experimental investigations on the thermal conductivity characteristics of beishan granitic rocks for china s hlw disposal abstract crystalline rocks are potential host rock types for the construction of high level radioactive waste hlw repositories a better understanding of thermal conductivity of rocks is essential to safe evaluation and engineering optimization of a hlw disposal system in the rock at depth in the present study experimental investigations on the thermal conductivity characteristics of 47 pairs of granitic rock specimens were conducted using the transient plane source tps method the specimens were collected from borehole cores in the beishan area which is being considered as the most potential candidate area for china s hlw repository to evaluate geological nature of the rocks mineralogical compositions of the rocks were identified and porosity of the specimens was measured the thermal conductivities of the specimens under dry and water saturated conditions were determined and the effect of water saturation on the thermal conductivity was investigated in addition the influence of temperature and axial compression stress on the thermal conductivity of dry specimens was studied the results revealed that the thermal conductivity of tested rocks was dependent on water saturation temperature and compression stress based on the obtained data some models considering porosity were established for describing the thermal conductivity characteristics of the tested rocks furthermore when the rocks have a similar porosity the quartz content dominates the thermal conductivity and there exists an obvious increase of the thermal conductivity with increasing quartz content the test results constitute the first systematic measurements on the beishan granitic rocks and can further be used for the development of thermal models for predicting thermal response near the underground excavations for hlw disposal

the evolution of andesite volcano structures new evidence from gravity studies in costa rica abstract published gravity data on active volcanoes generally reflect either the low density scoriaceous pumiceous deposits that are localized within ring fracture collapse depressions such as the calderas of mature silicic volcanoes or the high density frozen magma conduits that occur beneath basaltic shields and cones the intensive gravity surveys reported here over three complex andesite volcanoes reveal features of both types their multi component gravity fields have crater centred positive anomalies 1 2 km diameter surrounded by broader zones of negative gravity with similar amplitudes but greater width 5 10 km the former are thought to reflect sub crater magma pipes of normal density ca 2 5 2 6 mg m 3 surrounded by pyroclastic scoria ashes and occasional lava flows of much lower net density 1 8 2 4 mg m 3 which in turn account for the negative anomalous zones because the deeper more consolidated and older parts of these andesite volcano edifices have more normal densities 2 3 2 6 mg m 3 the low density materials are particularly interesting because they appear to have filled topographic depressions to depths of several hundred metres especially where old caldera like structures have been postulated from the steep gravity gradients over perimeter ring faults a model is developed whereby short periods of caldera collapse associated with intermittent large high level magma bodies are interspersed by normal crater like activity with narrow sub surface magma pipes dominantly pyroclastic activity from summit craters generates the materials that gradually fill earlier formed topographic depressions this study demonstrates the unique value of detailed gravity surveys combined with surface geological information for modelling and understanding the evolution of active volcano summit regions

anomalous transport in heterogeneous media demonstrated by streamline based simulation 1 we use fine grid streamline simulation to demonstrate that anomalous non gaussian transport arises from purely advective movement through heterogeneous systems the simulation model represents a channeled sandstone north sea oil field and contains over one million grid blocks we find the average location and spreading of the plume and the breakthrough curves these features are consistent with anomalous transport described by an exponent that characterizes the long time tail of the transit time distribution depends on the degree of heterogeneity and whether the tracer was injected or originally uniformly distributed across the domain incorporating dispersion to account for sub grid block heterogeneity does not affect the results

calculations on the thermal conditions around a salt diapir temperature modeling around the vejrum salt structure in denmark shows that the heat flow near the top is twice the regional heat flow the temperature in the vicinity of the top of the diapir is thus anomalously high overlying permeable formations could therefore be attractive for geothermal energy exploitation a negative temperature anomaly of 20 c is calculated around the root of the salt body comparisons between calculated and measured temperatures are used to test the model it is shown that measurements of heat flow or temperature gradients in wells penetrating the region of groundwater circulation could be used in identification of salt diapirs

role of continental crust in petrogenesis of orogenic volcanic associations abstract orogenic volcanic rocks form a continuous spectrum between tholeiitic associations of island arcs and calc alkaline associations of continental margins and collision zones although these settings show a wide variation in plate convergence rate depth of scismic zone nature and age of subducted and over riding lithosphere the compositional characteristics of the volcanic association is correlated most strongly with crustal thickness tholeiitic associations dominated by basaltic rocks and with high feott mgo and low k2o for a given sio2 content are restricted to island arcs with crustal thickness less than 20 km more calc alkaline associations dominated by andesitic rocks with lower feot mgo and higher k2o for a given sio2 content occur in areas where crustal thickness exceeds 20 km these suggest that 1 fractional crystallization occurring within the continental crust may be the major mechanism responsible for variations within orogenic volcanic associations and 2 formation of calc alkaline associations may require the presence of continental crust these relationships suggest that calc alkaline magmas may be derived from more tholeiitic magmas by fractional crystallization possibly combined with crustal melting or contamination the extension of these processes might be responsible for formation of silicic ignimbrites occurring in continental areas where the crustal thickness exceeds 30 km in areas of crustal extension

sandstone diagenesis and reservoir quality prediction models myths and reality models and concepts of sandstone diagenesis developed over the past two decades are currently employed with variable success to predict reservoir quality in hydrocarbon exploration not all of these are equally supported by quantitative data observations and rigorous hypothesis testing simple plots of sandstone porosity versus extrinsic parameters such as current subsurface depth or temperature are commonly extrapolated but rarely yield accurate predictions for lithified sandstones calibrated numerical models that simulate compaction and quartz cementation when linked to basin models have proven successful in predicting sandstone porosity and permeability where sufficient analog information regarding sandstone texture composition and quartz surface area is available analysis of global regional and local data sets indicates the following regarding contemporary diagenetic models used to predict reservoir quality 1 the effectiveness of grain coatings on quartz grains e g chlorite microquartz as an inhibitor of quartz cementation is supported by abundant empirical data and recent experimental results 2 vertical effective stress although a fundamental factor in compaction cannot be used alone as an accurate predictor of porosity for lithified sandstones 3 secondary porosity related to dissolution of framework grains and or cements is most commonly volumetrically minor 2 exceptions are rare and not easily predicted with current models 4 the hypothesis and widely held belief that hydrocarbon pore fluids suppress porosity loss due to quartz cementation is not supported by detailed data and does not represent a viable predictive model 5 heat flow perturbations associated with allochthonous salt bodies can result in suppressed thermal exposure thereby slowing the rate of quartz cementation in some subsalt sands

geochemical evidence for the volcanic arc tectonic setting of the dhanjori volcanics singhbhum craton eastern india geochemical data on the dhanjori volcanics of the singhbhum craton indicate that they range from basalt to andesite and show an iron enrichment trend various chemical characteristics suggest that they are differentiated along the trend similar to that of orogenic suites and have a strong affinity with island arc tholeiites the field relationships as well as other geological information also support this conclusion and indicate their eruption on a thin continental margin it is inferred that the dhanjori volcanics were probably erupted as a result of plate convergence in northern singhbhum with subduction of oceanic crust below the singhbhum craton

streamline based simulation of solute transport we propose streamline based simulation as a possible alternative to particle tracking for modeling solute transport like particle tracking the pressure field is computed on an underlying grid using conventional techniques the flow velocity at cell edges is then computed using darcy s law and this information is used to trace streamlines throughout the domain in particle tracking mass is transported by moving particles along streamlines in the method we describe a one dimensional conservation equation is solved numerically along each streamline if the flow field changes the solute concentration is mapped onto the underlying grid and the streamlines are recomputed the concentration is then mapped back onto the new streamlines and the simulation proceeds as before the method is suited for modeling advectively dominated multispecies transport in heterogeneous aquifers we illustrate the streamline approach with synthetic example problems in fully saturated confined aquifers conservative sorbing and decaying tracer a four component radioactive decay chain and saltwater intrusion where the flow field changes with time where possible we compare the results with analytical solutions and results from particle tracking codes

thermal properties and thermal structure in the deep water coalbed basin off the shimokita peninsula japan abstract heat transport properties are significant parameters that affect geothermal processes in deep sedimentary basins we measured the thermal properties of deep sediment core samples to a depth of approximately 2500 m below sea floor mbsf whereas most previous studies have only presented data 1 k 1 and calcite cemented sandstone siltstone exhibits the highest conductivity of approximately 3 wm 1 k 1 the other thermal properties are also influenced by the porosity and lithological contrast the correlation between thermal conductivity and porosity is explained by the mixed law model of the geometric mean the one dimensional temperature depth profile at site c0020 estimated from measured thermal conductivity reveals a regression of the thermal gradient with depth and the surface heat flow of 30 mwm 2 which is consistent with the heat flow data near this site was evaluated the obtained results suggest that the linear geothermal gradient estimated from the average thermal conductivity value at shallow sediment materials could overestimate the temperature at greater depths and underestimate the heat flow

the thermal conductivity for granite with various water contents the thermal conductivities of granite were measured under different conditions of porosity and water content to investigate the effects of the porosity and water content on the thermal conductivity for the dry samples the thermal conductivities range from 2 12 w mk for the rocks with a high porosity to 3 12 w mk for the ones with a low porosity water sorbed samples have greater thermal conductivities than dry samples of the same granite the thermal conductivities range from 2 99 w mk for granites with a high porosity to 3 62 w mk for ones with a low porosity under saturated condition

role of salt in restraining the maturation of subsalt source rocks abstract the presence of salt within a sedimentary basin can potentially modify its temperature distribution and history in particular the positive thermal anomaly associated with the top of salt domes has attracted considerable attention in the past the role of the lesser appreciated negative thermal anomaly associated with the base of salt domes in modifying the maturation history of subsalt source rocks is explored the finite element method was used to model the transient and steady state conductive temperature perturbations induced by salt layers domes and pillows the results indicate that the modification of the thermal regime due to evolving salt domes may significantly affect the maturation level of source rocks in the vicinity of the domes modelling the temperature structure of various salt structures has shown that in general the refraction of heat flow induces a dipole shaped temperature anomaly a positive anomaly located towards the top of the salt structure and a negative anomaly located towards its base these dipole anomalies can be strongly asymmetrical the degree of asymmetry depending on the shape of the salt structure and the proximity of the top of the salt structure to the surface of the basin however when the salt structure reaches the surface the dipole shaped temperature anomaly collapses to a monopole below the salt structure all sediments independent of their depth and lithology are colder relative to a section with no salt similarly salt domes that reach the surface very efficiently drain the heat from below and from the side of the dome these negative thermal anomalies may extend for a considerable depth beneath the base of the salt dome and may reach values of 85 c locally because of the large contrast in thermal conductivity between the highly porous sediments and salt at lower temperatures the efficiency of a salt dome to channel heat increases the closer the salt dome is to the surface these results indicate that deep sedimentary basins containing salt are more prospective than basins without salt and or salt diapirism in addition to the structural traps associated with salt tectonics salt domes and tongues connected to their source dissipate heat more efficiently and thus keep deeper regions of the basin relatively colder and potentially within the oil window for a longer time this cooling effect is maximized when the top of the salt dome remains close to the surface of the sedimentary basin for a significant period of time and may be especially important for continental margins such as brazil and offshore west africa where most of the source rocks lie beneath extensive evaporite deposits in contrast it was found that for the gulf of mexico basin pre and early tertiary salt diapirism and sheet emplacement may have caused significant delays in the maturation of subsalt source rocks in the deeper regions of the gulf basin but the maturation is likely to be relatively insensitive to the late miocene pliocene stage of salt mobilization because the time interval has been too short

thermal conductivity and radiogenic heat production of sedimentary and magmatic rocks in the northeast german basin thermal rock properties were determined for the northeast german basin a subbasin of the southern permian basin in europe the new thermal data provide new aspects for the determination of heat flow and for hydrocarbon and geothermal resource evaluation in the basin thermal conductivity was measured on drill core samples using the optical scanning method values for permian and pre permian clastic rocks are variable 2 3 4 8 w m k because of different depositional environments compaction and cementation reflected in lithology permian carboniferous igneous rocks show lowest thermal conductivity in basalts 2 2 w m k and highest 3 1 w m k in granitoids anisotropy of thermal conductivity in all rocks is low formation thermal conductivity was determined by upscaling the values determined for single lithotypes radiogenic heat production was determined on drill cores for the upper paleozoic sediments and igneous rocks for the younger formations without sample control a well log approach was used the heat production of sedimentary rocks is lowest 0 4 w m3 in the permian zechstein salt and anhydrite and highest 2 1 w m3 in the permian rotliegende clastic rocks heat production of the permian carboniferous rhyolites and granitoids is on the order of 2 6 3 8 w m3 and heat production of andesites and basaltoids is on the order of 0 9 1 9 and 0 1 0 7 w m3 respectively the contribution to surface heat flow by these up to 2 km 1 2 mi thick igneous complexes amounts to 7 mw m2 at a maximum on the same order is the total heat budget provided by the supra permian sedimentary succession in the basin

shallow and deep crustal control on differentiation of calc alkaline and tholeiitic magma article u 230 th isotopes 87 sr 86 sr lower crust assimilation the role of changing crustal interaction and plumbing geometry in modulating calc alkaline vs tholeiitic magma affinity is well illustrated by the influence of 70 km thick crust beneath volcan parinacota changes in petrologic affinity correlate with periods of cone building sector collapse and rebuilding of the volcano over the last 52 ka and are well explained by changes in magma recharge regime with increasing recharge and magma output lavas transition from low fe strongly calc alkaline phenocryst rich silicic compositions to medium fe near tholeiitic mafic and aphanitic characteristics strontium isotope data show that the change in magma regime did not affect all parts of the system simultaneously these are characterized by distinctive 87 sr 86 sr ratios which suggest an initially compartmentalized system relatively high 230 th 232 th activity ratios of 0 72 in early erupted calc alkaline lavas are consistent with interaction with high u upper crust low 230 th 232 th activity ratios of 0 55 and up to 33 th excess in younger near tholeiitic lavas correlate with steep ree patterns indicating lower crustal interaction thorium excesses at the time of eruption approach the maximum that can be generated via small degree garnet residual melting in the lower crust or mantle and imply that transit time through the crustal column for the most tholeiitic magmas had to be short on the order of b2 10 4 yr in contrast lavas with greatest calc alkalinity are also at or near secular

caracterisation du magmatisme proterozoique superieur en afrique de l ouest et implications geodynamiques des rifts intracratoniques au panafricain the main petrological mineralogical and geochemical features of the metavolcanites belonging to the late proterozoic tectono sedimentary units of southern mauritanides termesse and niokolo koba koulountou and western hoggar algeria timesselarsine permit a reconstruction of the geodynamic environment that controlled the evolution of the pan african ranges of western africa flows and pyroclastic beds metamorphosed under greenschist facies conditions are interbedded within detritic and carbonate platform sediments suggesting an unstable environment in the vicinity of a continental margin the association of oceanic tholeiites slightly enriched in lree and basalts more enriched in tio2 zr nb and lree displaying alkalic affinities suggests intracontinental rifting succeeded by expansion the lack of ultrabasic basic complexes oceanic paleosutures in southern mauritanides and their occurrence in the hoggar suggest that the opening was bigger in the north than in the south the later calc alkali

the influence of crustal structure on compositions of subduction related magmas abstract a survey of sr isotopic ratios and other compositional features of subduction related magma suites reveals significant correlations between these averaged parameters and characteristics of the underlying crust i e thickness composition and age these observations lead to the conclusion that crust and or mantle rocks in the hanging walls of subduction zones are involved in modification of primary mafic magmas typically basalt or basaltic andesite it is proposed that mafic magmas will stagnate within the crust or uppermost mantle where they may differentiate and react with wall rocks the extent to which such processes manifest themselves will depend upon details of the local crustal structure in particular the composition and age of the crust will strongly influence such parameters as sr nd and pb isotopic compositions such data strongly indicate the involvement of crustal rocks in locales underlain by old sialic crust e g central andes depending upon the level of magma stagnation and evolution within the crust different trends in isotopic composition may result these isotopic trends may be enhanced by partial melting of the wall rocks to produce relatively silicic anatectic magmas and locally they may reflect subduction of continental sediments interpretation of the isotopic data may be more ambiguous in locales underlain by younger and more mafic continental crust cascades e eleutians and those underlain by oceanic crust owing to the similarity in isotopic composition of primary magmas and the latter crustal materials yet some degree of crustal involvement in magmatic evolution seems highly probable even in these more primitive terranes consequently most island arc magmas and especially those more evolved than basalt are probably not primary in the sense that they do not represent direct melts of the upper mantle studies of arc volcanic rocks may yield misleading conclusions concerning processes of magma generation related to subduction unless evolutionary processes are defined and their effects considered it appears that modern volcanic arcs provide a poor analog for models of early crustal development because the modern mantle derived magmatic components are more mafic in composition than average continental crust

on the role of caprock and fracture zones in dispersing gas plumes in the subsurface 1 waste stored in a geological disposal facility can generate gas and depending on the geological environment this gas may migrate into the rock mass here we develop a simplified physical model to describe the initial stages of the dispersal of a gas plume as it rises from such a geological disposal facility located at a depth of many hundreds of meters below the surface typically the plume becomes confined below a low permeability layer and then spreads laterally until reaching a fault or fracture zone when it may continue rising upward since the gas is soluble in the groundwater the gas may partially dissolve as it displaces the groundwater in addition in the generic geology considered herein since the source of gas gradually wanes with time the spreading plume tends to thin out leading to some residual trapping of the gas behind the plume we show that depending on the distance of the fault or fracture zone from the geological disposal facility different fractions of the source gas may be diverted farther upward into the formation rather than being trapped in the original layer this can have an important impact on the subsequent pattern of dispersal of the gas by the groundwater flows which may be key information in any safety assessment

evolution and geodynamic significance of the tertiary orogenic volcanism in northeastern greece the tertiary volcanism of eastern macedonia and western thrace greece developed in association with the sedimentary basin which formed from eocene to oligocene along the southern margin of the rhodope massif the volcanic products ranging in composition from basaltic andesites to rhyolites show an overall calc alkaline orogenic affinity while chemical characteristics identify different groups of rocks probably reflecting minor differences among parent magmas the observed evolution within any group of rocks is compatible with fractional crystallization processes acting on relatively shallow magma bodies the sr isotopic composition of rhyolitic member shows an initial87sr 86sr ratio comparable with that of basaltic andesites reinforcing the hypothesis of a crystal liquid line of descent geochemical and petrographic evidence on the whole suggests that the investigated orogenic association developed on an active continental margin characterized by a relatively thick crust acting as a density filter for the basic magmas and facilitating their storage and fractionation within the crust itself minor contamination by interaction with host materials may also have occurred stratigraphic and k ar geochronological data indicate that the volcanic activity started in upper eocene and reached its maximum development in upper oligocene from lower miocene the volcanism shifted southward in the central aegean area and in part of western anatolia coming to an end by middle miocene the southward migration of the volcanic front has been interpreted as a consequence of the increase in the dipping of the benioff zone due to the decrease of penetrative strength after the main phase of continental collision

subsurface thermal conductivity assessment in calabria southern italy a regional case study determining the suitability of a local area at a regional or local scale for the geothermal application of low enthalpy systems requires the knowledge of rock thermal conductivity values to evaluate the possibility of low enthalpy heat exchange a digital cartographic tool is also needed to synthesize the thermal properties of the underground this tool should be easily accessible and upgradeable and thus suitable for territorial planning and environmental control in order to address these key issues a methodological approach was developed within the framework of the national vigor project dedicated to evaluating the geothermal potential in southern italy in this paper the region of calabria was selected as a case study around 70 samples that were representative of the main geological formations were collected from all over the area thermal property tests were carried out both in dry and wet conditions using a thermal device in accordance with the modified transient plane source method the thermal conductivity values were then compared with data from the international literature in order to consider the influence of the entire stratigraphic sequence on the thermal conductivity parameters a geostatistical analysis of the available lithostratigraphic data was performed using the matlab toolbox modalstrata specially developed for this purpose a comprehensive geothermal subsurface characterization of calabria was thus obtained

mesozoic and cenozoic volcanic rocks from central and southern tibet 39ar 40ar dating petrological characteristics and geodynamical significance field relations radiometric ages and mineralogical and chemical characteristics of the orogenic volcanic rocks from the lhasa block tibet are studied volcanic activity started before the deposition of the albian aptian sedimentary units takena formation and xigaze group volcanism is volumetrically limited in the northern part of the lhasa block basalts andesites and dacites are present while ignimbrites are scarce radiometric ages of these rocks range between 110 and 80 ma conversely in the southern part of the lhasa block volcanism is largely developed gangdese belt there paroxysmal activity occurred later than in the north between 60 and 50 ma lingzizong formation this volcanism is mainly represented by andesites and ignimbrites a younger episode at about 15 10 ma took place in this southern region the mineralogical and geochemical characteristics indicate that as a whole the volcanic rocks from the lhasa block belong to a calc alkaline continental margin series enriched in k20 and other incompatible elements subordinate potassic alkaline lavas are present in the northern margin of the gangdese belt some basalts exhibit a tholeiitic affinity daquin area southern region the geodynamic significance of these cenozoic volcanic rocks lies in the relative motion of india and the lhasa block after accretion of the latter to the northern qantang block a geodynamic model based on changes of the type of subduction of the indian oceanic crust beneath the lhasa block for the period 120 40 ma is proposed to account for the abundance age and magmatic affinity of the volcanic products

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

the olympus mons aureole formation by gravitational spreading new observations of the aureole deposits of olympus mons are in agreement with previous suggestions that the aureole lobes could have been formed by movement under gravity away from the observed scarps the characteristic corrugated morphology of the aureole is probably secondary formed by erosion along structural inhomogeneities geometries of the corrugations and translational faults in the aureole deposits favor a mechanism of emplacement that involves material with substantial shear strength rather than viscous flow estimates of the aspect ratios of terrestrial landslides nappes and ash flows suggest that the aureole deposits are more similar in overall shape to slide emplaced bodies than to pyroclastic flows although martian physical conditions permit the formation of ash flows there is no positive evidence for their existence a gravitational spreading mechanism is proposed that involves imbricate thrusting in distal regions analogous with terrestrial thrust sheets corrugations in the aureole developed by erosion along imbricate or listric faults basal shear stresses on the decoupling surface may have been of the order of 106 pa 10 bars the nature of the decoupling surfaces in the proximal regions is uncertain but is likely to have been the topographic surface in distal parts the aureole deposits were probably emplaced as a series of sheets by spreading under gravity from an ancestral olympus mons which extended farther to the northwest than does the present volcano as a result of the accumulation of lavas under the then prevailing stress conditions recent lava eruptions from the volcano have been concentrated in northeast and southwest sectors indicating a changed stress regime since aureole emplacement

the geological history of nili patera mars nili patera is a 50 km diameter caldera at the center of the syrtis major planum volcanic province the caldera is unique among martian volcanic terrains in hosting i evidence of both effusive and explosive volcanism ii hydrothermal silica and iii compositional diversity from olivine rich basalts to silica enriched units we have produced a new geological map using three mosaicked 18 m pixel context camera digital elevation models supplemented by compact remote imaging spectrometer for mars hyperspectral data the map contextualizes these discoveries formulating a stratigraphy in which nili patera formed by trapdoor collapse into a volcanotectonic depression the distinctive bright floor of nili patera formed either as part of a felsic pluton exposed during caldera formation or as remnants of welded ignimbrite s associated with caldera formation both scenarios deriving from melting in the noachian highland basement after caldera collapse there were five magmatic episodes 1 a basaltic unit in the caldera s north 2 a silica enriched unit and the associated nili tholus cone 3 an intrusive event forming a 300 m high elliptical dome 4 an extrusive basaltic unit emplaced from small cones in the east and 5 an extreme olivine bearing unit formed on the western caldera ring fault the mapping together with evidence for hydrated materials implies magmatic interaction with subsurface volatiles this in an area of elevated geothermal gradient presents a possible habitable environment sampled by the hydrothermal deposits additionally similarities to other highland volcanoes imply similar mechanisms and thus astrobiological potential within those edifices

streamline based simulation of carbon dioxide storage in a north sea aquifer 1 we model carbon dioxide co2 storage into a deep north sea aquifer using streamline based simulation we assume incompressible flow of liquid like co2 and aqueous phases we simulate dissolution of co2 and a rate limited precipitation reaction advective transport and reactions are solved along streamlines while dispersion and flow due to gravity segregation of the phases are solved on the underlying grid geological storage is modeled on a one million cell model the distribution of co2 after injection is dominated by advective transport due to multiphase flow and co2 moves preferentially through high permeability channels without reaction the regional groundwater flow causes the co2 to continue to migrate until it reaches residual saturation where it continues slowly to dissolve precipitation leads to a decrease in porosity and permeability while co2 is stored in the solid phase the storage efficiency is low around 2 because of aquifer heterogeneity

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

estimation of thermal conductivity from the mineral composition influence of fabric and anisotropy measured values of thermal conductivity from crystalline rocks are compared with values calculated from the mineral content using the layered model first thermal conductivity is estimated using data based on quasi isotropic mixtures of fragments or powder second the approach is applied on core data considering the anisotropy of some rock forming minerals the numerical value of estimated thermal conductivity is controlled by the quartz content sheet silicates control anisotropy and fabric in gneisses and their thermal consequences if imformation about the fabric of the rock is available the anisotropy of minerals can be considered in a layered model and this improves the estimation of thermal conductivity from mineral contents

tectonic cycles in southern africa abstract the recurrence of major geological events within the 3600 ma stratigraphic record of southern africa suggests a periodicity of320 25ma for at least the last 3200 ma this periodicity is reflected in major episodes of continental volcanism granitoid plutonism orogeny reciprocity of terrestrial and marine dominated sequences platform carbonate sedimentation glaciation and first order changes in sea level these serve to define 11 completed megacycles each introduced by a major rifting event accompanied by listric faulting alluvial sedimentation in restricted fault bound troughs volcanism and a type granitoid plutonism prior to 3200 ma continental rift magmatism occurred subaqueously due to very high early archean sea levels resulting in pillow lavas and a lack of interbedded terrigenous siliciclastics the long term reciprocity of terrestrial and marine dominated sequences records eustatic first order changes in sea level with highstands characterized by generally humid warm continental climates low relief and tropical afforestation on the other hand lowstand climates were hot and arid with high relief and widespread desertification thick marine sequences accumulate in areally extensive epeirogenic basins without significant volcanism or faulting and commonly are divided into an early phase of open shelf sedimentation followed by deposition in a brackish marine foreland basin within openshelf environments an early phase of biochemical precipitation and or siliciclastic reworking along linear shorelines is separated from a later phase involving rapid deposition of immature siliciclastics along lobate shorelines evolution of the foreland basin is related to orogenic activity and the isolation of an epeiric sea which sometimes developed the characters of a barred basin marine dominated sequences display a deterministic stacking of lithofacies important glacial epochs commonly occur midway through first order regression sometimes with lesser events closely following peak transgression potentially they display 320 ma periodicity but with an unexplained mid proterozoic gap glaciation is related to the combined effect of climatic cooling associated with first order regression and depletion of atmospheric co2 by biological uptake associated with platform carbonate development terrestrial volcanism is believed to be the main contributor of atmospheric co2 climatic change is accompanied by cyclical patterns of cratonic weathering and pedogenesis

experimental insights on the geometry and kinematics of fold and thrust belts above weak viscous evaporitic decollement abstract this paper discusses the differences in mechanical properties and kinematics between fold and thrust belts detaching on evaporitic decollements and those detaching on stronger detachments physical experiments are described that model shortening of a thick brittle cover overlying a weak viscous decollement to gain a better understanding of these differences we tested the influence of 1 the decollement layer thickness and 2 the presence of a deformable backstop on the hinterland side and of a decollement pinch out on the foreland side because of the very low shear strength of the viscous decollement folds and thrusts did not propagate according to a piggy back sequence but by centripetal back and forth propagation additional shortening was accommodated by growth of all existing structures fold symmetry and thrust vergence varied between experiments models confined between two rigid vertical endwalls always deformed by symmetric folding and thrusting in models having a deformable backstop and a foreland decollement pinch out forethrusting initially dominated folds were asymmetric and fault blocks rotated in models having a thick decollement layer folds kept growing asymmetrically diapirism also depended on the initial decollement geometry diapirs formed only in models having a deformable backstop and were restricted to the hanging wall of a fault related fold finally the implications of such kinematics on the thermal history are discussed as well as the likelihood of hydrocarbon maturation and preservation

mantle heat flow and geotherms for the main geologic domains in morocco thermal and deep seismic soundings data are used to study the dependence between the compressional pn velocity and the surface heat flow or the temperature at the moho discontinuity in morocco this correlation indicates a significant decrease in pn velocity where high heat flow and moho temperature are observed this result is consistent with respect to other regions of the world crustal heat generation models and geotherms are constructed for the major moroccan geological domains extending from the precambrian units in the south to the alpine units in the north the crustal contribution in surface heat flow is on average 35 mwm 2 with high values of 41 42 mwm 2 in the western and eastern meseta where hercynian granite intrusions could enrich the crust in radioactive heat sources high mantle heat flow values are obtained beneath the alboran neogene basin 62 mwm 2 the rif 47 mwm 2 the middle atlas 41 mwm 2 and the south atlantic margin 40 mwm 2 where the crust is thinned by an extensional tectonic regime despite their similar formation context the intra continental belts of the middle and the high atlas show different geothermal field components a lithospheric heating process in the middle atlas could be the result of a plio quaternary basaltic volcanism finally the precambrian basement of the anti atlas like all the west african shield is a stable domain showing the lowest subsurface temperatures

a control volume finite element method for three dimensional multiphase basin modeling abstract in this paper we describe a 3d control volume finite element method to solve numerically the coupled partial differential equations pdes governing geological processes involved in the evolution of sedimentary basins these processes include sediment deposition and deformation hydrocarbon generation multiphase fluid flow and heat transfer in deforming porous media these integrated processes possess a wide range of time scales indicating the need for implicit methods in addition sedimentary basins are geometrically complex environments requiring unstructured tetrahedral meshes to adequately represent the problem realistically without the need for an excessive number of mesh elements here we also present a general formulation for problems involving back oil thermal or compositional models using overall component mass concentrations and an arbitrary lagrangian eulerian ale formulation to deal with salt motion conservatively the newton method is used to solve the sparse jacobian systems resulting from the linearization of the coupled non linear pdes for multiphase flow and energy transfer these systems are solved with the generalized minimal residual method gmres method with an incomplete lower upper ilu preconditioner for faster inner iteration convergence rates we applied this model to a sedimentary basin and we describe the results for this basin

heat flow in the western mediterranean thermal anomalies on the margins the seafloor and the transfer zones the western mediterranean basin has been formed by miocene back arc extension and is underlain by a thin and young lithosphere this young lithosphere is warm as testified by an overall elevated offshore heat flow heat flow within the western mediterranean is however highly variable and existing data are unevenly distributed and poorly studied in the central part of the liguro provencal and algero balearic basins this central part is floored by a young oceanic crust bordered by different continental margins cut by transform faults and filled by up to 8 km of sediments we present a total of 148 new heat flow data collected during the medsalt and westmedflux cruises in 2015 and 2016 and aligned along seven regional profiles that show an important heat flow variability on the basin scale but also locally on the margins a new heat flow map for the western mediterranean outlines the following regional features 1 a higher average heat flow in the algero balearic basin compared to the liguro provencal basin 94 13 mw m2 and 78 16 mw m2 respectively and 2 a regional thermal asymmetry in both basins but with opposed heat flow trends up to 20 of this heat flow difference can be explained by sediment blanketing but age and heterogeneity of ocean crust due to an asymmetric and polyphased opening of the basins are believed to have given the major thermal imprint estimates of the age of the oceanic crust based on the new heat flow suggest a considerably younger west algerian basin 16 23 ma compared to the east algerian basin and the west sardinia oceanic floor 31 37 ma on the margins and ocean continent transitions of the western mediterranean the new heat flow data point out the existence of two types of local anomalies length scale 5 30 km 1 locally increased heat flow up to 153 mw m2 on the gulf of lion margin results from thermal refraction of large salt diapirs and 2 the co existing of both low 110 mw m2 heat flow areas on the south balearic margin suggests a heat redistribution system we suspect the lateral heat advection is resulting from a regional fluid circulation in the sediments associated to the widespread plio pleistocene volcanism on the south balearic margin

buoyancy driven flow from a waning source through a porous leaky aquifer we develop a series of models to describe the migration of a buoyant fluid through a layered permeable rock following release from a localized waning source in particular if the fluid is injected into a high permeability layer bounded above by a layer of lower permeability a plume migrates along the interface with some draining into the low permeability layer if the current is sufficiently deep to overcome the capillary entry pressure we show the motion of the fluid is controlled by a number of key factors with the dominant dimensionless numbers being the time scale for the source to decay compared to the time scale for draining through the low permeability layer the residual saturation of the gas and water in the formation as that phase is displaced by the other phase and the capillary entry pressure as measured by the critical depth of the current required for draining as compared to the initial depth of the current simplified analytical models are presented to illustrate some of the key controls on and transitions in the flow and the models are used to explore leakage and trapping prior to flow reaching a fault zone

anisotropy of elastic moduli p wave velocities and thermal conductivities of asan gneiss boryeong shale and yeoncheon schist in korea abstract this paper presents the anisotropic characteristics of the elastic moduli p wave velocities and thermal conductivities of three types of anisotropic rocks i e asan gneiss boryeong shale and yeoncheon schist occurring in korea the experiments were conducted on rock samples that show clear evidence of transverse isotropy cylindrical core samples with different anisotropy angles were prepared by coring at 15 degree intervals from the transversely isotropic plane using the laboratory directional coring system established for this study elastic moduli p wave velocities and thermal conductivities were determined along the sample axis for different anisotropy angles the anisotropy ratio is defined as the ratio of the properties parallel to the transversely isotropic plane to those perpendicular to the plane and the anisotropy ratios for the thermal conductivities k 90 k 0 of asan gneiss boryeong shale and yeoncheon schist were 1 4 2 1 and 2 5 respectively the p wave velocity anisotropy ratios v p 90 v p 0 for asan gneiss boryeong shale and yeoncheon schist were 1 2 1 5 and 2 3 respectively the elastic moduli p wave velocities and thermal conductivities that were obtained were compared with theoretical predictions by mean prediction error mpe the correlations between the measured properties were evidently correlated with some minor scatter in the data the degree of anisotropy measured in this study suggests that ignoring anisotropy in rock properties may mislead to erroneous results the application of tensorial transformation evaluations revealed that the three types of rocks chosen for this study can be modeled effectively by a transversely isotropic model

a surprising asymmetric paleothermal anomaly around el gordo diapir la popa basin mexico thirty seven mudstone samples were collected from the uppermost lower mudstone member of the potrerillos formation in el gordo minibasin within la popa basin mexico the unit is exposed in a circular pattern at the earth s surface and is intersected by el gordo diapir in the northeast part of the minibasin vitrinite reflectance ro results show that samples along the eastern side of the minibasin i e south of the diapir are mostly thermally immature to low maturity ro ranges from 0 53 to 0 64 vitrinite values along the southern western and northwestern part of the minibasin range between 0 67 and 0 85 values of ro immediately northwest of the diapir are the highest reaching a maximum of 1 44 the results are consistent with two different possibilities 1 that the diapir plunges to the northwest or 2 that a focused high temperature heat flow existed along just the northwest margin of the diapir if the plunging diapir interpretation is correct then the thermally immature area south of the diapir was in a subsalt position and the high maturity area northwest of the diapir was in a suprasalt position prior to tertiary uplift and erosion if a presumed salt source at depth to the northwest of el gordo also fed el papalote diapir which is located just to the north of el gordo diapir then the tabular halokinetic sequences that are found only along the east side of el papalote may be subsalt features however if the diapir is subvertical and the high maturity values northwest of the diapir are caused by prolonged high temperature fluid flow along just the northwestern margin of the diapir then both of these scenarios are in disagreement with previously published numerical models this disagreement arises because the models predict that thermal anomalies will extend outward from a diapir a distance roughly 1 5 times the radius of the diapir but the results reported here show that the anomalous values on one side of the diapir are about two times the radius whereas they are as much as five times the radius on the other side of the diapir the results indicate that strata adjacent to salt margins may experience significantly different heat histories adjacent to different margins of diapirs that result in strikingly different diagenetic histories even at the same depth

combined sr o isotope relationships and petrogenesis of andean volcanics of south america active andesitic type volcanism in the southern andes lat 42 36 s is characterized by low sr and o isotopic compositions which fall in the range 87sr 86sr 0 7036 0 7043 18o 5 2 6 8 in contrast volcanic centres in the central andes lat 24 21 s are significantly enriched in both 87sr and 18o we present the first combined sr and o isotope study of the southern volcanic zone svz in chile crustal thickness 40 km 1 and of the southern part of the central volcanic zone cvz in the borderlands of bolivia chile and argentina crustal thickness 60 70 km 1 only one of 13 volcanic centres studied lascar exhibits a correlated increase in both 87sr and 18o parallel with the basalt andesite rhyolite compositional change indicative of contamination by upper crust through a fractional crystallization assimilation mechanism the other centres of the cvz for which there is an overall sr o correlation document the variable contamination of mantle derived magmas at depth in the lower crust which had been thickened by mesozoic and earlier plutonism

petrology of arc volcanic rocks and their origin by mantle diapirs abstract calc alkalic chemical trends characteristic of arc volcanic rocks mainly result from three mechanisms which act additively 1 fractional crystallization involving separation of titanomagnetite 2 selective concentration of plagioclase phenocrysts and selective depletion of titanomagnetite phenocryst compared with the actually fractionated proportion and 3 mixing of magmas on continuous fractionation trends the association of calc alkalic and tholeiitic trends in a single composite volcano may not represent different fractional crystallization processes or different chemistries of primary magmas but the calc alkalic chemical trend can be considered as a mixing trend resulting from mixing of various magmas on associated tholeiitic chemical trends chemical variations of most arc volcanic rocks including calc alkalic ones can accordingly be essentially accounted for by the low pressure fractional crystallization of phenocrystic phases from primary basaltic magmas crystallization sequences of arc magmas which are strongly dependent on water content in magmas are deduced from the phenocryst assemblages the crystallization sequence changes laterally across arc suggesting increasing water contents in magmas toward the back arc side as is also seen for other incompatible elements such as k and rb systematic differences in the characteristic crystallization sequence are also observed among arcs roughly correlating with the crustal thickness water content in magma like other incompatible elements tends to increase with increasing crustal thickness the variation of incompatible elements including water roughly represents that of the degree of partial melting of the upper mantle which is broadly controlled by the crustal thickness the variation of water content indicates that arc magmas are not saturated with water during differentiation to late differentiates such as dacite or rhyolite this strongly constrains the maximum water contents in primary basaltic magma at most 2 5 wt this value suggests that magma generation beneath arcs is dependent on dry solidus of peridotite diapiric uprise of the hot deeper mantle and associated adiabatic decompression would be necessary for mantle peridotite to attain the temperature as high as dry solidus diapirs that begin to rise from the subduction zone may stop at or near the crust mantle boundary because of the surrounding density change and their degree of partial melting is roughly controlled by their stopped depth assuming their similar temperature across arc variation is also explained by the stopped depth of diapirs but is not controlled by crustal thickness

thermal conductivity anisotropy of metasedimentary and igneous rocks 1 thermal conductivity anisotropy was determined for three sets of metasedimentary and igneous rocks from central utah usa most conductivity measurements were made in transient mode with a half space line source instrument oriented in two orthogonal directions on a flat face cut perpendicular to bedding one orientation of the probe yields thermal conductivity parallel to bedding kpar directly the other orientation of the probe measures a product of conductivities parallel and perpendicular to bedding from which the perpendicular conductivity kperp is calculated some direct measurements of kpar and kperp were made on oriented cylindrical discs using a conventional divided bar device in steady state mode anisotropy is defined as kpar kperp precambrian argillites from big cottonwood canyon have anisotropy values from 0 8 to 2 1 with corresponding conductivity perpendicular to bedding of 2 0 to 6 2 w m 1 k 1 anisotropy values for price canyon sedimentary samples are less than 1 2 with a mean of 1 04 although thermal conductivity perpendicular to bedding for the samples varied from 1 3 to 5 0 w m 1 k 1 the granitic rocks were found to be essentially isotropic with thermal conductivity perpendicular to bedding having a range of 2 2 to 3 2 w m 1 k 1 and a mean of 2 68 w m 1 k 1 the results confirm the observation by deming 1994 that anisotropy is negligible for rocks having kperp greater than 4 0 w m 1 k 1 and generally increases for low conductivity metamorphic and clay rich rocks there is little evidence however for his suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2 5 for low thermal conductivity rocks

absence of silicic volcanism on mars implications for crustal composition and volatile abundance on earth eruptions of silicic magmas with volumes of 1 100 km3 are generally associated with stratovolcanoes or composite cones whereas larger 100 1000 km3 ignimbrite deposits are erupted from resurgent calderas and related structures small volumes of silicic rocks are generated by differentiation within basic magma chambers associated with stratovolcanoes but large silicic deposits are largely confined to areas where the granitic crust is thicker than 25 km as mantle derived magmas rise through the thick granitic crust fractional crystallization and assimilation of hydrous crustal rocks concentrate volatiles and sio2 in the magma yielding explosive silicic eruptions on mars under similar chemical conditions ignimbrite eruptions could take place over a broader range of physical conditions than on earth but no large volume ignimbrite deposits can be identified positively explosive basic to ultrabasic eruptions may be responsible for small cinder conelike features on mars and perhaps for the ancient flank scoured paterae such eruptions may have been driven by near surface water ice magma interactions or volatile rich magmas the paterae represent a unique style of volcanism that stopped 2 b y ago we suggest that the volatiles associated with these features were derived from mantle sources and that the cessation of patera formation may coincide with the termination of the period of maximum planetary degassing volcanism since 2 b y ago has been dominantly effusive except for minor explosive ash events such as those which blanketed part of the summit of hecates tholus we propose that such eruptions were driven by volatiles generated by differentiation of a magma chamber similar to icelandic explosive eruptions the apparent lack of large scale silicic volcanism on mars is circumstantial evidence that mars is deficient in volatiles and lacks a granitic crust

allochthonous salt structure and stratigraphy of the north eastern gulf of mexico ii structure the kinematic evolution of allochthonous salt in the north eastern gulf of mexico proceeds in three stages 1 since its middle jurassic deposition the louann salt was loaded by sediments causing episodic basinward movement of salt ultimately leading to large concentrations of salt masses in a slope environment by the end of the lower cretaceous 2 a regime of starved sedimentation during late cretaceous and early oligocene is responsible for the stabilization of these early salt accumulations 3 with renewed rapid accumulation of sediments during the neogene and pliocene extensive allochthonous salt tongues and sheets formed by gravity spreading within the younger sediments of the slope

evaluation of rock anisotropy using 3d x ray computed tomography abstract the anisotropic nature of fabric and internal structures plays a significant role in fluid flow heat transfer and geomechanical behavior in rock the existence and orientation of anisotropy in various rocks have been evaluated using laboratory experiments and image analyses to characterize anisotropic pore networks micro fractures mineralogy grain fabric and stiffness from micro to macro scales we present an assessment of anisotropy in rock by systematic and planar clustering of three dimensional x ray attenuation values and associated statistical analysis on the basis that x ray ct numbers directly represent the internal density of the mineral fabric in the rock mass variation in voxel values across the slicing plane for a given orientation enables identification of the unique orientation of anisotropy in rock the proposed concept is validated using a 3d virtual structure and is applied to four different rock types the sensitivity of anisotropic features and the image noise effect are further explored to highlight the robustness of the proposed method for evaluating the anisotropy of rock fabrics

sequence and petrogenesis of the jurassic volcanic rocks yeba formation in the gangdese arc southern tibet implications for the neo tethyan subduction abstract the yeba formation volcanic rocks in the gangdese arc recorded important information regarding the early history of the neo tethyan subduction to explore their magmatic evolution and tectonic significance we performed a systematic petrological geochronological and geochemical study on these volcanic rocks our data indicated that the yeba formation documents a transition from andesite dominated volcanism which started before 182 ma and continued until 176 ma to bimodal volcanism 174 168 ma in the earliest middle jurassic the early stage andesite dominated volcanics are characterized by various features of major and trace elements and are interpreted as the products of interactions between mantle derived arc magmas and lower crustal melts their positive end t and ehf t values suggest a significant contribution of asthenosphere like mantle the late stage bimodal volcanism is dominated by felsic rocks with subordinate basalts geochemical signatures of the basalts indicate a composite magma source that included a subduction component an asthenosphere like upper mantle domain and an ancient subcontinental lithospheric mantle component the felsic rocks of the late stage were produced mainly by the melting of juvenile crust with some ancient crustal materials also involved we suggest that the occurrence and preservation of the yeba formation volcanic rocks were tied to a tectonic switch from contraction to extension in the gangdese arc which probably resulted from slab rollback of the subducting neo tethyan oceanic slab during the jurassic

geochemistry and tectonomagmatic affinities of the metavolcanic rocks of the early proterozoic tampere schist belt southern finland abstract the c 1 9 ga old tampere schist belt is part of the svecofennian province of finland and sweden which was formed by extensive mantle derived crustal growth during the early proterozoic the volcanic rocks of the belt range widely in chemical composition part of the variation is due to alteration and reworking but the main control are primary compositional characteristics the rocks range from almost low k tholeiitic units to shoshonitic and trachytic units intermediate rocks of calc alkaline affinities being most common by and large the volcanic rocks resemble those of present day volcanic arcs calc alkaline intermediate rocks dominate and the contents of tio2 in mafic rocks are often low some units are exceptional by exhibiting non arc affinities they are fairly high in ti and may thus mark extensional tectonic events the percentage of andesites dacites rhyolites or percent adr mostly exceeds 50 which suggests that the crust was more than 20 km thick during the eruption of most of the studied rocks the tampere schist belt thus resembles mature island arcs or volcanic arcs at or close to active continental margins rather than immature intra oceanic island arcs archaean crust is absent and it can be inferred that the crust was segregated from the mantle during the proterozoic the svecofennian province as a whole appears to differ from present day convergent plate margins by the rapidity of its crustal evolution

radiogenic heat production of crustal rocks an assessment based on geochemical data a survey of the geochemical literature and unpublished data has resulted in the classification of u th and k concentrations by rock type over 2500 data entries have been compiled permitting calculation of their radiogenic heat production in the igneous rocks mean heat production ranges from highs of 12 20 heat production units hpu wm 3 in some peralkaline intrusives through 4 hpu in acidic 2 in intermediate and 1 in basic rocks to a low of 0 3 hpu in ultramafic rocks siliceous clastic rocks generally have greater heat production 2 to 4 hpu than do chemical sedimentary rocks including the carbonates 0 4 to 2 hpu the heat production of metamorphic rocks generally depends on the radioelement contents of their igneous and sedimentary predecessors modified by metamorphic processes based on estimates of the proportion of the continental crust that specific rock types occupy the weighted mean radiogenic heat production of the upper continental crust estimated from this data base is 3 hpu

the thermal regime of the northeastern german basin from 2 d inversion abstract the thermal regime and the distribution of heat flow at the base of sedimentary basins is fundamental to the understanding of the process of basin evolution and the associated mobilization and migration of hydrocarbon and other fluids for the northeastern german sedimentary basin available information on structure temperature and thermal properties along a seismic dekorp reflection profile allow high resolution 2 d forward and inverse simulations this approach is attractive in situations where much information is available if only with considerable uncertainty in particular this allows to introduce soft information into the analysis in our case forward simulations yield initial a priori estimates of the parameters while inversion calculations yield a posteriori estimates of the parameters and their uncertainty the a priori parameters as well as their assumed uncertainty are input for a bayesian parameter estimation scheme in respect to the northeastern german sedimentary basin the inverse analysis postulates a significant and characteristic a posteriori variation of thermal conductivity of the zechstein unit along the entire profile as well as a generally large a posteriori thermal conductivity of the pre permian basement in the northern part of the basin for inverse calculations we used two alternative scenarios one assumes the thermal conductivity of the zechstein unit to be homogeneous along the profile while the other allows a lateral variation a posteriori heat flow across the base of the model varies from 40 to 60 and 50 to 65 mw m 2 for models in which values for thermal conductivity and radiogenic heat generation rate were either based on literature values or direct measurements respectively

streamline based dual porosity simulation of reactive transport and flow in fractured reservoirs 1 we present a streamline based formulation to model two processes transport of a tracer undergoing rate limited sorption and two phase water oil or air water transport in fractured systems using a dual porosity approach we show that these two processes can be simulated using mathematically equivalent formulations in both cases the system conceptually has two components a flowing fraction connected to stagnant regions with transfer between the two domains streamlines capture movement through the flowing fraction fluid transfer between flowing and stagnant regions enters as a source sink term in the one dimensional transport equations along a streamline to model flow and transport in fractured systems we develop a new formulation for the transfer function that matches experimental imbibition data then we illustrate the streamline approach with synthetic reservoir problems we use a finely gridded over one million grid blocks three dimensional domain with a highly heterogeneous permeability field to study both fracture flow and tracer transport we find breakthrough curves that are consistent with anomalous transport described by an exponent that characterizes the longtime tail of the transit time distribution for fracture flow we demonstrate that the speed of fluid advance in the fractures is controlled by the imbibition rate the run times for the simulations scale approximately linearly with system size making the method appropriate for the simulation of large numerical models

thermophysical properties of the po basin rocks summary we present an analysis on thermal properties density and porosity of clastic chemical biochemical and intrasedimentary volcanic rocks collected from petroleum exploration wells of the po basin northern italy moreover we investigate the applicability of the hashin shtrikman s model for a mineral aggregate in combination with the zimmerman s model that takes pore shape into account to calculate the bulk thermal conductivity in case of macroscopically isotropic rocks deviations between predicted and measured values range from 2 2 per cent to 6 9 per cent and significantly decrease if a proper pore aspect ratio is chosen regarding the volumetric heat capacity approximate estimates were obtained by means of a weighted average of the volumetric heat capacity of the mineral grains and that of the pore filling water the differences between the computed and measured values range from 6 2 per cent to 4 9 per cent and on average the computed volumetric heat capacity is lower by 1 6 per cent the water loss during compaction and the temperature increase with depth are main factors controlling thermal properties an anisotropy effect occurs in the case of rocks rich in sheet silicates due to rotation of these minerals the vertical thermal conductivity of sheet silicates decreases exponentially with burial depth from 2 13 w m 1 k 1 at the surface to 0 52 w m 1 k 1 at 4 5 km the laboratory data allow the formulation of compaction curves

andean analogue for late carboniferous volcanic arc and arc flank environments of the western new england orogen new south wales australia abstract late carboniferous continental conglomerates interbedded with silicic ignimbrite sheets outcrop along more than 400 km of the western margin of the southern portion of the new england orogen farther east the coeval sedimentary facies are volcanogenic shallow marine and turbidite deposits the volcanic source terrain no longer exposed was located to the west of the existing conglomerate ignimbrite sequences and was underlain by continental crust which is in part represented by the northern lachlan fold belt the regional late carboniferous palaeogeography was similar to that of the present day western continental margin of south america the geology of the oceanward flank of the andean arc in northern chile and a section of the late carboniferous continental sequence near currabubula are comparable in detail the andean stratovolcanoes and ignimbrite centres thus provide the means of reconstruction of the late carboniferous volcanic source terrain the geological record of both of these continental margin volcanic arcs preserved in deposits of the arc flanks is shaped by volcanism especially the eruption of voluminous ignimbrites and by uplift deformation and glaciation centered on the arc for the arc sections considered diversity in the flank sequences arises because these controls vary in importance spatially and during the life of the arc 20 30 ma for the entire andean arc arc parallel variations in the sites of active volcanism and its character appear to be related to differences in the continental crust thickness and the circumstances of subduction of oceanic crust particularly the dip of the benioff zone by analogy variation in the age duration and style of volcanic activity along the late palaeozoic magmatic arc of the western new england orogen perhaps reflects the former existence of significant differences in crust thickness and in the angle of subduction

controlled co2 injection into heterogeneous geologic formations for improved solubility and residual trapping 1 geologic co2 storage gcs has been proposed as a potentially viable climate change mitigation option among the trapping mechanisms known for permanent co2 storage in saline aquifers solubility and residual trapping are important for safe short term entrapment these storage mechanisms are hampered by density driven upward co2 movement that inhibits the lateral migration of the plume leaving a large portion of the aquifer volume unexposed to co2 and unavailable for storage heterogeneity of aquifer hydraulic properties and high horizontal vertical hydraulic conductivity ratio of geologic formations are two competing mechanisms that can hinder upward co2 migration postinjection displacement of free phase co2 is somewhat controlled by the heterogeneity in rock permeability and porosity distributions in particular low permeability shale layers that act as vertical flow barrier and high permeability horizontal channels that form flow conduits can spread the co2 plume laterally in the aquifer in this paper we consider co2 storage in heterogeneous saline aquifers and propose controlled co2 injection based on existing knowledge of heterogeneity to increase co2 contact with brine and improve the solubility and residual trapping and the overall aquifer storage potential we examine two optimization methods directly maximizing the total stored gas in the aquifer and maximizing the sweep efficiency of the co2 flood to promote uniform displacement in all directions we consider the effect of geologic uncertainty on the performance of the controlled injection schemes by using an ensemble of model realizations to represent the uncertainty in aquifer property distribution we also show how a controlled injection can be used to mitigate the risk of leakage from potential pathways such as an abandoned well by restricting co2 movement toward the leakage zone our results suggest that controlled injection can lead to substantial improvements in residual and dissolution trapping and can be used to divert a co2 plume from approaching sensitive zones or leakage pathways

the effect of drainage on the capillary retention of co2 in a layered permeable rock buoyant plumes of co 2 spreading through water saturated permeable rock bounded by layers of lower permeability tend to spread laterally as they advance they may gradually leak through fractures or discontinuities in the lower permeability boundary leading to a gradual waning of the original plume and dispersal of co 2 higher in the formation with a finite release of co 2 the trailing edge of the plume recedes with time and capillary forces tend to trap a fraction of this co 2 within the pore space this also leads to a gradual waning of the plume with time and limits the mass of co 2 which can leak through the boundary and rise higher into the formation we explore the balance between these two effects and calculate some of the controls on the fraction of the co 2 plume which becomes trapped within the original layer of rock

major controlling factors on hydrocarbon generation and leakage in south atlantic conjugate margins a comparative study of colorado orange campos and lower congo basins abstract we present a supra regional comparative study of the major internal and external factors controlling source rock sr maturation and hydrocarbon hc generation and leakage in two pairs of conjugate margins across the south atlantic the brazil campos basin angola lower congo basin margins located in the central segment and the argentina colorado basin south africa orange basin in the southern segment our approach is based on the analysis and integration of borehole data 1d numerical modeling 2d seismic reflection data and published reports coupling of modeling results sedimentation rate calculation and seal bypass system analysis reveal that 1 oil window is reached by syn rift srs in the southern segment during the early to late cretaceous when thermal subsidence is still active while in the central segment they reach it in late cretaceous neogene during a salt remobilization phase and 2 early hc generation from post rift srs in the southern segment and from all srs in the central segment appears to be controlled mainly by episodes of increased sedimentation rates the latter seems to be associated with the andes uplift history for the western south atlantic basins campos and colorado and to a possibly climate driven response for the eastern south atlantic basins orange and lower congo additionally we observe that the effect of volcanism on sr maturation in the southern segment is very local the comparison of cretaceous mass transport deposit mtd episodes with hc peak of generation and paleo leakage indicators in the southern segment revealed the possible causal effect that hc generation and leakage have over mtd development interestingly paleogene leakage indicators which were identified in the argentina south africa conjugate margins occur contemporaneously to low sedimentation rate periods nonetheless present day leakage indicators which were also identified in both pairs of conjugate margins might be related to seal failure events linked to eustatic sea level drops

numerical modelling of the thermal evolution of the northwestern dniepr donets basin ukraine abstract the dniepr donets basin ddb is a late devonian rift structure located within the east european craton numerical heat flow models for 13 wells calibrated with new maturity data were used to evaluate temporal and lateral heat flow variations in the northwestern part of the basin the numerical models suggest that heat flow was relatively high during late carboniferous and or permian times the relatively high heat flow is probably related to an early permian re activation of tectonic activity reconstructed early permian heat flow values along the axial zone of the rift are about 60 mw m2 and increase to 90 mw m2 along the northern basin margin these values are higher than those expected from tectonic models considering a single late devonian rifting phase the calibration data are not sensitive to variations in the devonian carboniferous heat flow therefore the models do not allow deciding whether heat flows remained high after the devonian rifting or whether the reconstructed permian heat flows represent a separate heating event analysis of the vitrinite reflectance data suggest that the northeastern dniepr donets basin is characterised by a low mesozoic heat flow 30 35 mw m2 whereas the present day heat flow is about 45 mw m2

the influence of salt domes on paleotemperature distributions a characteristic of salt domes is that an enhanced heat flux is associated with them due to the contrast in thermal conductivity between rock salt and typical sedimentary formations we present a simple analytical model of heat flow in the vicinity of an isolated salt dome with numerical evaluations for some sample cases in addition to an enhanced surface heat flow these models show that on the upper flanks of a salt dome a temperature higher than the regional trend is predicted thus enhancing hydrocarbon maturation at these depths on the lower flanks a temperature lower than the regional trend is predicted thus inhibiting overmaturation the magnitude of this temperature anomaly depends upon the position of the measurement point both vertical and radial relative to the salt dome roughly speaking it is confined to within one salt dome radius of the salt sediment interface the magnitude of the anomaly can be quite large for typical salt domes these basic ideas are corroborated by observing downhole measurements from a salt dome in the gulf of mexico the good agreement allows us to bracket the height of that particular dome at between 9 000 and 15 000 m and also permits us to determine that the total sediment thickness overlying the basal salt is between 13 200 and 19 200 m at the location of the salt dome these results indicate that the presence of a salt dome can have a significant impact on the subsurface temperature distribution and hence on the thermochemical maturation of any source rocks or hydrocarbon accumulations in close proximity to the salt dome in addition to providing trapping structures a salt dome also provides an enhanced environment for hydrocarbon maturation on its upper flanks and for inhibiting overmaturation on its lower flanks such effects should be included when evaluating the hydrocarbon potential of a salt dome province

geologic modeling and fluid flow simulation of acid gas disposal in western wyoming the moxa arch anticline is a regional scale northwest trending uplift in western wyoming where geologic storage of acid gas carbon dioxide methane nitrogen hydrogen sulfide ethane is under consideration nugget sandstone a deep saline aquifer at depths exceeding 17 000 ft 5180 m is a candidate formation this study builds three dimensional local to regional scale geologic and fluid flow models for the nugget sandstone and its neighboring formations geologic and engineering characterization data were assembled and screened for accuracy using geostatistical simulations first sequential indicator simulation of facies then the sequential gaussian simulation of porosity the data were integrated to create a regional scale geologic model from which a local scale simulation model surrounding the proposed injection si te was extracted using this model acid gas injection was simulated for 50 yr followed by 1950 yr of monitoring a sensitivity analysis was conducted exploring the impact of geologic and engineering variables on model predictions results suggest that at the simulation time scale low dissolved solids in formation water large gas phase relative permeability krg hysteresis and low vertical to horizontal intrinsic permeability k anisotropy all contribute to enhanced storage of acid gas in both residual trapped and dissolved forms the parameter that exerts the largest control on gas storage is relative permeability hysteresis however given parameter uncertainty the total predicted gas storage varies significantly prediction uncertainty increases in the order of dissolved gas trapped gas and mobile gas in comparison petrophysical uncertainty as represented by multiple realizations has limited impact on prediction although future work is needed to expand the uncertainty analysis by developing alternative facies models for the storage formations

on the lateral variations in chemical composition and volume of quaternary volcanic rocks across japanese arcs the fe mg fe ratios xfe of the quaternary basalts sio2 53 wt in the japanese arcs were examined the xxfe of relatively magnesian basalts decreases from the volcanic front toward the japan sea across the arcs based on the partition coefficient of mg fe2 between olivine and liquid it is suggested that all the basalts near the volcanic front which are mostly tholeiitic basalts are significantly fractionated whereas many basalts near the japan sea which are mostly alkali basalts are little fractionated the k2 o content in the primary basalt magmas increases toward the japan sea combining the xfe and k2 o data it is suggested that relatively large amounts of tholeiitic magmas are produced near the volcanic front but they fractionate during their ascent whereas smaller amounts of alkali basalt magmas are formed near the japan sea but they can ascend with less fractionation the density of primary tholeiite magma is significantly larger than that of primary alkali basalt magmas it is most likely that primary tholeiite magmas cannot ascend beyond the upper crust and would fractionate to produce less dense tholeiitic magmas near the volcanic front whereas primary alkali basalt magmas can ascend through the upper crust without fractionation as far as buoyancy is the principal ascending force in the japanese arcs the stress field may be less compressional near the japan sea than near the volcanic front so that magmas can ascend more rapidly in the latter region than in the former these two factors may be responsible for the above mentioned chemical variations of basalt magmas across the arcs the variation in volume of the quaternary volcanic rocks across the arcs can be explained by the presence of a melt rich zone above but nearly parallel to the subducted slab

on the flow of buoyant fluid injected into a confined inclined aquifer we study the dispersal of a plume of incompressible buoyant fluid injected into a confined sloping aquifer which has an outflow at a single fault which may be up dip up slope or down dip down slope from the point of injection we develop a long time asymptotic solution for the motion of the injected fluid we show that for the case in which the outflow fault is up dip from the point of injection there is a critical injection rate above which the injected fluid floods the full depth of the aquifer and we show that for the case in which the outflow fault is down dip from the point of injection there is a critical injection rate below which all injected fluid initially flows up dip our analysis leads to expressions for the lateral extent of the injected fluid as a function of time and we consider the implications of the model for the dispersal of supercritical carbon dioxide injected into deep saline aquifers the work also indicates that the geometry of the system may have a significant effect on i the total volume of carbon dioxide which it is possible to sequester in a faulted aquifer and ii the interpretation of the dispersed position of any injected tracers

thermal conductivity from core and well log data abstract the relationships between thermal conductivity and other petrophysical properties have been analysed for a borehole drilled in a tertiary flysch sequence we establish equations that permit us to predict rock thermal conductivity from logging data a regression analysis of thermal conductivity bulk density and sonic velocity yields thermal conductivity with an average accuracy of better than 0 2 w m k 1 as a second step logging data are used to compute a lithological depth profile which in turn is used to calculate a thermal conductivity profile from a comparison of the conductivity depth profile and the laboratory data it can be concluded that thermal conductivity can be computed with an accuracy of less than 0 3 w m k 1 from conventional wireline data the comparison of two different models shows that this approach can be practical even if old and incomplete logging data are used the results can be used to infer thermal conductivity for boreholes without appropriate core data that are drilled in a similar geological setting

copper enrichment in arc magmas controlled by overriding plate thickness the characteristics of magmas typically associated with porphyry copper deposits are thought to be imparted in the mantle statistical assessment of over 40 000 geochemical analyses of magmatic rocks formed in subduction zones worldwide however shows that the characteristics of these magmatic rocks are systematically controlled by the thickness of the arc crust

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

thermal evolution and maturation of lower paleozoic source rocks in the tarim basin northwest china the tarim basin is one of the richest basins in oil and gas resources in china the cambrian and middle upper ordovician strata are the most important source rocks previous early paleozoic thermal histories have led to varied hypotheses on the evolution of the lower paleozoic source rocks causing a significant impact on petroleum exploration in the basin a new paleozoic thermal history of the tarim basin was reconstructed in this article using the integrated thermal indicators of apatite and zircon uranium thorium helium ages apatite fission tracks and equivalent vitrinite reflectance data the modeled results indicate that different parts of the basin experienced widely differing early paleozoic thermal gradient evolution the eastern and central regions of the basin experienced a decreasing thermal gradient evolution from 37 to 39c km during the cambrian and ordovician to 35 to 36c km in the silurian whereas the northwestern region of the basin had an increasing early paleozoic thermal gradient evolution from 28 to 32c km in the cambrian to 30 to 34c km in the ordovician and silurian the lower cambrian thermal gradient resulted from the higher thermal conductivity of the 800 to 1000 m 2625 to 3280 ft thickness of gypsum and salt in the cambrian strata the basin experienced an intracratonic phase during the late paleozoic and a foreland basin phase during the mesozoic and cenozoic with the thermal gradient decreasing to the present day value of 20 to 25c km the sensitivity of thermal modeling by the best fit method is less than 5 in our study and the differences of the early paleozoic thermal gradient evolution in different regions of the basin may result in differential maturation of lower paleozoic source rocks the maturity histories of the source rocks modeled based on the new thermal histories indicate that the lower paleozoic source rocks in most areas of the basin matured rapidly and reached the late mature to dry gas stage during the paleozoic but experienced slower maturation during the mesozoic and cenozoic these new data on the paleozoic thermal history and lower paleozoic source rock maturity histories of the tarim basin provide new insights to guide oil and gas exploration of the basin

the origin of lavas and ignimbrites of the taupo volcanic zone new zealand in the light of oxygen isotope data abstract the taupo volcanic zone consists predominantly of andesites at each end and about a 20times larger volume of rhyolites incl ignimbrites and pumice in the center in a 18o vs sio2 diagram the rhyolites do not continue the increasingly 18o contaminated andesite basalt to dacite trend but have lower 18o values than the most differentiated andesites comparison with 18o of greywackes and conjectural granitoids seems to rule out a partial fusion origin in retrospect the sr isotope data of ewart and stipp 1968 are seen to confirm this conclusion isotopic adjustment of source rocks before partial fusion by exchange with circulating subsurface waters is highly unlikely because of the combined demands for o and sr isotope shifts and the constraint offered by the normal igneous to somewhat enriched 18o values of the rhyolites oxygen isotope results confirm separate origins or at least different modes of ascent of basalt and andesites on one hand and rhyolites on the other both magma types appear to have originated below crustal formations and both have become contaminated by greywacke through which they passed to reach the surface

a diagenetic rock physics approach for siliciclastics this study presents a new heuristic approach that includes temperature in rock physics modelling temperature is the most important factor for chemical compaction and hence velocity evolution in the chemical compaction domain given brine saturated rocks the modelling is dependent on only three input parameters lithology vsh porosity and temperature the simplicity of the approach and the ability to model all stages of diagenesis in sands and shales make this strategy suitable in early exploration settings where little information is available due to fundamental differences in sands and shales one sand model and one shale model are proposed both temperature dependent the models are calibrated to local sands and shales and then used to predict scenarios not observed in the data set it is further demonstrated how the models can be used to guide seismic interpretation when interpreting shale sand reflections at different diagenetic stages finally the suggested models are also used to predict

outflow ignimbrite sheets from late carboniferous calderas currabubula formation new south wales australia regionally mappable silicic outflow ignimbrite sheets are interbedded with fluvial volcanogenic conglomerates and sandstones of the late carboniferous currabubula formation of north eastern n s w four of the most widespread of these ignimbrites are described and defined as members the oldest member is comprised of many thin originally non welded flow units interbedded accretionary lapilli horizons may indicate phreatomagmatic activity at vent during the eruption in addition to local rain flushing of co ignimbrite ash clouds of the three other members two are multiple flow unit sheets 160 180 m in aggregate thickness substantial portions of these sheets were originally welded the remaining member is a simple welded ignimbrite characterized by abundant spherulites and lithophysae irregular pre eruption topography and contemporaneous erosion were responsible for thickness variations of the ignimbrite sheets some palaeovalleys now delineated by the ignimbrites persisted in spite of repeated pyroclastic influxes relic pumice shards and crystal fragments are ubiquitous components of the sedimentary facies of the currabubula formation and were probably derived from originally poorly consolidated pyroclastic deposits such as airfall ash layers and non welded ignimbrites no surface trace of the sources of these ignimbrites exists however internal facies thickness variations and volumes of the ignimbrites indicate that they periodically emanated from a multiple caldera terrain which was continuously active during the late carboniferous and located several kilometres to the west of present exposures

a study of conceptual model uncertainty in large scale co2 storage simulation 1 in this study multiscale permeability upscaling is combined with a sensitivity study of model boundary condition to identify an optimal heterogeneity resolution in developing a reservoir model to represent a deep saline aquifer in co2 storage simulation a three dimensional fully heterogeneous reservoir model is built for a deep saline aquifer in western wyoming where each grid cell is identified by multiple material tags on the basis of these tags permeability upscaling is conducted to create three increasingly simpler site models a facies model a layered model and a formation model accuracy of upscaling is evaluated first before co2 simulation is conducted in all models since at the injection site uncertainty exists in the nature of the reservoir compartment end member boundary conditions are evaluated whereby brine production is introduced to control formation fluid pressure the effect of conceptual model uncertainty on model prediction is then assessed for each boundary condition results suggest that for the spatial and temporal scales considered without brine production optimal complexity of the upscaled model depends on the prediction metric of interest the facies model is the most accurate for capturing plume shape fluid pressure and co2 mass profiles while the formation model is adequate for pressure prediction the layered model is not accurate for predicting most of the performance metrics moreover boundary condition impacts fluid pressure and the amount of co2 that can be injected for the boundary conditions tested brine production can modulate fluid pressure affect the direction of mobile gas flow and influence the accuracy of the upscaled models in particular the importance of detailed geologic resolution is weakened when viscous force is strengthened in relation to gravity force when brine production is active variability of the predictions by the upscaled models becomes smaller and the predictions are more accurate suggesting a subtle but important interplay between heterogeneity resolution fluid driving forces and model predictions

subduction of young oceanic lithosphere and extensional orogeny in southwestern north america during mid tertiary time an extensional orogeny deformed the basin and range province probably beginning in the late eocene about 40 3 ma its characteristics include partial melting of the continental lithosphere during the ignimbrite flareup massive ductile extension including detachment faulting and rise of metamorphic core complexes the affected zone became about 1200 km wide possibly double its original width it rose an average of 1 2 km despite crustal thinning locally some of the highest mountains of north america up to 4 3 km high rose through resurgence of ignimbrite cauldrons and isostatic uplift of underlying plutons the climax of extension occurred prior to the development of the present basin and range topography modeling of major and trace elements and sr and pb isotopes strongly suggests that mid tertiary volcanic magmas equilibrated and probably originated in the continental lithosphere components attributable to subducted oceanic lithosphere have not yet been identified the rocks seem to belong to two provinces separated by the quartz diorite boundary line of moore 1959 which also marks the western limit of north america at the end of the late paleozoic sonoman orogeny to the west low k rocks rest on a basement of predominantly oceanic accreted terranes to the east high k rocks rest on an autochthonous sialic basement within the high k province potassium variations can be correlated with crustal thickness there is no need to invoke a k h relationship conventional models of plate convergence and back arc extension which involve subduction of old rigid cool and dense oceanic lithosphere may not apply to the mid tertiary basin and range province the overridden farallon plate is more likely to have been young hot ductile buoyant and no denser than continental asthenosphere having been generated in a spreading center close to north america under these conditions motion of the subducting plate slows and slab pull is likely to approach zero even prior to ridge trench collision overridden oceanic lithosphere may have become underplated beneath the continental lithosphere and ruptured by rising mantle diapirs subducted oceanic lithosphere no longer acted as a heat sink which could partly account for the great width of the affected zone and the anomalous thermal gradients required for partial melting extension and metamorphism had these processes not died down after ridge trench collision the western segment of the cordillera might have separated from north america to form a japanlike archipelago while the basin and range province foundered into an analog to the sea of japan instead of rupturing completely the basin and range province fractured into fault blocks

the deep thermal field of the glueckstadt graben with this paper we assess the present day conductive thermal field of the glueckstadt graben in nw germany that is characterized by large salt walls and diapirs structuring the graben fill we use a finite element method to calculate the 3d steady state conductive thermal field based on a lithosphere scale 3d structural model that resolves the first order structural characteristics of the graben and its underlying lithosphere model predictions are validated against measured temperatures in six deep wells our investigations show that the interaction of thickness distributions and thermal rock properties of the different geological layers is of major importance for the distribution of temperatures in the deep subsurface of the glueckstadt graben however the local temperatures may result from the superposed effects of different controlling factors especially the upper sedimentary part of the model exhibits huge lateral temperature variations which correlate spatially with the shape of the thermally highly conductive permian salt layer variations in thickness and geometry of the salt cause two major effects which provoke considerable lateral temperature variations for a given depth 1 the chimney effect causes more efficient heat transport within salt diapirs as a consequence positive thermal anomalies develop in the upper part and above salt structures where the latter are covered by much less conductive sediments in contrast negative thermal anomalies are noticeable underneath salt structures 2 the thermal blanketing effect is caused by thermally low conductive sediments that provoke the local storage of heat where these insulating sediments are present the latter effect leads to both local and regional thermal anomalies locally this translates to higher temperatures where salt margin synclines are filled with thick insulating clastic sediments for the regional anomalies the cumulative insulating effects of the entire sediment fill results in a long wavelength variation of temperatures in response to heat refraction effects caused by the contrast between insulating sediments and highly conductive crystalline crust finally the longest wavelength of temperature variations is caused by the depth position of the isothermal lithosphere asthenosphere boundary defining the regional variations of the overall geothermal gradient we find that a conductive thermal model predicts observed temperatures reasonably well for five of the six available wells whereas the steady state conductive approach appears not to be valid for the sixth well

influence of small scale fluvial architecture on co 2 trapping processes in deep brine reservoirs a number of important candidate co2 reservoirs exhibit sedimentary architecture reflecting fluvial deposition recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to co2 injection and storage we used a geocellular modeling approach to represent this multiscaled and hierarchical sedimentary architecture with this model we investigated the dynamics of co2 plumes during and after injection in such reservoirs the physical mechanism of co2 trapping by capillary trapping incorporates a number of related processes i e residual trapping trapping due to hysteresis of the relative permeability and trapping due to hysteresis of the capillary pressure additionally co2 may be trapped due to differences in capillary entry pressure for different textural sedimentary facies e g coarser grained versus finer grained cross sets the amount of co2 trapped by these processes depends upon a complex system of nonlinear and hysteretic characteristic relationships including how relative permeability and capillary pressure vary with brine and co2 saturation the results strongly suggest that representing small scale features decimeter to meter including their organization within a hierarchy of larger scale features and representing their differences in characteristic relationships can all be critical to understanding trapping processes in some important candidate co2 reservoirs

thermal properties of sedimentary rocks in the tarim basin northwestern china thermal properties of rocks are essential parameters for investigating the geothermal regime of sedimentary basins and they are also important factors in assessments of hydrocarbon and geothermal energy resources the tarim basin the largest basin located in the north of the tibetan plateau northwestern china has great hydrocarbon resource potential and is an ongoing target for industry exploration however the thermal properties of sedimentary rocks within the basin are yet to be systematically investigated at a basin scale thereby limiting our understanding of the thermal regime in the basin here we collected 101 samples of sedimentary rocks and measured their thermal properties our results show that the ranges and means of thermal conductivity radiogenic heat production and specific heat capacity are 1 08 5 35 w mk 2 52 0 99 w mk 0 03 3 24 w m3 1 24 0 87 w m3 and 0 75 1 10 kj kg c 0 87 0 07 kj kg c respectively volumetric heat capacity and thermal diffusivity at the temperature of 40 c range from 1 61 to 2 79 mj m3 k 2 26 0 25 mj m3 k and 0 44 2 95 10 6 m2 s 1 12 0 53 10 6 m2 s respectively the thermal properties vary considerably for different lithologies even within the same lithotype indicating that thermal properties alone cannot be used to distinguish lithology thermal conductivity increases with increased burial depth density and stratigraphic age suggesting the dominant influence is porosity variation on thermal conductivity furthermore a strong contrast in the thermal properties of rock salt and other sedimentary rocks perturbs the geothermal pattern which should be taken into consideration when performing basin modeling

characterization of the sedimentary thermal regime along the corsair growth fault zone texas continental shelf using corrected bottomhole temperatures temperatures of deep 3 km 1 8 mi sediments along the corsair growth fault zone in the texas continental shelf are elevated relative to those off the fault zone this observation is based on a compilation of nearly 400 bottomhole temperatures bhts obtained from about 230 wells widely distributed across the continental shelf the bhts have been individually corrected for the thermal disturbance associated with drill fluid circulation the isotherm of 140 c 284 f derived from the corrected bhts shows more or less continuous peaks along the fault zone thermal gradients in the depth range of 3 to 5 km 1 8 to 3 1 mi shows higher values along the fault zone than off the fault zone these trends are similar to the previous observations made along the wilcox growth fault zone in the texas coastal plain previous studies suggest that the faults of the wilcox system serve as the conduits for hot fluids expelled from deep overpressured sediments a similar mechanism may explain the elevated temperatures along the corsair fault zone

andean andesites and crustal growth over the last 200 ma the ensialic andean plate margin has been characterized by calc alkaline magmatism the early mesozoic activity was dominantly of basaltic volcanism while the cainozoic volcanism was of intermediate calc alkaline character the restriction of recent volcanism to parts of the andes underlain by thick wedges of asthenospheric mantle and the sr and nd isotopic relations indicate that the calc alkaline parental magmas are derived from the asthenospheric mantle there is no unequivocal geochemical and geophysical evidence that continental crust or sediment has contributed to the mantle source for andean magmatism the chemical compositions of the calc alkaline volcanic rocks of the active volcanic zones are controlled by fractional crystallization whereas o sr isotopic relations reflect crustal interaction of mantle derived parental magma with the sialic basement of the andes the variable extent of fractional crystallization partial melting and mixing of crustal contaminant are related to the variable thickness and age of crust in the different volcanic provinces calc alkaline magmatism was largely responsible for post mesozoic crustal growth in the andes and would have depleted the underlying mantle unless balanced by circulation within the asthenospheric mantle wedge in terms of net growth of the south american continent it is not certain where the balance lies between growth by magmatic addition and shrinking by erosion

the origin of pyrenean hercynian volcanic rocks france spain ree and smnd isotope constraints reply abstract the hercynian orogeny of the pyrenees generated a suite of basalt to rhyolite calc alkaline volcanic rocks that were erupted subaerially these melts may either have been generated above a subduction zone or by lower crustal melting after input of mantle derived magmas in an extensional environment sm nd garnet whole rock mineral isochrons date a rhyolitic ignimbrite from the coll de oli ignimbrite member at 313 14 ma 2 mswd 0 7 and a rhyolitic lava of the coll de pi region at 320 2 ma 2 mswd 0 2 these ages suggest that some of the volcanism was synchronous with high temperature low pressure metamorphism and partial melting deep in the hercynian crust as seen in rocks now exposed in the axial and northern pyrenean zones and dated by u pb on zircon at between 309 5 and 315 5 ma the silicic volcanic rocks are peraluminous and have highly fractionated ree patterns with low abundances of the hree and la yb n 70 mineral and whole rock ree abundances suggest derivation of the silicic rocks by partial melting of a metasedimentary source in equilibrium with garnet and or garnet fractionation in melts derived from peraluminous sources nd isotope compositions of the entire volcanic rock suite mafic silicic compositions are within the same range as those of sediments metamorphosed during the hercynian orogeny and hercynian basement rocks they have mid proterozoic depleted mantle model sm nd ages and do not exhibit mixing trends with mantle sources even the most mafic of the volcanic rocks appear to have interacted extensively with the crust analysis of the chemistry of the volcanic rocks does not unequivocally constrain the hercynian tectonic setting of the pyrenees

metallogeny and tectonic development of the tasman fold belt system in new south wales abstract the northwestern corner of new south wales consists of the paratectonic late proterozoic to early cambrian adelaide fold belt and older rocks which represent basement inliers in this fold belt the rest of the state is built by the composite late proterozoic to triassic tasman fold belt system or tasmanides in new south wales the tasman fold belt system includes three fold belts 1 the late proterozoic to early palaeozoic kanmantoo fold belt 2 the early to middle palaeozoic lachlan fold belt and 3 the early palaeozoic to triassic new england fold belt the late palaeozoic to triassic sydney bowen basin represents the foredeep of the new england fold belt the tasmanides developed in an active plate margin setting through the interaction of east gondwanaland with the ur precambrian and palaeo pacific plates the tasmanides are characterized by a polyphase terrane accretion history during the late proterozoic to triassic the tasmanides experienced three major episodes of terrane dispersal late proterozoic cambrian silurian devonian and late carboniferous permian and six terrane accretionary events cambrian ordovician late ordovician early silurian middle devonian carboniferous middle late permian and triassic the individual fold belts resulted from one or more accretionary events the kanmantoo fold belt has a very restricted range of mineralization and is characterized by stratabound copper deposits whereas the lachlan and new england fold belts have a great variety of metallogenic environments associated with both accretionary and dispersive tectonic episodes the earliest deposits in the lachlan fold belt are stratabound cu and mn deposits of cambro ordovician age in the ordovician cu deposits were formed in a volcanic are in the silurian porphyry cu au deposits were formed during the late stages of development of the same volcanic are post accretionary porphyry cu au deposits were emplaced in the early devonian on the sites of the accreted volcanic arc in the middle to late silurian and early devonian a large number of base metal deposits originated as a result of rifting and felsic volcanism in the silurian and early devonian numerous sn w mo and base metal au granitoid related deposits were formed a younger group of mo w and sn deposits resulted from early middle carboniferous granitic plutonism in the eastern part of the lachlan fold belt in the middle devonian epithermal au was associated with rifting and bimodal volcanism in the extreme eastern part of the lachlan fold belt in the new england fold belt pre accretionary deposits comprise stratabound cu and mn deposits pre early devonian stratabound cu and mn and exhalite au deposits late devonian to early carboniferous and stratabound cu exhalite au and quartz magnetite late carboniferous s type magmatism in the late carboniferous early permian was responsible for vein sn and possibly au as ag sb deposits volcanogenic base metals when compared with the lachlan fold belt are only poorly represented and were formed in the early permian the metallogenesis of the new england fold belt is dominated by granitoid related mineralization of middle permian to triassic age including sn w mo w and au ag as sb deposits also in the middle permian epithermal au ag mineralization was developed during the above period of post orogenic magmatism sizeable metahydrothermal sb au w and au deposits were emplaced in major fracture and shear zones in central and eastern new england the occurrence of antimony provides an additional distinguishing factor between the new england and lachlan fold belts in the new england fold belt antimony deposits are abundant whereas they are rare in the lachlan fold belt this may suggest fundamental crustal differences

geothermal characteristics of the vorotilovo deep borehole drilled into the puchezh katunk impact structure abstract the vorotilovo borehole 5374 m in depth was drilled in 1989 1992 in the central part of the large puchezh katunk impact structure which is located in the east european platform lat 57 1 n long 43 6 e the geothermal studies of the borehole section were based on the temperature logging of the entire borehole 1992 1995 on the thermal conductivity measurements for more than 3700 air dry and fluid saturated core samples under normal p t conditions and for 473 samples at a temperature up to 100 c the rock anisotropy was taken into account in these measurements significant local vertical variations 20 30 even within short depth intervals of 100 200 m and a regular increase of conductivity from 0 8 1 2 w m 1 k 1 to 2 5 3 0 w m 1 k 1 with depth were established it was shown that conductivity variations are closely related to the grade of shock thermal metamorphism the thermal conductivity of metamorphic rocks from the basement of the vorotilovo uplift appeared to be substantially lower up to 40 than the conductivity of similar archaean rocks from ukrainian and baltic shields which we have investigated previously after the drilling had been completed the thermal regime of the rock massif was restored significantly faster than was inferred from previous theoretical considerations by september 1995 it was generally stabilized substantial vertical variations were recorded for all geothermal characteristics the section can be subdivided into three segments with distinct heat flow densities the interval down to 1200 m with the least heat flow density 22 31 mw m 2 i e 50 60 of the highest value the 1200 1900 m interval 34 42 mw m 2 i e 75 85 of the highest value and the 1900 5300 m interval with the highest density 40 56 mw m 2 appreciable local variations of the heat flow density obviously are caused by the refraction of heat flow at structural elements of the massif the character of mutual change of geothermal parameters in certain intervals testifies to the non steady thermal regime and fluid filtration the value of terrestrial heat flow density for the drilling site was estimated as 52 58 mw m 2 calculations show that in the depth range of 400 2000 m the effect of palaeoclimate causes a reduction of heat flow density of approximately 25 this cannot exhaustively account of the recorded vertical variation of heat flow density and allows us to suppose an effect of mass transfer or non steady thermal regime in the upper part of the section

the quartz diorites of limousin elemental and isotopic evidence for devono carboniferous subduction in the hercynian belt of the french massif central a chain of late devonian early carboniferous intrusions on the western margin of the french massif central the limousin tonalite belt consists of quartz diorites which are unusual among french hercynian granitoids in their low silica contents 53 68 wt sio2 and abundant hornblende they represent the earliest and most primitive plutonism post dating the main phase of hercynian metamorphism and have chemical characteristics strongly resembling andesitic lavas of calc alkaline affinity they differ from other massif central hercynian granitoids in their low 87sr86sr360 0 7047 0 7059 and high nd360 0 7 to 1 8 their initial pb composition was rather homogeneous 206pb204pb360 18 15 18 38 207pb204pb360 15 57 15 62 208pb204pb360 38 06 38 26 and their 207pb204pbi values are significantly lower than those of other hercynian granitoids the limousin quartz diorites are considered to have originated from an enriched mantle with characteristics modified by subduction of oceanic crust and terrigenous sediments the primitive quartz dioritic magmas were then contaminated in the lower continental crust by an afc process involving acid metaigneous or metasedimentary lithologies the occurrence of such plutons in the earliest phase of hercynian plutonism in the massif central is probably related to minor subduction at an active continental margin

estimation of the thermal conductivity anisotropy of rock with application to the determination of terrestrial heat flow a moderately large data set of mostly sedimentary and metamorphic rocks compiled from the literature shows an inverse correlation between thermal conductivity anisotropy and thermal conductivity perpendicular to bedding the empirical relationship can be represented by a simple two component end member mixing model one end member is anisotropic x z 2 5 and has a relatively low thermal conductivity perpendicular to bedding z 1 w m k the other end member is isotropic and has a relatively high thermal conductivity perpendicular to bedding 4 w m k the proposed model may be used to derive a correction for anisotropic effects observed during thermal conductivity measurements on mixtures of randomly oriented aggregates although the accuracy and reliability of a universal correction procedure remain to be determined the proposed correction scheme should enhance our ability to estimate accurately heat flow in sedimentary basins where generally only borehole cuttings are available for thermal conductivity measurements

thermal and maturation history of jurassic source rocks in the kuqa foreland depression of tarim basin nw china abstract kuqa foreland depression of the tarim basin is one of the largest gas production provinces in china thermal history reconstruction using vitrinite reflectance data indicates that the palaeo heat flow in kuqa depression was relatively high 50 55 mw m 2 during the mesozoic but gradually decreased during the cenozoic to reach the present value of 40 50 mw m 2 the cooling of the kuqa depression is probably attributed to the crust thickening and the rapid sedimentary rate the jurassic source rocks entered conventional oil window at 100 ma and began to generate gas at approximately 75 ma in the kelasu area thermal maturation of the jurassic source rocks accelerated significantly since 23 3 ma especially in the recent 5 2 ma in this foreland depression source rock maturation which is likely controlled mainly by burial history also influenced by the presence of fault thrusting and salt bearing formations