electrical resistivity investigation of the arsenic affected alluvial aquifers in west bengal india usefulness in identifying the areas of low and high groundwater arsenic this study aims at finding out possible relation between lithology and spatial pattern of dissolved arsenic as in groundwater around chakdaha municipality west bengal india satellite image coupled with electrical resistivity survey and borehole drilling helps to delineate surface and sub surface lithological framework of the as affected alluvial aquifers the satellite imagery demonstrate that the high as area are presumably under active flood plain environment low lying areas that constantly receive organics due to periodic flooding thick low resistive fine grained layer was observed at the top around the high as areas which however not found in low as areas the result suggests that hydraulic properties of the surface sub surface soil sediment have an important control on the fate and transport of as in the aquifer this study demonstrates that electrical resistivity tools can be effectively used for the reconnaissance survey in characterizing the plausible lithological framework of an alluvial aquifer containing as

petrographic features and thermal behaviour of the historically known pietra ollare from the italian central alps valchiavenna and valmalenco

spectrum of pore types and networks in mudrocks and a descriptive classification for matrix related mudrock pores matrix related pore networks in mudrocks are composed of nanometer to micrometer size pores in shale gas systems these pores along with natural fractures form the flow path permeability network that allows flow of gas from the mudrock to induced fractures during production a pore classification consisting of three major matrix related pore types is presented that can be used to quantify matrix related pores and relate them to pore networks two pore types are associated with the mineral matrix the third pore type is associated with organic matter om fracture pores are not controlled by individual matrix particles and are not part of this classification pores associated with mineral particles can be subdivided into interparticle interp pores that are found between particles and crystals and intraparticle intrap pores that are located within particles organic matter pores are intrap pores located within om interparticle mineral pores have a higher probability of being part of an effective pore network than intrap mineral pores because they are more likely to be interconnected although they are intrap om pores are also likely to be part of an interconnected network because of the interconnectivity of om particles in unlithifed near surface muds pores consist of interp and intrap pores and as the muds are buried they compact and lithify during the compaction process a large number of interp and intrap pores are destroyed especially in ductile grain rich muds compaction can decrease the pore volume up to 88 by several kilometers of burial at the onset of hydrocarbon thermal maturation om pores are created in kerogen at depth dissolution of chemically unstable particles can create additional moldic intrap pores

drav model and its application in assessing groundwater vulnerability in arid area a case study of pore phreatic water in tarim basin xinjiang northwest china according to the characteristics of groundwater in arid area this paper proposes drav model for groundwater vulnerability assessment where d is groundwater depth r is the net recharge of aquifer a is the aquifer characteristics and v is the lithology of vadose zone as a case study the paper assesses the vulnerability of pore phreatic water in tarim basin of xinjiang china by using the drav model the results indicate that the areas of phreatic water with vulnerability index ranges of 2 4 4 6 6 8 and 8 accounting for 10 1 80 4 9 2 and 0 2 of the total plain area of the tarim basin respectively and the areas with the latter two vulnerability ranges 6 8 and 8 are mainly located in the irrigation districts with thin soil layer 20 30 cm thick surface soil of vadose zone mainly with underlying sandy gravel and with silty and fine sand layer such vadose zone generally lacks sandy loam and clayey soil and has larger recharge by infiltration of irrigation water

hydrochemical and isotopic characteristics of groundwater in the yanqi basin of xinjiang province northwest china in this study hydrochemical and isotope investigations were conducted in the yanqi basin to determine the chemical composition and to gain insight into the groundwater recharge process in the yanqi basin it mainly used hydrochemistry environmental isotopes and a series of comprehensive data interpretation e g statistics ionic ratios and piper diagram to obtain a better understanding of the functioning of the system the following hydrochemical processes were identified as the main factors controlling the water quality of the groundwater system weathering of silicate minerals dissolution ion exchange and to a lesser extent evaporation which seemed to be more pronounced down gradient of the flow system as groundwater flows from the recharge to discharge areas chemical patterns evolve in the order of ca2 hco3 ca2 mg2 hco3 to ca2 mg2 cl so4 2 na k cl so4 2 and na cl according to lithology the environmental isotope 18o 2h 3h measurements further revealed that precipitation was the main recharge source for the groundwater system some local values indicated high levels of evaporation tritium and cfc analysis were used to estimate the ages of the different groundwater the tritium values of the groundwater samples varied from 2 82 to 29 7 tu the age of the groundwater at depths of 120 m is about 30 50 years cfc values obtained for six samples to determine groundwater age the age of the groundwater is about 20 50 years

specific surface area and pore size distribution in clays and shales one of the biggest challenges in estimating the elastic transport and storage properties of shales has been a lack of understanding of their complete pore structure the shale matrix is predominantly composed of micropores pores less than 2 nm diameter and mesopores pores with 2 50 nm diameter these small pores in the shale matrix are mainly associated with clay minerals and organic matter and comprehending the controls of these clays and organic matter on the pore size distribution is critical to understand the shale pore network historically mercury intrusion techniques are used for pore size analysis of conventional reservoirs however for unconventional shale reservoirs very high pressures 414 mpa 60 000 psi would be required for mercury to access the full pore structure which has potential pitfalls current instrumental limitations do not allow reliable measurement of significant portions of the total pore volume in shales nitrogen gas adsorption techniques can be used to characterize materials dominated by micro and mesopores 2 50 nm a limitation of this technique is that it fails to measure large pores diameter 200 nm we use a nitrogen gas adsorption technique to study the micro and mesopores in shales and clays and compare the results from conventional mercury porosimetry techniques our results on pure clay minerals and natural shales show that i they have a multiscale pore structure at different dimensions ii fine mesopores with a characteristic 3 nm pore size obtained with n2 gas adsorption are associated with an illite smectite group of clays but not with kaolinite iii compaction results in a decrease of pore volume and a reduction of pore size in the inter aggregate macropores of the illitesmectite clays while the fine intra tachoid mesopores are shielded from compaction iv for natural shales mineralogy controls the pore size distributions for shales and the presence of micropores and fine mesopores in natural shales can be correlated with the dominance of the illite smectite type of clays in the rock our assessment of incompressible 3 nm sized pores associated with illite smectite clays provides an important building block for their mineral modulus

heterogeneity of the lower silurian longmaxi marine shale in the southeast sichuan basin of china this study characterizes the vertical heterogeneity of the lower silurian longmaxi marine shale in the southeast sichuan basin based on core description thin sections observation geological chemistry data interrogation and qemscan image analysis lithofacies associations mineralogy graptolite species occurrence rock fabrics as well as toc total organic carbon and gas content change noticeably and regularly in the lower silurian longmaxi marine shale within sequence stratigraphic framework lithofacies associations mainly include in situ graptolite rich and siliceous shale in the transgressive systems tract tst micro offsite graptolite rich shale and shale interbedded with siltstone laminaes in the early highstand systems tract ehst and micro offsite graptolite rich and carbonate rich shale in the late highstand systems tract lhst the tst has a greater abundance of diplogratus than ehst and lhst and has a lesser level of monograptus which is conversely higher in the ehst and lhst the tst shale is silica rich while the lhst shale is generally clay rich the ehst shale is more balanced in its silica and clay content than the tst and lhst are the sedimentary structure and fabric of shale shows that shale is homogenous in the tst with laminaes well developed in the ehst but decreasing in the lhst toc and gas content are highest in the tst and decrease upward the tst with high toc high gas content high brittle minerals silica rich and anoxic suboxic to dysoxic sedimentary environment is the most potential shale gas target interval in the study area our research also shows that the toc mainly controls shale gas accumulation and that the redox conditions mainly control the preservation of organic matter the silica also plays a significant role in shale gas content due to its contribution to hydraulic fracturing finally the study proposes a depositional and heterogeneity model for the lower silurian longmaxi marine shale in the study area

graptolite derived organic matter in the wufeng longmaxi formations upper ordovician lower silurian of southeastern chongqing china implications for gas shale evaluation abstract the organic rich shales of the wufeng longmaxi formations ordovician silurian are one of the most important hydrocarbon source rocks and shale gas exploration targets in china graptolites are abundant in these shales but their contribution to the dispersed organic matter om has been overlooked this lack of attention could seriously affect the evaluation of om type om maturity hydrocarbon generation potential reservoir characteristics and gas content of these shales optical microscope and focused ion beam scanning electron microscope fib sem techniques were employed to describe the optical characteristics and micro nanopores of the graptolites to determine the contribution of the graptolites and to evaluate the thermal maturity of the wufeng longmaxi formations non granular graptolites which show a stronger anisotropy and higher reflectance under polarized light than the granular graptolites were primarily observed in these sediments graptolites account for 20 93 of the dispersed om in the wufeng longmaxi formations and the level of their contribution has been attributed to the radiation of graptolites at the late ordovician kaptian and the recovery of graptolites at the early silurian rhuddanian the bireflectance values of the non granular graptolites fall between 2 22 and 4 32 indicating a behavior similar to biaxial anthracitic vitrinite the equivalent vitrinite reflectance eqvro values of the sediments in the wufeng longmaxi formations calculated from the mean maximum reflectance of non granular graptolite fall in the range of 3 08 4 29 and these values have a precision that is greater than in previous studies on the wufeng longmaxi formations abundant organic pores were observed in the non granular graptolites and they are aligned parallel to the fusellar layers of the graptolites this indicates that the fusellar layers of non granular graptolites controlled the development and distribution of organic pores such abundant organic pores played a significant role in the accumulation of shale gas in the wufeng longmaxi formations of the upper yangtze platform

formation of nanoporous pyrobitumen residues during maturation of the barnett shale fort worth basin abstract hydrocarbon generation reactions occur within organic rich shales as a response to thermal maturation here we report observations on samples from the organic rich mississippian barnett shale gas system fort worth basin texas usa at varying stages of thermal maturation a multiscale characterization was achieved using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm and transmission electron microscopy tem we document the chemical evolution of the macromolecular structure of barnett shale kerogen with increasing maturity from an immature kerogen containing a significant aliphatic component and an important concentration of oxygen and sulfur containing functional groups to an overmature kerogen dominated by poorly condensed aromatic structures in addition to the presence of bitumen in samples of oil window maturity very likely genetically derived from thermally degraded kerogen the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by secondary cracking of bitumen compounds

geomaterials in cultural heritage this volume gives a broad view of the application of geoscience techniques to the study of monuments and objects from excavations and museums including their origin technique of manufacture age and conservation it reaffirms the important contribution of geosciences in the interdisciplinary approach to the study of complex materials such as minerals rocks glass metals mortar plaster slags and pottery the papers in this book cover three topics the study of pottery glass stone and mortar the application of raman spectroscopy to a wide variety of objects and the future of archaeometry interdisciplinary studies including field geology geophysics microscopy textural analysis physical methods and geochemistry are used to unlock information from the ancient materials such as the provenance of the raw materials the firing technology the ancient recipes and the alteration pathways

the importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs abstract the effect of shale composition and fabric upon pore structure and ch 4 sorption is investigated for potential shale gas reservoirs in the western canadian sedimentary basin wcsb devonian mississippian d m and jurassic shales have complex heterogeneous pore volume distributions as identified by low pressure co 2 and n 2 sorption and high pressure hg porosimetry thermally mature d m shales 1 6 2 5 vro have dubinin radushkevich d r co 2 micropore volumes ranging between 0 3 and 1 2 cc 100 g and n 2 bet surface areas of 5 31 m 2 g jurassic shales which are invariably of lower thermal maturity ranging from 0 9 to 1 3 vro than d m shales have smaller d r co 2 micropore volumes and n 2 bet surface areas typically in the range of 0 23 0 63 cc 100 g co 2 and 1 9 m 2 g n 2 high pressure ch 4 isotherms on dried and moisture equilibrated shales show a general increase of gas sorption with total organic carbon toc content methane sorption in d m shales increases with increasing toc and micropore volume indicating that microporosity associated with the organic fraction is a primary control upon ch 4 sorption sorption capacities for jurassic shales however can be in part unrelated to micropore volume the large sorbed gas capacities of organic rich jurassic shales independent of surface area imply a portion of ch 4 is stored by solution in matrix bituminite solute ch 4 is not an important contributor to gas storage in d m shales structural transformation of d m organic matter has occurred during thermal diagenesis creating and or opening up microporosity onto which gas can sorb as such d m shales sorb more ch 4 per weight percent wt toc than jurassic shales inorganic material influences modal pore size total porosity and sorption characteristics of shales clay minerals are capable of sorbing gas to their internal structure the amount of which is dependent on clay type illite and montmorillonite have co 2 micropore volumes of 0 78 and 0 79 cc 100 g n 2 bet surface areas of 25 and 30 m 2 g and sorb 2 9 and 2 1 cc g of ch 4 respectively dry basis a reflection of microporosity between irregular surfaces of clay platelets and possibly related to the size of the clay crystals themselves mercury porosimetry analyses show that total porosities are larger in clay rich shales compared to silica rich shales due to open porosity associated with the aluminosilicate fraction clay rich sediments low si al ratios have unimodal pore size distributions

black shale deposition and faunal overturn in the devonian appalachian basin clastic starvation seasonal water column mixing and efficient biolimiting nutrient recycling integrated geochemical data suggest that black shale deposition in the devonian geneseo formation of western new york was initiated by the coincidence of siliciclastic starvation and the intensification of seasonal water column stratification and mixing once established however black shale deposition was maintained through efficient recycling of biolimiting nutrients which enhanced primary productivity recycling efficiency was achieved through a positive feedback loop of oscillating benthic redox conditions that enhanced n and p regeneration from sediments sustained high primary productivity by returning nutrients to the photic zone during mixing and ensured a downward flux of organic matter that drove or enhanced the episodic development of benthic anoxia during stratification this feedback was ultimately disrupted by rising siliciclastic influx which diluted organic matter and restored benthic redox stability the abrupt overturn of diverse long standing appalachian basin marine communities may have been the result of trophic resource destabilization during geneseo deposition

geochemical constraints on the origin and volume of gas in the new albany shale devonian mississippian eastern illinois basin this study involved analyses of kerogen petrography gas desorption geochemistry microporosity and mesoporosity of the new albany shale devonian mississippian in the eastern part of the illinois basin specifically detailed core analysis from two locations one in owen county indiana and one in pike county indiana has been conducted the gas content in the locations studied was primarily dependent on total organic carbon content and the micropore volume of the shales gas origin was assessed using stable isotope geochemistry measured and modeled vitrinite reflectance values were compared depth of burial and formation water salinity dictated different dominant origins of the gas in place in the two locations studied in detail the shallower owen county location 415 433 m 1362 1421 ft deep contained significant additions of microbial methane whereas the pike county location 832 860 m 2730 2822 ft deep was characterized exclusively by thermogenic gas despite differences in the gas origin the total gas in both locations was similar reaching up to 2 1 cm3 g 66 scf ton lower thermogenic gas content in the shallower location lower maturity and higher loss of gas related to uplift and leakage via relaxed fractures was compensated for by the additional generation of microbial methane which was stimulated by an influx of glacial melt water inducing brine dilution and microbial inoculation the characteristics of the shale of the maquoketa group ordovician in the pike county location are briefly discussed to provide a comparison to the new albany shale

estimation of marine shale methane adsorption capacity based on experimental investigations of lower silurian longmaxi formation in the upper yangtze platform south china abstract methane adsorption experiments were performed on eight lower silurian longmaxi moisture equilibrated shale samples from the upper yangtze platform south china at pressures up to 12 mpa at 20 c 40 c 60 c 80 c and 100 c to investigate the effects upon methane adsorption capacity and to estimate the variation of methane adsorption capacity as a function of depth and burial history the methane adsorption capacity of the longmaxi shale shows a significant positive correlation with total organic carbon toc content which is accompanied by an increase in bet brunauer emmett teller surface area and total pore volume a quadratic relationship was observed between clay content and methane adsorption capacity there is a threshold clay content 42 3 44 4 in this trend methane adsorption capacity declines with increasing clay content below the threshold and later increases with increasing clay content the langmuir pressure decreases exponentially with the reciprocal of temperature and the langmuir volume decreases linearly with temperature the isosteric heat of adsorption and standard entropy for the longmaxi shale ranges from 10 34 to 11 67 kj mol and from 57 04 to 61 32 j mol k respectively which are clustered around kerogen type i using these relationships a computational scheme was developed to calculate methane adsorption capacity as a function of toc content temperature and pressure based on the langmuir equation this algorithm was applied to estimate methane adsorption capacity of the longmaxi shale as a function of depth due to the dominating effect of pressure methane adsorption capacity increases initially with depth through a maximum and then decreases as a result of increasing temperature at a greater depth the maximum gas adsorption capacity is typically located at a depth range between 800 and 1350 m with toc content increasing the curves shift continuously towards higher adsorption capacity furthermore the maximum methane adsorption capacity moves higher and shifts to a deeper depth as toc content increases ultimately four principal dynamic evolutionary stages of methane adsorption capacity of the longmaxi shale over geologic time as a function of burial history were reconstructed

tracing organic matter composition and distribution and its role on arsenic release in shallow cambodian groundwaters biogeochemical processes that utilize dissolved organic carbon are widely thought to be responsible for the liberation of arsenic from sediments to shallow groundwater in south and southeast asia the accumulation of this known carcinogen to hazardously high concentrations has occurred in the primary source of drinking water in large parts of densely populated countries in this region both surface and sedimentary sources of organic matter have been suggested to contribute dissolved organic carbon in these aquifers however identification of the source of organic carbon responsible for driving arsenic release remains enigmatic and even controversial here we provide the most extensive interrogation to date of the isotopic signature of ground and surface waters at a known arsenic hotspot in cambodia we present tritium and radiocarbon data that demonstrates that recharge through ponds and or clay windows can transport young surface derived organic matter into groundwater to depths of 44 m under natural flow conditions young organic matter dominates the dissolved organic carbon pool in groundwater that is in close proximity to these surface water sources and we suggest this is likely a regional relationship in locations distal to surface water contact dissolved organic carbon represents a mixture of both young surface and older sedimentary derived organic matter ground surface water interaction therefore strongly influences the average dissolved organic carbon age and how this is distributed spatially across the field site arsenic mobilization rates appear to be controlled by the age of dissolved organic matter present in these groundwaters arsenic concentrations in shallow groundwaters 20 m groundwaters we suggest that while the rate of arsenic release is greatest in shallow aquifer sediments arsenic release also occurs in deeper aquifer sediments and as such remains an important process in controlling the spatial distribution of arsenic in the groundwaters of se asia our findings suggest that any anthropogenic activities that alter the source of groundwater recharge or the timescales over which recharge takes place may also drive changes in the natural composition of dissolved organic carbon in these groundwaters such changes have the potential to influence both the spatial and temporal evolution of the current groundwater arsenic hazard in this region

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

organic matter hosted pore system marcellus formation devonian pennsylvania the marcellus formation of pennsylvania represents an outstanding example of an organic matter om hosted pore system most pores detectable by field emission scanning electron microscopy fe sem are associated with om instead of mineral matrix in the two wells studied here total organic carbon toc content is a stronger control on om hosted porosity than is thermal maturity the two study wells span a maturity from late wet gas vitrinite reflectance ro 1 0 to dry gas ro 2 1 samples with a toc less than 5 5 wt display a positive correlation between toc and porosity but samples with a toc greater than 5 5 wt display little or no increase in porosity with a further increasing toc in a subset of samples 14 across a range of toc 2 3 13 6 wt the pore volume detectable by fe sem is a small fraction of total porosity ranging from 2 to 32 of the helium porosity importantly the fe sem visible porosity in om decreases significantly with increasing toc diminishing from 30 of om volume to less than 1 of om volume across the range of toc the morphology and size of om hosted pores also vary systematically with toc the interpretation of this anticorrelation between om content and sem visible pores remains uncertain samples with the lowest om porosity higher toc may represent gas expulsion pore collapse that was more complete as a consequence of greater om connectivity and framework compaction whereas samples with higher om porosity lower toc correspond to rigid mineral frameworks that inhibited compactional expulsion of methane filled bubbles alternatively higher toc samples may contain om low initial hydrogen index relatively unreactive that is less prone to development of fe sem detectable pores in this interpretation om type controlled by sequence stratigraphic position is a factor in determining pore size distribution

geological controls on matrix permeability of devonian gas shales in the horn river and liard basins northeastern british columbia canada abstract controls of matrix permeability are investigated for devonian gas shales from the horn river and liard basins in northeastern british columbia canada mineralogy is varied with high carbonate high quartz and moderate quartz carbonate and clay rich strata quartz content varies between 2 and 73 carbonate varies between 1 and 93 and clay varies between 3 and 33 the toc content ranges between 0 3 and 6 wt and porosity varies between about 1 and 7 for horn river basin samples quartz is mainly biogenic in origin derived from radiolarians toc content increases with the quartz content suggesting the toc and quartz both are derived from siliceous phytoplankton a positive relationship between porosity and quartz content is due to the positive relationship between quartz and toc matrix permeability parallel to bedding varies between 7 5e 02 and 7 1e 07 md at an effective stress of 15 mpa variation in permeability is due to a complex combination of factors that includes origin and distribution of minerals pore size distribution and fabric mercury intrusion capillary curves indicate that the higher matrix permeability values 2e 03 md occurs in samples that contain interconnected pore apertures greater than 16 m even when these samples may contain less macropores than low permeability samples the fabric of high permeability samples can be either isotropic or anisotropic however permeability of anisotropic samples is more sensitive to changes in effective stress than isotropic samples more highly anisotropic samples contain moderate amounts of quartz carbonate and in some clay high permeability samples that contain a more balanced ratio between micro meso and macroporosity would not only have faster flow rates but also greater access to sorbed gas within the microporosity compared to samples that lack mesopores several muskwa samples compared to evie and besa river samples contain higher quartz moderate clay and high toc content coupled with high permeability less sensitivity to effective stress and balanced ratios between micro meso and macroporosity would be a lower exploration risk due a greater propensity to fracture the ability to produce and store hydrocarbons due to higher toc contents and greater communication between macropores and micropores in the organic and clay fractions

polyphase thermal evolution in the infra cambrian ara group south oman salt basin as deduced by maturity of solid reservoir bitumen petrographic and organic geochemical analyses on solid reservoir bitumen from the late precambrian to early cambrian ara group indicate polyphase thermal evolution in the south oman salt basin sosb the ara group constitutes a complex petroleum system in the deep subsurface 3 5 km of interior oman salt diapirs encase isolated partly highly overpressured carbonate bodies intra salt stringers which represent a predominantly self charging hydrocarbon system a large number of stringer cores show that reservoir quality is decreased by the presence of solid reservoir bitumen by using different microscopy techniques this solid reservoir bitumen has been identified within pores pore throats and microfractures of the carbonates solid bitumen reflectance measurements brr were converted to vitrinite reflectance vrr using a new improved calibration vitrinite reflectance geothermometry shows that maximum paleo temperatures have a highly heterogeneous distribution paleo temperatures of 380 c were obtained from coke like solid reservoir bitumen which most likely formed from thermal cracking of oil in our model this process is related to hydrothermal fluids deriving from deeper pre salt strata of the sosb which entered the intra salt carbonate stringers during times of basement tectonic activity via hydrofractures this caused the formation of high maturities pyrobitumens in close vicinity to the fractures and precipitation of migrabitumens with increasing distance to the ht source which is supported by the geochemical composition of the solid reservoir bitumens the influx of these fluids into the carbonate stringers is considered to represent a major contribution to their strong overpressures 2007 elsevier ltd all rights reserved

clay mineral diagenesis and quartz cementation in mudstones the effects of smectite to illite reaction on rock properties abstract the late cretaceous to early tertiary sequence of the voring and more basins from the norwegian sea has been examined with respect to mineralogy based on 319 cutting samples from five wells a clear relationship between mineralogy and well log data is demonstrated a significant change with respect to velocity porosity and density occurs within the depth interval corresponding to 80 90 c at shallow depths temperatures

unconventional shale gas systems the mississippian barnett shale of north central texas as one model for thermogenic shale gas assessment shale gas resource plays can be distinguished by gas type and system characteristics the newark east gas field located in the fort worth basin texas is defined by thermogenic gas production from low porosity and low permeability barnett shale the barnett shale gas system a self contained source reservoir system has generated large amounts of gas in the key productive areas because of various characteristics and processes including 1 excellent original organic richness and generation potential 2 primary and secondary cracking of kerogen and retained oil respectively 3 retention of oil for cracking to gas by adsorption 4 porosity resulting from organic matter decomposition and 5 brittle mineralogical composition the calculated total gas in place gip based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf section 5 78 10 9 m 3 1 73 10 4 m 3 we estimate that the barnett shale has a total generation potential of about 609 bbl of oil equivalent ac ft or the equivalent of 3657 mcf ac ft 84 0 m 3 m 3 assuming a thickness of 350 ft 107 m and only sufficient hydrogen for partial cracking of retained oil to gas a total generation potential of 820 bcf section is estimated of this potential approximately 60 was expelled and the balance was retained for secondary cracking of oil to gas if sufficient thermal maturity was reached gas storage capacity of the barnett shale at typical reservoir pressure volume and temperature conditions and 6 porosity shows a maximum storage capacity of 540 mcf ac ft or 159 scf ton

vlda model and its application in assessing phreatic groundwater vulnerability a case study of phreatic groundwater in the plain area of yanji county xinjiang china based on the god method and drastic model for groundwater vulnerability assessment in this paper vlda model for assessing phreatic groundwater vulnerability is proposed where v is lithology of vadose zone l is the pattern of land use d is groundwater depth and a is the aquifer characteristics as a case study the paper assesses the vulnerability of phreatic groundwater in yanji county of xinjiang by using the vlda model as the tool and gis as the platform and matches the vulnerability with nitrate content of the phreatic groundwater in september 2009 the results indicate that areas with highly vulnerable pore phreatic groundwater account for 40 83 of the total inland area of yanji county including most of the northwestern area such as the groundwater wellfield in korla city and yanji town it is also discovered that areas with phreatic groundwater of higher vulnerability essentially coincide with areas with higher nitrate content indicating the feasibility of using vlda model to assess groundwater vulnerability

classification and provenance of soapstones and garnet chlorite schist artifacts from medieval sites of tuscany central italy insights into the tyrrhenian and adriatic trade abstract soapstones talc bearing schists and garnet chlorite schist artifacts found in medieval archaeological sites of tuscany central italy were classified in order to define provenance of the different lithotypes in italy and throughout the central europe these greenschist facies metamorphic rocks are generally known among the archaeologists as the pietra ollare from the alps the investigated tuscan archaeological sites are between 6 and 13th century ad and were strictly linked in that period to the well defined network trade running along tyrrhenian coast samples come from little containers used for cooking and preserving food and showing traces of lathe manufacturing at their sidewalls according to modal mineralogy petrographic texture xrd sem eds and whole rock chemistry we recognised among the 18 studied findings three different petrographic groups of the alpine pietra ollare i fine grained magnesite talc schists i e soapstones from outcrops of the central alps located in the valchiavenna area ii garnet chlorite schists from the valle d aosta region iii amphibole talc schists i e soapstones with a provenance in the ticino area it is worth noting that artifacts of pietra ollare lithotypes from the western alps i e garnet chlorite schists and amphibole talc schists were not detected in the archaeological sites of the middle adriatic coast of the central italy belonging to the same medieval time interval this emphasises that the petrographic groups of pietra ollare from the alps spread to the south of the po plain according to western and eastern trade along the italian peninsula using respectively the tyrrhenian and the adriatic sea commercial routes

evolution of porosity and geochemistry in marcellus formation black shale during weathering abstract soils developed on the oatka creek member of the marcellus formation in huntingdon pennsylvania were analyzed to understand the evolution of black shale matrix porosity and the associated changes in elemental and mineralogical composition during infiltration of water into organic rich shale making the reasonable assumption that soil erosion rates are the same as those measured in a nearby location on a less organic rich shale we suggest that soil production rates have on average been faster for this black shale compared to the gray shale in similar climate settings this difference is attributed to differences in composition both shales are dominantly quartz illite and chlorite but the oatka creek member at this location has more organic matter 1 25 wt organic carbon in rock fragments recovered from the bottom of the auger cores and nearby outcrops and accessory pyrite during weathering the extremely low porosity bedrock slowly disaggregates into shale chips with intergranular pores and fractures some of these pores are either filled with organic matter or air filled but remain unconnected and thus inaccessible to water based on weathering bedrock soil profiles disintegration is initiated with oxidation of pyrite and organic matter which increases the overall porosity and most importantly allows water penetration water infiltration exposes fresh surface area and thus promotes dissolution of plagioclase and clays as these dissolution reactions proceed the porosity in the deepest shale chips recovered from the soil decrease from 9 to 7 while kaolinite and fe oxyhydroxides precipitate eventually near the land surface mineral precipitation is outcompeted by dissolution or particle loss of illite and chlorite and porosity in shale chips increases to 20 as imaged by computed tomographic analysis weathering causes i greater porosity ii greater average length of connected pores and iii a more branched pore network compared to the unweathered sample this work highlights the impact of shale water o 2 interactions in near surface environments 1 black shale weathering is important for global carbon cycles as previously buried organic matter is quickly oxidized and 2 black shales weather more quickly than less organic and sulfide rich shales leading to high porosity and mineral surface areas exposed for clay weathering the fast rates of shale gas exploitation that are ongoing in pennsylvania texas and other regions in the united states may furthermore lead to release of metals to the environment if reactions between water and black shale are accelerated by gas development activities in the subsurface just as they are by low temperature processes in our field study

the characteristics and significance of conventional and unconventional sinian silurian gas systems in the sichuan basin central china abstract oil and gas discoveries within proterozoic cambrian strata and the majority of shale gas production occurs in relatively stable tectonic regions and characterised by moderate thermal maturity r o o 2 5 the system comprises two components namely a conventional sinian cambrian dolomite hosted gas resource and an unconventional cambrian silurian shale gas deposit both represent trillion cubic meter accumulations the migration accumulation type sinian cambrian gas system is a result of numerous processes including 1 paleo high trapping within a relatively stable tectonic setting 2 appropriate source materials located in a paleo rift trough 3 large scale dolomite grainstone reservoirs located near the paleo high 4 adequate gas produced from in situ crude oil cracking and 5 gypsum salt and shale cap rock preservation the self contained source reservoir cambrian silurian shale gas system is localized by deepwater organic rich shelf facies characterized by high silicon and calcium contents the recent discovery of these two massive gas fields in old and over matured sedimentary strata has effectively extended the upper maturity limit of r o over 3 0 which may indicate the efficacy of broadening current natural gas exploration areas thus potentially increasing global natural gas resources significantly furthermore the discovery may spark interest in natural gas exploration in widely distributed old strata thus encouraging co development of conventional and unconventional petroleum accumulations

pathways of coupled arsenic and iron cycling in high arsenic groundwater of the hetao basin inner mongolia china an iron isotope approach abstract high as groundwater is widely distributed all over the world which has posed a significant health impact on millions of people iron isotopes have recently been used to characterize fe cycling in aqueous environments but there is no information on fe isotope characteristics in the groundwater since groundwater as behavior is closely associated with fe cycling in the aquifers fe isotope signatures may help to characterize geochemical processes controlling as concentrations of shallow groundwaters this study provides the first observation of fe isotope fractionation in high as groundwater and evaluation of fe cycling and as behaviors in shallow aquifers in terms of fe isotope signatures thirty groundwater samples were taken for chemical and isotopic analysis in the hetao basin inner mongolia thirty two sediments were sampled as well from shallow aquifers for fe isotope analysis results showed that groundwater was normally enriched in isotopically light fe with 56fe values between 3 40 and 0 58 and median of 1 14 while heavier 56fe values were observed in the sediments between 1 10 and 0 75 median 0 36 in reducing conditions groundwaters generally had higher 56fe values in comparison with oxic conditions high as groundwaters generally occurring in reducing conditions had high 56fe values while low as groundwaters normally had low 56fe values although sediment 56fe values were generally independent of lithological conditions a large variation in sediment 56fe values was observed in the oxidation reduction transition zone three pathways were identified for fe cycling in shallow groundwater including dissimilatory reduction of fe iii oxides re adsorption of fe ii and precipitation of pyrite and siderite dissimilatory reduction of fe iii oxides resulted in light 56fe values around 1 0 and high as concentration 50 g l in groundwater in anoxic conditions re adsorption of isotopically heavy fe ii produced by microbially mediated reduction of fe iii oxides led to further enrichment of isotopically light fe in groundwater up to 3 4 of 56fe in anoxic suboxic conditions arsenic re adsorption was expected to occur along with fe ii re adsorption decreasing groundwater as concentrations in strongly reducing conditions precipitation of isotopically light fe pyrite and or siderite increased groundwater 56fe values reaching 0 58 56fe with a subsequent decrease in as concentrations via co precipitation the mixed effect of those pathways would regulate as and fe cycling in most groundwaters

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

origin and tectonic significance of a mesozoic multi layer over thrust system within the yangtze block south china abstract in the yangtze block south china a well developed mesozoic thrust system extends through the xuefeng and wuling mountains in the southeast to the sichuan basin in the northwest the system comprises both thin and thick skinned thrust units separated by a boundary detachment fault the dayin fault to the northwest the thin skinned belt is characterized by either chevron anticlines and box synclines to the northwest or chevron synclines to the southeast the former structural style displays narrow exposures for the cores of anticlines and wider exposures for the cores of synclines thrust detachments occur along silurian fs and lower cambrian fc strata and are dominantly associated with the anticlines to the southeast this style of deformation passes gradually into one characterized by chevron synclines with associated principal detachment faults along silurian fs cambrian fc and lower sinian fz strata there are however numerous secondary back thrusts therefore the thin skinned belt is like the valley and ridge province of the north american applachian mountains the thick skinned belt structurally overlies the thin skinned belt and is characterized by a number of klippen including the xuefeng and wuling nappes it is thus comparable to the blue ridge province of appalachia the structural pattern of this thrust system in south china can be explained by a model involving detachment faulting along various stratigraphic layers at different stages of its evolution the system was developed through a northwest stepwise progression of deformation with the earliest delamination along lower sinian strata fz analyses of balanced geological cross sections yield about 18 1 21 total 88 km shortening for the thin skinned unit and at least this amount of shortening for the thick skinned unit the compressional deformation from southeast to northwest during late jurassic to cretaceous time occurred after the westward progressive collision of the yangtze block with the north china block and suggests that the orogenic event was intracontinental in nature

characterizing the shale gas resource potential of devonian mississippian strata in the western canada sedimentary basin application of an integrated formation evaluation devonian mississippian strata in the northwestern region of the western canada sedimentary basin wcsb were investigated for shale gas potential in the subsurface thermally mature strata of the besa river horn river muskwa and fort simpson formations attain thicknesses of more than 1 km 0 6 mi encompassing an area of approximately 125 000 km2 48 300 mi2 and represent an enormous potential gas resource total gas capacity estimates range between 60 and 600 bcf section of particular exploration interest are shales and mudrocks of the horn river formation including the laterally equivalent lower besa river mudrocks muskwa formation and upper besa river formation which yield total organic carbon toc contents of up to 5 7 wt fort simpson shales seldom have toc contents above 1 wt horn river and muskwa formations have excellent shale gas potential in a region between longitudes 122w and 123w and latitudes 59n and 60n national topographic system nts 94o08 to 94o15 in this area which covers an areal extent of 6250 km2 2404 mi2 average toc contents are higher 3 wt as determined by wire line log calibrations and have a stratal thickness of more than 200 m 656 ft gas capacities are estimated to be between 100 and 240 bcf section and possibly greater than 400 tcf gas in place a substantial percentage of the gas capacity is free gas caused by high reservoir temperatures and pressures muskwa shales have adsorbed gas capacities ranging between 0 3 and 0 5 cm3 g 9 6 16 scf t at reservoir temperatures of 60 80c 140 176f whereas besa river mudrocks and shales have low adsorbed gas capacities of less than 0 01 cm3 g 0 32 scf t liard basin region because reservoir temperatures exceed 130c 266f potential free gas capacities range from 1 2 to 9 5 cm3 g 38 4 to 304 scf t when total pore volumes 0 4 6 9 are saturated with gas the mineralogy has a major influence on total gas capacity carbonate rich samples indicative of adjacent carbonate platform and embayment successions commonly have lower organic carbon content and porosity and corresponding lower gas capacity 1 toc and 1 porosity seaward of the carbonate slave point edge muskwa and lower besa river mudrocks can be both silica and toc rich up to 92 quartz and 5 wt toc and most favorable for shale gas reservoir exploration because of possible fracture enhancement of the brittle organic and siliceous rich facies however an inverse relation between silica and porosity in some regions implies that zones with the best propensity for fracture completion may not provide optimal gas capacity and a balance between favorable reservoir characteristics needs to be sought

occurrence and geochemistry of arsenic in the groundwater of eastern croatia in order to examine the extent of the as enrichment and the factors influencing this enrichment in the groundwater of eastern croatia groundwater samples were collected from 56 production wells in two counties osijek baranja and vukovar srijem suspected to be more affected hydrochemical analyses were performed at all locations including in situ as speciation at 32 locations arsenic was detected in 46 out of 56 groundwater samples with total as concentrations up to 491 g l thirty six of the studied wells yielded groundwater with total as concentrations that exceeded the who maximum contaminant level for arsenic in drinking water of 10 g l only inorganic as species were detected with arsenite as iii as the predominant form the spatial distribution of as in the groundwater was significantly linked with geological geomorphological and hydrogeological development of the alluvial basin of the drava and sava rivers the most probable groundwater as sources are deeper sediments from the middle and upper pleistocene the results obtained suggest that biogeochemical processes controlling as concentration in the groundwater are complex and location specific reductive dissolution of fe oxides desorption of as from fe oxides and or clay minerals as well as competition for the sorption sites with organic matter and phosphate could be the principal mechanisms that control as mobilization the extent of those processes vary in the different parts of the drava and sava depressions and could be linked to different site related parameters such as lithology mineralogy local hydrology and hydrogeology thus different processes of as mobilization have been proposed for the different types of water in relation to groundwater evolution

variation of groundwater hydrochemical characteristics in the plain area of the tarim basin xinjiang region china groundwater hydrochemistry could reveal the interaction mechanism between groundwater and the environment which provides a scientific basis for environmental resources management in this study shukaliefu s classification method and piper diagram were adopted to determine the hydrochemical types of groundwater in the tarim basin of xinjiang china the method of one vote veto was applied to evaluate the quality of groundwater phreeqc software was used to calculate the saturation indices of calcite and fluorite in groundwater by comparing groundwater quality data of 2003 and 2011 we characterized the variations in hydrochemical types and water quality types salinization of groundwater and fluoride geochemistry of the plain area of the tarim basin results show that the primary anion in phreatic water in the plain area of the tarim basin changed from hco3 to so4 2 or cl on the contrary the primary anion in confined water changed from so4 2 or cl to hco3 in 2003 63 1 of the sampling points in the study area exceeded the class iii water quality standard of china in 2011 the proportion increased to 82 5 in addition severe groundwater salinization was found at 19 7 of the sampling points some of the deep groundwater samples were salinized as well in the aksu area at the north west part of the tarim basin f concentration exceeding the standard limit 1 mg l was found to be 55 0 of the groundwater samples tested based on these findings it is concluded that the phreatic water in the study area was severely influenced by the industrial wastewater and domestic sewage related to human activities while the confined water was less affected the general quality of groundwater was in an aggravation trend and the groundwater salinization was in a severe condition in this area the ca2 na ionic exchange the unsaturated fluorite and oversaturated calcite in the aquifer of the aksu area are proposed to cause f enrichment in groundwater of this area

distribution of groundwater arsenic in xinjiang p r china although potential contamination of groundwater as is expected to occur in xinjiang p r china few data are available for the regional distribution of groundwater as in this study the spatial distribution of groundwater as was investigated in the chepaizi cpz n and shihezi shz n areas of northern xinjiang the balikun yiwu basin by e in eastern xinjiang and the tarim trm s and yanqi yq s basins in southern xinjiang arsenic concentrations greater than 10 g l were found in 12 of analyzed groundwaters all groundwater samples collected in cpz n had as concentrations greater than 10 g l 25 185 g l 30 in shz n 10 g l was found in the eastern and southern trm s and yq s distribution of groundwater as showed a tremendous spatial variability which greatly varied over a short distance horizontally arsenic concentration generally increased with increasing sampling depth the spatial distribution of groundwater as would be regulated by as source and hydrogeochemical processes higher ph and or lower orp values were generally observed in high as groundwater 10 g l in comparison with low as groundwater 10 g l arsenic mobility in shz n and cpz n may result from as desorption under relatively high ph conditions and more tentatively from reductive dissolution of fe iii oxides in by e and trm s however detailed mechanisms of as mobilization in these regions need further investigation

multiple controls on the preservation of organic matter in devonian mississippian marine black shales geochemical and petrographic evidence geochemical and petrographic analysis of an interval of black shales between the huron shale member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian suggests that multiple controls influenced the accumulation of organic matter stratigraphic trends were determined following detailed analysis of a core from the central appalachian basin d6 montgomery county ky specifically c s fe relationships mo v v ni ni co and v cr were used to assess paleo redox conditions during sediment accumulation the role of clastic input was evaluated using ti al k al and si al and c p was used as a proxy for paleoproductivity the terrestrial to marine maceral ratio t m vitrinite plus inertinite alginite plus bituminite was used to evaluate changes in om source c s fe relationships and trace element ratios suggest anoxic conditions prevailed during deposition of much of the upper part of this interval however bottom water conditions were intermittently dysoxic during accumulation of the huron shale member and possibly dysoxic to marginally oxic during accumulation of the lowermost huron shale member productivity appears to have been an important factor in the accumulation of corg and high c p ratios are consistent with a productivity anoxia feedback mechanism in addition nutrients from increased terrestrial weathering may have contributed to enhanced productivity variations in sediment influx may also have influenced corg concentrations through sediment starvation one of the more significant observations in this work is an increase in terrestrial om inertinite and vitrinite up section which may reflect vegetative changes occurring on land during this time interval most of this increase is due to inertinite much of which appears to be fusinitic in origin and hence may be fossil charcoal this latter observation has implications for the expansion of land plants into drier niches and for late devonian atmospheric oxygen levels introduction of more resistant terrestrial om to anoxic basins may have been an important factor in the preservation of high carbon 10 intervals especially in the cleveland member of the new albany shale upper devonian famennian and the sunbury shale lower mississippian tournaisian

high resolution stable isotope stratigraphy of upper ordovician sequences constraints on the timing of bioevents and environmental changes associated with mass extinction and glaciation the two phases of the late ordovician mass extinction are approximately coeval with the periods of rapid climate change associated with the onset and demise of the gondwanan glaciation in this paper we argue that the distinctive late ordovician carbon isotope profile provides a chronostratigraphic ruler against which a sequence of environmental and biotic events may be located the ruler also allows regional and global high resolution correlation of successions representing very different environments cores from the upper ordovician succession of estonia and latvia record a large 1 3 c c a r b o n a t e excursion up to 6 with a similar profile shape the consistent relationship between the chemostratigraphy and biostratigraphy in the baltic region suggests that the isotope profile has a regional chronostratigraphic value the presence of similar profiles in nevada united states suggests that the excursion is a global chronostratigraphic signal this interpretation enables a detailed correlation to be made between upper ordovician shallow marine and basinal sequences that have wholly different faunas successions in the baltic area and in canada that do not display the model profile are interpreted as incomplete reinter pretation of these important successions significantly modifies the global database used to assess the pattern of diversity change during the mass extinction key levels of environmental change have been located against the carbon isotope profile new oxygen isotope data from brachiopod and ostracode calcite set tight limits on the start of the glacial events cooling and sea level fall started at the same stratigraphic level as the start of the carbon isotope excursion the later rise in sea level and fall in oxygen isotope values record the end of the glaciation these restrict the duration of the main glaciation to only 1 5 graptolite zones we propose that models of the carbon cycle should be adapted to be consistent with the temporal relationships between carbon cycling sea level fall and temperature change documented here the chronostratigraphic ruler provided by the carbon isotope profiles is used as a scale to determine the sequence of biotic changes and to allow high resolution correlation of biotic events at different locations this approach identifies regional similarities and differences in the patterns of extinction the main phase of graptolite extinction in the monitor range nevada for example is synchronous with the chitinozoan extinction in the baltic region but chitinozoan taxa survive to higher levels in nevada the benthic faunas in the baltic region demonstrate that the main extinction event corresponded with the beginning of the isotope excursion at the start of the hirnantian the level at which the marine environment started to change rapidly but that there were further extinctions of species within the early hirnantian the cold adapted hirnantia fauna did not appear immediately after the extinction in this area the relationship between the second phase of extinction and the carbon isotope excursion is less clear but the available data suggest that the extinction coincides with a time of rapid environmental change but not at the inception of environmental change as happened in the first phase

hydrogeochemical zonation and its implication for arsenic mobilization in deep groundwaters near alluvial fans in the hetao basin inner mongolia summary high as groundwater has been found in shallow aquifers of the flat plain of the hetao basin but little is known about as concentration in deep groundwaters around piedmont areas which are the major drinking water resources one hundred and three groundwater samples from wells with depths 50 m and seven samples from one multi level monitoring well 89 m in depth were analyzed for chemical compositions and 18o and d isotopes to examine the geochemical processes controlling as mobilization according to hydrogeological setting chemical and isotopic characteristics of deep groundwater three distinguished hydrogeochemical zones are delineated including recharge oxic zone zone i groundwater flow moderate reducing zone zone ii and groundwater flow reducing zone zone iii zone i is located in proximal fans in the recharge area with oxic conditions where low as groundwater generally occurs in zone ii located in the intermediate between the fans and the flat plain with fe reduction predominated groundwater as is moderate zone iii lies in the flat plain with the occurrence of so 4 2 reduction where high as groundwater is mostly found this indicates that release of as to groundwater is primarily determined by reduction sequences arsenic is immobilized in o 2 no 3 reduction stage in zone i and released in fe reducing conditions of zone ii and displays a significant elevated concentration in so4 reducing stage in zone iii dissolution of carbonate minerals occurs in zone i while ca2 and mg2 are expected to precipitate in zone ii and zone iii in the multi level monitoring well both chemical and isotopic compositions are dependent of sampling depths with the similar trend to the hydrogeochemical zonation along the flow path the apparent increases in d and 18o values in zone iii reveal the possibility of high as shallow groundwater recharge to deep groundwater it indicates that deep groundwaters in proximal fans have low as concentrations and are considered as safe drinking water resources in the hetao basin however high as concentration is frequently observed in deep groundwater in the flat plain which should be routinely monitored in order to avoid chronic as poisoning

spatial variation in arsenic and fluoride concentrations of shallow groundwater from the town of shahai in the hetao basin inner mongolia abstract twenty nine wells were selected for groundwater sampling in the town of shahai in the hetao basin inner mongolia four multilevel samplers were installed for monitoring groundwater chemistry at depths of 2 5 20 m results show that groundwater as exhibits a large spatial variation ranging between 0 96 and 720 g l with 71 of samples exceeding the who drinking water guideline value 10 g l fluoride concentrations range between 0 30 and 2 57 mg l there is no significant correlation between as and f concentrations greater as concentrations were found with increasing well depth however f concentrations do not show a consistent trend with depth groundwater with relatively low eh has high as concentrations indicating that the reducing environment is the major factor controlling as mobilization low as concentrations 2 into the aquifers and lead to reducing conditions that favor as release sediment composition is an additional factor in determining dissolved as concentrations in aquifers composed of yellowish brown fine sands at depths around 10 m groundwater generally has low as concentrations which is attributed to the high as adsorption capacity of the yellow brown fe oxyhydroxide coatings fluoride concentration is positively correlated with ph and negatively correlated with ca 2 concentration all groundwater samples are over saturated with respect to calcite and under saturated with respect to fluorite dissolution and precipitation of ca minerals such as fluorite and calcite and f adsorption desorption are likely controlling the concentration of f in groundwater

natural organic matter in sedimentary basins and its relation to arsenic in anoxic ground water the example of west bengal and its worldwide implications in order to investigate the mechanism of as release to anoxic ground water in alluvial aquifers the authors sampled ground waters from 3 piezometer nests 79 shallow 80 m wells in an area 750 m by 450 m just north of barasat near kolkata calcutta in southern west bengal high concentrations of as 200 1180 mug l 1 are accompanied by high concentrations of fe 3 13 7 mgl 1 and po4 1 6 5 mg l 1 ground water that is rich in mn 1 5 3 mg l 1 contains 50 mug l 1 of as the composition of shallow ground water varies at the 100 m scale laterally and the metre scale vertically with vertical gradients in as concentration reaching 200 mug l 1 m 1 the as is supplied by reductive dissolution of feooh and release of the sorbed as to solution the process is driven by natural organic matter in peaty strata both within the aquifer sands and in the overlying confining unit in well waters thermotolerant coliforms a proxy for faecal contamination are not present in high numbers 10 cfu 100 ml in 85 of wells showing that faecally derived organic matter does not enter the aquifer does not drive reduction of feooh and so does not release as to ground water arsenic concentrations are high much greater than50 mug l 1 where reduction of feooh is complete and its entire load of sorbed as is released to solution at which point the aquifer sediments become grey in colour as feooh vanishes where reduction is incomplete the sediments are brown in colour and resorption of as to residual feooh keeps as concentrations below 10 mug l 1 in the presence of dissolved fe sorbed as released by reduction of mn oxides does not increase as in ground water because the as resorbs to feooh high concentrations of as are common in alluvial aquifers of the bengal basin arise because himalayan erosion supplies immature sediments with low surface loadings of feooh on mineral grains to a depositional environment that is rich in organic mater so that complete reduction of feooh is common c 2004 published by elsevier ltd

predicting groundwater arsenic contamination in southeast asia from surface parameters arsenic contamination of groundwater resources threatens the health of millions of people worldwide particularly in the densely populated river deltas of southeast asia although many arsenic affected areas have been identified in recent years a systematic evaluation of vulnerable areas remains to be carried out here we present maps pinpointing areas at risk of groundwater arsenic concentrations exceeding 10 g l 1 these maps were produced by combining geological and surface soil parameters in a logistic regression model calibrated with 1 756 aggregated and geo referenced groundwater data points from the bengal red river and mekong deltas we show that holocene deltaic and organic rich surface sediments are key indicators for arsenic risk areas and that the combination of surface parameters is a successful approach to predict groundwater arsenic contamination predictions are in good agreement with the known spatial distribution of arsenic contamination and further indicate elevated risks in sumatra and myanmar where no groundwater studies exist arsenic contamination of groundwater resources threatens the health of millions of people worldwide particularly in the densely populated river deltas of southeast asia maps of areas at risk of groundwater arsenic concentrations have been produced by combining geological and surface soil parameters in a logistic regression model they show that holocene deltaic and organic rich surface sediments are key indicators for arsenic risk areas and indicate elevated risks in sumatra and myanmar where no groundwater studies exist

the methane sorption capacity of paleozoic shales from the sichuan basin china the methane sorption capacities of paleozoic shales from the sichuan basin were investigated the primary results show they have sorption capacities ranging between 0 94 and 4 29 cm3 grock at stp comparable to the sorption capacity 1 27 2 41 cm3 grock at stp of barnett shale however the sorption isotherms indicate that most of the sichuan basin shales would reach their approximate sorption equilibrium at 3 4 mpa in contrast to the continuously upward trend of north american shales a general positive relationship between toc content and methane sorption capacity indicates that toc content is the major controlling factor for the methane sorption of the sichuan shales a negative relationship between the clay mineral content and the sorption capacity of these shales may suggest that clay minerals play an insignificant role in the methane sorption of these paleozoic shales sorption capacities and variation ranges are generally ordered as to geological age viz cambrian silurian permian

diagenetic origin of quartz silt in mudstones and implications for silica cycling mudstone the most abundant sedimentary rock type1 composed primarily of clay or silt sized particles contains most of the quartz found in sedimentary rocks2 these quartz grains which are chemically and mechanically resistant and therefore preserve their characteristics well have long been considered to be derived from the continental crust1 here we analyse quartz silt from black shales in the eastern usa dating back to the late devonian period about 370 million years ago using backscattered electron and cathodoluminescence imaging and measure oxygen isotopes with an ion probe our results indicate that up to 100 of the quartz silt in our samples does not originate from the continental crust instead it appears to have precipitated early in diagenesis in algal cysts and other pore spaces3 with silica derived from the dissolution of opaline skeletons of planktonic organisms such as radiolaria and diatoms transformation of early diatoms into in situ quartz silt might explain the time gap between the earliest fossil occurrences of diatoms about 120 myr ago4 and molecular evidence for a much earlier appearance between 266 or even 500 myr ago5 6 moreover if many other mudstone successions show similarly high proportions of in situ precipitated rather than detrital quartz silt the sedimentary record in mudstones may have been misinterpreted in the past with consequences for our estimates of palaeoproductivity as well as our perceptions of the dynamics and magnitude of global biogeochemical cycling of silica

porosity of devonian and mississippian new albany shale across a maturation gradient insights from organic petrology gas adsorption and mercury intrusion the evolution of porosity in shales with increasing maturity was examined in a suite of five new albany shale samples spanning a maturity range from immature vitrinite reflectance ro 0 35 to postmature ro 1 41 devonian to lower mississippian new albany shale samples from the illinois basin used in this study contain marine type ii kerogen having total organic carbon contents from 1 2 to 13 0 wt organic petrology co2 and n2 low pressure adsorption and mercury intrusion capillary pressure techniques were used to quantify pore volumes pore sizes and pore size distributions increasing maturity of the new albany shale is paralleled by many changes in the characteristics of porosity the total porosity of 9 1 vol in immature new albany shale decreases to 1 5 vol in the late mature sample whereas total pore volumes decrease from 0 0365 to 0 0059 cm3 g in the same sequence reversing the trend at even higher maturity the postmature new albany shale exhibits higher porosity and larger total pore volumes compared to the late mature sample with increasing maturity changes in total porosity and total pore volumes are accompanied by changes in pore size distributions and relative proportions of micropores mesopores and macropores porosity related variances are directly related to differences in the amount and character of the organic matter and mineralogical composition but maturity exerts the dominant control upon these characteristics we conclude that organic matter transformation due to hydrocarbon generation and migration is a pivotal cause of the observed porosity differences

characterizing the pore structure in the silurian and permian shales of the sichuan basin china abstract nitrogen sorption and mercury intrusion methods were applied to characterize the pore structure of the lower silurian shales of the long ma xi formation and upper permian shales of the da long formation in the sichuan basin the results indicate that the specific surface areas and porosities of the silurian shales are in the range of 17 83 29 49 m 2 g and 3 65 18 26 respectively the silurian shales show a bimodal pore size distribution and consist of both micropores and nanopores ranging from 30 to 60 m and 1 7 20 nm respectively a strong positive linear correlation between the surface areas and total organic carbon content toc suggests that the organic matter contributes mostly to the amount of specific surface area of the silurian shales whereas the contribution of clay minerals appears to be negligible the organic matter also accounts for 50 70 of the porosity in the silurian shales soluble organic matter in the form of bitumen however has a negative impact on the surface area and porosity of the silurian shales and reduce the amount of surface area and porosity in these shales for the permian shales their surface area and porosity are lower than those of the silurian shales and are in the ranges of 2 20 3 52 m 2 g and of 1 30 4 15 respectively the pore size distribution of the permian shales shows a unimodal pattern of micropores in a size range of 30 60 m their toc and clay mineral contents display poor correlation with the surface areas and suggest that both the organic matter and clay minerals have very low surface areas a clear negative correlation between the porosity and toc in the permian shales indicates that organic matter contributes little or insignificantly to the porosity due to poorly developed organic pores in kerogen because the permian shales are much lower in thermal maturity than the silurian shales furthermore there is a consistent negative linear correlations between the bitumen content and the porosity for both the permian shales and silurian shales and indicate that the bitumen may significantly reduce the porosity of the shales by occupying the pore spaces in the mineral and organic matrix finally it is clear that the lower silurian shales have a greater shale gas potential than the upper permian shales do based on their surface area and porosity

on the scalability of hydrogeochemical factors controlling arsenic mobility in three major inland basins of p r china abstract high as groundwater has been widely found in inland basins of p r china which has posed a serious health risk to the local residents although these inland basins experience the same arid to semiarid climate and are filled with quaternary sediments as concentrations show big variations three inlands basins have been investigated to characterize hydraulic conductivities and geochemistry of the groundwater and sediments and evaluate their controls on dissolved as concentrations dissolved as concentrations ranged between

mechanisms of shale gas storage implications for shale gas exploration in china this article reviews the mechanisms of shale gas storage and discusses the major risks or uncertainties for shale gas exploration in china at a given temperature and pressure the gas sorption capacities of organic rich shales are primarily controlled by the organic matter richness but may be significantly influenced by the type and maturity of the organic matter mineral composition especially clay content moisture content pore volume and structure resulting in different ratios of gas sorption capacity gsc to total organic carbon content for different shales in laboratory experiments the gsc of organic rich shales increases with increasing pressure and decreases with increasing temperature under geologic conditions assuming hydrostatic pressure gradient and constant thermal gradient the gsc increases initially with depth due to the predominating effect of pressure passes through a maximum and then decreases because of the influence of increasing temperature at greater depth this pattern of variation is quite similar to that observed for coals and is of great significance for understanding the changes in gsc of organic rich shales over geologic time as a function of burial history at an elevated temperature and pressure and with the presence of moisture the gas sorption capacities of organic rich shales are quite low as a result adsorption alone cannot protect sufficient gas for high maturity organic rich shales to be commercial gas reservoirs two models are proposed to predict the variation of gsc and total gas content over geologic time as a function of burial history high contents of free gas in organic rich shales can be preserved in relatively closed systems loss of free gas during postgeneration uplift and erosion may result in undersaturation the total gas contents lower than the sorption capacity and is the major risk for gas exploration in marine organic rich shales in china

characterization of gas shale pore systems by porosimetry pycnometry surface area and field emission scanning electron microscopy transmission electron microscopy image analyses examples from the barnett woodford haynesville marcellus and doig units the nanometer scaled pore systems of gas shale reservoirs were investigated from the barnett marcellus woodford and haynesville gas shales in the united states and the doig formation of northeastern british columbia canada the purpose of this article is to provide awareness of the nature and variability in pore structures within gas shales and not to provide a representative evaluation on the previously mentioned north american reservoirs to understand the pore system of these rocks the total porosity pore size distribution surface area organic geochemistry mineralogy and image analyses by electron microscopy were performed total porosity from helium pycnometry ranges between 2 5 and 6 6 total organic carbon content ranges between 0 7 and 6 8 wt and vitrinite reflectance measured between 1 45 and 2 37 the gas shales in the united states are clay and quartz rich with the doig formation samples being quartz and carbonate rich and clay poor higher porosity samples have higher values because of a greater abundance of mesopores compared with lower porosity samples with decreasing total porosity micropore volumes relatively increase whereas the sum of mesopores and macropore volumes decrease focused ion beam milling field emission scanning electron microscopy and transmission electron microscopy provide high resolution 5 nm images of pore distribution and geometries image analysis provides a visual appreciation of pore systems in gas shale reservoirs but is not a statistically valid method to evaluate gas shale reservoirs macropores and mesopores are observed as either intergranular porosity or are confined to kerogen rich aggregates and show no preferred orientation or align parallel with the laminae of the shale networks of mesopores are observed to connect with the larger macropores within the kerogen rich aggregates

a preliminary study on the pore characterization of lower silurian black shales in the chuandong thrust fold belt southwestern china using low pressure n2 adsorption and fe sem methods although lower silurian black shales within and around the sichuan basin have received renewed attention during the past few years because of their potential prospectivity for shale gas studies associated with shale gas reservoir evaluation are still rare in this study eight black shale core samples were collected from a well drilled recently in the chuandong thrust fold belt southwestern china and their geochemistry and pore structures were investigated using low pressure n2 adsorption analysis and field emission scanning electron microscopy fe sem observations the results show that the black shales have total organic carbon toc values ranging from 1 01 to 3 98 and their equivalent vitrinite reflectance values are in the range of 2 84 3 05 both mineral matrix and organic matter pores are well developed with pore sizes ranging from several to several hundred nanometers the total porosity for the eight samples ranges from 2 60 to 4 74 and the percentages of organic matter pores are estimated to be in the range of 31 62 the total surface area ranges from 5 06 m2 g to 19 32 m2 g and the micropore 2 nm surface area estimated by the t plot method ranges from 3 13 m2 g to 9 27 m2 g the toc values have positive relationships with the total porosity total surface area and the micropore 2 nm volume and surface area indicating toc may be an effective parameter for shale gas reservoir evaluation in the studied area

a review of high arsenic groundwater in mainland and taiwan china distribution characteristics and geochemical processes china is a typical high as region where 20 provinces have high as groundwaters among 34 provinces these groundwaters usually occur in both arid semiarid inland basins and river deltas in the inland basins mainly distributed in the northwest of china shallow groundwaters usually have high as concentrations in alluvial lacustrine or lacustrine sediment aquifers while high as groundwater mainly occurs in fluvial marine sedimentary aquifers in the river deltas which have been affected by transgression in both the inland basins and the river deltas high as groundwaters mainly occurring in reducing conditions are characterized by high fe and mn concentrations high ph and hco3 concentration and relatively low no3 and so42 concentrations although as contents are well correlated to fe mn contents in the aquifer sediments groundwater as concentrations are generally independent of sediment as contents redox processes microbe related reduction and desorption processes are the major geochemical processes for as enrichment in groundwaters in reducing conditions both reductive dissolution of fe oxides and reductive desorption of as are believed to result in as mobilization which would be catalyzed by indigenous microbes although decomposition of the low molecular weight organic matter during microbe metabolization would also release the colloid bound as into groundwater the cycling of colloidal as still needs to be further investigated during redox processes besides high ph and high hco3 lead to as desorption from adsorption sites in the aquifer systems however the contribution of competitive desorption to high as concentrations is still unknown and remains to be discovered relative to reductive dissolution of fe oxides especially in the inland basins

organic geochemical characteristics mineralogy petrophysical properties and shale gas prospects of the wufeng longmaxi shales in sanquan town of the nanchuan district chongqing thick marine shales occur in the wufeng formation and longmaxi formation of sanquan town of the nanchuan district chongqing municipality which is located on the southeast margin of the sichuan basin however few details of the characteristics of the wufeng longmaxi shales in this area have been reported in this study a well approximately 100 m 328 ft deep was drilled a high quality shale total organic carbon toc 2 0 wt clay 40 interval that was approximately 24 m 79 ft thick with an average toc value of 3 0 wt mainly occurs in the ordovician wufeng formation katian and hirnantian and base of the silurian longmaxi formation rhuddanian shales with higher toc values commonly have a higher porosity and specific surface area tectonic movements may also have been very important factors that influenced the petrophysical properties of the shales for example a detachment layer that resulted from complex tectonic movements is extensive in the wufeng formation the cracks and microcracks in the detachment layer can result in good pore connectivity consequently the detachment layer can be an effective migration pathway the longmaxi wufeng shales of sanquan town are also compared with those of the famous jiaoye 1 well in the jiaoshiba shale gas field in the eastern sichuan basin although the shales in sanquan town have considerable shale gas generation potential the shale gas resource potential in sanquan town is probably poor because the escape of shale gas may be accelerated by the detachment layer in destroyed anticlines and synclines

geologic geomorphic and hydrologic framework and evolution of the bengal basin india and bangladesh abstract the bengal basin the largest fluvio deltaic sedimentary system on earth is located in bangladesh and three eastern states of india sediment accumulates in the basin from the ganges brahmaputra and meghna gbm river systems and is dispersed into the bay of bengal forming the largest submarine fan in the world the basin is located in the himalayan foreland at the junction of the indian eurasian and burmese plates the basin is bounded by the indian craton on the west and the indo burmese fold belts on the east it can be broadly divided into a stable shelf and a foredeep separated by a deep seismic hinge zone basin sediments overlie gondwanan basement and vary in thickness from a few kilometers on the stable shelf to more than 16 km in the foredeep the basin was initiated at the breakup of gondwanaland in the late mesozoic and evolved through the formation of the proto gbm delta to the present delta starting around 10 5 ma the stratigraphy of the different parts of the basin differs considerably because of contrast in depositional history within the several sub basins that were produced by intra plate tectonic activities associated with ongoing himalayan orogeny the present day geomorphology is dominated by the extensive holocene gbm floodplain and delta the vertical succession of the deltaic plain can be classified into five units on the basis of differences in grain size which reflect differing depositional environments the initiation of the modern gbm delta at the onset of the pleistocene glacial maximum and its evolution to the present configuration are intricately related to holocene fluvio dynamic processes eustatic sea level changes and tectonic movements the sedimentology and mineralogy of the different parts of the basin reflect differences in sediment provenance the mineralogy is dominated by detrital quartz some feldspar and minor amounts of carbonates illite and kaolinite are the main clay minerals the basin has profuse groundwater resources but the architecture of the aquifers is not yet well resolved different classification schemes have been proposed on the basis of lithology regional groundwater flow follows a low hydraulic gradient from north to south but pumping for irrigation during the past several decades appears to have severely distorted regional flow recharge occurs primarily during the monsoon season groundwater chemistry is dominated by anoxic ca hco 3 type water with relatively high concentrations of fe mn and as carbonate dissolution silicate weathering feooh reduction and mixing with saline water are the primary processes controlling hydrochemistry

effect of indigenous bacteria on geochemical behavior of arsenic in aquifer sediments from the hetao basin inner mongolia evidence from sediment incubations abstract incubation studies were carried out using 5 freshly collected sediments from shallow aquifers of the hetao basin inner mongolia the aquifer sediments covering a range of redox conditions as indicated by their deep grey to yellow color were mixed with degassed artificial as solution or degassed deionized water at a ratio of solid to water of about 1 10 wt wt suspensions which were either amended with glucose or autoclaved were incubated in parallel with unamended suspensions five microcosm cultures of unamended sediments gradually release the equivalent of 0 03 0 30 g g as to the dissolved phase the addition of glucose as a potential electron donor results in a marked stimulation in the mobilization of as 0 71 3 81 g g in the amended incubations for all sediments the quantity of as released accounts for 60 70 of as bound to fe mn oxides in the original sediments the microbially mediated mobilization of as with the organic nutrient as an electron donor is strongly associated with the as bound to fe mn oxides as well as the exchangeable as during the incubations amended with glucose 2 4 of the sediment fe is released the results suggest that the introduction of labile dissolved organic c into the yellowish sediment aquifers with as free groundwater would reduce a significant proportion of the fe iii oxyhydroxides mediated by anaerobic bacteria respiration and increase groundwater as concentrations

sources and controls of arsenic contamination in groundwater of rajnandgaon and kanker district chattisgarh central india summary a high concentration of arsenic as contamination in ground water has been reported in the village of kaudikasa in rajnandgaon district wherein around 10 of the population is suffering from as borne diseases the region does not share any demographic or geological similarity with the sedimentary aquifers of the bengal delta plain in eastern india but represents an igneous terrain with elevated as concentrations in groundwater there is limited information about the source of as in groundwater and its mobility constraints in this area almost all the wells are located in the granitic terrain with pegmatitic intrusions most of these wells are characterized by as concentration above the world health organization who 1999 and the bis bureau of indian standards standards with the highest being found in a well with more than 250 g l of as here we report petrographic studies of the granitic host rock and x ray diffraction results that indicate that altered realgar as4s4 para realgar ass and or tennantite cu12as4s13 are the main mineral that contain as this element is leached during the weathering and water rock interactions microprobe analysis of the altered realgar grains of in pegmatitic intrusions of the host granite indicate 23 27 wt as remote sensing is useful to delineate the source of this contaminant which appears to lie at the intersection of a mineralized nw se and n s lineaments associated with the kotri rift zone these lineaments are structurally controlled as rifting followed by thrusting and other types of faulting caused left lateral displacement of n s kotri lineament along a nw se fault plane showing sinistral shearing this process caused water drainage in the areas to flow along these highly mineralized weak zones thus the water becomes highly contaminated due to leaching of minerals at the intersection of these lineaments clearly visible at two areas of high contamination that lie very near to this intersection over granitic rock the source of as affecting the rajnandgaon district is located in granites that have pegmatitic intrusions likely generated by hydrothermal activity

hydrological control of as concentrations in bangladesh groundwater 1 the elevated arsenic as content of groundwater from wells across bangladesh and several other south asian countries is estimated to slowly poison at least 100 million people the heterogeneous distribution of dissolved arsenic in the subsurface complicates understanding of its release from the sediment matrix into the groundwater as well as the design of mitigation strategies using the tritium helium 3h 3he groundwater dating technique we show that there is a linear correlation between groundwater age at depths 20 m and dissolved as concentration with an average slope of 19 g l 1 yr 1 monitoring wells only we propose that either the kinetics of as mobilization or the removal of as by groundwater flushing is the mechanism underlying this relationship in either case the spatial variability of as concentrations in the top 20 m of the shallow aquifers can to a large extent be attributed to groundwater age controlled by the hydrogeological heterogeneity in the local groundwater flow system

decoupling of as and fe release to bangladesh groundwater under reducing conditions part i evidence from sediment profiles this study reexamines the notion that extensive as mobilization in anoxic groundwater of bangladesh is intimately linked to the dissolution of fe oxyhydroxides on the basis of analyses performed on a suite of freshly collected samples of aquifer material detailed sediment profiles extending to 40 to 70 m depth below the surface were obtained at six sites where local groundwater as concentrations were known to span a wide range the sediment properties that were measured include 1 the proportion of fe ii in the fe fraction leached in hot 1 2 n hcl 2 diffuse spectral reflectance and 3 magnetic susceptibility in parallel with local concentrations of dissolved as ranging from 5t o 600g l fe ii fe ratios in shallow gray holocene sands tended to gradually increase with depth from values of 0 3 to 0 5 to up to 0 9 in deeper orange aquifers of presumed pleistocene age that were separated from shallow sands by a clay layer and contained 5 g l dissolved as leachable fe ii fe ratios averaged 0 2 there was no consistent relation between sediment fe ii fe and dissolved fe concentrations in groundwater in nearby wells the reflectance measurements indicate a systematic linear relation r 2 of 0 66 n 151 between the first derivative transform of the reflectance at 520 nm and fe ii fe the magnetic susceptibility of the shallow aquifer sands ranged from 200 to 3600 x 10 9 m 3 kg si and was linearly related r 2 of 0 75 n 29 to the concentrations of minerals that could be magnetically separated 0 03 to 0 79 dry weight no systematic depth trends in magnetic susceptibility were observed within the shallow sands although the susceptibility of deeper low as aquifers was low up to 200 10 9 m 3 kg si

age of initiation of collision between india and asia a review of stratigraphic data abstract the collision of india with asia is perhaps the most profound tectonic event to have occurred in past 100 ma it is responsible for the uplift of the himalayas and tibetan plateau and has been argued to have been responsible for geological geochemical and climatological consequences of global extent yet the age of initiation of this collision remains poorly constrained the literature is replete with estimates that range from the late cretaceous 65 ma to latest eocene

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

soapstone as a locally used and limited sculptural material in remote area of northern moravia czech republic in contrast to nordic countries talc rich rocks massive and schistose talc bearing rocks talcite magnesite talc schists chlorite talc schists and or chlorite actinolite talc schists often loosely classified as soapstone represented practically an unknown natural building and sculptural stone in the czech republic this extraordinary material was quarried and used in the only region of the czech republic where sobotin amphibolite massif sumperk district northern moravia outcrops metamorphosed basic igneous rocks contain small lenses of soapstone that were exploited in the past and used not only for refractory purposes but also as a construction and sculptural material occurrences of sobotin soapstone show distinct zone macrofabric marked by the occurrence of massive soapstone in the core that gradually changes to talc dominant schists later to actinolite tremolite rich schists and finally to chlorite schists at the contact with surrounding amphibolites the most typical sobotin soapstone exhibits high density up to 2 900 kg m 3 low water uptake maximum 0 68 wt favorable dynamic elastic properties p wave velocity 5 340 5 840 m s 1 s wave velocity 2 900 3 300 m s 1 and mechanical properties tensile splitting strength 5 2 6 9 mpa uniaxial compressive strength 17 5 24 1 mpa sobotin soapstone is relatively resistant to weathering action although schistose varieties show typical delamination when exposed to frequent freeze thaw cycling in harsh mountainous environment field survey of monuments architectural and building artefacts made from sobotin soapstone contributed to our knowledge on duration of exploitation of sobotin soapstone that was for sure utilised from the second half of seventeen century till the beginning of the twenty century the most characteristic feature of sobotin soapstone is its strict local use on the territory of about 20 villages surrounding previously exploited soapstone lenses

diminished groundwater recharge and circulation relative to degrading riparian vegetation in the middle tarim river xinjiang uygur western china riparian vegetation in the middle tarim river is being degenerated and groundwater in the riparian system is a key factor controlling this process vegetation degeneration is related to the reduced inflow from the upstream reduced recharge to riparian groundwater lowered water table and increased salinity of the groundwater system systematic chemical and isotopic sampling of river water and groundwater transects perpendicular to the river show that riparian groundwater is fed by the river river water picks up salts from the river bed and or from irrigation returns as it flows downstream and groundwater from riverbank sediments mirror this pattern mineral dissolution and evapotranspiration are the main mechanisms of salt accumulation in groundwater reduced recharge from the river has resulted in a distinctive zoning pattern in groundwater salinity groundwater residence times derived from tritium contents indicate that the extent of modern recharge since the 1960s is limited to approximately 1500 m from the riverbank in the middle reaches of the tarim river vegetation grows better in habitats with modern groundwater than in other areas the embankment built in 2001 along one side of the tarim river appears to have reduced groundwater recharge causing the water table to drop and ecosystem to degenerate copyright c 2009 john wiley sons ltd