are the viking lander sites representative of the surface of mars abstract global remote sensing observations of mars are compared with remote sensing observations of the two viking lander site regions and with orbiter and lander imaging of the sites the lander sites do not fit most of the global trends of remote sensing data the presence of a duricrust in the top meter of the surface is inferred for most regions of high thermal inertia although the duricrust is thinner at the lander sites than elsewhere regions of low thermal inertia are covered by greater than several centimeters of unconsolidated dust a thin microns thick layer of bright dust appears at the surface at the lander sites and these locations may be regions of incipient formation of low thermal inertia the lander sites are intermediate in structure between classical bright and dark regions and are distinctive from most of the rest of the planet

porosity and permeability in volcanic rocks a case study on the serie tobifera south patagonia argentina the middle to late jurassic serie tobifera belongs to the chon aike province and extends all over patagonia and the antarctic peninsula it consists largely of ignimbrites epiclastics and rhyolitic lavas and was considered only a minor reservoir rock for oil with fracture permeability petrographic and petrophysical data in selected core samples from the austral basin were collected to determine the processes controlling the porosity and permeability of these volcanic rocks the sequence of processes occurring during cooling and in the post cooling stages can modify sometimes substantially their original petrophysic characteristics the results show that the highest porosity and permeability occur in rocks with quench fractured glasses and in non welded ignimbrites with gas pipe structures followed by autobrecciated rhyolites welded ignimbrites massive glasses and fresh rhyolites have the lowest permeabilities the new data indicate that tectonic fracturing is not as significant as was considered before and application of these concepts are relevant in the assesment of volcanic reservoir quality

the emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and ph front here we argue that life emerged on earth from a redox and ph front at c 4 2 ga this front occurred where hot c 150 c extremely reduced alkaline bisulphide bearing submarine seepage waters interfaced with the acid warm c 90 c iron bearing hadean ocean the low ph of the ocean was imparted by the ten bars of co 2 considered to dominate the hadean atmosphere hydrosphere disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal fes membrane iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites our hypothesis is that the fes membrane laced with nickel acted as a semipermeable catalytic boundary between the two fluids encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers the ocean provided carbonate phosphate iron nickel and protons the hydrothermal solution was the source of ammonia acetate hs h 2 and tungsten as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde the mean redox potential eh across the membrane with the energy to drive synthesis would have approximated to 300 millivolts the generation of organic anions would have led to an increase in osmotic pressure within the fes bubbles thus osmotic pressure could take over from hydraulic pressure as the driving force for distension budding and reproduction of the bubbles condensation of the organic molecules to polymers particularly organic sulphides was driven by pyrophosphate hydrolysis regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the hadean ocean this was the first use by a metabolizing system of protonmotive force driven by natural aph which also would have amounted to c 300 millivolts protonmotive force is the universal energy transduction mechanism of life taken together with the redox potential across the membrane the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt the role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers this organic take over of the membrane material led to the miniaturization of the metabolizing system information systems to govern replication could have developed penecontemporaneously in this same milieu but iron sulphur and phosphate inorganic components of earliest life continued to be involved in metabolism

clay mineral evolution changes in the mechanisms of formation and global distribution of phyllosilicate clay minerals through 4 567 ga of planetary evolution in our solar system reflect evolving tectonic geochemical and biological processes clay minerals were absent prior to planetesimal formation 4 6 billion years ago but today are abundant in all near surface earth environments new clay mineral species and modes of clay mineral paragenesis occurred as a consequence of major events in earth s evolution notably the formation of a mafic crust and oceans the emergence of granite rooted continents the initiation of plate tectonics and subduction the great oxidation event and the rise of the terrestrial biosphere the changing character of clay minerals through time is thus an important part of earth s mineralogical history and exemplifies the principles of mineral evolution

earth and mars water inventories as clues to accretional histories abstract the earth has 2 7 km of water on its surface its mantle contains at least 150 ppm water and probably significantly more depending on the amount of undepleted mantle and subducted crustal water that is present geologic evidence suggests that a few hundred meters of water are close to the martian surface but evidence from snc meteorites indicates that the martian mantle is very dry containing no more than about 35 ppm water part of the difference in water content of the mantles of the two planets is attributed to plate tectonics however the earth s mantle appears to contain at least several times the water content of the martian mantle even accounting for plate tectonics we attribute the difference to two possible causes the first possibility is that melting of the earth s surface during accretion as a result of the development of a steam atmosphere allowed impact devolatized water at the surface to dissolve into the earth s interior in contrast because of mars smaller size and greater distance from the sun the martian surface may not have melted so that the devolatilized water could not dissolve into the surface a second and preferred possibility is that mars like the earth acquired a late volatile rich veneer but it did not get folded into the interior as with the earth but instead remained as a water rich veneer the perception of mars as having a wet surface but a dry interior is consistent with what we know of the geologic history of mars which can be viewed as the progressive intrusion and overplating of a water rich crust by dry mantle derived volcanic rocks

geochemical constraints on chemolithoautotrophic metabolism by microorganisms in seafloor hydrothermal systems mixing of hydrothermal fluids and seawater at the ocean floor combined with slow reaction kinetics for oxidation reduction reactions provides a source of metabolic energy for chemolithotrophic microorganisms which are the primary biomass producers for an extensive submarine ecosystem that is essentially independent of photosynthesis thermodynamic models are used to explore geochemical constraints on the amount of metabolic energy potentially available from chemosynthetic reactions involving s c fe and mn compounds during mixing of hydrothermal fluids with seawater for the vent fluid used in the calculations epr 21 n obs the model indicates that mixing environments are favorable for oxidation of h2s ch4 fe2 and mn2 only below 38 c with methanogenesis and reduction of sulfate or s favored at higher temperatures suggesting that environments dominated by mixing provide habitats for mesophilic but not thermophilic aerobes and thermophilic but not mesophilic anaerobes a maximum of 760 cal per kilogram vent fluid is available from sulfide oxidation while between 8 and 35 cal kg vent fluid is available from methanotrophy methanogenesis oxidation of fe or mn or sulfate reduction the total potential for chemosynthetic primary production at deep sea hydrothermal vents globally is estimated to be about 1013 g biomass per year which represents 0 02 of the global primary production by photosynthesis in the oceans thermophilic methanogens and sulfate and s reducers are likely to be the predominant organisms in the walls of vent chimneys and in the diffuse mixing zones beneath warm vents where biological processes may contribute to the high methane concentrations of vent fluids and heavy 34s32s s ratios of vent sulfide minerals the metabolic processes taking place in these systems may be analogs of the first living systems to evolve on the earth

high temperature life without photosynthesis as a model for mars discoveries in biology and developments in geochemistry over the past two decades have lead to a radical revision of concepts relating to the upper temperature at which life thrives the genetic relationships among all life on earth links between organic and inorganic compounds in geologic processes and the geochemical supply of metabolic energy it is now apparent that given a source of geochemical energy in the form of a mixture of compounds that is far from thermodynamic equilibrium microorganisms can take advantage of the energy and thrive without the need for photosynthesis as a means of primary productivity this means that life can exist in the subsurface of a planet such as mars without necessarily exhibiting a surface expression theoretical calculations quantify the geochemically provided metabolic energy available to hyperthermophilic organisms in submarine hydrothermal systems on the earth and help to explain the enormous biological productivity of these systems efforts to place these models in the context of the early earth reveal that substantial geochemical energy would have been available and that organic synthesis would have been thermodynamically favored as hydrothermal fluids mix with seawater

magmatism and petroleum exploration in the brazilian paleozoic basins abstract petroleum exploration in the paleozoic sedimentary basins of brazil has proven very challenging for explorationists except for the solimoes basin in which transcurrent tectonism formed prospective structural highs brazilian paleozoic basins lack intense structural deformation and hence the detection and prospecting of place is often difficult magmatic intrusive and associated rocks in all these basins have traditionally been considered heat sources and hydrocarbon traps the role of tholeiitic basic dikes in the generation migration and accumulation of petroleum in the anhembi oil occurrence sao paulo state is discussed herein it follows that similar geological settings in other paleozoic basins can be regarded as promising sites for oil accumulation that warrant investigation via modern geological and geophysical methods

volcanic rocks as prolific gas reservoir a case study from the qingshen gas field in the songliao basin ne china abstract the qingshen gas field with over 100 billion cubic meters bcms of proven gas reserves was discovered recently in the upper jurassic lower cretaceous strata of the songliao basin northeastern china the stratigraphic relationships and gas chemical compositions indicate mixed gas sources dominantly from the upper jurassic lower cretaceous coals and associated dark mudstones underlying the gas reservoirs with minor contribution from deep inorganic sources the gas reservoirs consist mainly of volcanic rocks rhyolite and tuff with some production also from the conglomerate gas charge into these largely volcanic rock reservoirs appears to coincide with the peak gas generation in the deep upper jurassic lower cretaceous coal measures the presence of several thick lacustrine mudstone beds in the upper cretaceous strata as regional caprocks and relatively mild structural deformation since the late cretaceous are among the favorable conditions for the preservation of large volume of natural gases in these relatively deep gas reservoirs the gas yields are the highest in the paleomorphological highs where fractures and secondary porosity are well developed in the gas reservoirs

the nature of martian fluids based on mobile element studies in salt assemblages from martian meteorites the s cl and br abundances determined in salt assemblages in nakhla and lafayette olivine fracture fillings and in gas rich impact melt grim glasses from shergotty and eet79001 lithologies a b using empa eds aps x ray microprobe techniques are compared with the s and cl abundances determined by gooding and coworkers in similar samples using quadrupole mass spectrometric techniques all the analytical methods yield relatively high cl and low so sub 3 abundances in nakhla indicating a so sub 3 cl ratio of approx 0 2 the same ratio in lafayette secondary salts seems to be approx 2 in the case of grim glasses from shergotty and eet79001 lith a lith b the so sub 3 abundance is found to be high whereas the cl abundance is low yielding a so sub 3 cl ratio of approx 5 300 large errors are associated with these ratios because of low cl signals the salts found in nakhla fracturefillings are inferred to have formed from cl rich fluids high ph near nakhlite source region on mars whereas the secondary minerals found in shergottite grim glasses seem to be associated with so sub 3 rich fluids low ph near shergottite source region on mars the cl rich fluids seem to have infiltrated into the nakhlite source region approx 600 ma ago more whereas the so sub 3 rich fluids likely percolated into the shergottite source region at approx 180 ma or less suggesting the possible existence of two types of fluid sources on mars less

remote laser induced breakdown spectroscopy analysis of east african rift sedimentary samples under mars conditions abstract laser induced breakdown spectroscopy will be used by the chemcam instrument on the curiosity rover to obtain chemical analyses of the martian surface surficial and deeper hydrothermal processes on mars have produced a diverse family of chemical and clastic sedimentary lithologies from primary igneous rocks through physical and chemical transport deposition and diagenesis this study uses 16 samples from the east african rift ear as martian analogues to assess use of libs to evaluate weathering reactions in sedimentary rocks data were acquired at 9 m distance with samples under conditions designed to simulate mars use of external validation in which a few sedimentary samples are added to the validation set coupled with choice of the first local minimum in the root mean square value in all the components of the validation model provides optimal results in this data set accuracy is measured using root mean square error predictions for major elements in the sedimentary rocks as expressed in wt oxides even lower errors can be obtained by using a more focused training set these results are sufficiently accurate to usefully characterize the four competing kinds of chemical weathering reactions in paleosols hydrolysis oxidation hydration and salinization

the nakhlite hydrothermal brine on mars abstract water is the basis of habitability and formation conditions of hydrous alteration minerals are key to temperature and chemical conditions of that water using new detailed observations on nakhlite martian meteorite alteration composition temperature and redox conditions of the water that formed the observed hydrous alteration can be determined through thermochemical modelling we show that the nakhlite parent rocks on mars encountered a co2 rich hydrothermal fluid at 150 t 200 c ph 6 8 with a water rock ratio w r 300 under these conditions fe rich carbonate was precipitated within brittle fractures as the fluid cooled to 50 c at ph 9 and w r of 6 fe rich phyllosilicate precipitated followed in turn by rapid precipitation of an amorphous gel it was enriched in the most soluble species e g k na of alkaline ph and similar to terrestrial i e not seawater influenced dilute brines in basaltic terrains on earth our results show that environments associated with this type of fluid were habitable unlike those associated with acid sulphate fluids considering the timing of the nakhlite alteration the most likely cause is impact generated hydrothermal alteration of the nakhlite pile at the margins of an impact crater the martian subsurface fluid forming phyllosilicates provided habitable temperatures and many of the nutrients required for life

the imprint of time on canadian soil landscapes abstract the imprint of time on canadian soil landscapes reflects the strong influence of repeated quaternary glaciations with most soils having formed on late pleistocene glacial sediments and to a lesser extent holocene non glacial sediments soil chronosequences in these youthful landscapes seldom span the full holocene and have been documented principally in areas of coastal isostatic uplift and shoreline evolution as well as on recessional moraine sequences in the cordillera these chronosequences have placed quantitative constraints on rates of podzolization in environments ranging from coastal temperate rainforest to subarctic longer sequences involving soils and relict paleosols on pleistocene morainal and glaciofluvial surfaces in the central yukon territory record more complex legacies of pedogenesis and landscape evolution but with much coarser time control and many potentially confounding influences of climatic change and disturbance processes older weathered bedrock and regolith can make significant contributions to soil parent materials in several settings 1 in favoured locations where local conditions protected these materials from glacial erosion in southern canada 2 beyond the maximum limits of glaciation principally in northwestern canada and 3 in the arctic where cold based non erosive ice allowed preservation of these materials closer collaborations between pedologists and other quaternary scientists will be needed to ensure a more complete understanding of these complex pedogenic legacies in canadian landscapes

sedimentary silica on mars terrestrial planetary surfaces other than earth are overwhelmingly basaltic in character because of this among the most intriguing and significant results from recent studies of mars are the occurrences of high silica rocks at the pathfinder site and orbital thermal emission spectroscopy evidence for a global petrological dichotomy with andesites dominating the entire northern hemispheric plains however during the alteration of basalt under a wide variety of pressure temperature and fluid conditions silica is highly mobile and chemical and or mineralogical relationships among martian soils and other surface deposits suggest the likelihood that sedimentary silica phases would have formed during surficial alteration processes accordingly the redistribution of sedimentary silica needs to be considered in interpreting at least some of the high silica features seen on mars

an integrated chemical and stable isotope model of the origin of midocean ridge hot spring systems chemical and isotopic changes accompanying seawater basalt interaction in axial midocean ridge hydrothermal systems are modeled with the aid of chemical equilibria and mass transfer computer programs incorporating provision for addition and subtraction of a wide range of reactant and product minerals as well as cation and oxygen and hydrogen isotopic exchange equilibria the models involve stepwise introduction of fresh basalt into progressively modified seawater at discrete temperature intervals from 100 to 350 c with an overall water rock ratio of about 0 5 being constrained by an assumed 18 o h 2o at 350 c of 2 0 per mil h craig personal communication 1984 this is a realistic model because 1 the grade of hydrothermal metamorphism increases sharply downward in the oceanic crust 2 the water rock ratio is high 50 at low temperatures and low 0 5 at high temperatures and 3 it allows for back reaction of earlier formed minerals during the course of reaction progress the results closely match the major element chemistry von damm et al 1985 and isotopic compositions craig et al 1980 of the hydrothermal solutions presently emanating from vents at 21 n on the east pacific rise the calculated solution chemistry for example correctly predicts complete loss of mg and so 4 and substantial increases in si and fe however discrepancies exist in the predicted ph 5 5 versus 3 5 measured and state of saturation of the solution with respect to greenschist facies minerals the calculated d h 2o is 2 6 per mil in excellent agreement with analytical determinations the calculated chemical mineralogic and isotopic changes in the rocks are also in good accord with observations on altered basalts dredged from midocean ridges humphris and thompson 1978 stakes and o neil 1982 as well as with data from ophiolites gregory and taylor 1981 predicted alteration products include anhydrite and clay minerals at low temperatures and a typical albite epidote chlorite tremolite greenschist assemblage at 350 c the models demand that the major portion of the water rock interaction occur at temperatures of 300 350 c interaction at temperatures below approximately 250 c results in negative 18 o h 2o shifts contrary to the observed positive 18 o values of the fluids exiting at midocean ridge vents hydrogen isotope fractionation curves by suzuoki and epstein 1976 lambert and epstein 1980 and liu and epstein 1984 among others are compatible with the model and require d h 2o to increase at all temperatures as a result of seawater basalt interaction

mesozoic cenozoic tectonic evolution and dynamics of the songliao basin ne asia implications for the closure of the paleo asian ocean and mongol okhotsk ocean and subduction of the paleo pacific ocean abstract the songliao basin in northeast china in the eastern part of the central asia orogenic belt is the largest accretionary orogen belt in the world however to date previous studies have not extensively examined the dynamic mechanism of its formation and evolution especially the pre cretaceous in this study the mesozoic cenozoic tectonic style stratigraphic records sedimentary time magmatic activity and tectonic evolution in the songliao basin were systematically analysed and summarised we propose that songliao basin experienced multi stage basin superposition processes the foreland compression stage syn rift and post rift stage and structural inversion stage after palaeozoic deposition the basin experienced a strong orogeny with the formation of the triassic middle jurassic foreland basin during the syn rift period three tectonic movements occurred at the end of the shahezi formation late valangnian 135 ma the end of first member of the yingcheng formation late hauterivian 129 ma and the end of the yingcheng formation late barrenian 125 ma in the songliao basin which ended the evolutional history of the rift in the post rift period three tectonic events occurred at the end of the nenjiang formation middle campanian 79 ma the mingshui formation late maastrichtian 66 ma and the yi an formation late chattian 23 ma which determined the deformation characteristics of the middle and shallow strata of the basin such as folding and reverse faults the rudimentary shape formed at the end of the nenjiang formation was finalised at the end of the mingshui formation and formed at the end of the yi an formation the largest depth and width influence of the two events was at the end of the mingshui and yi an formations which played a decisive role in the generation migration and accumulation of oil and gas in the middle and shallow strata of songliao basin after a series of asthenospheric mantle upwelling crustal uplift and extension and volcanic activity songliao basin was eventually formed the formation and structural evolution of the songliao basin were mainly influenced by the paleo asian ocean the mongol okhotsk ocean and the pacific ocean the closure of the paleo asian ocean in the late permian early triassic was influenced by the siberian plate which began to contact and collide with the xingan mongolian block from west to east causing the mongol okhotsk ocean to close in a scissor like structure from west to east in the early middle jurassic the subduction and movement of pacific rim tectonic systems such as the farallon izanagi pacific and philippine plates led to the formation of songliao basin which has experienced a foreland period via compressive pressure since the triassic syn rift period and post rift period via extensional stress and then a structural inversion period

volcanism on mars more than 15 years of planetary exploration of mars have given insight into the geologic processes that have shaped its surface the newly acquired viking data have shown that volcanism is one of the most important geologic processes operating on mars throughout its history in situ chemical analyses of martian soil by the viking lander spacecraft indicate mafic to ultramafic source rocks this is consistent both with available remote sensing data which indicate the presence of mafic minerals such as pyroxene and olivine and with petrologic modeling based on available geophysical data which suggest that martian lavas are probably iron rich and ultramafic these data strongly suggest that basaltic volcanism is widespread on mars and much of the photogeological data may be studied in this context photogeological analysis of the martian surface has shown two main types of volcanic morphologies the first type is central volcanoes which are volcanic landforms developed by continued and prolonged eruption from a point source vent this category includes 1 shields the classic low profile volcanic mountains of which olympus mons is the most spectacular example 2 domes steep sided constructs such as tharsis tholus that may represent lower rates of eruption than the shields or possibly more silicic lava compositions 3 highland patera radially textured low profile volcanoes that occur in the cratered terrain and are interpreted as ash shields 4 alba patera an apparently unique volcanic landform consisting of a vast volcanic center over 1500 km across with flank slopes of less than a tenth of a degree and 5 various small features such as cinder cones the second major category is volcanic plains which are units recognized by several criteria of which the presence of mare ridges and flow lobes are the most useful volcanic plains are subdivided into four main groups 1 simple flows broad smooth to rolling plains that contain numerous mare type ridges but no flow lobes interpreted as being composed of thick single cooling units 2 complex flows displaying multiple overlapping flow lobes interpreted to be indicative of thin multiple cooling units 3 undifierentiated flows plains that typically lack any morphologic identifying feature but are considered to be volcanic partly on the basis of their association with large volcanic centers and 4 questionable plains volcanic units heavily modified by other processes erosion tectonism etc so that their origins are uncertain when these categories of volcanic morphologies are combined with relative age data provided by crater statistics a volcanic history for mars can be derived as follows early heavy bombardment of mars was accompanied and followed by small scale fluvial channeling extensive flood volcanism the plateau plains and ash shield volcanism in the cratered terrain shortly after this time less extensive flood volcanism continued to resurface the planet during formation of the northern southern hemisphere dichotomy central volcanism became more prominent with the development of the alba patera center as well as the older shields and domes of the northern hemisphere early tharsis and elysium regions the development of the tharsis and elysium uplifts may have triggered the release of large scale catastrophic floods producing large channels continued uplift and lithospheric thinning concentrated volcanic activity in the tharsis region producing large shield volcanoes and extensive lava plains both central vent and plains volcanism have been active throughout martian history but the volumes of extrusion have gradually decreased with time this is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time gradually turning off the volcanism although many questions remain regarding martian volcanism the viking data have provided a remarkable detailed overview of the probable nature of the volcanic history of mars

constraining methane release due to serpentinization by the observed d h ratio on mars it has been suggested that mars atmospheric ch4 could be produced by crustal hydrothermal systems the two most plausible mechanisms proposed so far not exclusive from each other are homogeneous formation by fluid rock interaction during magmatic events and serpentinization of ultramafic rocks the first goal of the present paper is to provide an upper limit on the release rate of serpentinization derived ch4 due to the release of numerous h2 molecules together with one ch4 molecule followed by thermal escape of all released h atoms to space and subsequent h isotopic fractionation even a relatively modest serpentinization derived ch4 release acting over geological time scales may result in a significant enrichment of d wrt h in mars cryo hydrosphere including atmosphere polar caps and subsurface reservoirs by assuming that the ch4 release rate has been proportional to the volcanic extrusion rate during the last 4 billion years we calculate the present d h ratio resulting from the crustal oxidation due to serpentinization including the additional effect of sulfur oxidation we show that this rate doesn t exceed 20 within a factor of 2 of the estimated present value of the ch4 release rate if not the present d h ratio on mars would be larger than observed 5 smow this result suggests that either the production of ch4 is sporadic with a present release rate larger than the average rate or there are other significant sources of ch4 like homogeneous formation from mantle carbon degassing or bacterial activity second assuming further that most of the h isotopic fractionation observed today is due to serpentinization we show that a 400 m thick global equivalent layer of water may have been stored in serpentine since the late noachian this result doesn t depend on the chemical form of the released hydrogen h2 or ch4 such a quantity is generally considered as the amount required for explaining the formation of valley networks on mars serpentinization therefore appears as a potentially efficient sink of water on mars much more efficient than o escape for having removed large amounts of water from the hydrosphere

co2 solubility in primitive martian basalts similar to yamato 980459 the effect of composition on co2 solubility of basalts and the evolution of the martian atmosphere to determine the influence of basalt composition on the co2 solubility in martian lavas we investigated experimentally a synthetic melt based on the martian meteorite yamato 980459 y 980459 an olivine phyric shergottite and a picritic rock 19 wt mgo thought to be a near primary liquid derived from high temperature 1540 c partial melting of the martian mantle experiments were performed in a piston cylinder apparatus at 1 2 gpa and 1600 1650 c co2 contents in quenched glasses were determined using fourier transform infrared spectroscopy ftir and range from 0 45 1 26 wt despite large differences in feo and mgo contents the co2 solubilities in y 980459 are similar to that in a less primitive synthetic martian basalt based on the humphrey rock and to a hawaiian tholeiite the lack of enhanced solubility in fe2 and mg2 rich melts is likely owing to the complex structural role of these cations in silicate melts acting partly as network formers rather than network modifiers the small sensitivity of co2 solubility to compositional variations among martian and tholeiitic basalts means that the experimentally determined solubilities may be applicable to a wide spectrum of martian magmatic products using experimentally determined co2 solubilities of y 980459 and humphrey allows the calibration of the thermodynamic parameters governing dissolution of co2 vapor as carbonate in martian basalts this relation facilitates calculation of the co2 dissolved in magmas derived from graphite saturated martian basalt source regions as a function of p t and f o2 the hot conditions in the source of y 980459 1540 10 c and 1 2 0 5 gpa are plausible for plume related magmas forming the giant tharsis volcanic complex which accounts for 50 of martian igneous activity since stabilization of the primordial crust if oxygen fugacity in the sources of hot tharsis magmatism were equivalent to that at the iron wustite buffer iw or 1 log unit above iw 1 respectively then the entire tharsis event would outgas 30 300 mbars of co2 to the martian atmosphere which is far from the 2 bars required to stabilize an equable climate in the late noachian and early hesperian epochs this mismatch could be reconciled if significant martian igneous activity derived from comparatively oxidized mantle sources i e iw 2 similar to those responsible for the nakhlite meteorites

deep alteration between hellas and isidis basins abstract recent investigations of alteration of martian crustal outcrops suggest putative crustal hydrothermal systems which are favorable environments for the emergence of life in this study we perform an analysis of the crism targeted observations covering crustal outcrops in the region between the hellas and isidis basins with the goal of investigating the alteration phases over the wide studied region we detect the presence of possible serpentines chlorites smectites and carbonates these detections occur within ejecta blankets crater walls and central uplifts of impact craters we investigate the relation between the observed associations of minerals and the ages of the impact craters assessed by crater count no clear relation is observed we also investigate the relationship between the group of detected mineral and the pre impact depth of the studied outcrops assessed from the size of the impact craters this method allows us to reconstruct the pre impact cross section we suggest that alteration of the first 7 km of the crust between the hellas and isidis basins may have undergone alteration processes

reproducing hydrogeochemical conditions triggering the formation of carbonate and phyllosilicate alteration mineral assemblages on mars nili fossae region 1 the cooccurrence of mg fe ca carbonate and stratigraphically lower phyllosilicate bearing rock units identified in the nili fossae region on mars may reveal a co2 driven aqueous alteration process on ancient mars we reproduce hydrogeochemical conditions for concurrent carbonate and phyllosilicate formation in rock columns by using hydrogeochemical one dimensional transport modeling which is based on chemical equilibrium thermodynamics our models assume the isochemical low temperature equilibration of ultramafic rocks with pure water at varying atmospheric co2 partial pressure water to rock ratio temperature and rock composition equilibration among 1 mineral assemblages of olivine rich rocks 18 28 wt mgo 2 pure water water to rock ratio 500 50 mol mol 1 3 co2 transferred from the atmosphere co2 partial pressure lower than 2 bars and higher than 0 01 bar at 278 k and 4 100 000 years of diffusive mass transport create hydrogeochemical conditions enabling the concurrent formation of mg rich mg fe ca solid solution carbonate and stratigraphically lower phyllosilicate rich alteration assemblages in rock columns the modeled composition of alteration mineral assemblages their depth distribution and carbonate composition are similar to the observations from the nili fossae region higher equilibration temperature 373 k results in the formation of ca dominated ca mg carbonate instead of mg rich mg fe ca carbonate and in an inverse stratification with phyllosilicate rich units overlying carbonate rich units modeling results suggest that rocks in the nili fossae region hosting the carbonate and phyllosilicate mineral assemblage have been exposed to a groundwater alteration process driven by atmospheric co2 partial pressures ranging between 2 bars and 0 01 bar at low temperature 278 k

processes controlling porosity and permeability in volcanic reservoirs from the austral and neuquen basins argentina volcanic rocks develop primary and secondary porosity and permeability depending on both their lithology and the sequence of processes involved in their formation primary processes welding deuteric crystal dissolution gas release flow fragmentation and crystal shattering may lead to high porosity and permeability the best example of which is a nonwelded ignimbrite with well developed gas pipe zones secondary processes different types of alteration however tend to decrease primary porosity however certain secondary processes such as dissolution and hydraulic fracturing may contribute to enhance total porosity and permeability these conclusions were developed through a systematic review of reservoir quality in volcanic rocks integrating lithology and process interpretation with petrophysical data the said information was taken from selected cores of volcanic rocks from the serie tobfera unit in the austral basin and the precuyano unit in the neuqun basin argentina a clear understanding of both primary and secondary processes may serve to predict the quality of volcanic reservoirs and could be used as a guide for oil and gas exploration and development in many parts of the world

composition porosity and reservoir potential of the middle jurassic kashafrud formation northeast iran abstract in the kopet dagh basin of iran deep sea sandstones and shales of the middle jurassic kashafrud formation are disconformably overlain by hydrocarbon bearing carbonates of upper jurassic and cretaceous age to explore the reservoir potential of the sandstones we studied their burial history using more than 500 thin sections supplemented by heavy mineral analysis microprobe analysis porosity and permeability determination and vitrinite reflectance the sandstones are arkosic and lithic arenites rich in sedimentary and volcanic rock fragments quartz overgrowths and pore filling carbonate cements calcite dolomite siderite and ankerite occluded most of the porosity during early to deep burial assisted by early compaction that improved packing and fractured quartz grains iron oxides are prominent as alteration products of framework grains probably reflecting source area weathering prior to deposition and locally as pore fills minor cements include pore filling clays pyrite authigenic albite and k feldspar and barite existing porosity is secondary resulting largely from dissolution of feldspars micas and rock fragments with some fracture porosity porosity and permeability of six samples averages 3 2 and 0 0023 md respectively and 150 thin section point counts averaged 2 7 porosity reflectance of vitrinite in eight sandstone samples yielded values of 0 64 0 83 in the early mature to mature stage of hydrocarbon generation within the oil window kashafrud formation petrographic trends were compared with trends from first cycle basins elsewhere in the world inferred burial conditions accord with the maturation data suggesting only a moderate thermal regime during burial some fractures iron oxide cements and dissolution may reflect cenozoic tectonism and uplift that created the kopet dagh mountains the low porosity and permeability levels of kashafrud formation sandstones suggest only a modest reservoir potential for such tight sandstones fractures may enhance the reservoir potential

europa s crust and ocean origin composition and the prospects for life abstract we have considered a wide array of scenarios for europa s chemical evolution in an attempt to explain the presence of ice and hydrated materials on its surface and to understand the physical and chemical nature of any ocean that may lie below we postulate that following formation of the jovian system the europan evolutionary sequence has as its major links a initial carbonaceous chondrite rock b global primordial aqueous differentiation and formation of an impure primordial hydrous crust c brine evolution and intracrustal differentiation d degassing of europa s mantle and gas venting e hydrothermal processes and f chemical surface alteration our models were developed in the context of constraints provided by galileo imaging near infrared reflectance spectroscopy and gravity and magnetometer data low temperature aqueous differentiation from a carbonaceous ci or cm chondrite precursor without further chemical processing would result in a crust ocean enriched in magnesium sulfate and sodium sulfate consistent with galileo spectroscopy within the bounds of this simple model a wide range of possible layered structures may result the final state depends on the details of intracrustal differentiation devolatilization of the rocky mantle and hydrothermal brine reactions could have produced very different ocean crust compositions e g an ocean crust of sodium carbonate or sulfuric acid or a crust containing abundant clathrate hydrates realistic chemical physical evolution scenarios differ greatly in detailed predictions but they generally call for a highly impure and chemically layered crust some of these models could lead also to lateral chemical heterogeneities by diapiric upwellings and or cryovolcanism we describe some plausible geological consequences of the physical chemical structures predicted from these scenarios these predicted consequences and observed aspects of europa s geology may serve as a basis for further analys is and discrimination among several alternative scenarios most chemical pathways could support viable ecosystems based on analogy with the metabolic and physiological versatility of terrestrial microorganisms

variability of petroleum inclusions in vein fossil and vug cements a geochemical study in the barrandian basin lower palaeozoic czech republic abstract although no commercial oil or gas occurrences have been found in the barrandian basin residual oils and petroleum inclusions give evidence about the petroleum history of this lower palaeozoic basin petroleum inclusions are hosted in six generations of calcite and quartz cements that can be attributed to different stages of a basinal cycle and associated diagenetic events they were analysed using an on line crushing and an off line crush and leach approach five different groups pi a to pi e and intermediate mixtures pi m could be differentiated based on the relative distribution of n alkanes all oils had a calculated aromatic maturity rc ranging between 0 9 and 1 6 pi a shows a molecular weight maximum in the range of n c8 11 with a constant attenuation towards higher carbon numbered n alkanes this distribution is interpreted as the pristine precursor oil for other petroleum inclusion groups pi b has a maximum weight abundance at n c15 20 the genetic relationship between pi b and pi a can tentatively be explained by mixing effects or by gas stripping pi c is bimodal and characterised by a molecular weight maximum at n c32 34 and also a molecular weight maximum at n c15 20 similar to that of group pi b pi d shows a normally distributed molecular weight maximum in the range n c25 28 and is interpreted as a wax precipitate from ascending gas saturated in n alkanes pi e contains predominantly gaseous compounds with only a few higher hydrocarbons thompson s aromaticity values are elevated for condensates of group pi e and also for group pi c that is dominated by long chained n alkanes this gives evidence that fault bound petroleum migration in the barrandian basin was associated with evaporative fractionation for group pi c and pi e samples of group pi e yielded gas range compounds only and all come from a last generation of vein filling whitish calcite that was formed in a late uplift phase of the basin for other petroleum inclusion groups only a vague preferential occurrence in specific mineralisation phases or stratigraphic intervals of the host rock has been found this reflects the predominance of fracture bound migration in the barrandian basin aromatic maturity values also showed no correlation between either crystal type or pi group in six of the investigated petroleum inclusion samples alk 1 enes are present these terminal olefins are interpreted to be the result of the natural pyrolysis of petroleum due to the intrusion of volcanic dykes or hydrothermal processes an artificial generation of olefins during sample work up and analysis is unlikely the preservation of alk 1 enes from palaeozoic times was possible due to the protecting environment of petroleum inclusions

glaciovolcanic hydrothermal environments in iceland and implications for their detection on mars abstract volcanism has been a dominant process on mars along with a pervasive global cryosphere therefore the interaction between these two is considered likely terrestrial glaciovolcanism produces distinctive lithologies and alteration terrains as well as hydrothermal environments that can be inhabited by microorganisms here we provide a framework for identifying evidence of such glaciovolcanic environments during future mars exploration and provide a descriptive reference for active hydrothermal environments to be utilised for future astrobiological studies remote sensing data were combined with field observations and sample analysis that included x ray diffraction raman spectroscopy thin section petrography scanning electron microscopy electron dispersive spectrometer analysis and dissolved water chemistry to characterise samples from two areas of basaltic glaciovolcanism askja and kverkfjoll volcanoes in iceland the glaciovolcanic terrain between these volcanoes is characterised by subglacially erupted fissure swarm ridges which have since been modified by multiple glacial outburst floods active hydrothermal environments at kverkfjoll include hot springs anoxic pools glacial meltwater lakes and sulphur and iron depositing fumaroles all situated within ice bound geothermal fields temperatures range from 0 c 94 4 c and aqueous environments are acidic neutral ph 2 7 5 and sulphate dominated mineralogy of sediments mineral crusts and secondary deposits within basalts suggest two types of hydrothermal alteration a low temperature 120 c assemblage signified by zeolite heulandite and quartz these mineral assemblages are consistent with those identified at the martian surface in situ and laboratory vnir 440 1000 nm reflectance spectra representative of mars rover multispectral imaging show sediment spectral profiles to be influenced by fe2 3 bearing minerals regardless of their dominant bulk mineralogy characterising these terrestrial glaciovolcanic deposits can help identify similar processes on mars as well as identifying palaeoenvironments that may once have supported and preserved life

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

reservoir origin and characterization of gas pools in intrusive rocks of the yingcheng formation songliao basin ne china abstract in 2013 the first discovery of gas pools in well ls 208 in intrusive rocks of the songliao basin sb ne china was made in the 2nd member of the yingcheng formation in the yingtai rift depression proving that intrusive rocks of the sb have the potential for gas exploration however the mechanisms behind the origin of reservoirs in intrusive rocks need to be identified for effective gas exploration the gas pool in intrusive rocks can be characterized as a low abundance high temperature normal pressure methane rich and lithologic pool based on integrated coring logging seismic and oil test methods the intrusive rocks show primary and secondary porosities such as shrinkage fractures sf spongy pores sp secondary sieve pores ssp and tectonic fractures tf the reservoir is of the fracture pore type with low porosity and permeability a capillary pressure curve for mercury intrusion indicates small pore throat size negative skewness medium high displacement pressure and middle low mercury saturation the development of fractures was found to be related to the quenching effects of emplacement and tectonic inversion during the middle late campanian sp and ssp formed during two phases the first phase occurred during emplacement of the intrusive rock in the late albian when the intrusions underwent alteration by organic acids the second phase occurred between the early cenomanian and middle campanian when the intrusions underwent alteration by carbonic acid the sf formed prior to oil charging the ssp sp formed during oil charging and the tf formed during the middle late campanian and promoted the distribution of gas pools throughout the reservoir the intrusive rocks in the sb and the adjacent basins were emplaced in the mudstone and coal units and have great potential for gas exploration

hydrothermal plumes above the east scotia ridge an isolated high latitude back arc spreading centre we have identified first evidence for the presence of submarine hydrothermal activity along the east scotia ridge an isolated back arc spreading centre located at 55 60 s in the atlantic sector of the southern ocean using a combination of in situ optical light scattering sensor data and total dissolvable mn concentrations we demonstrate the existence of hydrothermal plumes overlying two segments of this 500 km ridge crest both segments exhibit anomalous topography and at least one segment is also underlain by an axial magma chamber seismic reflector future investigation of the fauna that inhabit these remote hydrothermal environments may provide an important missing link between the distinct biogeographical provinces delimited from previous investigation of northern atlantic versus eastern pacific vent sites

low temperature alteration of serpentinized ultramafic rock and implications for microbial life abstract alteration serpentinization of ultramafic rocks is known to generate hydrogen through oxidation of ferrous iron in olivine or pyroxene and reduction of water hydrogen oxidation can act as a primary source for chemolithotrophic microbial communities and it is suggested that hydrogen availability is essential for the existence of a deep subsurface biosphere in this study we focus on ongoing low temperature water rock processes in partially serpentinized dunite from the leka ophiolite complex mid norway we aim to determine whether these reactions release reduced compounds and nutrients that can be utilized by the associated microbial communities the study is based on the chemical and physical alteration features of a 51 m deep rock core as well as the chemical composition of groundwater from the core s borehole the borehole intersects three main fracture zones observations during drilling indicated that water infiltration largely takes place along the deepest zone the rock in the fracture zones is nearly completely altered to serpentine brucite magnetite and minor calcite an increase in ph and decrease in mg si and alkalinity of the groundwater along the borehole from the deepest to the outermost fracture zone reflect ongoing water rock reactions where dissolution of brucite serpentine and calcite and precipitation of chrysotile hydromagnesite and iron hydroxide are most likely to occur detection of both h 2 and o 2 in the groundwater influenced by the outermost fracture zone suggests that the local development of highly reducing conditions in the narrow fractures is due to low water rock ratios and to dissolution of fe ii containing brucite and serpentine resulting in the formation and successive diffusion of h 2 into the oxic borehole oxidation of h 2 reduced fe and mn nh 4 and ch 4 are all potential energy yielding reactions that could be utilized by chemolithotrophic microorganisms using dissolved organic or inorganic carbon as possible carbon sources methane could result from microbial oxidation of h 2 and reduction of co 2 or from the degradation of organic matter the results demonstrate that low temperature water rock reactions in serpentinized ultramafic rock lead to production of reduced chemical species that could support primary producers in diverse microbial communities

effects of rapid thermal alteration on coal geochemical and petrographic signatures in the springfield no 5 coal illinois basin abstract igneous intrusion into a coal bed can change the geochemical and petrographic properties of the coal including vitrinite reflectance maceral petrographic composition optical texture mineralogy stable isotope composition trace element composition and bulk geochemistry the intent of this study was to evaluate petrographic and geochemical changes in an intruded coal and compare them to trends seen in coals altered by normal burial maturation thereby evaluating whether or not the intruded coals followed a different maturation pathway the current study reports petrographic bulk geochemical proximate ultimate leco total organic carbon toc and rock eval pyrolysis data for a suite of samples from the springfield no 5 coal pennsylvanian desmoinesian in the southern part of the illinois basin where the coal had been intruded by a permian age peridotite dike petrographic analysis shows an increase in vitrinite reflectance rm from background levels of 0 55 0 63 up to 4 80 a loss in ability to differentiate liptinite macerals formation of isotropic coke and at the dike coal contact development of fine grained mosaic anisotropic coke texture volatile matter vm content decreases and fixed carbon fc content ash and mineral matter parr formula increase approaching the intrusion contact carbon increases whereas nitrogen hydrogen and oxygen decrease approaching the intrusion the presence of carbonate minerals confirmed by x ray diffraction and petrographic analysis has a significant impact on proximate and ultimate data however even after removal of carbonates trends for vm vs rm c vs rm and h vs c do not follow typical trends associated with normal burial coalification approaching the contact leco toc rock eval free oil content s1 remaining hydrocarbon potential s2 co2 from pyrolysis of the organic matter s3 and hydrogen hi and oxygen oi indices decrease whereas thermal maturity tmax c increases s2 vs rm and tmax vs rm diverge from the pathways seen in previous studies of coals that have undergone normal burial maturation geochemical data from this study suggest that the intruded springfield no 5 coal may have followed a maturation track that differed from that seen under normal burial maturation perhaps due to the geologically rapid high heating event associated with the emplacement of the intrusion it is also suggested here that the natural coke textures produced by this rapid geological heating may differ from those observed for metallurgical cokes produced under standard industrial coking conditions typically in an industrial coke oven a coal of this initial rank ro 0 6 would produce an isotropic coke rather than the fine grained circular anisotropic coke seen here however as variations in heating rate duration of heating maximum temperatures attained hydrothermal conditions and pressure are mostly unknown for the intrusive event it is not unreasonable to suggest that differences in these variables contributed to the higher anisotropy of the coke alternatively the development of this texture may reflect pre heating of the coal during the intrusion event

a geochemical model for the formation of hydrothermal carbonates on mars it is often argued that substantially more carbon dioxide and water were degassed from the martian interior than can be found at present in the atmosphere polar caps and regolith calculations have shown that atmospheric escape cannot account for all of the missing volatiles suggestions that carbon dioxide is stored as marine or lacustrine deposits are challenged by earth based and spacecraft remote sensing data moreover recent modelling of the martian atmosphere suggests that rainfall or open bodies of water are in any case unlikely to have persisted for extended periods of time hydrothermal carbonates therefore provide a possible solution to this dilemma using an accessible terrestrial system iceland as a guide to the underlying processes and a host rock composition inferred from the least altered martian meteorite we present a geochemical model for the formation of carbonates in possible martian hydrothermal systems our results suggest that an extensive reservoir of carbonate minerals equivalent to an atmospheric pressure of carbon dioxide of at least one bar could have been sequestered beneath the surface by widespread hydrothermal activity in the martian past

volcano ground ice interactions in elysium planitia mars abstract the occurence within elysium planitia of meltwater deposits possible pseudocraters collapse features within troughs and outflow channels indicates that a layer of subsurface volatiles existed at the time of volcanic activity within this area the pseudocraters are interpreted to be indicators of near surface volatiles while meltwater deposits and the degree of preservation of trough walls and floors are thought to signify greater volatile depths a latitudinal variation in the distribution of these features indicates either that the depth to the volatile layer increased from less than about 50 m at 35 n to greater than 600 m at 24 n or that an ice wedge that existed at 35 n thinned to nonexistence at 24 n braided distributary channel systems within the chaotic terrain north of elysium planitia show that ephemeral lakes were repeatedly created and drained at this locality the existence of volatiles contemporaneous with volcanic activity permits a search to be made for explosively generated landforms predicted to exist by previous theoretical models morphological evidence for strombolian vulcanian and plinian eruptions is lacking within western elysium planitia there are no identifiable cinder cones pyroclastic flow deposits or mantled areas indicative of large airfall deposits at an image resolution of 50 150 m pixel however the pseudocraters indicate that small scale phreatomagmatic activity may have taken place

contact metamorphic devolatilization of shales in the karoo basin south africa and the effects of multiple sill intrusions abstract quantification of fluid generation during contact metamorphism of shale is important for the understanding of metamorphic processes fluid flow in sedimentary basins and perturbations of the global carbon cycle in this study we provide geochemical and numerical analyses from the organic rich ecca group in the karoo basin south africa which was affected by contact metamorphism from multiple sill intrusions in the early jurassic organic matter was efficiently converted to hydrocarbons during contact metamorphism and complete loss of organic carbon in the innermost aureole is common mineral dehydration reactions are evident from the occurrence of metamorphic minerals like biotite and loss of the clay fraction towards the intrusive contact we have developed a numerical model in order to quantify fluid production from both inorganic and organic reactions during contact metamorphism the modelling results are constrained by data from two case studies in the karoo basin in order to obtain reliable estimates of the carbon loss from metamorphism of shale we show that single thin 15 m thick sills have a gas production potential of several gigatons of methane ch4 if emplaced over a 1000 km2 area furthermore the vertical spacing between simultaneously emplaced sills has an important influence on the gas generation potential when two sills are emplaced with a vertical spacing of 7 times the intrusion thickness the total ch4 generation is up to 35 more than for two separate sills data and modelling from five sills emplaced within the ecca group show hydrocarbon generation throughout the organic rich section with total carbon loss next to the sills this has implications for the fluid production and metamorphism in volcanic basins where multiple sills are common

galileo s first images of jupiter and the galilean satellites the first images of jupiter io europa and ganymede from the galileo spacecraft reveal new information about jupiter s great red spot grs and the surfaces of the galilean satellites features similar to clusters of thunderstorms were found in the grs nearby wave structures suggest that the grs may be a shallow atmospheric feature changes in surface color and plume distribution indicate differences in resurfacing processes near hot spots on io patchy emissions were seen while io was in eclipse by jupiter the outer margins of prominent linear markings triple bands on europa are diffuse suggesting that material has been vented from fractures numerous small circular craters indicate localized areas of relatively old surface pervasive brittle deformation of an ice layer appears to have formed grooves on ganymede dark terrain unexpectedly shows distinctive albedo variations to the limit of resolution

thermal maturation pattern in the southern bowen northern gunnedah and surat basins northern new south wales australia abstract comprehensive maximum vitrinite telocollinite reflectance data have been obtained for more than 260 polished sections from 28 petroleum exploration wells in the southern bowen and northern gunnedah basins and the overlying surat basin in an area from north of boggabri to the new south wales queensland border the samples studied were coal and dispersed organic matter dom taken from ditch cuttings and drill cores of the permian triassic and jurassic sedimentary successions vitrinite reflectance profiles show that the coals and dom in the early permian back creek group of the southern bowen basin have anomalously low suppressed reflectance values and a higher reflectance gradient rate of increase in vitrinite reflectance with depth relative to the overlying late permian triassic and jurassic sequences suppression of vitrinite reflectance is recorded in the early permian maules creek and goonbri formations in the northernmost part of the gunnedah basin relative to the overlying triassic and jurassic sequences dispersed organic matter in the marine sediments of the watermark and porcupine formations of the gunnedah basin also shows suppression of vitrinite reflectance the vitrinite in several wells of the study area however displays anomalously high reflectance in parts of the sequence due to the influence of igneous intrusions after allowing for heat effects due to intrusions and anomalies due to marine influence the reflectance gradient over equivalent intervals in the southern bowen basin is higher towards the west where the permian sequence pinches out and the triassic sequence overlies the basement vitrinite reflectance also increases at a higher rate with depth close to the gil gil ridge in the east and close to the moree high in the south this may reflect additional heat flow associated with the basement high features the areas between the gil gil ridge and the goondiwindi thrust in the east and to the west of the gil gil ridge appear to have lower reflectance gradients and equivalent or lower reflectance values despite the greater burial depths

filling characteristics reservoir features and exploration significance of a volcanostratigraphic sequence in a half graben basin a case analysis of the wangfu rift depression in songliao basin ne china abstract it has long been considered that thicker volcanostratigraphic sequences should in theory contain more favourable reservoir conditions than in thinner sequences particularly within large scale stratovolcanoes found in sedimentary basins however drilling results from the wangfu rift depression wrd in the songliao basin china show that the thick intermediate volcanostratigraphic sequence contains only one or two layers of favourable reservoir characteristics over approximately 1000 m of volcanic successions the volcanostratigraphic sequence that is common in the graben basin has a particular distribution pattern as a result of reservoir and origin processes the eruptive interval unconformity boundary eiub is introduced and the burial history is investigated in order to determine the reservoir characteristics and origin we also identify what controls the gas pool accumulation in the thick intermediate volcanostratigraphy according to the reworked volcanic rocks and weathered crust patterns the volcanostratigraphy of the basin has 13 wells containing one eiub and 2 wells with two eiubs the exposed and burial histories of the volcanostratigraphic sequence have produced a variety of pore space including primary pores secondary pores and secondary fractures the secondary pores are the most dominant followed by primary pores and finally fractures these pore spaces form a reservoir with moderate to low porosity and permeability and the most productive reservoirs are located 40 80 m below the eiub the secondary pores are primarily controlled by weathering and leaching as well as deep burial alteration due to the migration of fluids from the overlying strata into the volcanic rocks of the huoshiling formation below the top most layer dissolves first which significantly enhances the secondary porosity of this layer found 40 80 m below the eiub thus the number of eiubs should control the number of favourable reservoir layers based on analysis of the reservoir source and cap rocks in the study area we conclude that the best exploration targets in these thick volcanostratigraphic sequences specifically in half graben basins are the volcanic inherited uplift slope areas followed by the inherited uplift of the sag area and the uplifted zones the findings presented in this work provide an insight of the evolution of porosity in other volcanic systems elsewhere and contribute to the likelihood of locating the favourable exploration targets for thick volcanostratigraphic sequences in half graben basins

alteration mineralogy of home plate and columbia hills formation conditions in context to impact volcanism and fluvial activity the mars exploration rover spirit investigated the igneous and alteration mineralogy and chemistry of home plate and its surrounding deposits here we focus on using thermochemical modeling to understand the secondary alteration mineralogy at the home plate outcrop and surrounding columbia hills region in gusev crater at high temperatures 300 c magnetite occurs at very high w r ratios but the alteration assemblage is dominated by chlorite and serpentine over most of the w r range quartz epidote and typical high t phases such as feldspar pyroxene and garnet occur at low w r at epithermal temperatures 150 c hematite occurs at very high w r a range of phyllosilicates including kaolinite nontronite chlorite and serpentine are precipitated at specific w r amphibole with garnet feldspar and pyroxene occur at low w r if the co2 content of the system is high the assemblage is dominated by carbonate with increasing amounts of an sio2 phase kaolinite carpholite and chlorite with lower w r at temperatures of hydrous weathering 13 c the oxide phase is goethite silicates are chlorite nontronite and talc plus an sio2 phase in the presence of co2 the mineral assemblage at high w r remains the same and only at low w r i e with increasing salinity carbonate precipitates the geochemical gradients observed at home plate are attributed to short lived initially high 300 c temperature but fast cooling events which are in agreement with our models and our interpretation of a multistage alteration scenario of home plate and gusev in general alteration at various temperatures and during different geological processes within gusev crater has two effects both of which increase the habitability of the local environment precipitation of hydrous sheet silicates and formation of a brine which might contain elements essential for life in diluted easily accessible form

martian plate tectonics the northern lowlands of mars may have been produced by plate tectonics preexisting old thick highland crust was subducted while seafloor spreading produced thin lowland crust during late noachian and early hesperian time in the preferred reconstruction a breakup margin extended north of cimmeria terra between daedalia planum and isidis planitia where the highland lowland transition is relatively simple south dipping subduction occurred beneath arabia terra and east dipping subduction beneath thatsis montes and tempe terra lineations associated with gordii dotsum are attributed to ridge parallel structures while phelegra montes and scandia colles are interpreted as transform parallel structures or ridge fault fault triple junction tracks other than for these few features there is little topographic roughness in the lowlands seafloor spreading if it occurred must have been relatively rapid quantitative estimates of spreading rate are obtained by considering the physics of seafloor spreading in the lower c 0 4 g gravity of mars the absence of vertical scarps from age differences across fracture zones and the smooth axial topography to the first order the height of vertical scarps across fracture zones does not involve gravity crustal thickness at a given potential temperature in the mantle source region scales inversely with gravity thus the velocity of the rough smooth transition for axial topography also scales inversely with gravity plate reorganizations where young crust becomes difficult to subduct are another constraint on spreading age possible plate reorganizations for example the end of spreading through alba patera occur when the ridge axis is far from the trench that is rapid plate motions are inferred to have placed young oceanic crust far from the ridge axis the preferred full spreading rate 900 from the plate pole is 80 mm yr 1 plate tectonics if it occurred dominated the thermal and stress history of the planet a geochemical implication is that the lower gravity of mars allows deeper hydrothermal circulation through cracks and hence more hydration of oceanic crust so that more water is easily subducted than on the earth age and structural relationships from photogeology as well as median wavelength gravity anomalies across the now dead breakup and subduction margins are the data most likely to test and modify hypotheses about mars plate tectonics

experimental epithermal alteration of synthetic los angeles meteorite implications for the origin of martian soils and identification of hydrothermal sites on mars 1 the dissolution behavior and secondary minerals generated by experimental alteration of a synthetic los angeles basaltic shergottite la were evaluated at epithermal 75 c conditions starting ph values of 1 1 and 3 6 and water rock ratios ranging from 100 to 2000 were studied using flow through and batch reactor experimental apparatus dissolution of plagioclase dominates effluent solution chemistry under all experimental conditions little mg is released to solution because nearly 100 of the mg in unaltered la is contained in pyroxene m1 sites which are relatively resistant to dissolution secondary minerals generated include siliceous residue amorphous sio2 lepidocrocite and ferrihydrite anhydrite alunogen rhomboclase ferrinatrite halite and unidentified ca and na sulfates the dominance of alteration products of plagioclase suggests that la type basalts have not contributed significantly to the martian soils the search for hydrothermal sites by remote sensing may be hampered by the general similarity of the alteration products found in the near surface epithermal environment to those thought to exist in martian soils sulfates iron oxyhydroxides amorphous silica however the unique chemical composition of secondary products formed by la alteration may make detection of recent hydrothermal alteration of evolved basaltic rocks more straightforward in addition alteration in terrestrial epithermal environments associated with mafic to intermediate volcanic rocks generally produces abundant sulfides and kaolinite two potentially unique mineral phases which might also indicate the presence of active or extinct hydrothermal systems

geophysical controls of chemical disequilibria in europa the ocean in jupiter s moon europa may have redox balance similar to earth s on earth low temperature hydration of crustal olivine produces substantial hydrogen comparable to any potential flux from volcanic activity here we compare hydrogen and oxygen production rates of the earth system with fluxes to europa s ocean even without volcanic hydrothermal activity water rock alteration in europa causes hydrogen fluxes 10 times smaller than earth s europa s ocean may have become reducing for a brief epoch for example after a thermal orbital resonance 2 gyr after accretion estimated oxidant flux to europa s ocean is comparable to estimated hydrogen fluxes europa s ice delivers oxidants to its ocean at the upper end of these estimates if its ice is geologically active as evidence of geologic activity and subduction implies

geochemical bioenergetics during low temperature serpentinization an example from the samail ophiolite sultanate of oman abstract various classes of microbial and biomolecular evidence from global studies in marine and continental settings are used to identify a set of reactions that appear to support microbial metabolism during serpentinization of ultramafic rocks geochemical data from serpentinizing ecosystems in the samail ophiolite of oman are used to evaluate the extent of disequilibria that can support this set of microbial metabolisms and to provide a ranking of potential metabolic energy sources in hyperalkaline fluids that are direct products of serpentinization results are used to construct hypotheses for how microbial metabolism may be supported in the subsurface for two cases ecosystems hosted in rocks that have already undergone significant serpentinization and those hosted by deeper active serpentinization processes

scenarios for the evolution of life on mars received 10 march 2005 revised 2 august 2005 accepted 7 september 2005 published 22 november 2005 1 as the environmental histories of earth and mars have diverged drastically after the first few hundred million years so would the history of any life on them while earth has had liquid water on its surface for billions of years mars most likely had long dry and cold environments interspersed with warmer and wetter periods life thrived on earth but may have been severely restricted on mars there it could be present today in liquid water in or beneath ice sheets or glaciers in subterranean aqueous reservoirs especially in regions of elevated heat flow or in protected habitats such as lava tubes caves or cracks and fissures the potential for life is enhanced in regions where elevated heat flow may occur such as in parts of the tharsis and elysium volcanic provinces possible organisms would be chemoautotrophic psychrophiles adapted to a nutrient poor environment or photoautotrophic life in selected near surface habitats alternatively life may have evolved alternating cycles between active and dormant forms in which case microbes could be present in dormant forms close to the surface and in active forms in protected environments periodic liquid water on mars could have provided opportunities for biologic activity as well as evolutionary progress at the surface during the short lived climatic perturbations ancient organisms from any of these environments may also have left a detectable fossil record

search for signs of ancient life on mars expectations from hydromagnesite microbialites salda lake turkey the 9white rock9 constituting a portion of what may be a lacustrine sedimentary sequence near the margin of a crater c 90 km across in sabaea terra mars measures 18 15 km 180 540 m high it is re interpreted as a lens of magnesium carbonate precipitated where ground waters seeped into an ancient evaporating crater lake were life to have emerged on mars as seems feasible then the 9white rock9 might be expected to comprise a complex of stromatolitic mounds salda golu lake in turkey is taken as an analogue this enclosed lake is nearly surrounded and underlain by partially serpentinized harzburgite hydromagnesite stromatolites microbialites up to 7 m high coalesce to form a group of small islands 200 m across the microbialites are seen to be growing near the mouth of the usually dry salda river in the southwestern sector smaller developments of hydromagnesite encircle the lake and image processing of satellite data reveals a second extensive zone beneath the lake surface over a delta in the southeast individual columns a few centimetres high constitute bulbous mounds which are about 2 m in diameter these columns terminate in domes a centimetre or so across the domes are often annulated and are covered with a green biofilm a few millimetres thick comprised of cyanobactrial filaments the columns consist of alternating fine and coarse hydromagnesite layers differentiated on a millimetric scale the coarser layers near the surface still contain traces of the biofilm fossil microbialites were also discovered in the friable hydromagnesite cliffs shoreward of the main developments though the structures of the individual microbes have not survived instead the vestiges of microbialites are easily recognized and delineated by their coarse grain size and high porosity annular structures on their upper surfaces can be seen in places the intervening and overlying material also comprised of hydromagnesite is a semi lithified mud bulbous megascopic structures separated by finer grained magnesium carbonate mudstone within strata in the 9white rock9 would be strong evidence of a photosynthetic microbial genesis another deposit of white rock on the western margin of juventae chasma could have a similar origin

cretaceous volcanic reservoirs and their exploration in the songliao basin northeast china major reservoirs in the songliao basin sb are composed of volcanic rocks below 3000 m 9843 ft of buried depth gas accumulations are mostly found in the buried volcanic highs which in general correspond to paleovolcanic centers porosity in the volcanic rocks depends on both primary and secondary processes the best porosity is preferentially developed in a proximal facies near the central part of each volcanic edifice porosity and permeability decrease with depth of burial for both volcanic and nonvolcanic sections but their porosity depth trends differ lava and welded ignimbrite slowly lose porosity with burial depth because they solidified by cooling and their groundmasses are poor in quartz and calcite precipitation thus preserving porous space in contrast the associated sandstone conglomerate tuff and tuffite are more sensitive to overburden pressure suffering more intense compaction and cementation as a result porosity and permeability of lava and ignimbrite exceed that of the other rocks and thus they are the best reservoir rocks below burial depths of ca 3000 m 9843 ft in the sb the paleovolcanic domes are rich in both lava rocks and fractures of diverse origin and the topographic highs provide favorable locations for gas migration and accumulation

mixing relationships in the martian regolith and the composition of globally homogeneous dust abstract comparison of the chemical compositions of martian soils reveals distinct mixing trends resulting from admixture of variable amounts of sulfate chloride cement at viking landing sites and of the local andesitic rock fragments at the mars pathfinder site these trends most easily visualized in plots of oxides versus so 3 intersect approximately at a common composition thought to represent a global dust that has been homogenized by pervasive aeolian activity the source rocks that were weathered to produce the global dust are inferred to have been basalts rather than felsic rocks based on the observation that the dust lies along well established chemical weathering trends for terrestrial basalts the basaltic protolith was chemically similar e g high fe mg low al 2 o 3 to basaltic shergottite meteorites chemical changes during the weathering of martian basaltic rocks are apparently not as drastic as in terrestrial weathering perhaps because of evaporation of hydrous fluids that leave soluble components behind in the residue comparison with chemical trends for previously proposed martian soil formation mechanisms suggests that palagonitization of basalts more readily explains the dust composition than do hydrothermal alteration at higher temperatures or reactions of rocks with an acid fog produced by volcanic exhalations local or temporal processing of dust into soil involves not only cementation by salts and mixing with rock fragments but also chemical fractionations of fe 2 o 3 tio 2 presumably resulting from aeolian sorting by grain size and density if the global dust represents a broad average of the martian surficial or upper crustal composition the planet s surface geology is dominated by basaltic volcanic rocks and evaporitic salts

the biological potential of mars the early earth and europa the potential biomass that could have existed on mars is constrained by the total amount of energy available to construct it from an inventory of the available geochemical sources of energy we estimate that from the time of the onset of the visible geologic record 4 b y ago to the present as much as 20 g cm 2 of biota could have been created this is the same amount that could have been constructed on the early earth in only 100 million years this indicates that there likely was sufficient energy available to support an origin of life on mars but not sufficient energy to create a ubiquitous and lush biosphere similar calculations for europa suggest that even less geochemical energy would have been available there

hydrothermal hydration of martian crust illustration via geochemical model calculations if hydrothermal systems existed on mars hydration of crustal rocks may have had the potential to affect the water budget of the planet we have conducted geochemical model calculations to investigate the relative roles of host rock composition temperature water to rock ratio and initial fluid oxygen fugacity on the mineralogy of hydrothermal alteration assemblages as well as the effectiveness of alteration to store water in the crust as hydrous minerals in order to place calculations for mars in perspective models of hydrothermal alteration of three genetically related icelandic volcanics a basalt andesite and rhyolite are presented together with results for compositions based on snc meteorite samples shergotty and chassigny temperatures from 150 c to 250 c water to rock ratios from 0 1 to 1000 and two initial fluid oxygen fugacities are considered in the models model results for water to rock ratios less than 10 are emphasized because they are likely to be more applicable to mars in accord with studies of low grade alteration of terrestrial rocks we find that the major controls on hydrous mineral production are host rock composition and temperature over the range of conditions considered the alteration of shergotty shows the greatest potential for storing water as hydrous minerals and the alteration of icelandic rhyolite has the lowest potential

sulfur bearing phases detected by evolved gas analysis of the rocknest aeolian deposit gale crater mars the sample analysis at mars sam instrument suite detected so2 h2s ocs and cs2 from 450 to 800 c during evolved gas analysis ega of materials from the rocknest aeolian deposit in gale crater mars this was the first detection of evolved sulfur species from a martian surface sample during in situ ega so2 3 22 mol is consistent with the thermal decomposition of fe sulfates or ca sulfites or evolution desorption from sulfur bearing amorphous phases reactions between reduced sulfur phases such as sulfides and evolved o2 or h2o in the sam oven are another candidate so2 source h2s 41 109 nmol is consistent with interactions of h2o h2 and or hcl with reduced sulfur phases and or so2 in the sam oven ocs 1 5 nmol and cs2 0 2 1 nmol are likely derived from reactions between carbon bearing compounds and reduced sulfur sulfates and sulfites indicate some aqueous interactions although not necessarily at the rocknest site fe sulfates imply interaction with acid solutions whereas ca sulfites can form from acidic to near neutral solutions sulfides in the rocknest materials suggest input from materials originally deposited in a reducing environment or from detrital sulfides from an igneous source the presence of sulfides also suggests that the materials have not been extensively altered by oxidative aqueous weathering the possibility of both reduced and oxidized sulfur compounds in the deposit indicates a nonequilibrium assemblage understanding the sulfur mineralogy in rocknest materials which exhibit chemical similarities to basaltic fines analyzed elsewhere on mars can provide insight in to the origin and alteration history of martian surface materials

mars a water rich planet abstract mars had outgassed at least 0 5 to 1 km of water 10 to 20 bar of co2 and 0 1 to 0 3 bar of n2 the volatiles that have been retained are mostly in the cratered uplands terrain softening fretted channels debris flows and closed depressions indicate that at least the upper 2 km of the cratered uplands at high latitudes 30 contain ice in amounts that exceed the porosity estimated to be 10 20 theoretical studies and lack of these features in the cratered uplands at low latitudes suggest that the upper 1 km of the uplands at low latitudes is ice poor however valley networks indicate that water was present near the surface early in the planet s history although in amounts smaller than at high latitudes the entire upper 1 km planetwide is estimated to have contained 75 125 m of water at the end of heavy bombardment the largest sink for water is the megaregolith below 1 km episodic eruption of water from the deep megaregolith cut many of the large outflow channels from the volume of water needed to cut the circum chryse channels and assuming uniform planetwide distribution of water the deep megaregolith is estimated to have contained at least 350 m of water at the end of heavy bombardment thereby giving a total minimum inventory of 424 475 m planetwide most of the water lost from the low latitude uplands by diffusion and in cutting the valley networks is now believed to be in the polar layered terrains most of the water involved in cutting the outflow channels is in the low lying northern plains where a variety of features that have been attributed to ground ice is present a large fraction of the planet s surface has been overplated with water poor volcanics of which we have samples in the snc meteorites the younger volcanics have reacted extensively with the old volatile rich basement some of the co2 and n2 outgassed was lost during heavy bombardment by impact erosion of the atmosphere and other processes the remaining was fixed carbonates and folded deep into the megaregolith during heavy bombardment

explosive lava water interactions in elysium planitia mars geologic and thermodynamic constraints on the formation of the tartarus colles cone groups 1 volcanic rootless constructs vrcs are the products of explosive lava water interactions vrcs are significant because they imply the presence of active lava and an underlying aqueous phase e g groundwater or ice at the time of their formation combined mapping of vrc locations age dating of their host lava surfaces and thermodynamic modeling of lava substrate interactions can therefore constrain where and when water has been present in volcanic regions this information is valuable for identifying fossil hydrothermal systems and determining relationships between climate near surface water abundance and the potential development of habitable niches on mars we examined the western tartarus colles region 25 27 n 170 171 e in northeastern elysium planitia mars and identified 167 vrc groups with a total area of 2000 km2 these vrcs preferentially occur where lava is 60 m thick crater size frequency relationships suggest the vrcs formed during the late to middle amazonian modeling results suggest that at the time of vrc formation near surface substrate was partially desiccated but that the depth to the midlatitude ice table was 42 m this ground ice stability zone is consistent with climate models that predict intermediate obliquity 35 between 75 and 250 ma with obliquity excursions descending to 25 32 for lava thicknesses ranging from 30 to 60 m and ground ice fractions ranging from 0 1 to 0 3 an ice volume of 4 23 km3 could have been melted and or vaporized by the time the lava solidified and the associated hydrothermal systems could have retained temperatures 273 k for up to 1300 years

origin and ore forming consequences of the advanced argillic alteration process in hypogene environments by magmatic gas contamination of meteoric fluids metasomatic effects have been thermodynamically computed for magma derived sulfur gases which may contaminate convecting meteoric fluids in the monzonite k silicate protore and are compared with natural assemblages in the butte district of montana the advanced argillic assemblage with covellite is produced in hypogene environments at 300 degrees c by sulfur metasomatism of protore only for a limited range of net sulfur valences essentially 1 to 2 placing limiting constraints on the possible ratios of so 2 and h 2 s gases a second important factor is the relative reaction rates of protore and contaminating sulfur gases contamination by sulfur gases is a third factor of importance a final factor is that a minimum negative net volume of reaction causes by wall rock dissolution and fracture enlargement the high permeability necessary for circulation of enormous quantities of hydrothermal fluids and vein growth characteristic of this extreme alteration facies modified journal abstract

a resolution of discrepant thermodynamic properties for chamosite retrieved from experimental and empirical techniques an important deficiency in the thermodynamic data for common rock forming minerals involves chamosite the fe2 end member of chlorite solid solution the ag3 and al13 values for chamosite reported in the literature as computed from both phase equilibria data and empirical approaches exhibit huge discrepancies of up to 210 kj mol a small portion of the discrepancy 5 100 o is related to inconsistencies in the al reference state chosen for the thermodynamic retrieval calculations it is shown that the remainder can be assigned to an improper application of the van t hoffrelationship to compute standardstate thermodynamic properties 25 c i bar for chamosite from equilibrium constants derived from high temperature 575 625 c and high pressure 2 07 6 00 kbar phaseequilibria experiments we have reinterpreted these previously published experimental results by taking explicit account ofheat capacity and entropy data for chamosite predicted from additivity models following this approach we compute ag and afii for chamosite of 6495 13 4 17 and 7101 91 4 17 kj mol respectively values that are in excellent agreement with those computed from empirical techniques after inconsistencies reiated to the al reference state are taken into account in this way major discrepancies in previously reported thermodynamic data for chamosite are resolved

major episodes of geologic history of isidis planitia on mars abstract we have mapped the area of isidis planitia 1 27 n 75 103 e in order to assess the geologic history of this region using modern data sets such as mola topography and the high resolution images provided by the hrsc ctx and hirise cameras results of our mapping show that the geologic history of isidis planitia consists of three principal episodes 1 impact dominated episode noachian until 3 8 ga during this time the oldest materials in the study area were formed mostly by impact reworking and mass wasting other processes e g volcanism and fluvial glacial activity likely operated at this time but played a subordinate role 2 an episode related to volcanic and fluvial glacial activities late noachian early amazonian 3 8 2 8 ga volcanism appears as the most important process at the beginning of this episode 3 8 3 5 ga and was responsible for the formation of a large circum isidis volcanic province by the early hesperian epoch volcanic materials covered large portions of the isidis rim almost completely buried the previous crater record on the floor of the isidis basin and probably were the major contributors to the filling of the basin fluvial glacial processes prevailed closer to the end of the episode early hesperian early amazonian 3 5 2 8 ga and were responsible for widespread resurfacing in the isidis planitia region mostly at 3 1 3 4 ga glaciers and or ice sheets probably resulted in a massive glaciation of the rim and the floor of the isidis basin the total volume of material eroded from the isidis rim by glacial and fluvial activity is estimated to be about 35 000 50 000 km 3 which is equivalent to a composite layer about 40 60 m thick on entire floor of the basin more important however is that the eroded materials were likely saturated with ice water and could form wet deposits on the floor 3 wind dominated episode since early amazonian 2 8 ga wind activity dominated the later geologic history of isidis planitia but resulted only in minor modification of the surface

calcium dominated organans in humic podzols from the hudson and james bay lowlands of ontario canada abstract the sem edxra analysis of cutans within five humic podzolic soils derived from calcareous sands and gravels revealed the presence of ca dominated organans it is postulated that organic matter saturated by h and al is translocated through the ae horizon and precipitated within the bh horizon in the presence of calcareous material weathering of the calcareous material within the bh horizon results in the partial replacement of the h and al in the organans by ca

new insights into gully formation on mars constraints from composition as seen by mro crism over 100 martian gully sites were analyzed using orbital data collected by the compact reconnaissance imaging spectrometer for mars crism and high resolution imaging science experiment hirise on the mars reconnaissance orbiter mro most gullies are spectrally indistinct from their surroundings due to mantling by dust where spectral information on gully sediments was obtained a variety of mineralogies were identified their relationship to the source rock suggests that gully forming processes transported underlying material downslope there is no evidence for specific compositions being more likely to be associated with gullies or with the formation of hydrated minerals in situ as a result of recent liquid water activity seasonal co2 and h2o frosts were observed in gullies at mid to high latitudes consistent with seasonal frost driven processes playing important roles in the evolution of gullies our results do not clearly indicate a role for long lived liquid water in gully formation and evolution

the fate of early mars lost water the role of serpentinization the fate of water which was present on early mars remains enigmatic we propose a simple model based on serpentinization a hydrothermal alteration process which may produce magnetite and store water our model invokes serpentinization during about 500 to 800 myr while a dynamo is active which may have continued after the formation of the crustal dichotomy we show that the present magnetic field measured by mgs in the southern hemisphere is consistent with a 500 m thick global equivalent layer of water trapped in serpentine serpentinization results in the release of h 2 the released h atoms are lost to space through thermal escape increasing the d h ratio in water reservoirs exchanging with atmosphere we show that the value of the d h ratio in the present atmosphere 5 is consistent with the serpentinization of a 500 m thick water gel we reassess the role of non thermal escape in removing water from the planet by considering an updated solar wind ionosphere interaction representation we show that the contribution of oxygen escape to h isotopic fractionation is negligible our results suggest that significant amounts of water up to a 330 1030 m thick gel present at the surface during the noachian similar to the quantity inferred from the morphological analysis of valley networks could be stored today in subsurface serpentine 1 the study like earth mars has been endowed with large amounts of water during accretion equivalent to the content of several terrestrial oceans corresponding to a several 10 km thick global equivalent layer the present inventory of observable water on mars mainly within the polar caps is quite smaller in the range from 20 30 m the mega regolith capacity is large with up to 500 gel m potentially trapped in the cryosphere and hypothetically several additional hundreds of meters up to 500 m of ground water surviving at depth below the cryosphere 1 a 500 m thick gel is generally assumed to be required to explain the formation of outflow channels 2 and most of this water could be trapped today as water ice and possibly deep liquid water in the subsurface and also possibly under the form of hydrated minerals

role of impact excavation in distributing clays over noachian surfaces 1 spectrometers have detected clay bearing units in and on much of the ancient martian crust geothermally heated aquifers in basaltic rock provide conditions conducive to forming fe mg phyllosilicates at depth throughout the noachian period a high flux of km scale bolides excavated buried materials and distributed them over the surface we use the maxwell z model to quantify the volume and final location of excavated clay bearing material we focus on two potentially detectable properties the volume of clay bearing material ejected as a fraction of total ejected volume and the volume percentage of clay bearing material in the ejecta as a function of distance from the crater s rim generally the volume percentage of clays in the ejecta is greatest for craters less than 25 km in diameter larger crater sizes incorporate a higher fraction of clay poor material because they excavate to greater depths at which clays are likely absent specific trends in bulk clay volume fraction and the distribution of clay fraction across the ejecta deposit as a function of crater size depend on the depth to the clay rich layer and its thickness impact excavation likely explains clays associated with ejecta deposits and may reveal clues about the volatile content and stratigraphy of the upper noachian crust applying our model to the mawrth vallis region suggests that a clay layer a few hundred meters thick is buried at the 3000 m elevation contour given that clay layers are likely thin and buried in the upper 3 km of the crust we predict that small to mid sized craters 25 km will best exhibit detectable amounts of clays and that these clays will be most abundant in the crater wall and rim and less so in distal ejecta

expanding frontiers in deep subsurface microbiology abstract the subsurface biosphere on earth appears to be far more expansive and physiologically and phylogenetically complex than previously thought here several aspects of subsurface microbiology are discussed molecular and biogeochemical data as well as characteristics from new isolates suggest that ecosystems below deep sea hydrothermal vents are inhabited primarily by thermophilic archaea and bacteria the void spaces and conduits in basalt at mid ocean ridges and even more so at sediment covered hydrothermal vent sites represent promising hunting grounds for novel chemosynthetic archaea and bacteria as examples we highlight the subsurface microbial communities within the basalt flanks of the juan de fuca ridge off british columbia and the hydrothermal sediments at the guaymas basin in the gulf of california and at middle valley on the juan de fuca ridge in the deep continental subsurface microbial studies have primarily targeted aquifers in basaltic and granitic rock with an almost exclusive emphasis on h2 driven chemolithoautotrophy for example in the subsurface water from lidy hot springs idaho usa h2 consuming methanogenic archaea represent the most populous organisms comprising 95 of all cells besides h2 other potential sources of chemical energy reducing power are considered including abiotically synthesized organic matter and reduced sulfur compounds in addition the well established sequences of redox couples in microbial metabolism are investigated at elevated temperatures using a thermodynamic approach values of peo for 11 common reduction half reactions are tabulated at 25 50 100 and 150 c although many modes of metabolism may be employed by subsurface biota sulfate reduction appears to be one of the more ubiquitous strategies recent studies of sulfate reducing archaea and bacteria in marine and continental systems are reviewed

sources of nutrients and energy for a deep biosphere on mars hydrothermal vents appear to be the tip of the subsurface biosphere in the ocean crust the primary prducers in this biosphere are prokaryotes that tolerate a wide variety of physical and chemical conditions and are versatile in their use of inorganic compounds to drive metabolism a synthesis of chemical and mineralogical data from martian meteorites and measurements of the martian surface suggest that conditions similar to those that make life possible in earth s oceanic crust namely water carbon nutrients appropriate temperatures and gradients in redox conditions also occur within mars chemolithoautotrophic microorganisms capable of living below the seafloor on earth would probably survive in some regions of the martian subsurface

hydrocarbon reservoirs in a trachyte porphyry intrusion in the eastern depression of the liaohe basin northeast china hydrocarbon reservoirs in the oulituozi area of the liaohe basin northeastern china occur within a subvolcanic trachyte porphyry intrusion this intrusion was emplaced at a depth of less than 1 km during the paleogene the prevalent reservoir porosity is in explosive breccias fracture networks steeply dipping cracks and dilational microfractures in the apical zone of the intrusion these voids were formed by underground explosion during magma solidification and by postsolidification volume contraction minor oil and gas volumes are trapped also in fractures in the overlying brittle beds the massive rocks in the lower part of the porphyry body serve as hydrocarbon seals for reservoir beds lateral to the intrusion we propose a model for reservoir formation related to a subvolcanic intrusion that includes three types of reservoirs 1 reservoirs in the apical zone of the intrusion 2 reservoirs in the upper wall of the intrusion and 3 reservoirs lateral to the intrusion attention should be paid to all the three reservoir types during exploration around a subvolcanic intrusion

experimental abiotic synthesis of methanol in seafloor hydrothermal systems during diking events abstract the abiotic synthesis of organic compounds in seafloor hydrothermal systems is one mechanism through which the subsurface environment could be supplied with reduced carbon a flow through fixed bed laboratory reactor vessel the catalytic reactor vessel crv system has been developed to investigate mineral surface promoted organic synthesis at temperatures up to 400 c and pressures up to 30 mpa conditions relevant to seafloor hydrothermal systems here we present evidence that metastable methanol can be directly synthesized from a gas rich co2 h2 h2o mixture in the presence of a mineral substrate experiments have been performed without a substrate with quartz and with a mixture of quartz and magnetite temperatures and pressures in the experiments ranged from 200 c to 350 c and from 15 to 18 mpa respectively maximum conversion of 5 8 10 4 co2 to ch3oh per hour was measured using a mixture of magnetite and quartz in the reactor after passivation of the stainless steel reactor vessel experiments demonstrate that methanol is formed at temperatures up to 350 c in the presence of magnetite and that the formation rate decreases over time the experiments also show a loss of surface reactivity at 310 c and a regeneration of surface reactivity with increased temperature up to 350 c concentrations of co2 and h2 used in the experiments simulate periodic localized and dynamic conditions occurring within the seafloor during and immediately following magmatic diking events high concentrations of co2 and h2 may be generated by dike injection accompanied by exsolution of co2 and reaction of dissolved h2o with feo in the magma to form h2 the experiments described here examine how the ephemeral formation of an h2 co2 rich vapor phase within seafloor hydrothermal systems may supply reactants for abiotic organic synthesis reactions these experiments show that the presence of specific minerals can promote the abiotic synthesis of simple organic molecules from common inorganic reactants such h2o co2 and h2 under geologically realistic conditions

polymeric substances and biofilms as biomarkers in terrestrial materials implications for extraterrestrial samples organic polymeric substances are a fundamental component of microbial biofilms microorganisms especially bacteria secrete extracellular polymeric substances eps to form slime layers in which they reproduce in the sedimentary environment biofilms commonly contain the products of degraded bacteria as well as allochthonous and autochthonous mineral components they are complex structures which serve as protection for the colonies of microorganisms living in them and also act as nutrient traps biofilms are almost ubiquitous wherever there is an interface and moisture liquid liquid liquid solid liquid gas solid gas in sedimentary rocks they are commonly recognized as stromatolites we also discuss the distinction between bacterial biofilms and prebiotic films the eps and cell components of the microbial biofilms contain many cation chelation sites which are implicated in the mineralization of the films eps biofilms and their related components thus have strong preservation potential in the rock record fossilized microbial polymeric substances fps and biofilms appear to retain the same morphological characteristics as the unfossilized material and have been recognized in rock formations dating back to the early archaean 3 5 b y we describe fps and biofilms from hot spring deep sea volcanic lake and shallow marine littoral environments ranging up to 3 5 b y in age fps and biofilms are more commonly observed than fossil bacteria themselves especially in the older part of the terrestrial record the widespread distribution of microbial biofilms and their great survival potential makes their fossilized remains a useful biomarker as a proxy for life with obvious application to the search for life in extraterrestrial materials

energy for biologic sulfate reduction in a hydrothermally formed ocean on europa 1 formation of a sulfate bearing ocean on jupiter s satellite europa by quenched hydrothermal fluids provides a source of metabolic energy for low temperature sulfate reducing organisms that use dissolved h2 as an electron donor inhibition of thermodynamically favorable sulfate reduction in cooled hydrothermal fluids creates the potential for biologic reduction both high temperature and reduced conditions of ocean forming hydrothermal solutions favor sulfate reduction in quenched fluids the maximum amount of energy available to support autotrophic sulfate reduction is on the order of a few kilojoules per kilogram of water and is limited by the low abundances of either h2 or sulfate in ocean forming fluids although this irreplaceable energy source might have supported early life on europa maintenance of biologic sulfate reduction throughout the ocean s history would require a supply of organic compounds from endogenic sources or from the satellite s surface

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

chemical components of the martian soil melt degassing hydrothermal alteration and chondritic debris on the basis of measurements by the viking and soviet phobos missions the fine grained surficial drift material on mars is enriched in moderately volatile and mobile elements such as s cl k and br the compounds of these elements may amount to as much as 16 wt of the soil while the bulk of the soil appears to consist primarily of crustal material whose composition is similar to that of the basaltic mars meteorites clark 1993 three possible geochemical sources melt degassing hydrothermal alteration and accretion of chondritic material may have contributed to the enrichments we have evaluated possible chemical signatures for these sources by examining the relative abundances of chemical elements in the different components to the measured k abundance in the mars soil and have identified characteristic elements for each component the relative abundances of mobile elements in the different components are much less variable than their absolute abundances which strongly depend on conditions such as temperature and water composition the volatility controlled elemental signature of the melt degassing process includes enrichments of zn mo cd ba and w relative to the elemental abundances in the other components and martian meteorites hydrothermal alteration of minerals and glass controlled by low temperature solubility makes up a second component with a characteristic lithium enrichment signature a chondritic component is enriched in siderophile and chalcophile elements including ni compared to material derived from the martian mantle which was depleted in siderophile elements due to core formation unfortunately the existing data for the mars soil do not include any of these key signature elements and the uncertainties for the viking analyses could allow large amounts of each of these elements the mars pathfinder inorganic analysis experiment and the 2001 orbital gamma ray experiment have the potential to determine some of these characteristic elements and to reveal the possible contributions to the soil the enriched components of the soil especially cd and pb could also be a potential hazard for future martian explorers who will be exposed to the dust carried into their habitats on their space suits

mineralogic and compositional properties of martian soil and dust results from mars pathfinder mars pathfinder obtained multispectral elemental magnetic and physical measurements of soil and dust at the sagan memorial station during the course of its 83 sol mission we describe initial results from these measurements concentrating on multispectral and elemental data and use these data along with previous viking snc meteorite and telescopic results to help constrain the origin and evolution of martian soil and dust we find that soils and dust can be divided into at least eight distinct spectral units based on parameterization of imager for mars pathfinder imp 400 to 1000 nm multispectral images the most distinctive spectral parameters for soils and dust are the reflectivity in the red the red blue reflectivity ratio the near ir spectral slope and the strength of the 800 to 1000 nm absorption feature most of the pathfinder spectra are consistent with the presence of poorly crystalline or nanophase ferric oxide s sometimes mixed with small but varying degrees of well crystalline ferric and ferrous phases darker soil units appear to be coarser grained compacted and or mixed with a larger amount of dark ferrous materials relative to bright soils nanophase goethite akaganeite schwertmannite and maghemite are leading candidates for the origin of the absorption centered near 900 nm in imp spectra the ferrous component in the soil cannot be well constrained based on imp data alpha proton x ray spectrometer apxs measurements of six soil units show little variability within the landing site and show remarkable overall similarity to the average viking derived soil elemental composition differences exist between viking and pathfinder soils however including significantly higher s and cl abundances and lower si abundances in viking soils and the lack of a correlation between ti and fe in pathfinder soils no significant linear correlations were observed between imp spectral properties and apxs elemental chemistry attempts at constraining the mineralogy of soils and dust using normative calculations involving mixtures of smectites and silicate and oxide minerals did not yield physically acceptable solutions we attempted to use the pathfinder results to constrain a number of putative soil and dust formation scenarios including palagonitization and acid fog weathering while the pathfinder soils cannot be chemically linked to the pathfinder rocks by palagonitization this study and mcsween et al 1999 suggest that palagonitic alteration of a martian basaltic rock plus mixture with a minor component of locally derived andesitic rock fragments could be consistent with the observed soil apxs and imp properties

does europa have a subsurface ocean evaluation of the geological evidence it has been proposed that jupiter s satellite europa currently possesses a global subsurface ocean of liquid water galileo gravity data verify that the satellite is differentiated into an outer h2o layer about 100 km thick but cannot determine the current physical state of this layer liquid or solid here we summarize the geological evidence regarding an extant subsurface ocean concentrating on galileo imaging data we describe and assess nine pertinent lines of geological evidence impact morphologies lenticulae cryovolcanic features pull apart bands chaos ridges surface frosts topography and global tectonics an internal ocean would be a simple and comprehensive explanation for a broad range of observations however we cannot rule out the possibility that all of the surface morphologies could be due to processes in warm soft ice with only localized or partial melting two different models of impact flux imply very different surface ages for europa the model favored here indicates an average age of 50 myr searches for evidence of current geological activity on europa such as plumes or surface changes have yielded negative results to date the current existence of a global subsurface ocean while attractive in explaining the observations remains inconclusive future geophysical measurements are essential to determine conclusively whether or not there is a liquid water ocean within europa today

a lithosequence of soils in extremely gravelly dolomitic parent materials bois blanc island lake huron abstract eight extremely gravelly pedons on bois blanc island were characterized and pathways and processes of genesis were examined the soils are developed in dolomitic gravels and cobbles and contain 1 50 mean 15 fine earth most pedons are in coarse loamy or skeletal particle size families in extremely gravelly parent materials with less than 5 fine earth b horizons have not formed accumulation of organic matter on the surface and between coarse fragments in the upper solum is the main pedogenic process in such soils borofolists in other soils distinct eluvial and illuvial zones are present with organic carbon silts fine sands and caco 3 being the primary constituents undergoing translocation quantity and mineralogical composition of the fine earth appear to alter the pathways of pedogenesis as the amount of fine earth and the percentage of non carbonate materials derived from crystalline rocks increase cambic horizons with spodic morphology may develop

metamorphism in the martian crust compositions of basaltic and ultramafic rocks analyzed by mars rovers and occurring as martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions key minerals identified by remote sensing roughly constrain temperatures and pressures in the martian crust we use a traditional metamorphic approach phase diagrams to assess low grade hydrothermal equilibrium assemblages basaltic rocks should produce chlorite actinolite albite silica accompanied by laumontite pumpellyite prehnite or serpentine talc only prehnite bearing assemblages have been spectrally identified on mars although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates ultramafic rocks are predicted to produce serpentine talc and magnesite all of which have been detected spectrally on mars mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be h2o rich and co2 poor we confirm the hypothesis that low grade hydrothermal metamorphism affected the noachian crust on mars which has been excavated in large craters we estimate the geothermal gradient 20 c km 1 required to produce the observed assemblages this gradient is higher than that estimated from radiogenic heat producing elements in the crust suggesting extra heating by regional hydrothermal activity