triassic bedded cherts in central japan are not pelagic although the origin of bedded radiolarian cherts in orogenic belts has been widely debated1 15 their geochemistry is still poorly understood triassic bedded radiolarian cherts occur extensively in the japanese islands and are generally not associated with ophiolitic rocks but rather with clastic rocks we present here chemical data on the triassic bedded cherts of kamiaso in central japan the relationship of sio2 with al2o3 tio2 and zr shows that the bedded cherts have been formed by a simple mixing of biogenic silica derived from radiolarians and sponge spicules with lithogenic materials the ratios of several elements relative to tio2 strongly suggest that the shale partings and lithogenic portions of the cherts are consanguineous sedimentary structures as well as the geochemical evidence suggest that most kamiaso cherts are turbidity current deposits our geochemical and geological data compared with those of recent marine sediments from various environments demonstrate that the triassic cherts and associated shale partings are not deep pelagic in origin but formed in an offshore or marginal sea environment

assessment of soil moisture movement in nuclear subsidence craters abstract this study was undertaken to investigate the potential ground water recharge resulting from a nuclear subsidence crater on the nevada test site results from two boreholes one completed in the subsidence crater bottom and the other completed in an adjacent undisturbed area suggest that deep infiltration of periodically ponded runoff water at the crater bottom is occurring whereas little or no deep infiltration was evident in the adjacent undisturbed area specialized drilling coring and borehole logging revealed high water contents and a unit hydraulic gradient downward beneath the subsidence crater traditional soil physics analysis via darcy s law and core samples suggested a wide range of downward fluid velocities and fluxes beneath the crater in contrast soil water tritium concentrations combined with several mixing models significantly reduced the range of estimated fluxes based upon these models it is suggested that the vertical flux beneath the crater is on the order of 0 6m year 1 it is postulated that the surface topography combined with the coarse textured soils beneath the crater allows for the deep infiltration of ephemerally ponded water at the bottom in the adjacent undisturbed and topographically flat lying site significant ponding does not occur and evaporation and transpiration processes recycle much if not all of the precipitation falling on the surface

comparison of ground water flow model particle tracking results and isotopic data in the mojave river ground water basin southern california usa abstract flow path and time of travel results for the mojave river ground water basin southern california calculated using the ground water flow model modflow and particle tracking model modpath were similar to flow path and time of travel interpretations derived from delta deuterium and carbon 14 data model and isotopic data both show short flow paths and young ground water ages throughout the floodplain aquifer along most the mojave river longer flow paths and older ground water ages as great as 10 000 years before present were measured and simulated in the floodplain aquifer near the mojave valley model and isotopic data also show movement of water between the floodplain and regional aquifer and subsequent discharge of water from the river to dry lakes in some areas it was not possible to simulate the isotopic composition of ground water in the regional aquifer away from the front of the san gabriel and san bernardino mountains because recharge in these areas does not occur under the present day climatic conditions used for calibration of the model

direct measurements of floodwater infiltration into shallow alluvial aquifers the relationship between floodwater infiltration and groundwater recharge of a shallow alluvial aquifer in a hyper arid desert was studied in the arava valley israel the study implemented an experimental system that simultaneously monitors all three hydrological domains controlling the recharge process 1 floodwater stages on land surface 2 water content variations in the deep vadose zone and 3 groundwater response to the infiltration this experimental system makes use of a new technique for installing flexible time domain reflectometry probes for continuous monitoring of the vadose zone moisture profiles water infiltration was monitored in controlled infiltration experiments and during a natural flood the monitoring setup allowed real time tracking of the wetting front propagation velocities and assessment of water fluxes through the vadose zone the results revealed a complex infiltration process that includes matrix and preferential flow together with lateral flow

permo carboniferous magmatism of the northeast german basin abstract variscan continent continent collision in central europe was followed by a period of syn to late tectonic magmatism involving the extrusion of large volumes of permosilesian age volcanic rocks particularly in the northeast german basin the volcanic suite up to ca 2000 m thick comprises rhyolites acid and basic andesites and tholeiitic and alkali basalts tectono geochemical analysis in conjunction with volume calculations and petrography reveals changes in volcanic activity over time a total of five eruptive stages are recognised beginning in the stephanian and extending up into the upper rotliegend permian these include the stephanian late carboniferous andesite pre ignimbrite stage i lower rotliegend permian age explosive ignimbrite stage ii post ignimbrite stage iii late rhyolite stage iv and upper rotliegend permian age late basalt stage v in addition several volcanic centres including at least two large caldera like structures are recognised the total calculated volume for the northeast german basin volcanics is ca 48 000 km3 comprising rhyolitic rocks and ignimbrites ca 70 andesitic rocks ca 26 and basalts with cogenetic dolerites ca 4 regional variations in composition and geochemistry are related to diverse crust mantle regimes which correlate with differing positions relative to the heterogeneous basement of the variscan foredeep or within the rhenohercynian orogenic zone the crustal thickening and increasing generation depth of the mafic magmas from north to south may reflect the presence of a pre existing subduction influenced basaltic magma source

differences in geochemical features between permian and triassic cherts from the southern chichibu terrane southwest japan ree abundances major element compositions and sr isotopic ratios abstract ree abundances sr isotopic data and major element compositions are reported for the permian and triassic cherts from the kuma and saiki areas in the southern chichibu sambosan terrane the outer zone of southwest japan in order to elucidate the nature of sources depositional environment and any changes that occurred from the permian to the triassic a higher contribution of detrital components in the triassic sambosan cherts than in the permian ones is suggested by the ce anomaly seen in the ree pattern mno tio 2 and al 2 o 3 al 2 o 3 fe 2 o 3 ratios and initial 87 sr 86 sr ratio of these cherts small negative ce anomalies ce ce 0 75 0 95 are observed in the permian cherts from both kuma and saiki areas in contrast to small positive ce anomalies ce ce 1 1 1 3 for the triassic cherts from both areas it should be noted that the sambosan cherts show neither large negative ce anomalies ce ce 0 2 0 5 commonly observed in deep sea cherts nor large variation in ce anomalies ce ce 0 3 1 5 observed for cherts from the franciscan terrane of california al 2 o 3 al 2 o 3 fe 2 o 3 ratios are 0 5 0 8 for all sambosan cherts mno tio 2 ratios are larger than 0 5 for most of the permian kuma cherts and the early permian saiki cherts while the ratios are smaller than 0 5 for the triassic kuma cherts and late permian and triassic cherts from the saiki area initial 87 sr 86 sr ratios for the permian saiki cherts are 0 706 0 707 and are slightly lower than those for the triassic kuma cherts 0 707 0 709 these 87 sr 86 sr ratios for the permian and triassic sambosan cherts are close to the coeval marine 87 sr 86 sr ratios of burke et al 1982 and are clearly lower than that for cherts from the mino terrane 0 713 inner zone of southwest japan shibata and mizutani 1982 our geochemical and isotopic data of the sambosan cherts suggest a change from ocean basin floor deposition for the permian to hemipelagic for the triassic cherts however geochemical features showing deposition on a typical deep ocean floor are not observed even for the permian cherts some difference in depositional location between the kuma and saiki cherts in the sambosan terrane is also implied from the difference in temporal variation of geochemical features between these two cherts e g increase of ree content with age for the kuma cherts in contrast to a decrease for the saiki cherts in addition it is suggested that the permian and triassic sambosan cherts were deposited in a more open ocean environment than the triassic cherts in the mino terrane this study demonstrates that geochemical and isotopic data could be used to distinguish differences of depositional environment of cherts and those data from the permian to the triassic cherts suggest increasing proximity to land in their depositional environments

products and timing of diagenetic processes in upper rotliegend sandstones from bebertal north german basin parchim formation flechtingen high germany aeolian fluvial upper rotliegend sandstones from bebertal outcrops flechtingen high north germany are an analogue for deeply buried permian gas reservoir sandstones of the north german basin ngb we present a paragenetic sequence as well as thermochronological constraints to reconstruct the diagenetic evolution and to identify periods of enhanced mesodiagenetic fluid rock reactions in sandstones from the southern flank of the ngb bebertal sandstones show comparatively high concentrations of mesodiagenetically formed k feldspar but low concentrations of illite cements illite rich grain rims were found to occur preferentially directly below sedimentary bounding surfaces i e aeolian superimposition surfaces and indicate the lowest intergranular volume illite grain rims also indicate sandstone sections with low quartz and feldspar cement concentrations but high loss of intergranular volume due to compaction 40ar 39ar age determination of pronounced k feldspar grain overgrowths and replacements of detrital grains indicates two generations an early triassic and a late jurassic generation the latter age range is similar to published diagenetic illite ages from buried rotliegend reservoir sandstones the first generation suggests an early intense mesodiagenetic fluid flow with remarkably high k activity synchronous with fast burial of proximal initial graben sediments on the southern flank of the ngb accordingly zircon fission track data indicate that the strata already reached the zircon partial annealing zone of approximately 200 c during early mesodiagenesis zircon u th he ages 92 12 ma as well as apatite fission track ages 71 75 ma indicate the termination of mesodiagenetic processes caused by rapid exhumation of the flechtingen high during late cretaceous basin inversion

playa lake basins on the southern high plains of texas and new mexico part i hydrologic geomorphic and geologic evidence for their development playa lake basins of the southern high plains texas and new mexico may originate wherever water periodically can collect in a surficial depression they expand however by hydrologic and geomorphic processes including 1 dissolution of lithologic carbonates by infiltrating water 2 transport downward of fine grained clastic and organic material by the infiltrating ground water leading to continuing processes of oxidation and carbonate dissolution in the subsurface and 3 eolian removal of clastic material from the floor of playa lakes which at some sites appears to have deepened playa depressions evidence for largely hydrologic processes of playa basin development on the southern high plains includes 1 a geographic occurrence restricted to relatively flat areas of the high plains surface that have poorly developed fluvial drainage and which are underlain by generally unsaturated clastic and calcrete beds 2 a tendency to occur where water collects and infiltrates as along ephemeral streams and lineations suggestive of fracture systems and 3 hydrologic geochemical petrographic and bore hole data which suggest that recharge to the high plains aquifer is principally from playa lakes that various geochemical changes including carbonate dissolution and enhancement of secondary porosity occur as water moves downward through the unsaturated zone beneath playa lakes and that calcrete beds often are missing or significantly dissolved beneath playa floors

well documented travel history of mesozoic pelagic chert in japan from remote ocean to subduction zone the mino tanba belt in southwest japan a segment of the cordilleran type orogenic chain of jurassic east asia is composed mainly of a middle upper jurassic subduction accretion complex in which triassic and lower jurassic bedded radiolarian cherts occur as large allochthonous units structurally interlayered with middle upper jurassic clastic rocks high resolution microfossil conodont and radiolaria research has identified very low average sedimentation rates of about 0 5 g cm 1000 yr in the chert units similar to those of modern pelagic sediments accumulated in open ocean environments judging from the low average sedimentation rate high purity of biogenic silica long duration of continuous deposition 50 m y and wide along strike extent 1000 km the bedded radiolarian cherts in the mino tanba belt are best understood as ancient pelagic sediments that accumulated in open ocean environments accordingly the alleged origin in smaller marginal basins is untenable upward lithologic change from bedded chert to overlying siliceous mudstone in the uppermost portion of chert sequences suggests the gradual landward approach of the oceanic plate toward a trench the tectonic interlayering of these cherts and coarse grained terrigenous elastics is a secondary feature that was added through duplexing underplating in the subduction zone on the basis of the primary stratigraphy and field occurrence of triassic bedded chert in the mino tanba belt newly proposed are an idealized oceanic plate stratigraphy and a generalized travel history of a cordilleran type bedded chert from its birth at a mid oceanic ridge to its demise at a subduction zone

twin lake tracer tests setting methodology and hydraulic conductivity distribution following evaluation of three potential sites a fluvial sand aquifer with high 0 7 1 6 m d 1 linear average groundwater flow velocities was instrumented with a fully penetrating injection well and 82 monitoring installations over a 40 m flow path length two natural gradient tracer migration experiments have employed pulse injections of a nonreactive radioisotope 131i in a study of hydraulic conductivity structure and dispersive characteristics of the flow system the use of a gamma emitting radionuclide in these experiments allowed measurement of tracer distribution by scanning fully penetrating boreholes with a scintillation detector this technique provided many advantages in data collection over conventional tracers including unprecedented resolution of the vertical distribution of tracer measurements without pumping and the attendant concerns for flow system perturbation and minimal manpower for sample analysis tracer breakthroughs at monitors along the axis of flow revealed the presence of heterogeneities in aquifer hydraulic conductivity at two scales over the 40 m path length six regions with hydraulic conductivities substantially different from adjacent strata were identified thicknesses of these regions varied from 0 2 to more than 3 m their lateral extents in the direction of groundwater flow ranged from 15 m to more than 40 m smaller strata with an average thickness of 0 34 m and lengths of less than 10 m were detected within all six of the hydraulic conductivity regions but there was no evidence of increases in local dispersivity with increased transport distance as a result of these variations the six hydraulic conductivity regions do however have measurable effects on whole aquifer dispersion stratification characteristics of the tested aquifer believed to have been deposited in a sandy braided river are consistent with those observed in similar modern environments estimation of the magnitude and spatial structure of hydraulic conductivity variations in aquifers of concern would be greatly aided by studies of the stratification characteristics in well exposed modern or lithified sedimentary analogues

diagenesis and fluid mobilisation during the evolution of the north german basin evidence from fluid inclusion and sulphur isotope analysis abstract samples of diagenetic and hydrothermal minerals from drillcores along the dekorp 9601 seismic traverse in the north german basin were investigated for their fluid inclusion and sulphur isotope composition to reconstruct the thermal and chemical evolution of fluid systems during basin evolution the stages of basin subsidence and subsequent inversion are marked by fluid systems of distinct composition the basinwide zechstein evaporite units formed an aquiclude disconnecting convecting fluids in the underlying rotliegend volcanics from the overlying units 34 s ratios of sulphides suggest a sedimentary sulphur source 34 s ratios of diagenetic and hydrothermal sulphates indicate that sulphur was derived partly from rotliegend volcanic units and partly from the evaporitic zechstein

effective unsaturated hydraulic conductivity of layered sands accurate estimates of field scale hydraulic conductivities of unsaturated heterogeneous soils are very difficult to obtain in the present study various approaches to determining effective conductivity values for heterogeneous sands are compared with laboratory measurements the unsaturated hydraulic conductivity k of two homogeneous sands and one layered sand composed of the two homogeneous sands was measured using the steady state flux control method the averaged k curves of the two homogeneous sands using a direct averaging approach were compared with the measured layered sand k data the result shows that the geometric mean of hydraulic conductivity suction curves of the coarse and medium sands approximates the measured hydraulic conductivity suction curve of the layered sand the observed suction variance and effective hydraulic conductivity were compared with expressions developed from a stochastic theory the results support the stochastic approach

fluid inclusion evidence for low temperature thermochemical sulfate reduction tsr of dry coal gas in upper permian carbonate reservoirs zechstein ca2 in the north german basin abstract upper permian zechstein carbonate ca2 gas reservoirs in the southern part of the pompeckj block in the north german basin locally contain up to 36 vol hydrogen sulfide h2s produced by thermochemical sulfate reduction tsr tsr was triggered by migration of dry to extremely dry coal gas from upper carboniferous into the zechstein carbonate reservoirs methane reacted with dissolved sulfate at temperatures of the results of this study decipher three major stages of gas migration in the pompeckj block stage i commenced in the late triassic during burial when zechstein ca2 reservoirs were charged with dry ch4 co2 n2 gas sourced from mature upper carboniferous coals burial continued through the jurassic and caused alteration of ca2 reservoir gas by sulfate reduction reactions due to increasing temperatures entrapment of ch4 h2s co2 n2 gases in fluid inclusions hosted in cements and fracture filling minerals occurred at temperatures between 100 and 152 c and was related to stage ii uplift in the early lower cretaceous in the late cretaceous stage iii deep burial of the pompeckj block led to charge of the zechstein ca2 carbonate reservoirs with upper carboniferous derived ch4 co2 n2 c2 coal gas and or dilution of existing reservoir gas at temperatures of 144 167 c highly variable 13cch4 values from 18 7 to 8 7 and very negative 13cco2 values 22 4 to 18 9 of h2s rich fluid inclusion gases as well as negative 13c values 10 4 to 4 6 of host calcites reveal compelling evidence for participation of methane in tsr fluid inclusions imply that ch4 dominated tsr proceeded at tmin of 135 c in the presence of catalyzers such as h2s and dissolved mg2 this study demonstrates that fluid inclusions serve as an excellent and accurate tool for tracing h2s concentrations in hydrocarbon gases through time and space which is not possible using the present day compositions of natural reservoir gases it also contributes to the understanding of carbonate reservoir hosted hydrocarbon bearing fluid systems and processes that significantly control the quality of reservoir gases

chemical and sr isotopic variations during diagenesis of miocene siliceous sediments of the monterey formation california the monterey formation of california preserves miocene siliceous sediments at progressive generally with depth diagenetic stages diatomite opal a ct chert opai ct quartz chert for initially clay poor sediments and diatomaceous shale ct porcelanite porous opal ct quartz porcelanite for sediments that were initially clay rich the chemistry of most diatomite is controlled by three primary phases biogenic silica carbonate and detrital clay and several subsidiary phases organic material apatite pyrite and detrital minerals including quartz and plagioclase the elemental abundances of the clay poor diagenetic sequence decrease sharply with advancing diagenetic state for those elements controlled by clay al ti k rb cs fe some group b metals carbonate ca mg sr ba apatite p ca sr ba v and organics v ni while silica shows a congruent increase these first order variations reflect the initial compositions of the siliceous sediments modified by the addition of silica the removal of carbonate and apatite and the migration of petroleum during silica diagenesis anomalous abundances of mn ni cr mo and some other group b metals are associated with trapped refractory organic material and suggest that petroleum catagenesis and migration occurred during silica diagenesis migration may have been facilitated by the release of bound water during silica dehydration reactions second order variations in k rb k cs rb sr 87 sr 86 sr with advancing diagenetic state suggest ion exchange and ion expulsion by reaction of detrital phases with pore fluids diagenetic processes partially equilibrated but did not homogenize depositional 87 rb 86 sr 87 sr 86 sr mixing lines generated by detrital clays and authigenic carbonate and silica in siliceous sediments from the santa maria region however similar mixing lines in diatomites from the santa lucia area are reset to nearly horizontal slopes in associated ct porcelanites the degree of equilibration may be a function of the rate of formation of relatively impermeable quartz chert which isolated the siliceous system from further interaction with pore fluids the rapid formation of quartz chert in the santa maria region is believed to have prevented isotopic homogenization processes from reaching completion initial chemistry of the siliceous systems controlled the rates and pathways of silica diagenesis silica diagenesis in turn altered the chemistry of the siliceous sediment

the role of the kupferschiefer in the formation of hydrothermal base metal mineralization in the spessart ore district germany insight from detailed sulfur isotope studies the spessart district sw germany located at the southwestern margin of the permian kupferschiefer basin in central europe hosts abundant stratabound and structurally controlled base metal mineralization the mineralization styles identified are 1 stratabound cu pb zn ag ores in zechstein sedimentary rocks 2 structurally controlled cu as ag ores in zechstein sedimentary rocks 3 crosscutting co ni bi as and cu fe as veins 4 stratabound metasomatic fe mn carbonate ores in zechstein dolomite 5 barren barite veins and 6 fe mn as veins in permian rhyolites building on previous work that involved mineralogical textural and chemical characterization of the major mineralization types we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser ablation multi collector inductively coupled plasma mass spectrometry techniques the 34s values of sulfide minerals from the different ore types are consistently negative and highly variable in the range between 44 5 and 3 9 whereas the 34s values of barite are all positive in the range between 4 7 and 18 9 remarkably stratabound and structurally controlled mineralization in zechstein sedimentary rocks has the least negative 34s values whereas vein type deposits have consistently more negative 34s values the observed pattern of sulfide 34s values can be best interpreted in terms of fluid mixing at the basement cover interface hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post variscan sedimentary cover these groundwaters had interacted with the zechstein sedimentary rocks resulting in fluids characterized by elevated concentrations of reduced sulfur with negative 34s values and alkaline ph repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative 34s values

asian continental nature of87sr 86sr ratios in north central pacific sediments strontium isotopic compositions were determined for silicate detritus in 152 deep sea and continental shelf surface sediment samples from the pacific ocean to trace their provenance the major characteristics of the spatial variation of the sr isotopes and the interpretation of this variation may be summarized as follows 1 sediments in the pacific have a lower average87sr 86sr ratio 0 7112 with a narrower range 0 703 0 724 than in the atlantic 0 7166 0 704 0 743 many western pacific volcanoes together with young continental crust supply material with low87sr 86sr ratios to the pacific in contrast to the large old cratonic crust that supplies material with high sr ratio to the atlantic 2 the87sr 86sr ratio is high in the north central pacific 0 711 0 719 the izu ogasawara and mariana arcs supply low87sr 86sr material to the western pacific but farther to east the abundant supply of loess carried by middle latitude westerlies from the asian continent 87sr 86sr ca 0 720 dominates the north central pacific

thermal conductivity and radiogenic heat production of sedimentary and magmatic rocks in the northeast german basin thermal rock properties were determined for the northeast german basin a subbasin of the southern permian basin in europe the new thermal data provide new aspects for the determination of heat flow and for hydrocarbon and geothermal resource evaluation in the basin thermal conductivity was measured on drill core samples using the optical scanning method values for permian and pre permian clastic rocks are variable 2 3 4 8 w m k because of different depositional environments compaction and cementation reflected in lithology permian carboniferous igneous rocks show lowest thermal conductivity in basalts 2 2 w m k and highest 3 1 w m k in granitoids anisotropy of thermal conductivity in all rocks is low formation thermal conductivity was determined by upscaling the values determined for single lithotypes radiogenic heat production was determined on drill cores for the upper paleozoic sediments and igneous rocks for the younger formations without sample control a well log approach was used the heat production of sedimentary rocks is lowest 0 4 w m3 in the permian zechstein salt and anhydrite and highest 2 1 w m3 in the permian rotliegende clastic rocks heat production of the permian carboniferous rhyolites and granitoids is on the order of 2 6 3 8 w m3 and heat production of andesites and basaltoids is on the order of 0 9 1 9 and 0 1 0 7 w m3 respectively the contribution to surface heat flow by these up to 2 km 1 2 mi thick igneous complexes amounts to 7 mw m2 at a maximum on the same order is the total heat budget provided by the supra permian sedimentary succession in the basin

evolution of the northeast german basin inferences from a 3d structural model and subsidence analysis abstract a 3d structural model of the northeast german basin was evaluated with special emphasis on its evolution as an intracontinental depression the study includes investigations on subsidence history and structural setting of the basin thickness evolution and calculated tectonic subsidence volumes of permian to quaternary sediments in the northeast german basin indicate that the subsidence history was related to five stages of basin evolution which differ in their subsidence mechanisms for the initial rift phase in the late carboniferous to early permian a dominant thermal event and subordinate horizontal stresses were indicated by thickness variation evolution and by structural evidence the main part of basin subsidence occurred in a nw se oriented basin in the subsequent phase of thermal relaxation with maximum subsidence from early permian rotliegend to middle triassic muschelkalk from middle triassic the thermal subsidence pattern was superposed by further tectonic events in the middle triassic regional extension led to a reconfiguration of the southern part of the basin where new nne ssw trending troughs rheinsberg and gifhorn troughs developed in the jurassic the northwestern part of the basin was uplifted while in the south the keuper subsiding areas continued to sink and nw se trending depressions related to salt margins became important differentiation continued into cretaceous times when regional compression caused uplift of the southeastern part of the basin and basin margins a final subsidence phase occurred in the cenozoic this was accompanied by intensive salt movement recent basin configuration reflects the superposition of structural elements resulting from different evolution stages the main structural characteristics of the basin are 1 a vertical tectonic zonation in a pre zechstein succession which lacks significant internal structures and a strongly deformed post zechstein succession which was decoupled due to the thick zechstein salt and 2 a marked asymmetry of the basin with a shallow northern slope and a steep bounding fault at the southern margin elbe fault system the northwestern part of the basin shows the structural properties of an intracratonic sag basin with persisting subsidence and with minor salt mobilisation in contrast initial structures in the southeastern part are strongly overprinted by younger tectonic events including middle triassic to jurassic extension late cretaceous inversion and late to post cretaceous salt movements tectonic elements that deform the whole sedimentary succession are restricted to the basin s southern eastern and northeastern margins where salt thickness decreases combined volumetric and backstripping investigations show that 2 3 of the total subsidence was induced by the sediment load and 1 3 was caused by tectonics the tectonic subsidence history varies laterally across the basin while tectonic subsidence curves in the northwestern part of the basin show fast subsidence during the permian and early triassic decreasing exponentially with time subsidence curves in the southeastern part indicate repeated tectonic activity however the tectonic subsidence volume created during permian to late triassic is significantly higher than the tectonic subsidence during younger phases of basin history

rare earth elements in river waters we measured rare earth element ree concentrations in river waters to characterize the suspended and dissolved river flux of the ree to the oceans the ree pattern of river suspended materials is sensitive to drainage basin geology a positive correlation is observed between la yb ratios and nd model ages for the rivers studied major rivers have light ree enriched patterns relative to the north american shale composite nasc with la yb n 1 6 2 7 river water dissolved material 0 2 m is heavy ree enriched relative to suspended material and the most pronounced negative ce anomalies occur in rivers of high ph light ree concentrations vary by approximately 3 orders of magnitude and are inversely related to ph and major cation concentrations from these data we estimate that typical major river runoff has heavy ree depleted suspended material with la yb n 1 9 we conclude that the terrigenous input to the oceans from major rivers is heavy ree depleted relative to shales from the available data average river water dissolved material appears to be heavy ree enriched with la yb n 0 4 estuarine removal processes lower the dissolved ree river flux by approximately 60 and result in a flux that is more heavy ree enriched with la yb n 0 2 calculated oceanic residence times with respect to river input range from 2300 to 21 000 years are shortest for ce and greatest for the heavy ree and la such long residence times may suggest the presence of additional sources of ree in seawater

characteristics of soil infiltration in the tarim river floodplain the ecology in the tarim river basin is influenced by inundation of its floodplain to date however there is limited information about the infiltration properties of floodplain soils that are inundated by this river the aim of this study was to investigate steady infiltration rates of these soils under four different hydraulic heads 5 10 20 and 30 cm results showed that the mean infiltration rates were generally high and ranged from 3 17 to 3 50 cm h 1 when the hydraulic head was between 5 and 30 cm the steady infiltration increased slightly as the hydraulic head increased the relationship between the hydraulic head and the infiltration rate can be described by the equation y 0 0122x 3 072 r2 0 739 where y is the steady infiltration rate and x is the hydraulic head there was no significant difference between the infiltration rates for the four different hydraulic heads the infiltration rate was highest for loamy sand followed by sandy loam and was lowest for silt soils infiltration was influenced by soil texture and crust and was low 1 cm h 1 hydraulic head of 5 cm for soils with thick crusts and high for soils without surface crusts mean of 6 09 cm h 1 hydraulic head of 5 cm the steady infiltration rate was not influenced by soil organic matter these results indicate that flood water can percolate into the floodplain soils and give an improved understanding of the factors that influence the ecological processes on the tarim river floodplains

remnants of a late triassic ocean island in the gufeng area northern tibet implications for the opening and early evolution of the bangong nujiang tethyan ocean abstract in this paper we present new major and trace element compositions of basaltic rocks in the gufeng ocean island gfoi area in the western segment of the bangong nujiang suture zone northern tibet our aim was to assess the genesis of these rocks and discuss the implications of this new dataset for the evolution of the bangong nujiang tethyan ocean an ocean island type double layer structure comprising a basaltic basement and an oceanic sedimentary cover sequence found within the gfoi provides direct evidence for the interpretation that the assemblage is a typical ocean island the basalts in the gfoi can be divided into three types named g1 g2 and g3 basalts and these basalts range in composition from morb to oib types which is typical of ocean islands the g1 basalts have morb type affinities possibly indicating the existence of morb oceanic crust under the gfoi the g2 basalts represent the early stage of formation of the gfoi and are produced by the interaction of rising oib type basaltic magma and the existing morb oceanic crust the g3 basalts are typical oib basalts and they are the products of the direct eruption of oib type basaltic magmas the g3 basalts have high la yb n 12 3 14 4 ce yb n 10 8 11 8 la sm n 2 39 2 76 and sm yb n 4 89 5 23 ratios indicating the presence of oceanic lithosphere below the gfoi with a thickness of 50 60 km geochemical analyses of the gfoi cherts show that they contain terrigenous material indicating the gfoi formed close to a continental margin norian conodont fossils within the gfoi limestones indicate the gfoi formed during the late triassic these data combined with geological evidence and a half space model of lithosphere cooling where the thickness of the oceanic lithosphere is determined from the age of the lithosphere indicate that the western segment of the bangong nujiang tethyan ocean opened initially in the late permian expanded rapidly during the early middle triassic and was a mature ocean during the late triassic

water movement through a thick unsaturated zone underlying an intermittent stream in the western mojave desert southern california usa previous studies indicated that small amounts of recharge occur as infiltration of intermittent streamflow in washes in the upper mojave river basin in the western mojave desert near victorville california these washes flow only a few days each year after large storms to reach the water table water must pass through an unsaturated zone that is more than 130 m thick results of this study done in 1994 1998 show that infiltration to depths below the root zone did not occur at control sites away from the wash at these sites volumetric water contents were as low as 0 01 and water potentials measured as the combination of solute and matric potentials using a water activity meter were as negative as 14 000 kpa water vapor movement was controlled by highly negative solute potentials associated with the accumulation of soluble salts in the unsaturated zone highly negative matric potentials above and below the zone of maximum solute accumulation result from movement of water vapor toward the highly negative solute potentials at that depth the 18o and d delta oxygen 18 and delta deuterium isotopic composition of water in coarse grained deposits plots along a rayleigh distillation line consistent with removal of water in coarse grained layers by vapor transport beneath oro grande wash water moved to depths below the root zone and presumably to the water table about 130 m below land surface underneath oro grande wash volumetric water contents were as high as 0 27 and water potentials measured as matric potential using tensiometers were between 1 8 and 50 kpa on the basis of tritium data water requires at least 180 260 years to infiltrate to the water table clay layers impede the downward movement of water seasonal changes in water vapor composition underneath the wash are consistent with the rapid infiltration of a small quantity of water to great depths and subsequent equilibration of vapor with water in the surrounding material it may be possible to supplement natural recharge from the wash with imported water recharge to the wash may be advantageous because the unsaturated zone is not as dry as most areas in the desert and concentrations of soluble salts are generally lower underneath the wash

measurement of anisotropic hydraulic conductivity in unconsolidated sands a case study from a shoreface deposit oyster virginia in this study an integrated field and laboratory method which can be used to evaluate the magnitude and distribution of anisotropic hydraulic conductivity at the scale of bedding structures in unconsolidated sediment is demonstrated undisturbed sediment cores 10 16 cm in diameter and 18 25 cm long are obtained using a split barrel core sampler two undisturbed 5 72 cm diameter 7 90 cm long subcores oriented parallel and perpendicular to the primary bedding structures are then obtained from each field core the hydraulic conductivities of the subcores are then measured with a constant head permeameter the sampling and experimental procedures are designed to minimize potential sources of error sixty four 10 16 cm cores were sampled in a coastal sand outcrop located 300 m from a subsurface injection experiment near oyster virginia four distinct lithologies were sampled in horizontal transects with a spacing of 0 5 m between core locations in addition iron oxide bands which were prevalent throughout the exposure were sampled from both ends of the outcrop the average hydraulic conductivity values are consistent with the observable geologic features grain size sorting and iron oxide banding hydraulic conductivity is greater in the parallel oriented subcore for 90 of the core pairs and mean hydraulic conductivity ratios of parallel to perpendicular oriented subcores k k for the different lithologies ranged from 1 33 to 1 57 the major control on the anisotropy in this sediment is interpreted to be preferential grain orientations resulting from depositional processes with additional influences from the prominence of the bedding structures and secondary features such as hydrous iron oxide banding

geochemical characteristics and geological significance of the bedded chert during the ordovician and silurian transition in the shizhu area chongqing south china a large amount of bedded chert widely deposited during the ordovician and silurian transition in south china in this study analyses of the petrographic characteristics the major elements and rare earth elements rees were conducted on 31 bedded chert samples obtained from the wufeng and longmaxi formations at the qiliao section in the shizhu area of the sichuan basin to determine the sedimentary environment and the origin of the bedded chert during the ordovician and silurian transition the following conclusions were obtained 1 the bedded chert in the wufeng and longmaxi formations at the qiliao section originated mainly from terrigenous input and siliceous organisms and suffered slightly influence in hydrothermal fluid 2 siliceous organisms was a key factor controlling the differences in the sio2 content of the bedded chert in the wufeng and longmaxi formations at the qiliao section and 3 the bedded chert in the wufeng and longmaxi formations deposited in a continental margin environment d

geochemistry of late permian to early triassic pelagic cherts from southwest japan implications for an oceanic redox change major trace and rare earth element abundances were determined for the southwestern japanese pelagic chert sequence from the early late permian to early early triassic to investigate a redox change in deep sea pelagic environments before and at the permo triassic boundary ptb 251 ma the sequence was primarily deposited in the deep sea of the superocean panthalassa and then was accreted to japan in the middle jurassic a remarkable lithostratigraphic change from red chert to siliceous carbonaceous claystone through gray chert is observed in this sequence constituent elements for these sedimentary rocks are essentially derived from two sources 1 an ancient seawater via biogenic mainly radiolarian hydrothermal and authigenic materials and 2 an average shale like terrigenous material the present measurement demonstrates significant stratigraphic changes of the ce cenon ter value estimated ce anomaly value of non terrigenous component recalculated by subtraction of terrigenous rees from bulk rees and the mn te sample mn te paas value excess mn component other than terrigenous one te terrigenous elements including ti al nb hf th paas post archean average australian shale in the permian chert the ce cenon ter values increase from 0 2 to 1 and the mn te sample mn te paas values decrease up section suggesting that the redox condition of deep sea open ocean changed from oxic to suboxic in an interval of approximately 10 myr the fe te sample fe te paas and mn te sample mn te paas values of carbonaceous claystone near or at the ptb are less than unity suggesting that reductive dissolution of iron and manganese occurred under an anoxic condition this supports the idea of the ptb oceanic anoxia in the superocean panthalassa the present data suggest that the anoxic condition prevailed in the deep sea pelagic regions for an extremely long period much more than 10 myr from the middle late permian to early early triassic this long term development of widespread oceanic anoxia may have been linked to the greatest mass extinction of the phanerozoic

the panthalassa a cerium rich atlantic type ocean sedimentary environments of the tamba group southwest japan abstract the oceanic sediments of the tamba group a part of the japanese paleozoic mesozoic accretionary prism were studied geochemically these oceanic sediments have various ree patterns which correspond to specific ocean floor environments the type ii suite of the tamba group contains the following changes in sedimentary environment pelagic sedimentation under the influence of hydrothermal activity or diagenetic metal accumulation negative ce anomaly pelagic sedimentation in ce poor seawater or diagenesis under less oxic conditions lree hree or mree lree hree pattern and slow pelagic sedimentation under oxic conditions where authigenic metal flux from seawater resulted in a positive ce anomaly different from the type ii suite lower pelagic sediments of the type i suite show a lree hree pattern which indicates the inflow of very fine terrigenous or volcanic materials cherts and siliceous shales with positive ce anomaly are exclusively present in the upper part of chert siliceous shale sequences in all successions of the tamba group this suggests that seawater of the panthalassa ocean was at least partially enriched in ce resembling the modern atlantic more than the modern pacific ocean the following reasons for this enrichment are considered 1 1 fluvial input from surrounding continents was substantial 2 2 reductive regeneration of ce from continental shelves was active or 3 3 ce depleted seawater did not enter from the other ocean

interoceanic variation in the rare earth major and trace element depositional chemistry of chert perspectives gained from the dsdp and odp record rare earth element ree major and trace element abundances and relative fractionations in forty nodular cherts sampled by the deep sea drilling project dsdp and ocean drilling program odp indicate that the ree composition of chert records the interplay between terrigenous sources and scavenging from the local seawater major and non ree trace element ratios indicate that the aluminosilicate fraction within the chert is similar to nasc north american shale composite with average pacific chert including 7 nasc like particles indian chert 11 nasc atlantic chert 17 nasc and southern high latitude shl chert 53 nasc using la as a proxy for ree approximations of laex the amount of la in excess of that supplied by the detrital aluminosilicate fraction indicate that pacific chert contains the greatest laex 85 of latotal and shl chert the least 38 of latotal as shown by interelement associations this laex is most likely an adsorbed component onto aluminosilicate and phosphatic phases accordingly chert from the large pacific ocean where deposition occurs relatively removed from significant terrigenous input records a depositional ree signal dominated by adsorption of dissolved rees from seawater pacific chert cece 1 and lanybn 0 8 1 resulting from adsorption of local ce depleted seawater and preferential adsorption of lrees from seawater e g lanybn 0 4 which increases the lanybn ratio recorded in chert chert from the atlantic basin a moderately sized ocean basin lined by passive margins and with more terrigenous input than the pacific records a mix of adsorptive and terrigenous ree signals with moderately negative ce anomalies and lanybn ratios intermediate to those of the pacific and those of terrigenous input chert from the shl region is dominated by the large terrigenous input on the antarctic passive margin with inherited cece 1 and inherited lanybn values of 1 2 1 4 cece does not vary with age either throughout the entire data base or within a particular basin overall cece does not correlate with p2o5 concentrations even though phosphatic phases may be an important ree carrier this and previous studies of the large scale controlling parameters of sedimentary rees across ocean basins collectively indicate that ree indices of depositional regime e g cece lanybn laex are reproducible in a variety of sediment and rock lithologies ages and ocean basins and present a coherent tool for paleoceanographic and tectonic basin reconstructions

geologic and hydrologic controls on the movement of water through a thick heterogeneous unsaturated zone underlying an intermittent stream in the western mojave desert southern california 1 a two dimensional axially symmetric unsaturated flow model was developed to test hypotheses about geologic and hydrologic controls on the movement of water through the thick heterogeneous unsaturated zone underlying oro grande wash in the mojave desert california heterogeneity within the unsaturated zone was simulated with multiple realizations of subsurface geology estimated on the basis of transition probability markov chain statistics model results show lateral spreading of water away from the wash was best approximated by realizations that include thin horizontally extensive clay layers that impede the downward movement of water there was a wide range in model responses for these realizations and the movement of water through unsaturated zones containing thin horizontally extensive clay layers may be more difficult to predict than water movement through unsaturated zones where clay layers are less extensive for realizations having less extensive clay layers the range of model responses decreased with time and model results became increasingly similar as water encountered larger volumes of material

sedimentary environments of the middle permian phosphorite chert complex from the northeastern yangtze platform china the gufeng formation a continental shelf radiolarian chert abstract radiolarian chert deposited on a continental shelf occurs in the middle permian gufeng formation on the northeastern yangtze platform china the sedimentary environments of radiolarian cherts from accretionary complexes have been well studied however there are few studies about radiolarian chert deposited on continental shelves therefore we have completed a sedimentological and geochemical study of the gufeng formation the gufeng formation is subdivided into the phosphate nodule bearing mudstone member pnmm and the siliceous rock member srm in ascending order the basal pnmm consists of glauconite bearing mudstone which indicates deposition under aerobic shallow marine conditions whereas the upper pnmm is composed of mudstone including abundant phosphate nodules suggesting deposition near the outer shelf in suboxic conditions the srm consists mainly of alternating beds of black chert mudstone and siliceous mudstone with minor tuffaceous mudstone and porous chert beds the black chert contains abundant radiolarians sponge spicules and organic matter framboidal pyrite occurs in the black chert porous chert in the srm includes abundant rhombohedral cavities which are dolomite moulds surrounded by quartz suggesting dolomitization before silicification during early diagenesis the gufeng chert is characterized by high si mo ni cu and zn contents and extremely low mn content the gufeng chert has high normal paraffin concentrations with petroleum like markers these geochemical features suggest that the gufeng chert was deposited under sulfate reducing conditions and is not hydrothermal but rather biogenic in origin the sedimentological and geochemical data suggest that the gufeng formation was deposited mainly on the outer shelf in suboxic anoxic conditions caused by organic matter produced during upwelling the upwelling probably led to high radiolarian productivity abundant silica and organic matter were deposited in the gufeng basin compared with chert from other sites the gufeng chert shows many similarities with chert from platformal basins but not with chert from accretionary complexes especially with respect to age rock type stratigraphy and geochemical features the chert of the gufeng formation is similar to that of the phosphoria formation in the western u s a which is a world class phosphorite giant these similarities suggest that upwelling occurred around the eastern margins of panthalassa and the paleotethys concurrently during the middle permian in general shelf type radiolarian chert represented by the gufeng chert usually shows some of the following features dark color lack of rhythmical bedding association with phosphorite platformal limestone felsic tuff abundant organic matter and sulfides shelf type radiolarian chert is deposited in a poorly aerated restricted basin or in an oxygen minimum zone

rb sr and sm nd systematics of cherts and other siliceous deposits we have analyzed a suite of marine and lacustrine cherts to determine the concentration of rb sr sm and nd and the isotopic composition of sr and nd the samples ranged from pliocene to silurian in age and included nodular cherts in carbonates as well as bedded cherts massive samples were leached in acid to remove carbonate and both the leach and residue analyzed the residues contained 0 1 to 17 ppm rb and 0 5 to 20 ppm sr all samples have high rb sr ratios 0 1 to 0 8 and thus show enrichment of rb relative to sr of 6 to 60 times that of seawater the rb and sr in pegmatitic quartz are much lower by factors of 10 to 10 3 although these also may have high rb sr the site of rb and sr in the cherts was not established but appears to be correlated with al content the high rb sr ratios permit the use of cherts for dating in favorable circumstances the nd contents range from 9 to 1000 ppb with sm nd 0 16 to 0 19 typical of continental sources the initial 87 sr 86 sr ratio for a pacific deep sea chert is equal to that of associated carbonates and hence reflects the seawater environment in shelf and marginal basin environments the initial 87 sr 86 sr ratios of chert are distinctly more radiogenic than seawater this is most obvious where a substantial clay component is present but is observed even in samples with al 2o 3 contents less than 0 1 these results show the rb sr system in chert to be rather isolated from the associated carbonate with very little sr exchange this separate behavior appears to persist through both early and late recrystallization stages these data suggest that in many cases cherts are formed by dissolved sio 2 nucleating on clay like material which preserves the isotopic characteristics of the detrital source the detrital component required is less than 1 of the total chert in some cases it is possible that the cherts were formed from silica saturated waters from a nonmarine source possibly in coastal environments or during uplift these waters contained radiogenic sr in solution that was not exchanged with the carbonate matrix this latter mechanism is also indicated by oxygen isotopic studies knauth and epstein 1976 kolodny and epstein 1976 the nd isotopic signature of the deep sea samples reflects the seawater composition in agreement with the initial 87 sr 86 sr data on the same samples samples with excesses of 87 sr relative to seawater show low nd both sets of data thus indicating inheritance of an old detrital component the results demonstrate that the rb sr and sm nd systems may be used in elucidating the origin and evolution of cherts and that the rb sr system may be used for dating if consideration is given to the initial sr composition and to diagenetic changes this opens up numerous possibilities for sedimentological geochemical studies

stable carbon isotopic ratios of ch4 co2 bearing fluid inclusions in fracture fill mineralization from the lower saxony basin germany a tool for tracing gas sources and maturity abstract the stable carbon isotopic ratios 13 c of methane ch 4 and carbon dioxide co 2 of gas rich fluid inclusions hosted in fracture fill mineralization from the southern part of the lower saxony basin germany have been measured online using a crushing device interfaced to an isotopic ratio mass spectrometer irms the data reveal that ch 4 trapped in inclusions seems to be derived from different source rocks with different organic matter types the 13 c values of ch 4 in inclusions in quartz hosted by carboniferous rocks range between 25 and 19 suggesting high maturity coals as the source of methane methane in fluid inclusions in minerals hosted by mesozoic strata has more negative carbon isotope ratios 45 to 31 and appears to represent primary cracking products from type ii kerogens i e marine shales there is a positive correlation between increasing homogenization temperatures of aqueous fluid inclusions and less negative 13 c ch 4 values of in co genetic gas inclusions probably indicating different mtaturity of the potential source rocks at the time the fluids were released the co 2 isotopic composition of ch 4 co 2 bearing inclusions shows slight negative or even positive 13 c values indicating an inorganic source e g water rock interaction and dissolution of detrital marine calcite for co 2 in inclusions we conclude that the 13 c isotopic ratios of ch 4 co 2 bearing fluid inclusions can be used to trace migration pathways sources of gases and alteration processes furthermore the 13 c values of methane can be used to estimate the maturity of the rocks from which it was sourced results presented here are further supported by organic geochemical analysis of surface bitumens which coexist with the gas inclusion rich fracture fill mineralization and confirm the isotopic interpretations with respect to fluid source type and maturity

a new method for the determination of ceiii ceiv ratios in geological materials application for weathering sedimentary and diagenetic processes abstract relative abundances of rare earth elements ree in geological materials are used widely to investigate diverse geochemical issues such as the origins of igneous rocks or the degree of stratification of water columns in oceans one of the ree cerium ce can exist in either trivalent or tetravalent forms depending on the redox condition thus knowledge of the oxidation state of ce in rocks and minerals could potentially be used to constrain the redox states of past and present geological environments however the use of ce for this purpose has been hampered by an inability to measure its oxidation state directly here we present a new method employing the x ray absorption near edge structure for making such determinations in samples with ce concentrations as low as 15 ppm by analyzing a range of diverse geological materials granites manganese nodules and cherts we showed that the method could identify significant differences in ce speciation between materials formed under widely differing redox conditions used together with the degrees of ce anomalies measured in ree patterns this information has promise for refining our knowledge of various geochemical processes such as weathering sedimentary and diagenetic processes that control the ree behavior such a refinement should in turn improve geological interpretations based upon ree data

the influence of rock fabric and mineralogy on thermochemical sulfate reduction khuff formation abu dhabi abstract thermochemical sulfate reduction tsr is the reaction between anhydrite and petroleum fluids at elevated temperatures to produce h2s and calcite in this study of the dolomite hosted hydrocarbon gas reservoirs in the permo triassic khuff formation abu dhabi a geochemically well constrained rock gas system we demonstrate for the first time a clear influence of rock texture and mineralogy on the rate and extent of tsr reactions and thus on h2s concentration in the gas phase the controls on the rate on h2s accumulation were tsr reaction kinetics tsr became significant as temperature exceeded 140 c a critical threshold temperature for chemical reaction between aqueous sulfate and aqueous methane anhydrite dissolution rate once initiated the subsequent reaction rate was controlled by the rate of supply of aqueous sulfate to the reaction site sulfate limitation is indicated by the lack of fractionation of sulfur isotopes between sulfate and sulfide i e suggesting total reaction for each unit of sulfate that dissolves also finely crystalline anhydrite began reacting at a lower temperature than coarse crystalline anhydrite likely a result of relative surface area suggesting that anhydrite dissolution was the rate limiting step transport rates are unlikely to have been rate limiting at the earliest stage of reaction because anhydrite was replaced in situ by calcite on the very edges of anhydrite nodules and crystals transport rate later as tsr proceeded it became transport controlled as calcite growing on the surface of anhydrite crystals began to isolate them from dissolved methane tsr ceased once calcite had effectively armor plated totally isolated the remaining anhydrite finely crystalline anhydrite underwent more extensive and more rapid tsr than coarser anhydrite crystals because these had a greater ratio of surface area to volume allowing more and faster dissolution and requiring more calcite to isolate them from methane localized loss of h2s occurred in the reservoir by reaction with indigenous fe bearing clays consequently reservoirs with a relatively high siliciclastic content have less h2s than would be expected from the advanced state of anhydrite replacement by calcite in order to predict tsr related h2s concentration in hydrocarbon gases it is thus important to understand the diagenetic and textural characteristics of the reservoir as well as the thermal and petroleum emplacement history

paleomagnetism of red cherts a case study in the inuyama area central japan this study is an attempt to isolate and identify the primary magnetization in red cherts red chert samples from a middle triassic sequence in the inuyama area 35 4 n 137 0 e central japan have a multicomponent magnetization which is delineated by thermal demagnetization two of the components have high coercivity and high blocking temperatures one is carried by hematite and the other by magnetite the former was concluded to be the primary magnetization for two reasons 1 it predates intraformational folding and 2 it records geomagnetic reversals the other component which accounts for the dominant part of natural remanent magnetization was probably acquired at a time long after the deposition two paleomagnetic results were drawn from the middle triassic red chert sequence 1 the mean inclination of the samples in the sequence was 1 4 6 8 therefore the paleolatitude amounts to 0 7 3 4 in contrast to the paleolatitude expected from the paleopole of eurasian continent which is about 70 and 2 the magnetostratigraphy of this sequence indicates that two geomagnetic epochs in the middle triassic are considerably longer more than several million years than the average of those in the cenozoic

fluid rock interactions in a geothermal rotliegend permo carboniferous reservoir north german basin abstract comprehensive data on the chemical composition of reservoir rocks and geothermal brines from the geothermal well doublet gro schonebeck north german basin drilled into a rotliegend sedimentary and permo carboniferous volcanic rock reservoir were sampled over the past years they were characterized with respect to their major and minor elemental composition including various isotope ratios the study considered the impact of drilling and reservoir operations on fluid composition and aimed at determining fluid rock interactions to gain information on fluid origin and hydraulic pathways the highly saline fluids up to 265 g l tds show 18 o and d of water 2 7 5 6 and 3 1 15 respectively as well as 34 s of sulfate 3 6 5 and 87 sr 86 sr ratios 0 715 0 716 that resemble rotliegend brines from an area located around 200 km in the west the altmark halogen ratios indicated that brines developed predominantly by evaporation of meteoric water primary brine together with halite dissolution brine secondary brine indication for mixing with zechstein brine or with younger meteoric water was not found no geochemical distinction was possible between fluids deriving from different rock formations dacites or sedimentary rocks respectively this is due to the evolution of the sediments from the effusive rocks resulting in a similar mineralogical and chemical composition and due to a hydraulic connectivity between the two types of rock this connection existed probably already before reservoir stimulation as indicated by a set of faults identified in the area that could connect the rotliegend formation with both the volcanic rocks and the lower units of the zechstein additional geochemical indication for a hydraulic connectivity is given by 1 the very high heavy metal contents mainly cu and pb in fluids and scaling that derive from the volcanic rocks and were that were also found in increased amounts up at the zechstein border kupferschiefer formation 2 the 87 sr 86 sr isotope ratios of fluid samples correspond to the ratios determined for the sedimentary rocks indicating that initially the fluids developed in the sedimentary rocks and circulated later when faults structures were created by tectonic events into the volcanic rocks

late cenozoic tectonics of the northwestern san bernardino mountains southern california the late cenozoic structural and stratigraphic history of the northwestern san bernardino mountains supports two distinct episodes of uplift in late miocene to earliest pliocene and quaternary time that we hypothesize are related to movements on low angle structures beneath the range in this paper we document the nature distribution and timing of late cenozoic deformation and deposition in the northwestern san bernardino mountains and we illustrate the neotectonic evolution of the area in a series of interpretive paleotectonic block diagrams in the first episode of deformation late miocene to earliest pliocene motion on the south southwest directed squaw peak thrust system disrupted drainage in pre existing miocene nonmarine basins and uplifted the western third of the present range to form the ancestral san bernardino mountains crystalline rocks of the san bernardino mountains were thrust southward across the present site of the san andreas fault between 9 5 and 4 1 ma at a time when the san gabriel fault was the active strand of the san andreas transform system we speculate that the liebre mountain crystalline block at the northern margin of the ridge basin may be the missing upper plate of the squaw peak thrust now offset along the san andreas fault the second episode of deformation began with uplift of the northern plateau of the modern san bernardino mountains on north directed range front thrusts in early pleistocene time between 2 0 and 1 5 ma synchronous uplift of the northern plateau recorded in early pleistocene fanglomerates on the northwestern margin of the range is interpreted to be the result of movement of a relatively coherent crustal block northward up a south dipping detachment ramp beneath the central range in middle pleistocene time activity on the northern range front began to wane and the locus of uplift shifted to a narrow zone of arching and northward tilting adjacent to the san andreas fault which subsequently migrated rapidly northwestward along the san andreas fault from the western san bernardino mountains into the northeastern san gabriel mountains we attribute this pattern of deformation to the passage of a bulge or strike slip ramp attached to the southwest side of the san andreas fault at depth

rare earth major and trace elements in chert from the franciscan complex and monterey group california assessing ree sources to fine grained marine sediments abstract rare earth element ree major and trace element analyses of 77 samples from the mesozoic franciscan complex and miocene monterey group of california usa indicate that magnitudes of the ce anomaly ce ce and total ree abundances sree in these rocks are controlled dominantly by a the amount of included metalliferous material b the amount of direct terrigenous input and c the overall burial rate the relative importance of these individual processes varies across an ocean basin in such a way that ree relative fractionations and sree correspond with its depositional environment our conclusions are supported by an extensive review of published ree data from various river coastal open ocean and ridge influenced waters as well as terrigenous pelagic and metalliferous sediment the chert sequences record deposition in spreading ridge open ocean basin and continental margin environments the relative importance of metalliferous and terrigenous influences and the role of scavenging from seawater may be estimated from a sample s inferred depositional distance km from the spreading ridge the major element chemistry and the stratigraphie context the ce ce values are low 0 29 in the vicinity of spreading ridges and trend to successively higher 1 values with decreasing metalliferous and increasing terrigenous influences other ree indicators ree lu n la n eu eu also respond to metalliferous and terrigenous influences near the spreading ridge chert ree appears determined by burial rate while shale ree responds to metalliferous abundance in open ocean and continental margin environments ree is controlled by sediment exposure time and therefore is related inversely to burial rate ree data are consistent with the major elements fe2o3 mno and al2o3 in reflecting the respective metalliferous and terrigenous sources p2o5 and cao do not vary with ce ce in any environment but cao shows a weak negative correlation with ree trace element trends e g v cr cu ge si rb sr y th u in general can similarly be accounted for in the context of depositional position relative to metalliferous and terrigenous inputs rees in chert appear less affected by post depositional processes than either major or trace elements indicating that rees are better tools for paleoceanographic or tectonic reconstructions that are based on chert chemistry this work complements recent efforts to elucidate the factors determining large scale ree distributions in marine sediments and has direct bearing on previous attempts to use the ce anomaly in older rocks and sediments as a recorder of secular variations and anoxic events in the overlying water column

palaeomagnetism of middle triassic red bedded cherts from southwest japan equatorial palaeolatitude of primary magnetization and widespread secondary magnetization summary middle triassic anisian red bedded cherts were collected from the ajiro area in kyushu island southwest japan for a palaeomagnetic study thermal demagnetization showed five distinct remanent magnetization components from the cherts the lowest temperature component below 200 c component a is a present day viscous overprint the second up to 420 c component b and third demagnetized up to 580 c component c components are secondary magnetizations of thermoviscous and chemical origin respectively both of which reside in magnetite the fourth removed component component d was demagnetized at 630 c and is a secondary magnetization carried by haematite components b and c are considered to be a result of widespread remagnetization in southwest japan during the cretaceous the basis of this consideration is that red chert remagnetizations from an area about 600 km away from the present study area are of the same origins with unblocking spectra similar to those observed in this study the last removed component during thermal demagnetization up to 695 c component e is a primary magnetization carried by haematite the directions of this component after correction for the inclination flattening yielded a mean palaeolatitude of 2 s at the time of deposition in the middle triassic the ajiro cherts accreted as part of an accretionary complex to the eastern margin of the south china block during the middle jurassic and were then translated northwards from the continental margin to their present position through a margin parallel translation process owing to the oblique convergence of the oceanic plate

melting behavior of fluid inclusions in laboratory grown halite crystals in the systems naclh2o naclkclh2o naclmgcl2h2o and naclcacl2h2o abstract the chemical composition of aqueous fluid inclusions in crystals of halite can be accurately determined from observed melting behaviors of ice hydrohalite and sylvite some fluid inclusion melting behaviors observed in laboratory grown halite crystals systems nacl h 2 o nacl kcl h 2 o nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o differ from predicted stable equilibrium relations in the nacl h 2 o and nacl kcl h 2 o systems observed first melt temperatures are up to 15 c below the equilibrium eutectic temperatures of 21 2 and 22 9 c respectively the final melting temperature of ice in the presence of hydrohalite and the final melting temperature of hydrohalite are reproducible and match predicted melting temperatures the limit of detection of sylvite daughter crystals in the nacl kcl h 2 o system is approximately 5 wt 1 molal kcl final melting temperatures of sylvite match published equilibrium data to within 0 3 c in the nacl kcl h 2 o system at halite saturation m kcl can be determined from the final sylvite dissolution temperature or from the final melting temperature of hydrohalite fluid inclusions in the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems that form stable salt hydrates mgcl 2 12h 2 o and cacl 2 6h 2 o during freezing first melt within 3 c of predicted eutectic temperatures 37 and 52 c however fluid inclusions with mgcl 2 or cacl 2 may also start melting at temperatures as low as 80 c such low first melt temperatures indicate the presence of metastable salt hydrates presumably mgcl 2 8h 2 o mgcl 2 6h 2 o or cacl 2 4h 2 o the formation of metastable phases during freezing of fluid inclusions can lead to misinterpretation of the chemical composition of fluid inclusions in natural samples this is especially true for fluid inclusions with first melt temperatures below 37 c which may be erroneously interpreted as being rich in cacl 2 the final melting of ice in the presence of hydrohalite may vary by more than 15 c in fluid inclusions of different size but identical bulk composition and occurs at lower temperatures than predicted in fluid inclusions from the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems however the final melting temperature of ice in inclusions which fail to nucleate hydrohalite and the final melting temperature of hydrohalite are reproducible to within 0 1 c and can be used to determine mgcl 2 and cacl 2 molalities

stochastic analysis of unsaturated flow in heterogeneous soils 3 observations and applications results of stochastic theory for flow in heterogeneous soils are analyzed by comparisons with laboratory experiments and field observations and through applications examples the two key theoretical results are 1 the variability of capillary pressure or moisture content increases when mean capillary pressure increases and 2 the anisotropy ratio horizontal vertical of effective mean unsaturated hydraulic conductivity increases when mean capillary pressure increases or mean moisture content decreases comparisons with the field data on moisture content and capillary pressure variability show trends similar to those predicted by the theory calculations of hydraulic conductivity anisotropy based on two actual soils show that the variations in soil texture produce large changes in anisotropy as the mean capillary pressure changes several previously reported field observations and laboratory experiments support the theoretical finding of a capillary pressure dependent hydraulic anisotropy for unsaturated flow the importance of this anisotropy effect in applications involving groundwater recharge irrigation surface runoff generation and waste isolation is discussed

accreted oceanic materials in japan abstract the phanerozoic circum pacific orogenic belts contain numerous ocean derived materials accreted through plate converging processes japanese islands in particular display various kinds of oceanic materials of different origins including fragments of seamounts oceanic reef limestone morb like rocks and oceanic mantle and pelagic sediments the compilation of these rocks in many subduction complexes of late permian to the present led to following conclusions accretion processes work effectively only for materials primarily composing the upper portion of subducting oceanic crust i e layer 1 and layer 2 many fragments of seamount with alkali basalt 600 hot spot seamount 26 oceanic reef limestone 291 morb like basalt 200 and numerous cherts more than 1000 are recognized as ancient oceanic materials accreted to the japanese islands however gabbros and mantle materials of layer 3 and lower parts of the oceanic lithosphere scarcely occur in subduction accretion complexes except for a few examples of back arc basin or fore arc origin accretion occurs episodically in southwest japan oceanic materials were accreted intermittently in 1 a end permian 2 b middle late jurassic 3 c late cretaceous times 4 d at ca 50 ma and 5 e in miocene times while in northeast japan and hokkaido this occurred in b middle late jurassic c late cretaceous and f early cretaceous times in contrast to the general belief on accretion of younger oceanic plates the majority of japanese subduction accretion complexes were formed during the subduction of plates up to 160 ma old the accretionary events in end permian and middle late jurassic times coincide with northward collision of ancient island arcs oceanic rises or seamount chains of hot spot origin with the asian continent accretion relevant to subduction of older plates may be controlled by the collision subduction process of these topographic reliefs on an oceanic plate in addition the chronological coincidence with the continent collision amalgamation between the sino korean and siberian platforms and between the sino korean and yangtze blocks also implies collision induced voluminous supply of elastics from back arc regions and its contribution to the formation of huge accretionary complexes accreted fragments of ancient seamounts are much smaller than the average size of modern seamounts this implies that most parts of a colliding seamount are not accreted but subducted together with the underlying oceanic crust to much deeper levels with respect to the metamorphic grades for japanese subduction complexes oceanic materials have less than 1 vol in the zeolite facies 15 20 in the prehnite pumpellyite metagraywacke facies and ca 30 in the greenschist glaucophane schist facies and albite epidote amphibolite fades this relationship indicates that the major process for landward accretion of oceanic materials is not off scraping or sedimentary mixing at the trench but underplating subcretion at much deeper levels of a subduction zone

remnants of late permian middle triassic ocean islands in northern tibet implications for the late stage evolution of the paleo tethys ocean abstract in this paper we present new data for the tianquan tq and dabure db ocean islands in the western segment of the longmuco shuanghu lancangjiang suture zone northern tibet including the results of major and trace element analyses zircon u pb dating and hf isotope analyses our aim was to assess the genesis of these ocean islands and to consider the implications for the tectonic evolution of the region as a whole both tq and db retain an ocean island type double layered structure comprising a volcanic basement basalt and andesite and an oceanic sedimentary cover sequence conglomerate limestone and chert the basalts and andesites in the tq and db are enriched in light rare earth elements and high field strength elements nb ta zr hf and ti yielding chondrite normalized ree patterns and primitive mantle normalized trace element patterns that are similar to those of ocean island basalts given the small and generally positive ehf t values of the tq andesites 4 25 to 6 22 and db andesites 0 59 to 1 97 mostly 0 we conclude that the basalts were derived from the partial melting of garnet peridotite in the mantle and that the andesites were formed by fractional crystallization of the mafic parent magma derived from the garnet peridotite mantle the ascending magmas underwent varying degrees of fractional crystallization but were not contaminated by crustal material these features indicate that both tq and db are typical ocean islands that formed in an ocean basin geochemical analyses of cherts from tq and db show that they contain terrigenous material indicating the proximity of a continental margin the andesites of tq contain zircons that yield two u pb ages of 251 ma given that ages of 246 247 and 254 ma had been reported previously we conclude that tq formed during the late permian early triassic the andesites of db contain zircons that yield u pb ages of 242 and 246 ma taking into account the youngest age of 244 ma from the db basalt we conclude that db formed during the middle triassic these data combined with the geological history of the region indicate that the development of the longmuco shuanghu lancangjiang paleo tethys ocean continued after the early permian and that the closure of this ocean was diachronous from east to west the eastern segment of the ocean closed during the early triassic however the western segment remained at least partially open until the middle triassic although the ocean was relatively small at this time the ocean finally closed in the late triassic