hot water drilling and bore hole closure in cold ice drilling bore holes in deep cold ice masses by hot water methods and maintaining these holes with sufficient diameter to allow down hole experimentation poses a major obstacle to the investigation of conditions beneath ice sheets and ice streams closure of the water filled holes by refreezing is the dominant difficulty in this paper we describe calculations of heat transfer from the drilling system to the ice and the subsequent time dependent motion of the phase boundary defining the bore hole wall results are presented with the view of optimizing the bore hole radius at depth for a fixed drill performance and a variable rate of drilling calculation of melting refreezing rates at the bore hole wall requires the use of a one dimensional time dependent numerical heat flow model with a distorting mesh which follows the changing hole size the delay of hole closure is discussed with a view to keeping holes open long enough to allow instruments to be lowered to the glacier bed while realizing that drilling system performance may be marginal because of logisitical and or expenditure constraints the relative merits of drilling a large hole which is very time consuming with a small drill and the use of water soluble antifreezes which have a history of creating plugs of ice slush are discussed a method of creating a stable hole filled with antifreeze in which ice slush does not occur is described the recent application of these theoretical ideas to the planning and implementation of successful hot water drilling programs in antarctica and greenland is also presented

extensive liquid meltwater storage in firn within the greenland ice sheet surface melt water from the greenland ice sheet can become trapped in firn delaying its journey to the sea radar and ice core observations provide direct evidence of a perennial aquifer in the firn layer in southern greenland that represents a potentially significant contribution to the greenland mass budget

physical conditions at the base of a fast moving antarctic ice stream boreholes drilled to the bottom of ice stream b in the west antarctic ice sheet reveal that the base of the ice stream is at the melting point and the basal water pressure is within about 1 6 bars of the ice overburden pressure these conditions allow the rapid ice streaming motion to occur by basal sliding or by shear deformation of unconsolidated sediments that underlie the ice in a layer at least 2 meters thick the mechanics of ice streaming plays a role in the response of the ice sheet to climatic change

glauberite halite association of the zaragoza gypsum formation lower miocene ebro basin ne spain glauberite is the most common mineral in the ancient sodium sulphate deposits in the mediterranean region although its origin primary or diagenetic continues to be a matter of debate a number of glauberite deposits of oligocene miocene age in spain display facies characteristics of sedimentologic significance in particular those in which a glauberite halite association is predominant in this context a log study of four boreholes in the zaragoza gypsum formation lower miocene ebro basin ne spain was carried out two glauberite halite lithofacies associations a and b are distinguished association a is composed of bedded cloudy halite and minor amounts of massive and clastic glauberite association b is made up of laminated to thin bedded clear macrocrystalline massive clastic and contorted lithofacies of glauberite and small amounts of bedded cloudy halite transparent glauberite cemented by clear halite as well as normal graded and reverse graded glauberite textures are common this type of transparent glauberite is interpreted as a primary subaqueous precipitate gypsum thenardite or mirabilite are absent in the two associations the depositional environment is interpreted as a shallow perennial saline lake system in which chloride brines association a and sulphate chloride brines association b are developed the geochemical study of halite crystals bromine contents and fluid inclusion compositions demonstrates that conditions for co precipitation of halite and glauberite or for precipitation of na sulphates mirabilite thenardite were never fulfilled in the saline lake system

initial in situ measurements of perennial meltwater storage in the greenland firn aquifer 1 a perennial storage of water in a firn aquifer was discovered in southeast greenland in 2011 we present the first in situ measurements of the aquifer including densities and temperatures water was present at depths between 12 and 37 m and amounted to 18 7 0 9 kg in the extracted core the water filled the firn to capacity at 35 m measurements show the aquifer temperature remained at the melting point representing a large heat reservoir within the firn using model results of liquid water extent and aquifer surface depth from radar measurements we extend our in situ measurements to the greenland ice sheet the estimated water volume is 140 20 gt representing 0 4 mm of sea level rise slr it is unknown if the aquifer temporary buffers slr or contributes to slr through drainage and or ice dynamics

displacive halite hoppers from the dead sea some implications for ancient evaporite deposits abstract large hopper shaped halite cubes up to 10 cm on a side grow displacively within holocene sediments near the southern end of the dead sea under conditions of high temperatures ionic concentrations and rapid rates of crystallization two theories of formation are presented downward diffusion of ions versus upward diffusion and evaporative pumping both alternatives are considered possible and the correct choice probably depends upon the location of the sediments at the time of precipitation whether subaqueous or subaerial a choice indeterminate at present because of human disturbance to the sediments prior to collection displacively formed halite crystals similar in morphology to the dead sea cubes are common in evaporite bearing carbonate rocks of many regions such as the salina fm u silurian michigan basin the kirkham mudstone u triassic cumbria england and the u miocene gessoso solfifera fm of sicily these are believed to have formed under conditions analogous to those in the present dead sea these observations taken together with those of other authors may now be used for the facies interpretation of ancient halite deposits

thermal tracking of meltwater retention in greenland s accumulation area 1 poorly understood processes controlling retention of meltwater in snow and firn have important implications for greenland ice sheet s mass balance and flow dynamics here we present results from a 3 year 2007 2009 field campaign studying firn thermal profiles and density structure along an 85 km transect of the percolation zone of west greenland we installed one or two thermistor strings at 14 study sites each string having 32 sensors spaced between 0 and 10 m depth data from our network of over 500 sensors were collected at 15 60 min intervals for 1 2 years thereby recording the thermal signature of meltwater infiltration and refreezing during annual melt cycles we document three types of heating of firn related to different mechanisms of meltwater motion and freezing including heterogeneous breakthrough events wetting front advance and year round heating from freezing of residual deep pore water vertically infiltrating meltwater commonly penetrates through cold firn accumulated over decades even where ice layers are present at the previous summer surface and where ice layer thickness exceeds several decimeters the offset between the mean annual air temperature and the 10 m firn temperature reveals the elevation dependency of meltwater retention along our transect the firn is 10 c warmer than the mean annual air temperature at the region where meltwater runoff initiates during 2007 2009 runoff was limited to elevations lower than 1500 m with no sharp runoff limit rather the ratio of retention to runoff transitioned from all retention to all runoff across a 20 km wide zone

multiple applications of dipmeter curves for analyzing evaporite formations examples from paleogene of bresse trough france the microresistivity curves recorded by dipmeters give much diverse information about evaporitic formations because these curves have a fine vertical resolution approximately 1 cm and show the very high contrast in resistivity between evaporites with high resistivity and clay and carbonate rocks which are porous and conductive examples are taken from the paleogene salt sequence and its overlying formations of the bresse trough in southeastern france the consistency of the 4 to 8 dipmeter curves allows clear recognition of different salt facies primary salt secondary salt and mixed patches of clay and carbonate within displacive halite layers and sulfate facies massive anhydrite nodular anhydrite etc the correlation of thin continuous carbonate and clastic beds using resistivity curves discloses with a high degree of precision the geometry of the various formations between wells examples show the detection of small magnitude halite dissolution a few meters vertically and the lateral effect of anhydrite hydration in this paper a method is proposed for determining structural dip of salt beds by computing dip angle and azimuth of thin conductive beds within the salt using the dualdip computer program a frequency distribution plot of these dip angles and azimuths gives a good indication of the dip of the salt beds

the alpine haselgebirge formation northern calcareous alps austria permo scythian evaporites in an alpine thrust system abstract multiphase deformed and weakly metamorphosed permo scythian evaporites of the northern calcareous alps eastern alps of austria were deposited in an aborted rift arm of the northwest tethys they represent marine precipitates laid down in a basin surrounded by alluvial fans and mudflats mean bromide values of halite 13 53 ppm as well as s isotope ratios of sulphate minerals 14 0 9 cdt indicate that the contribution of non marine waters to the marine brine composition was insignificant the most striking feature is the haselgebirge structure a chaotic melange of shales silt and sandstones anhydrites carbonates and scarce magmatites kirchner 1980 embedded in a clayey halite matrix this melange resulted from severe tectonization caused by a variety of deformational processes halokinesis diapirism gravitational sliding and alpine thrust tectonics

paleoproterozoic stark formation athapuscow basin northwest canada record of cratonic scale salinity crisis abstract the paleoproterozoic stark formation a thick breccia unit formed during the transition from marine to non marine foreland basin fill in the athapuscow basin northwest territories canada four types of breccia occur in the stark formation 1 bedded breccias at the base of the unit overlying the basinal facies of the underlying pethei group are interpreted as debris flows 2 massive chaotic breccias occur in the lower part of the stark formation throughout the basin and these are interpreted to be evaporite collapse breccias 3 siltstone and mudstone breccia occurs in the upper part of the stark formation and is also interpreted as evaporite collapse breccia though much less evaporite was involved in its formation than the underlying chaotic breccia and 4 laminar accretionary breccia consisting of laminar carbonate clasts commonly with flat bottoms and convex up upper surface geometries these clasts occur in lenticular pods and are interpreted to form in caves following dissolution of evaporites or carbonates the widespread presence and abundance of evaporite pseudomorphs especially halite in all breccia types the stratigraphic restriction of the stark formation and irregular filling above this unit indicates that all but the bedded breccia formed by the dissolution and collapse of evaporites chaotic breccia directly above underlying pethei group shallow water and deep water carbonates indicates the evaporates formed across the platform and adjacent deep basin foundered megaclasts up to 1 5 km long and 40 m thick in basinal settings suggest cumulative evaporite thicknesses on the order of a few tens to a few hundreds of meters carbonate clasts in all the breccias contain abundant wave ripples planar laminations stromatolites and ooids these structures along with a paucity of subaerial exposure features indicates nearly all carbonate deposition in the stark was subaqueous thus by inference the evaporites in the stark formation were also partially subaqueous displacive halite pseudomorphs are common throughout all facies in the stark formation silicified and dolomite filled halite pseudomorphs are common along the contact between the evaporite collapse breccia and underlying carbonate platform pethei group and surrounding large clasts in basinal settings silicified hopper crystal casts within deep water rhythmites of the uppermost pethei group indicate precipitation of halite over deep waters gypsum pseudomorphs are exceedingly rare and anhydrite pseudomorphs were not observed the dominance of halite features in this basin and two penecontemporaneous basins kilihigok basin and wopmay orogen surrounding the slave craton suggests that relative to the present day seawater at 1 9 to 1 8 ga was oversaturated with respect to calcium carbonate had higher hco3 concentration and possibly was depleted in so42 the dearth of extensive thick bedded marine gypsum in the archean and early paleoproterozoic can be explained by low atmospheric oxygen content prior to 2 ga in conjunction with increased carbonate saturation before 1 6 ga

stratigraphic and structural controls on gold mineralization in the pilgrim s rest goldfield eastern transvaal south africa abstract since 1872 approximately 185 metric tons of gold and a significant amount of silver have been won from numerous stratiform ore bodies within the pilgrim s rest goldfield the epigenetic stratiform ore bodies are found primarily in the malmani dolomite subgroup a laterally extensive lower proterozoic carbonate platform succession a strong relationship exists between the presence of stratiform ore bodies and environment of deposition and structural deformation analysis of the host sediments indicates deposition in a retrogradational followed by an aggradational sequence that comprises supratidal sabkha siliciclastic sediments to midshelf carbonates the retrogradational and aggradational sequences are characterized by numerous higher frequency transgressive and regressive cycles mineralization is with few exceptions restricted to shallow water siliciclastic sediments deeper water carbonates are barren more importantly siliciclastic mudstones and sandstones have acted as zones of detachment for thin skinned thrust fault deformation resulting in the development of conformable passageways in which fluids concentrated their auriferous lodes evidence of shallow hinterland dipping duplex antiformal stack and imbricate thrust systems abounds in several underground and field exposures the gold silver emplacement model for the pilgrim s rest goldfield infers fluids derived from a deep seated magmatic source oxygen isotopic compositions of the mineralizing fluids recalculated from 18o quartz 12 1 to 19 5 point to a magmatic source and subsequent mixing with saline evolved formation water a magmatic origin is also supported by the high homogenization temperature gradient displayed by the fluid inclusions 100 c km the bushveld igneous complex rustenburg layered suite to the west of pilgrim s rest is thought to be the source of the auriferous hydrothermal solutions and its emplacement was the driving mechanism of thrust fault deformation in the pilgrim s rest goldfield

fluid assisted grain boundary sliding in bedding parallel quartz veins deformed under greenschist metamophic grade abstract iron formation rocks of quadrilatero ferrifero brazil were deformed at greenschist facies quartz grains in bedding parallel veins were sheared and deformed by a combination of mechanisms assisted by aqueous fluids veins in the outcrop appear to be stretched parallel to the compositional layering the overall vein shapes resemble those of boundinage and pinch and swell in thin sections veins show microstructures similar to those observed in hand samples where domains of large quartz crystals are pulled apart for several millimeters the voids between quartz fragments are filled with domains of polycrystalline quartz the microstructural and orientation data show that the strain imposed on the vein as a rigid and competent layer was not accommodated in the quartz polycrystals exclusively by crystal plastic deformation or dynamic recrystallization the new grains are strain free with straight boundaries and with weak to random crystallographic fabrics we interpret these features to have resulted from a combination of processes which included grain boundary sliding accomplished by solution transfer we propose that the coeval operation of both mechanisms allows the aggregate to deform at higher strain rates without necking of the vein layer in a type of flow similar to those described in superplastic regimes

internal kinematics of salt diapirs the internal structure of intrusive and extrusive salt bodies elucidates their external shape and the mechanism and history of diapiric emplacement information relevant to petroleum exploration trace amounts of brine can act like heat to weaken salt and promote geologic creep by solution transfer mechanisms we compare natural strain markers in salt with the artificial markers used by fluid dynamicists stream lines are the smooth flow paths followed by fluid particles stream surfaces separate flow laminae and contain the stream lines grain shape fabrics in salt anneal readily and have strain memories so short that lineations map the stream lines and foliations map the stream surfaces of the last stages of deformation by contrast larger structures like folded beddi g have much longer strain memories as a result multiple generations of tonguelike recumbent flow folds formed by unsteady flow in the mother source layer rotate to upright sheath folds or spines in the stems of diapirs here they are constricted and refolded into steep curtain folds to form crescentic and other interference patterns visible in the roofs of salt mines mature diapirs can form crestal bulbs which may be balloon or mushroom shaped and which potentially form larger petroleum traps than previously supposed screens of country rock may be entrained between the stem and peripheral overhanging lobes caused by episodic sedimentation

greenland ice sheet contribution to sea level rise buffered by meltwater storage in firn observations of firn structure and meltwater retention on the greenland ice sheet s percolation zone a region of the ice sheet that is perennially covered by snow and firn quantify the capacity of the firn to store future surface meltwater and to delay expansion of the area contributing to sea level rise the extent and the fate of surface melt on the greenland ice sheet are important factors contributing to sea level change the pore spaces in firn a type of partly compacted snow can be filled by meltwater and thus act as a temporary reservoir here joel harper et al show that the greenland ice sheet parts of which are permanently covered by snow and firn can buffer several hundred gigatonnes of meltwater for several decades although this buffering capacity is only temporary and cannot be easily regained it has the potential to delay the pace of near term sea level rise surface melt on the greenland ice sheet has shown increasing trends in areal extent and duration since the beginning of the satellite era1 2 3 records for melt were broken in 20054 20075 20106 and 20127 much of the increased surface melt is occurring in the percolation zone a region of the accumulation area that is perennially covered by snow and firn partly compacted snow the fate of melt water in the percolation zone is poorly constrained some may travel away from its point of origin and eventually influence the ice sheet s flow dynamics and mass balance and the global sea level whereas some may simply infiltrate into cold snow or firn and refreeze with none of these effects here we quantify the existing water storage capacity of the percolation zone of the greenland ice sheet and show the potential for hundreds of gigatonnes of meltwater storage we collected in situ observations of firn structure and meltwater retention along a roughly 85 kilometre long transect of the melting accumulation area our data show that repeated infiltration events in which melt water penetrates deeply more than 10 metres eventually fill all pore space with water as future surface melt intensifies under arctic warming a fraction of melt water that would otherwise contribute to sea level rise will fill existing pore space of the percolation zone we estimate the lower and upper bounds of this storage sink to be 322 44 gigatonnes and gigatonnes respectively furthermore we find that decades are required to fill this pore space under a range of plausible future climate conditions hence routing of surface melt water into filling the pore space of the firn column will delay expansion of the area contributing to sea level rise although once the pore space is filled it cannot quickly be regenerated

permian paleoclimate data from fluid inclusions in halite abstract this study has yielded surface water paleotemperatures from primary fluid inclusions in mid permian nippewalla group halite from western kansas a cooling nucleation method is used to generate vapor bubbles in originally all liquid primary inclusions then surface water paleotemperatures are obtained by measuring temperatures of homogenization to liquid homogenization temperatures ranged from 21 c to 50 c and are consistent along individual fluid inclusion assemblages indicating that the fluid inclusions have not been altered by thermal reequilibration homogenization temperatures show a range of up to 26 c from base to top of individual cloudy chevron growth bands petrographic and fluid inclusion evidence indicate that no significant pressure correction is needed for the homogenization temperature data we interpret these homogenization temperatures to represent shallow surface water paleotemperatures the range in temperatures from base to top of single chevron bands may reflect daily temperatures variations these permian surface water temperatures fall within the same range as some modern evaporative surface waters suggesting that this permian environment may have been relatively similar to its modern counterparts shallow surface water temperatures in evaporative settings correspond closely to local air temperatures therefore the permian surface water temperatures determined in this study may be considered proxies for local permian air temperatures

unusually well preserved casts of halite crystals a case from the upper frasnian of northern lithuania abstract upper frasnian carbonate siliciclastics of the stipinai formation northern lithuania comprise a bed of calcareous silty arenite with casts of halite crystals including hopper crystals unusually well preserved casts occur on the lower surface of the bed while poorly preserved casts are present on the upper bedding surface the casts originated as the result of the dissolution of halite crystals which grew in the sediment the dissolution took place during early stages of diagenesis when host sediment was soft unstable cavities after crystal dissolution were filled by overlying sediment forming their casts the collapsing sediment form sink hole deformation structures which disturb wave ripple cross lamination from the upper part of the bed dewatering pipe structures are also present the casts and accompanying sink hole and dewatering pipes are classified as the postdepositional deformation structures caused by haloturbation

contrasting siliciclastic evaporite strata in subsurface and outcrop an example from the permian nippewalla group of kansas u s a abstract geologists tend to expect that rocks as they appear in outcrop are a very good approximation of the same strata in the subsurface but this is not the case in mixed siliciclastic evaporite units strata that contain both a siliciclastic and an evaporite mineral component distinct differences in lithologic and stratigraphic descriptions of ancient siliciclastic evaporite strata exist between outcrop and core these differences present challenges in stratigraphic nomenclature lithologic correlation age determinations and interpretations about past depositional environments diagenetic history and paleoclimate an example of siliciclastic evaporite strata is the middle permian to early triassic gypsum and or anhydrite hereby referred to as gypsum anhydrite and halite bearing red beds throughout the midcontinent of north america and equivalent strata from other pangean deposits here we use core and field observations of the middle permian nippewalla group in kansas to show the range of similarities and differences in lithologies and thicknesses of specific lithofacies in outcrop and at various depths for example the displacive halite lithology consisting of red mudstones dominated by randomly oriented halite crystals is abundant in cores and interpreted as saline mudflat deposits the outcrop counterpart is less common friable massive red mudstones with some gypsum anhydrite pseudomorphs after displacive halite crystals we interpret these lithologic differences of this saline mudflat lithofacies as the result of excellent preservation of buried displacive halite and late stage dissolution of near surface halite additionally bedded halite and intergranular halite cements in siltstones and sandstones are also vulnerable to late stage dissolution near the surface further modifying lithologies and thicknesses thickness of the nippewalla group in the amoco rebecca k bounds core of western kansas is 931 feet 284 meters thick but it is estimated to be only half as thick in the outcrop belt of south central kansas to estimate amount of rock lost to late stage dissolution we conducted dissolution experiments on displacive halite units from cores which resulted in 60 95 loss of rock thickness and mass due to dissolution of halite the unconsolidated red sediment resulting from these dissolution experiments compares favorably with much of the fine massive red siliciclastics that make up the greater part of the nippewalla group outcrops we propose that major lithologic differences resulting from near surface diagenetic processes must be expected in any evaporite bearing siliciclastic unit besides guiding correlation attempts between surface and subsurface this knowledge is vital for making accurate interpretations of depositional and diagenetic history of siliciclastic evaporite units

alluvial playa sedimentation in the lower keweenawan sibley group thunder bay district ontario the middle proterozoic sibley group is a mixed clastic carbonate red bed sequence located in the thunder bay nipigon area on the north shore of lake superior the lowest unit the pass lake forma

temperature seasonality control on modern halite layers in the dead sea in situ observations layered halite sequences are found in deep basins throughout the geological record however analogs for such sequences are commonly studied in shallow environments here we studied active precipitation of halite layers from the only modern analog for deep halite precipitating basins the hypersaline dead sea in situ observations in the dead sea link seasonal thermohaline stratification halite saturation and the characteristics of the actively forming halite layers the spatiotemporal evolution of halite precipitation in the dead sea was characterized by means of monthly observations of 1 lake thermohaline stratification temperature salinity and density 2 degree of halite saturation and 3 textural evolution of the active halite deposits we present the observed relationships between the textural characteristics of layered halite deposits i e grain size consolidation and roughness and the degree of saturation which in turn reflects the limnology and hydroclimatology the lake floor is divided into two principal environments a deep hypolimnetic lake floor and a shallow epilimnetic lake floor in the deeper hypolimnetic lake floor halite continuously precipitates with seasonal variations 1 during summer consolidated coarse halite crystals form rough surfaces under slight supersaturation 2 during winter unconsolidated fine halite crystals form smooth lake floor deposits under high supersaturation these observations support interpretations of the seasonal alternation of halite crystallization mechanisms the shallow epilimnetic lake floor is highly influenced by the seasonal temperature variations and by intensive summer dissolution of part of the previous year s halite deposit which results in thin sequences with annual unconformities this emphasizes the control of temperature seasonality on the characteristics of the precipitated halite layers in addition precipitation of halite on the hypolimnetic floor at the expense of the dissolution of the epilimnetic floor results in lateral focusing and thickening of halite deposits in the deeper part of the basin and thinning of the deposits in shallow marginal basins

variations of near surface firn density in the lower accumulation area of the greenland ice sheet pâkitsoq west greenland firn density variations have been studied in the lower accumulation area of the greenland ice sheet 1440 1620 m a s l near p kitsoq west greenland the main control on density in the near surface firn layer of 5 10 m thickness is the formation of ice layers by the refreezing of meltwater that reaches depths of 2 4 m below the surface the density variations are described by the ratio of annual surface melt m to the annual accumulation c the ratio m c is about 0 6 at the run off limit at about 1400 m a s l in the study area where refreezing of meltwater transforms snow into impermeable ice the mean density of near surface firn decreases with elevation reflecting a decrease in melt with elevation there is a surprising decrease in firn density at depths of more than about 4 m below the 1991 summer surface which reflects lower melt rates and or higher accumulation in the early 1980s and late 1970s when this firn was passing through the surface layer the formation of such low density firn may have partially contributed to the 1978 85 thickening of the ice sheet observed by satellite radar altimetry near surface firn density is therefore very sensitive to climate change and might be an attractive target for climate monitoring

neoarchaean c 2 58 ga halite casts implications for palaeoceanic chemistry possibly the most extensive and best preserved archaean halite casts yet discovered occur in the c 2 58 ga upper black reef and basal oaktree formations transvaal supergroup in mpumalanga province south africa halite casts are isolated on bedding planes range in size from c 1 mm to 20 mm and have cubic dumbbell and triangular shapes as well as hopper like pyramidal hollows on cube faces some of the casts display distinct hopper shapes characteristic of halite crystals the halite cast bearing pavements are developed within silicified mudstone interbedded with siltstone or stromatolitic dolomite associated sedimentary structures pointing to subaerial exposure include adhesion ripples and warts desiccation and prism cracks rill marks and tepee structures halite cast bearing beds are interpreted as supratidal flat or sabkha deposits the presence of isolated casts and hopper shaped crystals suggests that halite resulted from displacive growth within the sediment from supersaturated residual brines after mudstone deposition absence of any indication of the former presence of gypsum or anhydrite supports previous contentions that the neoarchaean ocean was deficient in sulphate or contained a high bicarbonate to calcium ratio such that with progressive evaporation most calcium was consumed before the gypsum stability field was reached the association of halite and carbonate in the upper black reef and basal oaktree formations constrains the palaeolatitude of the transvaal basin at 2 58 ga to subequatorial 10 30

review of aragonite and calcite crystal morphogenesis in thermal spring systems abstract aragonite and calcite crystals are the fundamental building blocks of calcareous thermal spring deposits the diverse array of crystal morphologies found in these deposits which includes monocrystals mesocrystals skeletal crystals dendrites and spherulites are commonly precipitated under far from equilibrium conditions such crystals form through both abiotic and biotic processes many crystals develop through non classical crystal growth models that involve the arrangement of nanocrystals in a precisely controlled crystallographic register calcite crystal morphogenesis has commonly been linked to a driving force which is a conceptual measure of the distance of the growth conditions from equilibrium conditions essentially this scheme indicates that increasing levels of supersaturation and various other parameters that produce a progressive change from monocrystals and mesocrystals to skeletal crystals to crystallographic and non crystallographic dendrites to dumbbells to spherulites despite the vast amount of information available from laboratory experiments and natural spring systems the precise factors that control the driving force are open to debate the fact that calcite crystal morphogenesis is still poorly understood is largely a reflection of the complexity of the factors that influence aragonite and calcite precipitation available information indicates that variations in calcite crystal morphogenesis can be attributed to physical and chemical parameters of the parent water the presence of impurities the addition of organic or inorganic additives to the water the rate of crystal growth and or the presence of microbes and their associated biofilms the problems in trying to relate crystal morphogenesis to specific environmental parameters arise because it is generally impossible to disentangle the controlling factor s from the vast array of potential parameters that may act alone or in unison with each other

paleotemperatures preserved in fluid inclusions in halite a variety of paleoclimate proxy records allow determination of relative warming or cooling however if we are to understand climate change quantification of past temperature fluctuations is essential our research indicates that fluid inclusions in halite can yield homogenization temperatures that record surface brine temperatures at the time of halite precipitation to avoid problems with stretching leaking and initial trapping of air samples with primary single phase liquid fluid inclusions are chilled in a freezer to nucleate vapor bubbles we tested the reliability of this method of obtaining fluid inclusion homogenization temperatures using modern salts precipitated at badwater basin death valley california homogenization temperatures correlate well with measured brine temperatures the same method is applied to fluid inclusions in pleistocene halite from a core taken at the same location in death valley results are at several scales recording diurnal temperature variations seasonal temperature fluctuations and longer term warming and cooling events that correlate with major changes in the sedimentary environment related to climate this technique is uniquely instrumental for paleoclimate studies because it offers actual not just proxy paleotemperature data 27 refs 17 figs

textural features of holocene perennial saline lake deposits of the taoudenni agorgott basin northern mali abstract the holocene salt lake deposits of the taoudenni agorgott basin northern mali mainly consist of sediments with a high glauberite na2ca so4 2 content the remainder of the deposits largely consists of salt beds with a bloedite na2mg so4 2 4h2o thenardite na2so4 or halite nacl composition a petrographical study of the deposits demonstrates that they formed in a perennial lake that experienced a gradual decrease in water depth textural features of the glauberite dominated deposits are found to be related to water depth through the control that this factor exerts on the sensitivity of the lake to changes in water supply and to short term variations in evaporation rates in this way layering due to variations in glauberite content and crystal size is inferred to be typical of deposits that formed in shallow water whereas unstratified deposits are the product of high lake level stages halite textures are found to be indicative of the place within the water column where crystal growth occurred along the lake bottom or higher which is mainly determined by water depth and partly by evaporation rates the oldest halite beds are largely unaltered cumulate deposits whereas the youngest layers developed exclusively through bottom growth the basal part of one thick halite bed at a level between these two groups of halite layers developed by an alternation of both types of growth in response to variations in evaporation rates variations in mineralogical composition between and within the salt beds that formed during the earliest periods with a higher salinity up to the first stage with halite formation record a change in lake water chemistry with time but they are in one instance also determined by an early diagenetic mineral transformation

origin of deformed halite hopper crystals pseudomorphic anhydrite cubes and polyhalite in alpine evaporites austria germany the alpine haselgebirge formation represents an upper permian to lower triassic evaporitic rift succession of the northern calcareous alps eastern alps although the rocksalt body deposits are highly tectonised consisting mainly of protocataclasites and mylonites of halite and mudrock the early diagenetic history can be established from non tectonised mudrock bodies cm sized euhedral halite hopper crystals formed as displacive cubes within mud just during shallow burial the crystals were deformed by subsequent compaction later migrating fluids led to the replacement of halite by anhydrite retaining the shapes of deformed halite cubes polyhalite formed from subsequent enhanced fluid migration mudrock provided water by dewatering while potassium and magnesium were dissolved from primary salt minerals when these fluids interacted with sulphates polyhalite precipitated 40ar 39ar analyses date the polyhalite from within the retaining shapes of deformed halite hopper shaped cubes from two localities to ca 235 232 ma middle triassic at this time ca 20 25 ma after sedimentation polyhalite crystallised at shallow levels

alpine halite mudstone polyhalite tectonite sedimentology and early diagenesis of evaporites in an ancient rift setting haselgebirge formation eastern alps the permian haselgebirge formation of the eastern alps is among the most highly deformed evaporites worldwide in underground salt mines it is composed of a melange of halite anhydrite and mudstone with a subordinate amount of magmatic rocks the only potassium mineral is polyhalite k2ca2mg so4 4 center dot 2h 2 o its extreme tectonic deformation provides a challenge for reconstructing the tectono sedimentary environment in this context we were able to compile a set of characteristic sedimentary and early diagenetic features of the non halite components in particular mudstone and anhydrite pseudomorphs after gypsum preserve synsedimentary structures while mudstone represents the overall background sedimentation sulfate precipitated mainly at the brine surface under pelagic conditions the large amount of mudstone 50 was probably trapped as mud in a quiet lagoonal basin its magnesium dominated mineral composition is in accordance with coeval halite precipitation from seawater earthquake induced deformation structures formed in the semiductile mud sediment as mostly ramified centimeter scale sedimentary dikes which originated intrastratally by liquefaction permian volcanism is documented by a basaltic body from the hallstatt salt mine which exhibits a sedimentary contact with the mudstone its immobile trace element composition favors an intraplate origin consistent with a rift stage during subsequent burial authigenic minerals such as quartz and feldspar started to grow the origin of polyhalite relates to the mobilization of complex fluids and roughly coincides with the final late middle triassic opening of the meliata ocean all evidence from syn sedimentary deformation and early diagenesis confirms the deposition of the evaporites in a late thinning stage of an ancient rift