highlight a complex phanerozoic thermal history for the eastern musgraves and help to elucidate the poorly appreciated tectonic evolution of inland australia this study further demonstrates how high density sample transects across structural architecture can assess the relative crustal level and associated preservation of the thermal history record within fault reactivated terranes

dynamic variation effects of coal permeability during the coalbed methane development process in the qinshui basin china abstract the commercial exploitation of coalbed methane cbm has been achieved in the qinshui basin china however the productivity of wells varies greatly because of their different geological settings and production rules and the permeability damage to coal reservoirs caused during the development process is one of the most important factors affecting productivity in this study the patterns of permeability variation in coal seam no 3 and their influence on cbm recovery were analyzed and the degree of permeability damage caused by different factors was calculated the results show that the burial depth the bottom hole pressure and the dewatering rate affected the effective stress imposed on the coal reservoir which further induced changes in permeability and productivity the elastic modulus of the coal body reflects its ability to withstand compression the greater the elastic modulus is the less the permeability decreases when the pressure drops from 7 05 mpa to 0 20 mpa the relatively low elastic modulus of coal seam no 3 can cause a 10 decrease in permeability coals at different burial depths have different formation pressures and elastic moduli causing different levels of permeability damage during the development process calculations indicate that the absolute permeability will decrease by 5 5 and 14 3 at depths of 500 m and 1000 m respectively if the bottom hole pressure drops too fast or the dewatering rate is too high there will be a strong stress response resulting in decreasing permeability and productivity this study found that in high productivity wells a larger pressure drop approximately 0 022 mpa d and stroke 3 0 min are favorable in the early drainage period but a smaller pressure drop 0 002 mpa d and stroke 0 4 min should be applied when the gas peak appears

physical and chemical properties of submarine basaltic rocks from the submarine flanks of the hawaiian islands abstract to evaluate physical and chemical diversity in submarine basaltic rocks approximately 280 deep submarine samples recovered by submersibles from the underwater flanks of the hawaiian islands were analyzed and compared based on observations from the submersibles and hand specimens these samples were classified into three main occurrence types lavas coarse grained volcaniclastic rocks and fine grained sediments each with several subtypes the whole rock sulfur content and porosity in submarine basaltic rocks recovered from depths greater than 2000 m range from

thermomechanical evolution of a ductile duplex the thermomechanical evolution of a midcrustal ductile duplex in central australia has been reconstructed through space and time using 40ar 39ar thermochronology flow stress estimates cross sectional restoration of dislocation creep microstructures and microstructural and structural analysis a critical aspect of this analysis is the identification of populations of white micas in quartzite mylonites that have neocrystallized below their closure temperature and which record the time when ductile deformation ceased in dating these micas the mylonitic microstructures have effectively been dated the time temperature history of the duplex has been constrained through multidomain thermal modeling of k feldspar 40ar 39ar data the modeling demonstrates that a temperature gradient existed across the duplex during its formation the concept of microstructural continuity during ductile deformation has great potential for elucidating the kinematic evolution of ductile duplexes mapping of the deformation mechanisms and recrystallized grain sizes of quartzites deformed under greenschist facies conditions has been used to evaluate tectonic offsets that occurred after microstructural freezing this analysis shows that the duplex formed as a forward propagating thrust system accommodating 60 km of convergence between the upper and lower plates of the megathrust with a significant fraction of the displacement occurring after microstructural freezing finally using the data as input to published flow laws for quartz aggregates provides a strain rate history for the duplex although uncertainties are clearly large the timing of highest estimated strain rates during duplex evolution does indeed correlate with the highest rates of convergence between the upper and lower plates of the megathrust system according to regional cooling history studies and with coeval sedimentation in adjoining molasse basins

structure of the mobile south flank of kilauea volcano hawaii how do huge landslides occur in hawaii we can begin to address this question by examining an incipient landslide structure on the mobile south flank of kilauea volcano between 1970 and 1989 this part of the south flank moved in a southeast direction seaward by 4 m on its eastern end and by 10 m on its western end parallel to the western boundary of a large oifshore topographic bench we show that abrupt decreases in cumulative flank movement correspond to abrupt decreases in hypocenter concentration most of the earthquakes occur in a 7 to 10 km deep band beneath the south flank and relative relocation of a subset of these events shows that they are derived from a single horizontal plane which appears to be a decollement focal mechanisms for this deep seismicity are dominated by thrust fault mechanisms with the overlying block moving seaward a comparison of south flank bathymetry with decollement structures on other volcanoes suggests that the distal end of this decollement coincides with the distal end of the offshore topographic bench 30 50 km from shore and 5 km below sea level the fault system forming the hilina pali is connected with this decollement so that slip on the hilina pali s normal faults coincides with slip of the decollement and with reverse faulting of the distal end of the bench this interpretation is supported by studies of the events associated with the m7 2 kalapana earthquake in 1975 when the hilina pali is connected to the outer bench with a decollement inferred from seismicity a wedge 8 km thick adjacent to kilauea s magma system and 1 2 km thick along the edge of the outer bench an area over 3000 km2 is defined the thickness adjacent to the magma system decreases eastward along kilauea s east rift zone and southwestward from kilauea caldera whereas the thickness of the lip of the outer bench decreases only eastward geologic observations and geophysical studies of the subaerial flank reveal an extensive magma system beneath the koae fault system as well as beneath kilauea caldera and its east rift zone we infer that the boundary of the proximal end of the mobile flank is the southern boundary of this magma system and that this boundary coincides with the southern boundaries of both the koae fault system and kilauea s east rift zone

intracontinental orogeny enhanced by far field extension and local weak crust the accommodation of intraplate stresses in preexisting weak regions of plate interiors is here investigated using thin viscous sheet numerical models the intraplate stresses are governed by multicomponent and multidirectional stresses originating at plate boundaries the modeled scenarios mimic plate boundary conditions during the intraplate alice springs orogeny aso central australia and include 1 a northwest southeast zone of weak lithosphere within strong continental blocks to the north and southand 2 a principal south directed stress condition at the northern boundary that causes minor clockwise rotation of the northern block alternative tectonic environments are investigated in additional models that include 1 secondary compressional or extensional stresses acting at the eastern boundary representing the temporally variable stress conditions during the tasmanides orogeny and 2 an eastern wedge shaped zone of rheologically weak lithosphere mirroring rift fill of the irindina subbasin our results highlight that a low angle between major crustal features e g orogenic elongation and preexisting regional structures and the principal transmitted stresses is highly relevant in the concentration of elevated levels of differential stress and subsequent localization of deformation in plate interiors secondary stresses orthogonal to the principal acting stresses may introduce effects that explain the episodic orogenic activity in the case of the aso the combination of secondary extensional stresses at the eastern boundary of australia and weak lithosphere of the preexisting irindina subbasin strongly influences the observed spatial strain intensity localization and kinematics of deformation during the aso

experimental study of swelling of organic rich shale in methane abstract gas is stored in shale mainly in free and adsorbed phases since a significant amount of gas in the shale is adsorbed to the organic matter and or clay minerals it is possible that gas adsorption will induce shale swelling which may then has an impact on the gas flow behavior in the shale thus its gas production in this work strain behavior was studied in two gases helium and methane at different pore pressures under constant hydrostatic pressure at 20 mpa on two shale samples the results show that porosity and volumetric strain are functions of gas pressure and the strain is larger in methane than helium demonstrating gas adsorption induced swelling for the shale samples the calculated methane adsorption induced swelling strain is at a magnitude of 0 1 volumetrically with pressure at 10 mpa for the shale samples studied the adsorption induced shale swelling strain shows a langmuir like relationship with pressure and is proportional to the amount of methane adsorbed the results also show slight anisotropic strain behavior between the two directions of parallel and perpendicular to the bedding and strain hysteresis with methane in and out of the shale the gas adsorption induced swelling may influence gas flow in gas shale thus more research in this topic is warranted

geochronological constraints on orogenic events in the arunta inlier a review early workers subdivided the arunta inlier central australia into three major tectonic provinces classified the principal tectonostratigraphic units into three divisions and separated the tectonomagmatic history into five discrete events ranging in age from 1800 ma to 300 ma a review of the evidence for tectonic boundaries within the arunta inlier suggests that no major structural discontinuity exists between the northern and central tectonic provinces but that the redbank thrust zone is at least in part a province boundary the tectonostratigraphic division concept also requires revision as division 3 rocks of the northern and southern arunta cannot be time equivalents division 1 rocks grade into division 2 in the northern region and division 3 of the northern region may be equivalent to division 1 in the central region rocks originally assigned to divisions are better grouped into a larger number of lithological assemblages until better stratigraphic and isotopic correlations can be made compilation of rb sr and 40ar39ar age determinations obtained before 1984 indicate an almost complete age spectrum from 1800 ma to 1000 ma but age clusters exist at 1400 ma 1100 ma and 400 300 ma which have geological significance subdivision of older ages into discrete tectonic events was not justified from this data alone but more recent u pb isotopic analysis of zircons in rocks designated to particular structural metamorphic events has revealed a complex tectonic history in the 1880 1600 ma interval the northern and central provinces underwent major tectonism between 1780 1730 ma but much of the southern province was not deformed until 1600 ma the revised tectonic history nomenclature is proposed for the arunta inlier following deposition of a widespread turbiditic unit at or before 1880 ma possibly on thinned archaean crust the northern and central provinces underwent localized tectonism magmatism at 1880 ma yuendumu tectonic event and 1820 ma stafford tectonic event prior to the widespread strangways orogeny which is subdivided into an early phase at 1780 1770 ma and late phase at 1745 1730 ma it is not clear whether the strangways orogeny is a single arunta wide event or a series of separate short lived smaller scale events although the major deformation in all areas appears to have involved w to sw directed thrusting in the southern province the major events occurred at 1680 ma argilke tectonic event and 1600 ma chewings orogeny the latter involving n directed thrusting that was penecontemporaneous with post tectonic pegmatite intrusion in the northern province suggesting linkage of both regions at this stage the younger history of the inlier is characterised by several stages of uplift and isolated thermal magmatic events major mesoproterozoic crustal exhumation anmatjira uplift phase has been interpreted from widespread 1500 1400 ma ages including regional scale closure of 40ar 39ar systems in hornblende from mafic granulite outcrop scale rb sr total rock isotopic systems in mylonitized granitoids and sm nd garnet hornblende pairs in mylonitized amphibolites a 1150 ma thermal event in the southern part of the inlier teapot magmatic event is recorded by intrusion of granite pegmatites and the alkaline mordor igneous complex and by isotopic resetting of rb sr mineral systems dolerite dyke injection at 1050 ma reflects limited extensional tectonism that may have related to formation of the amadeus basin the second major uplift event was the alice springs orogeny at 400 300 ma an unusual intracratonic thick and thin skinned thrust event that involved limited retrograde amphibolite facies but extensive greenschist facies metamorphism and restricted pegmatite intrusion

high resolution geochemical record of fluid rock interaction in a mid crustal shear zone a comparative study of major element and oxygen isotope transport in garnet garnet grains from an intensely metasomatized mid crustal shear zone in the reynolds range central australia exhibit a diverse assortment of textural and compositional characteristics that provide important insights into the geochemical effects of fluid rock interaction electron microprobe x ray maps and major element profiles in situ secondary ion mass spectrometry oxygen isotope analyses and u pb and sm nd geochronology are used to reconstruct their thermal temporal and fluid evolution these techniques reveal a detailed sequence of garnet growth re equilibration and dissolution during intracontinental reworking associated with the ordovician carboniferous 450 300 ma alice springs orogeny a euhedral garnet porphyroblast displays bell shaped major element profiles diagnostic of prograde growth zoning during shear zone burial coexisting granulitic garnet porphyroclasts inherited from precursor wall rocks show extensive cation re equilibration assisted by fracturing and fragmentation oxygen isotope variations in the former are inversely correlated with the molar proportion of grossular suggesting that isotopic fractionation is linked to ca substitution the latter generally show close correspondence to the isotopic composition of their precursor indicating slow intergranular diffusion of o relative to fe2 mg and mn peak metamorphism associated with shearing 550 c 5 0 6 5 kbar occurred at c 360 ma followed by rapid exhumation and cooling progressive mn enrichment in rim domains indicates that the retrograde evolution caused partial garnet dissolution accompanying intra mineral porosity production then stimulated limited oxygen isotope exchange between relict granulitic garnet grains and adjacent metasomatic biotite resulting in increased garnet 18o values over length scales 200 m spatially restricted oxygen interdiffusion was thus facilitated by increased fluid access to reaction interfaces the concentration of ca in channelled fracture networks suggests that its mobility was enhanced by a similar mechanism in contrast the intergranular diffusion of fe2 mg and mn was rock wide under the same p t regime as demonstrated by a lack of local spatial variations in the re equilibration of these components the extraction of detailed reaction histories from garnet must therefore take into account the variable length and time scales of elemental and isotopic exchange particularly where the involvement of a fluid phase enhances the possibility of measureable resetting profiles being generated for slowly diffusing components such as ca and o even at low ambient temperatures and relatively fast cooling rates

using geological strength index gsi to model uncertainty in rock mass properties of coal for cbm ecbm reservoir geomechanics abstract the use of geostatistics has become an important concept to characterize uncertainty in reservoir simulations only recently has the concept been applied to geomechanics and coupled reservoir geomechanical simulations the work presented here describes how the geological strength index gsi is used to represent the fractured reservoir properties of a coalseam reservoir and link changes in flow properties with stress changes as well as to strength and deformation the approach is demonstrated by using a spherical geostatistical model to create 11 gsi realizations and one constant gsi model two years of primary methane production and then 3 months co 2 storage were simulated using each of the 12 models as inputs much higher cumulative gas and gas production rate profiles were observed for models with a mean gsi below 80 than the 80gsi model all models above 80 gsi show much lower cumulative gas and gas production rates than the 80gsi model the same trend held true for the co 2 injection component of the operation stress path profiles for three monitoring points in the reservoir showed large variability but similar paths whereas monitoring points in the overlying caprock showed very low variability for each realization

granulite facies metamorphism in the mallee bore area northern harts range implications for the thermal evolution of the eastern arunta inlier central australia abstract the mallee bore area in the northern harts range of central australia underwent high temperature medium to high pressure granulite facies metamorphism individual geothermometers and geobarometers and average p t calculations using the program thermocalc suggest that peak metamorphic conditions were 705 810c and 8 12 kbar partial melting of both metasedimentary and meta igneous rocks forming garnet bearing restites occurred under peak metamorphic conditions comparison with partial melting experiments suggests that vapour absent melting in metabasic and metapelitic rocks with compositions close to those of rocks in the mallee bore area occurs at 800 875c and 9 10 kbar the lower temperatures obtained from geothermometry imply that mineral compositions were reset during cooling following the metamorphic peak the rocks underwent local mylonitization at 680 730c and 5 8 7 7 kbar after mylonitization ceased garnet retrogressed locally to biotite which was probably caused by fluids exsolving from crystallizing melts these three events are interpreted as different stages of a single continuous clockwise p t path the metamorphism at mallee bore probably occurred during the 1745 1730 ma late strangways orogeny and the area escaped significant crustal reworking during the anmatjira and alice springs events that locally reached amphibolite facies conditions elsewhere in the harts ranges

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

metamorphic and tectonic evolution of granulites arunta block central australia petrographical and chemical evidence presented here indicate a prolonged metamorphic evolution of the granulite terrain in the northern strangways range arunta block central australia nsr in fig 1 beginning with migmatization followed by dry granulite metamorphism at high temperatures t and moderate pressures p estimated at 850 920 c 8 1 kbar1 this occurred at 1 800 myr refs 2 3 very shortly after deposition of the protolith4 a bimodal volcanic suite5 and associated sediments granulite metamorphism was followed by isobaric cooling during which there was an episode of pervasive but partial hydration later retrogression and hydration localized along shear zones occurred at the normal geothermal gradient in the kyanite stability field a tensional rift like regime best describes the geological environment in which the protolith formed was deeply buried metamorphosed with high heat flow and then remained in isostatic equilibrium metamorphic parageneses recording uplift may be matched with mid palaeozoic tectonic events in central australia if this correlation is correct the rocks of the northern strangways range may have remained deeply buried for 1 400 myr during which the shear zones were reactivated several times fig 2

exhumation of the lower crust during crustal shortening an alice springs 380 ma age for a prograde amphibolite facies shear zone in the strangways metamorphic complex central australia foliated garnet bearing amphibolites occur within the west bore shear zone cutting through granulite facies gneisses of the strangways metamorphic complex in the amphibolites large euhedral garnet up to 3 cm occurs within fine grained recrystallized leucocratic diffusion haloes of plagioclase quartz the garnet and their haloes include a well developed vertical foliation also present in the matrix this foliation is the same as that cutting through the unconformably overlying neoproterozoic heavitree quartzite the textures indicate syn to late kinematic growth of the amphibolite facies mineral assemblages all mineral assemblages record an arrested prograde reaction history noteworthy is the growth of garnet at the expense of hornblende and plagioclase and the breakdown of staurolite hornblende to give plagioclase gedrite these dehydration reactions indicate increasing p t conditions during metamorphism and suggest heating towards the end of a period of intense deformation temperature estimates for the garnet amphibolite and related staurolite hornblende assemblages from the shear zone are about 600 c pressure is estimated at about 5 kbar an sm nd isochron gives an age of 381 7 ma for the peak metamorphism and associated deformation this age determination confirms that amphibolite facies conditions prevailed during shear zone development within the strangways metamorphic complex during the alice springs orogeny these temperature conditions are significantly higher than those expected at this depth assuming a normal geothermal gradient the alice springs orogeny was associated with significant crustal thickening allowing exhumation of the granulite facies palaeoproterozoic lower crust along strike variations of the tectonic style suggest a larger amount of crustal shortening in the eastern part of the alice springs orogeny

experimental research on the permeability of high rank coal under a varying stress and its influencing factors abstract in order to investigate the permeability behavior of high rank coal during early depletion of cbm and its influencing factors we collected 14 coal samples from ordos basin in northwest china and determined their air permeability under a varying effective stress of 2 5 20 mpa in laboratory we used effective confining pressure to simulate effective stress it turns out that high rank coal permeability is susceptible to effective stress permeability of coal samples declines exponentially with the rise of effective stress on the whole when effective confining pressure variation ranges from 2 5 mpa to 10 mpa permeability varies dramatically when effective confining pressure rises to above 10 mpa the curve of permeability decline gets gentle and the stress sensitivity becomes relatively weak coal permeability is also affected by coal moisture maceral fracturing and metamorphism degree permeability rises with the increase of vitrinite content and fracturing degree and decreases with the increase of moisture content permeability of wet and fractured coal samples is more sensitive to effective stress than dry intact ones and the irreversible permeability loss rate of fractured coal cores is significant over 80 comparison of tests results of medium and low rank coal samples and high rank ones shows that the stress sensitivity coefficient decreases with the increase of the maximum reflectance of vitrinite if experiencing the same load relief process the irreversible permeability loss rate of low rank coal is less than that of medium and high rank coals

folded basement cored tectonic wedges along the northern edge of the amadeus basin central australia evaluation of orogenic shortening abstract intracontinental deformation at the northern margin of the amadeus basin central australia is characterised by the presence of basement cored downward facing antiformal synclines these structures were formed during the devonian carboniferous alice springs orogeny and in the past were explained as erosional relics of fold nappes indicating large horizontal crustal shortening within the australian continent this notion is in stark contrast with both the uncomplicated homoclinal structure that contains the nappes and with seismic data suggestive of a simple crustal structure formed during only modest intraplate shortening balanced and sequentially restored sections across the razorback nappe and its vicinity show that such downward facing synformal anticlines can be produced by emplacement of a basement cored tectonic wedge along shortcut thrusts in the footwall of a crustal scale redbank shear zone which initially formed during the mesoproterozoic the forelandward propagating wedge proper is formed by basement and the lower two successions of the amadeus basin higher sedimentary successions accommodate shortening by hinterlandward backthrusting above a detachment horizon which is hosted in carbonates and evaporites of the bitter springs formation during the formation of the homocline which characterises much of the northern margin of the amadeus basin the tectonic wedge was rotated through 90 and now forms a downward facing antiformal syncline the orogenic shortening indicated by this succession of structural events is about 19 km which is compatible with seismic data the proposed model explains the existence of downward facing synformal anticlines as folded basement cored tectonic wedges although they resemble parts of fold nappes these folded tectonic wedges do not necessarily imply large amounts of crustal shortening

magnetotelluric and teleseismic study across the snowbird tectonic zone canadian shield a neoarchean mantle suture 1 the snowbird tectonic zone stz is a fundamental boundary within canada s western churchill province one of the world s largest yet poorly known fragments of archean crust geophysical data from a collocated magnetotelluric and teleseismic transect across the northeastern segment of the stz provide an image of its subsurface geometry and indicate that it may have been previously mislocated the model suggests that 1 the stz has played a major role in the neoarchean assembly and paleoproterozoic reworking of the western canadian shield 2 it was reactivated in a manner comparable to other crustal scale features such as the kapuskasing zone of the superior province canada and the redbank thrust of the arunta block central australia and 3 it juxtaposes mantle blocks with contrasting geophysical properties revealing a lithosphere scale overlap of the leading edges of the rae and hearne domains the stz thus records plate interactions in the neoarchean comparable in scale with that of modern orogenic belts