the coupling mechanism of basin and orogen in the western ordos basin and adjacent regions of china abstract during the late triassic and jurassic three structural belts developed in the western ordos basin and adjacent regions of china the alxa compressive wedge the helanshan structural belt and the liupanshan fold and thrust belt three types of basin also developed a late triassic composite basin with a northwestern ordos rift sub basin and a southwestern ordos foreland sub basin an early middle jurassic intracratonic basin and a late jurassic foreland type molasse wedge it is suggested that these basins resulted from late triassic unconstrained lateral extrusion and jurassic constrained lateral extrusion the alxa region is interpreted as an extrusional wedge bounded by strike slip deformation which escaped laterally from the indentation of the liupanshan thrust belt from the south during the late triassic the sino korean block to the east of helanshan was controlled by a stress state with nearly e w trending extension at this stage extrusion was unconstrained the helanshan developed as a rift sub basin due to transtensional tectonics at the lateral margin of the wedge at this time a foreland sub basin was formed in front of the liupanshan thrust belt during the jurassic the sino korean block to the east of the helanshan was gradually compressed westwards and the extrusion structure became constrained the early middle jurassic shows a transitional stage from unconstrained to constrained extrusion and the ordos basin developed as an intracratonic basin from the latest middle jurassic to the late jurassic intense lateral escape and opposite compression led to the formation of the helanshan fold and thrust belt and its frontal foreland molasse wedge at the same time another foreland molasse wedge was developed in front of the liupanshan thrust belt the switch from rifting to thrusting in the helanshan is a result of the changing stress field at the circum pacific plate boundary the clockwise rotation of the sino korean block to the east of the helanshan and the anticlockwise rotation of the alxa block

occurrence of pyrites in sandstone type uranium deposits relationships with uranium mineralization in the north ordos basin china abstract large quantities of pyrite have been discovered near the ore bearing segments of the sandstone type uranium deposits in the north ordos basin in this study the electron probe microanalysis scanning electron microscopy and isotope geochemical analysis were used to systematically investigate the morphology composition and s isotopes of the pyrites in these deposits and their genetic order relative to the other main altered minerals based on the regional tectonic evolutionary sequence of the basin the relationships between the pyrites and uranium mineralization are discussed macroscopically the pyrites were found to occur in lumpy banded disseminated star like or sheet like form microscopically they exist either as detrital grains or inside detrital grains as idiomorphic grains in colloidal or framboidal form inside mica minerals in banded or petaloid form and in other forms related to biological cells or microorganisms the 34s values in the pyrites are highly variable 7 3 to 37 2 but principally in the proximity of 30 and display obvious biogenic origin taking into consideration the extremely low u contents in the pyrites and achavalites iron selenide the genetic order of the main altered minerals is determined as follows detrital pyrites clay mineral overgrowths micritic calcites during the diagenetic stage and achavalites pyrites coffinite pitchblende vanadium oxides sparry calcites during the metallogenic stage the broad presence of pyrites in the jurassic yan an formation during the basin s evolution provided detrital pyrites and organic detritus for the overlying formations the zhiluo formation host of the uranium mineralization is also home to some primary spherical colloidal or framboidal pyrites the cretaceous was the main epigenetic uranium metallogenetic period as well as the main pyrite development period of the area the pyrites which are typically colloidal have cemented the earlier framboidal pyrites and other minerals and are closely associated with the redox reaction related to uranium mineralization in the paleogene uranium mineralization mainly occurred by the redox migration of early shallow deposits to and fresh pyrites forming in deeper levels

evidence for sea level and monsoonally driven variations in terrigenous input to the northern east china sea during the last 24 3 ka geochemical and sedimentological analyses of core pc 1 recovered from the northern east china sea ecs provide insights into variations in terrigenous input associated with sea level and climate changes over the past 24 3 ka based on high resolution multiproxy records our results suggest that the competing processes of sea level and monsoonally driven precipitation determined terrigenous input to the northern ecs dominance of terrigenous material along with relatively light globigerinoides ruber 18o indicates that the last glacial maximum lgm lowstand of sea level has occurred during the period 21 5 19 6 ka not suggesting an early slow rise but supporting the conventional lgm age of 21 ka this lgm lowstand was terminated by the rapid sea level rise of 19 ka meltwater pulse mwp which is well expressed by the nearly synchronous decreases in both terrigenous detritus and mean grain size from 19 6 to 18 9 ka mwp 1a is clearly marked in our records by a sharp reduction in terrigenous input and pronounced maxima of g ruber 18o at 15 3 14 8 ka given the considerable age uncertainties of deglacial marine radiocarbon samples a slightly increasing input of terrigenous matter is noted after 13 4 ka potentially pointing to a sea level fall following the inter allerod cooling period which was seldom reported previously although mwp 1b did not leave robust signatures in terrigenous input it is explicitly captured by the heavy 18o of g ruber and decline in mean grain size at 11 5 10 9 ka mwp 1c probably occurred in a broad millennial interval with multiple peaks which are robustly marked by the abrupt variations in terrigenous input and marine organic matter at 9 7 9 3 and 9 1 ka respectively during the late holocene the effect of continuously weakening monsoon precipitation overwhelmed that of stable sea level resulting in a uniform increase in the proportion of marine derived organic matter after 5 5 ka

numerical evaluation of land subsidence induced by groundwater pumping in shanghai to predict the future behavior of land subsidence in shanghai due to pumping of groundwater a numerical model is established in the proposed model groundwater flow in three dimensional conditions and soil deformation in one dimen sional conditions are calculated the model takes into account the multi aquifer aquitard hydrogeological condition of the soft deposit of shanghai the variation of the coefficient of compressibility and coefficient of hydraulic conductivity of the soils with the consolidation process are simulated relationships among land subsidence groundwater withdrawal volume and groundwater level are analyzed comparison between the measured value and calculated value shows that the model simulates the measured value fairly well the future of land subsidence behavior due to groundwater withdrawal is predicted and discussed via consideration of the variation of the following parameters in the future 30 years net withdrawn volume of groundwater pumping layer and pumping region resume un modele numerique est propose afin de predire le comportement futur d un affaissement de sol cause par le pompage de l eau souterraine a shanghai dans le modele propose l ecoulement de l eau souterraine en trois dimensions et la deformation du sol en une dimension sont calcules le modele considere la condition hydrogeologique multi aquifere aquitard du depot mou de shanghai les variations du coefficient de compressibilite et du coefficient de conductivite hy draulique des sols lors du processus de consolidation sont simulees les relations entre l affaissement du sol le volume de retrait de l eau souterraine et le niveau phreatique sont analysees des comparaisons entre les valeurs mesurees et calculees montrent que le modele peut simuler les valeurs mesurees relativement bien le comportement futur du sol en affaissement cause par le retrait de l eau souterraine est predit et discute en considerant les variations pour les prochains 30 ans pour les parametres suivants le volume net d eau souterraine retire la couche de pompage et la region de pompage mots cles pompage de l eau souterraine affaissement du sol ecoulement de l eau souterraine en trois dimensions consoli dation en une dimension prediction traduit par la redaction

two classes of volcanic plumes on io abstract comparison of voyager 1 and voyager 2 images of the south polar region of io has revealed that a major volcanic eruption occured there during the period between the two spacecraft encounters an annular deposit 1400 km in diameter formed around the aten patera caldera 311 w 48 s the floor of which changed from orange to red black the characteristics of this eruption are remarkably similar to those described earlier for an eruption centered on surt caldera 338 w 45 n that occured during the same period also at high latitude but in the north both volcanic centers were evidently inactive during the voyager 1 and 2 encounters but were active sometime between the two the geometric and colorimetric characteristics as well as scale of the two annular deposits are virtually identical both resemble the surface features formed by the eruption of pele 255 w 18 s these three very large plume eruptions suggest a class of eruption distinct from that of six smaller plumes observed to be continously active by both voyagers 1 and 2 the smaller plumes of which prometheus is the type example are longer lived deposit bright whitish material erupt at velocities of 0 5 km sec 1 and are concentrated at low latitudes in an equatorial belt around the satellite the very large pele type plumes on the other hand are relatively short lived deposit darker red materials erupt at 1 0 km sec 1 and rather than restricted to a latitudinal band are restricted in longitude from 240 to 360 w both direct thermal infrared temperature measurements and the implied color temperatures for quenched liquid sulfur suggest that hot spot temperatures of 650 k are associated with the large plumes and temperatures 2 in their annuli whereas the large plumes apparently do not two other plumes that occur at either end of the linear feature loki may be intermediate or hybrid between the two classes exhibiting attributes of both additionally loki occurs in the area of overlap in the regional distributions of the two plume classes two distinct volcanic systems involving different volatiles may be responsible for the two classes we propose that the discrete temperatures associated with the two classes are a direct reflection of sulfur s peculiar variation in viscosity with temperature over two temperature ranges 400 to 430 k and 650 k sulfur is a low viscosity fluid orange and black respectively at other temperatures it is either solid or has a high viscosity as a result there will be two zones in io s crust in which liquid sulfur will flow freely a shallow zone of orange sulfur and a deeper zone of black sulfur a low temperature system driven by so 2 heated to 400 to 400 k by the orange sulfur zone seems the best model for the small plumes a system driven by sulfur heated to 650 k by hot or even molten silicates in the black sulfur zone seems the best explanation for the large plume class the large pele type plumes are apparently concentrated in a region of the satellite in which a thinner sulfur rich crust overlies the tidally heated silicate lithosphere so the black sulfur zone may be fairly shallow in this region the prometheus type plumes are possibly confined to the equatorial belt by some process that concentrates so 2 fluid in the equatorial crust

the causes of apparent overconsolidation in the namak marine deposit korea an intensive experimental study was carried out to investigate the causes of the overconsolidation phenomena in the namak new city site korea geological events in conjunction with sea level changes groundwater fluctuation weathering leaching and cementation were examined as possible causes of overconsolidation in addition to oedometer and triaxial tests radiocarbon dating geochemical components and pore water chemistry were analysed it was shown that the overconsolidation in the upper marine clay deposit was not caused by stress reductions such as erosion and groundwater fluctuation furthermore weathering or leaching seemed unlikely the apparent overconsolidation can be explained by cementation which is indicated by profiles of the sulphate and potassium ion concentrations in the pore water at the early stage of the holocene marine deposition the rate of deposition was 4 4 mm yr thereafter it was reduced to 1 4 mm yr controlling chemical processes such as sulphate reduction and ion exchan

role of fluid mixing and fault related sulfide in the origin of the ray point uranium district south texas the lamprecht and felder deposits are two of many roll type uranium deposits hosted by the miocene oakville sandstone in the ray point south texas uranium district the deposits in this district are aligned parallel to or are intersected by the oakville fault which suggests control by the faults on their origin and or preservation the lamprecht and felder deposits show fundamentally similar patterns of geochemical zonation and of distribution of authigenic iron disulfide fes sub 2 minerals distribution of u mo and se are typical of roll type deposits that result from invasion of geochemically reduced rock by oxygenated uranium bearing solutions sulfur content of these deposits is high as much as 9 with almost all sulfur occurring as fes sub 2 minerals organic carbon is virtually absent four distinct stages of fes sub 2 mineral formation are recognized 1 a generation of isotopically light delta sup 34 s 0 o and 4 a yet later generation of marcasite with isotopically light sulfur close to the values of stages 1 and 2 the alteredmore tongue in these deposits is anomalous in that it contains fes sub 2 minerals in contrast to other texas and wyoming roll type deposits which typically have an oxidized ferric iron bearing altered tongue the dominant fes sub 2 mineral in the altered tongue is isotopically heavy pyrite stage 3 with subordinate amounts of late marcasite stage 4 less

experimental study of migration of potassium ion through a two layer soil system a barrier system based on the hydraulic trap design concept for a landfill was proposed to study the field scenario in which a clay liner is underlain by a granular layer functioning as a secondary leachate drain layer a laboratory advection diffusion test was performed to investigate factors controlling the transport of contaminants in a two layer soil system the soils used for this study were ariake clay and the underlying layer shirasu soil from the kyushu region of japan potassium k was selected as the target chemical species with an initial concentration of 905 mg l 1 the effective diffusion coefficients d e of k for ariake clay and shirasu soil were back calculated using an available computer program pollute v 6 3 values of d e derived from this experiment are consistent with previously published ones the ariake clay has lower d e than the shirasu soil the hypothesis that mechanical dispersion can be considered negligible is reasonable based on both the observation that the predicted values well fit the experimental data and the analyses of two dimensionless parameters parametric analyses show that transport of k through soils is controlled by advection diffusion rather than diffusion only whereas at low darcy velocity i e 10 9 m s 1 transport of k will be controlled by diffusion applications of the test results and parametric analysis results in practical situations were reviewed

grain size control on sr nd isotope provenance studies and impact on paleoclimate reconstructions an example from deep sea sediments offshore nw africa five sediment cores from offshore nw africa were analyzed for strontium and neodymium isotope ratios to reconstruct temporal variations in continental weathering regimes sediments were taken from three time slices with well known and distinctive environmental conditions present day dry and warm similar to 6 ka wet and warm and similar to 12 ka dry and cold terrigenous sediment samples were split into two size fractions to distinguish between the two dominant transport mechanisms offshore nw africa fluvial 0 10 mu m and aeolian 10 40 mu m sr isotope data record evidence of marked grain size control with higher isotopic ratios in the fine fraction in contrast epsilon nd values are largely unaffected by grain size minor variability in nd isotope data at each sampling site indicates near constant sources of terrigenous matter over the last similar to 12 ka variations in sr isotope ratios are interpreted to reflect major changes in the evaporation precipitation balance we suggest that the sr nd isotope data record a latitudinal shift of the northern limit of the african rainbelt and associated wind systems causing changes in the humidity and rate of chemical weathering over nw africa while hyperarid conditions prevailed similar to 12 ka more humid conditions and intensified monsoonal rainfall at similar to 6 ka resulted in greater breakdown of easily weathered k bearing phases and increased sr 87 sr 86 in the detritus in late holocene times the monsoonal circulation diminished resulting in a return to arid conditions our results clearly show that it is of vital importance in paleoenvironmental studies to carry out isotopic analyses on individual sediment fractions that were carried to the studied deposition site by distinct sediment transport mechanisms if isotopic analyses are carried out on bulk sediments the observed variability in isotopic values most likely represents changes in the particle size and mixing proportions of the sediment subpopulations

parameter variability of undrained shear strength and strain using a database of reconstituted soil tests during construction the mobilization of undrained shear strength must be limited to avoid soil failure soil strains must be controlled to avoid compromising structural serviceability to assess f

transformation models for effective friction angle and relative density calibrated based on generic database of coarse grained soils this study compiles a generic database of seven parameters including relative density and friction angle for coarse grained soils from 176 studies covering a wide range of reconstituted and in situ coarse grained soils this database labeled as sand 7 2794 is dominated by data from laboratory reconstituted soils such as erksak hokksund monterey ottawa sacramento river ticino and tonegawa sands about 15 of the data points in the database are in situ samples obtained from tube sampling block sampling or ground freezing techniques the correlation behavior among some parameters in the database is consistent with existing transformation models in the literature mine tailings volcanic soils railroad ballast gravelly soils with significant cobble or boulder content and soils with high fines contents are removed from the database because they exhibit inconsistent behavior soils subjected to very high effective stresses are also removed from the database the generic database is adopted to

a quantitative model of ground water flow during formation of tabular sandstone uranium deposits tabular sandstone uranium deposits constitute the largest uranium resource type in the united states a major point of contention has been the nature and direction of the ground water flow this paper presents a quantitative simulation of regional ground water flow during uranium deposition in the westwater canyon member and jackpile sandstone member of the upper jurassic morrison formation in the san juan basin input for the four layer finite difference model was from thicknesses and sandstone mudstone ratios in each layer from 1 600 drill holes and 100 measured sections and from palcotopographic reconstructions topographic slope shoreline position and density contrasts in the lake and pore fluids controlled the directions of flow and recharge discharge areas the most important results for uranium ore deposit formation are that regional ground water discharged throughout the basin regional discharge was concentrated along the shore line or playa margin flow was dominantly gravity driven and compaction dewatering was negligible a strong association is found between the tabular sandstone uranium deposits and major inferred zones of mixed local and regional ground water discharge the results of ground water modeling favor the brine interface model over the lacustrine humate model for uranium deposition

characterisation and engineering properties of tiller clay abstract a detailed characterisation of the quick clay underlying the ntnu research site at tiller trondheim is presented the objective of the work is to provide guidance on quick clay parameters to engineers and researchers working with similar clays in scandinavia and north america especially on landslide hazard assessment the material is lightly overconsolidated and is characterised by its high degree of structure and very high sensitivity quick clay clay and water contents are both about 40 the plasticity index is low 5 this relates to the low active minerals of the clay and silt fractions illite chlorite and quartz feldspars respectively undrained shear strength is of the order of 30 kpa to 50 kpa medium stiff and increases with depth the deposit is consistent across the site and its properties are similar to other norwegian quick clays significant efforts have been made into examining sample disturbance effects on the material it was found that thin walled steel fixed piston samples can yield results similar to those of block samples provided the work is carried out with extreme care and storage time is minimised the piezocone cptu test proved very useful in characterising the material

a reevaluation of using laboratory shear tests the expression for the average undrained shear strength mobilized on a slip surface in the field resulted from in situ vane and oedometer data combined with a correction factor obtained from the computed factor of safety of unstable embankments footings and excavations it is shown here that the same expression for mobilized undrained strength of soft clays is also obtained from laboratory shear tests by taking into account anisotropy and time effects this result is highly significant since the laboratory undrained shear strength data as well as the correction factor for the time effect are completely unrelated to the in situ data that previously resulted in the expression for field mobilized undrained shear strength key words mobilized undrained shear strength in situ vane test laboratory shear tests

architecture of a sandstone uranium reservoir and the spatial distribution of its internal carbonaceous debris a case study of the zhiluo formation eastern ordos basin northern china abstract the sandstone of the middle jurassic zhiluo formation in the eastern ordos basin provides the opportunity for conducting a critical case study of the architecture and internal carbonaceous debris cd distribution of a sandstone uranium reservoir located in a field outcrop in shiwan the 16 24 m thick outcrop section is a sandstone dominated subaqueous distributary channel succession in which six lithofacies types se st sm sp sh and fl occur in a predictable order of repeated fining upward cycles these facies emphasize that the dominant structures had been deposited under lower flow regime conditions various groups of associated facies have been identified as six distinct architectural elements intrachannel units longitudinal bar transverse bar diagonal bar dune complex and abandoned channel deposits within a framework of five orders of bounding surfaces these elements with specific lithofacies associations and spatial relationships indicate that the subaqueous distributary channel had involved in four stages of formation channel occurring channel flooding channel waning and channel abandonment moreover as one of the most significant reductants in the sandstone succession the cd occurs in the form of channel lags and is concentrated in the middle and lower parts of the lag deposit zones the spatial distribution of cd within the studied succession is controlled by the sandstone architecture and the cd rich zones are preserved exclusively upon the basal surfaces of intrachannel units longitudinal and transverse bars this study can be helpful for exploring the distribution of metallogenic flow field as well as the restriction of the reductants on interlayer oxidation

sandstone type uranium deposits in the ordos basin northwest china a case study and an overview abstract this paper provides a comprehensive review on studies of sandstone type uranium deposits in the ordos basin northwest china as the second largest sedimentary basin the ordos basin has great potential for targeting sandstone type u mineralization the newly found and explored dongsheng and diantou sandstone type uranium deposits are hosted in the middle jurassic zhilou formation a large number of investigations have been conducted to trace the source rock compositions and relationship between lithic subarkose sandstone host rock and uranium mineralization an optical microscopy study reveals two types of alteration associated with the u mineralization chloritization and sericitization some unusual mineral structures with compositional similarity to coffinite have been identified in a secondary pyrite by sem these mineral phases are proposed to be of bacterial origin following high resolution mapping of uranium minerals and trace element determinations in situ moreover geochemical studies of ree and trace elements constrained the mechanism of uranium enrichment displaying lree enrichment relative to hree trace elements such as pb mo and ba have a direct relationship with uranium enrichment and can be used as index for mineralization the source of uranium ore forming fluids and related geological processes have been studied using h o and c isotope systematics of fluid inclusions in quartz veins and the calcite cement of sandstone rocks hosting u mineralization both h and o isotopic compositions of fluid inclusions reveal that ore forming fluids are a mixture of meteoric water and magmatic water the c and s isotopes of the cementing material of sandstone suggest organic origin and bacterial sulfate reduction bsr providing an important clue for u mineralization discussion of the ore genesis shows that the greenish gray sandstone plays a crucial role during processes leading to uranium mineralization consequently an oxidation reduction model for sandstone type uranium deposit is proposed which can elucidate the source of uranium in the deposits of the ordos basin based on the role of organic materials and sulfate reducing bacteria we discuss the mechanism of uranium deposition responsible for the genesis of these large sandstone type uranium deposits in this unique sedimentary basin

generic transformation models for some intact rock properties a global intact rock database of nine parameters including uniaxial compressive strength and young s modulus is compiled from 184 studies this database labeled as rock 9 4069 consists of 27

last deglaciation in the okinawa trough subtropical northwest pacific link to northern hemisphere and tropical climate 1 detailed deglacial and holocene records of planktonic delta o 18 and mg ca based sea surface temperature sst from the okinawa trough suggest that at similar to 18 to 17 thousand years before present kyr b p late spring early summer ssts were approximately 3 degrees c cooler than today while surface waters were up to 1 practical salinity unit saltier these conditions are consistent with a weaker influence of the summer east asian monsoon eam than today the timing of suborbital sst oscillations suggests a close link with abrupt changes in the eam and north atlantic climate a tropical influence however may have resulted in subtle decoupling between the north atlantic and the okinawa trough eam during the deglaciation okinawa trough surface water trends in the holocene are consistent with model simulations of an inland shift of intense eam precipitation during the middle holocene millennial scale alternations between relatively warm salty conditions and relatively cold fresh conditions suggest varying influence of the kuroshio during the holocene

depositional and post depositional geochemistry and its correlation with the geotechnical properties of marine clays in ariake bay japan the mineralogy geochemistry and geotechnical properties of clay samples in ariake bay japan are presented the mineralogy and geochemistry are discussed in terms of depositional and post depositional processes and the correlations of the clay mineralogy and geochemistry with the geotechnical properties were examined by multiple regression analysis the most predominant clay mineral in the deposits was found to be smectite the vertical distribution of trace elements in the deposits was indicative of the periodical changes in the parent materials involved in the depositional processes the chloride concentration in the pore water varied according to a change in the sea level from brackish to marine and then brackish towards the surface the higher iron oxide contents near the surface and in the deepest zones were the results of pyrite oxidation in the deposits due to weathering under subaerial conditions smectite content was the most predominant governing factor for the consistency limits and activi

the measurements of soil parameters relevant to tunnelling in clays a comprehensive laboratory program was carried out on specimens trimmed from 152 mm diameter piston samples of a soft silty clay and a varved clay at a tunnel site in thunder bay results of conventional triaxial tests as well as special tests for the determination of anisotropic elastic parameters simple shear tests and stress path tests are presented results indicate that the unloading moduli are about twice the loading moduli the poisson s ratios in unloading are about three times those in loading but the independent shear modulus is relatively unaffected while the modulus is sensitive to mode of consolidation drainage and direction of stress path the stress states at failure of all the different types of tests fall close to a single envelope for compression and extension the choice of soil parameters for the analysis of deformation in tunnelling in soft clays is discussed key words clay tunnelling stress path deformation modulus shear modulus anisotropic elastic parameters failure env

so2 rock interaction on io reaction under highly oxidizing conditions laboratory simulations have been carried out to test the possibility that interactions of so 2 and silicates can produce na s compounds which can account for the observed surface enrichment of na relative to si on io a wide variety of silicate compositions were heated under oxidizing conditions with a so 2 o 2 1 gas phase at a mid level crustal temperature for io 1123k all experiments produced sulfate deposits on the silicate surfaces the nature of the sulfate changed systematically with the silicate ca na ratio with mixtures of caso 4 and na rich sulfate formed by basaltic compositions having higher ca na but only alkali rich sulfates formed for more granitic low ca na compositions for crystalline albite and an albite orthoclase eutectic glass composition k and al rich sulfates were formed assuming that burial of so 2 to the temperatures of our experiments is plausible on io and that somewhat less oxidizing conditions do not qualitatively change the results so 2 rock interactions producing na rich sulfates could account for the io surface enrichment in na observations on minor elements such as k or ca in the atomic cloud or in magnetospheric ion spectra could be used to identify sulfates as io surface phases and conceivably even define ionian crustal magma types many analyses show significant s excesses which are best interpreted as due to the presence of bisulfate hso 4 components and nahso 4 deserves consideration as an io surface mineral the possibility of elemental s on io can be regarded as a totally separate issue from the problem of the surface na enrichment

systematic variations of h o c isotopes in different alteration zones of sandstone hosted uranium deposits in the southern margin of the yili basin xinjiang china a review and implications for the ore forming mechanisms abstract the meso cenozoic yili basin in northwestern china hosts important uranium and coal resources the uranium deposits are mainly hosted by sandstones and are characterized by clay and carbonate alterations within and surrounding the orebodies h o c isotopes of clay minerals and carbonate cement in the different alteration zones of the uranium deposits in the southern margin of the yili basin are summarized to examine the mechanisms of uranium mineralization the alteration zones associated with the uranium mineralization include an intensely oxidized zone a weakly oxidized zone a transitional mineralization zone and a reduced zone the d and 18o values of the parent fluids calculated from clay minerals from the different alteration zones show a linear trend that intersects the global meteoric line at a point with a 18ov smow of ca 5 and a dv smow of ca 30 which coincide with the upper end of the d 18o trend along the meteoric line of formation waters in the basin suggesting that the uranium mineralizing fluid was of meteoric origin the general trends of decreasing d and 13c and increasing 18o from the intensely oxidized zone to the reduced zone together with the fact that calculated dv smow values of the mineralizing fluids are lower than the original meteoric fluid and that the 13c values of the calcite cement overlap with those of organic matter in sedimentary rocks suggest that hydrocarbons were involved in uranium mineralization the hydrocarbons may have been important reducing agents causing precipitation of uranium minerals the hydrogen ion released from oxidation of the hydrocarbons may have been buffered by the formation of clay minerals which favors co development of clay alteration and calcite cement deviation of h o c isotopes from the general variation trends as expected from the above redox mechanism likely resulted from the dynamic nature of the redox front which changed its position in response to hydrodynamic balance between a downward flow of uranium bearing oxidizing fluid and an upward flow of reductants bearing reducing fluid from the lower part of the basin

hydrogeochemical characteristics of the sandstone hosted uranium mineralization in northern ordos basin china abstract the northern ordos basin is one of the biggest uranium resource production areas in china however the hydrogeochemical mechanism for the formation of uranium deposits remains poorly understood despite that interlayer oxidation hydrothermal fluid mineralization and gas reduction were proposed in order to provide a more comprehensive knowledge on their formation mechanism the investigation was carried out by analyzing hydrogeochemistry and environmental isotopes of waters from river lakes shallow private wells boreholes over the period from 2015 to 2016 the results showed that the analysed samples exhibited a hydrochemical heterogeneity confirmed by a large range of ph eh main cation and anion concentrations and uranium concentration in surface water quaternary shallow groundwater cretaceous confined water and jurassic confined water the piper and durov diagrams highlighted that hydrochemical facies changed with groundwater flow from shallow to deep with hco3 ca mg and hco3 ca in quaternary shallow groundwater hco3 cl ca na in cretaceous confined water and cl na and hco3 na in jurassic confined water aqueous geochemistry indicated that the jurassic ore bearing confined waters originated from the cretaceous confined waters involving both leaching processes and desulfidation nonetheless the cretaceous confined waters originated from quaternary shallow groundwater and mainly have experienced leaching processes gibbs plot indicated that with an accumulation of ions in the groundwater during runoff calcite and uraninite minerals would be oversaturated and precipitation tended to occur the variation of tds along depth indicated desulfurization occurrence in ore bearing aquifer and a decrease in migrating ability of uo22 leading to u precipitation isotopic results showed that the ore bearing confined waters were depleted in 18o and d and were located along the global meteoric water line gmwl most ore bearing confined waters plotted on or near the meteoricwater line showing their deep circulating meteoric origin uranium species study indicated that dissolved uranium was dominated by uo2 oh 3 and uo2 co3 34 which have a high migrating ability saturation index of uraninite in all water samples were determined to be below 0 indicating that this uranium deposit was currently not under mineralization the ph and eh values of the samples were located in the migration area suggesting that uranium is in a migration state under current groundwater conditions only when ph 5 8 and eh

stable isotope geochemistry and diagenetic mineralization associated with the tono sandstone type uranium deposit in japan the tono sandstone type uranium mine area middle honsyu japan is composed of miocene lacustrine sedimentary rocks in the lower part 18 22 ma and marine facies in the upper part 15 16 ma calcite and pyrite occur as dominant diagenetic alteration products in these neogene sedimentary rocks the characteristics of calcite and pyrite differ significantly between lacustrine and marine facies abundant pyrite calcite organic matter and small amounts of marcasite or pyrrhotite occur in the lacustrine facies whereas small amounts of calcite and framboidal pyrite organic matter and no marcasite or pyrrhotite are found within the marine units the 13c values of calcite in the lacustrine deposits are low 19 to 6 pdb but those in marine formation are high 11 to 3 this implies that the contribution of marine carbonate is larger in upper marine sedimentary rocks and carbon in calcite in the lower lacustrine formation was derived both from oxidation of organic matter and from dissolved marine inorganic carbon the 34s values of framboidal pyrite in the upper marine formation are low 14 to 8 cdt indicating a small extent of bacterial seawater sulfate reduction whereas those of euhedral subhedral pyrite in the lower lignite bearing arkose sandstone are high 10 to 43 implying a large extent of closed system bacterial seawater sulfate reduction the 34s and 13c data which deviate from a negative correlation line toward higher 13c values suggest methanogenic co2 production during diagenesis of the lacustrine unit large amounts of euhedral subhedral pyrite were formed facilitated by extensive bacterial reduction of seawater sulfate with concomitant oxidation of organic matter and by hydrolysis reactions of organic matter producing ch4 and co2 uranium minerals coffinite and uraninite were also formed at this stage by the reduction of u6 to u4 the conditions of diagenetic alteration within the lacustrine deposits and uranium mineralization is characterized by low eh in which nearly equal concentrations of ch4 and hco3 existed and reduced sulfur species h2s hs are predominant among aqueous sulfur species whereas diagenetic alteration of the marine formations was characterized by a predominance of so4 2 among dissolved sulfur species modern groundwater in the lacustrine formation has a low eh value 335 mv estimated and measured low eh values of modern and ancient interstitial waters in lacustrine environments indicate that a reducing environment in which u4 is stable has been maintained since precipitation of uranium minerals

io evidence for silicate volcanism in 1986 infrared observations of io during the 1986 apparition of jupiter indicate that a large eruptive event occurred on the leading side of io on 7 august 1986 universal time measurements made at 4 8 8 7 and 20 micrometers suggest that the source of the event was about 15 kilometers in radius with a model temperature of 900 kelvin together with previously reported events these measurements indicate that high temperature volcanic activity on the leading side of io may be more frequent than previously thought the inferred temperature is significantly above the boiling point of sulfur in a vacuum 715 kelvin and thus constitutes strong evidence for active silicate volcanism on the surface of io

distinct control mechanism of fine grained sediments from yellow river and kyushu supply in the northern okinawa trough since the last glacial high resolution multi proxy records including clay minerals and sr nd pb isotopes of the clay sized silicate fraction of sediments from iodp site u1429 in the northern okinawa trough provide reliable evidence for distinct control mechanism on fine grained sediments input from the yellow river and the southern japanese islands to the northern okinawa trough since 34 ka bp provenance analysis indicates that the sediments were mainly derived from the yellow river and the island of kyushu since the last glacial clay sized sediments transported from the yellow river to the study site were strongly influenced by sea level fluctuation during low sea level stage 34 14 ka bp the paleo yellow river mouth was positioned closer to the northern okinawa trough favoring large fluvial discharge or even direct input of detrital sediments which resulted about four times more flux of clay sized sediments supply to the study area as during the relatively high sea level stage 14 0 ka bp the input of kyushu derived clay sized sediments to the study site was mainly controlled by the kuroshio current and tsushima warm current intensity with increased input in phase with weakened kuroshio current tsushima warm current our study suggests that the kuroshio current was very likely flowed into the okinawa trough and thus influenced the fine grained sediment transport in the area throughout the last glacial and deglacial during 34 11 ka bp the kyushu clay sized sediment input was mainly controlled by the kuroshio current since 11 ka bp the occurrence of tsushima warm current became important in influencing the kyushu fine grained sediment input to the northern okinawa trough

the provenance of sediments in the gulf of lions western mediterranean sea in this study we undertook a reconnaissance study of sediments provenance in the gulf of lions focusing over the last 16 ka we used geochemical and isotopic tracers to determine the source of sediments and give insight into the weathering conditions prevailing sediments samples were selected both onshore and offshore from the western eastern and central part of the gulf of lions we analyzed bulk sediments coarse and fine silt and clay fractions elemental and nd isotope compositions appeared to differ from one grain size fraction to another one these are interpreted in terms of zircon addition in the coarse silt fraction for the elemental concentrations and variable sources influences for the nd isotope compositions our results indicate that sediments in the gulf of lions mainly originated from the rhone river watershed although a contribution of saharan dust is seen in one sample influence of pyrenean small rivers is minor in these samples some sr isotope compositions shifts are interpreted as reflecting variable amounts of chemical weathering that are consistent with published paleoclimatic reconstructions

quaternary sedimentary record in the northern okinawa trough indicates the tectonic control on depositional environment change abstract during the quaternary global sea level was characterized by large fluctuations in amplitude and increased frequency however the eastern marginal seas of china especially the northern east china sea and yellow sea did not experience large scale transgression until the middle pleistocene the zhe min zhejiang fujian uplift was an important barrier in the east china sea preventing transgression of sea water into the northern marginal seas of china but its quaternary evolution is still poorly constrained here we present a thick sand layer record the top age is 416 ka of the integrated ocean drilling program iodp site u1428 from the northern okinawa trough to reconstruct the history of the zhe min uplift since the middle pleistocene provenance analysis indicates that sediments from both sand and imbedded fine grained calcareous rich clay layers at the study site were mainly derived from the yellow river which for the first time indicates that the yellow river sediments could influence the northern okinawa trough since at least the middle pleistocene significant change of lithology at iodp site u1428 at 416 ka was attributed to the large scale subsidence of the zhe min uplift which is probably due to the rapid uplifting of tibet during 0 52 0 38 ma before 416 ka obstacle of the emersed zhe min uplift induced extremely severe reworking and promoted sand ridge formation in the shelf edge of southeastern yellow sea and supplied sand sediments to the northern okinawa trough during transgression and high sea level stages after the subsidence of the zhe min uplift at 416 ka westward of tidal sand ridge and yellow river mouth with the process of shelf transgressions favored fine grained sediments input to the northern okinawa trough even during low sea level stages the flat terrain of the east asian marginal sea shelf and low rainfall amount resulted in low discharge of yellow river and supplied fine grained particles to the northern okinawa trough

the microscopic characteristics of shanghai soft clay and its effect on soil body deformation and land subsidence compaction of the 40 m thick upper shanghai soft clay contributes to land subsidence in the shanghai region the upper clay a marine deposit continuously subsides at rate of 3mm years despite mitigation strategies designed to control land subsidence these strategies include the artificial injection of water into the subsurface data describing the particle size distribution pore size distribution microstructure mineralogical composition pore solution composition and cation exchange capacity indicate that the clay is semidispersed substable and susceptible to compaction an evaluation of soil body deformation caused by artificial injection of dilute water into a marine clay suggests that depression of the electrostatic double 1ayer in the marine clays may be responsible for the observed compaction and resulting subsidence a decrease in the swelling pressure of the marine clays might result from a reduction in the concentration of dissolved sodium in pore fluids when calcium bicarbonate water is injected thus ironically the strategy designed to mitigate land subsidence could be contributing to it increasing the concentration of dissolved salts in the injection water may prevent the collapse of the clay structure and halt or reverse the subsidence process the analysis results indicate the deformation of soft clay by consolidation is subject to its microscopic physical and chemical features rather than the fluctuation of groundwater level this continuous compression contributes as a major part to the land subsidence in shanghai

archean paleoproterozoic crustal evolution of the ordos block in the north china craton constraints from zircon u pb geochronology and hf isotopes for gneissic granitoids of the basement abstract the ordos block has been considered as an archean micro block in north china craton however its formation and evolution are poorly understood for a long time due to lack of available basement rocks our la icpms and sims zircon u pb dating of gneissic granitoids from the ordos block basement identified two distinct periods of granitic magmatism at 2 5 ma and 2 2 2 0 ga and two phases of metamorphisms at 1 95 ga and 1 85 ga respectively of which most zircons of 2 5 ga granitoids show positive hf t values ranging from 0 1 to 4 1 with a peak t dm of 2 7 ga minor zircons have negative hf t values from 3 8 to 0 02 and t hf c of 2 8 3 1 ga moreover the 3 40 ga inherited zircon and zircons with t hf c of 3 1 4 2 ga were found from 2 2 ga to 2 0 ga granitoids these suggest that there existed a neoarchean crust in the ordos block which underwent a major crustal growth at 2 7 ga and granitic magmatism at 2 5 ga highly consisting with 2 7 ga crustal growth and 2 5 ga magmatism resulted from juvenile crustal reworking in north china craton the zircons from 2 2 ga to 2 0 ga granitoids in ordos block basement display variable hf isotopic composition of positive to negative hf t values much similar to those of 2 2 2 0 ga granitoids related to continental margin arc setting in the trans north china orogen they were subsequently subjected to 1 95 and 1 85 ga metamorphisms which were widespread throughout the trans north china orogen based on the highly coherent zircon geochronology and hf isotopic composition between ordos block and other micro blocks of north china craton we propose that there is a neoarchean crust in ordos block which underwent a tectonic evolution similar to those in east block in later neoarchean and then experienced 2 2 2 0 ga granitic magmatism related to continental margin arc and 1 95 1 85 ga metamorphism resulted from collision between the east and west blocks along tnco

probabilistic mapping of earthquake induced submarine landslide susceptibility in the south west iberian margin abstract the sw iberian continental margin is well recognized as a tectonically active area where major canyons and mass wasting events are both present earthquake triggered submarine landslides may cause tsunami and result in catastrophic damage to bordering coastal areas in this setting submarine landslide susceptibility mapping represents a major step towards a regional risk mitigation strategy landslide susceptibility mapping in large offshore areas presents significant challenges as a result of the limited information on controlling variables large uncertainties in triggering mechanisms and limited geotechnical data in this study a geotechnical model based approach has been followed that narrows the range of controlling factors and within a probabilistic framework allows a systematic treatment of parameter uncertainties this model based analysis covers the whole sw iberian margin increasing by three orders of magnitude the areal extent of precedent offshore slope stability susceptibility studies this jump in spatial scale is facilitated by application of a systematic bayesian updating procedure to combine geotechnical information from global databases and that available from regional sites seismic shaking is estimated using an available regional database of seismogenic faults these tools are implemented within a gis to generate via montecarlo simulations probabilistic landslide susceptibility maps based on two different analytical seismic infinite slope stability models these models differ mainly in the form of their final results either as distributions of slope stability safety factors or as distributions of seismic triggered slope displacements receiving operator curves are used to assess the different landslide susceptibility predictions obtained against a comprehensive regional database of submarine landslides it turns out that the models analyzed correctly predict 92 and 82 of the mapped landslide subset chosen for validation for pseudo static and displacement based method respectively this suggests that within the limits of the currently available databases seismic events are the dominant factor at the origin of the submarine landslides mapped in the study area an advantage of the framework presented is that it can quickly incorporate new regional geotechnical information or better regional landslide databases as they become available

multivariate probability distribution for some intact rock properties a multivariate probability distribution model for nine parameters of intact rocks including unit weight porosity n l type schmidt hammer hardness rl shore scleroscope hardness sh bra

a microstructural investigation of osaka bay clay the impact of microfossils on its mechanical behaviour a recent microstructural investigation of osaka bay clay sediments has revealed the presence of abundant microfossils particularly in the marine layers which appear to influence directly the micr

petrology mineralogy and ore leaching of sandstone hosted uranium deposits in the ordos basin north china abstract the nalinggou daying uranium metallogenic belt is situated at the northern ordos basin china petrographical mineralogical and geochemical techniques were used to study the ore bearing sandstones and host rocks in the nalinggou daying uranium metallogenic belt the present study shows that uranium minerals i e coffinite pitchblende and brannerite are mostly disseminated around pyrite and detrital particles the ore bearing sandstones are enriched in organic matter with which this reductive environment influenced uranium leaching the carbonate concentration of the uranium ores is markedly higher than that of the host rocks and intense carbonatization occurs in the ore bearing sandstones in this case the usage of the classical in situ leach uranium mining technique by injecting h2so4 h2o2 solution produces calcium sulfate precipitate which can lead to blocking of the ore bearing strata for this reason laboratory and field uranium mining tests were conducted using co2 o2 in situ leaching technology and were demonstrated to be successful illustrating that this approach is technically feasible inhibiting ore bed blockage and increasing the amount of injected o2 are important for uranium leaching in this setting

stability of the kuroshio path with respect to glacial sea level lowering 1 we investigate the changes of the kuroshio current in the east china sea during the last glacial maximum based on numerical experiments using an ocean model and geochemical analyses of marine sediments our numerical experimental results indicate that there was little effect of sea level change on the path of the kuroshio during the glacial period geochemical proxy records of marine sediment cores recovered from inside and outside the okinawa trough ot show no significant difference in glacial sea surface temperature and planktonic foraminiferal 18o between the ot and the ryukyu forearc this indicates that the glacial sea surface temperature and salinity were almost the same inside and outside the ot hence during the glacial period kuroshio water most likely intruded into the ot and flowed along the shelf break until it drained out through the tokara strait

preconsolidation pressure from piezocone tests in marine clays piezocone penetration tests were carried out at five sites in marine clay with overconsolidation ratios ranging from 1 3 to 4 8 a simple model for the behaviour of these clays indicates that the effective vertical yield stress mobilized along the cone axis during penetration is equal to the difference between the actual induced total vertical stress in the soil and the total porewater pressure the actual induced total vertical stress can he derived from piezocone test data theoretically the ratio of the vertical yield stress inferred from piezocone results and the preconsolidation pressure should correlate with the overconsolidation ratio this hypothesis is supported by the field and laboratory investigations presented in this study des essais de penetration avec un piezocone ont ete effecte sur cinq sites d argile marine ayant des rapports de surconsolidation variant de 1 3 a 4 8 un modele simple de comportement de ces argiles indique que la contrainte effective verticale a l etat limite mobilisee d

competition between na2so4 and na sulfide in the upper crust of io the na atmosphere of io requires a na s o phase in the outer surface layers considering the various mechanisms for extraction of na to the surface the possible primary phases are na 2o na 2s x and na 2so 4 however regardless of the primary phases brought to the surface the shallow crustal recycling of material implied by the ongoing volcanism will tend to produce thermochemical equilibrium and cause all na to end up as na 2so 4 or na 2s x this hypothesis is investigated by relatively model independent thermodynamic calculations the major assumption is that material is statistically circulated to sufficiently high temperatures by burial that thermochemical equilibrium can be attained for a wide range of assumed crustal pt conditions na 2o will be converted to na 2so 4 during residence in the shallowest crustal regions dominated by liquid so 2 e g so 2 geysers or fumaroles or for any crustal regimes where so 2 and s are in comparable abundances na sulfides will be converted to na 2so 4 however in high temperature low pressure regimes with a low relative abundance of so 2 relative to s e g due to outgasing of so 2 na 2so 4 is converted to na sulfides such regimes could be relatively common on io e g associated with flows lava lakes or shallow intrusions consequently because of thermochemical equilibration in different crustal environments both na 2so 4 and na sulfides will coexist on the io surface

rare earth element distributions in uraninites implications for ore genesis abstract analysis of the rare earth element ree distributions in uraninites from a variety of hydrothermal mineral deposits indicates that wide variations are to be anticipated although crystal structure must exert a fundamental influence upon ree substitution in uraninite the present study suggests that other factors in particular hydrothermal fluid chemistry may be of equal importance total ree ree contents range from 15 000 ppm in uraninites from ultrametamorphic deposits to eu eu lree hree 0 08 1 10 they are interpreted to result from variations in the oxygen fugacity and the nature of the anionic complexes in the hydrothermal fluids responsible for ore transport additionally in uraniferous quartz pebble conglomerates the ree patterns of the detrital uraninites provide direct evidence regarding the provenance of these sedimentary u ores

uranium occurrence state in the tarangaole area of the ordos basin china implications for enrichment and mineralization abstract the zhiluo formation in the tarangaole area is a part of the dongsheng uranium ore field in the northeast ordos basin china uraniferous sandstones from this formation are examined in this study the type and mode of occurrence of uranium minerals is investigated in detail using an electron probe track etching energy spectrum backscattering a scanning electron microscope and an experiment for sequential extraction of uranium the results show that these uranium minerals are mainly composed of coffinite a small amount of pitchblende and some minerals containing titanium and uranium coffinite closely coexists with pyrite altered ilmenite or leucoxene charcoal biotite and clay minerals some coffinite occurs along mineral edges as burrs or fine columns it also occurs in biotite cleavage cracks with granulars in addition some uranium minerals are also observed within grains track etching shows that adsorbed uranium is either distributed at the edge of the debris or scattered among the grains the sequential extraction experiment indicates that the proportion of uranium minerals was significantly greater than that of the adsorbed uranium in the samples with the latter being largely present in pyrite and organic matter residual oxidizable and weak acid extractable uranium occur in the deposit scan mapping of uranium and titanium reveales that brannerite is almost nonexistent strongly altered ilmenite is considered a highly effective aggregating agent for uranium a large number of altered minerals including clays carbonaceous clastics biotite pyrite and ilmenite are widely developed in the uraniferous sandstone and play a significant role in the complex process of adsorption reduction precipitation of uranium the discovery of pitchblende and two types of coffinite high y and low y are discussed in context with their symbiotic relationship with the altered minerals it is suggested that the uraniferous sandstone underwent at least two stages of fluid activity

discussion on probabilistic transformation model for preconsolidation stress based on clay index properties eng geo 226 33 43 simple empirical models that use index properties as entry information for estimating the preconsolidation stress are of practical importance to geoengineers

interaction of two fluid systems in formation of sandstone type uranium deposits in ordos basin geochemical evidence and hydrodynamic modeling the ordos basin is one of the top oil gas and coal producers in china and is increasingly recognized as an important uranium mineralization province uranium deposits occur near the margin of the basin and are mainly hosted in sandstones of the jurassic zhiluo formation the ore bodies are associated with alterations that indicate a transition from oxidizing to reducing conditions accompanied by a change of color from red to green and grey previous studies of fluid inclusions in epigenetic minerals associated with uranium mineralization yielded homogenization temperatures from 60 to 180 indicating either deep burial or hydrothermal rather than early diagenetic environments the 13cv pdb dv smow and 18ov smow of the fluids related to mineralization inferred from the c h o isotopes of calcite and kaolinite associated with mineralization range from 14 0 to 2 7 130 to 94 and 9 1 to 8 8 respectively the c and h isotope compositions indicate that significant proportions of the carbon and hydrogen in the mineralizing fluids were derived from oxidation of hydrocarbons numerical modeling of fluid flow in the basin indicates that two fluid flow systems were developed in the jurassic and cretaceous time when the margins of the basin were relatively uplifted and the strata of the basin were gently inclined the upper flow system was driven by gravity in relation to topographic relief and the flow direction was downward and from basin margin towards basin center the lower flow system was driven by overpressures related to sediment compaction and the flow was upward and from basin center towards basin margins the authors hold that the location of uranium mineralization is associated with the mixing of the two fluid flow systems uranium was leached from the cretaceous and jurassic strata and carried by the descending meteoric fluids and was reduced from u6 to u4 by hydrocarbons carried by the ascending basinal fluids and precipitated at the interface of the two fluid systems the location of the interface between the two flow systems is dependent on the magnitude of the topographic relief at the end of the cretaceous sedimentation 65 ma the interface was located in the upper jurassic the main stratigraphic interval of uranium mineralization if the topographic relief was 350 m from the basin center to margin such an interface location can also be reached for a lower topographic relief at a later time due to gradual dissipation of the overpressures thus a combination of decreasing topographic relief and dissipation of overpressures after the cretaceous sedimentation was favorable for mineralization because the interface of the two fluid flow systems could be maintained in the same stratigraphic interval for a prolonged period of time

mineralogical and geochemical evidence for coupled bacterial uranium mineralization and hydrocarbon oxidation in the shashagetai deposit nw china unusual mineral structures have recently been found in a sandstone hosted roll type uranium deposit in the middle jurassic zhiluo formation in the shashagetai deposit the northern ordos basin nw china the structures possess a chemical composition and crystal structure characteristic of mineral coffinite usio4 1 x oh 4x which occurs as nanoparticles with size ranging from 5 to 25 nm these structures are interpreted to be fossilized microorganisms based on mineralogical biosignatures including morphology size occurrence of biogenic coffinite as nano crystals and biological elements such as p the intimate intergrowth of coffinite with secondary pyrite of bacterial origin as defined by low 34 s values and calcite cements with petroleum derived carbon supports its biogenic origin oil inclusions in the host sandstone are characterized by abundant n alkanes slightly increased pr nc17 and ph nc18 ratios significant amounts of demethylated hopanes and tricyclic terpanes and the existence of unresolved complex mixtures these characteristics are interpreted to be a result of mixing of an earlier heavily degraded oil with a later charged fresh oil subsequently the oils were slightly degraded these lines of evidence lead to the proposal that the reduction of sulfate and oxidization of petroleum are likely synchronous with reduction of hexavalent u vi to tetravalent u iv uranium by sulfate reducing bacteria srb the discovery of a natural association of microorganism like structures a uranium mineral and biodegraded petroleum has implications for uranium biomineralization and fossil fuel exploration

behaviour of a test excavation in soft champlain sea clay the field observations made during a sloped excavation in a soft sensitive clay are presented the test site is located in saint hilaire in a typical champlain sea clay deposit of 30 m depth the trench was 8 m deep and 60 60 m square and its slopes were at 45 34 27 and 18 to the horizontal the induced pore pressures and total lateral stresses have been recorded with vibrating wire instruments since the beginning of the excavation the steepest 45 slope completely failed 1 day after excavating and the 34 slope 2 weeks after the piezometer readings have shown that the groundwater regime was modified proportionally to the changes in total stresses these modifications took place within a time period of 5 months after which the heads became more or less constant the total stress cells indicated significant rotation of the principal axes at the toe of the slopes stability analyses using the lowest vane strength profile gave minimum factors of safety of 1 15 for the 45 slope and 1 23 for the

land subsidence due to groundwater drawdown in shanghai introduction shanghai is located on the deltaic deposit of the yangtze river as illustrated in fig 1 fig 2 shows the main geological strata the total thickness of the quaternary deposit is about 300 m shanghai geology office 1976 1979 excessive pumping of the groundwater caused compression of the quaternary deposit and subsidence in shanghai although several countermeasures including recharge of the groundwater have been adopted to mitigate the rate of subsidence up to the present the recorded cumulative subsidence has been 2 3 m in the central area of shanghai this subsidence has caused a lot of social problems the immediate problem is the increase in the possibility of flooding from 1981 to 1994 rainfall flooding occurred 22 times at a rate of almost twice per year liu 2001 the possibility of tidal flooding also increased from 1956 the height of the dike along the coast line was increased four times with the crest elevation rising from 5 m to 6 8 m other problems caused by the land subsidence are damage to the sewerage system road buildings and subway tunnels etc in shanghai the monitoring of land subsidence started in 1921 the history of land subsidence in the urban area of shanghai can be divided into two periods namely a rapid subsidence period 1921 1965 and a controlled period 1965 present zhang han 2002 however there has been a tendency for the subsidence rate to increase after 1990 in this paper the mechanism of land subsidence due to excessive pumping of groundwater is discussed first then the measured field data are presented and the relationship between groundwater pumping and land subsidence is discussed

biogenic and petroleum related ore forming processes in dongsheng uranium deposit nw china abstract sandstone hosted roll type u deposits has recently been found in the middle jurassic zhiluo formation in the dongsheng area north of the ordos basin in order to assess the origin of the uranium mineralization the host sandstone has been investigated with emphasis on 34s values of ore stage pyrite 13c of calcite fluid inclusion oil biomarkers x ray diffraction icp ms as well as studies by electron microprobe and scanning electron microscope the mineralization consists mainly of coffinite some of the coffinite is intimately intergrown with ore stage pyrite indicating co precipitation ore stage pyrite has 34s values from 34 to 17 suggesting the pyrite sulfur originated from bacterial sulfate reduction in the host sandstone calcite cement exhibits 13c values from 27 6 to 2 1 and fluid inclusion oils show evidence of biodegradation these lines of evidence indicate petroleum was likely oxidized by sulfate reducing bacteria srb and thus supplied a source of some of the carbon in the calcite microbial degradation of petroleum is partially supported by the low temperature diagenetic environment

geological and hydrogeological environment in shanghai with geohazards to construction and maintenance of infrastructures shanghai administrative region sar is located on the deltaic deposit of the yangtze river the bed rock under sar is generally buried in the depth of 200 m to 300 m except for several massifs where the bed rock is exposed to the ground surface the quaternary deposit in shanghai is soft sediment the variation of palaeoclimate influenced the sea level and resulted in a very complicated sedimentary environment the quaternary deposit in sar is composed of an alternated multi aquifer aquitard system maas the groundwater system is composed of one artesian aquifer and five confined aquifer layers with very high groundwater pressure head the maas was formed mainly within the warm geological era updated to 2 6 million years ago between two aquifers there is an aquitard which is composed of soft clayey soil formed mainly within the cold era the aquitards are composed of very soft clayey silt with very high compressibility and humus content the humus material was transformed into methane gas under a long term geological process with the development of economy the infrastructures were or are being constructed in the top shallow soft clayey deposit aquifer i and aquifer ii in sar the following geohazards occurred or possibly occur during the construction and maintenance of infrastructures i quicksand and piping hazards ii pumping induced hazards and recharge cutoff hazards iii long term settlement due to the seasonal fluctuation of groundwater level and iv geohazards of methane gas

modeling piezocone cone penetration cptu parameters of clays as a multivariate normal distribution this study examines the possibility of modeling piezocone cone penetration cptu cone tip resistance excessive pore pressure behind the cone undrained shear strength and overconsolidation ratio of lightly overconsolidated clays as a multivariate normal distribution this is part of a continuing study to develop a multivariate distribution that could be used to simulate common soil parameters at a clay site this study compiles a large database consisting of 535 data points in which the cptu parameters undrained shear strength and overconsolidation ratio are simultaneously measured in close proximity a multivariate normal distribution is then used to capture the correlations between soil parameters of interest and to derive useful equations for bayesian inference this constructed multivariate normal distribution and equations are further validated by another independent database consisting of 594 data points as well as by empirical equations proposed in literature the most useful outcome of this s

transformations and correlations among some clay parameters the global database this study compiles a large database of 10 clay parameters labeled as clay 10 7490 from 251 studies covering clay data from 30 regions or countries worldwide hence the range of data covered by

depositional and geotechnical properties of marine clays in lianyungang china the mineralogy geochemistry and geotechnical properties of clay samples in lianyungang china are presented the correlations of depositional history depositional environmental and geotechnical properties are discussed a series of x ray diffraction tests show that the principal clay minerals of the soil are illite smectite mixed layer mineral and illite the geochemistry investigation results indicate that the pore water of the lianyungang marine clay is dominant by sodium the ph of the soils varies in the range of 7 8 to 8 9 the depositional environment is oxidation condition the correlations of the geochemistry with the geotechnical properties are examined by the statistic analysis

statistical relationships between piezocone measurements and stress history of clays a database containing piezocone soundings from 205 clay sites around the world has been compiled for the calibration of an analytical cone penetration model and the development of statistical correlations yield stresses from laboratory oedometer tests were used as reference values for determining the stress history of natural clay deposits both simple and multiple regression analyses were performed on these data to evaluate correlative trends several simplified empirical relationships were identified for use in practice with the most reliable in relating preconsolidation stress to net cone tip resistance key words cone tip resistance overconsolidation ratio ocr preconsolidation pressure piezocone statistical relationships stress history

correlations between index tests and the properties of remoulded clays correlations have been developed which relate the compressibility undrained shear strength and permeability of remoulded clays to their atterberg limits and activity the relationships can be used to model a hydraulic fill such as fine grained dredged material or mine tailings prior to deposition they can also be used to estimate the engineering properties of normally consolidated natural clay such as marine sediments the correlations cover a wide range of plasticity index and liquidity index for a wide variety of clays it was found that the activity plays a major role in the compressibility and undrained shear strength and is thus also related to the sensitivity of clays the activity apparently does not affect the permeability but other factors remain to be investigated because compressibility undrained shear strength and permeability are interrelated it can be concluded that if one is known then the other two can be derived hence these three engineering properties are seen as different

selective crystallization and precipitation of authigenic pyrite during diagenesis in uranium reservoir sandbodies in ordos basin abstract the occurrence characteristics of authigenic pyrite during diagenesis in uranium reservoir sandbodies of zhiluo formation in ordos basin are investigated based on outcrop area investigations and drilled cores observations the pyrite is closely related to carbonaceous debris microscopically the host components for pyrite consist of carbonaceous debris clay minerals biotite the earlier pyrite and ilmenite by emphasizing on 34s values via la icp ms as well as observing through optical microscope and scanning electron microscope equipped with energy dispersive spectroscope three kinds of distribution pattern of pyrite are classified as i periphery ii infilling iii the combined form of the above two in situ micrometer scale sulfur isotope analyses of pyrite demonstrated that broad scale isotopes are heterogeneous from 52 5 to 35 4 of 34s and sulfur is derived from more than a single source significant differences of host components effects on authigenic pyrite formation are discussed the carbonaceous debris can supply the energy for the bacterial sulfate reduction process and the biotite can provide the source of iron for pyrite precipitation the ferrous ion can be adsorbed on the surface of the clay minerals meanwhile the authigenic pyrite is distributed in or around the earlier pyrite and ilmenite by the indirect adsorption of ferrous ion and the ilmenite may also provide the source of iron futhermore the uranium minerals are mainly associated with the authigenic pyrite relevant to carbonaceous debris and clay minerals which indicates there exists constraints of authigenic pyrite during diagenesis on the uranium mineralization

origin of the carbonaceous debris and its implication for mineralization within the qianjiadian uranium deposit southern songliao basin abstract appearance and coal petrology of the carbonaceous debris cd from the qianjiadian uranium deposit southern songliao basin are illustrated in order to reveal the relationship between the cd and uranium mineralization response of the cd and uranium mineralization to diabase dikes and origin of the cd three types of cd have been identified in the yaojia formation cd serving as trapped sediments cd serving as laminae of cross bedding and cd occurring in lumpy sandstones with an average content of 91 2 in the cd organic macerals are primarily composed of homoeollinite desmocollinite and inertinite inorganic macerals of the cd mainly include pyrite with an average content of 8 8 average contents of the desmocollinite inertinite and pyrite from the cd in the ore bearing section are higher than that in the non ore bearing section respectively the study demonstrates that the cd rich in inertinite and desmocollinite facilitates uranium mineralization uranium is frequently adsorbed in the desmocollinite and inertinite and coffinite is embedded in the inertinite inferring that roles of the cd in uranium mineralization are both adsorption and reduction vitrinite reflectance vr of the cd ranges from 0 24 to 0 513 with an average value of 0 335 the vr of the cd in the ore bearing section is generally larger than that in the non ore bearing section uranium mineralization and enlargement of the vr are both attributed to the diabase dikes the cd originated from the late cretaceous wildfire related woody plants and it has been transported into fluvial channels and preserved in sandstones

piezocone testing in underconsolidated clay this paper describes the results of piezocone testing that was carried out in underconsolidated soft marine clay in osaka bay the obtained profiles of the tip resistance and the pore water pressure were quite different from those for clay strata of normally consolidated state it was apparent that a different approach is needed to interpret the test results for underconsolidated clay the dissipation tests with the piezocone were performed at different elevations and indicated the excess pore water pressures remaining in the stratum the depth profile of excess pore pressure of underconsolidated clay is of special importance to the understanding of the degree of consolidation of the stratum an effort was made in this paper to assess the excess pore pressures remaining in the clay based on the piezocone data obtained during penetration an examination was made of available piezocone data of similar marine clays of both normally consolidated and underconsolidated states based on this a method was propos

paleogeography reconstruction of a multi stage modified intra cratonic basin a case study from the jurassic ordos basin western north china craton abstract post depositional modification is commonly found in sedimentary basins particularly in the eastern tethys tectonic domain and is related to special geological settings and evolution processes of the region the chinese continent is composed of numerous small scale blocks that underwent intensive tectonic movements paleogeography reconstruction for a modified basin is fundamental for objectively understanding the basin dynamics and exploration of hydrocarbon sandstone type uranium deposits and other mineral resources as a large scale intra cratonic depression basin in the western part of the north china craton ncc the mesozoic ordos basin underwent multi stage modification as a result only the western part was preserved in this study the paleogeography in bathonian oxfordian ages of the jurassic was reconstructed via integrated approaches including stratigraphic correlation sedimentary facies analysis provenance analysis and fission track analysis the original sedimentary boundary of the ordos basin during this period is approximately outlined we determine that the northern and southern borders reach the cenozoic hetao basin and the cenozoic weihe basin respectively and that the eastern northwestern and southwestern borders lie to the west of taihang mountain at the langshan bayanhot basin kexueshan and to the west of liupan mountain respectively the original sedimentary extent of the ordos basin was almost twice that of the present day residual basin the evolution of this basin in the mesozoic recorded the evolution and destruction processes of the ncc the ncc shows that n s and w e trending compressional setting occurred during the triassic and the jurassic respectively the interactive activities of adjacent tectonic domains played a critical role in subsidence dynamics for the intra cratonic ordos basin this study provides further insights for exploration of hydrocarbon and sandstone type uranium deposits in the ordos basin

excess pore pressure resulting from methane hydrate dissociation in marine sediments a theoretical approach 1 this study quantifies the excess pore pressure resulting from gas hydrate dissociation in marine sediments the excess pore pressure in confined pore spaces can be up to several tens of megapascals due to the tendency for volume expansion associated with gas hydrate dissociation on the other hand the magnitude of excess pore pressure in well connected sediment pores is generally smaller depending primarily on the hydrate dissociation rate and the sediment permeability volume expansion due to gas hydrate dissociation in well connected pore spaces is related via darcy s law to an increase in pore pressure and its gradient in sediment which drives an additional upward fluid flow through the sediment layer overlying the gas hydrate dissociation area the magnitude of this excess pore pressure is found to be proportional to the rate of gas hydrate dissociation and the depth below seafloor and inversely proportional to sediment permeability and the depth below sea level the excess pore pressure is the greatest at low initial pressures and decreases rapidly with increasing initial pressure excess pore pressure may be the result of gas hydrate dissociation due to continuous sedimentation tectonic uplift sea level fall heating or inhibitor injection the excess pore pressure is found to be potentially able 1 to facilitate or trigger submarine landslides in shallow water environments 2 to result in the formation of vertical columns of focused fluid flow and gas migration and 3 to cause the failure of a sediment layer confined by low permeability barriers in relatively deep water environments

biogenic and nonbiogenic ore forming processes in the south texas uranium district evidence from the panna maria deposit geochemical and petrographic studies of core samples from the panna maria uranium deposit a roll type orebody in the eocene jackson group in karnes county texas yield important information on the origin of the deposit organic carbon content averages about 0 42 weight percent in reduced rock and correlates postively with sulfur content pyrite is the dominant iron disulfide fes 2 mineral in most of the ore zone and throughout a surrounding zone of reduced barren ground and it is commonly associated with organic debris marcasite is sparse except in ore adjacent to the altered tongue in one core and locally in mineralized lignite sulfur isotopic compositions delta 34 s of fes 2 minerals range broadly from 1 to 34 per mil the lightest delta 34 s values less than 20 per mil were measured in samples from mineralized lignite and from the nose of the ore roll petrographic and geochemical characteristics of the panna maria deposit contrast greatly with those of three other south texas roll type uranium deposits the benavides felder and lamprecht deposits which are devoid of organic carbon and which contain more sulfide than does the panna maria these three deposits are characterized by abundant isotopically light ore stage marcasite and by isotopically heavy preore in the benavides or postore in the felder and lamprecht pyrite we have concluded previously that sulfide bearing fault leaked solutions from underlying hydrocarbon accumulations were important in the formation of the benavides felder and lamprecht deposits although the panna maria deposit shows an apparent alignment along a fault zone and although underlying formations in the karnes county area contain sour gas delta 34 s asymp 14 per mil and produce oil the deposit lacks characteristics indicating that its formation or preservation involved extrinsically derived reductants such as fault leaked aqueous sulfide mineralization of the panna maria rather appears to have been controlled by intrinsically derived reductants related either directly or indirectly to the presence of organic matter

comparison of field consolidation with laboratory and in situ tests settlement calculations for an earth embankment resting on soft compressible fraser river delta sediments were made from laboratory consolidation tests and in situ tests using a piezocone and a flat dilatometer the calculated values were compared with measured settlements there was rather good agreement among the three methods of calculation but the actual settlement was about 60 greater than the average calculated value calculated rates of settlement are also compared with observed values key words consolidation settlements piezocone dilatometer in situ tests constrained modulus pore water pressure settlement rate

paleo environmental constraints on uranium mineralization in the ordos basin evidence from the color zoning of u bearing rock series abstract color zoning of strata of mesozoic continental basins in north china is closely correlated with the sedimentary environments of sandstone type uranium deposits systematic research has been conducted on the colors of u bearing rock series within the ordos basin by using data of several ten thousands of drill holes from coal and oil fields taking an ore cluster as the unit well tie sections of deposit areas were compiled to analyze the vertical and lateral spatial variations in different color zones of rocks taking the basin as the unit two typical well tie sections in the central northern basin were compiled in order to summarize the rock color zoning laws of u bearing rock series within ore clusters and the entire basin lithogeochemical characteristics of different color zones in deposit areas and ore barren areas were studied especially variations in trace elements in different color zones and the paleo sedimentary environments they reflect were discussed within the ordos basin from the basin margin to the center and from the u ore clusters to the ore barren areas colors of the zhiluo formation u bearing rock series generally display vertical zoning i e from up downwards red green gray grayish black and show no lateral zoning characteristics u ore beds mostly occur in the lower part of the green zone and the upper part of the gray zone this conclusion differs greatly from the understanding on rock color zoning related to classic interlayer oxidation zone metallogenic theory hence a correct understanding on color zoning of u bearing rock series within the ordos basin is of great significance not only to u mineralization exploration but also to research on sandstone type u mineralization theory

preconsolidation pressure of champlain clays part i in situ determination the preconsolidation pressure of sensitive clays is an important parameter for the design of foundations on these soils which are widespread in eastern canada and above all in the st lawrence and ottawa valleys where champlain clays are found a research study was initiated in 1979 to assess whether the preconsolidation pressure values derived from laboratory tests are representative of the preconsolidation pressure effectively mobilized in situ several existing structures were investigated and five of them are presented with performance records taken during and after construction together with data obtained from recent soil investigations for each case study the in situ preconsolidation pressure is determined from the analysis of settlement and or pore pressure records the preconsolidation pressure values derived from conventional oedometer tests on good quality undisturbed samples are compared with the in situ values and a simple correlation taking into account the overconsolidation ratio of the cla

evidence of uranium biomineralization in sandstone hosted roll front uranium deposits northwestern china we show evidence that the primary uranium minerals uraninite and coffinite from high grade ore samples u3o8 0 3 in the wuyiyi wuyier and wuyisan sandstone hosted roll front uranium deposits xinjiang northwestern china were biogenically precipitated and psuedomorphically replace fungi and bacteria uranium vi which was the sole electron acceptor was likely to have been enzymically reduced post mortem accumulation of uranium may have also occurred through physio chemical interaction between uranium and negatively charged cellular sites and inorganic adsorption or precipitation reactions these results suggest that microorganisms may have played a key role in formation of the sandstone or roll type uranium deposits which are among the most economically significant uranium deposits in the world

occurrence of analcime in the middle jurassic coal from the dongsheng coalfield northeastern ordos basin china abstract this paper describes the occurrence of significant authigenic analcime naalsi2o6 h2o in the middle jurassic coal from the northeastern ordos basin and discusses its origin twelve coal samples from borehole zk31 19 in the dongsheng coalfield were collected and analyzed the coals are characterized by a low medium ash yield high volatile matter and low sulfur contents the major element oxides in the studied coals are mostly at similar or much lower concentrations compared to the averages for chinese coals similarly most trace elements are depleted or in concentrations close to the respective averages for world low rank coals based on seredin dai s classification the rey rare earth elements and y in the coal mainly display n and h type distribution patterns with no ce and eu anomalies coal sample zk31 19 12 from the lower zhiluo formation contains analcime up to 23 wt with a high na2o concentration of 1 23 both on a whole coal basis the analcime occurs as lath as subhedral granular crystals in fissures or pores and as anhedral crystals in the organic matrix furthermore significant analcime has also been observed by sem in coal from the upper yan an formation sample zk31 19 10 which mainly occurrs as anhedral crystals no evidence of analcime forming from precursors of volcaniclastic material alkali zeolites or other silicates was detected therefore it is deduced that the analcime in the studied coals formed by authigenic precipitation the na2o content in the studied coal seams displays a vertical variation different from that of the ash yield ad and those of the detrital dominated elements such as sio2 al2o3 tio2 zr nb and th indicating a different origin of na compared with other detrital materials of terrigenous origin combined with the evidence of the obvious na peak in authigenic amorphous material and gypsum mineral by sem it can be inferred that the source of na may derive from the fluids the paleoclimatic change from subtropical warm and humid to semi arid and arid hot during the deposition period of the yan an to the zhiluo formation may provide favorable conditions for analcime authigenesis leading to its abundant precipitation in the lower zhiluo formation and its limited occurrence in the upper yan an formation such paleoclimatic change is also significant for the u mineralization in the lower zhiluo formation

evolution and origins of pyrite in sandstone type uranium deposits northern ordos basin north central china based on micromorphological and compositional analysis abstract pyrite is an abundant mineral throughout the uranium bearing middle jurassic zhiluo formation northern ordos basin three different morphologies of pyrite are identified framboidal euhedral and cement based on textural and geochemical results from optical microscopy secondary electron se and back scattered electron bse imaging energy dispersive spectroscopy eds electron probe microanalysis epma and laser ablation multi collector inductively coupled plasma mass spectrometry la mc icpms three evolutionary models are proposed as follows aggregation of framboids to form polyframboids as a result of the bacterial sulfate reduction bsr processes the formation of cement pyrite under the addition of thermal fluids with numerous framboids and microcrystals inside and euhedral pyrite evolving from framboids the analytical data show that there is a minor increase in major and trace element contents in transformed pyrite and each pyrite morphology has a distinct sulfur isotopic composition 9 9 to 8 0 for framboids 19 1 to 14 2 for polyframboids 18 7 to 20 3 for euhedral pyrite and 15 7 to 21 2 for cement pyrite this indicates that the sulfur was derived from more than one source compared with the original framboids the association between uranium and different types of pyrite indicates that different processes e g bsr and thermogenic sulfate reduction tsr were involved in the precipitation of uranium mineralization and are important to the formation of the precipitation of uranium in the zhiluo formation northern ordos basin

effect of quaternary transgression and regression on the engineering properties of shanghai soft clays abstract the engineering properties of marine clays are closely related to its depositional environment however the correlation between the chemical properties and depositional environment and their effect on engineering properties of upper shanghai marine clay are still pending the sedimentary processes of upper shanghai marine clays from the quaternary transgression the correlation between the chemical properties and its depositional history are investigated in this study based on a series of laboratory experiments the distribution of chemical indicators e g ph value oxidation reduction potential and salt content with depth showed that the depositional environment directly affected the chemical properties of the soil layer the correlation of salt content with sensitivity liquid limit and liquidity index in upper shanghai layers represents a unique two stage distribution with the boundary at the bottom of the layer 4 clay the two stage distribution is caused by the quaternary transgression and regression which is confirmed to have different effects on the salt content sensitivity liquid limit and liquidity index the quantitative approaches used to evaluate the correlation between depositional environment chemical and mechanical properties can provide valuable references for investigating the engineering properties of soft clays

experimental study on the deterioration and natural remediation of the ariake sea tidal mud caused by the sea laver treatment acid practice and the upward seepage of pore water liquid this study presents a laboratory study of the following two aspects 1 the influence of sea laver treatment acid on the geoenvironmental properties of ariake sea tidal mud and 2 the natural remediation effect on the sea laver treatment acid contaminated ariake sea tidal mud caused by the upward seepage of pore water liquid in the mud firstly the mechanisms of the transport of sea laver treatment acid in the ariake sea tidal mud and the generation mechanisms of the upward seepage flow in the ariake sea tidal mud are discussed secondly a series of one dimensional laboratory infiltration tests were carried out to investigate the deterioration of the ariake sea tidal mud caused by the sea laver acid treatment practice test results reveal that the acid treatment practice caused considerable change in the geochemical properties of the mud in terms of increase in sulfide content and decrease in ph value after the treatment by the sea laver treatment acid the sulfide content of the mud even exceeded the safe limit value for the benthos which represents undesirable living condition for benthos thirdly series of laboratory fresh seawater infiltration tests for the deteriorated iida site mud were conducted to illustrate this natural remediation efficiency it is found that with the infiltration of the fresh seawater the sulfide content of the iida site mud was considerably reduced and ph value increased to an acceptable range for benthos living in the tidal flat mud with the increase in the infiltration time and the hydraulic gradient the remediation efficiency could be increased

rare earth elements and hydrothermal ore formation processes abstract the geochemical behaviour of ree is influenced by nearly all important hydrothermal ore formation processes including fluid rock interactions fluid precipitations adsorption and scavenging onto particles and changes in fluid temperature pressure ph eh alkalinity and ligand concentration destabilization of ree complexes in response to these physicochemical changes and possible chemical crystallographic controls determine the concentration and distribution of ree within hydrothermal minerals mineraloids and amorphous phases alteration assemblages of intrusive related mineralisations may exhibit a wide range of ree distributions and ree fractionation trends the ree distribution within these hydrothermally altered lithologies will depend on the ree concentration in the rock and the fluid the partitioning behaviour of the ree between the rock phases and the fluid and the types of alteration reactions which take place reactive rocks such as carbonate rich lithologies of skarn deposits may gain or loose significant amounts of ree during fluid rock interactions ree geochemical investigations combined with fluid inclusion and stable isotope studies may point to the origin of alteration products and the source s of ore fluids ancient massive sulphide ores commonly exhibit anomalous eu concentrations similar to many recent submarine hydrothermal precipitates the recognition of hydrothermal fluid seawater sedimentary or volcanically derived ree distributions within ores chemical sediments and hydrothermally altered lithologies may help to constrain genetic modelling of massive sulphide deposits care should be taken with the interpretation of ree distributions from metamorphosed hydrothermal ore deposits becase metamorphic and diagenetic alteration reactions may change the ree distributions mobility of ree may occur during diagenesis of carbonate rich rocks and during the development of shear zones and migmatites in contrast very large fluid rock ratios are necessary to cause significant changes in ree patterns of silicate rich rocks during diagenesis and regional metamorphism

contemporary kinematics of the ordos block north china and its adjacent rift systems constrained by dense gps observations abstract the detailed kinematic pattern of the ordos block north china and its surrounding rift systems remains uncertain mainly due to the low signal to noise ratio of the global positioning system gps velocity data and the lack of gps stations in this region in this study we have obtained a new and dense velocity field by processing gps data primarily collected from the crustal motion observation network of china and from other gps networks between 1998 and 2014 the gps velocities within the ordos block can be interpreted as counterclockwise rotation of the block about the euler pole with respect to the eurasia plate velocity profiles across the graben bounding faults show relatively rapid right lateral strike slip motion along the yinchuan graben with a rate of 0 8 2 6 mm a from north to south in addition a right lateral slip rate of 1 1 1 6 mm a is estimated along the central segment of the shanxi rift however strike slip motion is not detected along the northern and southern margins of the ordos block conversely significant extension motion is detected across the northwestern corner of the block with a value of 1 6 mm a and along the northern segment of the shanxi rift where an extensional rate of 1 3 1 7 mm a is measured both the daihai and datong basins are experiencing crustal extension on the southwestern margin of the block deformation across the compressional zone of the liupanshan range is subtle however the far field shorting rate is as high as 3 0 mm a implying that this region is experiencing ongoing compression the results reveal that present day fault slip occurs mainly along the block bounding faults with the exception of faults along the northern and southern margins of the block these results provide new insights into the nature of tectonic deformation around the ordos block and are useful for assessing the seismic activity in this region