channel margins in a pennsylvanian braided fluvial deposit the morien group near sydney nova scotia canada abstract braided fluvial deposits in the pennsylvanian morien group contain an unusual association of erosional features at contacts between sandstone and mudstone units which represent flat lying to vertical channel margins mudstone intraclasts up to 2 m in diameter form lensoid lags at channel bases and are interpreted as bank collapse rubble flutes on vertical channel walls channel floors and intraclasts indicate active flow whereas rills on steep surfaces resulted from downslope drainage over the edges of banks or mudclasts delicate plumose patterns on vertical fracture surfaces modified by flow formed during cracking of the muds by desiccation and bank collapse scoured desiccation cracks are common on flat lying surfaces where flow parallel linear scours 50 cm deep may have expl ited orthogonal desiccation cracks the channel margin features described here require deposition and subsequent reworking of cohesive fines on high topographic levels of a fluvial system due to alternating periods of flooding and subaerial exposure braided and ephemeral river systems with variable discharge are likely to provide the most suitable setting for these features

deformation enhanced fluid distribution in feldspar aggregates and implications for ductile shear zones experiments at 900 c and 1 4 gpa show that the distribution of aqueous fluid in fine grained feldspar aggregates changes from isolated pores under hydrostatic conditions to mostly wetted grain boundaries during deformation the isolated pore distribution is rapidly regained during annealing following deformation the deformation enhanced fluid distribution causes a switch from dislocation creep to diffusion creep accompanied by a significant decrease in strength it also increases the bulk transport rate through the aggregate by more than an order of magnitude a change in fluid distribution is not observed in fine grained quartz aggregates deformed at similar conditions if deformation enhanced fluid distribution occurs in naturally deformed feldspathic rocks it could help to explain the localization of strain and enhancement of bulk transport in ductile shear zones

evolution study of a regional groundwater system using hydrochemistry and stable isotopes in songnen plain northeast china groundwater is often a critical source of water for municipal industrial and agricultural uses especially in arid and semi arid environments songnen plain located in the central part of northeast china is such a region it being an important productive base of commodity grain in this country in the past two decades groundwater quality in the region especially salinization has deteriorated under natural changes and human activities and has become a crucial factor restricting sustainable eco environmental and socio economic development in this paper the taoer river catchment situated in the middle of the region was selected as the study area for the groundwater quality evolution study using hydrochemistry and stable isotopes to obtain a better understanding of the system fifty two groundwater samples were collected with systematic design during the low water and high water periods in 2003 a series of comprehensive quality data interpretations e g statistics ratios of ions and piper diagrams together with stable isotope data have been used to gain an insight into the spatial and temporal variations and evolution laws of groundwater hydrochemistry the following main hydrochemical processes were identified as controlling the water quality of the groundwater system weathering dissolution evaporation condensation ion exchange reactions and groundwater salinization this latter process salinization is the most important process and is caused by the leaching of superficial or near surface salts from the saline alkaline soil into shallow groundwater

dislocation creep regimes in quartz aggregates abstract using optical and tem microscopy we have determined that three regimes of dislocation creep occur in experimentally deformed quartz aggregates depending on the relative rates of grain boundary migration dislocation climb and dislocation production within each regime a distinctive microstructure is produced due primarily to the operation of different mechanisms of dynamic recrystallization at lower temperatures and faster strain rates the rate of dislocation production is too great for diffusion controlled dislocation climb to be an effective recovery mechanism in this regime recovery is accommodated by strain induced grain boundary migration recrystallization with an increase in temperature or decrease in strain rate the rate of dislocation climb becomes sufficiently rapid to accommodate recovery in this regime dynamic recrystallization occurs by progressive subgrain rotation with a further increase in temperature or decrease in strain rate dislocation climb remains sufficiently rapid to accommodate recovery however in this regime grain boundary migration is rapid thus recrystallization occurs by both grain boundary migration and progressive subgrain rotation the identification of the three regimes of dislocation creep may have important implications for the determination of flow law parameters and the calibration of recrystallized grain size piezometers in addition the identification of a particular dislocation creep regime could be useful in helping to constrain the conditions at which a given natural deformation has occurred

evolution of pore microstructures during healing of grain boundaries in synthetic calcite rocks the morphologies of calcite grain boundaries were analyzed to provide insight into the evolution of pore networks in unfractured rock two synthetic calcite rocks were fabricated by hot isostatically pressing hip ing dried analytical grade powders of pure caco3 and caco3 plus 5 al2o3 at 600 c and 200 mpa confining pressure for 3 hours hip 1 some samples were hiped a second time at different temperatures and pressures to investigate the stability of the structures hip 2a c sem and tem were used to image both grain faces and grain boundary cross sections structures on grain faces vary from open shallow basins with peripheral rims to labyrinths of irregular ridges and channels to isolated circular depressions all of these structures are mirrored across the plane between grain faces the grain size in both the single and two phase samples increased markedly during hip 1 migrating boundaries either dragged pores along or broke away leaving grain interiors dotted with small voids the structures present after hip 1 were not stable but evolved considerably in a way dependent on the conditions of the hip 2 confining pressure had the most pronounced effect with low confining pressure the grain boundary porosity evolved into isolated circular depressions but the total pore volume did not noticeably decrease with high confining pressure the pore volume virtually disappeared the structures present after hip 1 are strikingly similar to those that develop in intragranular cracks during healing we infer that grain boundaries and intragranular cracks heal by similar processes decomposition localized melting impurities and anisotropic surface energies played no evident role in forming the grain boundary structures the timing of the formation of the porosity and of the subsequent healing processes is more difficult to ascertain some structures appear to have evolved gradually throughout the constant high temperature stage of hiping the most obvious structures however appear to have evolved on grain boundary cracks that opened during cooling

the interaction of fluid inclusions and migrating grain boundaries in a rock analogue deformation and annealing of polycrystalline camphor ethanol mixtures the results of deformation and annealing experiments using a rock analogue containing a liquid phase as observed in transmitted light microscopy are presented samples were made of camphor ethanol mixtures with the polycrystalline solid being a rhombohedral phase and the liquid a saturated solution of camphor in ethanol results show the in situ pore fluid morphology during grain boundary migration recrystallization samples were deformed at high homologous temperatures th 0 7 and strain rates of 1 10 6 to 9 10 4 s 1 for grain boundary migration rates ranging from 10 10 to 10 6 ms 1 zener pinning not only the drag and drop of fluid inclusions by migrating grain boundaries but also the passage of grain boundaries over fluid inclusions without noticeable interaction was observed the drag limiting migration rate is three times lower for post kinematic annealing than for dynamic recrystallization and shows a weak dependence on fluid inclusion size a detailed description is presented of fluid inclusion grain boundary interaction with respect to fluid inclusion sizes and grain boundary migration rates fluid inclusions show up to 39 reduction in diameter after passage of a grain boundary indicating fluid flow along the mobile grain boundary

assessment of the spatial and temporal hydrochemical facies variation in the flood plains of north west delhi using integrated approach assessment of change in major ion chemistry of groundwater manifested by hydrochemical facies is a necessity for sustainable use of the groundwater resources in this perspective this article estimates spatial and temporal hydrochemical facies variation in the study area using an integrated approach the geochemical isotopic and sedimentary data from the north west delhi has been used to achieve the objective of the study it is seen that the spatial groundwater facies variation in the study area correlates with the change in geomorphologic units distinct hydrochemical facies for younger and older alluvial plains has been observed it is seen that geomorphic features such as palaeochannels also influence the groundwater quality of the study area further the temporal hydrochemical facies variations indicate that with time anthropogenic factors have also impacted the evolution of facies in the study area

hydrochemistry and contamination of groundwater resources in the behbahan plain sw iran the behbahan plain with an area of 1320 km2 is located in an arid to semi arid zone since it has restricted water resources the preservation of groundwater quality is of great importance in order to investigate the contamination possibility which could be resulted from geogenic and anthropogenic sources 30 wells were sampled during august 2014 the water samples were analyzed for heavy elements as cd fe mn zn sr pb se co b and cr anions cl so42 hco3 co3 no3 cations ca2 k mg2 and na and important quality parameters including ph ec and tds using icp oes faes oas titration conductometry and drying methods the concentration of major ions in most of the samples exceeds the allowed levels of who standard for drinking water geochemical data show that the water chemistry is influenced dominantly by weathering and dissolution of carbonate and evaporitic minerals ion exchange processes and human activities groundwater in the behbahan plain is mainly of calcium sulfate facies according to piper diagram the concentrations of nitrate and k show little correlation with that of major ions suggesting unnatural sources for them these components originated possibly from dissolution of nitrate and k bearing fertilizers used in farming geochemical maps indicate that concentration of toxic trace elements such as pb cd cr b as and those of so42 no3 cl and na ions have incremental trends these high concentrations are caused probably by domestic and industrial waste waters leaked into the groundwater aquifer the heavy metal pollution index hpi in 29 samples is greater than 100 indicating that groundwater in the study area is highly polluted with heavy elements

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

the rates and extent of textural equilibration in high temperature fluid bearing systems abstract the geometry of fluid filled pores in texturally equilibrated aggregates can in theory be uniquely determined given the porosity and the equilibrium dihedral angle for all possible orientations and combinations of the constituent solid phases while it is useful to be able to do this one should also ask whether and to what extent textural equilibrium is actually attained during fluid present intervals in high temperature rocks in fact textural equilibrium may be only rarely attained during melting of crustal rocks and equilibration under mid ocean ridges is possibly incomplete to depths as great as the garnet stability zone there is very little published information on the rates of attainment of textural equilibrium in fluid bearing geological environments the available experimental data for the rates of growth of equilibrated domains are consistent with a power law relationship between domain size and equilibration time with an exponent between 2 and 3 a simplified theoretical treatment of pore shape change governed by the gibbs thompson relationship demonstrates that an exponent of 3 is to be expected for equilibration by diffusion within the fluid phase with an effective diffusivity consistent with the available data

origin of shore normal channels from the shoreface of sable island canada a suite of modern shore normal channels was discovered on the southern shoreface of sable island canada repetitive multibeam and sidescan surveys of these features as well as box coring and sampling showed that the depressions were perennial features of the shoreface they occurred in fine and medium sand and were most abundant in depths less than 20 m they were up to 1 m deep and 50 m wide increased in size seawards and generally followed the seabed slope the channels dominated the inner shoreface becoming wider and deeper seawards to depths in excess of 40 m there is a continuum of scales in width and depth of these channels the smallest of which are equated with gutters preserved in the geological record the internal structure of the shoreface sediments where the gutters are found is characterised by normally graded tempestites composed of cut and fill structures overlying an erosion surface thus the environmental setting internal structure and scale are similar to ancient counterparts gutters have been interpreted to result from downwelling over palaeo shorefaces during ancient storms myrow 1992b the composition of gutter infill as well as the stability evolution associated bedforms and hydrodynamic conditions under which they formed were examined to verify genetic interpretations of the ancient counterparts the multi sensor benthic lander ralph was deployed within a field of shore normal channels for 17 days during late winter 1998 ralph burst sampled flow at hourly intervals whilst imaging the seabed resulting sequential imagery revealed the genesis of a group of five gutters during storm spin down that was coincident with the formation of large scale wave ripples this was followed by infilling of the gutters and wave ripple destruction within 20 hours by longshore sand transport the gutters were located within and parallel to a larger channel 50 m wide and 0 50 m deep they were formed by coastal set up and subsequent downwelling that was triggered by the rotation of storm winds from seawards onshore wind to landwards offshore wind the gutters formed within 2 to 3 hours during spin down of a winter storm under live bed conditions of sand transport wave height and mean tidal flows were well below those of the storm peak and so they were not directly responsible for creating the gutters the mechanism we propose for the evolution of gutters supports the geological interpretations that is a storm driven downwelling event as described by swift and niedoroda 1985 however the downwelling event appeared to take place suddenly rapid acceleration in flow briefly few hours duration and within narrow corridors guided by wider and deeper channels of the shoreface high turbidity during the time of gutter formation leads us to believe that the phenomenon of inner shelf turbidity currents as suggested by walker 1985 exists and may be instrumental in channel formation

disequilibrium melt distribution during static recrystallization melt migration and segregation and the rheology of partially molten rocks in the upper mantle and lower crust strongly depend on the grain scale distribution of the melt current theory for monomineralic aggregates predicts a perfectly regular melt framework but high temperature experiments with rock forming minerals melt show considerable deviations from this predicted geometry disequilibrium features such as fully wetted grain boundaries and large melt patches have been described these were mainly attributed to surface energy anisotropy of the minerals we present static analogue experiments with norcamphor ethanol that allow continuous in situ observation of the evolving liquid distribution the experiments show that all previously reported disequilibrium features can form during fluid enhanced static recrystallization when small grains are consumed there is no need to invoke surface energy anisotropy although this might enhance the effect all disequilibrium features are transitory and evolve back toward equilibrium geometry however because the system undergoes continuous static recrystallization disequilibrium features are always present in a partially molten polycrystalline aggregate and therefore control its properties

microstructural observations on natural syntectonic fibrous veins implications for the growth process abstract syntectonic antitaxial and ataxial fibrous veins were investigated using sem microprobe cathodoluminescence cl and optical microscopy in antitaxial calcite veins fibres and surrounding selvage grew simultaneously with similar growth rates of crystallographically differently oriented grains new material precipitated at the vein margin in antitaxial and bi mineralic ataxial microstructures bridges of country rock material formed during vein growth in an initial en echelon vein system in our antitaxial and bi mineralic ataxial samples the spacing of solid inclusions does not reflect individual crack seal openings

appraisal and evolution of hydrochemical processes from proximity basalt and granite areas of deccan volcanic province dvp in india summary this paper deals with a systematic hydrochemical study carried out at proximity basalt and granite areas of deccan volcanic province dvp in india to assess groundwater quality and evaluate the hydrochemical processes a total of 40 groundwater samples were collected equally from these areas and analyzed results showed that the groundwaters rich in alkaline earth in the basalt and alkali rich element in the granite the dominancy of cations was observed as ca 2 mg 2 na k in the basalt and na mg 2 k ca 2 in the granite whereas anions as hco 3 cl so 4 2 and cl hco 3 so 4 2 respectively hydrochemical processes were identified with the helps of ion exchange carbonate weathering and dissolution multiple ionic ratios and silicate weathering which shown the predominance of carbonate dolomite calcite and silicate anorthite weathering in basalt but in granite silicate alkali feldspar weathering was dominated factor analysis also showed that there were multiple processes acting on groundwaters were separated from the main cluster salinity sodium absorption ratio sar soluble sodium percentage ssp residual sodium carbonate rsc kelley s ratio kr and permeability index pi in well samples showed that groundwater in basalt was more suitable for irrigation purposes further a digital elevation model dem was generated using global mapper 8 0 version software which aided to decipher the thickness of basalt trap and vertical transition zone of basaltic trap and granitic basement aquifer at this dvp comprising with the well depths and groundwater chemistry

origin and dynamics of groundwater salinity in the alluvial plains of western delhi and adjacent territories of haryana state india groundwater salinity is a widespread problem and a challenge to water resources management it is an increasing concern in the alluvial plains of delhi and neighbouring haryana state as well as a risk for agricultural production water supply and sustainable development this study aims to identify potential sources of dissolved salts and the driving mechanisms of salinity ingress in the shallow aquifer it combines a comprehensive review of environmental conditions and the analysis of groundwater samples from 25 sampling points major ions are analysed to describe the composition and distribution of saline groundwater and dissolution precipitation dynamics density stratification and local upconing of saline waters were identified by multilevel monitoring and temperature logging bromide chloride ratios hold information on the formation of saline waters and nitrate is used as an indicator for anthropogenic influences in addition stable isotope analysis helps to identify evaporation and to better understand recharge processes and mixing dynamics in the study region the results lead to the conclusion that surface water and groundwater influx into the poorly drained semiarid basin naturally results in the accumulation of salts in soil sediments and groundwater human induced changes of environmental conditions especially the implementation of traditional canal and modern groundwater irrigation have augmented evapotranspiration and led to waterlogging in large areas in addition water level fluctuations and perturbation of the natural hydraulic equilibrium favour the mobilisation of salts from salt stores in the unsaturated zone and deeper aquifer sections the holistic approach of this study demonstrates the importance of various salinity mechanisms and provides new insights into the interference of natural and anthropogenic influences copyright 2011 john wiley sons ltd

stable isotopic and geochemical characteristics of groundwater in kherlen river basin a semi arid region in eastern mongolia summary inorganic solute ion concentrations and stable isotopes of oxygen and hydrogen in groundwater river water and precipitation were investigated to gain insight into the groundwater recharge process in the kherlen river basin a semi arid region in eastern mongolia the solute constituents in the river water main stream were of ca hco3 type spatially invariant and low in concentration groundwater in the upstream region was also characterized by a ca hco3 type though all ion concentrations were higher than in the river water on the other hand the chemical composition of the groundwater in the midstream region southern and eastern was spatially variable and the na mg2 cl and hco 3 concentrations were considerably higher than in the river water and upstream groundwater the stable isotopic compositions showed an evaporation effect on the groundwater and river water as well as an altitude effect in the precipitation and river water preferential recharge by relatively large rainfall events is thought to have caused the depleted isotopic ratio in the groundwater in the dry regions the stable isotope chemical and hydrological data suggest that the main stream water of the kherlen river is recharged by precipitation that falls in a headwater region at an altitude of more than 1650 m and that the interaction between the groundwater and river water is not dominant in the midstream and downstream regions of the river basin

late pleistocene precipitation δ18o interpolated across the global landmass global water cycles ecosystem assemblages and weathering rates were impacted by the 4 c of global warming that took place over the course of the last glacial termination fossil groundwaters can be useful indicators of late pleistocene precipitation isotope compositions which in turn can help to test hypotheses about the drivers and impacts of glacial interglacial climate changes here a global catalog of 126 fossil groundwater records is used to interpolate late pleistocene precipitation 18o across the global landmass the interpolated data show that extratropical late pleistocene terrestrial precipitation was near uniformly depleted in 18o relative to the late holocene by contrast tropical 18o responses to deglacial warming diverged late pleistocene 18o was higher than modern across india and south china but lower than modern throughout much of northern and southern africa groundwaters that recharged beneath large northern hemisphere ice sheets have different holocene pleistocene 18o relationships than paleowaters that recharged subaerially potentially aiding reconstructions of englacial transport in paleo ice sheets global terrestrial late pleistocene precipitation 18o maps may help to determine 3 d groundwater age distributions constrain pleistocene mammal movements and better understand glacial climate dynamics

grain growth and inclusion formation in partially molten carbonate rocks to learn more about the kinetics and mechanisms of coarsening and melt inclusion formation we investigated the effects of melt content viscosity and topology on the microstructural evolution of partially molten and melt free calcite aggregates synthetic marbles with eutectic melts were produced by annealing mixtures of calcite and either calcium hydroxide or lithium carbonate for up to 80 h at a confining pressure of 300 mpa and temperatures of 973 1 023 k the melts produced in the two systems are expected to differ significantly in viscosity generally coarsening rates decrease with increasing melt fraction probably because the diffusion length across melt pockets increases analysis of grain shapes in the samples with about 40 melt indicated that coarsening was accommodated by agglomeration in the samples of the calcium lithium carbonate system in the calcium carbonate hydroxide system classical ostwald ripening occurred for melt contents about 10 and below melt filled pores are either dropped from or dragged along with migrating grain boundaries depending on the pore size and the grain boundary curvature these data can be used to constrain the conditions where fluid or melt inclusions form under natural conditions combining our results and previous studies illustrates a systematic relation between the grain boundary mobility in calcite aggregates and the diffusion kinetics associated with second phases residing on the grain boundaries in particular boundaries with no porosity are most mobile those boundaries dragging melt filled pores are slower those with gas filled pores are slower yet and those containing solid phases are slowest or may even be motionless

deformation mechanisms in second phase affected microstructures and their energy balance based on the relationship zener parameter z second phase size second phase volume fraction vs calcite grain size dg second phase controlled aggregates and microstructures that are weakly affected by second phases are discriminated the latter are characterized by large but constant grain sizes high calcite grain boundary fractions and crystallographic preferred orientations cpo while calcite grain size and calcite grain boundary fraction decrease continuously and cpo weakens with decreasing z in second phase controlled microstructures these observations suggest that second phase controlled microstructures predominantly deform via granular flow because pinning of calcite grain boundaries reduces the efficiency of dynamic recrystallization favoring mass transfer processes and grain boundary sliding in contrast the balance of grain size reduction and growth by dynamic recrystallization maintains a steady state grain size in microstructures that are only weakly affected by second phases promoting a predominance of dislocation creep with increasing temperature the relationship between z and dg persists but the calcite grain size increases continuously based on microstructures the energy of each modifying process is calculated and its relative contribution is compared with energies of the competing processes surface energy dragging energy dynamic recrystallization energy the steady state microstructures result from a temperature dependent energy minimization procedure of the system

the preservation potential of microstructures during static grain growth grain growth simulations using the microstructure simulation system elle have been performed in materials with a pre existing grain shape foliation as might be expected the foliation is destroyed by the end of the experiment and grain areas have increased by a factor of seven the area of material swept by the migrating grain boundaries was monitored and it was found that at every stage virtually all of the grains which survived the grain growth process contain one and only one core of unswept material remarkably these remnant unswept cores preserve a useable record of the initial grain size and the orientation of the grain shape foliation this work suggests that even for samples where no equivalent protolith can be found it may be possible to see past a grain growth episode to estimate the original grain shape and grain size of the rock and perhaps even reconstruct the grain boundary kinematics in addition the identification of unswept cores has the potential to help unravel the evolution of grain boundary chemistry in rocks during metamorphism as an example of a natural system showing these microstructures we describe a peridotite from almklovdalen norway this peridotite was infiltrated by aqueous fluids at several stages during late caledonian exhumation and retrogressive metamorphism grain boundary migration associated with the last of these infiltration events swept off abundant intragranular fluid inclusions in the original chlorite peridotite at the grain scale microstructural mapping of the fluid inclusion rich areas shows that as with the numerical simulations many of the grains retain exactly one core of unswept material examples of other natural systems discussed include dislocation density distributions and trace element zoning

an sem study of porosity and grain boundary microstructure in quartz mylonites simplon fault zone central alps a backscattered and secondary electron sem study of the grain boundary microstructure in quartz mylonites sampled along the length of the retrograde simplon fault zone established three characteristic components 1 fine isolated pores 1 m diameter are scattered across two grain interfaces preferentially concentrated on surfaces in extension pores are uncommon on three grain junctions and there is no evidence for fluid interconnectivity along three and four grain junctions the fine porosity may develop by accumulation of original mainly intragranular fluid inclusions to the grain boundary during deformation and recrystallization and by cavitation of grain boundaries during grain boundary sliding dynamic cavitation implies that the ductile mylonitic deformation is at least locally dilatant and therefore pressure sensitive 2 large vug like pores up to mm scale extend along multi grain boundaries observed in all samples they are most common in the higher initial temperature coarse grained samples with a microstructure dominated by grain boundary migration recrystallization grains bordering this connected porosity develop perfect crystal faces undecorated by fine pores or pits the irregular lobate optical microstructure of many migrating grain boundaries actually consists of a series of straight crystal faces the coarse porosity is probably due to accumulation during dynamic recrystallization of co2 rich fluid with a high wetting angle against quartz 3 in one sample interconnected sinuous ridges 0 2 m high are observed to follow three and four grain junctions and disjoint into more isolated worms and spheroidal globules on two grain interfaces these are transitional to more branching vein like or convoluted brain like forms the brain like and globular forms have been observed with varying frequency through the range of samples with the globules attaining sizes of up to 60 m vein structures have also been observed on intragranular fractures these topologies do not match across adjoining surfaces and must have developed into free space the ridge vein brain spheroid structure is distinctly different to that previously observed on experimentally healed microcracks and its origin is not unequivocally established they could represent unstable meniscus necking of a thin grain boundary phase of low viscosity developed due to quasi adiabatic shear and or local stress induced dilatancy during microcracking

landscape and depositional controls on palaeosols of a distributive fluvial system upper cretaceous brazil abstract the stratigraphic record of distributive fluvial systems is commonly characterised by frequent and complex interstratification of palaeosols among channel and overbank deposits however current models focus primarily on sedimentation and pay only limited attention to palaeopedogenesis thereby failing to incorporate important palaeoenvironmental and stratigraphic information this study proposes a pedosedimentary model for distributive fluvial systems that depicts and accounts for two palaeopedogenetic trends one downdip in relation to distality from the fan apex and one along strike in relation to distance from active channel belts palaeosols are reported in detail from an upper cretaceous succession of the bauru basin southeastern brazil through the application of macro micromorphological and geochemical studies combined with facies and architectural element analyses of sediments in the downdip palaeopedogenetic trend the proximal zone of the depositional system is characterised by a dominance of well drained inceptisols that develop on amalgamated channel fills in the medial zone inceptisols occur interlayered with overbank deposits containing entisols and poorly drained vertisols the distal zone preserves more mature and poorly drained inceptisols developed on deposits of overbank and sporadic distal channel fills these pedotypes show an increase in maturity and hydromorphism moving away from the apex to the fan toe this is likely linked to i the progressive approach of the topographic surface to the water table and ii the average increase in distance to an active channel belt in distal locations the along strike palaeopedogenetic trend culminates in poorly developed palaeosols in floodplain regions that correspond to topographic depressions located between channel belts and which were subject to recurrent floods because palaeopedogenesis in the floodplain region is penecontemporaneous to sedimentation pedotypes show an increase in maturity bioinduced calcification and hydromorphism with distance from the active channels they pass laterally from entisols and inceptisols near active channels to vertisols away from active channels conversely following avulsion abandoned channel belts remain as topographically elevated alluvial ridges located at some distance from the newly active channels and positioned above the water table and this leads to the development of better drained and better developed inceptisols relative to pedotypes of the floodplain region overall both palaeopedogenetic trends demonstrate the overriding controls of topography sedimentation rate and parent material on pedogenesis with only minor climatic influence this work offers a novel pedosedimentary model for distributive fluvial systems and highlights the palaeoenvironmental significance of palaeosol trends providing new constraints for the recognition of distributive fluvial systems in the rock record

18o studies on recharge of phreatic aquifers and groundwater flow paths of mixing in the delhi area widespread decline in the groundwater level and growth of salinization are the critical factors controlling future groundwater quality and availability in the delhi area s180 and salinity data have been integrated for studying recharge conditions of phreatic aquifers and tracing the flowpaths of groundwater mixing wide range 2 8 0 to 8 6 and spatial inhomogeneity of 6180 in groundwater indicate that the aquifer is characterized by a slow process of natural mixing of groundwater in its lateral extent there is infiltration of river water to the groundwater in addition to the recharge from rainfall groundwater recharge in the area also occurs through stagnant water pools in low elevation areas where water surface run off collects chloride concentration in groundwater has a wide range from 15 ppm to 5070 ppm with a log normal frequency distribution indicating that the salt deposits in the area are not homogeneously distributed the s180 c1 relationship clearly suggests mixing of multiple sources of high salinity groundwater with low salinity groundwater or river water along specific pathways the data also indicates leaching of salts present in the soil during vertical recharge from rainfall and irrigation large lateral variation in chloride concentration indicates changes in evapotranspiration rate during recharge detailed investigations on identifying the potential recharging zones flow paths of mixing and recharge conditions will be useful to protect the groundwater resources from depletion and salinization

the analysis of progressive deformation in rock analogues abstract two dimensional deformation experiments using analogue materials such as octachloropropane and camphor have proven to be a powerful tool in the investigation of microstructural development since they make it possible to observe the specimen throughout its deformation history the addition of dispersed marker particles makes it possible to trace the movement of material points during deformation from this information the flow and deformation can be interpolated for any point within the specimen at any time the geometry of the flow and deformation can then be visualized in the form of grids contour plots strain ellipses and other methods despite this apparently ideal setting for studying flow and deformation the need to use marker particles to trace material points introduces unexpected problems in the analysis we present a computer program to analyse the movement of marker particles digitization of the positions of the particles is improved by the use of video input and semi automatic digitization the use of polynomials to describe the complete path of marker particles and least squares best fit solving improves the analysis of the data

tectonic control on the sequence stratigraphy of nonmarine retroarc foreland basin fills insights from the upper jurassic of central utah u s a abstract continental successions of the north american western interior retroarc foreland basin provide an excellent opportunity to evaluate the tectonic controls on nonmarine sequence stratigraphy the transition between the upper jurassic brushy basin member anastomosed fluvial system of the morrison formation and the gravelly braided river deposits of the buckhorn conglomerate has been studied to assess the dispersal of coarse clastics and the development of associated basin wide unconformities in a sequence stratigraphic framework the sharp contact between the two members is interpreted to be conformable based on stratigraphic sedimentologic and petrologic data collected at and near cedar mountain in central utah while a regional mature paleosol at the top of the buckhorn conglomerate indicates the presence of a major sequence boundary these interpretations are combined with paleoflow data and fluvial architectural analysis to reconstruct the evolution of the alluvial equilibrium profiles that controlled deposition of the succession the buckhorn conglomerate is interpreted as an example of a post orogenic deposit on the basis of 1 its tabular geometry 2 distance from the contemporaneous thrust belt 3 shift to transverse paleoflow direction from the preceding brushy basin axial drainage 4 conformable lower contact and 5 presence of an overlying sequence boundary with a westward expanding hiatus eroding the coeval foredeep the onset of a protracted period of low rate of orthogonal convergence between the farallon and north american plates resulted in tectonic quiescence and consequent isostatic rebound of the middle to late jurassic thrust belt and the contiguous contemporaneous foredeep as well as dynamic uplift the ensuing basin wide decrease in subsidence rate induced the progradation of the buckhorn alluvial plain into the morrison back bulge depozone and the subsequent generation of the overlying pedogenic unconformity which separates the deposits of the jurassic flexural event from the overlying sevier tectonostratigraphic unit

geochemical modelling ionic ratio and gis based mapping of groundwater salinity and assessment of governing processes in northern gujarat india in semi arid arid regions groundwater is the major source of irrigation drinking and industrial requirements water salinity and shortage are major problems of concern north gujarat india is one such area where highly saline groundwater is generally ascribed to rapid increase of population agriculture and industries induced decline in water table by unplanned abstraction of groundwater however no effort has been made to discriminate the natural and anthropogenic influences on groundwater salinity in this brief background the present study attempts to identify the factors and processes controlling the groundwater salinity in the area based on ionic ratios in integration with various graphical methods saturation indices and geographical information system na ca2 1 indicates the deficiency of ca2 possibly due to caco3 precipitation or ion exchange process na cl 1 and text so 4 2 text cl gg 0 05 suggest salinization is mainly due to wastewater infiltration and or due to irrigation water return flow sea water intrusion in coastal parts vertical and lateral mixing of water and anthropogenic inputs are also responsible for salinization of groundwater ussl diagram na sodium adsorption ratio residual sodium carbonate and magnesium hazard indicate unsuitability of groundwater for irrigation purposes to prevent groundwater salinization appropriate measures need to be taken to control further indiscriminate exploitation of groundwater for irrigation

sedimentology and mineral composition of the kurnub sandstone in wadi qsieb sw jordan abstract the kurnub sandstone of early cretaceous age crops out in wadi qsieb in the southwest of jordan with a thickness of 130 m moderately developed fining upward cycles with irregular erosive bases together with the presence of plant fragments and the absence of body or trace fossils point to a fluviatile depositional environment probably a river of intermediate sinuosity results of grain size analysis confirm this interpretation the sandstones are compositionally and texturally supermature quartz arenites formed mainly by recycling from early palaeozoc sandstones and less commonly by direct supply from the arabian nubian shield the absence of feldspars and unstable heavy minerals is attributed to intense chemical weathering attacking sands that were deposited with a low rate on a craton bordering the tethys sea the thickness recorded here and the absolute absence of hornblende are in contradiction with what has been published by nasir and sadeddin 1989

groundwater quality assessment and its suitability in celtikci plain burdur turkey the celtikci burdur plain is located in the southwest of turkey and is a semi closed basin groundwater is densely used as drinking irrigation and domestic water in the plain hydrogeochemical processes controlling groundwater chemistry and geochemical assessment of groundwater were investigated in the celtikci burdur turkey plain in this study groundwater samples for two seasons were analyzed and major ion chemistry of groundwater was researched to understand the groundwater geochemistry two major hydrochemical facies ca hco3 and ca mg hco3 were determined in the area various graphical plots and multivariate statistical analysis were used for identifying the occurrence of different geochemical processes in the study area weathering is one of the key geochemical processes which controlled the solute concentration in groundwater chemical indexes such as sodium adsorption ratio na residual sodium carbonate magnesium hazard and permeability index were calculated and results show that groundwater is suitable for irrigation purpose except for permeability index values concentrations of mn no3 and total hardness exceed the prescribed limits of who and are the major limiting parameters of groundwater use for potable and domestic purposes

origin of major dissolved ions in groundwater within the lower pra basin using groundwater geochemistry source rock deduction and stable isotopes of 2h and 18o hydrochemical and stable isotopes 18o and 2h analyses of groundwater samples were employed to establish the origin of major dissolved ions in groundwater within the lower pra basin results showed that the major processes responsible for chemical evolution of groundwater include silicate sio4 4 dissolutions ion exchange reactions sea aerosol spray and pyrite fes2 and arsenopyrite feass oxidations the groundwater is strongly acidic to neutral with ph generally range from 3 5 to 7 0 ph units and mean 5 9 0 5 approximately 89 of boreholes had ph values outside the world heath organization who guidelines for drinking water quality 2004 guideline value for drinking water due principally to natural biogeochemical processes and therefore not suitable for potable purposes electrical conductivity ec range from 57 6 to 1 201 s cm with mean 279 3 198 8 s cm total dissolved solids tds range from 32 to 661 mg l with mean 151 7 106 8 mg l with 98 6 of groundwater as fresh tds ca2 mg2 k and hco3 cl so4 2 respectively a plot of 18o against 2h showed that ground and surface waters clustered on or closely along the global meteoric water line suggesting that the waters emanated principally from meteoric source with evaporation playing an insignificant role on the infiltrating water

fluid inclusion record of the hypozonal orogenic renco gold deposit zimbabwe during the retrograde p t evolution the hypozonal renco gold deposit in zimbabwe is hosted by a shear zone system cutting granulite facies enderbites the geologic history of the region testifies to a polyphase tectonometamorphic evolution along the exhumation path three major events are notable during which fluid inclusions could have been formed detailed petrographic work and comparison of calculated isochores with the p t evolution allows correlation of inclusion formation with the tectonometamorphic evolution fluid inclusions in the mineralized lithologies of the renco gold mine are dominated by carbonic inclusions of highly variable densities the high density carbonic inclusions are related to the peak of metamorphism their lower density counterparts show a bimodal occurrence some are re equilibrated equivalents of the inclusions trapped at peak metamorphic conditions whereas others clearly post date this event and are related to gold mineralization the latter type of carbonic inclusions occurs in distinct microstructural domains of quartz crystals i e subgrain grain boundaries therefore these inclusions are interpreted to have formed because of selective trapping of co2 from a mixed h2o co2 low salinity ore fluid all the aqueous inclusions observed at renco can be attributed to a late retrograde greenschist facies overprint

liquid distribution and attainment of textural equilibrium in a partially molten crystalline system with a high dihedral angle liquid phase the evolution of a high dihedral angle liquid in a crystalline matrix such as fe s melt in an olivine matrix is of vital importance for a range of questions including planetary core mantle differentiation we performed hydrostatic in situ analogue experiments on norcamphor h2o liquid and high temperature experiments on olivine fes melt to investigate the evolution of the liquid and the attainment of textural equilibrium in the liquid and the solid the liquid distribution was dominated by large unconnected liquid pools smaller melt lenses and the regular occurrence of dry three grain triple junctions compared to low dihedral angle systems the liquid pockets had a very low mobility during grain growth and disequilibrium features such as elongated liquid pools only reequilibrated slowly the results have several consequences for the evolving microstructure 1 immobile liquid pockets hinder grain boundary migration and promote abnormal grain growth 2 the attainment of textural equilibrium in solid liquid regions is delayed with respect to liquid free regions 3 grain growth does not promote liquid pocket growth as in low dihedral angle systems and liquid pockets do not directly interact with each other during annealing 4 an existing liquid network is unstable and pinches off in the long term even if the liquid fraction is above the theoretical percolation threshold with regard to this final point percolative core mantle differentiation through an interconnected melt network may not be a viable mechanism even above the suggested percolation threshold of 5 vol

the development of shear zones in polycrystalline camphor urai j l and humphreys f j 1981 the development of shear zones in polycrystalline camphor in g s lister h j behr k weber and h j zwart editors the effect of deformation on rocks tectonophysics 78 677 685 thin polycrystalline specimens of rhombohedral camphor have been deformed in pure shear in the temperature range 283 343k the deformation processes dynamic recrystallization and the development of microstructure were followed by transmission polarized light microscopy when the stress distribution in the specimens was favourable shear zones were initiated the development of microstructure changed drastically above 310320k the shape of the dynamically recrystallized grains which was equiaxed below this temperature became strongly elongated this change probably due to the development of a marked anisotropy in grain boundary mobilities and the activation of new slip systems made the development of shear zones a more frequently occurring phenomenon above 310 320k

an assessment of groundwater salinization in haryana state in india using hydrochemical tools in association with gis unplanned abstraction of groundwater due to various land use land cover activities and variations in monsoonal rainfall have greatly affected the availability and quality of groundwater resources in semi arid regions of india in the present study a study of the hydrogeochemical characteristics of groundwater was undertaken in the sonipat district of haryana in india together with the use of stable isotope 18o and d measurements and gis analysis a total of 53 groundwater samples were collected from seven blocks of the district and 14 water quality parameters and stable isotopes 18o and d were analysed to infer hydrogeochemical processes taking place in the area the integration of hydrochemistry with gis is very helpful to understand the factors governing in the area the majority of the samples showed na cl type of hydrochemical facies the trilinear plot for major cations and anions in groundwater indicates dominance of sodium calcium chloride and bicarbonate ions nitrate plumes in the groundwater appear to be migrating in groundwater from the central and south western parts of the area towards the urbanized areas a total of 64 of the samples exceed the maximum permissible limit of 1 5 mg l given by who for fluoride besides natural sources such as silicate and carbonate weathering ion exchange and reverse ion exchange the leaching of surficial salts and untreated industrial wastes along with unregulated abstraction are contributing to poor groundwater quality in the study area an assessment of saturation indices has shown that groundwater in the area is unsaturated with respect to anhydrite halite and gypsum suggesting significant contribution of ca2 mg2 and other ions in the groundwater a scatter plot of 18o versus cl also suggests mixing of saline water with fresh groundwater

deuterium and oxygen 18 studies in groundwater of the delhi area india abstract groundwater in the delhi area occurs under different hydrogeological conditions west of the delhi ridge closed basin of chattarpur between the ridge and the yamuna river and east of the yamuna river with depth to the water table ranging from 1 53 to 19 12m below ground level a comparison of isotopic data of groundwater with that of rainfall during the period 1961 1978 indicates that groundwater in all the subbasins and at different depths is of meteoric origin having undergone direct evaporation and is genetically similar deviation of the points from the meteoric line on a d 18o diagram is attributed to evaporation from falling rain drops and retardation in infiltration rate of rainwater the latter due to the predominance of clayey soils at several places the present study has shown that the major sources of high salinity are high rate of evaporation recycling of irrigation water and re solution of precipitated minerals by monsoon recharge along with nonflushing of deeper waters this is contrary to the findings of earlier workers who proposed that the high salinity of groundwater is related to marine origin and or fallout of airborne salts from the arabian sea

microstructural evolution of deformation modified primary halite from the middle triassic rot formation at hengelo the netherlands the microstructure of halite from the subhorizontal bedded main rot evaporite member at hengelo the netherlands akzo well 382 depth interval of 420 460 m was studied by transmitted and reflected light microscopy of gamma irradiation decorated samples primary microstructures compare favourably with those found in recent ephemeral salt pans large blocky fluid inclusion poor halite grains and elongated chevrons are interpreted to have formed in the saline lake stage while void filling clear halite is interpreted to have formed during the desiccation stage of the salt pan in addition in all layers the grains are rich in deformation related substructures such as slip bands and subgrains indicating strains of a few percent the study of gamma irradiation decorated thin sections shows that the main recrystallization mechanism is grain boundary migration grain boundary migration removes primary fluid inclusions and produces clear strain free new grains differential stresses as determined by subgrain size piezometry were 0 45 0 97 mpa the deformation of the salt layers is probably related to cretaceous inversion in the area

a few remarks on the kinetics of static grain growth in rocks static grain growth is a relatively simple transformation in which grain size increases under driving forces caused by grain and interphase boundary curvature given the relative simplicity of the protocol for grain growth experiments measurements of grain boundary mobility show surprising variations boundary mobilities during grain growth are affected by solute and impurity chemistry chemical fugacity of trace and major elements pore size and number pore fluid chemistry the presence of melts and the presence of solid second phases as well as temperature and pressure all of these factors may exert influence on grain growth of rocks in natural situations and many are also present during the laboratory experiments provided that the necessary kinetics parameters are known bounds may be placed on the interface mobility when pores partial melts or solutes are present to predict the rate of grain growth in natural situations will require improved laboratory data and careful consideration of the thermodynamic conditions likely to be encountered in nature

the influence of grain boundary fluids on the microstructure of quartz feldspar mylonites quartz rich domains in pre alpine water deficient amphibolite facies 510 580 c 250 450 mpa pegmatite mylonites from mont mary mm western alps preserve a fine dynamically recrystallized grain size without significant annealing despite the high synkinematic temperatures and subsequent static greenschist facies alpine overprint the microstructure is dramatically different from more typical water rich amphibolite facies mylonites such as from the simplon fault zone in the central alps where the recrystallized grain size is on the millimetre scale the difference reflects the dominant strain induced recrystallization mechanism 1 progressive subgrain rotation and grain boundary bulging for the dry mm examples and 2 fast grain boundary migration for the wet simplon examples the grain boundary microstructure imaged with sem is also very different with most grain boundaries in the dry mm samples lacking porosity whereas grain boundaries in the wet samples are decorated by a multitude of pores quartz grain boundaries from both wet and dry samples are locally coated by thin 100 s of nanometres possibly amorphous silica films despite the differences in microstructure the crystallographic preferred orientations cpos of quartz rich domains from both areas are very similar water deficient conditions hinder grain boundary mobility and thereby modify the dominant recrystallization mechanism s but apparently have little influence on the intracrystalline slip systems as reflected in the cpos strong c axis y maxima in mm mylonites both k feldspar and plagioclase an33 38 dynamically recrystallize consistent with the inferred metamorphic conditions under water deficient conditions mid to lower crustal rocks can deform heterogeneously under transitional ductile brittle conditions at high differential stress for mm ca 300 500 mpa as estimated for dry mohr coulomb failure and preserve this high stress microstructure because of the low mobility of dry grain boundaries

water enhanced dynamic recrystallization and solution transfer in experimentally deformed carnallite cylindrical samples of polycrystalline carnallite kmgcl3 6h2o were deformed in a triaxial apparatus at 60 c at confining pressures between 0 1 and 31 mpa and at strain rates between 10 4 and 10 8 s 1 in a number of cases small amounts of saturated carnallite brine were added samples without added brine deform by intracrystalline slip mechanical twinning cracking and by frictional sliding on crack surfaces stress strain curves of these samples are strongly dependent on confining pressure addition of brine has a dramatic effect on both microstructural development and mechanical properties grain boundary migration is strongly enhanced at lower strain rates additional intracrystalline effects start to appear together with the onset of solution transfer rapid compaction in samples deformed with added brine causes high fluid pressures to develop at higher strain rates addition of brine results in a decrease of the flow stress by a factor of two this weakening will increase even further at strain rates below about 10 9 s 1 when solution transfer becomes rate controlling it is argued that deformation of carnallite in nature is adequately described by the flow law found for samples deformed with added brine

grain growth in synthetic marbles with added mica and water evolution of grain size in synthetic marbles was traced from compaction of unconsolidated powder through primary recrystallization and normal grain growth to a size stabilized by second phases to form the marbles reagent grade caco3 was mixed with 0 1 and 5 volume mica and heat treated under pressure with added water densification with negligible recrystallization occurred within one hour at 500 c and 500 mpa confining pressure primary recrystallization occurred at 500 550 c causing increases of grain size of factors of 2 5 resulting samples had uniform grain size gently curved grain boundaries and near equilibrium triple junctions they were used subsequently for normal grain growth studies normal grain growth occurred above 550 c at 800 c grain size d increased from 7 m d0 to 65 m in 24 hours growth rates fit the equation d n d 0 n kt where k is a constant and n 2 6 minor amounts of pores or mica particles inhibit normal grain growth and lead to a stabilized grain size dmax which depends on the size of the second phases and the inverse of their volume fraction raised to a power between 0 3 and 1 once dmax is reached normal growth continues only if second phases are mobile or coarsen or if new driving forces are introduced that cause unpinning of boundaries normal grain growth in solnhofen limestone was significantly slower than in pure synthetic marble suggesting that migration is also inhibited by second phases in the limestone

integrated hydrogeochemical isotopic and geomorphological depiction of the groundwater salinization in the aquifer system of delhi india abstract the problem of salinization in the delhi aquifer that currently exhibits rapid landuse change is conspicuous and severe salinization may be caused either by a single process or a combination of different processes including anthropogenic related activities water logging and evaporative concentration of salts influx of natural saline water upconing of brines from the deeper parts of the aquifer and airborne salts depositions however there is a lack of well proven theory that can explain the salinity of the order of 5000 s cm in the deeper aquifers of delhi this work identifies inconclusiveness in the previous theories of marine ingression evaporation enrichment and subsequent leaching of salt further the study depicts a conceptual understanding of the origin of salinity in groundwater based on the integrated investigations of groundwater quality age and stable isotopic fingerprinting as well as gis based mapping of geomorphic features in order to explain the salinity observed in groundwater of nct delhi a phenomenological scenario is illustrated and supported by additional evidences the highest average ec value was for the shallow aquifer and is strongly symptomatic of anthropogenic influences on groundwater chemistry piper diagram showed heterogeneous water type and sufficient recharge mixing of the groundwater from different aquifers the relationship between cl br ratios vs cl indicated dissolution of salt deposits containing evaporative fraction present in the unsaturated zones or in the sediments of deeper aquifers and leaching of evaporative minerals from dunes of the adjacent thar desert cl so 4 2 ratio suggested the presence of connate seawater halite dissolution and concentration of dissolved salts by evapo transpiration of river water diverted for irrigation the results show that the closed inland marine conditions developed and buried with the active sedimentation in the geological past in this region and further intensive exploitation of groundwater and enhanced evaporation have together resulted in saline playa condition in some part of the region the scenario was further verified by matching the required condition for the formation of salt pan or playa with the existing geo morphological conditions of the area isotopic results indicate that salinity flushing is possible and proceeds in the areas of freshwater recharge

assessment of hydrogeochemistry and the quality of groundwater in 24 parganas districts west bengal hydrogeochemistry of an area helps in understanding the geological processes which control the chemistry of water and play an important role in determining the suitability of groundwater for various purposes in the present study an attempt has been made to understand the geological processes controlling the quality of water in a part of north and south 24 parganas districts of west bengal 39 representative groundwater samples were collected from the study area and physico chemical parameters were analyzed for all the samples schoeller and durov diagram were used to understand the hydrochemical nature of water results obtained from water chemistry were used in the interpretation of controlling processes using different conventional graphs and determining the quality of groundwater silicate weathering and ion exchange are the dominant processes controlling the chemistry of groundwater in the study area where calcium and magnesium in the water are replaced by the sodium and potassium in the minerals from the host rock as chloro alkaline indices are negative at most of the places saturation index was calculated to understand the mineralogy of the subsurface the groundwater is oversaturated with iron containing minerals like fe oh 3 goethite and hematite while undersaturated with anhydrite and gypsum the groundwater suitability was determined by calculating water quality index for drinking purpose while sar and residual sodium carbonate indices for the agricultural purpose the groundwater in the study area is not suitable for drinking but can be used for other household use and in irrigation for agriculture

fluid inclusions tectonic indicators abstract during the first half of the 20th century fluid inclusions have been studied in ore geology in order to determine the chemistry and physical parameters density of the mineralising fluids apart from a few pioneering works in the middle of the century fluid inclusions were not used as structural markers before the late 1980s during the same time experiments as well as observations of natural samples have shown that the volume shape and density of fluid inclusions may change when submitted to pressure temperature conditions different from their trapping isochores in view of these experiments and based on natural examples from the higher himalaya metamorphic rocks it is evident how fluid inclusions can be used as thermobarometric structural and tectonic markers points of interest for further studies on fluid inclusions in nature and experiments are also stressed

hydrogeological processes controlling the release of arsenic in parts of 24 parganas district west bengal a study was conducted to understand the hydrogeological processes dominating in the north 24 parganas and south 24 parganas based on representative 39 groundwater samples collected from selected area the abundance of major ions was in the order of ca2 na mg2 k fe2 for cations and hco3 po43 cl so42 no3 for anions piper trilinear diagram was plotted to understand the hydrochemical facies most of the samples are of ca hco3 type based on conventional graphical plots for ca mg vs so4 hco3 and na k vs cl it is interpreted that silicate weathering and ion exchange are the dominant processes within the study area previous studies have reported quartz feldspar illite and chlorite clay minerals as the major mineral components obtained by the xrd analysis of sediments mineralogical investigations by sem and edx of aquifer materials have shown the occurrence of arsenic as coating on mineral grains in the silty clay as well as in the sandy layers excessive withdrawal of groundwater for irrigation and drinking purposes is responsible for fluctuation of the water table in the west bengal aeration beneath the ground surface caused by fluctuation of the water table may lead to the formation of carbonic acid carbonic acid is responsible for the weathering of silicate minerals and due to the formation of clay as a product of weathering ion exchange also dominates in the area these hydrogeological processes may be responsible for the release of arsenic into the groundwater of the study area which is a part of north 24 parganas and south 24 parganas

the origin of fluids and nature of fluid rock interaction in mid crustal auriferous mylonites of the renco mine southern zimbabwe geothermometric constraints on auriferous shear zones of the renco mine in the northern marginal zone of the late archaean granulite facies limpopo belt in southern zimbabwe indicate that deformation and associated mineralization occurred at temperatures of at least 600 c up to more likely 700 c mid to upper amphibolite facies conditions during mineralization correspond to the regional scale retrogression of granulite facies wall rocks during the late archaean thrusting of high grade metamorphic rocks of the northern marginal zone onto low to medium grade granite greenstone terrains of the zimbabwe craton mineral assemblages indicate that the ore fluid was moderately oxidized with log fo2 values between 10 17 and 10 18 bars with high h2s activities of 0 25 0 75 elements enriched in the shear zones include au s fe cu mo bi te ni co and h2o au and cu being the most enriched geochemically au correlates with cu but not with s which together with the fact that gold is only rarely intergrown or in direct contact with sulfides possibly indicates a transport of gold as a chloride complex the siting of gold along fractures or within implosion breccias suggests that gold was precipitated due to fluid immiscibility induced by catastrophic fluid pressure drops during seismic slip events fluid inclusions are predominantly co2 ch4 n2 rich but petrographic work indicates that fluid inclusions have undergone extensive post entrapment modifications due to the pervasive recrystallization of mineral textures in the high temperature shear zones the mineralized shear zones are enriched in 18o compared to wall rock enderbites which is interpreted to represent an influx of externally derived fluids of probably metamorphic origin based on temporal and spatial relationships between mineralization late archaean overthrusting of the northern marginal zone onto the zimbabwe craton and coeval amphibolite facies hydration of granulites we suggest that the renco mineralization formed in a mid crustal environment from metamorphic fluids that were generated from dehydration of subcreted greenstone terrains of the zimbabwe craton

characterization and evaluation of processes governing the groundwater quality in parts of the sabarmati basin gujarat using hydrochemistry integrated with gis intense agricultural and industrial activities in any area are likely to make groundwater vulnerable with respect to its quality in one such area which is a part of sabarmati river basin of gujarat factors influencing the groundwater hydrochemistry in pre and post monsoon season were evaluated groundwater samples were collected from 5 km 5 km grids on the basis of spectral signature of vegetation and soil observed on satellite image integration of conventional graphical plots piper plot saturation index values estimated using phreeqc and gis was helpful not only to create the database for analysis of spatial variation in respective water quality parameters but also to decipher the hydrogeochemical process occurring in such a large area ussl diagram and sodium were used to characterise the suitability of groundwater for irrigation it was observed that leaching of wastes disposed from anthropogenic activities and agrichemicals is the major factor influencing the groundwater quality in addition to the natural processes such as weathering dissolution and ion exchange sea water relics are also impacting the groundwater quality control of indiscriminate and unplanned exploitation of groundwater application of fertilizers and disposal of industrial wastes in the affected areas can possibly ensure groundwater protection from further pollution and depletion copyright 2011 john wiley sons ltd

hydrochemistry deducing basaltic trap thickness for groundwater resource mapping along the deccan volcanic province dvp margin in india it is hypothesized that hydrochemical parameters can be employed to deduce the basaltic trap thickness and that there exist diverse hydrochemical processes within the existing host rocks along the deccan volcanic province dvp margin chemical imprints of aquifers in various flows of flood basalt and fissured zones of granites had been appraised using major ion chemistry of groundwater in a test site of 623 km2 at the southern margin of the dvp in india the wide ranging hydrochemical processes obtained from empirical data describe the predominance of carbonate dolomite calcite and anorthite weathering in basalts and alkali feldspar albite and orthoclase in granites results showed that the elevated concentrations of alkaline earth elements in basaltic aquifers and alkali rich elements in granitic aquifers were useful in tracing the sources of host rock for dissolved mineral reactants further a digital elevation model using shuttle radar topography mission 90 m elevation satellite data aided in deciphering trap thickness vertical transition zone of trap and granitic basement comprising the well depths and hydrochemistry the mapping of trap thickness is useful to explore the groundwater resources at the vertical transition zone between the basaltic trap and granitic base the estimated thickness of the basaltic trap is varied from 4 to 98 m at the dvp southern margin which is further verified with the help of exploratory well lithologs matched closely

effect of confining pressure on dilatation recrystallization and flow of rock salt at 150 c microstructural evidence for fluid assisted dynamic recrystallization fadrx is widespread in naturally deformed rock salt however the principal experimental evidence for fadrx in salt has been obtained from stress relaxation experiments and it is unclear whether the process occurs during steady state dislocation creep and what its effect might be here we report deformation experiments performed on natural rock salt at a constant strain rate of 3 5 10 7 s 1 150 c and confining pressures pc of 3 30 mpa samples deformed at pc 3 mpa showed continuous work hardening and minor dilatation microstructurally they exhibited intergranular cracking plus slip band and subgrain structures indicative of dislocation glide creep electron backscatter diffraction analysis revealed a high frequency of boundaries with low angle misorientations in the range 5 10 in contrast samples deformed at pc 6 5 mpa showed work hardening followed by steady state flow at strains 6 7 these samples compacted slightly and crystal plastic deformation was accompanied by extensive fadrx with a predominance of high angle boundaries 30 50 over low angle boundaries we infer that fadrx is suppressed by dilatation at low pressures as a result of grain boundary disruption at pressures high enough to prevent dilatation however fadrx acts as a recovery mechanism counteracting work hardening the results offer a possible explanation for rheological variability seen in previous experiments conducted at pressures up to 30 mpa a simple rate model for diffusion and interface controlled fadrx indicates that fadrx should become increasingly important toward natural halokinetic conditions although the effect on flow stresses is likely to be small

fluid inclusion microthermometry in be ta li sn bearing pegmatites from the borborema province northeast brazil abstract fluid inclusions in be ta li sn bearing pegmatites have been reported in the literature as hypersaline aqueous brines or low salinity aqueous or aqueous carbonic fluids the evolution paths of volatile fluids in equilibrium with the different crystallizing phases of rare element pegmatites do not seem to be unique the aim of this work is to contribute to this discussion on the basis of fluid inclusion information from the borborema pegmatite province bpp in northeast brazil some well known heterogeneous be ta li sn mineralized pegmatites of this province were systematically sampled along cross sections with the purpose of studying the fluid inclusions in the different pegmatite zones i muscovite rich contact zone ii homogeneous or graphic pegmatite iii blocky feldspar zone and iv quartz core the observed fluid inclusions mainly in quartz were almost always secondary or pseudosecondary grouped along healed fractures with random orientation even some trails paralleling quartz grain limits were not undoubtedly primary almost all these fluid inclusions were filled with low salinity aqueous or aqueous carbonic fluids primary inclusions were recognized only in some well formed crystals from druses with erratic distribution in the pegmatites microthermometric data from these samples confirm that the various crystallizing phases of the pegmatites were in equilibrium with low salinity aqueous or aqueous carbonic fluids with insignificant n 2 or ch 4 contents with frequent accidentally trapped solids the various types of primary inclusions found in these crystals compare well with the types of secondary inclusions of the samples from the systematic cross sections the relative age of the crystals hosting primary fluid inclusions the relative age of primary inclusion types in successive crystal growth zones the relative age of secondary fluid inclusion trails and the corresponding microthermometric data allowed to establish the most probable evolution of the fluid characteristics during pegmatite crystallization an early low salinity aqueous carbonic fluid with co 2 contents of 20 mol was present during the crystallization of early minerals such as garnet and tourmaline of the border zone and graphic quartz beryl manganotantalite and blue tourmaline of zones ii and iii the end of zone iii crystallization occurred in the presence of a low salinity aqueous fluid with very low co 2 contents as indicated by inclusions in the smoky core of quartz crystals at the limit between zones iii and iv later aqueous fluids barren in co 2 and with salinities increasing from 5 to 20 coexisted with the formation of the pegmatite nucleus and replacement bodies as indicated by inclusions in the border of these crystals and in euclase the estimated trapping conditions of 3 5 kbar and 580 c for the earliest inclusion types agree with the regional metamorphic conditions and with the known liquidus conditions of rare element bearing pegmatite crystallization the trapping conditions of inclusions in euclase and coexisting quartz crystal rims in the pegmatitic core at 3 5 kbar and 400 c are slightly below the conditions admitted for the solidus of rare element pegmatites and indicate an isobaric cooling during pegmatite crystallization

fluid inclusions in rocks from the amphibolite facies gneiss to charnockite progression in southern karnataka india direct evidence concerning the fluids of granulite metamorphism fluid inclusion studies of rocks from the late archaean amphibolite facies to granulite facies transition zone of southern india provide support for the hypothesis that co2 rich h2o poor fluids were a major factor in the origin of the high grade terrain charnockites closely associated leucogranites and quartzo feldspathic veins contain vast numbers of large co2 rich inclusions in planar arrays in quartz and feldspar whereas amphibole bearing gray gneisses of essentially the same compositions as adjacent charnockites in mixed facies quarries contain no large fluid inclusions inclusions in the northernmost incipient charnockites as at kabbal karnataka occasionally contain about 25 mol of immiscible h2o lining cavity walls whereas inclusions from the charnockite massif terrane farther south do not have visibile h2o microthermometry of co2 inclusions shows that miscible ch4 and n2 must be small probably less than 10mol combined densities of co2 increase steadily from north to south across the transitional terrane entrapment pressures calculated from the co2 equation of state range from 5 kbar in the north to 7 5 kbar in the south at the mineralogically inferred average metamorphic temperature of 750 c in quantitative agreement with mineralogic geobarometry this agreement leads to the inference that the fluid inclusions were trapped at or near peak metamorphic conditions calculations on the stability of the charnockite assemblage biotite orthopyroxene k feldspar quartz show that an associated fluid phase must have less than 0 35 h2o activity at the inferred p and t conditions which agrees with the petrographic observations high tio2 content of biotite stabilizes it to lower h2o activities and the steady increase of biotite tio2 southward in the area suggests progressive decrease of ah2o with increasing grade oxygen fugacities calculated from orthopyroxene magnetite quartz are considerably higher than the graphite co2 o2 buffer which explains the absence of graphite in the charnockites the present study quantifies the nature of the vapours in the southern india granulite metamorphism it remains to be determined whether co2 flushing of the crust can by itself create large terranes of largeion lithophile depleted granulites or whether removal of h2o bearing anatectic melts is essential

geochemistry and assessment of hydrogeochemical processes in groundwater in the southern part of bathinda district of punjab northwest india hydrogeochemistry of groundwater is important for sustainable development and effective management of the groundwater resource fifty six groundwater samples were collected from shallow tube wells of the intensively cultivated southern part of district bathinda of punjab india during pre and post monsoon seasons conventional graphical plots were used to define the geochemical evaluation of aquifer system based on the ionic constituents water types hydrochemical facies and factors controlling groundwater quality negative values of chloroalkaline indices suggest the prevalence of reverse ion exchange process irrespective of the seasons a significant effect of monsoon is observed in terms chemical facies as a considerable amount of area with temporary hardness of ca2 mg2 hco3 type in the pre monsoon switched to ca2 mg2 cl type 18 followed by na hco3 type 14 in the post monsoon evaporation is the major geochemical process controlling the chemistry of groundwater process in pre monsoon however in post monsoon ion exchange reaction dominates over evaporation carbonate weathering is the major hydrogeochemical process operating in this part of the district irrespective of the season the abundance of ca2 mg2 in groundwater of bathinda can be attributed mainly to gypsum and carbonate weathering silicate weathering also occurs in a few samples in the post monsoon in addition to the carbonate dissolution water chemistry is deteriorated by land use activities especially irrigation return flow and synthetic fertilisers urea gypsum etc as indicted by concentrations of nitrate sulphate and chlorides overall results indicate that different natural hydrogeochemical processes such as simple dissolution mixing weathering of carbonate minerals locally known as kankar and silicate weathering are the key factors in both seasons

laurentide glaciation in west central alberta a single late wisconsinan event the grande prairie region in west central alberta shows evidence of late wisconsinan laurentide glaciation in the form of a widespread till containing abundant erratic clasts derived from the canadian shield two sections located on the smoky river at watino and on the simonette river 80 km to the southwest expose sediment lying stratigraphically below the till a similar sequence is exposed in both localities 5 10 m of coarse quartzite gravel overlain by a thick sequence of sand and silt the gravel contains no laurentide erratics and is thus preglacial the contact between the basal gravel and the overlying sand and silt is sharp and conformable 14c dates from the base of the simonette section and throughout the watino section suggest a middle wisconsinan age thus the sediment exposed is interpreted as a conformable middle wisconsinan sequence the sedimentary sequences were deposited in a moderate to low energy braided stream system flowing towards the north the general fining up trend in the

microstructure and micromotion in recrystallization flow of octachloropropane a first look advance of the genetic theory of metamorphic fabric depends in part on improved understanding of dynamic recrystallization processes and the effects of these processes upon various fabric elements this paper describes aspects of the microstructural evolution and associated small scale motion in a dynamically recrystallizing sheet of octachloropropane the material was deformed in progressive pure shear at 2 10 3 sec 1 with interruptions for photography and u stage measurement at 70 of its absolute melting temperature the dominant recrystallization process is migration of grain boundaries with consequent major adjustment of the shapes and sizes of grains but no marked change in the average grain size and no creation of new grains typical grains in the fully deformed material 30 bulk shortening have a composite structure with primitive high strain regions inherited directly from the undeformed state rimmed by successively younger regions of lower strain accreted behind outwardmoving boundaries an array of second phase marker particles permits distinction between grain boundary motion with and through the material and reveals an unexpected ability of grains as a whole to migrate short distances up a bulk strain gradient the markers also show that the only important deformation process is intragranular deformation and that it is proceeding at somewhat different rates in different grains the central problem posed by the observations is to explain the direction and speed of each migrating boundary two hypotheses were tested neither with outstanding success one of these hypotheses is that grain boundary migration is part of a strain accomodation process that operates between grains stretching or shortening at different rates parallel to their mutual boundary

a hydrogeochemical approach to evaluate the occurrence and source of salinization in the shallow aquifers of the southeastern imphal valley in the indo myanmar range of northeast india the imphal valley is an intramontane basin confined within an anticlinorium of several anticlines and synclines in the disang group of rocks of tertiary age this valley of more than 2 million people is occupied by fluvio lacustrine deposits of quaternary age and is located in the central part of the indo myanmar range of northeast india the hydrogeochemical parameters of temperature ph orp tds na cl br ba b sr li 18o hco3 k mg ca no3 po4 so4 in 173 samples using ion chromatograph icp aes icp oes icp ms and 37 dugwells were studied to understand the occurrence and origin of salinization process for the first time the order of abundance of ions is identified as hco3 na cl ca mg k no3 po4 sr br b ba li so4 five hydrochemical facies na cl ca mg hco3 na hco3 ca mg hco3 cl and ca mg cl represent the types of waters the saline dominated water types na cl and na hco3 represent piedmont and the rest of the facies represent alluvial plain and flood plain groundwaters durov s diagram reveales initial and intermediate stages of groundwater evolution isotope 18o gibbs diagram and ions scatter plots suggest evaporation and crystallization processes leading to halite encrustation in the disang shales negative eh low no3 and the absence of so4 indicates reduced condition coupled with rich dissolve organic matters leading to elevation of salts in soils around piedmont where the rock type is exclusively of the disang shales trilinear plot correlation matrix and water table flow analysis suggest salinization of groundwater originates in piedmont groundwater and disseminates towards alluvial plain and flood plain along the flow path

dynamic recrystallization of wet synthetic polycrystalline halite dependence of grain size distribution on flow stress temperature and strain abstract it is often observed that dynamic recrystallization results in a recrystallized grain size distribution with a mean grain size that is inversely related to the flow stress however it is still open to discussion if theoretical models that underpin recrystallized grain size stress relations offer a satisfactorily microphysical basis the temperature dependence of recrystallized grain size predicted by most of these models is rarely observed possibly because it is usually not systematically investigated in this study samples of wet halite containing 10 ppm water by weight were deformed in axial compression at 50 mpa confining pressure the evolution of the recrystallized grain size distribution with strain was investigated using experiments achieving natural strains of 0 07 0 12 and 0 25 at a strain rate of 5 10 7 s 1 and a temperature of 125 c the stress and temperature dependence of recrystallized grain size was systematically investigated using experiments achieving fixed strains of 0 29 0 46 and one to a strain of 0 68 at constant strain rates of 5 10 7 1 10 4 s 1 and temperatures of 75 240 c yielding stresses of 7 22 mpa the microstructures and full grain size distributions of all samples were analyzed the results showed that deformation occurred by a combination of dislocation creep and solution precipitation creep dynamic recrystallization occurred in all samples and was dominated by fluid assisted grain boundary migration during deformation grain boundary migration results in a competition between grain growth due to the removal of grains with high internal strain energy and grain size reduction due to grain dissection i e moving boundaries that crosscut or consume parts of neighbouring grains at steady state grain growth and grain size reduction processes balance yielding constant flow stress and recrystallized grain size that is inversely related to stress and temperature evaluation of the recrystallized grain size data against the different models for the development of mean steady state recrystallized grain size revealed that the data are best described by a model based on the hypothesis that recrystallized grain size organizes itself in the boundary between the grain size sensitive solution precipitation and grain size insensitive dislocation creep fields application of a piezometer calibrated using the recrystallized grain size data to natural halite rock revealed that paleostresses can vary significantly with temperature up to a factor of 2 5 for t 50 200 c and that the existing temperature independent recrystallized grain size stress piezometer may significantly underestimate flow stresses in natural halite rock

geochemical characterization and heavy metal contamination of groundwater in satluj river basin groundwater a renewable and finite natural resource vital for man s life social and economic development and a valuable component of the ecosystem is vulnerable to natural and human impacts the aim of present study is to evaluate hydrogeochemical parameters and heavy metals in groundwater and to study their spatial distribution in the rupnagar district of punjab the spatial distribution of physico chemical parameters were studied using arc gis 9 2 it was observed that the concentration of parameters such as no3 cd cr mn and pb was above permissible limit world health organization who in southern part of the study area the heavy metal pollution index hpi was calculated for all sampling locations and it was found much above the critical limit of pollution geochemical reaction models of selected water groups were constructed using phreeqc geochemical modeling suggests that sodium has source other than halite albite and calcium has alternate source other than gypsum carbonate or silicates it also suggests that evaporites ion exchange dissolution along with anthropogenic activities are controlling the hydro geochemistry of groundwater in the region various indices such as heavy metal pollution index permeability index sodium adsorption ratio were studied to verify suitability of groundwater for drinking and irrigation

hydrogeochemistry of groundwater and anthropogenic control over dolomitization reactions in alluvial sediments of the deoria district ganga plain india groundwater is a critical resource in deoria district as it is the main source of drinking water and irrigation the aquifer has deteriorated to a high degree during the last two to three decades in quality and quantity due to high population growth and environmental pollution more than 90 of the population get their drinking water from subsurface waters fifteen wells were sampled in june 2006 to probe the hydrogeochemical components that influence the water quality the results show that groundwater have ec tds na mg2 hco 3 and th higher than the who 1997 maximum desirable limits a hydrogeochemical numerical model for carbonate minerals was constructed using the phreeqc package the regression analysis shows that there are three groups of elements which are significantly and positively correlated the main hydrochemical facies of the aquifer ca mg hco3 represents 33 33 of the total wells the geochemical modeling demonstrated that the reactions responsible for the hydrochemical evolution in the area fall into three categories 1 dissolution of salts 2 precipitation of dolomite 3 ion exchange solubility of dolomite calcite aragonite and gypsum were assessed in terms of the saturation index the thermodynamic prerequisites for dolomite supersaturation reactions are satisfied by subsurface waters since they are supersaturated with respect to dolomite undersaturated or in equilibrium with respect to calcite and undersaturated with respect to gypsum the ca2 versus so 4 2 and mg2 versus so 4 2 trends are also compatible with homologous trends resulting from dolomite supersaturation

the sedimentary record of carboniferous rivers continuing influence of land plant evolution on alluvial processes and palaeozoic ecosystems abstract evidence from modern rivers and the deep time geological record attests to the fundamental importance of plant life for the construction of physical habitats within fluvial environments data from an extensive literature review and original fieldwork demonstrates that many landforms and geomorphic features of modern river systems appear in the palaeozoic stratigraphic record once terrestrial vegetation had adopted certain evolutionary advances for example stable point bars are associated with the onset of rooted plants in the siluro devonian and avulsive and anabranching fluvial systems become common at the same time as extensive arborescent vegetation in the carboniferous in this paper we demonstrate a correlation between the diversification of physical fluvial environments and the expansion of terrestrial fauna and flora with an emphasis on the culmination of these trends within carboniferous alluvial systems many extrinsic factors have been considered as possible controls on the evolutionary timelines of terrestrialization for organisms however a fundamental prerequisite for achieving terrestrial biodiversity was the variety of physical habitats especially riparian systems available for newly evolved organisms in association with abundant lowland meandering systems the widespread appearance across carboniferous alluvial plains of fixed channel and anabranching reaches created further physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes furthermore the associated increase in arborescent vegetation and supply of large woody debris to inland and coastal rivers would have created a wealth of microhabitats for continental organisms we argue that the expanding extent and diversity of physical alluvial niches during the palaeozoic is an underappreciated driver of the terrestrialization of early continental life the study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats

the application of fluid inclusions to migration of oil and diagenesis in petroleum reservoirs abstract fluid inclusions can be used to interpret thermal history and petroleum maturation and migration relative to burial history temperature pressure and composition data collected from fluid inclusions are used to determine the environment of diagenesis and the timing of cementation and migration cements in petroleum reservoirs contain both oil and aqueous fluid inclusions fluorescence spectroscopy is used to identify oil inclusions and to determine the maturity of entrapped oil the lifetime of fluorescence induced by a pulsed laser is related to the api gravity of entrapped oil interpretation of fluid inclusion data depends on knowing the origin of fluid inclusions and the probability that they survive in the burial environment those aspects of fluid inclusion study are investigated by synthesizing oil and aqueous inclusions in calcite crystals in laboratory experiments examples of how fluid inclusions are used to determine the physico chemical environments of diagenesis in petroleum reservoirs and the timing of cementation and migration are given for the wealden basin england the mishrif formation dubai the smackover formation gulf coast u s a and jurassic sandstones offshore norway in the wealden basin temperature data from fluid inclusions are used to determine that oil migration occurred in the cretaceous and that the reservoir rocks have been uplifted to varying degrees at a time after migration distribution of oil inclusions indicates that generation and migration of oil was principally in the western part of the basin the geochemistry of oil inclusions in calcite cements from the mishrif formation dubai are used to determine the type and maturity of entrapped oil temperature data from oil and water inclusions are used to relate reservoir diagenesis to burial history and the migration of oil in deep smackover reservoirs oil contains h 2 s the origin of the h 2 s is examined by study of fluid inclusions containing h 2 s in jurassic sandstones offshore norway fluid inclusion studies show that silica cementation is related to burial depth whereas a later calcite cementation originated from invasion of a hot fluid

halite cementation and carbonate diagenesis of intra salt reservoirs from the late neoproterozoic to early cambrian ara group south oman salt basin late neoproterozoic to early cambrian carbonates of the ara group form important intra salt stringer reservoirs in the south oman salt basin differential loading of thick continental clastics above the six carbonate to evaporite cycles of the ara group led to the formation of salt diapirs encasing a predominantly self charging hydrocarbon system within partly highly overpressured carbonate bodies stringers these carbonates underwent a complex diagenetic evolution with one stage of halite cementation in a shallow early and another in a deep late burial environment early and late halite cements are defined by their microstructural relationship with solid bitumen the early phase of halite cementation is post dated by solid reservoir bitumen this phase is most pervasive towards the top of carbonate stringers where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics bromine geochemistry revealed significantly higher bromine contents up to 280 p p m in the early halite compared with the late halite 173 p p m the distribution patterns and the high bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval later in burial history relatively small quantities of early halite were dissolved locally and re precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements late halite cement also seals fractures which show evidence for repeated reopening initially these fractures formed during a period of hydrothermal activity and were later reopened by a crack seal mechanism caused by high fluid overpressures porosity plugging by early halite cements affects the poroperm characteristics of the ara carbonates much more than the volumetrically less important late halite cement the formation mechanisms and distribution patterns of halite cementation processes in the south oman salt basin can be generalized to other petroliferous evaporite basins

evaluation of hydrogeochemical characteristics of phreatic alluvial aquifers in southeastern coastal belt of prakasam district south india the assessment of hydrogeochemical processes that govern the water quality of inland freshwater aquifers in coastal environment especially in indian sub continent is occasionally attempted to bridge the gap a detail hydrochemical evaluation of groundwater occurring in coastal alluvium is attempted single set of high density water sampling is done from a limited area to gain an in depth knowledge of the processes that govern the water chemistry of the sandy aquifers the water is of weak alkaline nature and less mineralized ec being na ca2 hco3 so42 mg2 no3 na and cl are almost in similar proportions implying the influence of coastal climate on water quality the water shows modest variation in their ionic assemblage among different sample points as evident from schoeller scheme groundwater can be classified into three distinct facies viz cl ca2 mg2 na cl and ca2 mg2 hco3 types the ionic assemblages their indices ratios and cross plots substantiate that multiple processes were involved in the evolution of the water chemistry among them silicate weathering halite dissolution ion exchange and base exchange played prominent role in the ion enrichment of groundwater the aquatic chemistry is further influenced and modified by marine environment evapotranspiration and anthropogenic inputs which is authenticated by good correlation r2 1 among the na cl ec mg2 na and cl gibbs plots established that evaporation is more responsible for contribution of minerals to the groundwater than aquifer material nitrate contamination can be attributed for poor sewerage disposal mechanism which is aggravated by fertilizer inputs irrigation practices and agriculture activity a contrasting correlation r2 90 to 0 40 among select pairs of ions reassures dissimilar source of those ions involvement of multiple processes and limited interaction of formation water with aquifer material

alluvial channel bank collapse phenomena in the old red sandstone hitra group western central norway the old red sandstone ors on the island of hitra forms an approximately 1350 m thick succession of alternating continental mudstones sandstones and conglomerates of possibly latest silurian to devonian age within the middle part of this succession just above a major scoured surface a spectacular slump feature was observed the phenomenon is interpreted as a unit of overbank channel bank mudstones which because of undercutting and liquidization caved into a low sinuosity river channel the hitra sequence is the only one in the norwegian ors where such phenomena have as yet been identified

an in situ optical investigation of the deformation behaviour of sodium nitrate an analogue for calcite abstract in situ observations have been made under the optical microscope of the deformation of thin polycrystalline specimens of sodium nitrate calcite structure at temperatures between 20 c 0 5 tm and 300 c 0 98 tm at low temperatures or high strain rates deformation twinning is observed between 20 c and 180 c inhomogeneous deformation together with dynamic recrystallisation by subgrain rotation results in a core and mantle microstructure at temperatures above 180 c rapid dynamic recrystallisation by grain boundary migration also occurs producing a coarse grained microstructure the results are interpreted in terms of impurity controlled grain boundary motion as proposed for halite and a strong similarity between the deformation behaviour of sodium nitrate and marble is noted

deformation related recrystallization processes abstract recrystallization is a common microstructural transformation that occurs during deformation metamorphism and diagenesis of rocks studies on minerals and rock analogues have demonstrated that a wide range of recrystallization mechanisms can occur the range of mechanisms is related to the various ways in which two basic processes grain boundary migration and new grain boundary formation combine to transform the microstructure two recent papers drury et al 1985 urai et al 1986 have proposed different schemes for the description of recrystallization mechanisms the purpose of this paper is to provide a unified framework for the description of mechanisms recrystallization mechanisms are divided into three main types rotation mechanisms which principally involve the formation of new grain boundaries migration mechanisms which principally involve grain boundary migration and general mechanisms which involve both basic processes a further distinction is made on the basis of the continuity of the microstructural transformation with respect to time each of the three main types of mechanism can be divided into a number of sub types depending on whether the processes of grain boundary migration new grain boundary formation and new grain formation occur in a discontinuous or continuous manner with respect to time as the terms continuous and discontinuous have been used in the metallurgical literature to signify the spatial continuity of the microstructural transformation the terms discontinuai and continual are used to refer to the temporal continuity of the transformation it is recommended that the following aspects should be specified if possible in a general description of recrystallization mechanisms 1 1 how do the basic processes combine to transform the microstructure 2 2 if new grain development occurs what is the development mechanism and does new grain formation occur in a continual or discontinuai manner 3 3 if grain boundary migration is involved in the transformation what is the migration mechanism i e fast solute escape migration slow solute loaded migration fluid assisted migration etc and is migration a continual or discontinuai process the application of the unified scheme is illustrated by reviewing studies that have provided detailed information on the recrystallization mechanisms involved the complicating effects of solid solution impurities dispersed second phase particles and grain boundary fluid films are also considered and it is demonstrated that variations in content of these types of impurity can significantly effect the types of recrystallization that occur in a given material

hydrogeochemical processes in the groundwater environment of muktsar punjab conventional graphical and multivariate statistical approach understanding the hydrogeochemical processes that govern groundwater quality is important for sustainable management of the water resource a study with the objective of identifying the hydro geochemical processes and their relation with existing quality of groundwater was carried out in an intensively cultivated district of punjab india the study approach includes conventional graphical plots and multivariate analysis of the hydrochemical data to define the geochemical evaluation of aquifer system based on the ionic constituents water types hydrochemical facies and factors controlling groundwater quality the results suggest that different natural hydrogeochemical processes like simple dissolution mixing weathering of carbonate minerals locally known as kankar silicate weathering and ion exchange are the key factors in the pre monsoon which was superseded by leaching processes loaded with anthropogenic inputs in the post monsoon limited reverse ion exchange has been noticed at few locations of the study area especially in pre monsoon periods there was a significant effect of monsoon observed in terms of hardness and the significant amount of area with temporary hardness ca2 mg2 hco 3 type in the pre monsoon switched to permanent hardness domain i e ca2 mg2 cl type by the post monsoon at most factor analyses substantiate the findings of conventional graphical plots and provide greater confidence in data interpretation thus the study highlights the descriptive capabilities of conventional and multivariate techniques as effective tools in groundwater evaluation