an improved method for reconstructing the stratigraphy and bathymetry of continental margins application to the cenozoic tectonic and sedimentary history of the congo margin a number of techniques such as backstripping and forward modeling have been previously used to reconstruct the tectonic sedimentary and thermal history at passive margins still these techniques are generally inaccurate in places such as the west african margin where the stratigraphic record is disrupted by continuous faulting of the sediment pile caused by salt tectonics and by erosional unconformities the ability to reconstruct the stratigraphy salt thickness and water depth along profiles of these types of margins is important for determining the factors controlling the geological history of the margin and the evolution of hydrocarbon systems to reconstruct the stratigraphy paleowater depths and salt flowage on a profile across the congo margin we combined backstripping and palinspastic reconstruction this enabled us to restore the faulting and salt flowage and simultaneously to take into account the isostatic response of the lithosphere to sediment loading and unloading this method allowed us to estimate the paleowater depth as well as the stratigraphy and the geometry of the sedimentary section on the profile through time the determination of the regional isostatic response of the lithosphere is performed with the use of a new model to estimate the flexural rigidity of continental lithosphere to demonstrate this method we perform the cenozoic reconstruction of the congo margin the results yield a coherent geological history of the margin from the eocene to the present in the eocene the margin was a carbonate ramp with a deep seated shelf break 600 m during the eocene oligocene transition intermediate water depth oceanic currents triggered submarine erosion of the eocene slope and shelf from the miocene to the present we observe a large increase in the input of terrigenous clastic sediments as a result the shelf prograded 40 km across the eocene ramp as the clastic sediments prograded across the margin into the deep basin faulting of the sediment pile and salt withdrawal caused the formation of grabens in places where salt swells had previously formed finally the reconstruction suggests that the congo margin was uplifted by at least 330 m between the late oligocene and the middle miocene

hydrated silicate minerals on mars observed by the mars reconnaissance orbiter crism instrument phyllosilicates a class of hydrous mineral first definitively identified on mars by the omega observatoire pour la mineralogie l eau les glaces et l activitie instrument preserve a record of the interaction of water with rocks on mars global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy fe mg and al smectite clays this was interpreted to indicate that phyllosilicate formation occurred during the noachian the earliest geological era of mars and that the conditions necessary for phyllosilicate formation moderate to high ph and high water activity were specific to surface environments during the earliest era of mars s history here we report results from the compact reconnaissance imaging spectrometer for mars crism of phyllosilicate rich regions we expand the diversity of phyllosilicate mineralogy with the identification of kaolinite chlorite and illite or muscovite and a new class of hydrated silicate hydrated silica we observe diverse fe mg oh phyllosilicates and find that smectites such as nontronite and saponite are the most common but chlorites are also present in some locations stratigraphic relationships in the nili fossae region show olivine rich materials overlying phyllosilicate bearing units indicating the cessation of aqueous alteration before emplacement of the olivine bearing unit hundreds of detections of fe mg phyllosilicate in rims ejecta and central peaks of craters in the southern highland noachian cratered terrain indicate excavation of altered crust from depth we also find phyllosilicate in sedimentary deposits clearly laid by water these results point to a rich diversity of noachian environments conducive to habitability

experiment on estimating thermal conductivity of sedimentary rocks from oil well logging geologic note oil well are an important source of geothermal data for studying regional tectonics reconstructing the evolution of sedimentary basins and theorizing petroleum generation migration and accumulation a more satisfactory less laborious method of estimating the thermal conductivity of sedimentary rocks is badly needed the thermal conductivity of cores from two gas wells in france was measured and correlated with neutron porosity index sonic interval travel time bulk density and gamma ray logs to obtain reasonable predictions of conductivity data were segregated into lithologic groups such as sand shale carbonate shale and carbonate sand a set of regression coefficients in the equation that predicts the conductivity from the logs was calculated for each group t e correlation coefficients between the measured and predicted conductivities of the core samples were 0 81 0 75 and 0 61 respectively for the three lithologic groups the average percent difference between the measured and the calculated conductivities for the lithologies likely to be encountered in practice is 13 4 we expect this figure can be reduced to 10 by enlarging the data base for calculating the regression coefficients in the same basin or oil field the relative errors from well to well probably will be 6 or smaller because the lithology will be nearly homogeneous

thermal effects of zechstein salt and the early to middle jurassic hydrothermal event in the central polish basin deep gas potential in the polish basin may factor significantly in european geopolitics and thermal effects can influence that outcome there and elsewhere deep 3 km 9843 ft well data from the kujawy area of the central polish basin reveal average geothermal gradient 36c km thermal conductivity of mesozoic strata k 2 29 w m k and present day heat flow q 82 4 mw m2 that is 3 less than that obtained using the entire borehole the extrapolated surface temperature 6 2c is in good agreement with temperatures during the weichselian glaciation the thermal conductivity of the upper permian zechstein 4 89 w m k is in good agreement with values from the north sea and northern germany steady state heat flow theory one dimensional 1 d predicts present day temperature 199c at the base of zechstein cap rock at 6 km 19 685 ft depth in kujawy this is reduced just more than 10c by low zechstein thermal gradients 16 8c km because of thermal refraction two dimensional and three dimensional models of zechstein salt pillows can significantly negate this cooling effect however such effects appear absent in the kujawy wells studied a widespread early to middle jurassic 195 175 ma hydrothermal event appears to have reached maximum in the kujawy area a 455c paleotemperature at 7 km 22 966 ft depth carboniferous is predicted by 1 d conductive heat transfer however geologic evidence does not support this result the discrepancy is reconciled by convective heat transfer with upward fluid flow 3 3 10 10 m s 10 8 10 10 ft s resulting in a maximum paleotemperature of 273c at 7 km 22 966 ft depth despite a paleoheat flow of 142 mw m2 the trend of intensity of the hydrothermal event correlates with the present day heat flow trend hydrothermal event sites are subparallel to the major northwest southeast structural and regional heat flow trend whereas other sites as close as 14 km 45 932 ft and without hydrothermal event are not the decay of the hydrothermal event is consistent with localized cylindrical plumes 10 km 32 808 ft radius that cool by conduction results suggest a long term 185 m y structural control on heat flow linear regression to vitrinite paleotemperatures yields a 185 ma jurassic surface temperature of approximately 21 3c that is approximately 13c higher than the present day temperature for warsaw poland the duration of maximum reservoir and source rock paleotemperature 50 m y is contrary to the kinetics of nitrogen and co2 producing wells equilibrium thermodynamics predicts approximately 60 methane for present day kujawy reservoirs with considerable uncertainty that should be removed by anticipated new deep drilling

hydrothermal alteration and diagenesis of terrestrial lacustrine pillow basalts coordination of hyperspectral imaging with laboratory measurements abstract we investigate an outcrop of 187 ma lacustrine pillow basalts of the talcott formation exposed in meriden connecticut usa focusing on coordinated analyses of one pillow lava to characterize the aqueous history of these basalts in the hartford basin this work uses a suite of multidisciplinary measurements including hyperspectral imaging other spectroscopic techniques and chemical and mineralogical analyses from the microscopic scale up to the scale of an outcrop the phases identified in the sample are albite large iron oxides and titanite throughout calcite in vesicles calcic clinopyroxene aegirine and fe mg bearing clay in the rind and fine grained hematite and pyroxenes in the interior using imaging spectroscopy the chemistry and mineralogy results extend to the hand sample and larger outcrop from all of the analyses we suggest that the pillow basalts were altered initially after emplacement either by heated lake water or magmatic fluids at temperatures of at least 400 600 c and the calcic clinopyroxenes and aegirine identified in the rind are a preserved record of that alteration as the hydrothermal system cooled to slightly lower temperatures clays formed in the rind and during this alteration the sample oxidized to form hematite in the matrix of the interior and fe 3 in the pyroxenes in the rind during the waning stages of the hydrothermal system calcite precipitated in vesicles within the rind later diagenetic processes albitized the sample with albite replacing plagioclase lining vesicles and accreting onto the exterior of the sample this albitization or na metasomatism occurred when the lake within the hartford basin evaporated during a drier past climatic era resulting in na rich brines as ca rich plagioclase altered to albite ca was released into solution eventually precipitating as calcite in previously unfilled vesicles dominantly in the interior of the pillow coordinated analyses of this sample permit identification of the alteration phases and help synthesize the aqueous history of pillow lavas of the talcott formation these results are also relevant to mars where volcanically resurfaced open basin lakes have been found and this hartford basin outcrop may be a valuable analog for any potential volcano lacustrine interactions the results can also help to inform the utility and optimization of potentially complementary synergistic and uniquely suited techniques for characterization of hydrothermally altered terrains

estimating thermal conductivity in sedimentary basins using lithologic data and geophysical well logs a method for estimating in situ thermal conductivity profiles in oil and gas wells is advanced to rectify a major shortcoming in thermal analyses of sedimentary basins thermal conductivity estimates are made in a two stage procedure and are based on a model for the conductivity of mixtures and input data from lithological and geophysical logs first rock matrix conductivity for an arbitrary depth interval i e drill cuttings sample interval which is about 3 m is determined from the laboratory calibrated conductivities and volumetric representation of its individual lithologic components using a geometric mean model in situ conductivity is then estimated by a second application of the model correcting for temperature and porosity determined from geophysical logs the method is illustrated for three uinta basin utah wells that penetrate a series of tertiary sandstones shales and muddy carbonates detailed lithologic descriptions together with sonic and neutron logs were digitized and used for estimating in situ conductivity the validity of the method was tested by comparing the prediction against laboratory measurements on 565 samples from the same wells rock matrix thermal conductivity ranges from 1 6 to 6 8 w m k and is predicted within 20 of the actual measurement for 90 of the samples both in situ conductivity values and variations for a given lithologic unit are reduced at increased porosity and increased temperature thermal conductivity nomograms are presented as useful tools to predict directly the in situ thermal conductivit of a formation from a well log signal

thermal conductivity and well logs a case study in the paris basin summary the estimation of thermal conductivity from well logs is of great importance for all studies on thermal evolution of sedimentary basins the approach proposed here is to first interpret the well logs in terms of mineralogic composition and porosity and then to estimate the in silu conductivity from a mixing formula the geometric average of individual conductivities weighted by the volumetric proportion of each component the validity of the model has been widely verified by laboratory measurements on isotropic samples however there is a need for validation of such an approach for in situ conditions temperature data recorded at equilibrium in two wells of the paris basin offer a unique possibility of testing this approach in the case of a steady state conductive thermal rcgime fourier s law the conductivity must be proportional to the inverse of the temperature gradient the well logs are quantitatively interpreted in terms of mineralogic composition porosity and then thermal conductivity using a conductivity law calibrated on cuttings and cores laboratory measurements for three examples of well sections the computed thermal conductivity compares reasonably well with the inverse of the gradient for each of the three examples it is possible to define a depth range where the apparent heat flow is almost constant with depth and where the conductive regime seems to prevail this allows a refinement of the conductivity model with emphasis on the contribution of clays assuming that the conductivities of non clay end terms are known it is possible to obtain the conductivity of clay giving the best fit to the temperature measurements in the three cases the conductivity of clay 1 21 4 w m k is found to be lower than the assumed one 1 8 w m k i which probably indicates an anisotropy effect finally an empirical model where the bulk conductivity is expressed directly as a function of well logs is tested in one case the results obtained are quite compatible with the previous one but in the other two sections the stability and the physical meaning of this model are found to be questionable this could be due to the lack of constraints in the underlying implicit mineralogy model

thermophysical properties of the earth s crust in situ measurements from continental and ocean drilling knowledge of the variation of thermal conductivity and heat production with depth is critical to understanding the thermal state of the crust continental and oceanic drill holes provide unique opportunities for the calibration of empirical and theoretical models relating crustal thermal properties to physical and chemical properties these calibrations are based on more than 30 000 well log measurements of acoustic velocity both compressional and shear density porosity radioelement concentrations k u th and major element chemistry al si ca fe s mg na in formations ranging in age from 5 to 620 ma and in composition from granitic to gabbroic the mineralogical data available from induced gamma ray spectroscopy logs when combined with known mineral thermal conductivities in a model for the thermal conductivity of a crystalline aggregate enable the in situ application of a laboratory estimation technique and yield continuous conductivity profiles however mineralogy based conductivity models cannot account for the anisotropic conductivity observed in foliated metamorphic rocks a phonon conduction model which utilizes acoustic velocity and bulk density measurements is accurate within 15 in both isotropic and anisotropic formations of the upper continental crust and in oceanic crustal layers 2c and 3 in oceanic crustal layers 2a and 2b however the effects of fracturing on compressional and shear velocities lead to inaccurate results the heat flow heat production relationship which provides one method of determining subsurface heat production has well documented limitations allis 1979 and rybach and buntebarth 1982 1984 on the basis of laboratory measurements have proposed quantitative relationships between heat production and rock compositional and physical properties the well log k u and th data indicate that heat production can be predicted from compositional data within a factor of 2 or 3 predictions of heat production from acoustic velocity and bulk density measurements are only accurate to within an order of magnitude three factors account for these results 1 the natural variability of velocity and density for a given rock composition 2 the tendency of u and th to associate with secondary rather than primary minerals and 3 u and th redistribution through fluid flow and metamorphism thus seismic velocity based heat production profiles can at best be taken as first order estimates which may misrepresent the complexity of the continental crust however the correlation of formations of known heat production with subsurface structures when combined with a suite of existing techniques for estimating heat production may lead to more accurate results

in situ investigations of thermal conductivity heat production and past hydrothermal circulation in the cajon pass scientific drillhole california wireline logs from the cajon pass drillhole provide observations of crustal properties and processes near the san andreas fault mineralogical profiles developed from geochemical logs are combined with a technique for calculating thermal conductivity from the volume fractions of component minerals variations in the equilibrium temperature gradient correlate with conductivity contrasts and thus with lithology rather than with fluid circulation k u and th contents calculated from gamma spectroscopy logs yield heat production values which range from 1 3 to 2 4 w m averaging 1 8 w m in the section from 500 to 1800 m evidence for depletion of u relative to th raises the possibility of extensive fluid circulation in the past however discontinuity of depletion across faults suggests that the fluid regime responsible for u depletion predated san andreas faulting

seasonal latitudinal and diurnal distributions of whistler induced electron precipitation events the seasonal latitudinal and diurnal distributions of whistler induced electron precipitation events detected as subionospheric signal perturbations trimpi events have been studied by means of data sets acquired in 1982 1983 at palmer and siple stations antarctica the data sets substantially larger than any previously examined confirm previous indications of a broad 4 hour maximum in hourly event occurrence rates the peak was centered 1 2 hours after local midnight at palmer for the roughly north south argentina omega 12 9 khz path but was shifted several hours later for the 23 4 khz npm path which has a westerly arrival bearing at palmer the previously reported seasonal variation with peaks at the equinoxes was confirmed activity persisted in the austral winter particularly following a magnetic storm but in general occurred on fewer days and during shorter daily periods comparisons of occurrence data at siple l 4 3 and palmer l 2 4 for particular signal sources showed the number of days of activity to be larger at palmer by a factor of 2 or more comparisons of five months of simultaneous palmer and siple receptions of 21 4 khz nss signals on north south paths suggest that most of the events observed at siple occurred as the result of ionospheric perturbations relatively close to the l shell of palmer that is in the range l 2 3 this result is consistent with the expected variation with latitude of the energy of electrons precipitated due to equatorial gyroresonance at typical whistler frequencies

impact generated hydrothermal systems on earth and mars it has long been suggested that hydrothermal systems might have provided habitats for the origin and evolution of early life on earth and possibly other planets such as mars in this contribution we show that most impact events that result in the formation of complex impact craters i e 2 4 and 5 10 km diameter on earth and mars respectively are potentially capable of generating a hydrothermal system consideration of the impact cratering record on earth suggests that the presence of an impact crater lake is critical for determining the longevity and size of the hydrothermal system we show that there are six main locations within and around impact craters on earth where impact generated hydrothermal deposits can form 1 crater fill impact melt rocks and melt bearing breccias 2 interior of central uplifts 3 outer margin of central uplifts 4 impact ejecta deposits 5 crater rim region and 6 post impact crater lake sediments we suggest that these six locations are applicable to mars as well evidence for impact generated hydrothermal alteration ranges from discrete vugs and veins to pervasive alteration depending on the setting and nature of the system a variety of hydrothermal minerals have been documented in terrestrial impact structures and these can be grouped into three broad categories 1 hydrothermally altered target rock assemblages 2 primary hydrothermal minerals precipitated from solutions and 3 secondary assemblages formed by the alteration of primary hydrothermal minerals target lithology and the origin of the hydrothermal fluids strongly influences the hydrothermal mineral assemblages formed in these post impact hydrothermal systems there is a growing body of evidence for impact generated hydrothermal activity on mars although further detailed studies using high resolution imagery and multispectral information are required such studies have only been done in detail for a handful of martian craters the best example so far is from toro crater marzo g a davila a f tornabene l l dohm j m fairen a g gross c kneissl t bishop j l roush t l mckay c p 2010 icarus 208 667 683 we also present new evidence for impact generated hydrothermal deposits within an unnamed 32 km diameter crater 350 km away from toro and within the larger holden crater synthesizing observations of impact craters on earth and mars we suggest that if there was life on mars early in its history then hydrothermal deposits associated with impact craters may provide the best and most numerous opportunities for finding preserved evidence for life on mars moreover hydrothermally altered and precipitated rocks can provide nutrients and habitats for life long after hydrothermal activity has ceased

impact induced hydrothermal activity within the haughton impact structure arctic canada generation of a transient warm wet oasis field studies and analytical scanning electron microscopy indicate that a hydrothermal system was created by the interaction of water with hot impact generated rocks following formation of the 24 km diameter 23 ma haughton impact structure hydrothermal alteration is recognized in two settings within polymict impact breccias overlying the central portion of the structure and within localized pipes in impact generated concentric fault systems the intra breccia alteration comprises three varieties of cavity and fracture filling a sulfide with carbonate b sulfate and c carbonate these are accompanied by subordinate celestite barite fluorite quartz and marcasite selenite is also developed particularly in the lower levels of the impact breccia sheet the fault related hydrothermal alteration occurs in 1 7 m diameter subvertical pipes that are exposed for lengths of up 20 m the pipes are defined by a monomict quartz carbonate breccia showing pronounced fe hydroxide alteration associated sulfides include marcasite pyrite and chalcopyrite we propose three distinct stages in the evolution of the hydrothermal system 1 early stage 200 c with the precipitation of quartz vapor phase dominated 2 main stage 200 100 c with the development of a two phase vapor plus liquid zone leading to calcite celestite barite marcasite and fluorite precipitation and 3 late stage 100 c with selenite and fibroferrite development through liquid phase dominated precipitation we estimate that it took several tens of thousands of years to cool below 50 c following impact during this time haughton supported a 14 km diameter crater lake and subsurface water system providing a warmer wetter niche relative to the surrounding terrain the results reveal how understanding the internal structure of impact craters is necessary in order to determine their plumbing and cooling systems

geological overview and cratering model for the haughton impact structure devon island canadian high arctic the haughton impact structure has been the focus of systematic multi disciplinary field and laboratory research activities over the past several years regional geological mapping has refined the sedimentary target stratigraphy and constrained the thickness of the sedimentary sequence at the time of impact to 1880 m new 40ar 39ar dates place the impact event at 39 ma in the late eocene haughton has an apparent crater diameter of 23 km with an estimated rim final crater diameter of 16 km the structure lacks a central topographic peak or peak ring which is unusual for craters of this size geological mapping and sampling reveals that a series of different impactites are present at haughton the volumetrically dominant crater fill impact melt breccias contain a calcite anhydrite silicate glass groundmass all of which have been shown to represent impact generated melt phases these impactites are therefore stratigraphically and genetically equivalent to coherent impact melt rocks present in craters developed in crystalline targets the crater fill impactites provided a heat source that drove a post impact hydrothermal system during this time haughton would have represented a transient warm wet microbial oasis a subsequent episode of erosion during which time substantial amounts of impactites were removed was followed by the deposition of intracrater lacustrine sediments of the haughton formation during the miocene present day intracrater lakes and ponds preserve a detailed paleoenvironmental record dating back to the last glaciation in the high arctic modern modification of the landscape is dominated by seasonal regional glacial and niveal melting and local periglacial processes the impact processing of target materials improved the opportunities for colonization and has provided several present day habitats suitable for microbial life that otherwise do not exist in the surrounding terrain

using neural networks to predict thermal conductivity from geophysical well logs summary we present a new approach based on neural networks to predict the thermal conductivity of sedimentary rocks from a set of geophysical well logs this method is calibrated on ocean drilling program odp data which provide several thousands of conductivity measurements combined with five geophysical well logs sonic density neutron porosity resistivity and gamma ray this data set is used to train multilayer perceptrons mlp and to find an empirical relationship between well logs mlp inputs and thermal conductivity mlp output validation tests suggest that mlp provide better estimates of thermal conductivity within 15 per cent confidence level than classical linear models and still give satisfying results with sets of only four well logs if neutron porosity is included in two odp sites 863b and 1109d mlp s predictions are compared to conventional mixing methods although this latter technique gives reliable results provided that rocks description is precise enough the mlp is more straightforward does not need any extra parameter and makes predictions in good agreement with the experimental trends this method will be useful in the estimation of heat flow from data acquired in scientific and industrial boreholes

spaceborne visible and thermal infrared lithologic mapping of impact exposed subsurface lithologies at the haughton impact structure devon island canadian high arctic applications to mars this study serves as a proof of concept for the technique of using visible near infrared vnir short wavelength infrared swir and thermal infrared tir spectroscopic observations to map impact exposed subsurface lithologies and stratigraphy on earth or mars the topmost layer three subsurface layers and undisturbed outcrops of the target sequence exposed just 10 km to the northeast of the 23 km diameter haughton impact structure devon island nunavut canada were mapped as distinct spectral units using landsat 7 etm vnir swir and aster vnir swir tir multispectral images spectral mapping was accomplished by using standard image contrast stretching algorithms both spectral matching and deconvolution algorithms were applied to image derived aster tir emissivity spectra using spectra from a library of laboratory measured spectra of minerals arizona state university and whole rocks ward s these identifications were made without the use of a priori knowledge from the field i e a blind analysis the results from this analysis suggest a sequence of dolomitic rock in the crater rim limestone wall gypsum rich carbonate floor and limestone again central uplift these matched compositions agree with the lithologic units and the pre impact stratigraphic sequence as mapped during recent field studies of the haughton impact structure by osinski et al 2005a further conformation of the identity of image derived spectra was confirmed by matching these spectra with laboratory measured spectra of samples collected from haughton the results from the blind remote sensing methods used here suggest that these techniques can also be used to understand subsurface lithologies on mars where ground truth knowledge may not be generally available

the stability of sulfate and hydrated sulfate minerals near ambient conditions and their significance in environmental and planetary sciences abstract sulfate and hydrated sulfate minerals are abundant and ubiquitous on the surface of the earth and also on other planets and their satellites the humidity buffer technique has been applied to study the stability of some of these minerals at 0 1 mpa in terms of temperature relative humidity space on the basis of hydration dehydration reversal experiments updated phase relations in the binary system mgso 4 h 2 o are presented as an example to show how reliable thermodynamic data for these minerals could be obtained based on these experimental results and thermodynamic principles this approach has been applied to sulfate and hydrated sulfate minerals of other metals including fe both ferrous and ferric zn ni co cd and cu metal sulfate salts play important roles in the cycling of metals and sulfate in terrestrial systems and the number of phases extends well beyond the simple sulfate salts that have thus far been investigated experimentally the oxidation of sulfide minerals particularly pyrite is a common process that initiates the formation of efflorescent metal sulfate minerals also the overall abundance of iron bearing sulfate salts in nature reflects the fact that the weathering of pyrite or pyrrhotite is the ultimate source for many of these phases many aspects of their environmental significance are reviewed particularly in acute effects to aquatic ecosystems related to the dissolution of sulfate salts during rain storms or snow melt events hydrous mg ca and fe sulfates were identified on mars with wide distribution and very large quantities at many locations on the basis of spectroscopic observations from orbital remote sensing and surface explorations by rovers however many of these findings do not reveal the detailed information on the degree of hydration that is essential for rigorous interpretation of the hydrologic history of mars laboratory experiments on stability fields reactions pathways and reaction rates of hydrous sulfates likely to be found on mars enhance our understanding of the degrees of hydration of various sulfates that should currently exist on mars at various seasons and locations and during various atmospheric pressure and obliquity periods two sets of systematic experiments were described one on hydrous mg sulfates and the other on hydrous fe 3 sulfates also their implications to mars sulfates mineralogy were discussed

identification of carbonate rich outcrops on mars by the spirit rover decades of speculation about a warmer wetter mars climate in the planet s first billion years postulate a denser co2 rich atmosphere than at present such an atmosphere should have led to the formation of outcrops rich in carbonate minerals for which evidence has been sparse using the mars exploration rover spirit we have now identified outcrops rich in magnesium iron carbonate 16 to 34 weight percent in the columbia hills of gusev crater its composition approximates the average composition of the carbonate globules in martian meteorite alh 84001 the gusev carbonate probably precipitated from carbonate bearing solutions under hydrothermal conditions at near neutral ph in association with volcanic activity during the noachian era

a case study of impact induced hydrothermal activity the haughton impact structure devon island canadian high arctic the well preserved state and excellent exposure at the 39 ma haughton impact structure 23 km in diameter allows a clearer picture to be made of the nature and distribution of hydrothermal deposits within mid size complex impact craters a moderate to low temperature hydrothermal system was generated at haughton by the interaction of groundwaters with the hot impact melt breccias that filled the interior of the crater four distinct settings and styles of hydrothermal mineralization are recognized at haughton a vugs and veins within the impact melt breccias with an increase in intensity of alteration towards the base b cementation of brecciated lithologies in the interior of the central uplift c intense veining around the heavily faulted and fractured outer margin of the central uplift and d hydrothermal pipe structures or gossans and mineralization along fault surfaces around the faulted crater rim each setting is associated with a different suite of hydrothermal minerals that were deposited at different stages in the development of the hydrothermal system minor early quartz precipitation in the impact melt breccias was followed by the deposition of calcite and marcasite within cavities and fractures plus minor celestite barite and fluorite this occurred at temperatures of at least 200 c and down to 100 120 c hydrothermal circulation through the faulted crater rim with the deposition of calcite quartz marcasite and pyrite occurred at similar temperatures quartz mineralization within breccias of the interior of the central uplift occurred in two distinct episodes 250 down to 90 c and 80 c appreciation of the structural features of impact craters has proven to be key to understanding the distribution of hydrothermal deposits at haughton

introduction to special issue on integrated basin studies ibs a european commission dgxii project this issue contains papers issued from the integrated basin studies project ibs which is part of a larger program of the european commission dgxii entitled geosciences ii the ibs project ec contract jou2 ct92 0110 originated in geosciences consultation meetings the first of them being held in strasbourg in june 1989 under the auspices of mr hubert curien former french minister for research and technology and the subsequent meeting being held in brussels these consultation meetings have resulted in the conclusion that a main axis of future research in geosciences should be the study of sedimentary basins upstream of industrial activities mainly the oil and gas industry but also water resources management the mining industry the storage of undesirable products and coastal engineering they also resulted in the conclusion that future research on sedimentary basins should fulfill two requirements integration of disciplines and modelling such a conclusion may now seem trivial but was not so generally accepted at that time in this spirit the ibs project was designed to provide the oil and gas industry with a new generation of models for basin formation basin evolution and basin fill architecture from basin scale to reservoir scale its main objectives are the linkage of crust thermomechanical behaviour to basin formation and deformation mechanics and the corresponding modelling the quantification of tectonic control on the sedimentary record and the analysis of compaction and mass and heat transfer the ibs strategy is to link subsurface data to field data and an important part of the project is devoted to thematic field studies in european sedimentary basins of different tectonic styles taken as natural laboratories basin research has gone through a rapid evolution during the last decade in particular through the development of new acquisition and processing methods for seismic data and advances in drilling technology modelling provides an important tool to analyse different aspects of basin formation processes and find their tectonic expression in the basin fill the need for 3 d modelling techniques and models capable of linking processes operating on basinwide to subbasin scales is increasingly recognized and a significant effort has been made in the ibs project to develop a new generation of basin formation models coping with these needs see also cloetingh et al 1993a van wees and cloetingh 1994 as many data required to test these models reside in industrial companies ibs has promoted a closer link between academic research and basin studies carried out by industry the participation of the petroleum industry has been vital in this project and ibs has been able to establish a well functioning system of cooperation that not only facilitated data access but most important guaranteed the suitability of the end products of the project this has led to an intensive exchange of modelling concepts and data sets between industry and academia the ibs project has also used extensively the international lithosphere program task force origin of sedimentary basins see cloetingh sassi and task force team 1994 cloetingh et al 1993a b 1994 to implement planning and to discuss preliminary results it also builds partly on joint research through the european commission tempus and peco programs on pannonian basin studies horvath 1993 van balen and cloetingh 1995 van balen et al 1995 horvath and cloetingh 1995 a stimulating aspect of the activity of the ibs group is the creation of a research network in the corresponding field of knowledge which comprises now 30 teams belonging to eight european countries england france germany hungary norway spain switzerland and the netherlands this demonstrates the capacity of the procedures used by the dgxii of the european community to formulate a really european research space phd students and young researchers form an important component of the research groups

finding mineralogically interesting targets for exploration from spatially coarse visible and near ir spectra abstract spectroscopic studies of analog terrestrial mineral assemblages are necessary to develop criteria to identify similar environments on mars we use visible near infrared vnir laboratory field and remotely acquired spectral data to identify the iron bearing and hydrous minerals of rio tinto spain an astrobiological analog mineralogy evolves from iron sulfate and oxide rich jarosite rozenite gypsum schwertmannite copiapite goethite and hematite assemblages in young sediments to hydrated iron oxides in preserved terraces using spectra from the rio tinto we examine one of the key challenges of extraterrestrial exploration how to identify promising targets from spatially coarse data for in situ investigation we apply an index to quantify the expression of spectral diversity as a function of spatial scale from hand sample to landscape to validate this method for use at the decimeter orbital scale we apply the index to cm scale point spectra and meter scale gridded spectra collected in the field this exercise in spatial scaling gives increased confidence in the ability of the spectral variance index svi method to locate regions with increased mineral diversity from remotely sensed data we divide the remotely sensed data into 25 25 pixel 200 m 200 m cells and calculate the average mean albedo and spectral variance over all wavelengths for each cell we next calculate the expected variance for each cell with a linear regression between mean and spectral variance the number of standard deviations of each cell s spectral variance is from the expected variance is the svi value we locate 20 areas with high svi values within the tailing piles and along wide riverbanks downstream of the active mine this method uses spatially coarse vnir spectra to recognize areas in rio tinto that would be ideal targets for future field exploration and could also be applied to mars orbital spectral datasets such as omega and crism

ancient impact and aqueous processes at endeavour crater mars the rover opportunity has investigated the rim of endeavour crater a large ancient impact crater on mars basaltic breccias produced by the impact form the rim deposits with stratigraphy similar to that observed at similar sized craters on earth highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits gypsum rich veins cut sedimentary rocks adjacent to the crater rim the gypsum was precipitated from low temperature aqueous fluids flowing upward from the ancient materials of the rim leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate rich sandstones of the meridiani region

determination of thermal conductivity for deep boreholes two methods for thermal conductivity determinations on rock cores and fragments were tested on a suite of samples from the kontinentales tiefbohrprogramm der bundesrepublik deutschland ktb superdeep drill hole in germany they were also compared with estimates of thermal conductivity using the mineral composition of the rock and physical well logs and with in situ thermal conductivity measurements laboratory methods provide reasonably precise determinations of the thermal conductivities of both solid core 5 and drill cuttings 10 at room temperature and pressure the most common methods presently used for crystalline rocks are the steady state divided bar db technique and the transient half space line source ls sample preparation and measurement times are comparable for the db and ls with sample preparation being more time consuming on average for isotropic rocks there is little to choose from between the two methods which both give reliable values of conductivity in the vertical direction the ls is easier to set up and use in field laboratory situations which renders it the preferred method for field reconnaissance the gneissic crystalline rocks penetrated by the ktb boreholes typically have anisotropy of the order of 10 20 the db provides unambiguous values of conductivity in a given direction so its use is preferable for obtaining both principal conductivities and the vertical component anisotropy can be estimated using ls measurements in many different directions but the potential for large random errors is much greater than with the more straightforward db approach for deep research wells the difficulties of extrapolating laboratory results to in situ conditions particularly temperature present additional obstacles to determining heat flow laboratory measurements of water saturated samples under in situ conditions combined with in situ measurements and judicious use of calculations based on mineralogy and well log derived physical properties can aid in the accurate characterization of thermal conductivity in deep wells the application of different methods helped to link variations of heat flow with depth in the ktb hole to the anisotropy of thermal conductivity or thermal refraction and thus allowed the calculation of background heat flux in this geologically complex area

impact thermochronology and the age of haughton impact structure canada 1 most successful efforts to determine the ages of impact events are based on the isotope geochronology of crystalline or glassy impact melts studies of impact sites on earth show that many form without significant melt production meaning that traditional geochronologic approaches can yield unsatisfying results we describe here an alternative approach based on theoretical calculations that even brief thermal events related to impact can reset the isotopic systematics of unmelted target rocks thermochronometers based on the production of radiogenic 4he in accessory minerals are particularly amenable to complete resetting by impact and should yield robust impact ages if helium systematics are not further disturbed during post impact thermal events we illustrate the utility of this method through a presentation of a new zircon u th he date for the haughton impact structure canada of 23 5 2 0 ma

mineralogy of juventae chasma sulfates in the light toned mounds mafic minerals in the bedrock and hydrated silica and hydroxylated ferric sulfate on the plateau 1 juventae chasma contains four light toned sulfate bearing mounds denoted here as a d from west to east inside the trough mafic outcrops at the base of the mounds and in the wall rock and light toned layered deposits of opal and ferric sulfates on the plateau hyperspectral visible near infrared compact reconnaissance imaging spectrometer for mars crism spectra were used to identify monohydrated and polyhydrated sulfate phs outcrops of layered material on the bright mounds most of the monohydrated sulfate signatures closely resemble those of szomolnokite feso4 h2o characterized by a water band near 2 08 m while some areas exhibit spectral features more similar to those of kieserite mgso4 h2o with a band centered closer to 2 13 m the largest phs outcrops occur on the top of mound b and their spectral features are most consistent with ferricopiapite melanterite and starkeyite but a specific mineral cannot be uniquely identified at this time coordinated analyses of crism maps mars orbiter laser altimeter elevations and high resolution imaging science experiment images suggest that mounds a and b may have formed together and then eroded into separate mounds while mounds c and d likely formed separately mafic minerals low ca pyroxene high ca pyroxene and olivine are observed in large 2 10 km wide outcrops in the wall rock and in smaller outcrops 50 500 m across at the floor of the canyon most of the wall rock is covered by at least a thin layer of dust and does not exhibit strong features characteristic of these minerals the plateau region northwest of juventae chasma is characterized by an abundance of light toned layered deposits one region contains two spectrally unique phases exhibiting a highly stratified terraced pattern crism spectra of one unit eroded into swirling patterns with arc like ridges exhibit a narrow 2 23 m band assigned to hydroxylated ferric sulfate a thin layer of a fractured material bearing an opaline silica phase is observed at the contact between the older plateau unit and the younger hydroxylated ferric sulfate bearing light toned layered deposits hydrothermal processes may have produced an acidic environment that fostered formation of the hydrated silica and hydroxylated ferric sulfate units

revised crism spectral parameters and summary products based on the currently detected mineral diversity on mars the investigation of hyperspectral data from the mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism and the observatoire pour la mineralogie l eau les glaces et l activitie omega on mars express has revealed an increasingly diverse suite of minerals present on the martian surface a revised set of 60 spectral parameters derived from corrected spectral reflectance at key wavelengths in crism targeted observations and designed to capture the known diversity of surface mineralogy on mars is presented here as summary products some of the summary products have strong heritage to omega spectral parameter calculations this paper also presents newly derived parameters that highlight locations with more recently discovered spectral signatures type locations for the diversity of currently identified mineral spectral signatures have been compiled into a library presented in this work our analysis indicates that the revised set of summary products captures the known spectral diversity of the surface and successfully highlights and differentiates between locations with differing spectral signatures the revised spectral parameter calculations and related products provide a useful tool for scientific interpretation and for future mission landing site selection and operations

major and trace element composition of copiapite group minerals and coexisting water from the richmond mine iron mountain california copiapite group minerals of the general formula ar4 so4 6 oh 2d nh2o where a is predominantly mg fe 2 or 0 67al 3 r is predominantly fe 3 and n is typically 20 are among several secondary hydrous fe sulfates occurring in the inactive mine workings of the massive sulfide deposit at iron mountain ca a usepa superfund site that produces extremely acidic drainage samples of copiapite group minerals some with coexisting water were collected from the richmond mine approximately 200 ml of brownish pore water with a ph of 0 9 were extracted through centrifugation from a 10 l sample of moist copiapite group minerals taken from pyritic muck piles the pore water is extremely rich in ferric iron fe 3 149 g l 1 f et 162 g l 1 and has a density of 1 52 g ml 1 the composition of the pore water is interpreted in the context of published phase relations in the fe2o3 so3 h2o system and previous work on the chemistry of extremely acid mine waters and associated minerals in the richmond mine two distinct members of the copiapite mineral group were identified in the samples with coexisting water 1 abundant magnesiocopiapite consisting of platy crystals 10 to 50 am and 2 minor aluminocopiapite present as smaller platy crystals that form spheroidal aggregates the average composition n 5 of the magnesiocopiapite is mg0 90fe 2 zn0 02cu0 01 p 1 10 fe 3 al0 09 p 3 92 so4 6 00 oh 1 96d 20h2o bulk compositions determined by digestion and wet chemical analysis are consistent with the microanalytical results these results suggest that magnesiocopiapite is the least soluble member of the copiapite group under the prevailing conditions micro pixe analysis indicates that the copiapite group minerals in this sample sequester zn average 1420 ppm with lesser amounts of cu average 270 ppm and as average 64 ppm d 2004 elsevier b v all rights reserved

hydrothermal alteration at the lonar lake impact structure india implications for impact cratering on mars the 50 000 year old 1 8 km diameter lonar crater is one of only two known terrestrial craters to be emplaced in basaltic target rock the 65 million year old deccan traps the composition of the lonar basalts is similar to martian basaltic meteorites which establishes lonar as an excellent analogue for similarly sized craters on the surface of mars samples from cores drilled into the lonar crater floor show that there are basaltic impact breccias that have been altered by post impact hydrothermal processes to produce an assemblage of secondary alteration minerals microprobe data and x ray diffraction analyses show that the alteration mineral assemblage consists primarily of saponite with minor celadonite and carbonate thermodynamic modeling and terrestrial volcanic analogues were used to demonstrate that these clay minerals formed at temperatures between 130 c and 200 c by comparing the lonar alteration assemblage with alteration at other terrestrial craters we conclude that the lonar crater represents a lower size limit for impact induced hydrothermal activity based on these results we suggest that similarly sized craters on mars have the potential to form hydrothermal systems as long as liquid water was present on or near the martian surface furthermore the fe rich alteration minerals produced by post impact hydrothermal processes could contribute to the minor iron enrichment associated with the formation of the martian soil

carbonate mineral water interactions in sulfide rich mine tailings the chemical composition and mineralogy of coatings on carbonate minerals from mine tailings have been studied using aqueous geochemical methods time of flight laser ionization mass spectrometry tof lims and transmission electron microscopy tem the goal is to study major and trace element partitioning between the aqueous and solid phase and to infer mechanisms that control the concentrations of elements in the pore water of sulfide rich mine tailings pore water samples and carbonate mineral grains were collected from four geochemically distinct zones within the tailings oxidation of sulfide minerals near the surface results in a large range in pore water ph 3 85 to 6 98 and aqueous concentrations of metals and sulfate with increasing depth in the tailings mineral water interactions lead to increasing ph and decreasing concentrations of metals and sulfate calculated mineral saturation indices trends in the abundance of ca fe mg and mn in tof lims profiles through the secondary coatings and electron diffraction patterns obtained from the coatings suggest that precipitation dissolution of jarosite group minerals gypsum goethite akaganeite amorphous fe oxyhydroxides and siderite control the aqueous ca fe na k and so4 concentrations the occurrence of secondary coatings on primary minerals is widespread and reactions with the secondary minerals rather than the primary mineral substrate probably represent the principal controls on trace element distributions in the pore water the data indicate that adsorption surface complexation and co precipitation reactions are important controls on the concentrations of trace elements in the pore water the occurrence of siderite coatings on the surface of ankerite grains suggests that fe bearing dolomite structure carbonate minerals dissolve incongruently this corroborates inferences made by previous workers that solubility differences between calcite and siderite lead to calcite dissolution and siderite precipitation during acid neutralization the accumulation of secondary coatings will diminish the rate of mineral dissolution reactions involving the primary minerals consequently the use of kinetic rate constants obtained from the literature for simulating the dissolution of primary mineral phases such as the carbonates and alumino silicates will likely overestimate the actual rates

geothermal regime and thermal history of the llanos basin colombia the llanos basin is a siliciclastic foreland sub andean sedimentary basin located in colombia between the cordillera oriental and the guyana precambrian shield data on bottom hole temperature lithology porosity and vitrinite reflectance from all 318 wells drilled in the central and southern parts of the basin were used to analyze its geothermal regime and thermal history average geothermal gradients in the llanos basin decrease generally with depth and westward toward the fold and thrust belt the geothermal regime is controlled by a moderate generally westward decreasing basement heat flow by depositional and compaction factors and in places by advection by formation waters compaction leads to increased thermal conductivity with depth whereas westward downdip flow in deep sandstone formations may exert a cooling effect in the central western part of the basin vitrinite reflectance variation with depth shows a major discontinuity at the pre cretaceous unconformity areally vitrinite reflectance increases southwestward in paleozoic strata and northwestward in post paleozoic strata these patterns indicate that the thermal history of the basin robably includes three thermal events that led to peaks in oil generation a paleozoic event in the southwest a failed cretaceous rifting event in the west and an early tertiary back arc event in the west rapid cooling since the last thermal event is possibly caused by subhorizontal subduction of cold oceanic lithospheric plate

geochemical and mineralogical aspects of sulfide mine tailings abstract tailings generated during processing of sulfide ores represent a substantial risk to water resources the oxidation of sulfide minerals within tailings deposits can generate low quality water containing elevated concentrations of so 4 fe and associated metal loid s acid generated during the oxidation of pyrite fes 2 pyrrhotite fe 1 x s and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate oxy hydroxide and silicate minerals the extent of acid neutralization and therefore pore water ph is a principal control on the mobility of sulfide oxidation products within tailings deposits metals including fe iii cu zn and ni often occur at high concentrations and exhibit greater mobility at low ph characteristic of acid mine drainage amd in contrast hydr oxyanion forming elements including as sb se and mo commonly exhibit greater mobility at circumneutral ph associated with neutral mine drainage nmd these differences in mobility largely result from the ph dependence of mineral precipitation dissolution and sorption desorption reactions cemented layers of secondary oxy hydroxide and hydroxy sulfate minerals referred to as hardpans may promote attenuation of sulfide mineral oxidation products within and below the oxidation zone hardpans may also limit oxygen ingress and pore water migration within sulfide tailings deposits reduction oxidation redox processes are another important control on metal loid mobility within sulfide tailings deposits reductive dissolution or transformation of secondary oxy hydroxide phases can enhance fe mn and as mobility within sulfide tailings production of h 2 s via microbial sulfate reduction may promote attenuation of sulfide oxidation products including fe zn ni and tl via metal sulfide precipitation understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings

evidence for the shock melting of sulfates from the haughton impact structure arctic canada abstract sulfate minerals can form an important component of the matrix to carbonate rich impact melt breccias at the 24 km diameter 23 ma haughton impact structure arctic canada the textural and chemical features of the matrix forming sulfates indicate that these phases in addition to co existing carbonates and silicates crystallized directly from an impact generated melt evidence for this includes 1 the matrix supported nature of the crater fill lithologies 2 sulfate carbonate silicate liquid immiscible textures 3 possible quench textures in anhydrite and 4 flow textures developed between anhydrite and silicate rich glasses further supporting evidence includes the presence of si al and mg in the anhydrite structure which were probably trapped by quenching from a melt irregular blebs and globules of shock melted carbonates within anhydrite also suggest a common origin for the two phases field studies reveal that clasts of anhydrite bearing target material are also present in the crater fill deposits several clasts of anhydrite quartz lithologies exhibit evidence for incipient shock melting in both phases previous assumptions about the response of sulfates and carbonates to hypervelocity impact i e lack of melting may therefore be incorrect

diurnal variation of burst precipitation effects on subionospheric vlf lf signal propagation near l 2 burst precipitation effects on subionospheric vlf lf signal propagation are studied using data recorded at palmer station antarctica l 2 4 between march 3 and april 7 1983 relatively abrupt signal amplitude changes known as trimpi effects were observed in conjunction with magnetospheric whistlers which are inferred to induce electron precipitation that in turn causes enhanced ionization at the 80 to 90 km altitude level earlier findings that trimpi effects occur predominantly under nighttime ionospheric conditions were confirmed by comparing the sunrise sunset terminator position with perturbation activity on three vlf lf signal paths for which the arrival bearings range from magnetic north to west events were found to occur on 70 of the observing nights signal paths making larger angles with the terminator were used to deduce that most events were caused by ionospheric effects occurring within 1000 km of palmer station some events were observed after sunrise over the observing station apparently due to precipitation in dark regions as far as 1800 km away observed differences between two different paths in the occurrence of this postsunrise continuation of trimpi events suggest that the trimpi event activity rate decreases below l 2 this may be due to a reduction in whistler activity and or lower particle scattering efficiency the average hourly occurrence rate of transmitter nss events on the 11 most active nights studied increased from sunset to near midnight and then remained at a roughly constant level until sunrise the influence of the whistler rate and of whistler path locations on trimpi effects is clearly important and requires further study

compositional heterogeneity of impact melt rocks at the haughton impact structure canada implications for planetary processes and remote sensing connecting the surface expression of impact crater related lithologies to planetary or regional subsurface compositions requires an understanding of material transport during crater formation here we use imaging spectroscopy of 6 clast rich impact melt rock outcrops within the well preserved 23 5 ma 23 km diameter haughton impact structure canada to determine melt rock composition and spatial heterogeneity we compare results from outcrop to outcrop using clasts groundmass and integrated clast groundmass compositions as tracers of transport during crater fill melt rock formation and cooling supporting laboratory imaging spectroscopy analyses of 91 melt bearing breccia and clast samples and microscopic x ray fluorescence elemental mapping of cut samples paired with spectroscopy of identical surfaces validate outcrop scale lithological determinations results show different clast rich impact melt rock compositions at three sites kilometers apart and an inverse correlation between silica rich sandstone gneiss and phyllosilicate rich shales and gypsum rich rocks that suggests differences in source depth with location in the target stratigraphy gypsum is primarily sourced from 1 km depth while gneiss is from 1 8 km depth sandstone from 1 3 km and shales from 1 6 1 7 km observed heterogeneities likely result from different excavation depths coupled with rapid quenching of the melt due to high content of cool clasts results provide quantitative constraints for numerical models of impact structure formation and give new details on melt rock heterogeneity important in interpreting mission data and planning sample return of impactites particularly for bodies with impacts into sedimentary and volatile bearing targets e g mars and ceres

hyperspectral mapping of alteration assemblages within a hydrothermal vug at the haughton impact structure canada meteorite impacts on earth and mars can generate hydrothermal systems that alter the primary mineralogies of rocks and provide suitable environments for microbial colonization we investigate a calcite marcasite bearing vug at the 23 km diameter haughton impact structure devon island nunavut canada using imaging spectroscopy of the outcrop in the field 0 65 1 1 m and samples in the laboratory 0 4 2 5 m point spectroscopy 0 35 2 5 m major element chemistry and x ray diffraction analyses the mineral assemblages mapped at the outcrop include marcasite marcasite with minor gypsum and jarosite fibroferrite and copiapite with minor gypsum and melanterite gypsum fe3 oxides and jarosite and calcite gypsum clay microcline and quartz hyperspectral mapping of alteration phases shows spatial patterns that illuminate changes in alteration conditions and formation of specific mineral phases marcasite formed from the postimpact hydrothermal system under reducing conditions while subsequent weathering oxidized the marcasite at low temperatures and water rock ratios the acidic fluids resulting from the oxidation collected on flat lying portions of the outcrop precipitating fibroferrite copiapite that assemblage then likely dissolved and the changing chemistry and ph resulting from interaction with the calcite rich host rock formed gypsum bearing red coatings these results have implications for understanding water rock interactions and habitabilities at this site and on mars

akaganeite β feooh precipitation in inland acid sulfate soils of south western new south wales nsw australia abstract the prevalence of sulphidic sediments in inland wetlands has been only recently recognized in many parts of the world including australia the exposure of sulphidic sediments in these wetlands due to natural and human induced drying events has resulted in the oxidation of iron sulfide minerals the formation of secondary iron minerals characteristic of acid sulfate soils and the release of highly acidic solutions the objective of this study was to determine the mineralogy and morphology of sediments collected from the oxidized surface horizon 0 5 cm of an inland acid sulfate soil located in south western new south wales nsw australia random powder x ray diffraction xrd transmission electron microscopy tem and scanning transmission electron microscopy combined with energy dispersive x ray spectroscopy stem eds techniques were used to characterize the minerals present in these sediments akaganeite was identified as the major mineral phase in the sediments k jarosite was also determined in small amounts in some sediments the xrd patterns of sequentially washed e pure water 0 01 m hcl 0 01 m edta sediment samples showed all akaganeite peaks the rietveld refinement of these patterns also revealed a predominance of akaganeite the chemical analyses of the original and washed sediments using stem eds clearly showed the presence of akaganeite as a pure mineral phase with an average fe cl mole ratio of 6 7 and a structural formula of fe 8 o 8 oh 6 8 cl 1 2 these findings show that the extreme saline acidic solutions ph 2 ec 216 ds m at the bottle bend lagoon provide ideal conditions for the crystallization of this rarely forming mineral

impact generated carbonate melts evidence from the haughton structure canada evidence is presented for the melting of dolomite rich target rocks during formation of the 24 km diameter 23 ma haughton impact structure on devon island in the canadian high arctic field studies and analytical scanning electron microscopy reveal that the s 200 m thick crater fill deposit which currently covers an v60 km 2 area in the center of the structure comprises fragmented target rocks set within a carbonate silicate matrix the silicate component of the matrix consists of si al mg rich glass the carbonate component is microcrystalline calcite containing up to a few wt si and al the calcite also forms spherules and globules within the silicate glass with which it develops microtextures indicative of liquid immiscibility dolomite clasts exhibit evidence of assimilation and may show calcite and rare dolomite overgrowths some clasts are penetrated by calcite and silicate injections along with the carbonate silicate glass textures the presence of pigeonite and spinifex textured diopside suggests that the matrix to the crater fill deposit was originally molten and was rapidly cooled this indicates that the impact event that generated haughton caused fusion of the predominantly dolomitic target rocks it appears that the ca mg component of the dolomite may have dissociated with mg entering the silicate melt phase while the ca component formed a caco3 dominant melt the silicates were derived by the fusion of lower paleozoic sandstones siltstones shales and impure dolomites evidence for melting is corroborated by a review of theoretical and experimental work which shows that caco3 melts at s 10 gpa and s 2000 k instead of dissociating to release co2 this work indicates that carbonate rich sedimentary targets may also undergo impact melting and that the volume of co2 released into the atmosphere during such events may be considerably less than previously estimated fl 2001 elsevier science b v all rights reserved

the opportunity rover s athena science investigation at meridiani planum mars the mars exploration rover opportunity has investigated the landing site in eagle crater and the nearby plains within meridiani planum the soils consist of fine grained basaltic sand and a surface lag of hematite rich spherules spherule fragments and other granules wind ripples are common underlying the thin soil layer and exposed within small impact craters and troughs are flat lying sedimentary rocks these rocks are finely laminated are rich in sulfur and contain abundant sulfate salts small scale cross lamination in some locations provides evidence for deposition in flowing liquid water we interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water followed by evaporation exposure and desiccation hematite rich spherules are embedded in the rock and eroding from them we interpret these spherules to be concretions formed by postdepositional diagenesis again involving liquid water

an impact origin for hydrated silicates on mars a synthesis 1 recent mars orbiting spectrometers continue to detect surface materials containing hydrated silicates particularly clays and amorphous phases e g silica glasses concentrated within the heavily cratered noachian highlands crust this paper provides a review summary and synthesis of observations from terrestrial impact structures with current martian data it is suggested that numerous and frequent impacts into the volatile rich silicate crust of mars through direct and indirect impact generated mechanisms represent a plausible hypothesis that can explain the widespread distribution of hydrated silicates in the surface and subsurface of the heavily cratered noachian highlands crust largely independent of climate in addition to impact generated hydrothermal activity devitrification autometamorphism and the voluminous production of impact damaged materials that are susceptible to alteration must be considered when taken together a drastically different early climate on mars in which water is stable at the surface for extended periods of time cannot be ruled out however it is noted here that these additional impact mechanisms can operate and thereby extend the range of possible alteration settings to include climate conditions that may have been predominately colder and drier such a climate would not be dissimilar to the conditions of today with the important exceptions of a higher geothermal gradient and punctuated thermal disturbance to the cryosphere and hydrosphere from igneous activity and an exponentially higher impact flux

iron and aluminum hydroxysulfates from acid sulfate waters acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite chalcopyrite pyrrhotite and marcasite in rocks soils sediments and industrial wastes this spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits the formation of acid sulfate soils and the mobilization and release of acidity and metals to surface and ground waters the purely natural process of acid rock drainage is often intensified by human activities related to mining mineral processing construction soil drainage and dredging geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water and to microbes that catalyze the reaction process large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation hydrolysis and neutralization the objective of this chapter is to describe the formation properties fate and environmental implications of the nano to microphase hydroxy sulfates of fe and al that are precipitated from acid sulfate waters these minerals are commonly of poor crystallinity and difficult to characterize much remains to be learned about their occurrence formation and properties mine drainage the best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited ash et al 1951 barton 1978 nordstrom 1982a rose and cravotta 1998 nordstrom and alpers 1999 there may be as many as 500 000 inactive or abandoned mine sites in the united states alone lyon et al 1993 although most of these pose no immediate water quality problem kleinmann 1989 estimated that about 19 300 km of streams and more than 72 000 ha of lakes and reservoirs have been

carbon sequestration on mars on earth carbon sequestration in geologic units plays an important role in the carbon cycle scrubbing co 2 from the atmosphere for long term storage while carbonate is identified in low abundances within the dust and soils of mars at 1 wt in select meteorites and in limited outcrops no massive carbonate rock reservoir on mars has been identified to date here we investigate the largest exposed carbonate bearing rock unit the nili fossae plains combining spectral thermophysical and morphological analyses to evaluate the timing and carbon sequestration potential of rocks on mars we find that the olivine enriched 20 25 basalts have been altered by low temperature in situ carbonation processes to at most 20 fe mg carbonate thus limiting carbon sequestration in the nili fossae region to 0 25 12 mbar of co 2 during the late noachian early hesperian before or concurrent with valley network formation while this is large compared to modern day co 2 reservoirs the lack of additional comparably sized post late noachian carbonate bearing deposits on mars indicates ineffective carbon sequestration in rock units over the past 3 7 b y this implies a thin atmosphere 500 mbar during valley network formation extensive post noachian atmospheric loss to space or diffuse deep sequestration by a yet to be understood process in stark contrast to earth s biologically mediated crust atmosphere carbon reservoir ratio of 10 4 10 5 mars ratio is a mere 10 10 3 even if buried pre noachian crust holds multiple bars

orbital identification of carbonate bearing rocks on mars geochemical models for mars predict carbonate formation during aqueous alteration carbonate bearing rocks had not previously been detected on mars surface but mars reconnaissance orbiter mapping reveals a regional rock layer with near infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the nili fossae region the carbonate is closely associated with both phyllosilicate bearing and olivine rich rock units and probably formed during the noachian or early hesperian era from the alteration of olivine by either hydrothermal fluids or near surface water the presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering proposed to be characteristic of hesperian mars did not destroy these carbonates and thus did not dominate all aqueous environments

enigmatic tubular features in impact glass we describe the fi rst putative microbial trace fossils hosted in meteorite impact glass we conducted optical and scanning electron microscopy energy dispersive x ray spectroscopy and fourier transform infrared spectroscopy on postimpact tubular features hosted in impact glasses from the ries impact structure germany the morphologies of the tubules are inconsistent with known mineralogical crystallization mechanisms and combined with evidence of organic molecules suggest that these tubules cannot be formed through purely abiotic processes the simplest and most consistent explanation of the data is that biological activity played a role in the formation of the tubular textures in the ries glasses likely during postimpact hydrothermal activity as impact glass is a ubiquitous substrate on rocky bodies throughout the solar system and likely common on the early earth the preservation of biological activity in impact glass has signifi cant astrobiological implications for life on early earth as well as for the search for life on other planets

impact crater lakes on mars the robotic search for life on mars centers on identifying accessible environments where the biological catalyst water has existed the formation of large impact craters on mars 65 km diameter may have resulted in the creation of ice covered impact crater lakes which would not freeze for thousands of years even under present climatic conditions water could be supplied from deep confined aquifers penetrated by the impact craters without the need for surface melt water freezing of the lakes is postponed owing to heat from impact generated melt bearing deposits from impact related uplift of hotter rocks from depth and from the latent heat of freezing of a deep crater lake abundant morphologic evidence for ancient crater lakes has not been found in viking images except for craters associated with outflow channels however ice covered crater lakes could have formed and further searches for evidence of these lakes are warranted the lake deposits from dissected impact craters may represent one of the best targets for future surface exobiology investigations or sample return missions from mars

mineralogy porosity and fluid control on thermal conductivity of sedimentary rocks summary estimates of thermal conductivity of the main non clay and clay sedimentary minerals are presented especially for the case of argillaceous ones these estimates are averaged estimates based on the interpretation of laboratory conductivity porosity and mineralogy measurements performed on small volumes of the order of 100cm3 of water saturated moist and air saturated samples the sampling is representative of the main sedimentary rocks sandstones carbonates evaporites and shales and it is composed of samples considered as structurally isotropic material first we experimentally verify the first order control of mineralogy porosity and fluid content on bulk conductivity and we demonstrate that such influences may be predicted accurately using a geometric mean model as long as isotropic samples are used then we interpret the data using an inverse method in order to estimate the average mineral conductivities of the main non clay and clay minerals which give the best fit to the individual laboratory measurements through the geometric mean model the analysis is based on measurements on 82 non clay samples and 29 clay samples taken on oil well cores or cuttings on outcrops and on artificially recompacted samples estimates of average mineral conductivities returned by the inversion process for the main non clay minerals are similar to generally admitted values 7 7 w m k for quartz 3 3 w m i k for calcite 5 3 w m l k for dolomite and 6 3 w m k for anhydrite values obtained for the clay minerals are systematically lower than those obtained for non clay ones they are of the order of 1 9 w m k for illite and smectite 2 6 w m k for kaolinite and 3 3 w m l k for chlorite these estimates combined with porosity and mineralogy data are used with the geometric mean model in order to verify its first order validity for predicting thermal conductivity of small volumes of porous isotropic sedimentary rocks the bulk conductivity is predicted with an accuracy of the order of f10 per cent for moist or water saturated samples and of the order of f20 per cent for air saturated samples

effective thermal conductivity of heterogeneous rocks from laboratory experiments and numerical modeling 1 studying heat transfer processes in sedimentary crustal rocks requires the correct thermal conductivity of the respective rock type often a single value is used for a given rock type obtained from the measurements on homogenous samples we demonstrate how variations in rock layering and microfractures on the subcentimeter scale may influence thermal conductivity values at much larger scale we obtain thermal conductivity images from lab measurements on two different heterogeneous samples performed with an optical thermal conductivity scanner in two directions we study different spatial averaging methods for parameterizing the structural heterogeneities and the associated variation of thermal conductivity within the samples for each of these structural simplifications we set up a numerical model for a numerical heat transfer experiment in order to determine effective thermal conductivity values in two directions we compare these values and the mean thermal conductivities obtained from different mixing laws and find that in heterogeneous rocks effective and mean thermal conductivity may differ substantially this may cause significant errors in reservoir scale simulations of heat transfer with associated severe consequences for estimated heat flow and temperatures

high resolution heat flow density in the lower congo basin 1 heat flow density hfd has been derived in the lower congo basin from 293 conventional probe measurements 424 oil exploration data and about 1 000 000 bottom simulating reflector bsr values each set of data provides independent estimates of temperature gradients associated with specific uncertainties and geographic distributions but a statistical comparison in overlapping domains shows a relatively good consistency in situ conductivity has been measured in conventional surveys and estimated from rock composition and porosity in oil exploration boreholes in the deep offshore measurements and estimates are consistently low and increase significantly toward the shelf domain thermal conductivity does not change significantly in the interval between the water bottom and the bsr and can be estimated from the surface measurements to provide an inference of hfd the combined sets of hfd in the lower congo basin cover the overall domain of the continental margin and a part of the oceanic domain high resolution imaging of the bsr by three dimensional 3 d seismic studies provides in addition good quality nominal resolution of 500 m in the deep offshore at short length scales on the order of kilometers large variations of hfd from 30 to 140 mwm 2 exist above salt diapirs and canyons related to heat refraction on the other hand no small scale effect related to fluid flow has been detected although active venting is known at larger length scale hfd in the deep offshore is different on both sides of the congo submarine channel 54 8 mwm 2 to the north and 48 12 mwm 2 to the south which are also characterized by different basin tectonic styles at the margin scale hfd is significantly different in the oceanic domain 42 3 mwm 2 the deep continental offshore 52 10 mwm 2 and the continental shelf 65 15 mwm 2 a progressive reduction of the radiogenic heat contribution in the extended continental crust is the more likely the cause of these differences mantle heat flow below the continental margin is consequently high compared to that expected 15 mwm 2 for old shields such as congo

intense low latitude vlf emissions observed aboard ariel 4 analysis of the peak intensity of low latitude vlf emissions observed aboard the ariel satellite reveal that some north zone 3 2 khz vlf emissions are unexpectedly more intense than south zone vlf emissions in fact the north zone intensity peaks are 5 10 db higher than those in the south zone this discrepancy in intensity peaks can be explained in terms of wave growth during transverse resonant interaction between the wave and counterstreaming energetic electrons it is argued that vlf signals observed on board the ariel satellite were generated in the south zone during lightning discharges and propagated to equatorial heights in the whistler mode at the equator the emissions are amplified by taking energy from energetic electrons and then these amplified emissions again propagating in the whistler mode arrive at the ariel satellite in the north zone thus the intense signals in the south zone are preamplified and in the north zone these are observed after amplification this explains the discrepancy in the observations of intensity analysis of vlf satellite data reveals that vlf emissions have high spectral densities in the longitudinal range of 100 140 e these phenomena of vlf emissions are explained through the effect of the south pacific magnetic anomaly spma it is found that atmospheric scattering enhancing precipitated fluxes of energetic electrons in the south atlantic magnetic anomaly sama region has no role in vlf wave amplification

gas exsolution during fluid migration and its relation to overpressure and petroleum accumulation abstract petroleum systems in the tertiary sections of the gulf of mexico and niger delta among other basins are characterized by the close association between petroleum accumulation and over pressure although overpressure is generated mainly by compaction disequilibrium of the low permeability sediments exsolution of gases from water and petroleum during migration over great vertical distance may create overpressure or modify the existing overpressure in this paper the author combined relative permeability data and petroleum phase behavior modelling to explain and predict the presence of an overpressure and petroleum baffle due to gas exsolution generalized isoperm diagrams for oil gas and water phases in sandy and silty shaly sediments were created based on published data aqueous solubility of methane and carbon dioxide as a function of temperature pressure and salinity is summarized based on literature data phase diagrams of petroleum with a wide range of composition api gravity and gor were produced using phase behavior software with calibration using field data these tools were integrated to model overpressure and petroleum phase variations in two oil gas fields in the gulf of mexico the pressure gradients in these fields are likely modified by gas exsolution from the petroleum which migrated and accumulated within and below the pressure transition zone ptz petroleum trapped within ptz tends to be fractionated whereas that accumulated below ptz tends to be single phase with high api gravity these results provide a model which explains both the effect of gas exsolution on ptz and the occurrence of different types of petroleum in these fields these tools may be integrated with geological and seismic data to assess more accurately the economic value of petroleum accumulations in petroleum systems governed by overpressure and petroleum phase separation and fractionation

the reflectance spectra of opal a 0 5 25 μm from the taupo volcanic zone spectra that may identify hydrothermal systems on planetary surfaces 1 opal a the main component of siliceous sinters in many terrestrial hydrothermal systems is a hydrated silicate that commonly incorporates silicified microorganisms the detection of opal a on the surface of mars therefore may carry important implications in the search for extraterrestrial life sinters from the discharge apron of ohaaki pool north island new zealand yielded reflectance spectra wavelengths between 0 5 25 m that indicate the presence of absorbed water trapped water and silanol in opal a two classes 1 and 2 of reflectance spectra were detected between the wavelengths of 6 13 m the class 1 spectrum is similar to existing opal spectra and was collected from well consolidated samples that had low porosity the class 2 spectrum is unique when compared to the spectra of other silica polymorphs and was collected from poorly consolidated samples that had high porosity

sulfates in the north polar region of mars detected by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega imaging spectrometer observed the northern circumpolar regions of mars at a resolution of a few kilometers an extended region at 240 e 85 n with an area of 60 kilometers by 200 kilometers exhibits absorptions at wavelengths of 1 45 1 75 1 94 2 22 2 26 and 2 48 micrometers these signatures can be unambiguously attributed to calcium rich sulfates most likely gypsum this region corresponds to the dark longitudinal dunes of olympia planitia these observations reveal that water alteration played a major role in the formation of the constituting minerals of northern circumpolar terrains

sulfur isotope signatures for rapid colonization of an impact crater by thermophilic microbes in the 23 km diameter haughton impact structure canadian high arctic in sulfate rich bedrock widespread hydrothermal sulfide mineralization occurred in breccias formed during the impact the sulfides exhibit extreme sulfur isotopic fractionation relative to the original sulfate requiring microbial sulfate reduction by thermophiles throughout the crater this evidence of widespread microbial activity demonstrates that colonization could occur within the lifetime of a moderately sized impact induced hydrothermal system the pyrite was subsequently oxidized to jarosite which may also have been microbially mediated the successful detection of evidence for microbial life suggests that it would be a valuable technique to deploy in sulfate rich impact terrain on mars

impact generated hydrothermal systems capable of forming phyllosilicates on noachian mars the early history of the terrestrial planets was punctuated by a period of heavy bombardment frequent large impacts condensed in a short 0 02 0 5 ga long time period resulted in heavily cratered planetary surfaces in volatile bearing planetary crusts each of these large impacts created a volume of hot rock and melt that drove vast subsurface hydrothermal systems in mars basaltic crust these systems produced a variety of alteration phases the nature of which we explored with thermochemical modeling using the computer code chiller we found a variety of oxides hydroxides and hydrous and water free silicates resulting from the hydrothermal alteration the main hydrous silicates are serpentine chlorite nontronite and other clay minerals some of the resulting assemblages contain up to 15 wt bound water our results constrain the temperature and water rock ratio at the time of alteration and compare well to the mineral assemblages found on mars by omega observatoire pour la mineralogie l eau les glaces et l activite and crism compact reconnaissance imaging spectrometer for mars and therefore provide an interpretative framework for analyzing martian mineralogy from orbital data our results also provide a geological template needed to select landing locations for future missions that search for water and energy sources associated with potential habitats on early mars

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time

in situ evidence for an ancient aqueous environment at meridiani planum mars sedimentary rocks at eagle crater in meridiani planum are composed of fine grained siliciclastic materials derived from weathering of basaltic rocks sulfate minerals including magnesium sulfate and jarosite that constitute several tens of percent of the rock by weight and hematite cross stratification observed in rock outcrops indicates eolian and aqueous transport diagenetic features include hematite rich concretions and crystal mold vugs we interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history the environmental conditions that they record include episodic inundation by shallow surface water evaporation and desiccation the geologic record at meridiani planum suggests that conditions were suitable for biological activity for a period of time in martian history

visible near infrared spectra and two layer modeling of palagonite coated basalts fine grained dust coatings on martian rocks and soils obscure underlying surfaces and hinder mineralogic interpretations of both remote sensing and in situ observations we investigate laboratory visible near infrared spectra of various thicknesses of palagonite coatings on basalt substrates we develop a two layer hapke scattering model incorporating porosity grain size and derived absorption coefficients of palagonite and basalt that reproduces the observed spectra only when the single scattering particle phase function is varied with wavelength