microbially induced cementation to control sand response to undrained shear current methods to improve the engineering properties of sands are diverse with respect to methodology treatment uniformity cost environmental impact site accessibility requirements etc all of these methods have benefits and drawbacks and there continues to be a need to explore new possibilities of soil improvement particularly as suitable land for development becomes more scarce this paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose collapsible sand microbially induced calcite precipitation micp was achieved using the microorganism bacillus pasteurii an aerobic bacterium pervasive in natural soil deposits the microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix the results of both micp and

yield strength and critical state behavior of a tropical saturated soil the paper reports laboratory investigations carried out on a tropical soil profile to study its compressibility strength critical state and limit state conditions and their variation with depth the soil profile comprises a reddish lateritic layer horizon b underlain by a saprolitic soil horizon c from which a number of block samples were taken a series of isotropic and anisotropic compression tests and drained and undrained triaxial tests were conducted on specimens sampled at depths between 1 0 and 7 0 m and also in the exposed saprolitic soil special triaxial tests with the pore pressure increased to induce failure were performed to investigate the failure at low stress levels on this basis a tensile cutoff on the failure envelope was defined in order to assess the influence of the natural soil structure drained and undrained triaxial tests were carried out on compacted samples obtained from depths of 1 0 and 5 0 m higher strength parameters were measured for the horizon c soil which

cemented sands under static loading cemented sands are found in many areas of the world one of their distinguishing characteristics is their ability to stand in steep natural slopes large deposits are located along the california coast and in a number of areas intense urban development has occurred near the crest of high steep slopes because of the hazards posed by slope failures in the cemented sands a test program was undertaken to define the nature of the cementation and its effect on behavior of the soils a total of 137 laboratory compression and tension load tests were performed on undisturbed samples of naturally cemented sands and artificially prepared cemented sands the materials exhibited friction angles similar to uncemented sands but had a cementation strength intercept and a tensile strength the primary cementing agents of the sands tested were silicates and iron oxides the strength of the cemented sands were found to be a function of density amount of cementing agent grain shape and grain arrangement

monitoring and volumetric estimation of injected co2 using 4d seismic petrophysical data core measurements and well logging a case study at ketzin germany more than 50 000 tons of co2 have been injected at ketzin into the stuttgart formation a saline aquifer at approximately 620 m depth as of summer 2011 we present here results from the 1 st repeat 3d seismic survey that was performed at the site in autumn 2009 after about 22 000 tons of co2 had been injected we show here that rather complex time lapse signatures of this co2 can be clearly observed within a radius of about 300 m from the injection well the highly irregular amplitude response within this radius is attributed to the heterogeneity of the injection reservoir time delays to a reflection below the injection level are also observed petrophysical measurements on core samples and geophysical logging of co2 saturation levels allow an estimate of the total amount of co2 visible in the seismic data to be made these estimates are somewhat lower than the actual amount of co2 injected at the time of the survey and they are dependent upon the choice of a number of parameters in spite of some uncertainty the close agreement between the amount injected and the amount observed is encouraging for quantitative monitoring of a co2 storage site using seismic methods

geology geochemistry and 40ar 39ar ages of the cerro millo epithermal high sulfidation gold prospect southern peru abstract the high sulfidation system of cerro millo is hosted in a late miocene andesitic paleo stratovolcano in the high andes of southern peru very pronounced advanced argillic alunite silicic and argillic kaolinite and smectite alteration characterizes the central part of the hydrothermal system propylitic alteration is developed in a 3 to 4 km wide outer halo abundant alunite occurs as hypogene acicular crystals and very fine grained aggregates the latter formed during near surface steam heated overprinting hypogene alunite has an ar ar plateau age of 10 8 0 9 ma 2 and is synchronous with the andesitic volcanism ar ar on biotite 11 0 0 5 ma a second ill defined alunite age plateau of 8 0 0 9 ma is probably related to steam heated overprint and points to major erosion in between both hydrothermal events telescoping is also evident by a series of silicified horizons which mark the paleo groundwater table these units have elevated mercury antimony and arsenic levels late phase barite occurs in some structurally controlled advanced argillic altered envelopes the hypogene alteration mineralogy points to temperatures at 250 c hydraulic fracturing and steam heated overprinting suggest a shallow boiling environment slight gold enrichment is observed in the lowermost exposed parts of the system

mapping brittle fracture zones in three dimensions high resolution traveltime seismic tomography in a granitic pluton summary fractured and altered zones within a granitic pluton are mapped in three dimensions by means of high resolution seismic traveltime tomography the input traveltimes were picked from offset and azimuth variable vertical seismic profiles ovsp acquired in three boreholes and from seismic shot gathers of four cdp high resolution seismic reflection profiles recorded on the surface for the ovsp data a hydrophone streamer placed in the boreholes recorded the acoustic energy generated a signal with a frequency content between 15 to 150 hz by a vibroseis truck at source points distributed every 30 m in a rectangular grid of 620 m by 150 m the combination of borehole and surface seismic data resulted in an increase in the ray density of the shallow subsurface the tomographic algorithm uses a variable model grid with a finer grid spacing close to the surface were ray density is highest and the velocity variations are strongest therefore the resulting velocity models feature more detail at shallow levels a simple and smooth starting velocity model was derived from p wave velocity logs careful surface geological mapping and borehole geophysical data p and s wave velocity logs and poisson s ratio depth functions provided key constraints for a physically reasonable 3 d interpretation of the tomograms the low velocity anomalies constrained by the tomographic images were interpreted as unconsolidated rock fractures and altered zones which correlate with structures mapped at the surface or velocity anomalies identified in the logs subsequent resolution analysis revealed that the derived velocity model is well constrained to depths of 60 m

mesozoic rifting in the basque cantabrian basin spain inherited faults transversal structures and stress perturbation terra nova 24 70 76 2012 abstract in the basque cantabrian basin northern iberian margin inherited wnw ese striking faults were reactivated during the mesozoic extensional stage associated with the opening of the bay of biscay syn rift structures in the area include different sets apparently indicating multiple extensional stages in particular abundant ne sw striking extensional elements have been interpreted in the past as having developed during a late rifting left lateral transtensional stage however the development of these structures also fits well with an analytical model of ridge perpendicular extension along strike stretching imposed by displacement variations along inherited faults locally produced an additional stress field oriented obliquely to the regional one this caused rotation of the local minimum stress and development of anomalously oriented transversal structures a single extensional stage is thus inferred during mesozoic rifting with a stretching direction oriented approximately perpendicular to the trend of the bay of biscay oceanic ridge

relationships between chemical weathering indices and physical and mechanical properties of decomposed granite abstract chemical weathering is one of the dominant mechanisms for weathering of granite in subtropical and tropical regions resulting in modifications of its chemical physical and mechanical properties thus the changes in chemical properties may provide insight about the changes in physical and mechanical properties of weathered granite in this paper three quantitative chemical weathering indices are correlated to the dry density of decomposed granite a linear relationship is found between each chemical weathering index and dry density for granitic saprolites mobiles index i mob gives the highest coefficient of correlation among the three chemical weathering indices further investigations were conducted to establish the relationships between i mob and other physical and mechanical properties of granitic saprolites the test results showed that fines content increases with increasing i mob but peak strength increases with decreasing i mob the peak states of granitic saprolites are consistent with rowe s stress dilatancy relationship dilatancy increases with decreasing i mob that contributes to a higher peak strength based on some test results presented in this study it seems that i mob could be a good indicator to quantify the effects of chemical weathering on physical and mechanical properties of granitic saprolites

variations in sub tropical deep weathering profiles over the kowloon granite hong kong variations in the physical characteristics of the weathering profile over the kowloon granite in hong kong have been established using borehole records supported by field mapping there is a strong correlation between topography of the weathered profile base and the main structural trends linear zones of deep weathering have been preferentially eroded to create valleys which subsequently became sites of alluvial and colluvial accumulation variations in weathering patterns are primarily a function of the geometry and infilling of relict jointing which together determine local hydrogeology and hence intensity of weathering magnetic susceptibility is a reliable indicator of material weathering grade in the kowloon granite corestones are generally restricted to weathered profiles over topographically high areas the locations of which are controlled by regional joint spacing and orientation corestone bearing profiles are rare and more commonly deeply weathered granite without corestones passes abruptly into relatively fresh rock this has important implications for engineering ground models derived from borehole interpretation

the characterization of arsenic in mine waste arsenic is dispersed widely in nature and is the 47th most abundant element among the 88 known natural elements the average crustal abundance is 1 5 ppm with higher concentrations in reduced shales and coals it is concentrated in many metal bearing mineral deposits being a chalcophile element it occurs in many metallic deposits including those of cu ag au zn hg u sn pb mo w ni co and pge arsenic is often more dispersed than ore minerals in those deposits and as such is a useful indicator in geochemical exploration boyle and jonasson 1973 hale 1981 cohen and bowell 2014 consequently elevated concentrations of as are common in mine waste and process waste from metal bearing ores bowell et al 1994 2013 thornton 1994 craw and pacheco 2002 lazareva et al 2002 in particular as is the main element of environmental concern in most hardrock mines in this chapter we outline the principal occurrences of as at mine sites and their environmental significance as an example of the detailed controls on as geochemistry in mine waste we focus on the gold mines in new zealand many mines are significant point sources for as in the environment and some mine sites have high concentrations of as locally often exceeding 1 in ore or waste for almost all of these mines the as is a natural but undesirable component of the ore and therefore the as is discarded with the rest of the mine wastes hence mine wastes especially mine tailings are major repositories of as and have to be managed carefully view this table table 1 major primary mineral hosts for as in mine waste arsenic is an especially common constituent of sulfide bearing mineral deposits where as typically occurs either as separate as minerals table 1 or in solid solution

influence of reconstitution method on the behaviour of completely decomposed granite reconstituting soil is common in construction yet the method used can affect the mechanical behaviour of the reconstituted soil when the soil contains a significant amount of fines a completely decomposed granite was reconstituted following different methods namely dry deposition moist tamping slurrying and reconstituting after separating fines by washing then it was tested in compression and shearing the test results highlight the sensitivity of the soil behaviour to the method of preparation used for reconstitution it was found that preparation methods involving large amounts of water such as slurrying s or reconstitution after washing the fines f can lead to a release of fines with effect to change the grading and change the mineralogy differences between dry deposited d moist tamped mt specimens and slurried s washed reconstituted f specimens were observed mainly in the volumetric response two different normal compression and critical state lines were obtained for the two main

geotechnical characterization of macau marine deposits abstract samples of marine deposits retrieved at an onshore old reclamation site on the north coast of taipa macau were studied samples located from 6 m to 17 m below the existing ground were retrieved from three boreholes where field vane shear tests were performed close to one of them the soil is very soft and the results reveal that the deposits are normally consolidated in addition to common geotechnical classification tests x ray diffraction and scanning electron microscope analyses were carried out oedometer tests k 0 compression and undrained triaxial shear tests were performed on intact as well as laboratory remolded specimens the deposits resemble typical soft clay behavior in terms of compressibility and permeability however the soils exhibit a surprisingly high k 0 value which is believed to be caused by the presence of salts during the sedimentation process critical state of the soil is presented and two unique critical state lines in the e ln p space are found for the deposits at different depths

plate reconstruction of the bay of biscay a plate reconstruction of the bay of biscay to a predrift stage is proposed on the basis of 1 an aptian albian tectonic pattern of the basque cantabrian region in northern spain which suggests major left lateral strike slip movements and 2 a continental margin that matches predrift stages plate reconstruction results from the juxtaposition of the two continental margins of the bay of biscay so that the eastern north spanish margin lies laterally adjacent to the southwest french margin landes plateau and the western north spanish margin borders the eastern part of the meriadzek terrace in the armorican margin the restoration obtained is supported by both the implied amount of clockwise rotation of iberia 37 very close to the 35 suggested by paleomagnetism and the positive matching of north south oriented transform structures from the south biscay margin with northeast southwest oriented transform structures from the north biscay margin

modeling of dilative shear failure medium to dense sand sheared under undrained or essentially undrained conditions shows a dilative hardening response when the stress crosses a phase transformation state and gets into the dilative zone when the stress finally reaches a failure surface the deviatoric stress as well as the mean normal stress may continuously develop along the surface accompanied by an excessive but finite deviatoric strain this behavior is termed as dilative shear failure in this text properly modeling this behavior has its significance in predicting the large deformations of many geotechnical structures at or near failure this includes quantitative predictions of postliquefaction ground deformations during and after earthquakes this paper points out that dilative shear failure is no more than a combination of neutral loading and perfect plasticity however under which the stress strain relationship is still well defined this paper presents a general framework in modeling this failure mode identifies dilatancy as

geochemistry of late metamorphic hydrothermal alteration and graphitisation of host rock macraes gold mine otago schist new zealand abstract the macraes gold deposit in the otago schist new zealand formed during late metamorphic fluid flow through a lower greenschist facies shear zone mineralisation occurred near to the brittle ductile transition at about 300 c large volumes of host rock in a shear zone up to 120 m thick have been hydrothermally altered by this fluid activity most alteration is not structurally controlled apart from proximity to the shear zone ductile and brittle microshears traverse the most mineralised rocks and some structural control of fluid flow occurred as well fluid flow was slow similar to that in metamorphic rocks mm year and diffusion through interconnected fluid was a significant chemical process localised extensional hydrofractures m scale are filled with mineralised quartz most alteration of the host rocks was isochemical with respect to the lithophile elements and mineralised rocks have been variably enriched in as au sb w mo and bi but not co or cd addition of sulphur has occurred to both host rocks and mineralised rocks up to 1 wt above a background of 0 1 wt host rock sulphur is mainly pyritic and is not structurally controlled mineralised rocks have pyrite and arsenopyrite along microshears pyrite chalcopyrite sphalerite and galena have formed from sulphidation of silicates with no addition of metals graphite has been added to mineralised rocks along microshears up to 3 wt locally above a background of 0 1 wt noncarbonate carbon graphite deposition may have occurred as a result of mixing of two fluids water methane and water carbon dioxide graphitisation and sulphidation reactions released low d water which accumulated in the slow moving mineralising fluid distinction between this low d reaction water and meteoric water incursion is difficult

the pierina epithermal au ag deposit ancash peru paragenetic relationships alunite textures and stable isotope geochemistry the pierina high sulfidation epithermal au ag deposit 9 26 5 s 77 35 w was emplaced in the middle miocene into a hypabyssal to extrusive pumice tuff and an underlying older dacitic flow dome complex both of which are cut by hydrothermal breccias and small dacitic domes stage i advanced argillic alteration generated a core of vuggy silica focused in the tuff and surrounded successively by zones of quartz alunite dickite kaolinite pyrophyllite and illite montmorillonite kaolinite laser ablation icp ms analysis of the sulfide minerals of the succeeding stage ii cu pb bi sb zn as barite mineralization largely confined to the vuggy silica zone reveals that both au and ag were introduced at that time this assemblage was almost entirely obliterated during stage iii when oxidation by low temperature meteoric waters generated botryoidal hematite goethite assemblages which are now the main precious metal hosts stage iv barite acanthite mineralization shows limited temporal overlap with stage iii but dominantly overprints the hematite goethite assemblage the deposit incorporates alunite exhibiting a wide range of modes of occurrence grain size and morphology disseminated alunite dominates stage i alteration which replaced phenocrysts and fragments and locally hosts corroded 40 m alumino phosphate sulfate aps inclusions the alunite shows limited na substitution molar na na k 0 2 but alunite natroalunite assemblages occur sporadically throughout the quartz alunite alteration zone isotopic analysis yields 34s values of 16 6 31 0 consistent with a magmatic hydrothermal origin rare occurrences of disseminated alunite and pyrite in textural equilibrium occur in unoxidized areas of the deposit and yield 34salu py precipitation temperatures of 179 to 250 c with the majority below 200 c disseminated alunite in shallower oxidized portions of the deposit where pyrite has been destroyed yield 18oso4 values of 6 3 to 14 4 the lighter compositions occur along the axis of the quartz alunite alteration zone and imply precipitation at higher temperatures albeit with some meteoric water involvement porcelaneous alunite 10 100 m forms the matrix of breccias that cut stage i alteration sodium contents are low na na k molar 0 1 and aps inclusions have not been identified the 34s values of 21 8 27 1 are consistent with a magmatic hydrothermal origin but the 18oso4 values of 11 4 to 14 6 indicate deposition under cooler temperatures and the involvement of meteoric water that interacted substantially with igneous country rocks coarse open space filling alunite which occurs as veins or coatings on breccia fragments exhibits limited na substitution is not associated with natroalunite and does not host aps inclusions its 34s and 18oso4 values of 12 9 to 26 2 and 6 5 to 8 6 respectively imply a magmatic hydrothermal origin and deposition at higher temperatures dike like bodies and mantos of friable alunite have distinctive 34s 16 2 19 3 and 18oso4 7 6 9 2 values and may record a steam heated environment however these compositions may also indicate loss of h2s gas during oxidation or overprinting of steam heated alunite by magmatic hydrothermal alunite or vice versa all forms of alunite exhibit higher 18oso4 values in the central part of the deposit and the coherent isotopic chemistry casts doubt on the reliability of the widely accepted textural criteria for the origin of this mineral in hydrothermal systems

depositional architecture and transgressive regressive cycles within liassic backstepping carbonate ramps in the basque cantabrian basin northern spain an integrated stratigraphical sedimentological geochemical and sequential analysis has been carried out on the liassic rocks of the basque cantabrian basin in northern spain using outcrop and subsurface data the study documents the progressive drowning and backstepping of an epeiric carbonate ramp that originated during the worldwide late triassic early jurassic transgression two major carbonate depositional systems have been recognized within the drowning succession 1 a late triassic early sinemurian shallow marine ramp which reflects a progressive marine transgression over triassic continental deposits 2 a late sinemurian toarcian set of hemipelagic ramps which recorded the progressive drowning and backstepping of the ramp system during a second major event of marine flooding sequence stratigraphic analysis of the liassic succession has revealed that transgressive regressive trends constitute the most evident cyclicity a major transgressive regressive cycle and six subsidiary transgressive regressive facies cycles have been defined in the basin and compared with those defined in other european basins although a good correlation exists for the major transgressive regressive cycle significant discrepancies have been found for the number limits and extent of the transgressive regressive facies cycles reflecting the effects of local tectonics the overall backstepping within the basque cantabrian basin resulted in a dominance of transgressive episodes across a range of different scales accordingly regressive intervals are less well developed except during limited periods of active tectonics as occurred in the mid sinemurian these progressively longer and deeper marine flooding intervals followed by relative stillstand or minor sea level falls are interpreted to reflect high thermal subsidence rates coupled with a liassic eustatic transgression

characterisation and multifaceted anisotropy assessment of corvio sandstone for geological co2 storage studies we present a comprehensive characterisation of the physical mineralogical geomechanical geophysical and hydrodynamic properties of corvio sandstone this information together with a detailed assessment of anisotropy is needed to establish corvio sandstone as a useful laboratory rock testing standard for well constrained studies of thermo hydro mechanical chemical coupled phenomena associated with co2 storage practices and for geological reservoir studies in general more than 200 core plugs of corvio sandstone 38 1 and 50 mm diameters 2 1 length to diameter ratio were used in this characterisation study with a rock porosity of 21 7 1 2 dry density 2036 32 kg m 3 and unconfined compressive and tensile strengths of 41 3 28 and 2 3 0 14 mpa respectively geomechanical tests show that the rock behaves elastically between 10 and 18 mpa under unconfined conditions with associated young s modulus and poisson s ratio of 11 8 2 8 gpa and 0 34 0 01 gpa respectively permeability abruptly decreases with confining pressure up to 10 mpa and then stabilises at 1 md ultrasonic p and s wave velocities vary from about 2 8 3 8 km s 1 and 1 5 2 4 km s 1 respectively over confining and differential pressures between 0 1 and 35 mpa allowing derivation of associated dynamic elastic moduli anisotropy was investigated using oriented core plugs for electrical resistivity elastic wave velocity and attenuation permeability and tracer injection tests corvio sandstone shows weak transverse isotropy symmetry axis normal to bedding of 10 for velocity and 20 for attenuation

a land controlled source electromagnetic experiment using a deep vertical electric dipole experimental settings processing and first data interpretation a multichannel borehole to surface controlled source electromagnetic experiment was carried out at the onshore co2 storage site of hontom in spain the electromagnetic source consisted of a vertical electric dipole located 1 5 km deep and the electric field was measured at the surface the subsurface response has been obtained by calculating the transfer function between the transmitted signal and the electric field at the receiver positions the dataset has been processed using a fast processing methodology appropriate to be applied on controlled source electromagnetics csem data with a large signal to noise ratio the dataset has been analysed in terms of data quality and repeatability errors showing data with low experimental errors and good repeatability we evaluate if the induction of current along the casing of the injection well can reproduce the behaviour of the experimental data

genesis of acid sulfate alteration and au cu ag mineralization at summitville colorado the summitville au cu ag deposit occurs within a porphyritic quartz latite primarily in a zone of vuggy silica alteration characterized by leaching of all major elements except silica and iron vuggy silica is best developed between an elevation of 3 700 and 3 500 m where it occurs in irregular pipes and lenticular pods up to 70 m wide and is enclosed by up to 30 m of intense quartz alunite alteration the vuggy silica zones diminish in size with decreasing elevation and rarely exceed a width of 2 m below an elevation of 3 400 m these deep vuggy silica zones are enclosed by quartz kaolinite alteration with little or no alunite sulfide mineralization occurs primarily within the vuggy silica the sulfide assemblage changes with decreasing elevation from covellite luzonite or native gold to chalcopyrite tennantite sulfides occur lining voids or in microveinlets and are accompanied by minor kaolinitc but not by alunite gold also occurs in a near surface barite goethite jarosite assemblage that crosscuts the vuggy silica consideration of alunite kaolinitc and pyrite stability relations and of aluminum speciation at 250 degrees c indicates that a ph of 2 or below and a log f sub o 2 of 31 or 1 at 250 degrees c were necessary to produce vuggy silica alteration the chalcopyrite tennantite mineralization occurring at depth in the vuggy silica zone is indicative of less oxidizing and less acidic conditions the covellite luzonite or gold assemblage requires conditions intermediate between those necessary for vuggy silica alteration and for deep sulfide mineralization barite gold mineralization is interpreted as a near surface assemblage produced under highly acidic oxidizing conditions these textural and geochemical relationships indicate that sulfide and gold mineralization postdate the formation of vuggy silica alteration in the deposit and are not directly related to the highly acidic solutions necessary for this early acid leaching event the change from extreme acid leaching to copper sulfide and precious metal deposition may represent a transition from a magmatic vapor dominated to a liquid dominated system leading to more reducing and less acidic conditions during sulfide deposition

experimental investigation of both the disturbed and undisturbed granitic saprolite soil granitic saprolites are abundant in many regions around the world and they are widely employed in various engineering projects behavior of such kinds of soils is not sufficiently understood and our knowledge about the fundamental behavior of saprolites is to a far less extent than the sedimentary soils owing to the limited knowledge many problems occurred in the engineering applications that used saprolites as a construction material this study presents results of a set of conventional drained and undrained triaxial compression shearing tests on the granitic saprolites in both the disturbed and undisturbed conditions this study showed that the soil fabric was the paramount factor governing on the soil stress strain response rather than the soil bonds under the drained shearing condition the undisturbed soil revealed a strain softening behavior with a dilative response at the low consolidation stress level while a contractive response was present at the high consolidation stress levels however the disturbed soil showed a strain hardening behavior with a contractive response regardless of the consolidation stress levels during the drained shearing the undrained response was complicated as the soil showed both the contractive and dilative responses with phase transformation points regardless of the soil condition i e disturbed or undisturbed and the consolidation stress levels the bond effect of the intact soil persisted during the consolidation stage however its effect did not extend to the large strain controlled shearing stage where the tangential stiffness suddenly decreased at the axial strain of 1 5

white island new zealand volcanic hydrothermal system represents the geochemical environment of high sulfidation cu and au ore deposition the white island volcanic hydrothermal system new zealand is thought to closely represent the chemical conditions that lead to the formation of high sulfidation cu au ore deposits the amounts of cu and au produced over a 10 ka period of activity largely from degassing magma are calculated to be 106 and 45 t respectively altered andesite blocks ejected from recent vents contain alunite anhydrite and pyrite their s isotopic composition indicates vein filling at 380 c at this temperature cu and au are highly soluble in acid solutions which may explain the depletion of cu and absence of au in the ejecta mass balance calculations however suggest that cu and au are precipitated in cooler zones before the acid solutions discharge at the surface

formation of rock coatings induced by the acid fumarole plume of the passively degassing volcano of la fossa vulcano island italy at la fossa volcano vulcano island and in the surrounding environment rock coatings rc develop owing to exposure of the ground surface to a volcanic acid plume this plume is produced by the passive degassing of la fossa active cone proximal and distal with respect to the high temperature fumarolic field rc have been identified which differ in mineralogy texture and chemical composition proximal rc are characterised by high silica content massive texture and strong leaching at the expense of the pyroclastic material distal rc are characterised by the presence of silica jarosite and minor goethite laminated texture and less developed evidence of leaching the rc are produced by direct interaction between the acid fumarolic aerosol and rocks and by reaction of dews and rains acidified by the absorption of acid gases so2 hcl hf of the fumarole plume with volcanic material proximal rc are produced at conditions of ph 2 distal rc form at ph 2 3 based on the presence of jarosite although the occurrence of goethite in some samples suggests higher values of ph the influence of the volcanic plume in the development of these rc is indicated also by the coincidence of the rc areal distribution with the distribution of the volcanic plume controlled by the local wind field this is furthermore supported by the presence in rc of chloride and or sulphur bearing compounds enriched in volatile elements and metals commonly carried by volcanic aerosols

a study of the effects of weathering on soils derived from decomposed volcanic rocks a comprehensive investigation was made of the effects of weathering on the nature and mechanics of volcanic saprolites from hong kong few such studies have been conducted in volcanic weathered soils and the application of a critical state type of framework that accounts for the effects of structure as has been used here is especially novel the investigation examined the effects of spatial variations of the effects of weathering both vertically as the weathering degree alters and horizontally through comparing data from different sites in addition to index tests sem and xrd an extensive series of oedometer triaxial and multi directional bender elements tests was carried out comparing the behaviour of samples from different locations and depths in both intact and reconstituted states this meant that the changes to the intrinsic reconstituted behaviour could be traced throughout different degrees of weathering along with the effects of changing structure on the mechanical behaviour of the intact soils the intrinsic properties changed in a manner that was broadly consistent with the increasing of fines content and plasticity due to weathering the effects of meso structure were small to medium in compression and in shearing they were generally even less evident both at small strains and failure the degrees of anisotropy of stiffness for both intact and reconstituted samples were mostly quite small

undrained shear behavior of cement admixed clay at high water content understanding of undrained shear behavior of cement admixed clay is of utmost importance for strength and deformation analyses in composite soft clay under short term condition from the critical analysis the distinct difference in the responses of the same clay at uncemented and induced cemented states is brought out the undrained shear behavior of uncemented clay is mainly dependent upon the clay fabric the dismembering of the clay clusters in the fabric brings about the interlocking when the clay is in overconsolidated state for the cement admixed clay the clay is in meta stable state hence the strength and deformation characteristics are controlled by the clay fabric and cementation the shear resistance is the sum of the shear resistance due to cementation iq db n and due to fabric iq df n the term iq db n is practically constant with the increase in effective confining pressure at preyield state the contribution from the clay fabric to the shear resistance iq df n comes into the picture at postyield state

mineralogy at the magma hydrothermal system interface in andesite volcanoes new zealand ejecta from phreatomagmatic eruptions of ruapehu and white island andesite volcanoes in new zealand provide insight into the mineralogical reactions that occur when magma invades a vent hosted hydrothermal system at the surface and in ejected blocks from shallow depths hydrothermal alteration mineralogies are dominated by silica polymorphs anhydrite natroalunite and pyrite blocks from greater depths are composed mainly of cristobalite anhydrite halite and magnetite where altered material was heated to magmatic temperatures thermal decomposition reactions produced mullite wollastonite and indialite some ejected breccias contain osumilite cordierite sanidine and hypersthene indicative of reactions occurring near the osumilite cordierite phase boundary at 800 c and water pressure 0 2 kbar hedenbergite wollastonite andradite and magnetite are found in rare skarn fragments possibly formed by metasomatism of silica poor sulfate rich hydrothermal deposits high temperature parageneses of these types have not been reported before in shallow acidic volcano hydrothermal systems however they may be typical of the magma hydrothermal contact zone at many andesite volcanoes

3d baseline seismics at ketzin germany the co2sink project a 3d 25 fold seismic survey with a bin size of 12 by 12 m and about 12 km 2 of subsurface coverage was acquired in 2005 near a former natural gas storage site west of berlin as part of the fiv

laboratory study on soil behavior in loess slope subjected to infiltration abstract in recent years heifangtai plateau in gansu province china has received significant attention as a loess region in which landslides frequently occur this study aims to examine the soil behavior and failure mechanism s of loess slopes subjected to water infiltration high quality samples were retrieved behind the failure plane of a landslide in heifangtai three sets of stress path tests were conducted to mimic the process of loess slope failures these tests include undrained compression on anisotropically consolidated saturated samples drained shear by decreasing mean effective stress at constant axial load on saturated samples and wetting by decreasing matric suction at constant axial load on unsaturated samples loess behavior was evaluated in terms of shear strength deformation upon shearing critical state state parameter and soil water characteristic curve three major observations were drawn from the test results first the anisotropically consolidated saturated loess exhibits a noticeable strain softening behavior upon undrained compression the peak shear strength is mobilized at less than 1 axial strain the ultimate shear strength is only 20 30 of the peak value second when subjected to shear by decreasing mean effective stress at constant axial load the saturated loess exhibits sudden failure when the confining stress is low at higher stresses the soil exhibits progressive failure third unsaturated loess deforms progressively when subjected to a reduction in matric suction i e wetting at constant axial load the failure mechanisms of the loess slopes are discussed based on the experimental findings

fracture pattern analysis as a tool for constraining the interaction between regional and diapir related stress fields poza de la sal diapir basque pyrenees spain during diapir evolution the local stress field results from the interaction between diapirrelated and remote regional stress fields the fracture pattern hosted in the overburden can register this evolving interaction providing significant insights for the unravelling of the diapir kinematics in this work we present the example of the poza de la sal diapir which is a salt diapir that pierces the synorogenic deposits of the basque pyrenees the integrated analysis of mesostructural data which includes field collected faults joints and fracture traces digitalized on high resolution orthophotos allowed us to establish an evolutionary model for the stress field around diapirs the presented data support the idea that during diapir evolution stress fields evolve from mostly regional related to mostly diapir related contrasting with other geological data seismic data geological map and cross section we observe that different methods provide complementary information coherent with the proposed evolutionary model of the poza de la sal diapir the study of fracture development associated with the growth of salt diapirs is of interest for both academic and industrial purposes in fact fractures play an important role in fluid flow and its accumulation in salt diapir related reservoirs johnson bredeson 1971 koestler ehrmann 1987 davison et al 2000a b on the other hand the analysis of fracture patterns is useful to constrain the host structure evolution thorbjornsen dunne 1997 tavani et al 2008 and accordingly can provide useful information for understanding diapir kinematics alsop 1996 stewart 2006 yin groshong 2007 yin et al 2009 the fracture pattern associated with salt diapirs and in general with doming structures is characterized by two classes of elements radial and concentric fig 1a b e g parker mcdowell 1955 withjack 1979 squyres et al 1992 branney 1995 malthe sorenssen et al 1999 rowan et al 1999 2003 davison et al 2000a b freed et al 2001 stewart 2006 this pattern is documented in simple structures where the remote stress field is negligible in relation to the diapir related stress fields when such a condition is not verified the interaction of these two stress fields leads to the development of more complex patterns ode 1957 withjack scheiner 1982 studies of interacting regional and punctual stress fields e g ode 1957 indicate that the influence of diapir induced stress progressively reduces away from the dome i e the punctual structure as a consequence far from the diapir the fracture pattern responds to the remote stress field and approaching the diapir the fracture pattern tends to be radial and concentric fig 1c although these patterns have been observed by several authors in different structures withjack scheiner 1982 mege masson 1996 ernst et al 2003 there are no detailed field studies focusing on this topic in this work we present a simple 2d theoretical stress field model where the stress tensor resulting from the interaction between remote and diapirrelated stress fields is assumed to be for a fixed distance from the diapir centre a 2 2 matrix provided by the sum of the horizontal components of the two stress tensors the eigenvectors associated with this matrix are assumed to be the principal axes of the local stress field the working hypothesis is that if the stress field changes the azimuth of fractures joints developed under these stress fields also change by understanding interactions between diapir related and regional stress fields we can predict the azimuth of the developed fractures to test the validity of this theoretical model we have applied it to a well exposed salt diapir located at the western pyrenees poza de la sal diapir this is a near circular diapir with a mainly carbonate overburden affected by a complex pattern of fractures results of this comparison indicate that despite its simplicity the provided stress model is a useful tool for understanding the kinematics of salt diapirs accordingly in this paper we provide from alsop g i archer s g hartley a j grant n t hodgkinson r eds 2012 salt tectonics sediments and prospectivity geological society london special publications 363 521 532 http dx doi org 10 1144 sp363 25 the geological society of london 2012 publishing disclaimer www geolsoc org uk pub ethics guidelines to obtain a fracture pattern using the theoretical model presented to complement other techniques of investigation such as field work or 3d seismic interpretations

behavior of a loosely compacted unsaturated volcanic soil in this paper the stress strain relationsihp and volumetric behavior of a loosely compacted unsaturated decomposed volcanic soil fill were studied by conducting three series of triaxial stress path tests 1 consolidated undrained on the saturated fill 2 constant water content and 3 a reducing suction under constant deviator stress on the unsaturated fill the last two series of tests were designed to simulate the effects of undrained response and rainfall infiltration in initially unsaturated slopes respectively it was found that the saturated loose volcanic soil behaves like clay under isotropic compression but it resembles sand behavior when it was subjected to undrained shear for isotropically consolidated unsaturated specimens sheared under a constant water content a hardening stress strain and a nonlinear shear strength suction relationship are observed at relatively high suctions both angle of friction and apparent cohesion appear to be independent of suction volumetric contraction during shear is observed in this series of tests on the other hand anisotropically consolidated loose unsaturated specimens subjected to a reducing suction change from contractive to dilative behavior as the net mean stress increases this observed volumetric behavior unlike the shear strength is stress path dependent and cannot be explained by using the existing elastoplastic critical state theoretical framework extended for unsaturated soils

transpressive inversion of a mesozoic extensional forced fold system with an intermediate decollement level in the basque cantabrian basin spain 1 in the basque cantabrian basin spain normal faulting and associated folding occurred during late jurassic to early cretaceous rifting cenozoic pyrenean thick skinned transpressive inversion in the western parts of the basin preserved the first order extensional architecture integration of geological maps and seismic profiles has permitted to fully constrain the style of extensional deformation and subsequent inversion in the western portion of the basque cantabrian basin extensional faults offset the paleozoic basement up to lower triassic rocks the presence of an efficient decollement level represented by triassic evaporites produced the decoupling between basement rocks and the upper triassic to middle jurassic prerift cover sequence extensional forced folding occurred in the cover driven by basement faulting and the migration of evaporites toward the hanging wall of the extensional faults with salt welds developing away from them upper jurassic to lower cretaceous syn rift sediments deposited synchronously with forced folding which led to the development of extensional growth geometries associated with both master faults and nearly transverse faults syn rift growth sequences are characterized by downlap and onlap relationships with the underlying prerift units interpreted as the result of along strike variations of master fault extensional displacement rate cenozoic pyrenean contraction generated the right lateral transpressive inversion of basement master faults and the almost dip slip reactivation of transverse extensional faults

laboratory studies of two common saprolitic soils in hong kong two commonly encountered saprolitic soils in hong kong weathered volcanic tuff wt and weathered granite wg were studied using high quality intact samples the intact samples exhibited quasi preconsolidation pressure or yield stress under isotropic compression due to their bonded structures but the yield was progressive and not abrupt as the stress increased significant volumetric changes were measured these changes resembled clay type behavior the soils also exhibited anisotropic deformation under isotropic loading and unloading which was associated with the features of their parent rocks during the drained tests shearing at the in situ stress state produced peak strength and volumetric dilation undrained shearing showed complicated stress paths and dilatancy behavior in these soils phase transformation states and dilative shear failure were readily seen which resembles typical sand type behavior distinct shear band s appeared in the wt specimens during shearing whereas a bulging type of failure appeared in the wg specimens the soils ultimately approached the corresponding state guided by a unique critical state line regardless of their complex initial states in relation to the bonded structure and drainage conditions

ground freezing and sampling of pleistocene sand near charleston south carolina abstractthe procedures used to freeze and sample a pleistocene sand deposit near charleston south carolina to preserve and study the effects of diagenesis are presented in this paper based on the results of geotechnical tests and a feasibility ground freezing study a freezing system with a central freeze pipe was installed to target a column of clean sand 1 m in radius and 2 3 m in length liquid nitrogen was continuously supplied to the freeze pipe fabricated to freeze the sand between depths of 1 8 and 3 8 m below the ground surface for 270 h frozen sand cores taken from five locations 0 65 to 0 7 m away from the central freeze pipe indicate the ground was frozen between depths of 1 8 and 3 8 m at all but one location ground temperature measurements growth of the frozen zone and the amount of liquid nitrogen consumed are presented and compared with predicted values recorded temperatures indicate that the freezing was influenced by the direction of groundwater flow the flow rate of liquid nitrog

the general and congruent effects of structure in natural soils and weak rocks the engineering properties of naturally occurring sedimentary and residual deposits which are usually treated in geotechnical engineering as soils are reviewed and it is shown that usually they have characteristics due to bonded structure which are similar to those of porous weak rock while this structure can arise from many causes its effects follow a simple general pattern that involves stiff behaviour followed by yield this yield can be described in a similar way to that occurring due to overconsolidation although it is a separate phenomenon the effects of structure are as important in determining engineering behaviour as are the effects of initial porosity and stress history which are the basic concepts of soil mechanics as it can be described in a general way it is concluded that structure and its effects should be treated as a further basic concept of equal importance l article passe en revue les proprietes des depots sedimentaires et residuels naturels qui sont nor malement traites comm

the foreland deformation in the south western basque cantabrian belt spain abstract in the south western portion of the cenozoic basque cantabrian belt structural data collected in pre orogenic upper cretaceous limestones were combined with aerial images interpretation in flat lying areas observations about fracture strike type orientation and overprinting relationships both at the macro and mesoscales allow to constrain the pre thrusting and pre folding deformational sequence that affected the area when it was forming part of the foreland basin wnw ese striking extensional structures represent the oldest elements developed during the very late stages of the mesozoic rifting associated with the opening of the bay of biscay the onset of convergence is marked by the development of extensional structures striking roughly nnw sse and wsw ene which are associated with belt parallel stretching in the foredeep and outer arc extension in the peripheral bulge respectively and developed in a non fluid assisted environment these elements are postdated by a pre folding layer parallel shortening pattern which includes wsw ene striking pressure solution cleavages and reverse faults both of them frequently reactivating inherited early orogenic wsw ene striking extensional elements and right lateral reactivation of wnw ese striking pre orogenic extensional structures this stage was followed by a syn to post folding e w oriented belt parallel compression wnw ese striking left lateral faults being the most outstanding elements associated with this stage the presence of such elements in upper cretaceous sediments provides support to the idea that left lateral shear zones of the area related with a cenozoic intrabelt lateral extrusion tectonics our results indicate coherently with previously published works in the pyrenean orogen that most of the mesoscale deformation has been acquired before layer s tilting

biocalcification of sand through ureolysis biological processes may provide great and previously unexplored opportunities for cost effective in situ improvement of the engineering properties of soil a laboratory study was conducted to evaluate the changes in geomechanical properties of sand attributable to the formation of calcium precipitates induced through ureolysis catalyzed by sporosarcina pasteurii s pasteurii specifically direct shear and california bearing ratio cbr tests were conducted on sand specimens subjected to treatment by growing resting and dead s pasteurii cells in completely stirred tank reactors and completely mixed biofilm reactors respectively scanning electron microscopy analyses were also conducted to evaluate microbially induced precipitation the results of the study show that the bacterial cells effectively improved the geomechanical properties of the sand growing cells improved the sand properties owing to microbially induced precipitation and related pore volume changes whereas dead and resting cells ge

mount st augustine volcano fumarole wall rock alteration mineralogy zoning composition and numerical models of its formation process abstract intensely altered wall rock was collected from high temperature 640 c and low temperature 375 c vents at augustine volcano in july 1989 the high temperature altered rock exhibits distinct mineral zoning differentiated by color bands in order of decreasing temperature the color bands and their mineral assemblages are a white to grey tridymite anhydrite b pink to red tridymite hematite fe hydroxide molysite fecl 3 with minor amounts of anhydrite and halite and c dark green to green anhydrite halite sylvite tridymite with minor amounts of molysite soda and potash alum and other sodium and potassium sulfates the alteration products around the low temperature vents are dominantly cristobalite and amorphous silica with minor potash and soda alum aphthitalite alunogen and anhydrite compared to fresh 1986 augustine lava the altered rocks exhibit enrichments in silica base metals halogens and sulfur and show very strong depletions in al in all alteration zones and in iron alkali and alkaline earth elements in some of the alteration zones to help understand the origins of the mineral assemblages in altered augustine rocks we applied the thermochemical modeling program gasworks in calculations of a reaction of the 1987 and 1989 gases with wall rock at 640 and 375 c b cooling of the 1987 gas from 870 to 100 c with and without mineral fractionation c cooling of the 1989 gas from 757 to 100 c with and without mineral fractionation and d mixing of the 1987 and 1989 gases with air the 640 c gas rock reaction produces an assemblage consisting of silicates tridymite albite diopside sanidine and andalusite oxides magnetite and hercynite and sulfides bornite chalcocite molybdenite and sphalerite the 375 c gas rock reaction produces dominantly silicates quartz albite andalusite microcline cordierite anorthite and tremolite and subordinate amounts of sulfides pyrite chalcocite and wurtzite oxides magnetite sulfates anhydrite and halides halite the cooling calculations produce a anhydrite halite sylvite b cu mo fe and zn sulfides c mg fluoride at high temperature 370 c d chlorides fluorides and sulfates of mn fe zn cu and al at intermediate temperature 170 370 c and e hydrated sulfates liquid sulfur crystalline sulfur hydrated sulfuric acid and water at low temperature

pressure oxidation autoclave as an analogue for acid sulphate alteration in epithermal systems gold extraction at the macraes gold mine in new zealand involves concentration of pyrite and arsenopyrite oxidation of those sulphides then cyanidation the ore concentrate is predominantly otago schist host rock andesitic composition with up to 15 sulphides the oxidation step is conducted on ore concentrate slurry in an autoclave at 225 c and 3 800 kpa oxygen gas pressure with continuous feed the slurry takes ca 1 h to pass through the autoclave during which time the sulphides are almost completely oxidised sulphide oxidation causes strong acidification of the slurry which is maintained at ph of 1 2 by addition of caco3 scales form on walls in the autoclave with minerals reflecting progressive oxidation and alteration of the ore through the system the schist in the ore feed has mineralogy similar to propylitically altered andesite quartz albite muscovite chlorite and pyrite muscovite undergoes almost complete dissolution with associated precipitation of quartz and alunite kal3 so4 2 oh 6 other principal minerals deposited and discharged include anhydrite and or gypsum jarosite kfe3 so4 2 oh 6 hematite and or amorphous iron oxyhydroxide and amorphous arsenates dissolved ferrous iron passes right through the autoclave and variably hydrated fe2 and fe3 sulphate minerals including rozenite and szomolnokite both feso4 hydrate and ferricopiapite fe5 so4 6o oh hydrate are formed along the way the autoclave chemical system resembles acid sulphate hydrothermal activity in geothermal systems and high sulphidation epithermal mineral deposits formed in arc environments these natural acid sulphate systems are pervaded by volcanic vapours in the near surface environment where widespread dissolution of host rocks occurs and deposition of quartz alunite and anhydrite is common some of the volume loss associated with these natural systems may be due to dissolution of soluble sulphate minerals by later stage groundwater incursion

seismic models of a carbonate foreslope to basin transition picco di vallandro dolomite alps northern italy detailed geologic cross sections augmented by laboratory calibration of lithology and acoustic impedance have been used to produce synthetic reflection seismic sections of a carbonate foreslope to basin transition two areas from the picco di vallandro region of the dolomite alps were modeled a progradational section and a retrogradational backstepping section the resulting models show how these complex areas of strata interfingering might be displayed on conventional reflection seismic lines in the area of progradation rapid stratigraphic thinning below seismic detectibility coupled with abrupt impedance changes produces a reflection discontinuity between steeply dipping reflections of the foreslope and gently dipping parallel reflections of the basin section this apparent downlap surface marks the toe of slope for successive clinoforms but does not correspond to a discrete stratigraphic surface in the backstepping example similar stratigraphic thinning and impedance changes create an apparent onlap surface wavelet interference causes complications in both examples these models indicate how stratigraphic complexity can be simplified by the seismic reflection process and suggest that caution should be exercised when using seismic data to construct general models in areas of complex depositional geometries and rapidly changing facies

influence of the flow rate on dissolution and precipitation features during percolation of co2 rich sulfate solutions through fractured limestone samples abstract calcite dissolution and gypsum precipitation are expected to occur when injecting co2 in a limestone reservoir with sulfate rich resident brine if the reservoir is fractured these reactions will take place mainly in the fractures which serve as preferential paths for fluid flow as a consequence the geometry of the fractures will vary leading to changes in their hydraulic and transport properties in this study a set of percolation experiments which consisted of injecting co2 rich solutions through fractured limestone cores was performed under p 150 bar and t 60 c flow rates ranging from 0 2 to 60 ml h and sulfate rich and sulfate free solutions were used variation in fracture volume induced by calcite dissolution and gypsum precipitation was measured by x ray computed microtomography xcmt and aqueous chemistry an increase in flow rate led to an increase in volume of dissolved limestone per unit of time which indicated that the calcite dissolution rate in the fracture was transport controlled moreover the dissolution pattern varied from face dissolution to wormhole formation and uniform dissolution by increasing the flow rate i e pe from 1 to 346 fracture permeability always increased and depended on the type of dissolution pattern

seismic models of a mixed carbonate siliciclastic shelf margin permian upper san andres formation last chance canyon new mexico seismic models based on randomly distributed samples from the permian upper san andres formation last chance canyon new mexico verify that the most prominent seismic reflections are related to stratal geometry however at least some reflections arise from lateral facies transitions that are commonly associated with highly prograding mixed carbonate siliciclastic sediments understanding seismic reflections and reflection terminations in sedimentary rocks requires simulation of at least 2 d cross sections of the impedance distribution to investigate the cause of reflections in strongly prograding mixed carbonate siliciclastic shelf margins acoustic velocity and bulk density were measured on more than 60 plugs that spatially cover one higher order genetic sequence the resulting impedance values were gridded and contoured and the genetic sequence was repeated to create a cross section averaging impedance values for each lithofacies zone generated a second impedance cross section seismic models of both impedance cross sections revealed the following observations 1 reflections associated with the sequence boundaries are subject to amplitude and polarity phase changes and 2 at least one reflection within the high order sequences is related to subhorizontal facies changes and is associated with two pseudounconformities the contoured impedance model is suggested to closer resemble the true impedance function in outcrop and shows subtle vertical shifts and significantly higher impedance contrasts

3d visualization of carbonate reservoirs conventional 2d and 3d seismic mapping is not ideal for characterizing carbonate reservoirs mainly because of the complexity and heterogeneity of carbonate systems the unique depositional systems of carbonate environments means that a standard interpretation routine is often inadequate and more sophisticated techniques are needed

cenozoic right lateral wrench tectonics in the western pyrenees spain the ubierna fault system abstract a study of macro and mesostructural deformation patterns of the southern margin of the cantabrian area western pyrenees spain has revealed a complex cenozoic tectonic framework right lateral tectonics reactivated inherited wnw ese striking faults which developed during late paleozoic and early triassic events and late jurassic to early cretaceous main rifting stage the ubierna fault represents the southern boundary of the mesozoic basin during the oligocene even eocene to present day deformation this fault and the ventaniella fault located to the south in the study area acted as right lateral slightly transpressive elements forming a 120 km long and 15 km wide overstep area here named ubierna fault system where the cumulative right lateral displacement exceeds 15 km the cenozoic tectonic framework of the ubierna fault system includes reactivation along the wnw ese faults development of negative and mostly positive flower structures branch faults strike slip duplexes and releasing and restraining bends ne sw to ene wsw striking reverse faults and contractional horsetail terminations and nnw sse striking normal faults and joints are produced by the wnw ese right lateral strike slip motion the extensional elements are well developed and deformation progression implied their incorporation in the strike slip system as right lateral faults forming part of strike slip duplexes the abundance of flower structures striking wnw ese and paralleling the main strike slip faults together with the overall uplift of the overstep area testifies for a slight compressional component at a regional scale the ubierna fault system represents the most prominent element of a cenozoic transpressional belt which incorporates the western portion of the basque cantabrian basin and the asturian massif area lateral transition between this transpressive belt and the dip slip belt located to the east occurs across an area experiencing along strike shortening which developed to accommodate the eastward extrusion of the transpressional belt

3d geological characterization of the hontomin co2 storage site spain multidisciplinary approach from seismic well log and regional data abstract the first spanish technological development plant for co2 storage is currently under development in hontomin spain in a fractured carbonate reservoir the subsurface 3d geological structures of the hontomin site were interpreted using well log and 3d seismic reflection data a shallow low velocity zone affects the wave propagation and decreases the coherency of the underlying seismic reflections deteriorating the quality of the seismic data and thus preventing a straightforward seismic interpretation in order to provide a fully constrained model a geologically supervised interpretation was carried out in particular a conceptual geological model was derived from an exhaustive well logging analysis this conceptual model was then improved throughout a detailed seismic facies analysis on selected seismic sections crossing the seismic wells and in consistency with the regional geology leading to the interpretation of the entire 3d seismic volume this procedure allowed characterizing nine main geological levels and four main fault sets thus the stratigraphic sequence of the area and the geometries of the subsurface structures were defined the resulting depth converted 3d geological model allowed us to estimate a maximum co2 storage capacity of 5 85 mt this work provides a 3d geological model of the hontomin subsurface which is a challenging case study of co2 storage in a complex fractured carbonate reservoir

exploring for dolomitized slave point carbonates in northeastern british columbia in northeastern british columbia a number of significant gas fields have been discovered in dolomitized slave point carbonates located along the edge of the mid devonian barrier reef system reflection seismic techniques have been used extensively in exploring for these fields a common exploration practice has been to detect the reef edge on seismic data and then to drill on isochron thins and structural highs close to this edge the remaining reserves however are proving more difficult to find and this exploration technique does not always guarantee that the slave point formation is dolomitized at this location as with many other complex play types combining geologic concepts with geophysical exploration techniques can improve the explorationist s success ratio in this example a geologic model the dorag dolomitization model provides a possible explanation for the localization of the slave point dolomites in this model dolomitizing solutions are created by mixing fresh phreatic water with sal

3 d seismic analysis of a carbonate platform in the molasse basin reef distribution and internal separation with seismic attributes abstract carbonate platforms differ from clastic sedimentary environments by a greater heterogeneity so that key horizons for mapping and compartmentalisation of the reservoir are generally missing we show that different seismic attributes help to compete with these difficulties and to identify different carbonate facies within the platform the upper jurassic carbonate platform in southern germany in the molasse basin is a main exploration target for hydrogeothermal projects knowledge about the distribution of different carbonate facies within the platform which is overprinted by faults is important for a realistic reservoir simulation the platform with an average thickness of 600 meters was artificially divided into four layers of equal thickness within each layer the characteristic seismic pattern was visualized by different attributes travel time mapping spectral decomposition allowing additionally for further depositional classification within the uppermost layer the coral reef distribution could be mapped the reefs form several complexes of up to 12 square kilometres in size the surrounding slope and trough areas are identified as well within the platform the distribution of sponge reefs could be visualized they form either amalgamations in distinct areas or are spread as small singular structures with diameters of approximately less than hundred meters comparing tectonic elements and reef distribution within the whole platform reveals that the early topography triggered the reef distribution while these lithologic inhomogenities influenced later on the local shape of tectonic lineaments the fault system which dominates the structural style in the area is visible in the different transformations but does not obscure the facies distribution which hindered former interpretations of the data set in this way a reservoir model can incorporate now the first time the reef distribution within an area