reservoir compartmentalization an introduction reservoir compartmentalization the segregation of a petroleum accumulation into a number of individual fluid pressure compartments occurs when flow is prevented across sealed boundaries in the reservoir these boundaries are caused by a variety of geological and fluid dynamic factors but there are two basic types static seals that are completely sealed and capable of withholding trapping petroleum columns over geological time and dynamic seals that are low to very low permeability flow baffles that reduce petroleum crossflow to infinitesimally slow rates the latter allow fluids and pressures to equilibrate across a boundary over geological time scales but act as seals over production time scales because they prevent crossflow at normal production rates such that fluid contacts saturations and pressures progressively segregate into dynamic compartments thus reservoir compartmentalization impacts the volume of moveable produceable oil or gas that might be connected to any given well drilled in a field which restricts the volume of reserves that can be booked for that field booking of reserves is tightly regulated by government authorities because it is a key measure used by stock analysts and investors to value an oil company this places reservoir compartmentalization studies and the predictive science and technology applied to them at the heart of company valuation unexpected compartmentalization can also seriously impact the profitability of a field with more data acquisition more study more wells more time being required to produce less oil and gas than was originally anticipated in extreme cases this might even lead to early field abandonment however unexpected or misunderstood reservoir compartmentalization has been an industrywide experience for over 30 years and it is clear that there is great value in learning from past often expensive mistakes e g smith 2008 this learning process has often driven developments in geoscience engineering and related technology enabling operating companies to identify and predict new untapped volumes in old fields make general improvements to field management e g gainski et al wonham et al and apply this knowledge to other similar but lessmature fields in their portfolio reservoir compartmentalization is therefore a major uncertainty that should be accurately assessed during the appraisal of petroleum reservoirs in order to avoid unexpected compartmentalization at the production stage in the past few decades there have been major advances in data detection and surveillance methods and our geoscience and reservoir engineering approaches however reservoir compartmentalization can still be underestimated during field appraisal and can still give surprises that force a re think of the field development and production plan e g smith 2008 this is not necessarily a defect in the science or technology but rather it may also be a result of ineffectual data appraisal or discipline integration within subsurface workflows thus it is not unusual for subsurface teams to place too much emphasis on one aspect of the evidence or to make early assumptions that bias data acquisition analyses and interpretations later on for example fisher jolley 2007 point out that non existent faults or improbable fault seal capacities might be invoked to explain variable petroleum contacts and dynamic fluid pressure behaviour when an alternative or combination of factors or other unrelated explanations might be more appropriate for the data e g hydrodynamic tilting of petroleum contacts tozer borthwick research initiatives and collaborations between oil companies service groups and academic institutions vary considerably in scope and content and there is often a creative tension between the competitive advantages motivations and knowledge gaps perceived by the sponsoring companies and their research partners in addition to this the scientific insights that can be gained from the

the dissolution kinetics of brucite antigorite talc and phlogopite at room temperature and pressure dissolution experiments were done on a series of layer type mg minerals brucite antigorite talc and phlogopite of progressively more complex structure and chemical composition twenty five gram portions of these minerals were dry ground to 400 mesh and then subjected to controlled dissolution in distilled water at 25 c and i atm co2 partial pressure for antigorite talc and phlogopite mg from the octahedral sheets was released more rapidly than was si from the tetrahedral sheets r e the dissolution was incongruent it appears that the solubility of these layer type minerals is related to the relative number of octahedral to tetrahedral sheets present in the structure i e the dissolution kinetics of layer type silicate minerals is controlled bv the rate of destruction of the tetrahedral silica sheets of the mineral

how are diagenesis and reservoir quality linked to depositional facies a deltaic succession edgeoya svalbard abstract middle to late triassic strata exposed at edgeoya eastern svalbard represents an uplifted part of the northwestern corner of the barents sea this interval is characterized by a predominantly mud dominated deltaic depositional system where rocks with petroleum reservoir potential are expected both in delta front and channelized sandstone deposits recent drilling campaigns into time equivalent rocks in the barents sea have however been disappointing with porosity and permeability below expectation this study improves the current understanding of reservoir potential within depositional systems of this kind by examining the link between different depositional facies diagenesis and their impact on reservoir quality five depositional facies were mapped and correlated channel floodplain shallow marine prodelta and offshore our study suggests that diagenetic signatures that control the quality of reservoir rocks vary systematically with these depositional facies mechanical compaction was the main cause of porosity destruction in the channel shallow marine and floodplain samples while early carbonate cementation occludes the intergranular volume in the prodelta samples moreover quartz cement reduced the porosity in the shallow marine depositional facies the estimated maximum burial temperature of 124 c indicates burial to several km depths depositional settings within a deltaic to shallow marine system do not exert a strong control on the abundance of chlorite but it does impact whether the chlorite is pore filling or grain coating and porosity preserving efficient chlorite coating have aided in preserving porosities up to 32 in the very well well sorted medium to fine grained sandstones deposited by fluvial dominated channels

the transformation of nesquehonite to hydromagnesite in the system cao mgo h20 co2 an experimental spectroscopic study abstract this study reports the nature of the nesquehonite to hydromagnesite transition at 52 c in an aqueous medium hosting magnesian calcite and nesquehonite the latter mineral occurs with abundant calcite at the floor of the experimental chamber substrate and as a film of needles at the interface between the mother liquor and the atmosphere surface film the experimental vessel was held at 52 c for 336 h and at 60 c for a further 192 h precipitates were analyzed by fourier transform ft raman augmented by ft infrared and x ray diffraction at 52 c hydromagnesite and dypingite occur with abundant quantities of a hitherto unreported transitory magnesium hydrate carbonate tmhc together with huntite magnesian calcite and traces of nesquehonite and monohydrocalcite the ft raman spectra of the first formed hydromagnesite crystals contain the raman forbidden v2 mode interpreted to indicate a relaxation in selection rules caused by rapid precipitation hydromagnesite growth at the expense of t

the morphology and dynamics of low amplitude bedwaves upon upper stage plane beds and the preservation of planar laminae experimental studies of subcritical unidirectional flow over upper stage plane beds of medium grained sand reveal the ubiquitous presence of low amplitude bedwaves flow depth was 0 11 m mean flow velocities were 0 86 1 0 m s 1 shear velocities were 0 058 0 71 m s 1 and dimensionless shear stresses were 0 56 0 87 bedwaves are asymmetrical in profile and range from 0 75 to 11 mm in height mainly 2 6 mm from 0 7 to 1 3 m in wavelength and have mean celerities of 10 mm s 1 flow records suggest that the bedwaves are associated with accelerating flow over the bedwave crests and flow which decelerates and diverges laterally over the troughs high resolution bed profiling during aggradation of the bed combined with subsequent box coring illustrates that these bedwaves are responsible for the planar laminae characteristic of upper stage plane beds lamina preservation is dependent upon the mean aggradation rate and the sequence of bedwaves of different height crossing any point individual laminae are more readily preserved at higher aggradation rates where the possibility of reworking by later bedwaves is reduced laminae are recognized by small changes in grain size and commonly a fining upwards at the top of laminae which is generated by fine grained material infiltrating a lower lamina in the leeside of a bedwave

holocene vegetation change in the northern peten and its implications for maya prehistory an 8400 cal yr record of vegetation change from the northern peten guatemala provides new insights into the environmental history of the archaeological area known as the mirador basin pollen loss on ignition and magnetic susceptibility analyses indicate warm and humid conditions in the early to mid holocene evidence for a decrease in forest cover around 4600 cal yr b p coincides with the first appearance of zea mays pollen suggesting that human activity was responsible the period between 3450 cal yr b p and 1000 cal yr b p is characterized by a further decline in forest pollen types includes an abrupt increase in weedy taxa and exhibits the highest magnetic susceptibility values since the early holocene all of which suggest further agricultural disturbance in the watershed a brief drop in disturbance indicators around 1800 cal yr b p may represent the preclassic abandonment of the area changing pollen frequencies around 1000 cal yr b p indicate a cessation of human disturbance which represents the late classic collapse of the southern maya lowlands

experimental determination of the effect of dissolved co2 on the dissolution kinetics of mg and ca silicates at 25 c dissolution rates of diopside forsterite fo100 and fo92 wollastonite and hornblende were measured at 25 c in nacl solutions as a function of ph 1 ph 12 pco2 0 and 1 atm and activity of hco3 and co32 10 5 co2 0 1 m dissolution rates of diopside forsterite and horneblende are not affected within the experimental uncertainty by 1 atm pco2 at ph 4 and by the presence of bicarbonate up to 0 1 m and carbonate up to 0 01 m ions at ph of 8 and 11 12 respectively although wollastonite dissolution rates are unaffected by pco2 at ph 4 its rates are increased by the presence of hco3 at 0 01 hco3 0 1 m and ph 7 8 and decreased slightly by co32 at co32 0 0001 m and ph 12 these results should be useful for modeling the effect of silicate rock weathering on the global biogeochemical cycle of carbon for the first time we were able to distinguish the net effect of pco2 versus that of ph it is observed in general accord with previous results that the direct effect of co2 on basic silicates dissolution rates is very weak as a result the major parameter governing basic silicates dissolution is ph of soil solutions in contact with minerals

the effects of grain density variation on turbidity currents and some implications for the deposition of carbonate turbidites abstract sediment grains in carbonate turbidity currents vary greatly in size shape surface texture and density depending on the evolution of the source carbonate platform in time and space facies character and distribution may vary from traditional siliciclastic turbidite models not only because of the difference in composition but also because variation in grain properties influences flow and depositional behavior experimental gravity flows were generated to investigate one control on this variation the experiments used silicon carbide 3214 kg m 3 and glass ballotini 2650 kg m 3 with a similar grain size distribution in varying proportions to assess the influence of particle density on flow and sedimentation processes mixed particle density flows were more efficient than single particle density flows flow propagation was faster in flows with greater initial bulk density determined by grain density and suspended sediment concentration with mixed particle suspensions flow propagation velocity was maintained for longer due to the presence of low settling velocity particles as a result mixed particle density flows transported more sediment downstream compared to single particle density flows of similar initial suspended sediment volume concentration because of the wider range of grain types in carbonate turbidity currents they may more effectively transport coarse sand grade sediment to more distal sites in a marine basin compared to siliciclastic counterparts of equivalent initial volume this results in differences in bed and facies geometry and distribution

deep to shallow marine sedimentology and impact of volcanism within the middle triassic palaeo tethyan semantan basin singapore abstract the middle triassic pulau ayer chawan formation is a predominantly deep marine occasionally shallow marine sedimentary succession deposited in the singapore sector of the palaeo tethyan semantan basin the formation provides an important record of the dynamic interplay between a siliciclastic sedimentary system and the products of an adjacent active volcanic arc it is characterised by six sub environments including deep marine turbidite fan deep marine background sedimentation subaqueous debris cone shallow marine volcanically sourced turbidite fan and hyaloclastite mound or ridge turbidite fan deposits preserve the input of both siliciclastic and volcaniclastic sediments from the shelf transported into the deep marine environment by a suite of subaqueous sediment gravity flow processes including turbidity currents mixed flow types hybrid event beds concentrated and hyper concentrated sediment gravity flows and debris flows thick heterolithic successions of debrites were likely sourced through regular collapse of an unstable shelf the presence of hybrid event beds encountered within the deep marine turbidite fans supports a slope that was out of grade and may have been actively retreating towards the hinterland together these factors suggest regional scale uplift of the eastern margins of the semantan basin during triassic times most likely facilitated through volcanic activity in the adjacent palaeo tethys sukhothai arc evidence for contemporaneous arc related magmatism includes ubiquitous volcaniclastic sedimentary rocks within formation including pyroclastic density current deposits and perhaps more strikingly through the hyaloclastites of the nanyang member the hyaloclastites formed through quenching of magmas delivered into the deep marine setting from a series of sub sea vents or mounds

onset of submarine debris flow deposition far from original giant landslide submarine landslides can generate sediment laden flows whose scale is impressive individual flow deposits have been mapped that extend for 1 500 km offshore from northwest africa these are the longest run out sediment density flow deposits yet documented on earth this contribution analyses one of these deposits which contains ten times the mass of sediment transported annually by all of the world s rivers understanding how this type of submarine flow evolves is a significant problem because they are extremely difficult to monitor directly previous work has shown how progressive disintegration of landslide blocks can generate debris flow the deposit of which extends downslope from the original landslide we provide evidence that submarine flows can produce giant debris flow deposits that start several hundred kilometres from the original landslide encased within deposits of a more dilute flow type called turbidity current very little sediment was deposited across the intervening large expanse of sea floor where the flow was locally very erosive sediment deposition was finally triggered by a remarkably small but abrupt decrease in sea floor gradient from 0 05 degrees to 0 01 degrees this debris flow was probably generated by flow transformation from the decelerating turbidity current the alternative is that non channelized debris flow left almost no trace of its passage across one hundred kilometres of flat 0 2 degrees to 0 05 degrees sea floor our work shows that initially well mixed and highly erosive submarine flows can produce extensive debris flow deposits beyond subtle slope breaks located far out in the deep ocean

atmospheric carbon sequestration in ultramafic mining residues and impacts on leachate water chemistry at the dumont nickel project quebec canada abstract passive carbon mineralization in ultramafic mining residues which allows the sequestration of co2 through carbonate precipitation is one of the options being considered to limit the accumulation of anthropogenic co2 in the atmosphere the dumont nickel project dnp will generate approximately 1 7 gt of utramafic mining residues over 33 years of production and the mine will release about 127 700 tonnes of co2 each year using two experimental cells filled with ultramafic waste rock ec 1 and milling residues ec 2 the impacts of carbon mineralization on leachate water quality were studied and the quantity of sequestered carbon was estimated hydrotalcite supergroup minerals aragonite artinite nesquehonite dypingite and hydromagnesite precipitated through atmospheric weathering while the inorganic carbon content of the weathered mining waste increased from 0 1 wt to 4 0 wt which indicates active co2 sequestration the leachate water sampled at the bottom of the experimental cells is characterized by an alkaline ph 9 5 a high alkalinity 90 to 750 mg l and a high concentration of magnesium 50 750 mg l which is typical from weathering of ultramafic rocks in a system open to co2 since 2012 the chemical composition of the leachate water has evolved seasonally these seasonal variations are best explained by 1 climatic variations over the year and 2 increased carbonate precipitation between may and july increased carbonate precipitation decreased the alkalinity and magnesium concentrations in the leachate water and produced pore waters which were undersaturated with respect to carbonate minerals such as artinite and hydromagnesite carbonate precipitation thus self limits carbon sequestration through a negative feed back loop the carbon sequestration potential of the dnp residues is also influenced by the hydrogeological properties of the residues in cell ec 2 a high liquid solid ratio which limits carbonate precipitation was maintained by the hydrogeological properties since 2011 an estimate of 13 kg of atmospheric co2 has been sequestered in the milling residues ec 2 which corresponds to a mean rate of 1 4 0 3 kgco2 tonne year using this mean rate the 15 mt of tailings produced each year during the planned 33 years of mining operation could potentially sequester 21 000 tonnes of co2 per year by passive carbon mineralization about 16 of the 127 700 tonnes of co2 annually emitted by the planned mining operation

carbon dioxide fixation within mine wastes of ultramafic hosted ore deposits examples from the clinton creek and cassiar chrysotile deposits canada carbon dioxide co2 is sequestered through the weathering and subsequent mineralization of the chrysotile mine tailings at clinton creek yukon territory and cassiar british columbia canada accelerated weathering is attributed to a dramatic increase in surface area which occurs during the milling of ore we provide a detailed account of the natural process of carbon trapping and storage as it occurs at clinton creek and cassiar including mineralogy modes of occurrence methods of formation for carbonate alteration light stable isotope geochemistry and radiocarbon analysis powder x ray diffraction data were used to identify weathering products as the hydrated magnesium carbonate minerals nesquehonite mgco3 3h2o dypingite mg5 co3 4 oh 2 5h2o hydromagnesite mg5 co3 4 oh 2 4h2o and less commonly lansfordite mgco3 5h2o textural relationships suggest that carbonate precipitates formed in situ after milling and deposition of tailings samples of efflorescent nesquehonite are characterized by 13c values between 6 52 and 14 36 per mil 18o values between 20 93 and 26 62 per mil and f14c values fraction of modern carbon between 1 072 and 1 114 values which are consistent with temperature dependent fractionation of modern atmospheric co2 during mineralization samples of dypingite hydromagnesite collected from within 0 2 m of the tailings surface give 13c values between 1 51 and 10 02 per mil 18o values between 17 53 and 28 40 per mil and f14c values between 1 026 and 1 146 which suggests precipitation from modern atmospheric co2 in a soil like environment field observations and isotopic data suggest that hydrated magnesium carbonate minerals formed in two environments nesquehonite formed in an evaporative environment on the surface of tailings piles and dypingite and hydromagnesite formed in the subsurface environment with characteristics similar to soil carbonate in both cases these minerals

geochemical correlation in an exhumed submarine channel complex tabernas basin se spain comparison to sedimentological correlation at various length scales abstract whole rock inorganic geochemical data have previously been used to aid characterization and stratigraphic correlation of fossil poor clastic sedimentary deposits although this approach has not yet been calibrated by testing chemostratigraphic correlations against physical stratigraphic correlations from outcrop chemical data from a well exposed siliciclastic succession in a tortonian late miocene submarine slope channel system in the tabernas basin of southern spain were generated using x ray fluorescence supplemented by x ray diffraction sem analysis and light microscopy amongst the 60 elements measured nearly a quarter of them have proved to be useful or reliable for geochemically based correlation at the tested scales 10 m 50 m 100 m these elements are sio2 k2o al2o3 cao and tio2 as well as zr nb th rb cs as and the rare earth elements la nd and ce high resolution bed to bed geochemical correlation is feasible over short distances 10 m geochemical data from sections in beds that are traceable suggest that a given stratigraphic level seems to be geochemically homogeneous with respect to some key elements geochemical data also provide a useful aid for high resolution sedimentary correlation at distances of several tens of meters up to at least 100 m since each individual bed seems to be broadly homogeneous in composition at a larger scale it is possible to discern a provenance signal in geochemical data chemical stratigraphy thus seems to work even in stratigraphically complicated submarine channel complexes

an 8000 year record of vegetation climate and human disturbance from the sierra de apaneca el salvador abstract an 8000 cal yr stratigraphic record of vegetation change from the sierra de apaneca el salvador documents a mid holocene warm phase followed by late holocene cooling pollen evidence reveals that during the mid holocene 8000 5500 cal yr b p lowland tropical plant taxa were growing at elevations 200 250 m higher than at present suggesting conditions about 1 0 c warmer than those prevailing today cloud forest genera liquidambar juglans alnus ulmus were also more abundant in the mid holocene indicating greater cloud cover during the dry season a gradual cooling and drying trend began by 5500 cal yr b p culminating in the modern forest composition by 3500 cal yr b p a rise in pollen from weedy plant taxa associated with agriculture occurred 5000 cal yr b p and pollen from zea first appeared in the record at 4440 cal yr b p human impacts on local vegetation remained high throughout the late holocene but decreased abruptly following the tierra blanca joven tbj eruption of volcan ilopango at 1520 cal yr b p the past 1500 years are marked by higher lake levels and periodic depositions of exogenous inorganic sediments perhaps indicating increased climatic variability

petrography and temporal changes in petrofacies of deep marine ainsa jaca basin sandstone systems early and middle eocene spanish pyrenees a petrographic study of 157 samples from the early to middle eocene deep marine sandy systems ainsa jaca basin spanish pyrenees shows that each system has a characteristic petrofacies three main petrofacies are recognized petrofacies 1 sandstones comprise mainly siliciclastic grains 80 subordinate terrigenous carbonate grains and negligible intrabasinal grains petrofacies 2 hybrid arenites are characterized by significant amounts 10 of intrabasinal carbonate grains petrofacies 3 calcilithites contain relatively abundant 10 extrabasinal carbonate grains on the basis of these petrofacies a revised correlation of the sandy systems is proposed between the more proximal ainsa basin and the more distal jaca basin sediments now separated by the boltana anticline across which it is impossible to actually trace out individual beds or sandstone packages between both basins the arenite composition in the ainsa and jaca basins is interpreted as being controlled mainly by synsedimentary tectonic processes that led to changes in sediment sources during basin evolution

the stratigraphic record and processes of turbidity current transformation across deep marine lobes sedimentary facies in the distal parts of deep marine lobes can diverge significantly from those predicted by classical turbidite models and sedimentological processes in these environments are poorly understood this gap may be bridged using outcrop studies and theoretical models in the skoorsteenberg formation south africa a downstream transition from thickly bedded turbidite sandstones to argillaceous internally layered hybrid beds is observed the hybrid beds have a characteristic stratigraphic and spatial distribution being associated with bed successions which generally coarsen and thicken upward reflecting deposition on the fringes of lobes in a dominantly progradational system using a detailed characterization of bed types including grain size grain fabric and mineralogical analyses a process model for flow evolution is developed this is explored using a numerical suspension capacity model for radially spreading and decelerating turbidity currents the new model shows how decelerating sediment suspensions can reach a critical suspension capacity threshold beyond which grains are not supported by fluid turbulence sand and silt particles settling together with flocculated clay may form low yield strength cohesive flows development of these higher concentration lower boundary layer flows inhibits transfer of turbulent kinetic energy into the upper parts of the flow ultimately resulting in catastrophic loss of turbulence and collapse of the upper part of the flow advection distances of the now transitional to laminar flow are relatively long several kilometres suggesting relatively slow dewatering several hours of the low yield strength flows the catastrophic loss of turbulence accounts for the presence of such beds in other fine grained systems without invoking external controls or large scale flow partitioning and also explains the abrupt pinch out of all divisions of these sandstones estimation of the point of flow transformation is a useful tool in the prediction of heterogeneity distribution in subsurface systems

downstream evolution of turbiditic channel complexes in the pab range outcrops maastrichtian pakistan the pab formation consists of deltaic and turbiditic sediments which were deposited during the late maastrichtian on the indo pakistani passive margin the margin geometry has been restored in the pab range from a regional transect 120 km long two superposed turbiditic systems onlap the slope carbonates and completely pinch out southward the lowest turbiditic system lower pab is a sand rich basin floor fan which consists of sand rich channel complexes distally passing to lobes northward this basin floor fan is overlain by a mud rich slope fan formed during the subsequent sea level rise which drowned the shelf the upper turbiditic system upper pab is a sand rich slope fan formed during the progradation of a deltaic system in the shelf setting it consists of prograding tabular lobes passing upward to conglomeratic channels and thins out northwards the lower pab turbiditic system consists of three channel complexes lp1 2 3 organised in a backstepping succession each channel complex has a multi storey internal architecture resulting from the amalgamation of several individual turbiditic channels five major facies associations have been determined in the lp3 channel complex fa 1 corresponds to polygenic and monogenic debris flows fa 2 to high density gravelly or sandy turbidites fa 3 to by pass deposits fa 4 to thin bedded turbidites spill over lobes and levees and fa 5 to hemipelagites the downstream evolution of the lp3 channel complex can be studied from canyon to mid fan settings where it is confined in the canyon the channel complex is 50 m thick and 1 km large and shows a high sand shale ratio the development of overflow deposits is limited and occurs only at the top of the channel complex at the canyon mouth the channel complex is still deeply incised but overflow deposits start to expand laterally as a result of the decreased confinement by pass facies here are well developed and are related to hydraulic jump processes in the mid fan setting the channel complex widens and the sand shale ratio decreases erosion at the channel base is less developed whereas internal and external levees are well developed spill over lobes form the last stage of the channel complex infill the internal geometry of the channel complexes is a result of a complex interaction between lateral confinement by pass and lateral migration processes

high resolution correlation patterns in the turbidite systems of the hecho group south central pyrenees spain detailed bed by bed correlations in sheetlike lobes and basin plain elements of the hecho group were carried out through a hierarchical decomposition based on three orders of correlation this procedure provides the most detailed correlation framework with chronostratigraphic significance first order decomposition is based on physical correlation by mapping of major megaturbidites second order decomposition consists in matching a series of marker beds within first order units leading to the definition of units several metres thick finally third order decomposition relies on the matching of serial features within second order packages number vertical arrangement and facies features of beds and further testing the coherence of the downstream evolution of facies in single beds sheetlike lobes and basin plain are closely related and display a distinctive sheet like geometry basin plain beds are deposited by the same flows that build the sheetlike lobes with the existence of a transitional facies change from the lobe to the basin plain thickening of some beds towards the basin plain due to ponding of the fine grained silt and mud divisions a diagnostic feature of the basin plain controls the sheet like stacking pattern by balancing the wedging out of thinner lobe beds upcurrent from or within the basin plain as a consequence the whole area can be geomorphically classified as a basin plain which comprises both lobe and basin plain facies associations

kinetic testing to evaluate the mineral carbonation and metal leaching potential of ultramafic tailings case study of the dumont nickel project amos quebec abstract ultramafic mine wastes are known to react passively with co 2 to form stable hydrated magnesium carbonates this study uses kinetic tests to evaluate the carbonation potential of ultramafic mine tailings from the dumont project rnc minerals quebec canada during their weathering and to determine the impact of carbonation on the long term quality of drainage waters the weathering of awaruite ni 2 5 fe pentlandite fe ni 9 s 8 and heazlewoodite ni 3 s 2 which are the main sources of ni in the studied materials were also investigated due to their potential to generate contamination a column test and small scale weathering cell tests were used to simulate the passive weathering of ultramafic mine wastes as well as concentrates of awaruite and ni sulfides results from the kinetics tests confirmed that the dumont tailings have a significant carbon sequestration potential which ranged from 8 5 to 33 6 kgco 2 t the surface normalized carbonation rates varied from 600 to 2200 g of co 2 m 2 year results demonstrated that brucite mg oh 2 content is the main parameter controlling co 2 uptake by the dumont wastes weathering of brucite and serpentine mg 3 si 2 o 5 oh 4 are driven by co 2 dissolution in pore water and by sulfide oxidation the rapid dissolution of brucite results in leachates with alkaline ph values thus preventing metal mobility metals such as ni zn fe and cu are suggested to precipitate as hydroxide or carbonate species within the wastes immediately upon being released through sulfide oxidation the ni fe alloy awaruite is stable and does not release metals in kinetic tests the dumont tailings are found to be non acid generating and co 2 sequestration is shown to play a significant role in drainage water quality which allow generation of significant alkalinity and the rise of ph

fluvial architecture and reservoir compartmentalization in the oligocene middle frio formation south texas abstract seeligson stratton and agua dulce fields south texas are being studied as part of a gas research institute department of energy state of texas cosponsored program designed to develop and test methodologies and technologies for gas reserve growth in conventional reservoirs in mature gas fields over the last five decades each field has produced approximately 2 tcf of gas from middle frio reservoirs alone recent drilling old well workover results and reservoir pressure data however point to the possibility of additional reserves within these fields the middle frio oligocene is composed of sand rich channel fill and splay deposits interstratified with floodplain mudstones all forming part of the gueydan fluvial system channel fill deposits are 30 ft 9 m thick and 2 500 ft 76 m wide splay deposits are as much as 20 ft 6 m thick proximal to channels and extend as much as 2 mi 3 km from channels channel fill and associated splay sandstones are reservoir facies porosity 20 percent permeability 10 s to 100 s md floodplain mudstones and levee sandy mudstones impede or obstruct flow and separate individual reservoirs and compartments both vertically and laterally deposition on an aggrading coastal plain resulted in a continuum of fluvial architectural styles that has important implications for reservoir compartmentalization relatively slow aggradation resulted in laterally stacked channel systems whereas more rapid aggradation resulted in vertically stacked channel systems in seeligson field laterally stacked architecture alternates with vertically stacked architecture through the 2 000 ft 610 m thick middle frio section in stratton and agua dulce fields the same general alternation in architectural modes exists through the 2 500 ft 763 m thick middle frio section in stratton and agua dulce however the reservoir zones composed of laterally stacked architecture are not laterally continuous instead the laterally stacked architecture locally changes into a vertically stacked architecture because laterally stacked sandstone bodies lead to separate but potentially leaky reservoir compartments and vertically stacked sandstone bodies favor more isolated reservoir compartments a high potential for reserve growth through the identification of untapped poorly drained and bypassed gas reservoir compartments exists in each of these fields differences in reservoir architecture also must be taken into account as part of exploitation strategies

acid neutralization mechanisms and metal release in mine tailings a laboratory column experiment mining and milling of base metal ore deposits can result in the release of metals to the environment when sulfide minerals contained in mine tailings are exposed to oxygen and water they oxidize and dissolve two principal antagonistic geochemical processes affect the migration of dissolved metals in tailings impoundments sulfide oxidation and acid neutralization this study focuses on acid neutralization reactions occurring in the saturated zone of tailings impoundments to simulate conditions prevailing in many tailings impoundments 0 1 mol l sulfuric acid was passed continuously through columns containing fresh unoxidized tailings collected at kidd creek metallurgical site the results of this column experiment represent a detailed temporal observation of ph eh and metal concentrations the results are consistent with previous field observations which suggest that a series of mineral dissolution precipitation reactions control ph and metal mobility typically the series consists of carbonate minerals al and fe iii hydroxides and aluminosilicates in the case of kidd creek tailings the dissolution series consists of ankerite dolomite siderite gibbsite and aluminosilicates in the column experiment three distinct ph plateaus were observed 5 7 4 0 and 1 3 the releases of trace elements such as cd co cr cu li ni pb v and zn were observed to be related to the ph buffering zones high concentrations of zn ni and co were observed at the first ph plateau ph 5 7 whereas cd cr pb as v and al were released as the ph of the pore water decreased to 4 0 or less

prediction of deep reservoir quality using early diagenetic process models in the jurassic norphlet formation gulf of mexico we have developed process based models for early grain coats and their impact on deep reservoir quality in the jurassic eolian norphlet formation alabama with implications for exploration and development in other conventional and tight gas continental reservoirs the norphlet a major gas reservoir to depths of 21 800 ft 6645 m and temperatures of 419f 215c displays contrasting intervals of high and low reservoir quality within compositionally similar cross bedded eolian sands study results show that grain coats formed soon after deposition are responsible for differences in deep norphlet porosity of up to 20 and permeability up to 200 md three types of grain coats were identified in norphlet dune sands each formed in a different part of a shallow groundwater system and each with distinctive impact on deep reservoir quality diagenetic chlorite coats formed where dunes subsided into shallow hypersaline groundwater preserve good deep porosity to 20 and permeability to 200 md continuous tangential illitic coats formed in the vadose zone of stabilized dunes exposed to periodic fresh water influx preserve good deep porosity to 15 associated with poor permeability 1 md due to linked formation of later high temperature diagenetic illite discontinuous grain coats formed in active dunes where grains were abraded by eolian transport are associated at depth with tight zones of pervasive quartz cement low porosity 8 and low permeability 1 md these concepts plus data from 60 wells were used to derive bay wide predictive tight and porous zone isopachs that can be used for well placement geologic models and field development

factors influencing the deposit geometry of experimental turbidity currents implications for sand body architecture in confined basins two sets of scaled laboratory experiments were performed to examine the effect of flow volume flow density and grain size distribution on the transport efficiency of turbidity currents the experiments employed two sediment analogues ballotini and silica flour intended to model medium to coarse grained sand and mud respectively in the first set of experiments each parameter was varied to examine its effect upon deposit geometry increases in the initial flow density volume and proportion of fines had the effect of increas ing the amount of sediment that was transferred to the floor of the experimental tank by the turbidity currents increase of each of these parameters has a characteristic effect on the three dimensional of the deposit the deposits of large volume flows are elongate and those of fines rich flows are broad increase of flow density increases the initial potential energy of the flow thus increasing the runout distance increase of the initial density beyond a sediment concentration of 13 by mass results however in a reverse of the geometrical trend of deposit elongation possibly because of turbulence suppression at high densities increase of flow volume also increases the initial potential energy and reduces the rate of velocity decrease due to gravitational spreading increase in the proportion of fines leads to main tenance of negative buoyancy as the fine fraction remains suspended until the flow has virtually come to rest it also decreases the settling velocity of the coarser fraction and thus delays its sedimentation the second set of experiments was performed to investigate the influence of flow efficiency on the interaction of turbidity currents with topography a single arcuate obstacle was placed in the path of the flows in successive experiments flow efficiency was increased by progressively increasing the proportion of fines silica flour both the proportion of sediment reaching the obstructing topography and the proportion of it able to surmount the topography increased as flow efficiency increased thus flow effi ciency may determine whether or not an enclosed basin hosts deposits whose geometry has been affected by the confinement and may also determine the relative effectiveness of the topography in confining inbound turbidity currents and thus trapping their sediment load

a review of human and natural changes in maya lowland wetlands over the holocene abstract in the maya lowlands of mexico belize and guatemala two main types of wetlands have played important roles in human history bajos or intermittently wet environments of the upland interior yucatan and perennial wetlands of the coastal plains many of the most important maya sites encircle the bajos though our growing evidence for human wetland interactions is still sparse the deposits of these wetlands record two main eras of slope instability and wetland aggradation the pleistocene holocene transition as rainfall increased and forests eclipsed savannas and the maya preclassic to classic as deforestation land use intensity and drying increased the ancient maya adapted with terraces around these bajo margins but retracted in the late preclassic in some areas the perennial wetlands of the coastal plains have different histories and the first conceptual model of human wetland interaction described intensive wetland agriculture in the preclassic through classic based on raised fields and canals but a second model arose that interpreted the wetland stratigraphy and canals as more indicative of natural aggradation by accelerated erosion and gypsum precipitation that buried archaic and preclassic fields and there was little classic era use we present new data on a third and fourth model in this study the third is a hybrid of the models one and two including the archaic to preclassic aggradation of the second model and the first model s classic period fields and canals as piecemeal attempts by the maya to adapt to these and other environmental changes the fourth conceptual model describes a very late terminal classic preplanned project on a floodplain these wetland fields were short lived aggraded rapidly but with some reoccupation in the postclassic all of these new models display the burgeoning evidence for intricate maya interactions with wetlands and the diversity of evidence from the relatively few studies underscores the infancy of our understanding of maya interaction with tropical wetlands

distribution and origin of hybrid beds in sand rich submarine fans of the tanqua depocentre karoo basin south africa abstract this study documents the stratigraphic and palaeogeographic distribution of hybrid event beds that comprise both debris flow cohesive and turbidity current non cohesive deposits this is the first study of such beds in a submarine fan system to combine outcrop and research borehole control and uses a dataset from the skoorsteenberg formation of the tanqua depocentre in the karoo basin south africa three types of 0 1 1 0 m thick hybrid beds are observed which have a basal weakly graded fine grained sandstone turbidite division overlain by a division of variable composition that can comprise 1 poorly sorted carbonaceous rich material supported by a mud rich and micaceous sand matrix 2 poorly sorted mudstone clasts in a mud rich sand silt matrix or 3 gravel grade rounded mudstone clasts in a well sorted mud poor sandstone matrix these upper divisions are interpreted respectively as 1 the deposit of a debris flow most likely derived from shelf edge collapse 2 the deposit of a debris flow most likely developed through flow transformation from turbidity current that eroded a muddy substrate and 3 from a turbidity current with mudstone clasts transported towards the rear of the flow all three hybrid bed types are found concentrated at the fringes of lobes that were deposited during fan initiation and growth the basinward stepping of successive lobes means that the hybrid beds are concentrated at the base of stratigraphic successions in medial and distal fan settings hybrid beds are absent in proximal fan positions and rare and thin in landward stepping lobes deposited during fan retreat this distribution is interpreted to reflect the enhanced amounts of erosion and availability of mud along the transport route during early lowstands of sea level therefore hybrid beds can be used to indicate a fan fringe setting infer lobe stacking patterns and have a sequence stratigraphic significance

sequestration of atmospheric co2 in chrysotile mine tailings of the woodsreef asbestos mine australia quantitative mineralogy isotopic fingerprinting and carbonation rates since closure of the woodsreef asbestos mine located in the great serpentinite belt gsb new south wales australia extensive carbonate rich crusts have formed by recessive weathering of fine grained material on the surface of the tailings pile a relationship exists between the mode of carbonate occurrence the mineralogy and the isotopic fingerprint of carbonates from the tailings pile vertical carbonate crusts covering most of the tailings predominantly consist of the hydrated mg carbonate hydromagnesite mg5 co3 4 oh 2 4h2o which has precipitated from evaporating meteoric waters incorporating atmospheric co2 as reflected in high 18o 13c and f14c signatures respectively low and variable concentrations of magnesite dolomite and calcite represent bedrock carbonate which has formed during alteration of the serpentinite bedrock before mining and is characterised by moderately high 18o low 13c and f14c a signature typical for weathering derived magnesite deposits in the gsb the carbonate fraction of deep cement samples collected from 70 to 120 cm below the surface representing the bulk tailings material at depth predominantly consists of pyroaurite mg6fe2 co3 oh 16 4h2o and despite stable isotope signatures similar to bedrock contains significant radiocarbon this indicates that pyroaurite forming under different conditions as hydromagnesite may represent an additional trap for atmospheric co2 in the woodsreef mine tailings the distribution of carbonates and quartz together with the absence of isotopic mixing trends between bedrock carbonate and atmospheric derived carbonate strongly indicates that dissolution and re precipitation of bedrock carbonate is not a dominant process in the woodsreef tailings the cations for carbonate formation are instead derived from the dissolution of serpentine minerals lizardite and chrysotile and brucite the internal standard method and the reference intensity method have been used with x ray diffraction data to estimate the abundance of the two major carbonate minerals hydromagnesite and pyroaurite respectively considering the formation of hydromagnesite on the outer surface of the tailings pile alone or together with formation of pyroaurite within the tailings pile we conclude that between 1400 and 70 000 t of atmospheric co2 have been sequestered in the mine tailings since closure of the mine 29 a ago carbonation rates of 27 g c m 2 y 1 and 1330 g c m 2 y 1 are significantly higher than background rates of co2 uptake by chemical weathering and demonstrate the potential of passive carbonation of mine tailings as a cost and energy effective alternative for storage of co2 in carbonate minerals

the intercept is a poor estimate of a calibrated radiocarbon age intercept based methods of generating a point estimate of a calibrated radiocarbon date are very popular but exhibit undesirable behaviour they are highly sensitive to the mean of the radiocarbon date and to adjustments of the calibration curve other methods give more stable results the weighted average of the probability distribution function is recommended as the best central point estimate but more consideration should be given to using the full probability distribution rather than a point estimate in developing age depth models

evolution of a turbiditic foreland basin and analogy with an accretionary prism example of the eocene south pyrenean basin the south pyrenean tertiary basin was an east west trending foreland trough which developed from early eocene to miocene times in a north south trending compressive regime a turbiditic series of lower and middle eocene age hecho group enables us to define the typical features of the tectono sedimentary evolution of the basin 1 slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders 2 the southern basin border evidenced by the onlap of the turbidites onto slope and shelf deposits migrated progressively southwards in time and 3 the deformation pattern is characterized in the meso cenozoic sediments by a complex thrust fold system of thin skinned tectonics style its specific geometry and kinematics were influenced by the pre deformation geometry onlap this thrust fold system is related to south directed basement nappes and its front advanced progressively southwards in time from this data we infer an evolutionary model for this highly mobile basin it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south directed crustal accretionary prism as the nappes advanced the basin migrated progressively southwards in the foreland direction as for the actual basin evolution many analogies with accretionary prism trench systems of active margins exist

the effect of ductile lithic sand grains and quartz cement on porosity and permeability in oligocene and lower miocene clastics south china sea prediction of reservoir quality ductile clay rich sand grains control porosity and permeability in the fluvio deltaic oligocene and lower miocene sandstones of the south china sea ductile grains account for between approximately 5 and 50 of the original sand grain population there is a pronounced loss of porosity with increasing burial depth in the basin at depths of less than 3000 m this is due solely to ductile grain compaction where the rate of porosity loss with depth increases with increasing ductile grain content at depths greater than 3000 m the steep porosity loss with depth is due to combined ductile grain compaction and quartz cementation the amount of quartz cement increases with increasing burial depth however cleaner sandstones tend to have greater amounts of quartz cement at any given depth below 3000 m this leads to convergence of porosity evolution for the clean and ductile rich sandstones below 3000 m there is a rapid loss of permeability with decreasing porosity because compaction of ductile grains smears them between rigid quartzose grains leading to blocked pore throats a consequence of this process is that the lowest permeabilities are found in sandstones with the highest ductile grain contents quartz cement does not have a clear and discernible control on permeability the pronounced loss of porosity with increasing depth and permeability with decreasing porosity leads to low permeability at relatively shallow burial depths reservoir quality is thus controlled by the nature of the primary sand and depth of burial the sediment supply system led to systematic changes in ductile grain content across the basin with ductile content increasing into the more distal part of the sediment system the consequence is that depth of economic basement in terms of porosity or permeability can be predicted as a function of ductile grain content and burial depth for prospects across the basin

spatial variability in depositional reservoir quality of deep water channel fill and lobe deposits abstract initial porosity and permeability in deep water systems are controlled by primary sedimentary texture and mineralogy therefore understanding the sedimentary processes that control changes in primary texture is critical for improved reservoir quality predictions a well constrained exhumed submarine lobe in the jaca basin and a submarine channel fill element in the ainsa basin northern spain were studied to characterize the depositional reservoir quality in axial to marginal fringe positions construction of architectural panels and strategic sampling enabled analysis of the spatial changes in textural properties and their relationship to reservoir quality distribution samples were analyzed in thin section to establish how depositional processes inferred from outcrop observations affect textural properties results show that high density turbidites are concentrated in lobe and channel axis positions and exhibit good depositional reservoir quality lobe off axis deposits contain high and low density turbidites and have moderate depositional reservoir quality conversely low density turbidites dominate lobe fringe and channel margin positions and have relatively poor depositional reservoir quality there is a sharp decrease in depositional reservoir quality between the lobe off axis and lobe fringe due to 1 an abrupt increase in matrix content 2 an abrupt decrease in sandstone amalgamation and 3 a decrease in grain size there is an abrupt increase in depositional reservoir quality from channel margin to channel axis corresponding to 1 an increase in total sandstone thickness and amalgamation 2 an increase in grain size 3 a decrease in matrix content rates of change of key properties are up to two orders of magnitude greater between channel fill sub environments compared to lobe sub environments spatial variability in properties of discrete architectural elements and rates of changes provides input to reservoir models during exploration appraisal and development phases of hydrocarbon fields

compaction of lithic sands experimental results and applications compaction experiments showed that the degree of physical compaction of a lithic sand is related to the amount and type of lithic material present these experiments produced a product that is texturally indistinguishable from natural lithic sandstones generally sedimentary lithic fragments are more ductile than metamorphic lithic fragments volcanic lithic fragments when altered to phyllosilicate minerals by weathering or diagenesis are extremely ductile mineralogy and intragranular microporosity influence ductility ratios based on weight percent of soft ductile minerals clay and micas to hard brittle minerals quartz and feldspar within the lithic fragments provides a good indication of ductility a ratio greater than 1 indicates the lithic material will be h ghly ductile microporous lithic fragments are more ductile than dense lithic fragments physical compaction models were developed based on experimental data from well sorted lithic sandstones for which the percentage of preserved porosities were functions of the effective stress the type of lithic material and the quantity of lithic material these models are derived from laboratory sandstones with at least 25 lithic grains in the following categories moderately ductile metamorphic lithic fragments highly ductile shale lithic fragments and extremely ductile altered volcanic lithic fragments application of the compaction models of the experimental compaction techniques to modern subsurface sand samples or outcrop equivalents can provide valuable estimates of the preserved porosities i e reservoir potential for lithic sandstones that may be exploratory objecti es in frontier basins examples using the models and experimental compaction techniques for exploration are given experimental data showed that precompaction cement and overpressure may be beneficial to porosity preservation an early formed partial cement can retard compaction and preserve porosity by stabilizing the sand pack a later cement does not have this beneficial effect overpressure when developed early retards compaction by reducing the effective stress of course a late developing overpressure is not effective at preserving porosity because compaction is an irreversible process

influence of depositional sand quality and diagenesis on porosity and permeability examples from brent group reservoirs northern north sea abstract multivariate statistical analysis was applied to examine correlations between reservoir quality and petrology in two data sets from the middle jurassic brent group one of the data sets is from relatively shallow depth and has been little affected by chemical diagenesis statfjord nord and ost fields 2 3 2 6 km below the sea floor while the second data set is from a more deeply buried reservoir having an advanced degree of diagenesis huldra field 3 6 3 9 km much of the total variation in porosity and permeability within each data set 0 02 md to 7 d in both sets can be accounted for by laboratory measurements of parameters mainly related to depositional sand quality including shaliness represented by bulk rock alumina silica ratio early carbonate cement feldspar co tent and grain size despite major differences in the proportions of different sedimentary facies in the two data sets they have similar ranges of depositional sand quality and therefore probably had similar reservoir quality early in their burial history deeper burial diagenesis at huldra field has shifted the average of both porosity and permeability to lower values and produced a bimodal permeability distribution apparently reflecting preferential preservation of permeability in the cleaner sandstones on the basis of these examples we outline an approach for unmixing the diagenetic and lithologic components of variation in regional compilations of sandstone porosity permeability data the procedure and its consequences are illustrated using a regional compilation of core data fr m the brent group of the northern north sea

anomalously high porosity and permeability in deeply buried sandstone reservoirs origin and predictability porosity and permeability generally decrease with increasing depth thermal exposure and effective pressure however a significant number of deep 4 km approximately 13 000 ft sandstone reservoirs worldwide are characterized by anomalously high porosity and permeability anomalous porosity and permeability can be defined as being statistically higher than the porosity and permeability values occurring in typical sandstone reservoirs of a given lithology composition and texture age and burial temperature history in sandstones containing anomalously high porosities such porosities exceed the maximum porosity of the typical sandstone subpopulation major causes of anomalous porosity and permeability were identified decades ago however quantification of the effect of processes responsible for anomalous porosity and permeability and the assessment of the predictability of anomalous porosity and permeability occurrence in subsurface sandstones have rarely been addressed in published literature the focus of this article is on quantification and predictability of three major causes of anomalously high porosity 1 grain coats and grain rims 2 early emplacement of hydrocarbons and 3 shallow development of fluid overpressure grain coats and grain rims retard quartz cementation and concomitant porosity and permeability reduction by inhibiting precipitation of quartz overgrowths on detrital quartz grains currently prediction of anomalous porosity associated with grain coats and grain rims is dependent on the availability of empirical data sets in the absence of adequate empirical data sedimentologic and diagenetic models can be helpful in assessing risk due to reservoir quality such models provide a means to evaluate the effect of geologic constraints on coating occurrence and coating completeness required to preserve economically viable porosity and permeability begin page 302 in a given play or prospect these constraints include thermal history and sandstone grain size and composition the overall effect of hydrocarbon emplacement on reservoir quality is controversial it appears that at least some cements quartz and illite may continue to precipitate following emplacement of hydrocarbons into the reservoir our work indicates that integration of basin modeling with reservoir quality modeling can be used to quantify prior to drilling the potential impact of hydrocarbon emplacement on porosity and permeability the best case scenario for significant reservoir quality preservation due to fluid overpressure development is in rapidly deposited tertiary or quaternary sandstones our models suggest that significant porosity can be preserved in sandstones that have experienced continuous high fluid overpressures from shallow burial depths the models also indicate that the potential for porosity preservation is greatest in ductile grain rich sandstones because compaction tends to be the dominant control on reservoir quality in such rocks the case for significant porosity preservation associated with fluid overpressures in pre tertiary basins however is more problematic because of the complexities in the history of fluid overpressure and the greater significance of quartz cementation as a potential mechanism of porosity loss

submarine transitional flow deposits in the paleogene gulf of mexico gravity driven flows on the seafloor are the largest yet least well understood sediment transport agents on earth recent exploration wells in ultradeep basins have revealed the presence of large sandy submarine fan systems of enigmatic facies types many hundreds of kilometers from paleocoastlines these sedimentary deposits often defy conventional turbidite or debrite interpretations having a character suggestive of deposition from flows with transient turbulent laminar rheologies in the wilcox formation gulf of mexico inferred transitional flow deposits have distinctive stratigraphic stacking patterns from fine grained debrites to coarser grained turbidites the vertical sequence of beds is here inferred to reflect the longitudinal bed distribution in response to lobe progradation and demonstrates a transition from well mixed turbulent flow to progressively more rheologically stratified flow and eventually to fully laminar flow the progressive development of internal rheological boundaries resulted in a high concentration but fluidal basal layer and an upper quasi laminar layer with an overriding sheared dilute turbidity current the long runout of the flows is linked to their high silt and clay content it is most likely flow expansion at the channel lobe transition that drives flow transformation this process based model may be applicable to many deep water settings and provides a framework within which to interpret the stratigraphic and spatial distribution of these complex deposits

the mineral and aqueous phase evolution of sulfur and nickel with weathering of pyrrhotite in a low sulfide granitic waste rock abstract the release of s and metals from the weathering of waste rock pyrrhotite fe 1 x s is affected by oxidation pathways the presence and concentration of fe substitution metals e g ni and fe oxyhydr oxide products a 4c monoclinic pyrrhotite fe7s8 ni fe substitution of about 1 200 in a low sulfide waste rock was weathered in the laboratory and at a field site to identify the evolution of s oxidation distribution and coordination of ni and possible adsorption of ni on secondary fe minerals mineral phase s was present in the 2 1 0 4 and 6 oxidation states prior to its release as so42 into solution the thiosulfate s2o32 pathway of sulfide oxidation was indicated by the presence of polythionates and s2o32 sulfur as s2o32 was more persistent than sulfite so32 prior to oxidation to so42 the release of ni during the oxidative dissolution of pyrrhotite was influenced by its distribution in the grain diffuse throughout the grain solid solution mineral or concentrated in exsolved pentlandite fe ni 9s8 lamellae within the pyrrhotite with the oxidation of s ni coordination changed from bonding with reduced s species to bonding with oxygen prior to its release with so42 sulfur as so42 typically stayed in solution with release from the pyrrhotite but the solubility of released ni was dependent on leachate ph a near neutral ph induced the adsorption of ni onto fe oxyhydr oxides which formed during oxidation of the pyrrhotite in some grains ni was found concentrated in fe distal precipitates as opposed to the closer alteration layers zones of the sulfide grain subsequent dissolution of the fe oxyhydr oxides or desorption of ni with a change in ph provides a delayed release of ni into solution this improved understanding of the oxidation pathway of s coordination and release of ni and influence of fe oxyhydr oxides in the weathering of pyrrhotite will assist in determining appropriate reaction rate factors and element release rates for prediction of acid rock drainage

hybrid event beds dominated by transitional flow facies character distribution and significance in the maastrichtian springar formation north west voring basin norwegian sea hybrid event beds comprising clay poor and clay rich sandstone are abundant in maastrichtian aged sandstones of the springar formation in the north west voring basin norwegian sea this study focuses on an interval informally referred to as the lower sandstone which has been penetrated in five wells that are distributed along a 140 km downstream transect systematic variations in bed style within this stratigraphic interval are used to infer variation in flow behaviour in relatively proximal and distal settings although individual beds were not correlated the lower sandstone shows an overall reduction of total thickness bed amalgamation sand to mud ratio and grain size in distal wells turbidites dominated by clay poor sandstone are at their most common in relatively proximal wells whereas hybrid event beds are at their most common in distal wells hybrid event beds typically comprise a basal clay poor sandstone non stratified or stratified overlain by banded sandstone with clay rich non stratified sandstone at the bed top the dominant type of clay poor sandstone at the base of these beds varies spatially non stratified sandstone is thickest and most common proximally whereas stratified sandstones become dominant in distal wells stratified and banded sandstone record progressive deposition of the hybrid event bed thus the facies succession within hybrid event beds records the longitudinal heterogeneity of flow behaviour within the depositional boundary layer this layer changed from non cohesive at the front through a region of transitional behaviour fluctuating non cohesive and cohesive flow to cohesive behaviour at the rear further spatial variation in the dominant type of clay poor sandstone at the bed base suggests that the front of the flow remained non cohesive and evolved from high concentration and turbulence suppressed to increasingly turbulent flow this is thought to occur in response to deposition and declining sediment fall out this research may be applicable to other hybrid event bed prone systems and emphasises the dynamic nature of hybrid flows this article is protected by copyright all rights reserved

tb or not tb banding in turbidite sandstones recognition and interpretation of sedimentary structures is fundamental to understanding sedimentary processes banded sandstones are an enigmatic sedimentary facies comprising alternating mud rich as matrix and or mud clasts and cleaner sand layers the juxtaposition of hydrodynamically different grain sizes contradicts established models of cleaner sand bedform development here outcrop subsurface core and petrographic data from three deep water systems with well constrained paleogeographic contexts are used to describe the range of sedimentary textures bedform morphologies and facies associations and to quantify the mud content of banding banding can occur in any part of a bed base middle or top but it typically overlies a structureless basal sandstone or mud clast conglomerate lag and is overlain by clean parallel laminated sandstone and or ripple cross lamination banding morphology ranges from sub parallel to bedforms that comprise low angle laminae with discontinuous lenses of mudstone or asymmetric bedforms comprising steeply dipping foresets that transition downstream into low amplitude bedwaves or steeply dipping ripple like bedforms with heterolithic foresets this style of banding is interpreted as a range of bedforms that form progressively in the upper stage plane bed flow regime via tractional reworking beneath mud laden transitional plug flows the balance of cohesive and turbulent forces and the rate of flow deceleration aggradation rate govern the style of deposit banded sandstones and linked debrites are rarely found juxtaposed together in the same bed because they are distributed preferentially in proximal and distal settings respectively understanding the origins of banding in turbidite sandstones the conditions under which it forms and its distribution across deep water systems and relationship to linked debrites is important for it to be used effectively as a tool to interpret the geological record

mobilization and attenuation of heavy metals within a nickel mine tailings impoundment near sudbury ontario canada the oxidation and the subsequent dissolution of sulfide minerals within the copper cliff tailings area have led to the release of heavy metals such as fe ni and co to the tailings pore water dissolved concentrations in excess of 10 g l fe and 2 2 g l ni have been detected within the shallow pore water of the tailings with increasing depth these concentrations decrease to or near analytical detection limits geochemical modelling of the pore water chemistry suggests that ph buffering reactions are occurring within the shallow oxidized zones and that secondary phases are precipitating at or near the underlying hardpan and transition zones mineralogical study of the tailings confirmed the presence of goethite jarosite gypsum native sulfur and a vermiculite type clay mineral goethite jarosite and native sulfur form alteration rims and pseudo morphs of the sulfide minerals interstitial cements composed of goethite jarosite and gypsum locally bind the tailings particles forming hardpan layers microprobe analyses of the goethite indicate that it contains up to 0 6 weight ni suggesting that the goethite is a repository for ni other sinks detected for heavy metals include jarosite and a vemiculite type clay mineral which locally contains up to 1 6 weight ni to estimate the mass and distribution of heavy metals associated with the secondary phases within the shallow tailings a series of chemical extractions was completed the experimental design permitted four fractions of the tailings to be evaluated independently these four fractions consisted of a water soluble an acid leachable and a reducible fraction as well as the whole rock total twenty five percent of the total mass of heavy metals was removed in the acid leaching experiments and 100 of the same components were removed in the reduction experiments the data suggest that precipitation coprecipitation reactions are providing an effective sink for most of the heavy metals released by sulfide mineral oxidation in light of these results potential decommissioning strategies should be evaluated with the recognition that changing the geochemical conditions may alter the stability of the secondary phases within the shallow tailings

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

arenite petrography in sequence stratigraphy stratigraphic boundary surfaces and internal anatomy of unconformity bounded units may be deciphered by using properly conceived petrography that identifies compositional spatial and temporal characteristics of sand grains discussion of two case studies of synorogenic deep marine successions indicates the potential of this method when intrabasinal source areas are present relative sea level changes can exert direct influence on the intrabasinal extrabasinal grain budget in this case genetically significant unconformity bounded units are not only characterized by their internal facies architecture but also by internal organization in petrosomes as it is for biozones in biostratigraphy when intrabasinal source areas are narrow or absent relative sea level changes only control the timing of the record in deep sea sands of tectonic modifications in hinterland sources in this case unconformity bounded sequences may be fingerprinted with distinctive detrital compositions these results emphasiz

the south pyrenean eocene carbonate megabreccias revisited new interpretation based on evidence from the pamplona basin abstract the south pyrenean foreland basin contains numerous units of eocene carbonate megabreccias intercalated with siliciclastic turbidites and derived by resedimentation of shallow marine carbonate platforms previous studies were limited mainly to the foreland eastern part known as the jaca basin the present study from the pamplona basin a western part of the foreland trough sheds new light on the origin and regional significance of these south pyrenean eocene carbonate megabreccias specms the number of the specm units in the foreland basin is higher than previously recognized and their age is somewhat older than originally assumed the specm units appear to occur as time stratigraphic clusters which can be correlated with the relative sea level lowstands and linked with phases of tectonic activity the megabreccias were derived from a carbonate platform system hosted by the foreland basin s southern passive margin the episodic instability and mass wasting were triggered by phases of structural steepening forebulge uplift accompanied by high magnitude earthquakes with the former causing platform emergence increased load stresses and excess pore water pressure in the carbonate ramp the specm deposits were emplaced by cohesive debris flows evolving into high density turbidite currents an ideal specm unit consists of 1 an immature homogeneous debrite in the proximal part 2 a differentiated bipartite debrite and turbidite in the medial part and 3 an incomplete base missing debrite overlain by turbidite or a turbidite alone in the distal part the debrite component volumetrically predominates in the specm units and the original terms megaturbidite and seismoturbidite thus seem to be inappropriate for these deposits

a sedimentological process based approach to depositional reservoir quality of deep marine sandstones an example from the springar formation northwestern voring basin norwegian sea reservoir properties of deep marine sandstones deposited by various sediment gravity flow types in the northwestern voring basin norwegian sea are characterized using detailed sedimentological and petrographic analyses the sandstones are quartz arenites and subarkoses having similar mineralogical compositions a low degree of diagenetic modification and low to moderate volumes of quartz cement up to 6 however significant textural variability is observed for the various sandstone types which were subdivided based upon their interpreted processes of deposition in the studied wells there is a predominance of turbidites deposited by high density turbidity currents hdts and a range of hybrid event beds hebs hdts are coarser grained and contain less detrital clay than the various hebs in addition the dominant grain size of hebs decreases down the depositional profile whilst the content of detrital clay increases porosities of the various bed types span the same interval but overall the hdts and proximal hebs have a higher proportion of samples with porosities higher than 20 compared to distal hebs permeabilities in contrast are significantly different with the hdts having permeabilities approximately two orders of magnitude higher than clay rich hebs a comparison of the observed variability in composition and textural parameters with porosity and permeability indicates that sedimentological flow processes control the depositional reservoir quality of deep marine sandstones understanding these processes therefore enhances our ability to predict distribution of reservoir quality in deep marine systems

spatial variations in the composition of turbidites due to hydrodynamic fractionation 1 this study uses measurements from physical experiments to document turbidity currents which are density currents composed of suspended sediment and water to be effective at hydrodynamically fractionating minerals on the basis of grain density and grain shape alone resulting in large scale spatial variations in the composition of their deposits while grain composition varies spatially the population sampled at any one location is hydrodynamically equivalent spatial variations in composition of the deposits are modeled using exponential decay functions which are based on initial concentration of grain types and their respective differences in settling velocity we further discuss implications of this process for addressing practical geophysical problems in which mineralogical distributions are important such as provenance and geochronology studies subsurface imaging and predicting bulk properties of subsurface reservoirs

impact of sequence stratigraphy depositional facies and diagenesis on reservoir quality a case study on the pennsylvanian taiyuan sandstones northeastern ordos basin china abstract the pennsylvanian taiyuan formation of the shenmu field in the northeastern ordos basin of china contains tight sandstone reservoirs that have recently been commercially produced an evaluation of the reservoir quality of the taiyuan sandstones will play a critical role in the development of the field an investigation was conducted to explore possible effects of the sequence stratigraphy depositional facies and diagenetic alterations on the reservoir quality of the taiyuan sandstones based on core descriptions the examination of thin sections and core plug and scanning electron microscope analyses the taiyuan formation consists of lowstand system tracts lst transgressive system tracts tst and highstand system tracts hst the lst sandstones are principally medium to coarse grained and are interpreted to have been deposited in the dominant distributary channels of a delta plain the early tst fine to coarse grained sandstones were largely deposited in the underwater distributary channel and mouth bar of a delta front and the middle tst fine to medium grained sandstones were deposited in the shoreface to foreshore environment the hst silt to medium grained sandstones were mostly deposited in the mouth bar of a delta front and shoreface to foreshore the taiyuan sandstones which are composed of sublitharenites quartzarenites and litharenites suffered from extensive compaction that resulted in a large loss of intergranular porosity before the sandstones were further cemented severely the sandstone cements are mostly composed of illite ankerite calcite and quartz the taiyuan sandstones have a particularly low average core plug porosity of 7 41 and horizontal permeability of 0 916 md which results from that most of the pores of the sandstones are micropores and secondary pores with poor connectivity the lst dominant distributary channel early tst underwater distributary channel and proximal mouth bar and hst shoreface to foreshore sandstones with relatively coarser grain sizes mostly medium to coarse grained have relatively higher porosities and permeabilities than the sandstones with relatively finer grain size which is ascribed to a widespread early dissolution by meteor water leaching and lower content of cements within the coarser grained sandstones however the lst dominant distributary channel sandstones had undergone a more effectively early dissolution and less carbonate cementation than the tst underwater distributary channel and proximal mouth bar and hst shoreface and foreshore sandstones had which lead to the relatively best reservoir quality of the lst dominant distributary channel sandstones among the taiyuan sandstones the study revealed that the reservoir quality of the tight taiyuan sandstones was controlled by sequence stratigraphy framework depositional facies grain size and diagenetic alterations together the sequence stratigraphy framework played a key role in controlling the reservoir quality of the taiyuan sandstones by governing the depositional facies and corresponding diagenetic products while the grain size affected the reservoir quality of the sandstones by controlling the content of cement within the sandstones

3 d seismic evidence of the effects of carbonate karst collapse on overlying clastic stratigraphy and reservoir compartmentalization a multidisciplinary team composed of stratigraphers petrophysicists reservoir engineers and geophysicists studied a portion of boonsville gas field in the fort worth basin of north central texas to determine how modern geophysical geological and engineering techniques can be combined to understand the mechanisms by which fluvio deltaic depositional processes create reservoir compartmentalization in a low to moderate accommodation basin an extensive database involving well logs cores production and pressure data from more than 200 wells 26mi2 67km2 of 3 d seismic data vertical seismic profiles vsps and checkshots was assembled to support this investigation we found the most important geologic influence on stratigraphy and reservoir compartmentalization in this basin to be the existence of numerous karst collapse chimneys over the 26 mi2 67km2 area covered by the 3 d seismic grid these near vertical karst collapses originated in or near the deep ordovician age ellenburger carbonate

pre requisites processes and prediction of chlorite grain coatings in petroleum reservoirs a review of subsurface examples abstract deeply buried reservoirs containing chlorite coated quartz sand grains commonly have higher than expected porosity and permeability although prediction of such positive anomalies still remains elusive a total of 54 published examples based on information and data from 62 scientific papers was collated quantification of some of the most common parameters including depositional environment age and latitude of sand deposition effect on reservoir quality and chemical composition of chlorite is presented the dataset indicates that chlorite coats are found in sandstones deposited in a range of depositional environments but most commonly occur in delta related environments 44 with fluvial environments the second most common 19 age relationships indicate that there is an overall exploration bias in published examples with chlorite coats becoming increasingly common through time the latitude at the time of deposition of sands with chlorite coats is wide 60 n 60 s and indicates that temperate and tropical climates are important for the generation of this clay mineral chlorite can have a variable effect on reservoir quality but is typically positive iron rich chlorites occur overwhelmingly in coastal environments while mixed iron and magnesium rich chlorites are principally found in marine and terrestrial sandstones analysis of these factors suggests that hinterland geology basinal soil development and geochemical weathering and proximity to river systems are essential to the formation of chlorite precursor phases these characteristics have been combined to define situations where chlorite coats were more likely or more unlikely to form these parameters will provide insights into the formation of chlorite and to further refine predictive models for the presence or absence of chlorite coated sandstones

interaction of diamond mine waste and surface water in the canadian arctic abstract factors controlling the chemical composition of water interacting with finely crushed kimberlite have been investigated by sampling pore waters from processed kimberlite fines stored in a containment facility discharge water from the diamond recovery plant and surface water from the containment facility which acts as plant intake water were also sampled all waters sampled are ph neutral enriched in so 4 mg ca and k and low in fe pore water samples representing the most concentrated waters are characterized by the highest so 4 up to 4080 mg l 1 mg up to 870 mg l 1 and ca up to 473 mg l 1 the water discharged from the processing plant has higher concentrations of all major dissolved constituents than the intake water the dominant minerals present in the processed fines and the kimberlite ore are serpentine and olivine with small amounts of ca sulphate and fe sulphide restricted to mud xenoclasts reaction and inverse modeling suggest that much of the water rock interaction takes place within the plant and involves the dissolution of chrysotile and ca sulphate and precipitation of silica and mg carbonate evapoconcentration also appears to be a significant process affecting pore water composition in the containment facility the reaction proposed to be occurring during ore processing involves the dissolution of co 2 g and may represent an opportunity to sequester atmospheric co 2 through mineral carbonation

late holocene vegetation change in the sierra madre oriental of central mexico abstract past vegetation and climate changes reconstructed from a sediment core from laguna atezca molango mexico provide new insights into the environmental and cultural histories of the sierra madre oriental during the last 1700 yr pollen microscopic charcoal sediment chemistry loss on ignition and magnetic susceptibility indicate that three phases of human occupation deforestation and erosion ca a d 280 890 ca a d 1030 1420 and ca a d 1680 present alternate with two phases of abandonment ca a d 890 1030 and ca a d 1420 1680 forest composition of the two abandonment phases differed with cloud forest taxa liquidambar ostrya carpinus ulmus etc dominating the pollen record during the first phase and quercus and pinus pollen characterizing phase two these differences may reflect a climate change in which the second phase was drier than the first alternatively the increase in pinus and quercus may have been caused by a human induced decline in soil fertility the laguna atezca record also differs from several other mesoamerican paleoenvironmental records in that it shows no evidence of drought at the end of the classic period ca a d 900

in situ sequestration of atmospheric co2 at low temperature and surface cracking of serpentinized peridotite in mine shafts abstract the investigation of carbonate formation at low temperature during weathering of ultramafic rocks has become increasingly important as it represents an analog study for a cost efficient carbon disposal strategy here we present new insight into carbonate formation under subarctic surface conditions obtained from extensively carbonated chromite mine shafts in the feragen ultramafic body e norway carbonation proceeded by formation of mm to cm thick carbonate surface coatings on the serpentinized peridotite host rock the surface coatings consist in most cases of pure lansfordite mgco 3 5h 2 o and sometimes nesquehonite mgco 3 3h 2 o heavy o and c isotopes are strongly enriched in the carbonate coatings relative to drip water samples from the mines and water samples from subaerial ponds the major element composition of the water samples reveal that infiltrating rainwater reacts rapidly with the peridotite mainly due to brucite dissolution within the mines discharging alkaline water forms thin films on walls and ceilings that evaporate upon circulation of cold dry air in mines with only one opening the carbonation is limited to the entrance area in mines with a more efficient air circulation due to multiple entrances carbonation is found throughout the mine evaporation of the mine water results in lansfordite saturation and precipitation and is accompanied by a rayleigh type distillation effect causing enrichment of the heavy c and o isotopes in the liquid from which the carbonates precipitate formation of the carbonate coatings involved fragmentation of the underlying serpentinite substrate fragmentation proceeded by subcritical cracking i e by a combination of substrate weakening due to brucite dissolution and stress build up due to lansfordite precipitation in fractures close to the surface reaction induced fracturing represents a positive feedback mechanism as it creates additional reactive surface area during the carbonation mining operations in the area ceased in the mid 1920s indicating that the described carbonation occurs on a time scale relevant for the disposal of anthropogenic co 2

fossil grass cuticles from lacustrine sediments a review of methods applicable to the analysis of tropical african lake cores the need for alternatives to fossil pollen for the reconstruction of vegetation dominated by grasses has prompted the use of grass cuticles which lack a described method of analysis methods used to analyse sediments for palaeoecological materials allied to grass cuticles including microscopic charcoal phytoliths and plant cuticles are reviewed a simple set of methods and protocols for extracting identifying and quantifying fossil grass cuticles are presented

quantifying carbon fixation in trace minerals from processed kimberlite a comparative study of quantitative methods using x ray powder diffraction data with applications to the diavik diamond mine northwest territories canada abstract the capacity of mine waste to trap co2 is in some cases much larger than the greenhouse gas production of a mining operation in mine tailings the presence of secondary carbonate minerals that trap co2 can therefore represent substantial fixation of this greenhouse gas the abilities of three methods of quantitative phase analysis to measure trace nesquehonite mgco3 3h2o in samples of processed kimberlite have been assessed the method of reference intensity ratios rir the internal standard method and the rietveld method with x ray powder diffraction data tests on synthetic mixtures made to resemble processed kimberlite indicate that both the rir and rietveld methods can be used accurately to quantify nesquehonite to a lower limit of approximately 0 5 wt for conditions used in the laboratory below this value estimates can be made to a limit of approximately 0 1 wt using a calibration curve according to the internal standard method the rir method becomes increasingly unreliable with decreasing abundance of nesquehonite primarily as a result of an unpredictable decline in preferred orientation of crystallites for rietveld refinements structureless pattern fitting was used to account for planar disorder in lizardite by considering it as an amorphous phase rietveld refinement of data collected from specimens that were serrated to minimize preferred orientation of crystallites gives rise to systematic overestimates of refined abundances for lizardite and underestimates for other phases the resulting pattern of misestimates may be mistaken for the effect of amorphous and or nanocrystalline material in samples this effect is mitigated by collecting data from non serrated specimens which typically give relative errors on refined abundances for major and minor phases in the range of 5 20 however relative error can increase rapidly for abundances less than 5 wt nonetheless absolute errors are sufficiently small that estimates can be made for the amount of co2 stored in secondary nesquehonite using the rir method or the rietveld method for abundances 0 5 wt and a calibration curve for abundances

origin of mud in turbidites and hybrid event beds insight from ponded mudstone caps of the castagnola turbidite system north west italy the partitioning of different grain size classes in gravity flow deposits is one of the key characteristics used to infer depositional processes turbidites have relatively clean sandstones with most of their clay deposited as part of a mudstone cap or as a distal mudstone layer whereas sand bearing debrites commonly comprise mixtures of sand grains and interstitial clay hybrid event beds develop alternations of clean and dirty clay rich sandstones in varying proportions analysis of co genetic mudstone caps in terms of thickness and composition is a novel approach that can provide new insight into gravity flow depositional processes bed thickness data from the ponded castagnola system show that turbidites contain more clay overall than do hybrid event beds the castagnola system is characterized by deposits of two very different petrographic types thanks to this duality analyses of sandstone and mudstones composition allow inference of which proportion of the clay in each of the deposit types was acquired en route in combination with standard sedimentological observations the new data allow insight into the likely characteristics of their parent flows clean turbidites were deposited by lower concentration long duration erosive muddy turbidity currents which were more efficient at fractionating clay particles away from their basal layer hybrid event beds were deposited by shorter duration higher concentration less erosive sandier flows which were less efficient at clay fractionation the results are consistent with data from other turbidite systems for example marnoso arenacea the approach represents a new method to infer the controls on the degree of clay partitioning in gravity flow deposits

evidence of modern fine grained sediment accumulation in the monterey fan from measurements of the pesticide ddt and its metabolites abstract the documented presence of the pesticide ddt 1 1 1 trichloro 2 2 bis p chlorophenyl ethane and its metabolites dde 1 1 dichloro 2 2 bis p chlorophenyl ethylene and ddd 1 1 dichloro 2 2 bis p chlorophenyl ethane collectively referred to as ddt in sediments from the monterey submarine canyon monterey fan channel and monterey fan indicates that during the present sea level highstand the monterey fan has been an active depositional system the presence of ddt in marine sediment is an indication of the recent arrival of terrigenous fine grained sediment because ddt was only applied on land in california between 1944 and 1972 and is being transported to the ocean in the fine grained sediment fraction of rivers ddt was found in 81 out of 82 cores collected in water depths deeper than 3000 m in the monterey fan channel and in the monterey fan within a geographical extent of 250 km to the south and 210 km to the west of the monterey canyon head with surface concentrations averaging 6 and 3 ng g 1 in the upper and lower monterey fan respectively this is the first documentation of ddt presence in ocean sediments below 3000 m water depth worldwide the estimated total amount of ddt in the fan is consistent with the amount of ddt discharged by the salinas and pajaro rivers since ddt started being used in california suggesting that current fine grained sediment discharge from these rivers has been accumulating in the fan the ratio dde ddt an indication of the extent of ddt degradation provides a first order proxy for the relative age of the sediments ddt is found along the thalweg of the monterey fan channel as far as 215 km from the canyon head indicating recent fine grained sediment transport along the channel in contrast only dde was detected in sediments on the fan which suggests that the fan does not accumulate fine grained sediments at a constant rate

colloquium 2004 hydrogeotechnical properties of hard rock tailings from metal mines and emerging geoenvironmental disposal approaches tailings are ground rock particles from which the valuable minerals or metals have been extracted an historical overview on hard rock mines shows that since the 1930s it has become current practice to pump the tailings into storage areas circumscribed by dykes made of the tailings themselves however numerous physical and chemical stability problems were observed mainly owing to the particular hydrogeotechnical and mineralogical properties of the tailings therefore modifications to the conventional methods were proposed but these were relatively costly not always efficient and sometimes difficult to implement new management methods that improve the physical and or chemical stability have hence been developed to reduce environmental risks associated with tailings storage namely densified tailings environmental desulphurization covers built with tailings and co disposal of tailings and waste rock even if many aspects need to be optimized these approaches can be considered today as interest

the transition between sheet like lobe and basin plain turbidites in the hecho basin south central pyrenees spain genetic facies analysis based on bed by bed correlations from sheet like lobes to the basin plain in some hecho turbidite systems demonstrates that at least 50 of the flows building the sheet like lobes kept moving downcurrent to the closely related basin plain and underwent flow transformations interpreted to have resulted from interaction with topography at the basin margin s that gave rise to specific facies these facies form a new facies tract that replaces the fine grained group of turbidite facies very fine sand to mud and characterizes the basin plain beds beds in the sheet like lobes evolve downcurrent in a way that is predictable by the existing turbidite facies tract models whereas 36 of basin plain beds which account for 78 of the basin plain volume do not the latter have deposits from high density turbidity currents at their bases and typically complete basin floor coverage the new facies tract developed when the flows obliquely encountered the southern foreland margin ramp at the ramp the lower sand laden and high density part of the larger flows was deflected evolving downcurrent along the ramp trend the upper part of the flow more dilute and thicker was reflected from the foreland margin as a train of declining undular bores moving hydraulic jumps subsequent reflections generated against the flanking margins in the closed basin led to ponding which resulted in an overall sheet like stacking pattern across sheet like lobes and the basin plain and is the diagnostic feature of the distal element in the lower sand rich stages of the turbidite systems calcilutites on top of beds interpreted until now as hemipelagites show field evidence of having a turbiditic origin hemiturbidites thus forming the facies capping the new facies tract

architecture of shoreface to deep water systems in segmented rift systems evidence from the southern margin of the sogn graben northern north sea the spatial distribution of syn rift deposits and temporal evolution of sandy gravity flows in the context of rift segmentation are poorly constrained based on conventional core description well log analysis and 3d seismic interpretation this study focuses on the upper jurassic successions in the southern margin of the sogn graben northern north sea thirteen facies associations are classified in order to discuss the architecture of shoreface gravity driven submarine fans and basin plain deposits on the scale of centimeters to meters in the eastern part of the study area gamma ray log stacking patterns suggest that northeast southwest oriented shoreface successions underwent progradational to retrogradational deposition during the oxfordian age lithological description of conventional cores indicates that large submarine fan system formed by debris flow dominated channels and turbidity flow dominated lobe complexes covers a broad 22 20 km depositional area the entry of regional drainages and the location of sandy gravity flow deposits were controlled by first order rift segmentation whereas the route of submarine canyon feeder system and the orientation of submarine fan lobes were determined by second order rift segmentation thus both first order and second order rift segmentation should be considered when determining the sedimentary facies and depositional architecture of sandy gravity flow deposits in individual rift segments

accelerating mineral carbonation in ultramafic mine tailings via direct co2 reaction and heap leaching with potential for base metal enrichment and recovery accelerated carbonation of ultramafic mine tailings has the potential to offset co2 emissions produced by mining ores from cu ni platinum group element podiform chromite diamondiferous kimberlite and historical chrysotile deposits treatments such as acid leaching reaction of tailings with elevated concentrations of gaseous co2 and optimization of tailings pore water saturation have been shown to enhance co2 sequestration rates in laboratory settings the next challenge is to deploy treatment technologies on the pilot and field scale while minimizing cost energy input and adverse environmental impacts implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures here we describe column experiments designed to trial two geochemical treatments that address these criteria 1 direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation 10 co2 in n 2 and 2 repeated heap leaching of ultramafic tailings with dilute sulfuric acid in the first experiment we report rapid carbonation of brucite mg oh 2 in the presence of 10 co2 gas within tailings sampled from the woodsreef chrysotile mine new south wales australia within four weeks we observe a doubling of the amount of co2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field our simulated heap leaching experiments treated daily with 0 08 m h2so4 produce high mg leachates that have the potential to sequester 21 2 kg co2 m 2 which is approximately one to two orders of magnitude higher than the rate of passive carbonation of the wood sreef mine tailings although some nesquehonite mgco3 center dot 3h 2 o forms from these leachates most of the mg is precipitated as mg sulfate minerals instead therefore an acid other than h2so4 could be used otherwise sulfate removal would be required to maximize co2 sequestration potential from acid heap leaching treatments reactive transport modeling min3p is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years finally our synchrotron x ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals fe ni mn co cr become highly concentrated within secondary fe hydr oxide minerals at the ph neutralization horizon within our column experiments this discrete horizon migrates downward and our reactive transport models indicate it will become increasingly enriched in first row transition metals in response to continued acid leaching acid leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings waste rock or low grade ores

experiments on bidisperse constant volume gravity currents propagation and sediment deposition laboratory experiments show that the propagation and sedimentation patterns of particle laden gravity currents are strongly influenced by the size of suspended particles the main series of experiments consisted of fixed volume releases of dilute mixtures containing two sizes of silicon carbide particles 25 m and 69 m mean diameter within a 6 m flume polydisperse experiments involved mixtures of five different particle sizes and variation of the amounts of the finest and coarsest particles all variables apart from the initial relative proportions of particles were identical in the experiments the effects of mixing different proportions of fine and coarse particles is markedly non linear adding small amounts of fine sediment to a coarse grained gravity current has a much larger influence on flow velocity run out distance and sedimentation patterns than adding a small amount of coarse sediment to a fine grained gravity current the experiments show that adding small amounts of fine particles to a coarse grained current results in enhanced flow velocities because the fine sediment remains suspended and maintains an excess current density for a much longer time thus the distance to which coarse particles are transported increases substantially as the proportion of fines in the flow is increased our experiments suggest that sandy turbidity currents containing suspended fines will be much more extensive than turbidity currents composed of clean sand

qualitative and quantitative characterization of multiple factors that influence movable fluid saturation in lacustrine deep water gravity flow tight sandstones from the yanchang formation southern ordos basin china abstract fluid mobility is one of the most important factors in evaluating the potential for recovering tight oil however quantitative effects of multiple factors that influence movable fluid saturation in different pore throat combinations and their relationships with lithofacies in tight sandstones especially for lacustrine deep water gravity flow deposits remain controversial due to the strong heterogeneity and complex pore structure of tight reservoirs core samples obtained from the upper triassic yanchang formation in southern ordos basin were evaluated by using a variety of techniques including nuclear magnetic resonance nmr scanning electron microscopy sem x ray diffraction xrd pressure controlled porosimetry pcp rate controlled porosimetry rcp impregnated thin sections and helium porosity and nitrogen permeability measurements based on nmr t2 distributions under water saturated and centrifugal conditions four types of pore throat combinations are identified by using the relaxation time thresholds ts1 and ts2 from nmr large intergranular pore dominated pore throat combinations lip small intergranular pore dominated pore throat combinations sip intragranular pore dominated pore throat combinations iap and micropore dominated pore throat combinations mp among them sip is the dominant pore space favorable for fluid flow movable fluid saturation in sip pore space varies among different lithofacies the best fluid mobility commonly occurs in fine grained cross bedded sandstones sc whereas the worst fluid mobility usually appears in siltstones to very fine grained sandstones ss the quantitative effects of a total of 41 factors that influence movable fluid saturation of different pore throat combinations were investigated through the analysis of the pearson correlation matrix the results demonstrate that porosity and permeability mainly affect the movable fluid saturation in the pore space of sip and mp in addition maximum mercury intrusion saturation from pcp smax and tortuosity are the critical pore structure parameters affecting the movable fluid saturation in the pore space of sip and mp whereas the average pore throat radius ratio is the critical factor affecting the movable fluid saturation in lip pore space overall movable fluid saturation in different pore throat combinations is characterized mainly by different microscopic pore structure parameters a general pore network model for different lithofacies with different fluid mobility is established to facilitate assessment of the heterogeneity of tight sandstones and to further guide hydrocarbon exploration and development in similar lacustrine deep water depositional settings

verifying and quantifying carbon fixation in minerals from serpentine rich mine tailings using the rietveld method with x ray powder diffraction data most carbon on earth is bound within minerals and increasing the uptake of atmospheric carbon dioxide into minerals may reduce the greenhouse gas content of the atmosphere we document carbon disposal through the mineralization of mine tailings at clinton creek yukon territory and cassiar british columbia we confirm crystallographic binding of carbon in these tailings and quantify carbon dioxide uptake using quantitative phase analysis with the rietveld method for x ray powder diffraction data planar disorder in the structures of the kaolinite serpentine group minerals makes rietveld refinements of x ray powder diffraction data for serpentinites problematic using structureless pattern fitting and with the addition of a known quantity of a well crystallized material the problem of structural disorder is overcome by considering the serpentine minerals as amorphous phases we test the accuracy and precision of this refinement method using synthetic serpentine rich mine tailings of known composition estimates of the abundance of hydrated magnesium carbonates in these tailings have a precision of approximately 5 relative for mineral species present in amounts greater than 10 wt precise estimates of carbonate mineral content and crystallographically bound atmospheric co 2 are made for samples of serpentine rich tailings from clinton creek and cassiar results for mine tailings are also compared to mineralogically similar samples from a carbonate playa at atlin british columbia the potential for decomposition of metastable hydrated magnesium carbonate phases to geologically stable magnesite may represent long term stability of the products of mineral sequestration in mine tailings

multiproxy paleoecological reconstruction of prehistoric land use history in the western region of the lower rio verde valley oaxaca mexico paleoecological archives from three paleomeander sites and one archeological feature located in the lower rio verde valley oaxaca mexico are used to develop a spatial understanding of the patter

the spatial and temporal distribution of grain size breaks in turbidites grain size breaks are surfaces where abrupt changes in grain size occur vertically within deposits grain size breaks are common features in turbidites around the world including ancient and modern systems despite their widespread occurrence grain size breaks have been regarded as exceptional and not included within idealized models of turbidity current deposition this study uses ca 100 shallow sediment cores from the moroccan turbidite system to map out five turbidite beds for distances in excess of 2000 km the vertical and spatial distributions of grain size breaks within these beds are examined five different types of grain size break are found type i in proximal areas between coarse sand and finer grained structureless sand type ii in proximal areas between inversely graded sand overlain by finer sand type iii in proximal areas between sand overlain by ripple cross laminated finer sand type iv throughout the system between clean sand and mud and type v in distal areas between mud rich debrite sand and mud this article interprets types i and v as being generated by sharp vertical concentration boundaries controlled by sediment and clay concentrations within the flows whilst types ii and iii are interpreted as products of spatial temporal fluctuations in flow capacity type iv are interpreted as the product of fluid mud layers which hinder the settling of non cohesive grains and bypasses them down slope decelerating suspensions with sufficient clay will always form cohesive layers near to bed promoting the generation of type iv grain size breaks this may explain why type iv grain size breaks are widespread in all five turbidites examined and are commonplace within turbidite sequences studied elsewhere therefore type iv grain size breaks should be understood as the norm not the exception and regarded as a typical feature within turbidite beds

diagenetic alteration and its control on reservoir quality of tight sandstones in lacustrine deep water gravity ﬂow deposits a case study of the yanchang formation southern ordos basin china abstract the tight oil sandstone reservoir of the upper triassic yanchang formation is one of the main targets for hydrocarbon exploration in the ordos basin china sandstones of the upper triassic yanchang formation within lacustrine deep water gravity ow deposits are characterized by ultralow porosity ultralow permeability and complex diagenetic alterations and sedimentary lithofacies however the diagenetic alterations and their controls on the reservoir quality of the chang 6 tight sandstones remain poorly understood this study integrated a variety of techniques such as casting thin section analysis scanning electron microscopy sem back scattered electron imagery bse x ray diffraction xrd cathodoluminescence cl microscopy and fluid inclusion to investigate the lithofacies diagenetic history and diagenetic intensity and also evaluate their controls on reservoir quality the research results indicated that the chang 6 sandstones exhibit variable intensity of diagenetic alterations among the various lithofacies which leads to variable reservoir quality mechanical compaction was the most important factor reducing primary porosity sandstones of the ss lithofacies siltstone to very fine grained sandstones with graded bedding or ripple laminations showed the highest loss of primary porosity carbonate cements were commonly present in sandstones of the sc fine grained and cross bedded sandstones and sm fine grained and massive sandstones lithofacies near the sandstone mudstone bounding surface sandstones with more authigenic illite rims were able to resist compaction to some extent and were favorable to the preservation of porosity however abundant pore filling illite aggregates commonly bridged pore throats causing a significant reduction in reservoir quality feldspar dissolution porosity leads to a slight enhancement in reservoir quality intergranular pores and feldspar dissolution pores are most abundant in the sandstones away from the sandstone mudstone bounding surface of the sc lithofacies resulting in the best reservoir quality which is followed by sandstones of the sm lithofacies ultimately four evolution patterns of diagenetic alterations that formed best moderate or poor reservoir quality were summarized by linking diagenetic alterations to lithofacies the research results are conducive to the evaluation of reservoir quality and to understanding the genetic mechanisms of tight sandstones so they should facilitate hydrocarbon exploration and production in similar lacustrine deep water gravity ow reservoirs

mine drainage from the weathering of sulfide minerals and magnetite pyrite and pyrrhotite are the principal minerals that generate acid drainage in mine wastes low ph conditions derived from fe sulfide oxidation result in the mobilization of contaminant metals such as zn cd ni and cr and metalloids such as as which are of environmental concern this paper uses data from detailed mineralogical and geochemical studies conducted at two canadian tailings impoundments to examine the mineralogical changes that pyrite pyrrhotite sphalerite and magnetite undergo during and after sulfide oxidation and the subsequent release and attenuation of associated trace elements the stability of sphalerite in tailings impoundments generally is greater than that of pyrrhotite but less than pyrite dissolved ni and co derived from fe sulfides and to a lesser extent dissolved zn and cd from sphalerite are commonly attenuated by early formed fe oxyhydroxides as oxidation progresses a recycling occurs due to continued leaching from low ph pore waters and because the crystallinity of fe oxyhydroxides gradually increases which decreases their sorptive capacity unlike many other elements such as cu pb and cr which form secondary minerals or remain incorporated into mature fe oxyhydroxides zn and ni become mobile magnetite which is a potential source of cr is relatively stable except under extremely low ph conditions a conceptual model for the sequence of events that typically occurs in an oxidizing tailings impoundment is developed outlining the progressive oxidation of a unit of mine waste containing a mixed assemblage of pyrrhotite and pyrite

a rock glacier pond system nw italian alps soil and sediment properties geochemistry and trace metal bioavailability abstract rock glacier sediment transfer and ice melting can impact surface waters located downstream however there is a lack of knowledge on the influence of rock glacier dynamics on the geochemical hydrochemical and ecological characteristics of adjacent impounded surface waters in the col d olen area long term ecological research site nw italian alps an intact rock glacier terminates into a pond and solute enriched waters originating from the rock glacier flow into the pond through a subsurface hydrological window in this study we performed geophysical and ground surface temperature measurements moreover we sampled soils and sediments in different compartments of the investigated rock glacier pond system and we further sampled benthic invertebrates in the pond cold ground thermal regime ground ice presence and coarse debris cover on the rock glacier together with its lithology serpentinites influence the rock glacier geochemistry and ecology with respect to surrounding areas pond geochemistry is affected by transfer of trace metal enriched fine grained debris and meltwaters from the rock glacier enhanced bioavailability of serpentinite associated trace metals was proved with concentrations of ni and cr in benthic invertebrates up to 384 and 110 mg kg 1 d w respectively potentially exerting toxic effects on pond biota the advancing movement of the rock glacier not only has delivered sediments to the pond but it has progressively filled the valley depression where the pond is located creating a dam that could have modified the level of impounded water this process likely constituted a sediment trap in which serpentinitic rock glacier sediments could be deposited at the pond bottom with related geochemical and ecological implications this study illustrates the importance of rock glaciers in influencing the characteristics of downstream freshwater bodies and highlights the need to improve our knowledge about climate change related impacts of rock glacier dynamics on alpine headwaters