open co2 underground water system in the west carpathians south poland chemical and isotopic evidence in the open co2 water system 13c of the total dissolved carbonate i e 13c tdc is pco2 and 13c co2 g dependent as tdc is pco2 dependent the variation of 13c tdc in such a system is described by the following equilibrium equation 13c tdc 13c co2 g 1000 0 h2co03 0k1 hco 3 h 0k1k2 co2 3 h 21 h2co03 k1 hco 3 h k1k2 co2 3 h 2 1000 chemical and isotopic data of waters in the west carpathians south poland when subjected to the necessary computation reflect properties of a system open to co2 pco2 of the waters of interest at the earth s surface is close to 1 2 atm their initial chemical speciation has been assigned to this value using program phreeqe then 13c values of dissolved carbonate species in the waters were calculated according to the wigley plummer pearson procedure to obtain the value for 13cf tdc which corresponds to pco2 1 2 atm resulting 13cf tdc values when plotted as a function of tdcf and phf fall well between two curves independently derived for 13c co2 g 1 and 3 and pco2 1 2 atm t 10 c and i 0 1 this implies that waters from the west carpathians are under almost constant co2 pressure and constant 13c co2 g moreover it suggests that a single origin of co2 is quite possible

origin of formation waters of s e parts of the bohemian massif and the vienna basin abstract deep formation waters were sampled from boreholes on the s e slopes of the bohemian massif they are na cl hco 3 waters with tds in the range 6 52 g l 1 some of them are associated with gas and oil deposits the waters are rich in br and i and their dand 18 0 isotope compositions vary from 12 to 77 and 4 6 to 10 respectively the processes of concentration and dilution have been discussed based on deuterium and conservative element contents of the waters three regional groups can be identified in the plots br vs i and cl vs i the vienna basin samples vb southern s and northern n flanks of the bohemian massif bm the vb samples have as an end member brackish water with about 7 g l 1 cl about 40 marine component enriched in br and i this water has been later diluted by meteoric water of recent isotopic composition only 3 vb samples can be considered as derived from the dissolution of evaporites the salt content of the s and n end members is very close to or higher than sea water with an isotopic composition similar to the brackish water subaerial evaporation of diluted sea water is suggested as the process increasing salt content the evaporative enrichment of primary brackish solution can be estimated from extrapolation of cl vs i and br vs i plots to zero i about 25 mg l 1 br and 6 g l 1 cl for the southern flanks of the bm evaporated solutions were later diluted by meteoric waters with d in the range from 50 to 80 southern flanks and about 80 northern flanks

structural geometry and kinematic evolution of the eastern cascades foldbelt washington and british columbia the eastern cascades foldbelt is one of three structural domains lying within the complex collision zone between the insular and intermontane composite terranes in northern washington and southern british columbia the foldbelt resides between the high grade metamorphic backbone of the cascade orogen on the west and rocks of the composite intermontane terrane to the east it encompasses the stratigraphically coherent basalt floored jura cretaceous methow basin as well as more chaotically disposed permian jurassic oceanic rocks of the hozameen terrane methow basin rocks are thought to have been sutured above the oceanic rocks prior to the middle cretaceous contractional episode described in this report based on the analysis presented herein between ca 100 and 88 ma the rocks in the foldbelt underwent shortening in an east northeast west southwest direction by 50 km or more largely by displacement on the east vergent jack mountain chuwanten thrust system the early stages of contraction occurred by

geothermometric and isotopic studies of dehydration waters implications for thermal conditions in the central carpathian synclinorium se poland dehydration type mineralized waters encountered in some places of the central and eastern parts of the polish outer carpathians have been studied for the first time in the light of their usefulness in estimation of thermal conditions of the geological system at regional scale the temperature range of dehydration of mixed layer illite smectite clay minerals estimated at 100 170 c agrees well with thermal conditions of carpathian oil and gas generation as well as coincides with reservoir temperatures estimated by application of mg li na k and na k ca geothermometers i e 88 160 c 50 112 and 79 152 c respectively the discrepancy between actual temperatures at given depths calculated from geothermal gradient and those inferred from chemistry of dehydration waters i e geothermometers and geochemical processes in carpathian geological system strongly supports the idea that the zones of origin of dehydration type waters must be connected with deep parts of the flysch thermal conditions favorable for high temperature water generation occur only in deep parts of the flysch basin or even in the flysch basement temperatures obtained from down hole measurements comparable to those inferred from this study occur at a depth greater than 3000 3500 m moreover cooling down the whole geological system since the period of maximum burial diagenesis is an additional factor reducing geothermal gradient observed nowadays in this part of the carpathian mountains

origin of co2 rich fluid inclusions in leucosomes from the skagit migmatites north cascades washington usa co2 ch4 fluid inclusions are present in anatectic layer parallel leucosomes from graphite bearing metasedimentary rocks in the skagit migmatite complex north cascades washington petrological evidence and additional fluid inclusion observations indicate however that the skagit gneiss was infiltrated by a water rich fluid during high temperature metamorphism and migmatization co2 rich fluid inclusions have not been observed in skagit metasedimentary mesosomes or melanosomes meta igneous migmatites or unmigmatized rocks and are absent from subsolidus leucosomes in metasedimentary migmatites the observation that co2 rich inclusions are present only in leucosomes interpreted to be anatectic based on independent mineralogical and chemical criteria suggests that their formation is related to migmatization by partial melting although some post entrapment modification of fluid inclusion composition may have occurred during decompression and deformation the generation of the co2 rich fluid is attributed to water saturated partial melting of graphitic metasedimentary rocks by a reaction such as biotite plagioclase quartz graphite al2sio5 water rich fluid garnet melt co2 ch4 the presence of co2 rich fluid inclusions in leucosomes may therefore be an indication that these leucosomes formed by anatexis based on the inferences that 1 an influx of fluid triggered partial melting and 2 some episodes of fluid inclusion trapping are related to migmatization by anatexis it is concluded that a free fluid was present at some time during high temperature metamorphism the infiltrating fluid was a water rich fluid that may have been derived from nearby crystallizing plutons because partial melting took place at pressures of at least 5 kbar abundant free fluid may have been present in the crust during orogenesis at depths of at least 15 km

smectite dehydration its relation to structural development and hydrocarbon accumulation in northern gulf of mexico basin a comparison of clay diagenesis data obtained from a study of tertiary shales from the brazos colorado river system of texas the mississippi river system of louisiana and the niger river system of nigeria illustrates significant differences in temperature intervals over which smectite diagenesis occurs the threshold temperature required to initiate diagenesis ranges from about 160 f 71 c in mississippi river sediments to more than 300 f 150 c in the niger delta water expelled from smectite into the pore system of the host shale during the process of diagenesis may migrate out of the shale early or may be totally or partially trapped and released slowly through time in either situation the water can act as a vehicle for hydrocarbon migration p ovided hydrocarbons are present in a form and in sufficient quantities to be transported observations from the northern gulf of mexico basin indicate a close relation between buildup of high fluid pressure and the smectite illite transformation process abnormal pressures exert partial control on the type and quantity of hydrocarbons accumulated because pressure potential determines the direction of fluid flow and overpressuring partly controls the geometry of growth faults and related folds in basins where shale structures are the dominant type formed the depths to which growth faults can penetrate and the angle of dip that these faults assume at depth are largely dependent on fluid pressure in the sedimentary section at the time of faulting dips of some faults in texas have been observed to change abruptly within the interval of smectite diagenesis and some faults formed in the overpressured miocene and younger sections become beddingplane types at depths where the temperature is near that required for thermal generation of petroleum although these faults may be important for fluid redistribution in shallow sandstone shale sections they are a minor factor in moving hydrocarbons out of shale below the faults in much of the texas offshore area fluid movement upward through microfracture systems in the deeply buried overpressured section overlying and extending upward from fault trends in the sub tertiary section is proposed as a mechanism for flushing hydrocarbons from the deeper portion of the northern gulf of mexico basin this flushing process would be enhanced by smectite diagenesis because water derived from smectite that was trapped during basin subsidence would cause the flushing process to continue for longer periods of time and to extend to greater depths than could be attained if only remnants of original pore water were present shale tectonism is also the primary mechanism for structural development in the tertiary section of the niger delta however seismic data indicate that the rate of dip change of seaward dipping listric growth faults is commonly less than that observed in texas where dips as low as 10 15 can occur at depths as shallow as 10 000 15 000 ft 3 048 4 572 m syndepositional faults in nigeria are formed in sandstone shale sections where the clay composition of shale is primarily kaolinite and where little water of smectite diagenesis has been added to the pore system of the host sedimentary section subtle differences in structural styles in the tertiary sections of texas and nigeria are probably the result of differences in clay composition of the shaly sections being deformed

calcium depletion halos and fe mn mg zoning around faceted plagioclase inclusions in garnet from a high grade pelitic gneiss

origin and age of saline waters in busko spa southern poland determined by isotope noble gas and hydrochemical methods evidence of interglacial and pre quaternary warm climate recharges abstract in the busko and solec spas saline sulphide and sulphate waters are exploited at different depths the shallow water system in busko is related to an interglacial or interstadial period shown by the lack of tritium and 14 c and its 18 o and d values equal to that of modern water the noble gas temperatures ngt are somewhat lower than the present air temperatures but the 4 he and 40 ar ages of about 90 480 ka confirm a pleistocene recharge the 18 o and d values of the deep system are much heavier than those of local modern waters which may mean the recharge of a warm pre quaternary climate the 4 he 40 ar and 21 ne contents and the ngt values confirm the deep system to be recharged at the pre quaternary stages of the present hydrologic cycle i e after the sea transgression in the badenian high so 4 2 contents indicate that the cl and so 4 2 in both systems originated from simultaneous leaching of nacl and gypsum other components can be explained by cation exchange between water and badenian clay minerals in marls e g ca 2 for mg 2 and na for k and by the decay of marine organic matter supplying br i and b

metal rich fluid inclusions provide new insights into unconformity related u deposits athabasca basin and basement canada the paleoproterozoic athabasca basin canada hosts numerous giant unconformity related uranium deposits the scope of this study is to establish the pressure temperature and composition p t x conditions of the brines that circulated at the base of the athabasca basin and in its crystalline basement before during and after uo2 deposition these brines are commonly sampled as fluid inclusions in quartz and dolomite cementing veins and breccias associated with alteration and u mineralization microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms data from five deposits rabbit lake p patch eagle point millennium and shea creek complement previously published data for the mcarthur river deposit in all of the deposits investigated fluid inclusion salinity is between 25 and 40 wt nacl equiv with compositions displaying a continuum between a nacl rich brine end member cl na ca mg k and a cacl2 rich brine end member cl ca mg na k the cacl2 rich brine has the highest salinity and shows evidence for halite saturation at the time of trapping the continuum of compositions between the nacl rich brine and the cacl2 rich brine end members combined with p t reconstructions suggest anisothermal mixing of the two brines nacl rich brine 180 30 c and 800 400 bars cacl2 rich brine 120 30 c and 600 300 bars that occurred under fluctuating pressure conditions hydrostatic to supra hydrostatic however because the two brines were u bearing and therefore oxidized brine mixing was probably not the driving force for uo2 deposition several scenarios are put forward to account for the cl na ca mg k composition of the brines involving combinations of seawater evaporation halite dissolution mixing with a halite dissolution brine mg ca exchange by dolomitization na ca exchange by albitization of plagioclase na k exchange by albitization of k feldspar and mg loss by mg rich alteration finally the metal concentrations in the nacl rich and cacl2 rich brines are among the highest recorded compared to present day sedimentary formation waters and fluid inclusions from basin hosted base metal deposits up to 600 ppm u 3000 ppm mn 4000 ppm zn 6000 ppm cu 8000 ppm pb and 10 000 ppm fe the cacl2 rich brine carries up to one order of magnitude more metal than the nacl rich brine though the exact origin of major cations and metals of the two brines remains uncertain their contrasting compositions indicate that the two brines had distinct flow paths and fluid rock interactions large scale circulation of the brines in the athabasca basin and basement was therefore a key parameter for metal mobility including u and formation of unconformity related u deposits

nature of the contact zone between the north cascades crystalline core and the methow sequence in the ross lake area washington implications for cordilleran tectonics previous analyses of the accretionary history of nw washington sw british columbia have suggested the possibility of large scale dextral slip faulting events to explain the present day regional outcrop pattern the contact zone between the crystalline skagit complex and the volcano sedimentary methow sequence has been considered to be a major fault named the ross lake fault by misch 1966 and has been considered to be a possible large scale strike slip fault by later workers detailed mapping of this contact zone in the ross lake area shows that the brittle faults and mylonites thought by misch to express dextral shearing along the contact are not continuous throughgoing structures and that the contact between skagit orthogneisses and methow sequence strata is primarily intrusive furthermore the mylonites show both left and right lateral shear the skagit methow contact is therefore not a major terrane boundary but rather a tectonized intrusive contact that has not accommodated significant motion between the two regions based on these observations and regional synthesis of timing relations deformation in the contact zone is interpreted to express regional ene wsw shortening not major dextral slip in the early tertiary since no terrane bounding fault exists the cretaceous tertiary history of the ross lake area can be interpreted as follows 1 jurassic early cretaceous forearc rift basin sedimentation deposition of the lower methow sequence 2 110 95 ma imbrication of the lower methow sequence and its basement of oceanic crustal rocks by east vergent thrusting with concomitant development of a west derived foredeep in the upper methow sequence 3 95 85 ma arc magmatism with genesis of the skagit migmatite from methow and older basement protoliths and 4 paleocene early eocene folding faulting uplift and exposure of a relatively intact 25 km crustal section termed the skagit methow crustal section by kriens and wernicke 1987

modelling fresh water injection into a partially saline partially fresh paspaf aquifer abstract this paper concerns the study of physical phenomena typical to injection of fresh water like treated effluents into an aquifer whose deep layers are saturated with saline water and its upper layers are saturated with fresh water such a partially saline partially fresh aquifer is termed by the present paper as a paspaf aquifer the study concerns infiltration by recharge wells as well as over an infiltrating area the framework of the present study includes the development of the appropriate numerical model as well as the performance of various numerical simulations demonstrating the applicability of the model and representing the possible physical phenomena associated with the fresh water injection the numerical model is able to simulate the downconing process and the formation of the transition zone in the aquifer the numerical experiments with the model indicate that the fresh water injection may lead to degradation of the groundwater quality mainly around the injection site quantitative calculations of such an effect and the appropriate conclusions obtained by these calculations are represented in this paper

origin of natural waters and gases within the upper carboniferous coal bearing and autochthonous miocene strata in south western part of the upper silesian coal basin poland abstract the molecular and stable isotope compositions of coalbed gases from the upper carboniferous strata and natural gases accumulated within the autochthonous upper miocene skawina formation of the debowiec simoradz gas deposit were determined as well as the chemical and stable isotope compositions of waters from the skawina formation and waters at the top of the upper carboniferous strata of the kaczyce ridge the abandoned morcinek coal mine in the south western part of the upper silesian coal basin two genetic types of natural gases within the upper carboniferous coal bearing strata were identified thermogenic ch4 small amounts of higher gaseous hydrocarbons and co2 and microbial ch4 very small amounts of ethane and co2 thermogenic gases were generated during the bituminous stage of coalification and completed at the end of the variscan orogeny degassing desorption of thermogenic gases began at the end of late carboniferous until the late miocene time period and extended to the present day this process took place in the upper carboniferous strata up to a depth of about 550 m under the sealing upper miocene cover a primary accumulation zone of indigenous thermogenic gases is present below the degassing zone up to 200 m depth from the top of the upper carboniferous strata within the weathered complex an accumulation zone of secondary microbial gas occurs waters within these strata are mainly of meteoric origin of the infiltration period just before the last sea transgression in the late miocene and partly of marine origin having migrated from the upper miocene strata then both methanogenic archaebacteria and their nutrients were transported by meteoric water into the near surface carboniferous strata where the generated microbial ch4 saturated coal seams waters within the miocene strata of the debowiec simoradz and zablocie are of marine origin and natural gases accumulated within autochthonous miocene strata of the debowiec simoradz gas deposit were most probably generated by microbial processes of on organic matter dispersed within the strata though some contribution of gases migrating from the carboniferous coal bearing strata cannot be excluded

theory and application of an approximate model of saltwater upconing in aquifers abstract motion and mixing of salt water and fresh water are vitally important for water resource development throughout the world an approximate model of saltwater upconing in aquifers is developed which results in three non linear coupled equations for the freshwater zone the saltwater zone and the transition zone the description of the transition zone uses the concept of a boundary layer this model invokes some assumptions to give a reasonably tractable model considerably better than the sharp interface approximation but considerably simpler than a fully three dimensional model with variable density we assume the validity of the dupuit forchheimer approximation of horizontal flow in each layer vertical hydrodynamic dispersion into the base of the transition zone is assumed and concentration of the saltwater zone is assumed constant solute in the transition zone is assumed to be moved by advection only velocity and concentration are allowed to vary vertically in the transition zone by using shape functions several numerical techniques can be used to solve the model equations and simple analytical solutions can be useful in validating the numerical solution procedures we find that the model equations can be solved with adequate accuracy using the procedures presented the approximate model is applied to the smoky hill river valley in central kansas this model can reproduce earlier sharp interface results as well as evaluate the importance of hydrodynamic dispersion for feeding salt water to the river we use a wide range of dispersivity values and find that unstable upconing always occurs therefore in this case hydrodynamic dispersion is not the only mechanism feeding salt water to the river calculations imply that unstable upconing and hydrodynamic dispersion could be equally important in transporting salt water for example if groundwater flux to the smoky hill river were only about 40 of its expected value stable upconing could exist where hydrodynamic dispersion into a transition zone is the primary mechanism for moving salt water to the river the current model could be useful in situations involving dense saltwater layers

the occurrence of a secondary zone of coal bed methane in the southern part of the upper silesian coal basin southern poland potential for methane exploitation abstract coal bed methane cbm exploitation in the upper silesian coal basin has in spite of earlier failures again aroused investor interest carboniferous coal seams at depths of 200 500 m are characterized by coal permeability values estimated at 27 230 md and degrees of methane saturation almost 100 that suggest future successful exploitation based on the results of geological surveys archived in the polish geological institute the shallow cbm zone is defined as a gas horizon distinct from a deep cbm zone the disposition of the shallow zone follows the topography of the upper carboniferous paleorelief and is deemed the most important factor controlling methane distribution within this zone the most favorable places for cbm accumulation within the shallow coal seams are erosional highs and the slopes of upper carboniferous ridges associated with fault zones the thickness of the zone 200 m and methane contents 8 m 3 t coal daf are highest in these places the nearly full saturation of the coal seams with methane reflects the involvement of two genetic types of gas indigenous late stage microbial methane and thermogenic methane derived from the deeper coals the favorable geological characteristic of this shallow cbm zone is a potential source of energy for upper silesia

nature of mixed layer clays and mechanisms of their formation and alteration abstract mixed layer clay minerals are intermediate products of reactions involving pure end member clays they come from natural environments ranging from surface to low grade metamorphic and hydrothermal conditions most often mixed layering is essentially two component but more complicated interstratifications have also been documented variable tendency to form regular 1 1 interstratifications has been observed and explanations of this phenomenon have been proposed mixed layer clays are either di or trioctahedral di trioctahedral interstratifications are rare most mixed layer clays contain smectite or vermiculte as a swelling component exceptions are all trioctahedral serpentine chlorite in low temperature environments and mica chlorite and talc chlorite at high temperatures solid state transformation and dissolution crystallization are the two mechanisms responsible for the formation of different mixed layer clays in general the weathering reactions that produce mixed layering are revers

origin of brines in the upper silesian coal basin poland inferred from stable isotope and chemical data brines in the miocene formations of the upper silesian coal basin have isotopic composition close to smow which identifies them as the connate marine water however controversies exist on the origin of brines in the carboniferous formations isotopic and hydrochemical data exclude any relationship to marine water and enrichment by evaporation the most common brine which occurs at great depths can be identified as the oldest infiltration in a very hot climate 18o 2 d 20 cl content 34 to 140 g l this brine is free of so42 and u and rich in ba2 and226ra its salinity is probably related to the leaching of evaporites and intensive weathering of rocks during the rotliegendes other brines are difficult to identify because their isotopic contents are within the range of mixing between the oldest brine and the quaternary waters 18o 10 d 70 isotopic and hydrochemical data allow identification of several occurrences of brine formed by meteoric water of a warm tertiary climate after the last marine transgression in the tortonian that brine is rich in so42 and contains moderate contents of226ra and u its salinity is thought to result from leaching of miocene evaporites two other identified types of brines can be related to some infiltration periods before the last marine transgression the sources in salinity of these 2 types remain unknown mining activity results in a common occurrence of mixed brines when the quaternary component dominates its identification is easy from the isotopic composition whereas the end brine component can ususally be identified by chosen ion ratios and the presence or lack of sulphates

a middle jurassic to early tertiary andean sierran arc model for the coast belt of british columbia regional tectonic features of the western canadian cordillera can be interpreted in terms of middle jurassic accretion of a single composite superterrane stikinia wrangellia alexander to ancestral north america closure of the intervening cache creek bridge river ocean moved the continental edge to a new position west of the accreted superterrane the coast belt is primarily a succession of superimposed middle jurassic to early tertiary magmatic arcs related to prolonged subduction of pacific ocean lithosphere beneath the new north american margin discrete magmatic pulses separated by lulls or periods of relative quiescence successively overprinted the new margin the insular and intermontane superterranes previously viewed as widely separate entities prior to mid cretaceous time were already amalgamated before an initial middle jurassic overprint produced an ancestral coast belt late jurassic to early cretaceous rift related marine basins mid to late cretaceous compressional structures and early tertiary extensional features coincident with the coast belt are subsidiary intraplate attributes that reflect external adjustments in plate motions within a primary subduction related andean magmatic arc

the occurrence and behavior of radium in saline formation water of the u s gulf coast region abstract radium has been measured in deep saline formation waters produced from a variety of u s gulf coast subsurface environments including oil reservoirs gas reservoirs and water producing geopressured aquifers a strong positive correlation has been found between formation water salinity and ra activity resulting from the interaction of formation water with aquifer matrix ra isotopes enter the fluid phase after being produced by the decay of parent elements u and th which are located at sites on and within the solid matrix processes that are belived to be primarily responsible for transferring ra from matrix to formation water are chemical leaching and alpha particle recoil factors controlling the observed salinity ra relationship may be one or a combination of the following factors a ion exchange b increased solubility of matrix silica surrounding ra atoms coupled with a salinity controlled rate of reequilibration of silica between solution and quartz grains and c the equilibration of ra in solution with detrial barite within the aquifer no difference was found in the brine ra relation in water produced from oil or gas wells and water produced from wells penetrating only water bearing aquifers although the relation was more highly correlated for water bearing aquifers than hydrocarbon containing reservoirs

characterizing thermogenic coalbed gas from polish coals of different ranks by hydrous pyrolysis abstract to provide a better characterization of origin and volume of thermogenic gas generation from coals hydrous pyrolysis experiments were conducted at 360 c for 72 h on polish coals ranging in rank from lignite 0 3 r r to semi anthracite 2 0 r r under these conditions the lignites attained a medium volatile bituminous rank 1 5 r r high volatile bituminous coals attained a low volatile bituminous rank 1 7 r r and the semi anthracite obtained an anthracite rank 4 0 r r hydrous pyrolysis of a coal irrespective of rank provides a diagnostic 13 c value for its thermogenic hydrocarbon gases this value can be used quantitatively to interpret mixing of indigenous thermogenic gas with microbial methane or exogenous thermogenic gas from other sources thermogenic methane quantities range from 20 dm 3 kg of lignite 0 3 r r to 0 35 dm 3 kg of semi anthracite 2 0 r r at a vitrinite reflectance of 1 7 r r approximately 75 of the maximum potential for a coal to generate thermogenic methane has been expended at a vitrinite reflectance of 1 7 r r more than 90 of the maximum potential for a coal to generate co 2 has been expended assuming that these quantities of generated co 2 remain associated with a sourcing coal bed as uplift or erosion provide conditions conducive for microbial methanogenesis the resulting quantities of microbial methane generated by complete co 2 reduction can exceed the quantities of thermogenic methane generated from the same coal bed by a factor of 2 5

isotopic geochemistry of burial metamorphosed volcanogenic sediments great valley sequence northern california isotopic and mineralogic data from an 8500 m thick section of the great valley sequence northern california indicate that changes in the 18o values of authigenic minerals resulted from the conversion of smectite to a 10 a clay mineral as temperature increased with burial in the jurassic cretaceous outer arc basin the clay mineral assemblage in mudstone is characterized by a proportional increase of the 10 a clay mineral with increasing stratigraphic depth and by a depletion in the 18o value of the mixed layer smectite 10 a clay mineral with descending stratigraphic position from 21 9 to 15 5 smow modeling of the oxygen isotopic data from authigenic phases based on equilibrium fractionation during clay mineral diagenesis indicates that 18o values of calcite in mudstones and of calcite cements in sandstone precipitated along a temperature gradient of about 25 c km during maximum burial to about 6 7 km d values of the mixed layer smectite 10 a clay mineral range between 69 to 44 smow using temperatures calculated from the oxygen isotopic data the deuterium and oxygen isotopic data indicate that the smectite underwent late stage dehydration and probably buffered the composition of formation waters from sea water values to isotopic compositions of 18o 8 smow and d 25 smow the 13c values of calcite from mudstone and sandstone imply that crystallization of authigenic calcite was linked to organic diagenesis during which dissolved hcot 3 was continuously enriched in 13c as temperature increased with burial at the base of the sequence and immediately overlying the ophiolitic basement rocks several hundred meters of strata were altered by more oxygen depleted 18o 4 to 5 hydrothermal fluids emanating from the ophiolitic rocks probably at maximum burial depth

interplay of plutonism and regional deformation in an obliquely convergent arc southern coast belt british columbia the coast plutonic complex is an extensive zone of continental growth that formed along the mesozoic convergent margin of northwestern north america the orogeny creating this belt involved terrane accretion and assembly massive upward transfer and emplacement of sial in the form of batholiths constituting a magmatic arc and transformation of broad tracts of sedimentary and volcanic rocks into crystalline continental crust all operating in more or less the same space and time the mechanisms and interplay of these orogenic processes are well displayed in the harrison lake area of the southern coast belt british columbia great structural relief across the area exhibits a present day architecture defined by thin thrust stacked terrane sheets and early concordant pluton sheets folded on a macroscopic scale all truncated by oblique dextral reverse faults and overlain by later floored plutons construction of this complex began with terrane assembly on orogen normal thrusts during a lull in plutonism in the early cretaceous low grade metamorphism during this event indicates only modest crustal thickening subsequent plutons intruded into the assembled terranes appear to be composites of sheets early pluton sheets are now steeply dipping due to folding but were likely intruded as horizontal bodies large ovoid post folding plutons are mostly subhorizontal floored bodies at least in part sheeted these plutons are underlain by barrovian mineralogic aureoles that indicate downward vertical displacement of 10 km or more during plutonism suggesting pluton emplacement by vertical inflation magmatic fabrics in these bodies and the discordant relation of plutons to regional structures preclude emplacement in active fault zones penetrative strain aureoles flanking plutons are mostly limited to zones a few hundred meters wide and regional tectonic structures are widely preserved tectonic deformation of the arc is characterized by contraction and strike slip not orogen normal extension plutons played a greater role than terrane accretion in causing crustal thickening and high grade metamorphism

high pressure metamorphism in the western cordillera of north america the skagit gneiss a major component of the crystalline core of the north cascades was metamorphosed during a mid cretaceous to early tertiary high p event driven by the collision of the insular and intermontane superterranes maximum pressures recorded by metapelitic rocks are 8 10 kbar at 650 725 c high pressures are also indicated by coexisting staurolite and hornblende in amphibolites in the skagit gneiss and adjacent cascade river schist mineral reactions continued during nearly isothermal decompression from 8 10 kbar to c 3 5 kbar early high p minerals e g kyanite are present as armoured relics in garnet in gneisses that contain sillimanite and cordierite in the groundmass skeletal relics of kyanite are also present in the groundmass of lower grade staurolite bearing schists that contain texturally later cordierite this matrix kyanite may have been preserved as a result of rapid uplift following initial decompression at high temperature these results represent a revision of the metamorphic history of the skagit gneiss which was formerly thought to have experienced only relatively low p barrovian metamorphism qualitative estimates of metamorphic conditions based on stable matrix mineral assemblages result in an underestimation of maximum pressures because mineral reactions continued during decompression geobarometric results for the skagit gneiss are interpreted as evidence for major crustal thickening in the north cascades recognition that pressures of c 9 kbar were attained supports a contractional model for north cascades orogenesis and requires that tectonic syntheses account for the burial of the skagit gneiss protoliths to a depth of c 25 30 km

aqueous sulphates from the stripa groundwater system abstract the isotopic composition of aqueous sulphate in the groundwater in the stripa pluton reflects the geochemical history of the groundwater as well as the origin of the sulphur or sulphate in shallow modern groundwater sulphate originates from fallout and the oxidation of pyrite or other reduced forms of sulphur at intermediate depths sulphate of surface origin is lost through bacterial reduction the origin of sulphate of the deep and more saline water is not clearly defined but could be derived from a sedimentary brine which was subject to substantial modification through rock water interaction bacterial sulphate reduction also occurs locally at depths below about 800 m

diagenetic and other highly mineralized waters in the polish carpathians abstract highly mineralized waters of different chemical types and origin occur in the flysch formations and their bedrocks in the western part of the polish carpathians the marine sedimentation water of the flysch formations is not preserved as the most mineralized and the heaviest isotopic values of flysch waters are characterized by 18 o and 2 h values in the ranges of 5 7 and 20 30 respectively their origin is related to the dehydration of clay minerals during burial diagenesis with molecules of marine water completely removed by molecules of released bound water they are relatively enriched in na in respect to the marine water supposedly due to the release of na during the illitization of smectites and preferable incorporation of other cations from the primary brine into newly formed minerals in some parts of younger formations i e in the badenian sediments brines occur with isotopic composition close to smow and cl contents greatly exceeding the typical marine value of about 19 6 g l supposedly due to ultrafiltration most probably the marine water of the flysch formations was similarly enriched chemically in its initial burial stages final cl contents in diagenetic waters depend on different cl contents in the primary brines and on relationships between diagenetic and further ultrafiltration processes in some areas diagenetic waters migrate to the surface along fault zones and mix with young local meteoric waters becoming diluted with the isotope composition scattering along typical mixing lines in areas with independent co 2 flow from great depths they form chloride co 2 rich waters common co 2 rich waters are formed in areas without near surface occurrences of diagenetic waters they change from the hco 3 ca type for modern waters to hco 3 mg ca hco 3 na ca and other types with elevated tds mg 2 and or na contents for old waters reaching even those of glacial age bedrocks of the flysch are represented by mesozoic and paleozoic mudstones sandstones and carbonates and in some areas by badenian sediments brines of the mesozoic and paleozoic bedrocks are usually significantly enriched in ca 2 and mg 2 in comparison with the badenian brines by analogy to the deepest brines in the adjacent upper silesian coal basin they are supposed to originate from paleometeoric waters of a hot climate

geochemistry and origin of formation brines from the paris basin france 2 saline solutions associated with oil fields abstract oil fields from the paris basin are located in three geological levels dogger middle jurassic rhaetian and keuper upper triassic the origin of water and dissolved salts in saline solutions associated with oil is investigated using the hypothesis that cl and br are conservative in solution in a diagram of cl br ratios vs cl the points of the dogger and the keuper aquifers lie in the zone of primary brines whereas those of the rhaetian are located in the zone of secondary brines the na cl ratio is very high in all of the saline solutions suggesting either a relatively poorly evolved brine at the beginning of halite deposition or some halite dissolution all of the saline solutions especially those from the dogger aquifer are clearly diluted dilution by meteoric waters would not alter the cl br ratio high concentrations of lithium rubidium and boron are attributed to the presence of an extremely evolved brine of marine origin in mixtures of secondary brines formed by dissolution of halite and small amounts of sylvite and ca sulphate mass balance calculations of the excess of cl with respect to na k allows the fraction x of water derived from the primary brine to be calculated assumptions are that all na and k is derived from the secondary brine and that the cl content of the primary brine is constrained by bischofite saturation at 11 000 mmol kg 1 the typical proportion of water from the primary brine waters is 0 7 in the dogger formation and 2 4 in the keuper values of the concentration factor cf expressed as the ratio of the molal concentration of a conservative ion in the evolved brine to its concentration in seawater have been calculated for lithium solutions from the dogger and keuper aquifers have cfli values of 1 8 103 and of 7 7 103 respectively in the rhaetian aquifer the linear relationship between heavy isotope contents of the brine 2h and 18o and the cl content indicates a mixture of two water sources the first one is meteoric water as defined by the intersection of the formation water line with the global meteoric water line 2 h 65 18 o 9 3 the other end member is enriched in heavy isotopes and in cl and is attributed to seawater that has dissolved evaporites mainly halite however the presence of small amounts of an extremely evolved brine is required to account for the bromide lithium rubidium and boron contents of the formation brine from the rhaetian aquifer as this contribution is very limited in amount it cannot affect the heavy isotope content of the formation water mass balance equations are solved for ternary mixtures of meteoric water seawater and brine the same constraints as above no na and k supplied by the primary brine and clbrine 11 000 mmol kg 1 are applied it is also assumed that the seawater component has the same ionic contents as modern seawater and that the salt content of the meteoric component is negligible the fraction of primary brines is x 1 4 according to the cl balance this estimate agrees with that obtained from the lithium balance assuming that the primary brine component was the same as that of the keuper formation water mass balance calculations also indicate that the so42 content of the rhaetian formation water is exclusively due to the secondary brine component in the three saline solutions the very high ca2 contents and high ca 2 mg 2 ratios may be attributed to reaction of the very evolved brine free of so2 4 with gypsum or anhydrite the result is an exchange of mg2 for ca2 which causes a release of ca2 to the solution and a precipitation of secondary mg sulphate this process can also account for the high strontium contents of the analysed samples values of the ratio 87 sr 86 sr are very high in the keuper formation water due to close contact of the solutions with the granitic basement or with granite derived detrital deposits values in the rhaetian and dogger aquifers equal those of upper triassic marine deposits the stable isotope 34s and 18o content of the dissolved aqueous so2 4 indicates a triassic origin for the bulk of sulphate involved in the evolution of formation waters from the rhaetian and from the dogger all geochemical indicators thus show a vertical migration of triassic brines however aqueous so2 4 from the keuper has a permian isotopic signature suggesting a reworking in solution of salts from this period

analysis of saltwater upconing beneath a pumping well abstract aquifer systems that contain freshwater and saltwater are usually stratified with the more dense saltwater underlying the freshwater a groundwater well discharging from the freshwater zone causes the saltwater to move upwards towards the well this phenomenon is known as saltwater upconing two methods of analysis the sharp interface method and the fluid density dependent solute transport method are used to simulate saltwater upconing numerical experiments including comparisons of the two methods indicate 1 for low to moderate pumpages the 50 isochlor and sharp interface correlate well 2 the well can discharge significant concentrations of saltwater even though a stable cone according to the sharp interface method exists below the well screen 3 an almost linear relationship exists between the well discharge rate and the concentration of the discharge at low pumping rates that maintain a stable cone and 4 upconing is sensitive to transverse dispersivity whereas it is insensitive to longitudinal dispersivity a simulation of upconing at test site no 4 truro cape cod massachusetts indicates that the appropriate field value of transverse dispersivity is very small this supports the validity of the sharp interface assumption for analyzing the behavior of systems with thin saltwater freshwater transition zones

occurrence and use of mineral and thermal waters in poland mineral and thermal waters are defined according to polish geological and mining law their occurrence in particular hydrogeological provinces of the country is characterized besides their use in balneotherapeutics their role as a heat carrier and source of chemical raw materials is stressed topics mentioned requiring further research are the origin of saline formation waters and the origin of co2 in carbonated waters

stable sulfur and oxygen isotope ratios of the świetokrzyski national park spring waters generated by natural and anthropogenic factors south central poland abstract this paper presents the results of an isotopic study of spring waters in wietokrzyski holy cross mountain national park np south central poland the 34 s v cdt and 18 o v smow of soluble sulfates n 40 varied from 0 5 to 18 1 and from 3 5 to 12 2 respectively the average 34 s values are closely similar to those of rainwater soils and rocks comprising scattered pyrite this suggests that soluble sulfates in the springs originated from mixing of recent and historic deposition sulfates derived from pyrite oxidation and cs mineralization in soils and debris an additional anthropogenic sulfur input inorganic fertilizer occurs in the water of spring s 61 located in the wietokrzyski national park buffer zone the 18 o v smow of spring waters n 4 were in the range of 10 6 to 10 2 indicating that they are derived from vadose groundwater in np this was the first isotope study of spring waters in the national parks of poland it enabled the determination of sulfur pathways and discrimination between natural and anthropogenic sources of this element in a relatively pristine area

extensive microbial modification of formation water geochemistry case study from a midcontinent sedimentary basin united states the upper devonian antrim shale in the michigan basin is an economically significant source of microbially produced methane along the basin margins where meteoric recharge has been focused oxygen and hydrogen stable isotope compositions of antrim formation waters show that fresh waters recharged from pleistocene glaciation and modern precipitation suppressed basinal brine salinity to great depths and enhanced methanogenesis this paper presents results of integrated elemental and isotope analyses of antrim shale formation waters from the margins and center of the michigan basin focusing on solute sources and geochemical modifications associated with regionally extensive microbial methanogenesis cl br na systematics reveal that salinity is controlled not only by mixing between variable amounts of basinal brine and meteoric water but also by halite dissolution where fluids recharged through underlying devonian carbonate aquifers with localized evaporite deposits divalent cations carbonate system parameters and carbon isotope compositions of dissolved inorganic carbon have been systematically and profoundly altered by microbial methanogenesis large decreases in formation water ca mg and ca sr ratios accompany increasing carbonate alkalinity values in areas with high rates of microbial gas production thermodynamic and reaction path modeling show that these changes are consistent with calcite precipitation during progressive microbial methanogenesis similar variations in fluid chemistry are evident in databases from other sedimentary basins containing black shales and coal beds associated with microbial gas microbial methanogenesis may play an important role in the geochemical evolution of divalent cation relationships in crustal fluids and should be considered in models of formation water origin and evolution

p t t evidence for mechanisms of vertical tectonic motion in a contractional orogen north western us and canadian cordillera the 1800 km long coast mountains north cascades orogen of the canadian cordillera and north western us developed as a continental magmatic arc metamorphic rocks in the orogen contain widespread evidence for burial of supracrustal rocks to depths of c 40 km followed by nearly isothermal decompression to depths of 10 km near many shallowly emplaced mid cretaceous plutons low pressure contact metamorphic effects were overprinted by high pressure regional metamorphic minerals and textures as evidenced by kyanite staurolite pseudomorphs after andalusite in metapelitic rocks therefore near pluton rocks record the loading history of the orogen metapelitic rocks not associated with plutons only preserve evidence for high pressure conditions and or high temperature decompression as indicated for example by sillimanite and cordierite after kyanite and garnet respectively petrological evidence for burial and decompression is therefore recorded in different rocks various regions of the orogen differ in timing of metamorphism the overall shape of p t paths and the relative timing and regional extent of the high pressure event but most of these data and observations are consistent with thrusting and or pure shear thickening as primary loading mechanisms throughout the orogen as opposed to magma dominated loading this interpretation is further supported by comparison with thermal models which demonstrate that the p t paths are consistent with simultaneous thrusting and folding at a high initial geothermal gradient 35 40 c km 1 in much of the orogen a high geothermal gradient supports tectonic models invoking intra arc contraction and suggests that magmatism played an important role in regional temperature time paths this tectonic thermal history may be typical of other contractional orogens and illustrates the importance of large vertical displacement of crust in magmatic arcs

comment on mid cretaceous thrusting in the southern coast belt british columbia and washington after strike slip fault reconstruction by paul j umhoefer and robert b miller

transverse dispersion of contaminants in fractured permeable formations abstract our interest in understanding some of the mechanisms involved in the mineralization of the great bend prairie aquifer of kansas by salt water originating from permian bedrock formations which are fractured sandstones has prompted this basic study the fractured permeable formatiodis represented by a simplified conceptual model incorporating two sets of oblique and parallel fractures embedded in permeable blocks the domain is initially divided into a completely freshwater zone overlying a completely saline water zone however the sharp interface originally existing between the saline and fresh water is subject to dispersion because of mixing in fracture intersections and between the fracture flow and the permeable block flow simulations based on the use of an appropriate numerical model developed in the present study have helped us to characterize dispersion of the sharp interface and creation of the transition zone relationships of transverse and longitudinal dispersion in the domain are also determined

chemical osmosis reverse chemical osmosis and the origin of subsurface brines abstract calculations using recently tabulated values of density and osmotic coefficient for nacl h2o indicate that overpressuring is more than adequate to overcome chemical osmosis and drive reverse chemical osmosis in sedimentary sequences the best demonstrated overpressuring mechanism is the rapid deposition of fine grained sediments the dehydration of gypsum contributes to overpressuring for brief time intervals at shallow depths whereas water evolved during the protracted conversion of smectite to illite is probably a subordinate but continuing contributor to overpressuring at greater depth occurrences of overpressuring in sedimentary sections older than cretaceous indicate that post depositional mechanisms such as tectonic compression and aquathermal pressuring must also operate the latter may be of major importance in geothermal areas with adequate low permeability seals and a nontrivial contributor in areas of normal geothermal gradient because of shales that sharply decrease normal fluid flow the strongest arguments for the importance to present day brine compositions of membrane concentration of sea water solutes are 1 1 the correlation of d values of water molecules of pore fluid with those of local meteoric water 2 2 the need for major sources of mg2 and cl in apparently evaporite free basins even where dissolution of halite is a major contributor of solute reverse chemical osmosis still operates to leak relatively dilute water of the associated diagenetic chemical reactions that of mg2 with limestone to form dolomite is particularly effective in generating concentrated cl brines rich in ca2 it decreases the concentration of mg2 increases that of ca2 and decreases those of both so42 and co32 by precipitating caco3 and caso4 because of the ca2 common ion effect

barium and radium discharged from coal mines in the upper silesia poland waters discharged from coal mines in the upper silesia in poland cause contamination of rivers and their sediments saline waters discharged from coal mines of the southern region contain elevated barium and radium the discharge of these elements can be reduced by treating these waters with sulphates in mine workings sources of sulphate used in treatments include gypsum anhydrite and industrial wastes such as fly ash slags and flotation tailings gypsum and anhydrite are used in the coal mine workings as components of the fire protection walls industrial wastes from power plants are stored in the mine workings as fire and methane protection agents sulphates precipitate barium and radium from saline waters inflowing into the mine workings the waters can be treated by flowing them through old mine workings in this case the source of sulphates is the natural oxidation of pyrite mining activities and the natural process of desulphurisation of the carboniferous rocks reduce the amount of barium and radium that is discharged in the southern region of upper silesia the processes for reducing the environmental impact of toxic discharges from the mines should be monitored

motion of the seawater interface in a coastal aquifer by the method of successive steady states abstract the paper describes a method for determining the motion of the seawater interface in a phreatic coastal aquifer during a specified time period in response to changing hydrologic conditions provided a seaward flow of fresh water is maintained everywhere above the interface the method of successive steady states is used leading to an approximate analytical expression which gives the motion of the interface toe during the time period as a function of the initial conditions and the change in freshwater flow to the sea above the toe during the time period sensitivity of the results to values of parameters and to hydrologic conditions is investigated and the results are compared with those obtained by other methods of analysis the motivation for developing the approximate analytical expression for movement of the interface was to facilitate the introduction of seawater intrusion as a criterion in the multiobjective management model for coastal aquifers

constraints on the hydrogeochemistry and origin of the co2 rich mineral waters from the eastern carpathians transylvanian basin boundary romania abstract the eastern carpathians along the neogene to quaternary volcanic chain host important natural resources of mineral waters most of these are in the form of co2 rich natural springs of different types associated with co2 gas emissions in order to understand the origin of these waters the natural processes responsible for the observed physical chemical features and to check the exposure and vulnerability of the hydrogeological system to potential contamination and environmental changes 121 mineral water springs and wells were investigated the investigations performed offered an insight on the processes affecting the waters after their infiltration that led to a wide range of chemical and isotopic compositions the diversity in the geological structure of the area alteration processes and interaction with co2 all explain the variety of the hydrogeochemical facies of the investigated waters three major hydrogeochemical types that are the result of the geological variety of the study area and water rock interaction were identified ca na mg hco3 ca na mg na ca mg hco3 cl so4 and na cl waters further changes in the geochemical features are attributable to mixing between different water types during their ascent enhanced by the tectonic setting of the area considering the isotopic composition 18o d of the waters most of them proved to be of meteoric origin extreme isotopic shifts towards enriched 18o and d values of 8 59 and 12 2 v smow respectively were observed in the case of 11 springs these shifts were attributed to the interaction of water with clay minerals and diagenesis as most of these waters are of meteoric origin their discharge may be influenced by meteorological factors moreover the mixing of aquifers with very shallow waters most likely facilitates their exposure to external contamination

hydraulic parameters and solute velocities in triple porosity karstic fissured porous carbonate aquifers case studies in southern poland rock and flow parameters of three karstic fissured porous aquifers in the krakow silesian triassic formations were measured using various methods and compared though cavern and fissure porosities are shown to be very low cavern porosity below 0 5 and fracture porosity below 0 2 they contribute dominantly to the hydraulic conductivity from about 1 3 10 6 to about 11 10 6 m s matrix porosity 2 11 is shown to be the main water reservoir for solute transport and the main or significant contributor to the specific yield 2 though the matrix porosity is shown to be much larger than the sum of the cavern and fissure porosities its contribution to the total hydraulic conductivity is practically negligible hydraulic conductivity of the matrix is from about 5 10 11 m s to about 2 10 8 m s on the other hand the matrix porosity for neglected cavern and fissure porosities when combined with tracer ages or mean travel times is shown to yield proper values of the hydraulic conductivity k by applying the following formula k matrix porosity mean travel distance mean hydraulic gradient mean tracer age confirming earlier findings of the authors this equation is shown to be of great practical importance because matrix porosity is easily measured in the laboratory on rock samples whereas cavern and fracture porosities usually remain unmeasurable

deformational episodes recorded in the skagit gneiss complex north cascades washington usa abstract the crystalline core of the north cascades is part of a thick 55 km 96 45 ma continental magmatic arc the highest grade part of the arc is the skagit gneiss complex that includes partially migmatitic amphibolite facies orthogneiss layered biotite gneiss and paragneiss the typically nw striking foliation and gently se plunging lineation formed mostly between 69 and 51 ma in the study area to the north four fold generations are recorded some of which formed from 51 to 46 ma the upright kilometer scale folds in the study area are similar to eocene folds in the southern part of the skagit gneiss complex and implies at least an abbreviated interval of regional shortening during an extended period of overall transtension latest ductile deformation is marked by strong subhorizontal constrictional fabrics in granodiorite which intrudes all other major units and structures at 46 45 ma microstructures record relatively low temperature 300 400 c and medium to high temperature 450 c ductile deformation which are focused in kilometer scale domains orientation sequence and timing of deformation are similar in the northern and southern portions of the skagit gneiss complex but structures differ in the central portion that apparently do not record the brief interval of shortening

cretaceous crustal section through the proposed insular intermontane suture north cascades washington the north cascades of washington consist of rocks that were deformed and recrystallized during a middle cretaceous orogeny that was driven by the collision of the insular and intermontane superterranes we reconstruct a composite vertical crustal section through the orogen on the basis of geobarometric data from the skagit gneiss and on stratigraphic and structural data from supracrustal rocks exposed east of the skagit gneiss we propose that at the end of the orogeny the upper 30 km of crust consisted of skagit gneiss overlain by two structural couplets each composed of methow basin strata underlain by hozameen terrane rocks we suggest that the insular intermontane suture lies between the skagit gneiss and the overlying hozameen terrane rocks

metamorphism and deformation at different structural levels in a strike slip fault zone ross lake fault north cascades usa continental crust is displaced in strike slip fault zones through lateral and vertical movement that together drive burial and exhumation pressure temperature deformation p t d histories of orogenic crust exhumed in transcurrent zones record the mechanisms and conditions of these processes the skagit gneiss complex a migmatitic unit of the north cascades washington usa was metamorphosed at depths of 25 30 km in a continental arc under contraction and is bounded on its eastern side by the long lived transcurrent ross lake fault zone rlfz the p t d conditions recorded by rocks on either side of the rlfz vary along the length of the fault zone but most typically the fault separates high grade gneiss and plutons from lower grade rocks the ruby mt elijah ridge area at the eastern margin of the skagit gneiss exposes tectonic contacts between gneiss and overlying rocks the latter rocks including slivers of methow basin deposits are metamorphosed and record higher grade metamorphism than in correlative rocks along strike along the rlfz in this area the skagit gneiss and overlying units all yield maximum p t conditions of 8 10 kbar at 650 c indicating that slices of basin rocks were buried to similar mid crustal depths as the gneiss after exhumation of fault zone rocks to 15 km depth intrusion of granitoid plutons drove contact metamorphism resulting in texturally late andalusite cordierite in garnet schist in the elijah ridge area of the rlfz an overlapping step over or series of step overs that evolved through time may have facilitated burial and exhumation of a deep slice of the methow basin indicating that strike slip faults can have major vertical displacement tens of kilometres that is significant during the crustal thickening and exhumation stages of orogeny

spatial and temporal relations between early tertiary shortening and extension in nw washington based on geology of the pipestone canyon formation and surrounding rocks detailed mapping of the deformed paleocene pipestone canyon formation and surrounding cretaceous rocks in nw washington suggests that uplift erosion and unroofing of adjacent rocks was influenced by shortening at high angle to the continental margin during mid cretaceous circa 88 110 ma and early tertiary 47 65 ma time although significant shortening is mid cretaceous in age additional shortening expressed as reverse faults and major folds is early tertiary in the map area and regions to the west and northwest the skagit methow western okanogan area the shortening is essentially unmodified by extensional deformation whereas in regions east and northeast of the map area the omineca and eastern okanogan regions widespread eocene extension has obscured the shortening and caused additional unroofing as well the conglomeratic pipestone canyon formation lies unconformably on intruded early cretaceous rocks of the lower methow sequence approximately 3 5 km of mid cretaceous methow sequence strata are missing at the unconformity yet are present 15 km to the west and northwest these observations indicate late cretaceous erosion and unroofing in the southeastern methow area prior to deposition of the pipestone canyon formation furthermore conglomerate clasts in the pipestone canyon formation record sources resulting from relative uplift of the crystalline okanogan complex east of the basin and slightly later from relative uplift of the volcano sedimentary methow sequence and structurally underlying migmatitic skagit complex west to northwest of the basin following deposition which ended sometime between 55 and 65 ma the pipestone canyon formation and underlying methow sequence were tightly folded and faulted and juxtaposed with the okanogan complex by reverse faulting the map pattern of these folds and faults suggests ene wsw shortening and concomitant uplift crosscutting relations north of the map area constrain this deformation to be pre 47 ma similarity of pipestone canyon fold geometry to folds elsewhere in the methow and skagit areas supports the interpretation that a significant fold belt of circa 47 65 ma age developed in these areas and overprinted the mid cretaceous folding and thrusting regional data suggest the circa 47 65 ma folding formed a synclinorium in the methow area and an anticlinorium in the skagit area roughly concurrent with cooling ages for deep 8 9 kbar skagit rocks for the skagit methow western okanogan region as a whole the 47 65 ma shortening and unroofing were accompanied by uncertain amounts of fold belt parallel strike slip faulting timing estimates for shortening in the skagit methow western okanogan area are generally older but overlap with those established for extension farther east and northeast in the okanogan complex and omineca belt supporting interpretations that the belt of extension began to develop during or very soon after regional shortening existing thermal rheological models of extension immediately after shortening point to the need for heat sources other than mantle conduction and crustal radioactivity to facilitate the extension apparently the skagit methow fold belt failed to extend because it lacked the necessary heat

tectono stratigraphic terranes and the metamorphic history of the northeastern part of the crystalline core of the north cascades evidence from the twisp valley schist the twisp valley schist tvs is important for both the correlation of terranes in the cascades crystalline core and for the determination of the metamorphic pressure temperature time history of the northeastern part of the core the tvs is a chaotically mixed unit of mainly siliceous schist metachert with significant amounts of metabasite calc silicate rock and marble and minor ultramafite and metapsammite geochemical analyses of metabasites indicate that the tvs contains both ocean island basalts oib and mid ocean ridge basalts morb the tvs is lithologically similar to the napeequa unit of the chelan mountains terrane in the cascades core and is broadly correlative with units outside of the core including the mississippian jurassic bridge river hozameen terrane of the eastern coast belt and coeval oib bearing terranes in the northwest cascades thrust system much of the northeastern cascades core thus consists of oceanic rocks that probably originally lay between the insular and the inter