oxygen diffusion in amphiboles the kinetics of oxygen isotope self diffusion in natural samples of hornblende tremolite and richterite have been measured samples were run under hydrothermal conditions using 18o enriched water profiles of 18o 16o 18o vs depth into the crystal were obtained using an ion microprobe the depths of sputtered holes were measured using an optical interferometer at 1000 bars 100 mpa water pressure the activation energies q and pre exponential factors d0 for diffusion parallel to c are d0 cm2 sec q kcal gm atom t c hornblende 1 20 1 10 741 6 650 800 tremolite 2 30 2 10 8 39 5 650 800 richterite 3 5 2 10 4 57 2 650 800 the diffusion coefficient d for hornblende at 800 c and 1000 bars water pressure measured parallel to the c crystallographic direction is at least ten times greater than that parallel to the a or b directions an increase in water pressure from 200 to 2000 bars increases d by a factor of 2 7 for diffusion parallel to c at 800 c the d value for hornblende at 800 c is about 0 01 that for quartz and 0 001 that for anorthite as a result closure temperatures for oxygen exchange in natural primary amphiboles are significantly higher than for quartz or feldspars it is unlikely that amphiboles will exchange oxygen isotopes by diffusion under most crustal conditions

plant fossil distributions in some australian permian non marine sediments abstract plant remains occur in all post devonian lowland terrestrial depositional systems with distinctive assemblages characterizing discrete environments glossopterid gymnosperms dominate most australian permian coal bearing sediments herbaceous pteridophytes sphenophytes and lycophytes are best represented in lower deltaic lacustrine and paludal deposits non glossopterid gymnosperms mostly colonized drier floodplain and upland environments and are poorly represented in australian permian sequences fresh and brackish water algae are abundantly preserved in paludal and lacustrine facies in both alluvial and delta plain environments seasonal productivity and taphonomic factors undoubtedly influenced the composition of interseam compression impression floras but integration of information from these assemblages with that from permineralized peats in situ coalified plants and coal maceral and palynological analyses can assist in the interpretation of australian permian coal forming environments and the structure of plant communities

some late eocene depositional environments of the coal bearing puget group of western washington state u s a abstract plant bearing sediments of the puget group in the area of detailed study accumulated in large flood basins cutoff meanders and along channel margins in point bars and crevasse splay settings in addition to the plant bearing deposits peat swamp deposits and coarse grained channel deposits are represented by stacked sandstone bodies and thick coal sequences the depositional environments of the fluvial deltaic deposits are distinguished by the presence and distribution of sedimentary structures grain size grain size variability and the densityand layering of organic remains both plant and invertebrate the importance of organic matter distribution in the sediments to differentiation of subenvironments was unexpected and may prove to be a valuable sedimentary characteristics in depositional interpretations within a single basin the sedimentary characterization of environments was made exclusive of the taxonomic composition of the plants preserved and is presented here without paleobotanical interpretation the separation of depositional interpretation from taxonomic identity of the fossil plants allows an independent assessment of the paleoecology of the plants preserved two prominent coal depositional models are discussed and evaluated in light of these data from the puget group it is concluded that peat accumulation in this system can be attributed most easily to a domed peat swamp model

oxygen diffusion in quartz diffusional oxygen exchange between quartz and water was studied by determining 18o profiles in the quartz using an ion microprobe inverse error function plots of the data are linear as required for a diffusion mechanism one natural and two synthetic samples were used and although they had different impurity concentrations oh na and al per 106 si atoms are 7 4000 35 835 and 67 127 respectively the d values were the same within experimental uncertainty diffusion parallel to c is about 2 orders of magnitude faster than that normal to c at 700 c and diffusion normal to the rhombohedron is intermediate the data indicate a change in slope on an arrhenius plot at the boundary at 100 mpa 1 kbar water pressure the preexponential factors do in square centimeters per second and activation energies q in kilojoules per mole for quartz 500 550 c are as follows do 190 and q 284 parallel to c and do 8 10 2 and q 238 normal to the rhombohedron for quartz 600 800 c do 4 10 7 and q 142 parallel to c do 9 10 7 and q 155 normal to the rhombohedron and do 1 10 4 and q 234 normal to c d increases with ph 2 o and between 25 and 350 mpa log d versus log h 2 o has a slope of approximately 1 1 these d values are all several orders of magnitude larger than previously reported values for oxygen diffusion in water free systems

environmental influence on maturity parameters in carboniferous coals of the netherlands abstract an upper carboniferous coal sequence has been analysed by means of organic petrological sedimentological and statistical methods in order to test the hypothesis of environmental influence on vitrinite reflectance values differences between the linear regression value and the vitrinite reflectance value along the depth profile have been taken as a measure of reflectance variation detailed maceral analyses have been carried out on forty seven coal seams factor analyses of selected variables resulted in the recognition of common factors accounting for approximately 50 of the variation of the data matrix two factor analyses were performed including either maturity parameters t max and r r or variation in vitrinite reflectance in both analyses two factors were considered sufficient to represent the data the factors have been attributed to coalification degree of humification and oxidation clustering on the basis of detailed maceral analyses resulted in a two fold subdivision of the coal seams the two clusters are differentiated on the basis of the ratio of the vitrinite macerals telocollinite and desmocollinite significant differences in hydrogen index and marked differences in mean vitrinite reflectance values the subdivision is related to differences in depositional environment one cluster interpreted to represent peat formation in a fluviatile influenced environment accommodates samples with significantly lowered reflectance values the other cluster is characterized by a deltaic setting of the coal seams petrographic and chemical differences are interpreted to be related to different levels of biochemical degradation in these two palaeo environments the fluviatile influenced coals have a marked lower maturity trend compared to those formed under deltaic conditions

analysis of experimental data on divalent cation diffusion kinetics in aluminosilicate garnets with application to timescales of peak barrovian metamorphism scotland we present a new statistical framework to analyze the diffusion data for divalent cations fe mg mn and ca in aluminosilicate garnet using published experimental data and an arrhenius relationship that accounts for dependence on temperature pressure garnet unit cell dimension and oxygen fugacity the regression is based on bayesian statistics and is implemented by the markov chain monte carlo approach all reported experimental uncertainties are incorporated and the data are weighted by the precision of the experimental conditions we also include a new term the inter experiment bias to compensate for possible inconsistencies among experiments and to represent any experimental variability not explicitly presented in the arrhenius relationship e g water content defect density at high temperatures where most experiments were conducted the diffusion coefficients calculated with the new parameters agree well with previous diffusion models e g chakraborty and ganguly in contrib mineral petrol 111 74 86 1992 carlson in am mineral 91 1 11 2006 however the down temperature extrapolation leads to notable differences at lower temperatures for common petrological applications for example at 600 c the diffusion coefficients of fe and mn are one half to one order of magnitude faster and the diffusion coefficient of ca is about one order of magnitude slower than calculated with parameters in carlson 2006 our statistical analysis also provides well defined uncertainty bounds for timescale estimates based on garnet diffusion profiles application of the newly derived coefficients indicates that the timescale of the thermal peak of barrovian metamorphism dalradian belt of scotland is about four to seven times longer than that estimated using previously published diffusion coefficients the peak is still geologically brief however of the order of 106 years 0 75 myr 0 70 0 36 myr 1 this brevity requires pulsed advective heat input as provided by syn orogenic mafic magmatism in these rocks

a flow law for dislocation creep of quartz aggregates determined with the molten salt cell we have used the molten salt cell to conduct an experimental study on the rheology of a natural quartzite containing 0 15 wt water co axial deformation experiments were conducted at constant piston displacement rates approximating constant strain rates at low strain the strengths of our natural quartzite measured in the molten salt cell are approximately half those measured at the same conditions in solid media because unlike solid confining media molten salt does not contribute to the strength of the sample it reduces the friction on the moving piston and it allows clear identification of the hit point we have limited the experimental conditions to those required for dislocation creep and have used only steady state flow stresses measured during climb accommodated dislocation creep to calculate the flow law parameters two flow laws were determined one for samples containing minor amounts of melt 1 2 and one for melt free samples in both cases the power law stress exponent n is 4 0 0 9 which is greater than that previously reported in flow laws for dislocation creep of quartz aggregates determined in solid media the activation energy q is 137 34 kj mol 1 for samples with melt and 223 56 kj mol 1 for those without within the range of previously determined values for quartz aggregates containing 0 1 wt water the pre exponential term a is 1 1 10 4 2 mpa ns 1 for samples without melt and 1 8 10 8 2 mpa ns 1 for those with melt the lower strengths measured in the molten salt cell indicate that previous piezometer relations for quartz experimentally determined in solid media are not correct extrapolation of the flow law for melt free aggregates to natural strain rates predicts higher strengths than most previous quartz flow laws however accurate extrapolation requires determining the dependence of flow stress on fh2o and or ah

coal depositional models and the distinction between alluvial and delta plain environments abstract the distinction between coal bearing upper and lower delta plain deposits in the rock record may be based on the presence or absence of features indicative of basinal influence and on the geometry of coal seams discriminating between alluvial plain and upper delta plain sequences is more difficult but is considered possible on coal seam geometry and coal seam splitting patterns other features such as the cross sectional shape of channel deposits may also be useful

deltaic coals of ferron sandstone member of mancos shale predictive model for cretaceous coal bearing strata of western interior the upper cretaceous ferron sandstone member of the mancos shale the coal bearing unit of the emery coalfield in central utah shows accumulation of clastic sediments in a lobate river dominated deltaic system that existed along the western shoreline of the interior cretaceous seaway during late turonian time five cycles of deltaic sedimentation each containing one major coal bed or coal zone are represented a clear genetic relationship exists between the geometries of the major coal beds of the emery field and the geometries of the delta front sandstone units with which they are associated the thicker part of each coal bed extends from the vicinity of the landward pinch out of the associated delta front sandstone landward to a distance of about 10 km this genetic relation forms the basis of a predictive model that can be used in designing more cost effective exploration programs in coal bearing strata of cretaceous age in the western interior

the rate of water penetration in experimentally deformed quartzite implications for hydrolytic weakening abstract in order to determine the rate at which water penetrates the grains of a quartzite we performed several types of experiments including water added deformation and hydrostatic experiments on vacuum dried samples and hydrostatic annealing experiments on previously deformed quartzites samples of heavitree quartzite with an average grain size of 200 m and intragranular water concentration of 1750 420 h 10 6 si as measured by ftir were vacuum dried at 800 c 6 pa for 12 h after vacuum drying the grains showed thermal cracks with an average spacing of 50 m and an intragranular water concentration of 240 60 h 10 6 si one constraint on the rate of water penetration into quartz was obtained by deforming vacuum dried samples with 0 3 wt 20 000 h 10 6 si water added at 800 c 1500 mpa and a strain rate of 10 6 s conditions at which as is quartzite undergoes climb accommodated dislocation creep the time between reaching experimental conditions and yielding of the sample was between 2 and 9 h the samples had yield stresses of 100 250 mpa values well below the yield stress of 1500 mpa for a vacuum dried sample deformation of the grains was homogeneous on both optical and tem scales indicating that the grains had fully equilibrated with the water related defect that is responsible for water weakening ftir measurements are consistent with this interpretation one of the deformed samples has an intragranular water concentration of 820 160 h 10 6 si and vacuum dried samples hydrostatically annealed for 3 or 10 h at the same conditions as the deformed samples have an average intragranular water concentration of 730 180 h 10 6 si to obtain a second constraint on the rate of water penetration hydrothermal annealing experiments were performed on portions of a sample of heavitree quartzite which were previously deformed without water added at 700 c 1200 mpa and 10 5 s and have a high 10 16 m 2 and homogeneous dislocation density two samples were annealed at 700 c 1500 mpa for 24 h one with 0 2 wt water and one with no water added the grains in the water added sample have a rim approximately 15 m wide with dislocation recovery microstructures indicating equilibration with the water related defect the sample with no water added has a homogeneous dislocation density throughout the grains which is similar to that of the original deformed sample the 15 m wide recovered rim suggests a penetration rate approximately an order of magnitude faster than the rate of oxygen diffusion under hydrothermal conditions the observed rate of penetration of the water related species is consistent with theoretical considerations and calculations which predict a diffusion rate for h 2 o that is an order of magnitude faster than the rate of hydrothermal oxygen diffusion we infer from our experiments that the rate of water penetration into quartz is consistent with diffusion of h 2 o

propagation of acoustic waves in a visco elastic two phase system influences of the liquid viscosity and the internal diffusion abstract the main purpose of the present paper is to present the mathematical expression for the frequency dependent effective acoustic properties of a liquid bubble mixture effects of the bubble resonance the heat and mass transfer between the liquid and bubbles and the viscoelasticity of the liquid are included in the expression several characteristic frequencies associated with these internal processes are represented by simple functions of the material and condition parameters using these expressions the acoustic properties of bubbly magmas are calculated and analyzed it is shown that the dispersion and attenuation of the pressure wave are particularly considerable in the frequency range lower than the characteristic frequency of the mass transfer and in the range near the characteristic frequency of the viscous response of the bubble radius in the frequency range bounded by these two frequencies the bubbly magma can be regarded as an elastic medium with the slow sound speed the significance of such acoustic properties on resonance of a body of bubbly magma is demonstrated in a simple one dimensional system

quantifying the seismicity on taiwan summary we quantify the seismicity on the island of taiwan using the frequency magnitude statistics of earthquakes since 1900 a break in gutenberg richter scaling for large earthquakes in global seismicity has been observed this break is also observed in our taiwan study the seismic data from the central weather bureau seismic network are in good agreement with the gutenberg richter relation taking b 1 when m 8 earthquake in the study region about every 25 yr however our analysis shows a lower frequency of occurrence of large earthquakes so that the expected frequency of m 8 earthquakes is about 200 yr the level of seismicity for smaller earthquakes on taiwan is about 12 times greater than in southern california and the possibility of a m 9 earthquake north or south of taiwan cannot be ruled out in light of the fukushima japan nuclear disaster we also discuss the implications of our study for the three operating nuclear power plants on the coast of taiwan

oxygen self diffusion in quartz under hydrothermal conditions oxygen self diffusion dox has been monitored in single crystal quartz in the temperature range 515 850 c under hydrothermal conditions in the beta field between 700 and 850 c the data are represented by two linear arrhenius relations for transport parallel and perpendicular to c values for do m2 s 1 are 2 09 10 11 parallel to c and 3 16 10 10 perpendicular to 101 0 values for h kj mol 1 are 138 54 parallel to c and 203 72 perpendicular to 101 0 at 700 c in the total pressure range 11 5 100 mpa dox is independent of water f h2o and oxygen f o2 fugacities between the ni nio and fe3o4 fe2o3 buffers the results are consistent with diffusion via a simple charged vacancy mechanism under an extrinsic point defect regime further experiments are required to confirm the nature of the mobile oxygen defect a key aspect of the results is the observation that at the low water fugacities of the present experiments a hydrogen containing defect appears to play no role in the oxygen transport mechanism this is in contrast to other published sets of data and leads directly to the requirement for detailed interlaboratory comparisons

ion microprobe studies of water in silicate melts concentration dependent water diffusion in obsidian abstract the temperature dependence of water diffusivity in rhyolite melts over the range 650 950 c and pt h2o 700 bars is evaluated from water concentration distance profiles measured in glass with an ion microprobe diffusivities are exponentially dependent on concentration over this temperature range and vary from about 10 8 cm2 s at 650 c to about 10 7 cm2 s at 950 c at 2 wt water water solubility also varies with temperature at a rate of 0 14 wt per 100 c increase the avtivation energy ea appears to be constant at 19 1kal mole for 1 2 and 3 wt h2o comparison of these data with results for cation diffusion indicates that this value is a minimum ea for diffusion of any species in a rhyolite melt compensation plots of log10d0 the frequency factor versus ea indicate that hydrous rhyolite melts follow the same trend as anhydrous basalts d0 increases for h2o and ca2 1 as ea decreases this suggests that these molecules may diffuse by different mechanisms than do monovalent cations and that hydration of the melt affects diffusion of ca2 and h2o differently than it does monovalent cation diffusion the results imply that dramatic increases in cation diffusivities by hydration 1 may occur with additions of less than 1 wt h2o

diffusion of a multi species component and its role in oxygen and water transport in silicates an important but poorly understood factor that affects diffusion rates is the role of speciation during diffusion of a multi species component the diffusion of such a component is complicated by the different diffusion coefficient of each species and the interconversion reactions among the species these complexities can be treated by a diffusion equation that incorporates the diffusive fluxes of all species contributing to the concentration of the component the effects of speciation on the diffusion of the component can be investigated experimentally in some simple cases by measuring concentration profiles of all species developed during diffusion experiments or by studying some of their other consequences experimental data on water diffusion in rhyolitic glasses indicate that although dissolved water is present as two species h 2o molecules and oh groups molecular h 2o is the dominant diffusing species at very low to high water concentrations this explains the apparently complex behavior of water diffusion experimental data on oxygen diffusion in some silicates using 18 o tracers in the form of h 2 18 o are consistent with the idea that 18 o transport is dominated by diffusion of h 2o molecules even at lower water contents ppm or less this explains why oxygen transport depends on the presence of water and generally depends on water fugacity linearly for this mode of oxygen transport there is a simple theoretical relationship between the effective total oxygen diffusion coefficient and the total water diffusion coefficient that is a function of only the water concentration of the silicate at low water content this relationship appears to describe quantitatively the existing data over a wide range in water contents and diffusion coefficients in several phases

facies and genesis of carboniferous coal seams of northwest germany abstract in order to get detailed information about the facies and genesis of upper carboniferous coal seams of northwest germany maceral analyses of complete seam profiles westphalian b d mainly westphalian c were carried out four main facies and twelve subfacies could be distinguished the main facies are 1 1 the sapropelic coal facies consisting of fine grained inertinite and liptinite which forms from organic sediments deposited at the bottom of moor lakes 2 2 the densosporinite facies which is high in inertinite and liptinite and low in vitrinite syngenetic pyrites clastic layers thick vitrains and fusains do not occur this facies originates from peats of open mires with higher groundwater table and herbaceous vegetation the open mire was situated in the centre of extensive swamps consequently clastic sedimentation did not affect this swamp type and nutrient supply and ph values were low 3 3 the vitrinite fusinite facies which is high in vitrinite this is the result of abundant vitrains under the microscope fusains were mostly identified as fusinite the vitrinite fusinite facies originates from a forest mire more or less abundant seam splits and clastic layers show that rivers flowed in the neighbourhood of this area 4 4 the shaly coal facies which represents the most marginal part of the former swamp frequently affected by clastic sedimentation within the carboniferous of the ruhr region it seems unlikely that the thin coal seams of the namurian c and westphalian a1 contain a densosporinite facies the swamps were situated in the lower delta plain where they were often affected by marine influences consequently coals are high in minerals and sulfur and they are thin and discontinous the best conditions for the formation of extensive swamps with open mires densosporinite facies in their central parts prevailed during westphalian a2 and b1 times low contents of sulfur and minerals and high content of inertinite are typical for these coals sedimentation mainly took place in the transitional zone from the lower to the upper delta plain during the westphalian b2 and c fluvial sedimentation dominated within the coal seams minerals sulfur and pseudovitrinite increase while inertinite decreases this is the consequence of coal of the densosporinite facies occurring with increased rarity the coal seams of the westphalian c2 contain no densosporinite facies because peat formation was restricted by increasing fluvial sedimentation and by a better drainage as a consequence extensive swamps with open mires in the centre were no longer formed after the formation of the odin seams above the odin seams coal of the vitrinite fusinite facies contains thick walled torisporinites variations and lowering of the groundwater table caused mild oxidative influences during peat formation this is documented by an increase in pseudovitrinite the occurrence of torisporinites and the absence of spheroidal sideritic concretions sulfur content increases in the absence of the low ash and low sulfur coal of the densosporinite facies in upper carboniferous coal seams of the ibbenburen region the inertinite and telocollinite contents are higher than in those of the ruhr region therefore variations of the groundwater table have been more pronounced and resulting oxidative influences must have been more severe seldom occurring marine and brackish horizons and a higher fusinite fusain content indicate a slight elevation of this area from early westphalian d times onward peat formation was no longer possible because of the better drainage this resulted in severe oxidative conditions which excluded peat formation

delta plain coal deposits from the than formation of the early cretaceous saurashtra basin gujarat western india abstract the than formation of the early cretaceous saurashtra basin consists of an interbedded assemblage of sandstone claystone carbonaceous shale and coal facies small scale crossbedded and laminated mudstone siltstone sr lm facies are considered to have formed by down current migration of small scale subaqueous bedforms and overbank deposits of distributary channels the planar and trough crossbedded sandstone lithofacies sp st formed by migration of sand dunes and transverse bars in distributary channels laminated to ripple laminated siltstone f1 facies with or without coaly stringers alternate with fine clastics are suggestive of flood deposits and abandoned interchannel plain of delta distributaries the muddy carbonaceous shale fm facies represents deposition largely in low lying interchannel plains and backswamps peat coal pc facies are interpreted as in situ deposits in quiet water conditions of sedimentation across a lake the integrated results of lithofacies texture and palaeocurrent analysis suggest that than strata were deposited in a prograding major delta distributary complex in lower and upper delta plain environments

evolving fluvial style in the kekiktuk formation mississippian endicott field area alaska base level response to contemporaneous tectonism the hydrocarbon reservoir at endicott field offshore from the sagavanirktok delta in northeastern alaska is found in the upper mississippian visean kekiktuk formation the trap is bounded by the northwest southeast trending tigvariak and mikkelson bay faults and the younger east west trending niakuk fault the kekiktuk comprises sandstones siltstones and mudstones with locally significant coals and conglomerates and is subdivided into three major reservoir zones based on the relative dominance of these lithologies zone 1 the lowest comprises mudstones siltstones and coals with subordinate isolated sandstones and represents deposition within a low lying swamp plain with very low net to gross ratio this zone is considered to be effectively nonreservoir major movement on the mikkelson bay and tigvariak faults created a half graben with uplift to the north and east and a very significant drop in base level this change resulted in fairly widespread deposition of zone 2 medium to coarse grained sandstones from sandy bed load braided streams however those sandstones thin significantly to the west away from the faults continuing tectonism at this time created local shifts in base level manifest as diversion of streams widespread abandonment and subsidence leading to the creation of a arge lake the lacustrine deposits are widespread and effectively divide zone 2 into two subzones those subzones are mappable sheet sandstones and constitute the best reservoir at endicott field in terms of net to gross ratio porosity permeability and sandstone connectivity base level shows evidence of rising dramatically at the end of zone 2 this rise is attributed to continuing tectonism within the basin and is particularly associated with the east west trending mid field fault system at endicott field as well as ongoing activity on the tigvariak mikkelson bay fault system thus at the base of zone 3 subzone 3a in the southern and eastern parts of the field the rocks are mudstones and widespread coals and contain at least one unequivocally marine mudstone these rocks are lower delta plain interdistributary bay fill deposits with rare distributary channel sandstones north and west of the mid field fault system the marine mudstone is absent and the facies changes significantly with the loss of dominant coal and a concomitant increase of dist ibutary channel sandstones reservoir properties of subzone 3a including connectivity are significantly different in this area subzone 3b is a thick accumulation of fine grained alluvial overbank deposits within which occur rare isolated anastomosed channel sandstones of limited connectivity this subzone makes minimal contribution to endicott field reserves subzone 3c is characterized particularly in its upper part by well developed fining upward cycles indicating mature meandering streams the relationships between these two highest subzones of the kekiktuk at endicott field indicate they represent an aggradational episode initiated by tectonically induced avulsion and set against a background of rising base level to the west at some distance from the tigvariak mikkelson bay f ult system zone 3 is much thinner than at endicott field and is dominated by mudstones and coals this evidence emphasizes the control that contemporaneous tectonism related to those faults had on sediment especially sandstone distribution within the kekiktuk formation base level changes can be identified within the end page 1723 kekiktuk formation in the north slope subsurface by careful lithofacies analysis and an awareness of key constraining indicators such as are revealed by palynology paleontology and structural geology by analogy with shallow marine rocks sequence stratigraphic concepts may be extended to continental successions however one must approach such problems with a full awareness of the impact of tectonism on base level and basin development

sedimentary environment dynamics and the formation of coal in the pennsylvanian variscan foreland in the ruhr basin germany western europe during the pennsylvanian formation of coal was a phenomenon that was spread over many continents it is the aim of this paper to illustrate factors that led to the formation of coal seams in paralic clastic sedimentary environments in the ruhr basin german variscan foreland during the pennsylvanian in terms of sequence stratigraphy and the structural evolution of the basin lithostratigraphic sections from exploration wells in the currently explored zone of the coal basin allowed the generation of volumetric lithofacies models using geostastical methods these models support the analysis of sedimentary facies and a sequence stratigraphic interpretation of the successions that are widely correlated throughout the basin we then evaluate the relation of the sequence stratigraphic elements derived from the facies models with the abundance of coal seams

depositional environment of the lower cretaceous upper albian winton formation at isisford central west queensland australia inferred from sandstone concretions abstract numerous vertebrate and plant fossils have been found in ex situ sandstone concretions near isisford in central west queensland since the mid 1990s these concretions are found in the lower cretaceous portion upper albian 100 5 102 2 ma of the winton formation the lower most winton formation is thought to have formed in a fluvial channel or flood basin setting proximal to the eromanga sea but due to the scarcity of good exposures the local depositional environment at isisford has not been ascertained minimal compression of vertebrate and plant fossils a lack of grain suturing predominantly cement supported fabric and fractures running through calcite cement as well as fossil bone and framework grains indicates that concretions formed during early diagenesis pre compactional or syndepositional calcite stable isotope 18ovpdb values range from 12 25 to 4 indicating mixed marine and meteoric pore waters and 13cvpdb values range from 5 3 to 4 1 indicative of both sulfate reduction and methanogenesis of organic material including decaying vertebrate soft tissues in the burial environment the mixed marine and freshwater signature suggests a marginal marine setting possibly deltaic or estuarine connected to the regressive epicontinental eromanga seaway at around 102 100 ma this is not inconsistent with the lithology from nearby cores coupled with isisford fossil vertebrate ecology personal observation our research demonstrates the utility of investigating ex situ concretions to refine paleoenvironments at localities where little or no outcrop is available and traditional facies analysis is impractical

quantification of lower crustal synmetamorphic fluid fluxes in the kapuskasing structural zone based on oxygen isotope profiles across two paragneiss mafic gneiss contacts detailed oxygen isotope profiles were measured across two very similar amphibolite grade paragneiss mafic gneiss contacts located 2 km apart within the kapuskasing structural zone the first profile is asymmetrical about die contact 18 o values for whole rocks and minerals are homogeneous in the paragneiss whole rock 18 o 10 4 to 11 4 smoothly decrease by about 2 over 2 5 m moving into the mafic gneiss and are homogeneous in the remainder of the mafic gneiss whole rock 18 o 7 0 to 7 4 the second profile is flat with homogeneous whole rock and mineral 18 o values in bom lithologies and mafic gneiss values whole rock 18 o 8 7 to 9 8 that are higher by about 3 relative to typical mafic gneiss values mineral mineral isotopic fractioations are fairly constant in all samples and are typical of high grade metamorphic rocks despite their differences both profiles can be explained by the advection of a mixed h 2 o co 2 fluid in equilibrium with the paragneiss across the contact into the mafic gneiss coupled with diffusion of oxygen in the fluid modeling constrains the net fluid flux required to form me first profile to be 1 3 m 3 m 2 and for me second profile to be 10 m 3 m 2 thus the net fluid flux during metamorphism varied probably by at least a factor of five over 2 km these fluxes could have been generated locally within the kapuskasing structural zone during metamorphism either by metamorphic devolatilization reactions or by the release of volatiles from crystallizing magmas

origin of large scale crossbeds in the late permian coal measures of the sydney and bowen basins eastern australia abstract theories proposed for the origin of large scale crossbeds may be generalised into two main categories the first suggests the large sigmoidal shape of the sediment layers results from variable differential compaction during and after deposition whereas the second infers that the high angle of the crossbeds is the result of primary depositional processes britten 1983 has proposed that large scale inclined strata may be produced according to his cide model whilst mallett 1983 has suggested that such structures are produced by channel automigration parbury 1976 and conaghan 1981 both proponents of the primary depositional model interpret the large scale inclined strata as foreset beds of a gilbert type delta prograding into deep 50 m water depth lakes within which floating islands produce allochthonous deposits from hydroponic vegetation marchioni 1976 1982 however envisages that the large scale inclined strata are epsilon crossbeds which have tilted during differential subsidence of peat swamps over which active channel systems have encroached nine kilometers of almost continuous high wall exposures have been studied in the moura kianga coal mine of the southeastern bowen basin and it is concluded that none of the above mentioned processes can explain the present configuration of sedimentary layering observed in these high walls at the moura kianga coal mine it is proposed that there the high angle large scale inclined strata have originated as primary features associated with a crevasse sub delta subsidence in excess of vegetation accumulation within the peat swamp provides the mechanism whereby a shallow lake developed and into which a crevasse sub delta was deposited similar processes have been described by coleman and prior 1980 from the mississippi delta

simple kinetic models of petroleum formation part i oil and gas generation from kerogen modern basin analysis uses kinetic models to predict the extent of petroleum generation within potential source rocks the global kinetic model presented here assigns kinetic parameters based on gross depositional environment and stratigraphic age this is useful in areas of low geochemical knowledge including exploration frontiers five kerogen kinetic organofacies each characterized by a specific organic matter input and early diagenetic overprint can broadly be related to sedimentary facies age associations even using seismic sequence stratigraphy alone a aquatic marine siliceous or carbonate evaporite any age b aquatic marine siliciclastic any age c aquatic non marine lacustrine phanerozoic d e terrigenous non marine ever wet coastal mesozoic and younger and f terrigenous non marine coastal late palaeozoic and younger routine pyrolysis data allow partitioning of organic carbon in the immature source rock into four initial components oil oil generative gas generative and inert separate kinetic parameters for the oil and gas generative fractions allow computation of the evolving concentration and composition of the products it was assumed that the activation energy distributions for each fraction were normally distributed non linear regression of large combined laboratory and field data sets varying by up to 12 orders of magnitude in heating rate established optimum values for the required ten 5 2 kinetic parameter sets a emean e differences in kinetic parameters can be reconciled with known chemical properties although our knowledge base is still inadequate to construct kinetic models from first principles mean activation energies governing oil generation increase systematically in the order a f causing a corresponding increase in generation temperature at a reference heating rate 2 c ma 1 the oil generation window 10 90 oil generative kerogen degraded increases from ca 95 135 c to 145 175 c organofacies c has the tightest energy distribution and narrowest oil generation window the gas generation window ranges from ca 105 155 c to 175 220 c thermal stress results from a combination of temperature and time an order of magnitude increase decrease in heating rate elevates depresses reaction temperatures by ca 15 c heating rates in subsiding sedimentary basins can vary by two orders of magnitude dramatic differences in generation temperature can result if the heating rate and organofacies effects compound thus global oil and gas generation temperature thresholds constitute blunt instruments with which to screen the petroleum potential of sedimentary basins because unexpelled oil provides a potential feedstock for oil to gas cracking in the source rock quantitative models of petroleum generation become really useful only when coupled with models of oil gas cracking and expulsion for example the frequently observed association between gas provinces and coals cannot be explained solely by their generation behaviour

interpreting complex fluvial channel and barform architecture carboniferous central pennine province northern england the bashkirian lower brimham grit of north yorkshire england is a fluvio deltaic sandstone succession that crops out as a complex series of pinnacles the three dimensional arrangement of which allows high resolution architectural analysis of genetically related lithofacies assemblages combined analysis of sedimentary graphic log profiles architectural panels and palaeocurrent data have enabled three dimensional geometrical relationships to be established for a suite of architectural elements so as to develop a comprehensive depositional model small scale observations of facies have been related to larger scale architectural elements to facilitate interpretation of the palaeoenvironment of deposition to a level of detail that has rarely been attempted previously thereby allowing interpretation of formative processes detailed architectural panels form the basis of a semi quantitative technique for recording the variety and complexity of the sedimentary lithofacies present their association within recognizable architectural elements and thus the inferred spatio temporal relationship of neighbouring elements fluvial channel fill elements bounded by erosional surfaces are characterized internally by a hierarchy of sets and cosets with subtly varying compositions textures and structures simple cross bedded sets represent in channel migration of isolated mesoforms dunes cosets of both trough and planar tabular cross bedded facies represent lateral accreting and downstream accreting macroforms bars characterized by highly variable yet predictable patterns of palaeocurrent indicators relationships between sandstone dominated strata bounded by third order and fifth order surfaces which represent in channel bar deposits and incised channel bases respectively chronicle the origin of the preserved succession in response to autocyclic barform development and abandonment major episodes of incision probably influenced by episodic tectonic subsidence differential tilting and fluvial incision associated with slip on the nearby north craven fault system overall the succession represents the preserved product of an upper delta plain system that was traversed by a migratory fluvial braid belt system comprising a poorly confined network of fluvial channels developed between major sandy barforms that evolved via combined lateral accretion and downstream accretion

interpretation of vitrinite reflectance depth profiles in the northern denison trough bowen basin australia abstract the denison trough bowen basin australia is a mature hydrocarbon province that contains permian to triassic coal and gas bearing sediments deposited in deltaic to shallow marine shelf conditions the sandstone reservoirs of the permian aldebaran sandstone freitag formation and catherine sandstone of the northern denison trough ndt were evaluated for their co2 storage potential as part of the queensland government s zerogen co2 capture and storage project which found that diagenetic processes acting on the sandstones have resulted in poor permeability and reduced porosity making them unsuitable for large scale injection and storage in this area to better understand the factors acting to degrade these reservoirs the purpose of the current study was to establish a thermal maturity framework for the permian sandstone reservoirs of the northern denison trough based on vitrinite reflectance measurements of coals and rock eval analysis of coals and shales from the aldebaran sandstone through to the catherine sandstone mean maximum vitrinite reflectance of coals rmax ranges from 0 55 to 0 93 and estimated maximum burial temperatures calculated from vitrinite reflectance fall between 83 oc 125 oc calculation of palaeotemperatures from vitrinite reflectance data has been hampered by inversions of depth reflectance profiles at the top of the aldebaran sandstone and scatter in vitrinite reflectance data this has been attributed to depositional effects including the major marine flooding surfaces at the top of the aldebaran sandstone that have affected vitrinite reflectance evolution in the ndt producing low reflecting fluorescing perhydrous vitrinite near marine flooding surfaces and subhydrous vitrinite when oxidising conditions prevailed a vitrinite reflectance difference of up to 0 2 rmax is detected in an isometamorphic coal an equivalent palaeotemperature difference of approximately 19 oc the abundance of perhydrous vitrinite has resulted in largely suppressed vitrinite reflectance throughout the examined permian interval in the northern denison trough and the presence of both perhydrous and subhydrous vitrinite introduces an error in palaeotemperature calculation in high volatile bituminous coals rock eval analysis provides supporting and calibrating maturity data tmax over the studied interval ranges from 421 oc to 447 oc generating a positive broadly linear correlation between rmax and tmax that is applicable specifically to the ndt tmax suppression was also detected in perhydrous coals hydrogen index serves to evaluate the level of vitrinite reflectance suppression through an inverse relationship between the two parameters the rock eval data confirms the oil generation potential of coals in the ndt while shales associated with the same stratigraphic intervals have lower hydrocarbon generation potential this study brings new insights into the thermal maturity framework in the ndt and highlights the importance of reliable vitrinite reflectance data for calculation of maximum burial temperatures particularly in underexplored or frontier areas

peat marl deposition in a holocene paludal lacustrine basin sucker lake michigan exceptionally thick over 15 m deposits of peat which fill the northern end of sucker lake basin in northcentral michigan document the volumetric importance of allochthonous organic material in a modern coal forming environment organic debris that originates in and is derived from a highly vegetated floodplain immediately upstream is deposited as a lakeward prograding lobe that exhibits features typical of most lacustrine gilbert deltas but is composed almost entirely of organic material this system overlies an additional 7 m of nearly pure brecciated lacustrine carbonate deposited as shallow lake margin benches and emplaced into the deep basin centre by gravity sliding prior to deltaic progradation in the southern end of the basin bottomset beds of fine silt size organic phytoclasts onlap distal facies of progradational bench carbonates which originate in shallow water through calcite encrustation about stems of the dominant macrophyte chara with continued sedimentation a stratigraphic succession in which allochthonous organics will overlie pure allochthonous lacustrine carbonates and in part be overlain by autochthonous carbonates will characterize the northern end of this holocene system in the southern end around the basin margins however autochthonous carbonates will entirely underlie allochthonous organics numerous continuous cores up to 22 m through these units document 1 the importance of sources of allochthonous organic debris in modern coal forming complexes 2 the genetic relationship between nearly pure calcareous and nearly pure carbonaceous facies within these paludal lacustrine settings and 3 the complexity of interrelationships between the several component facies within such continental sedimentary systems

oxygen self diffusion in calcite dependence on temperature and water fugacity oxygen self diffusion in natural calcite single crystals was studied hydrothermally at 400 800 c and 10 350 mpa confining pressure diffusion coefficients d were determined from18o concentration profiles measured with an ion microprobe at 100 mpa confining pressure the arrhenius parameters yield an activation energy q 173 6 kj mole and pre exponential factor d0 7 10 9 m2 s over the temperature range 400 800 c and there is no measurable anisotropy constant temperature experiments at 700 c indicate that there is a strong linear correlation slope 0 9 of d with water fugacity over the range 4 240 mpa consistent with the interpretation that in the presence of water the dominant oxygen bearing transport species in calcite is molecular water a sample containing 1180 ppm mn shows a marked increase in observed d values at temperatures below 600 c however when pre annealed at 700 c the d values obtained at 550 c are within a factor of four of the value obtained for the low 100 ppm mn sample the results of this study confirm that in contrast to carbon oxygen diffusion rates in calcite are greatly enhanced when water is present the difference in the effect of water on doxygen and dcarbon in calcite may provide valuable information for evaluating the role of fluids in the thermal histories of calcite bearing rocks

a survey of hydrous species and concentrations in igneous feldspars the hydrous components in 85 feldspars from various igneous environments spanning the range of naturally occurring compositions were examined with infrared spectroscopy the feldspars contain structural oh 0 512 ppm h 2o h 2o 0 1350 ppm h 2o and nh 4 0 1500 ppm nh 4 groups as well as fluid inclusions and alteration products although composition and structure do influence the type of hydrous species that can be incorporated into a particular feldspar mineral the concentration of these species is not controlled by major element composition coarse perthitic microclines have a heterogeneous distribution of hydrous species and contain h 2o or nh 4 in k rich lamellae and fluid inclusions in na rich areas the structural oh in plagioclase feldspars is not associated with twin boundaries or exsolution lamellae all of the possible structural hydrous species are found in pegmatite feldspars whereas volcanic feldspars contain only structural oh the variation in oh concentration within a given feldspar composition suggests that fluids in the geologic environment play a role in determining the hydrogen concentration of each sample the vast majority of plutonic feldspars have undergone partial or total equilibration with meteoric fluids during low temperature 400 150 c hydrothermal exchange obliterating any structural hydrogen and creating substantial concentrations of fluid inclusions up to 4000 ppm h 2o in the exchanged regions the amount of water stored as fluid inclusions within feldspars in the upper crust 1 10 19 kg is small compared to the 1 35 10 21 kg of water in the oceans but is roughly equivalent to the reservoir of water stored in hydrous minerals in the upper crust

the late triassic callide coal measures queensland australia coal petrology and depositional environment abstract the late triassic carnian rhaetian callide coal measures are preserved in a partly fault bounded basin remnant in east central queensland australia the sequence comprises up to 150 m of interbedded clastic sedimentary rocks and at least four major coal seams including one coal body up to 23 m thick the sequence was deposited initially in high gradient alluvial fan systems which gave way through time to sandy low sinuosity rivers the restricted intermontane and entirely alluvial nature of sediment accumulation is here considered to have influence the petrographic characteristics of callide coals and their external geometry the main coal seam from the callide measures shows variation in the predominance of some macerals indicating successions of environmental changes the application of transmission electron microscopy tem to the study of the callide coal has enabled a better understanding of the nature and origin of some of the less understood macerals such as micrinite and vitrinite b two forms of vitrinite have been observed each with a distinct reflectance range the wood sourced vitrinite a displays an average reflectance of 0 56 implying a higher rank than the 0 49 ro total vitrinite reflectance recorded in previous publications vitrinite b and a together represent the most commonly occurring macerals in the callide coal samples of the present study the lower reflecting vitrinite b which forms bands often several hundred m in thickness in tem shows sub micron electron transparent laminae of lipid rich material alternating with a more conventional vitrinite material the vitrinite b is interpreted to represent accumulations of leaves the callide coal has entered the oil window and oil has been generated from some exinite cutinite and resinite as evident from change in fluorescence and the presence of exsudatinite in cell cavities and cleats vitrinite b is seen under the microscope to also be generating oil micrinite the origin of which has been much debated occurs in selected horizons only as lenticular bodies suggesting cell filling or filling of spaces between laminations in vitrinite b tem shows micrinite to consist predominantly of sub micron pyrite and possibly other mineral particles adsorbed on humic acids

water diffusion in quartz at high pressure tectonic implications an indirect method based on the effect of water on plastic deformation mechanisms in quartz is used to estimate water diffusion penetration depths at high pressure diffusivities calculated by this method are orders of magnitude greater than those determined at low pressure and high pressure activation energy for water diffusion is three to five times greater than low pressure values this implies very temperature sensitive hydrolytic weakening at deep crustal and upper mantle depths potentially leading to a sharp mechanical decoupling of the lithosphere

the effect of depositional environment on coal distribution and quality parameters in a portion of the highveld coalfield south africa abstract eight successive lithofacies associations are identified and described they are each laterally continuous and represent a certain depositional phase throughout the study area these are related to sedimentary processes from which a three dimensional paleoenvironmental model is derived subsequently coal distribution and coal quality characteristics are linked to the depositional features of the model the identified depositional phasescommenced with subglacial glaciofluvial and glaciolacustrine settings with associated gilbert type deltas these are followed by meandering and minor braided fluvial settings characterized by laterally and vertically highly variable lithofacies in which the main coal bearing strata were formed coal distribution and quality parameters ash and volatile matter content calorific value are closely related to paleoenvironmental characteristics major changes of coal distribution and quality parameters are mainly associated with active and abandoned channels and these parameters are less variable in floodplain settings

relationships between o isotope equilibrium mineral alteration and rb sr chronometric validity in granitoids implications for determination of cooling rate a combined study of mineral o and rb sr isotopes was carried out for a number of mesozoic granitoids in china in order to compare the degree of o isotope equilibrium between coexisting minerals with the validity of mineral rb sr isochrons for granitoids a scrutiny of both o isotope geothermometry and rb sr internal isochron dating for corresponding minerals indicates that equilibrium o isotope fractionation between rb sr isochron minerals corresponds to geologically meaningful isochron ages if the variation in 87rb 86sr ratio is big enough to provide reasonably small uncertainties in age significant deviation of the rb sr isochron age from the actual age appears to depend on the difference in sr isotopic composition between an external fluid and the igneous minerals as a result o isotope disequilibrium is often caused by interaction between the rock and the external fluid that results in mineral alteration post magmatic alteration can cause isotope exchange between the minerals and an internally buffered fluid that is isotopically identical to the host rock the o isotope composition of coexisting minerals in studied samples changed principally due to a decrease in temperature both rb and sr concentrations and the sr isotope ratios of isochron minerals also changed due to the mixing of different sr reservoirs nevertheless the isochron age can remain unchanged if the mixing took place along the isochron chord between the internal fluid and the minerals from that newly altered minerals formed this provides an insight into the effect of internal and external fluids on the validity of mineral rb sr chronometry in addition an alternative approach is proposed to construct the cooling curve by a combined use of o isotope temperature and mineral isotope age for the granitoids of interest comparing with the traditional method using the empirical closure temperature for rb sr chronometry the proposed approach utilizes fewer variables with smaller uncertainties than the traditional way

seismic stratigraphy of a large cretaceous shelf margin delta complex offshore southern australia seismic images along australia s southern continental margin reveal the internal geometry and depositional history of the hammerhead delta a late cretaceous shelf margin delta complex in the ceduna subbasin of the bight basin the hammerhead delta comprises the late santonian to maastrichtian hammerhead supersequence which is divisible into three third order sequence sets and their component sequences sequence set 1 late santonian to early campanian comprises three progradational sequences deposited after a major fall in sea level under a high sediment supply regime sequence set 2 early campanian to early maastrichtian comprises two sandy progradational sequences basinward shifts in facies caused by forced regression are apparent between each progradational sequence sequence set 3 early to late maastrichtian is a thick aggradational succession deposited when the rates of creation of accommodation space and sediment supply were balanced a transgressive episode at the top of sequence set 3 marks a rapid decrease in sediment supply and the end of deltaic sedimentation a long lived sand rich sediment supply most likely derived from erosion of the eastern australian highlands to the northeast was the major influence on delta formation rapid progradation and the formation of thick shelf margin clinoforms resulted in slope instability growth faulting and load induced collapse of the shelf margin during the campanian the hammerhead delta is characterized by sandy progradational clinoforms and lacks the thick coeval prodeltaic shales and shale tectonism that are common to many other large deltas the results of this study which included seismic facies mapping well correlations and comparisons to other large shale poor deltas suggest that the hammerhead delta has excellent reservoir potential

cation diffusion in feldspars feldspars are among the most common minerals in the earth s crust and are found in a variety of rock types diffusion in feldspars has been studied for well over half a century with rosenqvist s 1949 measurements of ra and pb diffusion among the earliest published works major efforts in measuring diffusion in feldspars primarily of the alkali elements were undertaken in the early 1970s with the work of bailey 1971 lin and yund 1972 petrovic 1972 foland 1974 giletti et al 1974 and kasper 1975 many of these early studies used bulk exchange techniques rather than direct depth profiling or employed methods of limited depth resolution such as serial sectioning these methods while state of the art for their time impose several limitations including a range of measurement restricted to relatively fast diffusivities and the difficulty of distinguishing the effects on measured chemical or isotopic compositions that may be a result of diffusional fast paths surface reaction and or other artifacts from those contributions due solely to volume diffusion development of high resolution depth profiling techniques such as sims and rbs have permitted measurement of much smaller diffusivities for a broader range of elements and reduced some of the uncertainties characteristic of bulk exchange methods feldspar diffusion data have been previously summarized in yund 1983 and smith and brown 1988 and were included in brady s 1995 compilation of diffusion data for silicate minerals since the publication of these works there have been numerous diffusion studies of feldspars encompassing a range of compositions in alkali feldspars and across the plagioclase series these have included measurements of diffusion of major elements na k ca ba oxygen and silicon as well as na k and caal nasi interdiffusion diffusion of noble gases and diffusion of minor and trace elements including fe mg sr

rates and mechanisms of isotopic exchange background the proliferation of stable isotope laboratories in recent years has led to a marked increase in the routine use of stable isotope analyses in geochemical studies this trend is likely to continue because of the development of micro analytical techniques e g laser ablation ion microprobe femtomole carrier gas methods etc for stable isotope analysis and the potential of these techniques to reveal the detailed sequence of thermal and fluid histories preserved in the rock record see mckibben et al 1998 equilibrium isotope fractionation factors and rates of isotopic exchange form the cornerstones for the interpretation of stable isotope data from natural systems indeed determination of the distribution of the stable isotopes of c o h s in gases fluids and minerals has become a standard and extremely powerful approach in elucidating the temperatures material fluxes rock and fluid origins and time scales associated with ancient and active fluid rock interaction processes in the earth s crust see valley et al 1986 although the thermodynamic principles underlying isotopic fractionation behavior were developed more than fifty years ago by urey 1947 the calibration of fractionation factors has proven to be difficult during the last four decades a great deal of progress has been made in determining the equilibrium fractionations of 18o 16o d h 13c 12c and 34s 32s among fluid and mineral components at high temperatures 400 c both from experimental exchange studies theoretical calculations using vibrational spectra semi empirical calculations using bond type considerations and empirical calibrations based on natural assemblages see references in o neil 1986 kyser 1987 criss 1991 1999 chacko et al this volume of these the experimental method is the most direct because it involves the least number of a priori assumptions despite the utility of the equilibrium approach in quantifying the isotopic behavior in select water rock

solubility of hydroxyl in natural quartz annealed in water at 900 c and 1 5 gpa we have measured the infrared spectra of a natural quartz after annealing it for up to 37 hours in water at 900 1000 c and 1 0 1 5 gpa under chemical conditions buffered through a hydrogen membrane with an assemblage of water nickel metal and nickel oxide from integral absorbances in the 3400 and 2500 cm 1 regions we calculated the concentration of hydrogen and deuterium present in the samples as hydroxyl concentrations reported in this work are calibrated to the deuterium content of a sample annealed 37 hours in d2o18 as determined by nuclear reaction analysis hydrothermal annealing increased the hydroxyl content of natural quartz a 1 from 26 to 75 11 h 106si absorption increased by growth of o h bands it 3318 3483 and 3432 cm 1 associated with a13 samples annealed in d2o18 showed an increase in bands near 2500 cm 1 associated with o d and a13 an o h band in the starting material at 3485 cm 1 associated with li was absent from the spectra of annealed samples fractured samples were characterized by the appearance of a sharp band at 3580 cm 1 and absorption several times larger than unfractured samples microscopic examination of fractured samples showed that they contained water inclusions and healed fractures previous hydroxyl solubility measurements made on fractured samples may be too large due to hydroxyl contamination along fractures at 900 c experiments equilibrated in times consistent with a diffusivity for hydrogen impurity in quartz of 10 7 cm s

diffusion obstacles and opportunities in petrochronology many of the approaches in petrochronology are rooted in the assumption of equilibrium diffusion is an expression of disequilibrium the movement of mass in response to chemical potential gradients and isotopes in response to isotopic gradients it is extremely important that we be aware of how the effects of diffusion can place obstacles across our path towards petrochronologic enlightenment conversely the effects of diffusion also provide opportunities for understanding rates processes and conditions experienced by rocks the enormity of the field does not permit us to provide a comprehensive review of either the mathematics of diffusion or quantitative data that have been obtained relevant to the interpretation of diffusive processes in rocks and minerals many resources cover these topics including rimg volume 72 diffusion in minerals and melts zhang and cherniak 2010 and several textbooks crank 1975 glicksman 2000 particularly relevant to the discussion of petrochronology are summaries of the theory and controls on diffusion brady and cherniak 2010 zhang 2010 as well as diffusion rates in feldspar cherniak 2010a accessory minerals cherniak 2010b garnet ganguly 2010 mica pyroxene and amphibole cherniak and dimanov 2010 and melts zhang and ni 2010 zhang et al 2010 rather than duplicate that material our goal is to explore the obstacles and opportunities presented by the effects of diffusion as they inform the rates of petrologic processes to achieve this goal we emphasize key principles and illustrative examples quantitative interpretation of the effects of diffusion assumes predictability of numerous factors that may affect chemical or isotopic transport including temperature initial and boundary conditions water and oxygen fugacities activities of other components multiple mechanisms of diffusion and crystal chemistry coupling of the substitution of elements into different crystallographic sites additionally the extraction of meaningful ages durations of events and temperatures requires

stable isotope thermometry at high temperatures determination of accurate temperatures for geological events has been the grail of stable isotope geochemistry since the seminal 1947 paper by urey in theory this should be simple calibrated mineral pairs are common analysis is rapid and there is no significant pressure correction however in spite of widespread application the promise of reliable thermometry has been elusive stable isotope temperatures in metamorphic and igneous rocks are often controversial is the fractionation between two phases a thermometer speedometer rate dependant hygrometer p h2o dependant or chimera a number of factors have contributed to this uncertainty including incomplete and sometimes conflicting calibration of isotope fractionation factors limited understanding of the kinetics of mineral exchange and the lack of microanalytical techniques this situation has improved dramatically over the past decade permitting reliable and detailed thermal histories to be inferred in a landmark paper bottinga and javoy 1975 empirically calibrated the oxygen isotope fractionation factors among ten rock forming minerals at t 500 c their compilation shows that 84 of analyzed samples contain at least three minerals meeting a concordance test for equilibrium they concluded the great majority of igneous and metamorphic rocks has conserved a state of oxygen isotope exchange equilibrium if correct this bodes well for thermometry however this conclusion was contested by deines 1977 who critically examined the existing data and concluded that less than half of the rocks analyzed to date would yield concordant 18o derived temperatures while seeming irreconcilable both conclusions are based on fact all rocks contain some degree of disequilibrium but many also preserve a thermometric record it is the purpose of this review to discuss the new strategies for reliable isotope thermometry and to explore disequilibrium processes so they may be recognized and properly interpreted the organization of this paper will be to discuss the assumptions

preparation and analysis of coal seam data utilizing paleoenvironment modeling hazard 7 coal eastern kentucky abstract pennsylvanian strata of the hazard coalfield eastern kentucky contain fluvial upper delta plain facies characterized by thick localized coals bay fill shales levee silt and sandstones and channel fill sands and gravels although the deltaic nature of these sediments has long been established mining and exploration activities in the district require a thorough understanding of small areas within the delta environment coal quantity and quality trends in the hazard 7 seam the major producer in the area have been examined in detail the 7 coal accumulated in a peat swamp restricted laterally by a major fluvial channel three types of non coal parting are recognized thin tabular fine grained partings resulted from periods of increased terrigenous influx into the swamp lenticular crevasse splay deposits locally split the coal wedge shaped fine to coarse grained partings of probable levee origin are found along the channel margin post swamp deposits consist of thick bay fill shales thin shales silt and sandstones deposited on floodplains and channel fill sandstones and gravels the modeling technique discussed provides guidance for mine development and regional exploration by prediction of coal seam quantity and quality trends from local geologic features the thickest 7 coal is split by thin tabular partings and is overlain by thick shale sequences coal overlain by silt and sandstone is thinner and unsplit and typically of higher heat value regional seam thinning due to channel scour is recognized factors which control the configuration of the coal seam include position within the peat swamp proximity to the fluvial channel swamp burial processes and paleochannel sinuosity

investigating the stratigraphy and palaeoenvironments for a suite of newly discovered mid cretaceous vertebrate fossil localities in the winton formation queensland australia the winton formation of central queensland is recognized as a quintessential source of mid cretaceous terrestrial faunas and floras in australia however sedimentological investigations linking fossil assemblages and palaeoenvironments across this unit remain limited the intent of this study was to interpret depositional environments and improve stratigraphic correlations between multiple fossil localities within the preserved winton formation in the eromanga basin including isisford lark quarry and bladensburg national park twenty three facies and six repeated facies associations were documented indicating a mosaic of marginal marine to inland alluvial depositional environments these developed synchronously with the final regression of the eromanga seaway from central australia during the late albian early turonian investigations of regional and local scale structural features and outcrop core and well analysis were combined with detrital zircon provenance signatures to help correlate stratigraphy and vertebrate faunas across the basin significant palaeoenvironmental differences exist between the lower and upper portions of the preserved winton formation warranting informal subdivisions a lower tidally influenced fluvial deltaic member and an upper inland alluvial member this work further demonstrates that the isisford fauna is part of the lower member of the preserved winton formation whereas fossil localities around winton including lark quarry and bladensburg national park are part of the upper member of the winton formation these results permit a more meaningful framework for both regional and global comparisons of the winton flora and fauna

diffusion of dissolved carbonate in magmas experimental results and applications the diffusivity of dissolved carbonate in sodium aluminosilicate 60 sio 2 30 na 2 o 10 al 2 o 3 and iron free basalt melts was measured by a 14 c thin source tracer technique at conditions of combined high temperature and high pressure ranging from 800 c to 1350 c and 0 5 to 18 kbar for the simple melt and 1350 to 1500 c at 15 kbar for the haplobasalt melt the two melts have similar dissolved carbonate transport properties expressed for the simple system at 0 5 kbar by d carbonate 3 559exp 46 600 rt the pressure dependence at 1200 c is given by d carbonate 4 13 10 7 exp 11 02p rt the activation energy of 46 6 kcal mole is low relative to expected values for small highly charged cations suggesting that the actual diffusing species is a larger carbonate anion this interpretation is supported by the 11 cm 3 mole activation volume which corresponds to twice the molar volume of oxygen anions because the 14 c diffusion gradients conform quite well to a constant diffusivity thin source model there can be no strong dependence of carbonate diffusivity upon dissolved carbonate content at least in the 0 0 2 wt range represented by the experimental profiles carbonate diffusion is markedly different from previously determined systematics for water being 1 2 orders of magnitude slower in granitic magmas and considerably faster in basalts this difference can result in diffusional fractionation of co 2 and h 2 o in magmas which may be most significant in small scale processes such as growth of vapor bubbles and formation of some types of glass inclusions in phenocrysts the new data also place constraints on the rate at which co 2 dominated fluid bubbles can actually grow under more or less isothermal conditions at 10 kbar the growth rate is on the order of 1 mm day depending upon the degree of supersaturation in co 2 when combined with knowledge of initial co 2 contents of magmas and observed characteristics of dispersed bubbles e g in ocean floor basalt glasses the diffusivity data may expedite the reconstruction of magma decompression paths