a discussion of the structure of the precambrian and lower paleozoic basement of the central andes between 22 and 32 s lat by mon and hongn

geochemical effects of co2 sequestration in sandstones under simulated in situ conditions of deep saline aquifers abstract the geochemical effects of brine and supercritical co 2 scco 2 on reservoir rocks from deep 1500 2000 m saline aquifers were examined via experimental simulation at in situ conditions dry sandstone samples were mounted in a triaxial cell and autoclave system evacuated and saturated with 1 m nacl solution the brine rock system was allowed to react at 30 mpa confining pressure 15 mpa pore fluid pressure and 60 c while scco 2 was injected at a pressure gradient of 1 2 mpa the experiment was conducted for a period of 1496 h during which fluids were periodically sampled and analyzed the ph measured in partially degassed fluid samples at 25 c decreased from a starting value of 7 0 4 3 9 days and finally 5 1 after saturation with scco 2 fluid analyses indicate that most of the major e g ca mg fe mn and trace elements e g sr ba pb of the sandstone increase in concentration during the reaction with brine and scco 2 these results are supported by scanning electron microscopy which indicates dissolution of dolomite cement k feldspar and albite in addition to dissolution reactions the formation of montmorillonite was observed by adjusting surface area and reaction rates of dissolution and precipitation geochemical modeling of the experiments could reproduce long term trends in solution chemistry and indicated limited rates of dissolution as the system remained strongly undersaturated with most minerals including carbonates the geochemical models could not account for decreases in concentration of some elements changes in solution composition resulting from changes in imposed pressure gradient and the observed ca mg and si al ratios in solution

anisotropy of gas permeability associated with cleat pattern in a coal seam of the kushiro coalfield in japan an underground investigation has been performed in a subbituminous coal seam exhibiting a particular cleat pattern in the kushiro coalfield japan the coal cleat pattern shows some analogy to isolated straight joints and is believed to have been formed during the late tertiary period by a compressive tectonic stress roughly in the east west direction three cylindrical coal specimens representing the three orthogonal axes of the coal seam with respect to the bedding plane and its associated cleat were cored from a large block of coal gas permeabilities of the three coal specimens were measured under the same hydrostatic pressure conditions results clearly revealed anisotropy in permeability of the coal seam under relatively low confining pressures of less than about 12 mpa the specimen cored parallel to both the bedding plane and cleat strike showed the highest permeability even though the cleats were partly filled with calcite and clay minerals the permeability in this direction was 2 5 times higher than perpendicular to the bedding plane and 3 times higher than in the direction parallel to the bedding plane but perpendicular to the cleat strike this suggests that the cleats play a greater role than bedding planes in controlling fluid flow in the coal seam the permeability in the three orientations however converged to the same value at confining pressures above about 16 mpa this may suggest that both cleats and bedding planes in a coal seam can close due to earth pressure if the coal seam is located below a certain depth it further indicates that the traditional view that gas permeability is always greater parallel to the coal bedding than perpendicular to it should be reconsidered

the volcanic and magmatic evolution of volcan ollague a high k late quaternary stratovolcano in the andean central volcanic zone abstract volcan ollague is a high k calc alkaline composite volcano constructed upon extremely thick crust in the andean central volcanic zone volcanic activity commenced with the construction of an andesitic to dacitic composite cone composed of numerous lava flows and pyroclastic deposits of the vinta loma series and an overlying coalescing dome and coulee sequence of the chasca orkho series following cone construction the upper western flank of ollague collapsed toward the west leaving a collapse amphitheater about 3 5 km in diameter and a debris avalanche deposit on the lower western flank of the volcano the deposit is similar to the debris avalanche deposit produced during the may 18 1980 eruption of mount st helens u s a and was probably formed in a similar manner it presently covers an area of 100 km2 and extends 16 km from the summit subsequent to the collapse event the upper western flank was reformed via eruption of several small andesitic lava flows from vents located near the western summit and growth of an andesitic dome within the collapse amphitheater additional post collapse activity included construction of a dacitic dome and coulee of the la celosa series on the northwest flank field relations indicate that vents for the vinta loma and post collapse series were located at or near the summit of the cone the vinta loma series is characterized by an anhydrous two pyroxene assemblage vents for the la celosa and chasca orkho series are located on the flanks and strike n55 w radial to the volcano the pattern of flank eruptions coincides with the distribution in the abundance of amphibole and biotite as the main mafic phenocryst phases in the rocks a possible explanation for this coincidence is that an unexposed fracture or fault beneath the volcano served as a conduit for both magma ascent and groundwater circulation in addition to the lava flows at ollague magmas are also present as blobs of vesiculated basaltic andesite and mafic andesite that occur as inclusions in nearly all of the lavas all eruptive activity at ollague predates the last glacial episode 11 000 a b p because post collapse lava flows are overlain by moraine and are incised by glacial valleys present activity is restricted to emission of a persistent 100 m high fumarolic steam plume from a vent located within the summit andesite dome sr and nd isotope ratios for the basaltic andesite and mafic andesite inclusions and lavas suggest that they have assimilated large amounts of crust during crystal fractionation in contrast narrow ranges in 143nd 144nd and 87sr 86sr in the andesitic and dacitic lavas are enigmatic with respect to crustal contamination

chemical alteration and mineral growth under high pco2 conditions insights from the mineral chemistry of carbonate phases in the caprese reservoir northern apennines central italy abstract carbon cycle is one of the most complex geochemical cycles of the earth as it involves atmosphere hydrosphere biosphere and lithosphere among these different geochemical spheres mechanisms and reaction rates governing migration and fixation of carbon i e fluxes such as the stability of the different carbonates minerals under specific conditions in crustal reservoirs are still matter of detailed studies in this work sem and xrd investigations and emp analyses were combined to study the mineralogical and chemical compositions of carbonate phases occurring in strongly altered triassic volcanic rocks hosting a co 2 reservoir namely the caprese reservoir located in eastern tuscany central italy the caprese crustal fluid reservoir lying at 3300 m depth beneath the quaternary san cassiano basin hosts a supercritical co 2 n 2 rich phase and a na cl rich saline up to 81 5 g l brine the mineralogical assemblage consists of authigenic microcrystalline quartz ca fe mg carbonates na k clay minerals and fe oxides the primary minerals being almost completely chemically altered by secondary processes scanning electron microscope images and cation ca fe mg contents in carbonates highlighted that zoned ankerite was re grown on calcite crystals due to interactions processes with co 2 rich fluids the geochemical and mineralogical data provided useful insights for understanding both the processes that formed the c bearing minerals and their growth in deep saline reservoirs

reconstructing holocene geomagnetic field variation new methods models and implications reconstructions of the holocene geomagnetic field and how it varies on millennial timescales are important for understanding processes in the core but may also be used to study long term solar terrestrial relationships and as relative dating tools for geological and archaeological archives here we present a new family of spherical harmonic geomagnetic field models spanning the past 9000 yr based on magnetic field directions and intensity stored in archaeological artefacts igneous rocks and sediment records a new modelling strategy introduces alternative data treatments with a focus on extracting more information from sedimentary data to reduce the influence of a few individual records all sedimentary data are resampled in 50 yr bins which also means that more weight is given to archaeomagnetic data during the inversion the sedimentary declination data are treated as relative values and adjusted iteratively based on prior information finally an alternative way of treating the sediment data chronologies has enabled us to both assess the likely range of age uncertainties often up to and possibly exceeding 500 yr and adjust the timescale of each record based on comparisons with predictions from a preliminary model as a result of the data adjustments power has been shifted from quadrupole and octupole to higher degrees compared with previous holocene geomagnetic field models we find evidence for dominantly westward drift of northern high latitude high intensity flux patches at the core mantle boundary for the last 4000 yr the new models also show intermittent occurrence of reversed flux at the edge of or inside the inner core tangent cylinder possibly originating from the equator less

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

paleomagnetic dating of postglacial sediment offshore lake superior minnesota wisconsin u s a abstract four gravity cores and two piston cores obtained from offshore regions of lake superior were analyzed for variations in geomagnetic declination and inclination in natural remanent magnetization nrm sedimentation rates in offshore lake superior 20 cm 1000 yr are much slower than in great lakes environments where paleomagnetic dating has been applied before typically 1 m 1000 yr five of the six cores could be correlated on the basis of declination and four of the six could be correlated on the basis of inclination absolute age assignment to declination events by correlation to a radiocarbon dated core from lake st croix minnesota tentatively shows that sedimentation rates in lake superior have changed from relatively fast to relatively slow to intermediate values in postglacial times

experimental evaluation of mixed fluid reactions between supercritical carbon dioxide and nacl brine relevance to the integrity of a geologic carbon repository abstract the reactive behavior of a mixed fluid supercritical co2 and brine under physical chemical conditions relevant to geologic storage and sequestration in a carbon repository is largely unknown experiments were conducted in a flexible cell hydrothermal apparatus to evaluate fluid rock aquifer plus aquitard reactions that may adversely impact the integrity of the repository a 5 5 molal nacl brine rock system was held at 200 c and 200 bars 20 mpa for 32 days 772 h to approach steady state then injected with co2 and allowed to react for an additional 45 days 1079 h in a separate experiment at 200 c and 200 bars the system was allowed to react for 77 days 1845 h without injection of co2 corroded magnesite and euhedral siderite crystallized in a paragenetic sequence after co2 injection nucleation and growth of siderite on shale suggests the aquitard is a reactive component in the system changes in elemental abundances in the brine following addition of co2 include ph decrease and depletion of sodium due to accelerated growth of analcime a ph increase follows pressure and temperature decrease and loss of saturated co2 from acidic brine silica concentrations and dissolution rates are enhanced and silica precipitation inhibited in the acidic brine geochemical reactions in a carbon repository extend beyond ph decrease and carbonate mineral precipitation rock dominated reaction systems yield to acid dominated and related reactions controlled by mixed fluid equilibria i e a fluid dominated system escape of co2 or migration of brine from the repository into overlying aquifers may cause silica super saturation and increased alkalinity due to mixed fluid phase equilibria these geochemical changes could be monitored in aquifers as indicators of repository integrity return of silica super saturated brine to a rock dominated reaction system buffered to neutral ph conditions may enhance precipitation of quartz chalcedony or amorphous silica in addition to the potential effects beneficial or deleterious that silica super saturation and precipitation may hold for repository performance an understanding of the effects of multi phase equilibrium relationships between supercritical co2 and dissolved silica in aquifer brine systems also raises new questions for a variety of geologic systems multi phase fluid equilibria may for example account for quartz cements in some sedimentary basin sandstones and quartz vein mineralization in some ore districts

tectono metamorphic evolution of a convergent back arc the famatinian orogen sierra de quilmes sierras pampeanas nw argentina

evolution of sealing efficiency for co2 geological storage due to mineral alteration within a hydrogeologically heterogeneous caprock in co2 geological storage cgs context the evolution of the caprock sealing capacity has received increasing attention particularly on a geological time span thousands of years at this time scale geochemical reactions may enhance or weaken the caprock quality it is widely recognized that for the reservoir geological heterogeneities affect the concentration and spatial distribution of co2 and then affect the extent of gas water rock interactions which in turn alters the hydrogeological properties of the reservoir however much less attention of these effects has been paid to the caprock in this study we presented and applied a novel approach to evaluate the effects of permeability and porosity heterogeneities on the alteration of minerals the associated evolution of the caprock sealing efficiency and the containment of supercritical co2 scco2 within the caprock even though this is a generic study several conditions and parameters such as pressure permeability and mineral composition were extracted from a caprock layer of the shiqianfeng formation in the ordos basin demonstration site in china for the sake of simplification a 2 dimensional model was designed to represent the caprock domain we firstly generated an appropriate heterogeneous random field of permeability with the average permeability taken from the uppermost mudstone layer of the shiqianfeng formation and then the heterogeneity in porosity was incorporated using a joint normal distribution method based on the available data homogeneous mineral compositions of the reservoir and caprock were used in all simulations simulations of three cases were performed including a homogeneous case a case with only permeability heterogeneity and a case with both permeability and porosity heterogeneities the results demonstrate dramatic influences of permeability and porosity heterogeneities on the migration of scco2 within the caprock the alteration of minerals and therefore the evolution of the caprock sealing quality specific to the data used in this study hydrogeological heterogeneities facilitated the overall penetration of scco2 within the caprock and promoted the alteration of minerals thereby weakening the caprock sealing efficiency over the simulation time

mineral occurrence and its impact on fracture generation in selected qinshui basin coals an experimental perspective abstract the effect of mineral matter on the fracture evolution was investigated for lower permian and upper pennsylvanian coal samples from the qinshui basin of china optical microscopy scanning electron microscopy with energy dispersive x ray spectrometry sem eds and x ray computed tomography x ray ct were used to investigate the composition and modes of occurrence of minerals within the coals and to characterize the natural and induced fractures present within the samples the spatial distribution of mineral matter investigated by x ray ct demonstrates that the variation of mineralization within the cleats fractures occurred at fine scales and most of minerals were scattered in coal core samples the original fractures normally were present as two sets one set was almost parallel to the bedding plane and the other was almost perpendicular to the bedding plane for created fractures the difference in density between the matrix and mineral matter may weaken the cohesion of coals and it could explain why the created fractures propagate along the junction of minerals and organic coal matrix the internal fracture porosities varied from 0 06 to 20 69 which indicates a strong internal heterogeneity of the coals after a stress is applied the inclination of the main shear fractures ranges from 55 to 95 using energy analysis the fracture energy appears to represent nearly half of the total dissipated energy which can be correlated with the fracture density and orientation the formation and distribution of shear fractures is related to the spatial distribution of mineral matter and the overall mineral content these investigations serve to characterize hydro fracturing and pulverized coal generation during coalbed methane development

distribution and origin of minerals in high rank coals of the south walker creek area bowen basin australia the coals of the south walker creek area in the northern bowen basin with a vitrinite reflectance rvmax of 1 7 to 1 95 are among the highest rank coals currently mined in australia x ray diffraction studies have identified an unusual mineral variation through the vertical sequence with kaolinite rich assemblages typical of other australian coals at the top and bottom of the seam section and an illite chlorite assemblage resembling a metamorphic association in the middle calcite and ankerite are also abundant in parts of the vertical sequence diaspore is abundant in the middle section of the seam in some areas and paragonite dickite or nacrite occurs in some locations as well the distribution of the non carbonate mineral assemblages cross cuts the seam stratigraphy and appears to be primarily controlled by faults and other structural features integration of the mineral distribution with optical and electron microscope data on the coal and non coal bands chemical data from coal ash analysis and information from x ray micro tomography suggests that the illite chlorite and diaspore bearing assemblages resulted from hydrothermal effects associated with fluid migration through the middle part of the coal seam this is further confirmed by the development of metamorphic textures in a tonstein band also altered to illite and chlorite in the illite rich part of the seam section in contrast to a tonstein with more normal sedimentary textures and a kaolinite composition in the kaolinite rich upper part of the seam detailed studies of cleat mineralisation suggest that fluids rich in ca mg and al were introduced relatively early in the seam s post depositional history associated with heat flow sufficient to alter the minerals in the coal and tonstein in the affected part of the seam section the relatively uniform vitrinite reflectance profile observed through the seam section may indicate that the coal was already of high rank before the fluids were introduced or that any localised heat effects on the organic matter associated with the changes in clay mineralogy were overprinted by subsequent wider ranging rank advance processes

early paleozoic orogeny in southern south america abstract in northwest argentina weakly metamorphic clastic and calcareous sedimentary rocks of latest precambrian to lower cambrian age puncoviscana formation and related units contain an abundant ichnofauna of both chronostratigraphic and paleoenvironmental value in the western and central sierras pampeanas metasedimentary and metavolcanic rocks are considered to form part of the same geotectonic unit this pampean orogenic cycle includes geosynclinal sedimentation of latest precambrian to lower cambrian age as well as magmatism metamorphism and deformation of middle to upper cambrian age documented by an angular unconformity below the upper cambrian to devonian rocks of the famatinian orogenic cycle in some of the metamorphic rocks of the pampean cycle a pre ordovician folding is also distinguished from a later tectonic overprinting hence the concept of a pampean cycle differs from other concepts of late precambrian orogenic cycles of south america which are only defined by radiometric ages the pampean orogenesis may be compared with the ross orogenesis of the transantarctic mts the tyennan orogenesis of australia and some of the deformation phases of the damara orogen in namibia

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

effects of feldspar and salinity on the mineral sequestration capacity of co2 in high salinity aquifers mineral sequestration of co2 is considered to be the safest mechanism in the long term storage of co2 in deep saline aquifers this study aims to investigate the effect of feldspar and salinity on the mineral sequestration capacity of co2 in deep high salinity brine aquifers by taking jiangling depression of jianghan basin for instance numerical simulation on the long term geochemical reaction and transport was performed by taking toughreact as the simulation tool simulation results indicate that the effect of feldspar on the mineral trapping capacity of co2 does not depend on the total content of feldspar but depends on feldspar type and relative content with mg rich minerals such as chlorite or dolomite present the mineral composition abundant in k feldspar is less favorable for the mineral sequestration capacity of co2 for the reason that a large amount of illite precipitates consuming a lot of al3 in the aqueous solution thereby limiting the precipitation of dawsonite especially for the high temperature sedimentary environment in addition the effect of salinity on the mineral sequestration capacity of co2 represents two aspects one for the longer migration distance due to the lower solubility of higher salinity and the other for co2 mineral trapping capacity per 1 m3 medium which is not in simple decreased with salinity depending on k feldspar present or not for the mineral composition with k feldspar present co2 mineral trapping capacity decreases with salinity while with albite instead of k feldspar it increases with salinity owing to more precipitation of dawsonite

sedimentary processes in the great lakes sediments in the great lakes are subject to four general categories of processes input transport deposition and postdepositional alteration sedimentary input is from coastal erosion 64 riverine input 26 atmospheric transport 3 and several lesser sources 7 once in the lake sediments are transported to their place of deposition along the bottom and or in suspension depending upon grain size and density the rate of deposition in the great lakes is variable and ranges from zero in some areas to over 6000 g m sup 2 yr sup 1 in the eastern basin of lake erie after deposition sediments undergo bioturbation dissolution of carbonate and opal remobilization of many metals followed by reprecipitation within the surficial oxidized layer and degradation of organic compounds

spline analysis of holocene sediment magnetic records uncertainty estimates for field modeling 1 sediment and archeomagnetic data spanning the holocene enable us to reconstruct the evolution of the geomagnetic field on time scales of centuries to millennia in global field modeling the reliability of data is taken into account by weighting according to uncertainty estimates uncertainties in sediment magnetic records arise from 1 imperfections in the paleomagnetic recording processes 2 coring and sub sampling methods 3 adopted averaging procedures and 4 uncertainties in the age depth models we take a step toward improved uncertainty estimates by performing a comprehensive statistical analysis of the available global database of holocene magnetic records smoothing spline models that capture the robust aspects of individual records are derived this involves a cross validation approach based on an absolute deviation measure of misfit to determine the smoothing parameter for each spline model together with the use of a minimum smoothing time derived from the sedimentation rate and assumed lock in depth departures from the spline models provide information concerning the random variability in each record temporal resolution analysis reveals that 50 of the records have smoothing times between 80 and 250 years we also perform comparisons among the sediment magnetic records and archeomagnetic data as well as with predictions from the global historical and archeomagnetic field models combining these approaches we arrive at individual uncertainty estimates for each sediment record these range from 2 5 to 11 2 median 5 9 interquartile range 5 4 to 7 2 for inclination 4 1 to 46 9 median 13 4 interquartile range 11 4 to 18 9 for relative declination and 0 59 to 1 32 median 0 93 interquartile range 0 86 to 1 01 for standardized relative paleointensity these values suggest that uncertainties may have been underestimated in previous studies no compelling evidence for systematic inclination shallowing is obtained from the analysis of the available database of holocene sediment magnetic records the analysis highlights the importance of collecting oriented cores publishing and archiving unprocessed raw paleosecular variation determinations and presenting a detailed chronology so that changes in the sedimentation rate can be assessed with regard to future field models workers should consider rejection of anomalous cores through comparisons to other sources and ensure that realistically large uncertainties are allocated to high latitude declination records

reconstructing the holocene geomagnetic field abstract knowledge of the holocene evolution of earth s magnetic field is important for understanding geodynamo processes in the core is necessary for studying long term solar terrestrial relationships and can provide useful age constraints for archeologicaland stratigraphic applications continuous time varying global field models based on archeo and paleomagnetic data are useful tools in this regard we use a comprehensive data compilation and recently refined modelling strategies to produce cals10k 1b the first time varying spherical harmonic geomagnetic field model spanning 10 ky the model is an average obtained from bootstrap sampling to take account of uncertainties in magnetic components and ages in the data and hence has version number 1b instead of 1 this model shows less spatial and temporal resolution than earlier versions for 0 3 ka and particularly aims to provide a robust representation of the large scale field at the core mantle boundary cmb we discuss the geomagnetic dipole evolution and changes in holocene magnetic field morphology at the cmb as shown by the new reconstruction the results are compatible with earlier models cals3k 3 and cals3k 4 for 0 3 ka but reveal some clear deficiencies in the 0 7 ka cals7k 2 model prior to 3 ka cals10k 1b is able to resolve mobile and structurally evolving high latitude radial field flux lobes at the cmb in both hemispheres as well as persistent non zonal structure in the 10 ky average contributions to the average field from time varying structures in the equatorial indonesian australian region are particularly striking

ages of metamorphic and deformational events in the sierra de ancasti pampean ranges argentina metamorphic rocks of the sierra de ancasti catamarca province northwestern argentina were investigated by means of the rb sr method three phases of metamorphism can be distinguished a first possible homogenization of sr possibly took place 524 m y ago a second one can be subdivided into a mean metamorphism at 472 m y and a statical recrystallization at about 450 m y a last weak metamorphism at about 420 m y can be recognized only by ages of cooling of biotites the relations of the metamorphic rocks to granitic intrusions and regional comparisons support this subdivision similar ages have been reported from various regions of the gondwana continent

palaeomagnetic chronostratigraphy of holocene sediments niagara basin lake ontario canada the north american great lakes contain 18 of the world s fresh water lake ontario is the lowermost downstream of the great lakes and has existed for the past 13 000 yrs yet details of the evolution of this lake during this period remain sketchy over the summers of 1992 and 1993 piston cores sampled the late pleistocene and holocene sediments within the niagara and mississauga basins of lake ontario the history of late pleistocene and holocene environments and deposition rates are assessed by palaeomagnetic secular variations and stratigraphical descriptions of the sediment pollen samples were taken from the sediment to better constrain the palaeomagnetic ages and to establish the boundary between pleistocene and holocene deposition at 10 500 yr bp secular variation type curves were used to provide estimates of the age of the late pleistocene and holocene sediments a description of the stratigraphical sequence is included the sediments can be divided into six stratigraphical units for which ages have been derived the lowermost unit is a diamict upper contact 12 500 yr bp next in the sequence is a deformed unit upper contact 12 300 yr bp followed by a thinly laminated unit upper contact 12 000 yr bp a massive unit upper contact 11 800 11 000 yr bp and an irregularly laminated unit upper contact 10 500 yr bp the unit deposited in the deep water of the basin since 10 500 yr bp is an iron banded mud sedimentation rates of the basin compiled from pollen and from magnetic data are compared and the post glacial geological history of the niagara basin of western lake ontario is discussed

geomagnetic field for 0 3 ka 1 new data sets for global modeling 1 paleomagnetic and archeomagnetic records are used in both regional and global studies of earth s magnetic field we present a description and assessment of five newly compiled data sets also used in the companion paper by korte et al 2009 to produce a series of time varying spherical harmonic models of the geomagnetic field for the last 3000 years data are drawn from our compilation of lake sediment records and from the online database geomagia50v2 the five selections are available from the earthref digital archive at http earthref org cgi bin erda cgi n 944 data are grouped according to the source of material and we conducted separate assessments of reliability for archeomagnetic artifacts and lava flows the arch3k dat data set and for sediments sed3k dat the overall number of data is 55 greater than in previous compilations constrained data sets were selected using different criteria for each group winnowing of archeological data was based on uncertainties supplied by the original data providers the lake sediment data assessment relied on preassigned age uncertainties and one or more of the following comparisons with archeomagnetic data from the same region regional consistency among several lakes and consistency with global archeomagnetic models we discuss relative merits of a larger unconstrained data set or a smaller possibly more reliable one the constrained data sets eliminate a priori up to 35 of the available data in each case and rely on potentially subjective assessments of data quality given the limited data available our analyses indicate that iterative rejection of a small number 1 1 5 of outlying data during global field modeling is a preferable approach specific regional comparisons among the models and data support the conclusion that korte et al s outlier free cals3k 3 model based on all available measurements from sediments and archeological artifacts currently provides the best global representation of the 0 3 ka field the arch3k 1 model provides a better fit to the denser european archeomagnetic data and may be better in that region

potential environmental issues of co2 storage in deep saline aquifers geochemical results from the frio i brine pilot test texas usa abstract sedimentary basins in general and deep saline aquifers in particular are being investigated as possible repositories for large volumes of anthropogenic co2 that must be sequestered to mitigate global warming and related climate changes to investigate the potential for the long term storage of co2 in such aquifers 1600 t of co2 were injected at 1500 m depth into a 24 m thick c sandstone unit of the frio formation a regional aquifer in the us gulf coast fluid samples obtained before co2 injection from the injection well and an observation well 30 m updip showed a na ca cl type brine with 93 000 mg l tds at saturation with ch4 at reservoir conditions gas analyses showed that ch4 comprised 95 of dissolved gas but co2 was low at 0 3 following co2 breakthrough 51 h after injection samples showed sharp drops in ph 6 5 5 7 pronounced increases in alkalinity 100 3000 mg l as hco3 and in fe 30 1100 mg l a slug of very high doc values and significant shifts in the isotopic compositions of h2o dic and ch4 these data coupled with geochemical modeling indicate corrosion of pipe and well casing as well as rapid dissolution of minerals especially calcite and iron oxyhydroxides both caused by lowered ph initially 3 0 at subsurface conditions of the brine in contact with supercritical co2 these geochemical parameters together with perfluorocarbon tracer gases pfts were used to monitor migration of the injected co2 into the overlying frio b composed of a 4 m thick sandstone and separated from the c by 15 m of shale and siltstone beds results obtained from the frio b 6 months after injection gave chemical and isotopic markers that show significant co2 2 9 compared with 0 3 co2 in dissolved gas migration into the b sandstone results of samples collected 15 months after injection however are ambiguous and can be interpreted to show no additional injected co2 in the b sandstone the presence of injected co2 may indicate migration from c to b through the intervening beds or more likely a short term leakage through the remedial cement around the casing of a 50 year old well results obtained to date from four shallow monitoring groundwater wells show no brine or co2 leakage through the anahuac formation the regional cap rock

holocene geomagnetic secular variation records from north eastern australian lake sediments summary secular variation records have been obtained from cores from lakes barrine and eacham two north eastern australian volcanic crater lakes the results from several cores have been stratigraphically correlated and then stacked and smoothed the chronology provided by radiocarbon dating indicates that the lake eacham sequence spans the last 5700 calendar years the time scale for the lake barrine record is less weil constrained but it

palaeomagnetic and mineral magnetic studies of sediment from ball s cavern schoharie u s a abstract two sediment sequences from a cave near schoharie n y have been sampled for palaeomagnetic measurements the nature of the palaeomagnetic records obtained was found to be similar to other north american records a correlation can be made with lake sediment records back to 13 000 yr b p and with a sediment record from bessette creek in canada for the period between 23 000 and 30 000 yr b p during both periods the dominant long term trend of the vgp path has been that of anticlockwise motion but during the last 13 000 years there has been more superimposed short term clockwise motion than during the earlier period magnetic properties of the sediments suggest that magnetite is the dominant magnetic mineral and this is confirmed by the mossbauer spectra of both the sediments and magnetic extracts mossbauer measurements on the magnetic extracts also detected the presence of a small amount of haematite

palaeomagnetism of a core sediment from the inland sea japan seto naikai palaeomagnetic measurements on a giant core sample 20 cm in diameter and 7 38 m long collected from mizushima nada the inland sea japan seto naikai provide evidence of post depositional magnetization the geomagnetic secular variation from about 4000 to 8000 yr bp is characterized by a long period of westerly declination before 6600 yr bp the maximum deflection is beyond 50 w during this period the palaeomagnetic record further demonstrates that there is a hiatus over 3000 yr in sedimentation due 10 the sea level change around 6 85 m from sea bottom and that the lower limit of the sea level around 8000 yr bp is 18 5 m beneath the present sea level

paleomagnetic dating of postglacial sediments vancouver island canada abstract cores taken from lakes throughout vancouver island consist of a homogeneous sequence of postglacial sediments that is usually underlain by glacial varves or outwash deposits the paleoinclination and the relative paleodeclination logs of the postglacial sequence for each core forms a fairly consistent pattern of oscillations that has been used for the correlation of the cores from lake to lake this correlation method provides important information on the relative timing of the cessation of glacial outwash deposition as well as the rate of postglacial deposition from lake to lake unfortunately 14 c dates on discrete organic material and the presence of the mazama tephra layer 6800 bp in the postglacial sequence at shawnigan lake have not provided sufficient reliable information to date the paleomagnetic record or the postglacial glacial boundary

late quaternary secular variation of geomagnetic declination in western new york a secular variation record of the geomagnetic declination has been obtained from glaciolacustrine varved clays and postglacial sediments sampled both from outcrop and from piston cores from lake ontario it appears to be uninterrupted and covers the interval 14 000 years b p 14c to the present the record for the interval 14 000 12 300 years b p consists of true declination and was obtained from samples collected from outcrop the record for the interval 12 500 years b p to the present consists of relative declination and was obtained from piston cores the secular variation record is internally consistent and is compatible with the chronology of events known to have occurred during and following the deglaciation of western new york use of the record for magnetic correlation within the study area is demonstrated

late quaternary paleomagnetic record of the goderich basin lake huron paleomagnetic analysis of two cores taken of the late quaternary sequence of the goderich basin lake huron resulted in high resolution declination inclination intensity of magnetization j magnetic susceptibility k and q ratio j k curves there was a consistent relative relationship of the features along the curves of all five parameters for both cores studied which confirms the reproducibility of the method and suggests that paleomagnetic curves can be used for time parallel correlation of the late quaternary sequence of the goderich basin

long period geomagnetic secular variations since 12 000 yr bp a comparison of secular variation records of the geomagnetic field inclination obtained from palaeomagnetic studies of european and north american post glacial and late glacial sediments suggests that geomagnetic westward drift has persisted through the past 12 000 yr between 12 000 and 2 500 yr bp the overall average drift rate was between 0 14 and 0 16 deg yr 1 at 2 500 yr bp it is tentatively suggested that the drift rate increased and rose to a maximum of nearly 0 5 deg yr 1 before decreasing to historically observed values of 0 25 deg yr 1

experimental study of co2 brine rock interaction during co2 sequestration in deep coal seams abstract co 2 sequestration in deep coal seams is a potential option for reducing greenhouse gas emissions once co 2 is injected into coal seams sealing capability of the cap rock is critical to investigate and quantify reactions over time between co 2 cap rocks and brine associated with selected cap rocks of the no 3 coalbed of the qinshui basin in china batch experiments were conducted for reacting powdered rock samples 180 220 m with co 2 and brine as well as co 2 free brine at 160 c and 15 mpa the analysis of leachate chemistry indicated significant mobilization of major elements from dissolution of carbonate and silicate minerals in the coal measure strata analysis of reacted solids by xrd and sem also revealed appreciable changes in mineralogical compositions for lithic sandstone after reaction with co 2 brine the contents of quartz plagioclase illite and chlorite increased considerably whereas the contents of illite smectite biotite and kaolinite decreased more or less the calcareous mudstone reacting with co 2 brine and co 2 free brine all showed major mineralogical alteration after 12 days of treatment the modeling results identified key chemical processes but they also showed that the models are not capable of covering all possible contingencies the precipitation of carbonate minerals could also enhance the security of co 2 sequestration in deep coal seams

on the current state of lake sediment palaeomagnetic research summary it is now possible to obtain high quality records of geomagnetic secular variations in the direction though not the magnitude of the ancient field type curves are presented for four regions namely north america west europe argentina and australia constructed by fitting cubic splines to data stacked from numbers of cores of post glacial sediments ways in which the results can be used to investigate the grosser properties of the ancient field are discussed

archaeo and paleosecular variation and long term asymmetries of the geomagnetic field this report summarizes progress made during the last four years in i obtaining records of the geomagnetic secular variation using paleomagnetic techniques ii analysis and modelling of the secular variation and iii the study of asymmetries in the time averaged field seen both as departures from the geocentric axial dipole model and as statistical differences between polarity states

sedimentation in large lakes processes associated with sedimentation in these lakes is in its infancy the large lakes of the world are precious resources that provide their nearby inhabitants with abundant fresh water food economical transpor tation and recreation they also provide additional benefits to the geologist unique paleoclimatic records and useful basins in which to test models of aquatic sedimentary processes this paper summarizes the global distribution oflarge lakes and focuses upon their geological attributes

continuous geomagnetic field models for the past 7 millennia 1 a new global data compilation 1 a global data set of archeomagnetic and paleomagnetic data covering the past 7000 years has been compiled it consists of 16 085 results of inclination 13 080 of declination and 3188 of intensity for the time span 5000 bc to 1950 ad declination and inclination data come partly from existing databases and partly from original literature a new global compilation of intensity data for the millennial scale is included data and dating uncertainties are discussed as we attempted to obtain an internally coherent data set the global distribution of the data is very inhomogeneous in both time and space all the data are compared to predictions from the previous 3000 year global model cals3k 1 this collection of data will be useful for global secular variation studies and geomagnetic field modeling although southern hemisphere data are still underrepresented in particular we will use it in a further study to update and extend the existing global model cals3k 1 the huge increase in data compared to the previous compilation will result in significant changes from current models as we might have missed some suitable data we encourage the reader to notify us about any data that have not been included yet and might fit in as improving our global millennial scale models remains our aim for the future the data files described in this paper are available from the earthref digital archive erda at http earthref org cgi bin erda cgi n 331

simulation study on evolution of coalbed methane reservoir in qinshui basin china a dynamic equilibrium model has been proposed to describe the coalbed methane concentration dissipation evolution process in coal including its generation storage and migration the model developed with a computational program has been applied to the qinshui basin china which allows to evaluate features of coal seam of the basin including coal quality and burial palaeo geothermal field and coal organic material maturation evolution history the simulation study was focused on coalbed methane concentration dissipation evolution history of the upper and lower main coal seams in the basin the results indicate that the whole evolution process can be divided into three stages at the first stage i e the primary concentration stage gas generation quantity and gas content were lower and only weak diffusion took place the second stage can be called the active concentration dissipation stage during this period coal organic material was matured at a higher rate generating a large amount of gas because of abnormal high palaeo geothermal field in the middle and late yanshan epoch as a result gas content in coal reservoir was higher and gas could be lost in different ways including diffusion cap outburst and permeation the third stage can be defined as the absolute dissipation stage at which coal organic material no longer generates gas meanwhile much gas was lost mainly by diffusion and partly by permeation simulation results further show that although the high gas generation led to active dissipation in the coal reservoir there still remains comparatively high gas content on the south and north ends of the qinshui basin due to the preserving geological conditions this suggests that these regions are favorable for coalbed methane exploitation which has been confirmed by recent geological exploitations in qinshui basin c 2007 published by elsevier b v

u pb th pb and ar ar geochronology from the southern sierras pampeanas argentina implications for the palaeozoic tectonic evolution of the western gondwana margin

structural evolution of the sierra de san luis eastern sierras pampeanas argentina implications for the proto andean margin of gondwana

construction of type curves of geomagnetic secular variation for dating lake sediments from east central north america type curves of palaeomagnetic secular variations of declination and inclination through the last 12 000 radiocarbon years have been constructed by combining data from the minnesota lakes with paral

the erieau excursion revisited paleomagnetic results from two cores collected from the central and eastern basins of lake erie contain the same remanence direction shift from positive to negative inclination at a depth of approx

orogenic development of the argentinian chilean andes during the palaeozoic the geological development of the basement of the argentinian chilean andes during the palaeozoic is characterized by an almost continuous structural metamorphic and plutonic mobility ultrabasic magmatism occurred only in a few regions terrigenic psammopelitic sequences are widespread at all times metamorphism is mostly of low to intermediate pressure but of variable temperature late palaeozoic high pressure metamorphism only took place near the present pacific coast there are about four culminations of orogenic activity varying in space and time from the mid cambrian to the mid ordovician from the silurian to the mid devonian during the early carboniferous and at the permian triassic boundary fold structures strike in variable directions at different times on the whole the pacific margin of gondwana consolidated continuously from the shield region in the e towards the pacific during the palaeozoic

the use of paleomagnetic curves for chrono stratigraphic correlation of late quaternary fluvial estuarine and lacustrine stratigraphic sequences in nipigon bay lake superior ontario canada abstract a study was carried out in nipigon bay lake superior to evaluate the use of paleomagnetic curves in correlating late quaternary stratigraphic sequences from a variety of sedimentary environments within a limited geographic area oscillations of the paleodeclination and paleoinclination curves result from secular variations of the earth s magnetic field with time so any correlation horizons picked on the character of either of these curves could be used for chrono stratigraphic correlation from one core to another within nipigon bay high resolution paleodeclination and paleoinclination curves were compiled for cores taken from six fluvial estuarine and lacustrine sites both the paleodeclination and the paleoinclination curves show marginal correlation for cores taken from within a specific sedimentary environment and reasonable correlation for cores taken from different sedimentary environments paleomagnetic curves can be used for chrono stratigraphic correlation and in addition show considerable promise as a method for absolute age dating of late quaternary stratigraphic sequences