the hydrogeological and contaminant transport properties of fractured champlain sea clay in eastern ontario part 1 hydrogeological properties hydrogeological and geochemical investigations were conducted on four fractured champlain sea clay deposits in eastern ontario the results from water level monitoring maximum seasonal variations and hydraulic head profiles revealed a hydraulically active fractured zone existing at all four sites the depth of this fractured zone varies from site to site ranging from 3 2 to 6 0 m slug test analysis indicated that bulk hydraulic conductivity values in the upper fractured zone range from 1 8 10 8 to 2 0 10 5 m s in contrast the measured hydraulic conductivity values from the deepest piezometers range from 8 2 10 10 to 1 4 10 9 m s the geochemical analysis indicated the presence of three hydrochemical facies a shallow active facies a deep inactive facies and an intermediate transition facies the presence of tritiated groundwater well below the groundwater table indicates that the upper fractured zone at all four sites is hydraulically active key words fractures champlain sea clay

geological geochemical and mineralogical characteristics of the mandan and deh now bauxite deposits zagros fold belt iran the mandan and deh now bauxite deposits are located 40 km northeast of the dehdasht city in the zagros simply fold belt these deposits occur in eroded major nw se trending anticlines and occupy karst cavities near or at the boundary between the sarvak and ilam formations local uplifts at the end of the cenomanian and the mid turonian caused erosion and karstification of the sarvak formation these unconformities in the upper cretaceous favoured the formation and enrichment of bauxite deposits in the zagros fold belt the bauxite sequence in the mandan deposit consists of white gray black pisolitic red and yellow bauxites this sequence was repeated in the deh now area but without gray and black bauxites the present mineralogical studies of the sarvak formation and the mandan and deh now bauxite deposits indicate oxidizing to reducing conditions during the upper cretaceous in the zagros fold belt which had a significant effect on the compositions of the bauxites at least two phases of bauxitization can be distinguished in the study area i an oxidizing phase represented by boehmite diaspore hematite and kaolinite and ii a reducing phase represented by pyrite and chlorite geochemical data show that trace elements like zr hf nb ta th and u were enriched during bauxitization the bauxite deposits and carbonate rocks show similar ree patterns namely they are enriched in rees although the lrees are more enriched than the hrees mass change calculations demonstrate that mg mn ca k and p2o5 were leached out of the weathered system whereas al fe and si become concentrated in the residual system this study indicates that the mandan and deh now deposits are karst type bauxites formed by karstification and weathering of the sarvak formation

quick clay a case study of chemical perspective in southwest sweden quick clay a soil that changes from normal firm ground to a liquid mass when it is disturbed has been involved in most of the large and serious clay slides in sweden norway and canada the location time of occurrence and size of quick clay slides are difficult to predict and large slides may cause great devastation some geochemical studies of swedish quick clay were done in the 1960s and early 1970s but no systematic studies of the interrelationships of pore water chemistry mineralogy geotechnical properties and other parameters on quick clays in sweden have been published such studies are of national and general interest because of the many combinations of rock flour source areas and sedimentation conditions that occurred across central sweden and into the baltic sea area during deglaciation in this study geotechnical properties related to the in situ chemistry at one quick clay site were extensively studied and spot sampling was conducted at two other locations in southwest sweden in this area the clay minerals mainly are non expanding phyllosilicate minerals illite and primary minerals quartz feldspar which is consistent with previous studies of quick clay mineralogy extensive leaching has occurred at all three locations at the extensively studied site surte the lowest salinity was found at the greatest depth inferring that the leaching by fresh water was accomplished by water movement upward and laterally through the sediment from the underlying bedrock this is consistent with the local setting where bedrock hills rise sharply to over 100 m above the marine sediment surface an artesian pressure would also be anticipated at this location there is a correlation negative between sensitivity and salinity but there is an indication that the maximum salinity or electrical conductivity consistent with the quick clay behaviour is higher than reported elsewhere however for high sensitivities the salinity is about the same as reported elsewhere in the deepest part of the borehole there is a higher content of fe and al in the pore water indicating reduced state further work is needed to confirm the difference in salinity and to investigate the possible interplay of salinity and potential dispersing agents such as the role of anoxic conditions in this region further work is especially needed in the locations where the sediment accumulation occurred under lower salinity conditions at all three locations high remoulded shear strength and low sensitivity have been seen near the surface together with a decrease in pore water cation concentrations

a physical explanation of the relation between flank uplifts and the breakup unconformity at rifted continental margins rift flank uplifts and the breakup or postrift unconformity are characteristic features of many rifted passive or atlantic type continental margins but are not predicted as primary features of simple lithospheric stretching models the explanations that have been proposed for their origin remain controversial either because they call upon special circumstances or because they are difficult to test plane strain finite element models are used in this paper to explore the dynamics of lithospheric necking during rifting and rupture the results agree with the conceptual interpretation that uplift of the rift boundaries to form flank mountains and uplift of the basin responsible for the breakup unconformity are related consequences of regional isostatic compensation of mass that is redistributed during the necking and rupture phases although the amplitudes of these uplifts depend on the model parameter values the relations between and relative signs of these two effects appear to be fundamental the explanation we propose may have been missed in recent studies because there has been a tendency to concentrate on kinematic stretching models which assume local isostatic equilibrium through out the rifting process such an approach is predicated on the assumption that the lithosphere has an insignificant strength or flexural rigidity during extension which is not true if our explanation is correct

mercury intrusion and permeability of louiseville clay several theories have been proposed to correlate the permeability hydraulic conductivity with the pore size distribution of soils and it seemed interesting to determine if these theories could be applied to natural clays for this purpose permeability and mercury intrusion porosimetry tests were performed on a champlain sea clay for both intact and remoulded conditions after compression of the specimens to strains varying from 0 to 42 the results show that for either intact or remoulded soil conditions there is a relationship between the pore size parameters and the permeability of the clay however there is no unique relationship for both intact and remoulded clays and for the silt and clay considered in previous studies consequently mercury intrusion porosimetry alone cannot be usepto evaluate the permeability of soils in general plusieurs thkories ont ctc proposces pour corrcler la permiabilite conductivitk hydraulique avec la distribution des grosseurs de pore des sols et il a semblc intiressant de verifier si ces theories pourraient 2tre appliquees aux argiles naturelles a cette fin des essais de permcabilitc et de porosimctrie a intrusion de mercure okt ctc rcaliscs sur l argile de la mer champlain dans des conditions tant intactes que remanikes apris la compression des specimens a des dcformations variant de 0 a 42 les rcsultats demontrent que pour des conditions soit intactes ou remanices il existe une relation entre les paramitres de grosseur de pore et la permcabilitc de l argile cependant il n existe pas de relation unique pour les argiles tant intactes que remanices et pour le limon et l argile ctudics antkrieurement en conscquence la porosimctrie a intrusion de mercure ne peut pas a elle seule tre utilisce pour cvaluer la permcabilitc des sols en general mots clds permcabilitc argile porosimctrie a intrusion de mercure structure traduit par la rcdaction

karst bauxite deposits in the zagros mountain belt iran more than 190 occurrences of bauxitic lateritic deposits were investigated in seven areas within the zagros simply folded mountain belt in southwestern of iran the bauxitic horizons are situated in eroded major nw se trending anticlines and occur in karst cavities near or at the boundary between the sarvak and ilam formations uplift in the cenomanian turanian period had exposed the sarvak limestone to karst weathering and during a period of unconformity layers of ferruginous argillaceous limestone debris developed and accumulated on its surface the ferruginous argillaceous debris was partly converted to bauxite folding and faulting in oligocene miocene time with ensuing erosion exposed the bauxitic horizons on the limbs and cores of anticlines the karst bauxite deposits are probably of authigenic origin as evidenced by their lithologic associations textural and mineralogy

the pleistocene of schoningen germany a complex tunnel valley fill revealed from 3d subsurface modelling and shear wave seismics abstract the pleistocene deposits of schoningen represent an outstanding geological and archaeological archive where an up to 45 m thick middle to late pleistocene succession has been preserved and unique artefacts from the lower palaeolithic have been discovered the preservation of such a thick and complete glacial interglacial succession is very rare in the geological record and requires a specific depositional setting we will present a new depositional model for the pleistocene succession of schoningen integrating outcrop data borehole data and high resolution shear wave seismics a total of four outcrop sections and 744 borehole logs were examined to document the complex facies architecture all collected sedimentological and geophysical data sets were integrated into a high resolution 3d geological model gocad for reconstructing the spatial distribution of facies associations and the large scale depositional architecture the spatial distribution of the artefacts will be discussed with respect to the depositional environment the elsterian and holsteinian deposits are restricted to a nnw sse trending elongated trough which is deeply incised into unconsolidated lignite bearing palaeogene deposits the geometry of this erosional structure points to a tunnel valley origin that was incised below the elsterian ice sheet the basal tunnel valley fill consists of cross stratified pebbly sand and gravel overlain by till after deglaciation the tunnel valley remained underfilled and acted as a depocentre for interglacial deposition during the subsequent holsteinian interglacial mis 9 a lake formed within this depocentre and lacustrine sediments accumulated this interglacial succession consists of peat organic rich silt and fine grained sand interpreted as lake bottom and deltaic sediments fed by surface run off shed from the elm ridge the lacustrine deposition was controlled by repeated lake level fluctuations in the range of 1 6 m leading to the formation of laterally stacked delta systems these lake level changes were probably triggered by climate causing variations of precipitation and surface run off during the late saalian glaciation the remnant tunnel valley was completely filled with meltwater deposits the sedimentary facies and depositional architecture point to a shallow water delta subsequently the meltwater deposits were overlain by till the deposition of the middle pleistocene sediments within an elsterian tunnel valley explains the unique preservation of the sedimentary succession of schoningen the long lived interglacial lake provided an attractive site for animals and early humans ambushing them artefacts mainly became embedded on the delta plain which rapidly was transgressed during lake level rise and artefacts were thus preserved

geometry of propagating continental rifts reconstruction of past plate configurations through palinspastic restoration of continental margins1 4 requires a detailed knowledge of the geometries of horizontal continental extension extension is often restricted to discrete linear zones termed rifts5 6 and rift models that invoke propagating vertical dykes and cracks7 10 are useful for assessing the relative significance and timing of uplift subsidence and extension in the tectonic evolution of rift basins however many models do not adequately account for the observed asymmetry of rifts i describe here the general three dimensional character of young and aborted continental rifts which can be used to derive a structural model for the propagation of rifts in continental lithosphere the rifts become asymmetric as a consequence of the role played by low angle normal faults in the overall rift geometry

seismic detection and evaluation of delta and turbidite sequences their application to exploration for the subtle trap energy conditions at the seaward edge of deltas allow their division into fluvial dominated wave dominated and tide dominated deltas each kind of delta has a distinct framework orientation and depositional pattern which results in a characteristic seismic reflection pattern fluvial dominated deltas are characterized by clinoform seismic reflection patterns which include oblique tangential complex oblique tangential sigmoid and complex sigmoid oblique seismic facies analysis can be used to define those facies which should contain sand wave dominated deltas are characterized by shingled seismic reflection patterns seismic facies analysis of this delta is not effective in identifying those facies which should be sand prone shingled reflections may be used in determining the possible location and depositional attitude of strandline sands tide dominated deltas have not yet been identified using seismic stratigraphic methods and therefore are not covered in this paper turbidite fans are sequences of sands and shales deposited in conjunction with and basinward of deltas or submarine canyons turbidite sands can be classified generally into channel and suprafan sands certain seismic events and reflection patterns occurring in various combinations may suggest the presence of turbidites these indicators include troughs submarine canyons mounds prograded fluvial dominated delta reflection patterns which vary in thickness and onlap offlap patterns on depositional slopes regional studies provide the best means of identifying and mapping depositional sequences examples from the north sea gulf coast and sacramento valley illustrate the geologic and geophysical expression of delta and turbidite sequences and their interrelations

trace and rare earth elements constraints on the sources of the yunfeng paleo karstic bauxite deposit in the xiuwen qingzhen area guizhou china abstract a number of carboniferous paleo karstic bauxite deposits occur in the xiuwen qingzhen area central guizhou province which constitute an important part of the central guizhou southern chongqing bauxite belt in southwestern china these deposits consist of lenticular and stratiform orebodies hosted in the lower carboniferous jiujialu formation which lies unconformably above carbonate rocks mainly dolomite of the middle and upper cambrian loushanguan group shilengshui formation and lower cambrian qingxudong formation although it is generally agreed that the bauxite resulted from weathering of cambrian rocks below the unconformity it remains unclear whether the carbonates alone can provide sufficient material for the formation of the deposits in this study we examined the mineralogy and major trace and rare earth elements geochemistry of bauxite and bauxitic clays from the yunfeng deposit in the xiuwen qingzhen area and compared them to previously published data of a paleo weathering profile consisting of loushanguan dolomite underlying the sub carboniferous unconformity and the black rock sequence of the lower cambrian niutitang formation in order to evaluate the sources of the bauxite the bauxite ores are composed of diaspore as the main ore mineral along with small amounts of pyrite arsenopyrite galena stibnite xenotime and uranium bearing minerals and are characterized by high contents of uranium and phosphorus chondrite normalized ree patterns and various bivariant diagrams commonly used to study the provenance of bauxite including eu eu vs tio2 al2o3 eu eu vs sm nd tio2 vs al2o3 tio2 th th vs ta th vs nb and nb vs ta suggest that the loushanguan dolomite and the niutitang black rock sequence are both potential source rocks however a comparison in u and th contents between the paleo weathering profile of the loushanguan dolomite and the bauxite samples suggests that the dolomite alone cannot provide the materials for the bauxite ores instead the black rock sequence may have contributed most of the ore forming materials which are mainly transported from source regions where the niutitang formation was exposed weathered and eroded therefore the yunfeng bauxite deposit is of mixed autochthonous and allochthonous origin

mineralogy chemistry and physical properties interrelationships of some sensitive clays from eastern canada this paper describes the use of quantitative mineralogy and specific surface area in interpreting the index properties of clayey soils from nine sites in eastern canada samples representative of t

mineralogical control and characteristics of rare earth elements occurrence in carboniferous bauxites from western henan province north china a xrd sem eds and la icp ms analysis abstract high concentrations of rare earth elements ree are found in the bauxite deposits in the songqi area of henan province north china however no studies have been carried out on the occurrences of ree in these bauxite ores in this study we explored the ree occurrence and their possible enrichment mechanism in the songqi bauxite deposits using petrographic observation x ray diffraction xrd scanning electron microscope with energy dispersive spectroscopy sem eds and la icp ms techniques the major aluminum rich ore mineral in the songqi bauxite deposits is diaspore and other coexisting minerals include clay mineral aggregates with minor amounts of hematite pyrite anatase and zircon the bauxite ores are rich in ree and also some other critical metals li zr nb and ga most of the ree are adsorbed in the form of ions on the surface of clay minerals and diaspore and some heavy rare earth elements hree exist in the form of xenotime the sem eds and la icp ms analyses show that ree is closely related to the content of p and therefore it is possible that other dispersed and minor p bearing rare earth minerals may occur in the bauxite deposits except for the possible co adsorption of p and ree in the clays and diaspore

influence of porefluid salinity on instability of sensitive marine clays a new approach to an old problem the geographic association between earthflow occurrence sensitivity of the sediment and salinity of the interstitial fluid has been examined in an area of exposed marine champlain sea deposits in the lachute region northwest of montreal quebec mapping of earth resistivity as a means of calculating porefluid salinity revealed that areas of large earthflows 20 ha coincided with sediment of very low porefluid salinity earthflow scars were absent from intervening areas of higher salinity 5 gl 1 mapping of the thickness of the clay deposit by seismic refraction showed furthermore that low porefluid salinity occurred only in areas of relatively thin 25 m deposits resting upon more permeable drift or rock finally laboratory tests confirmed that high sensitivity was restricted to areas of low porefluid salinity the study thus provides a geomorphological verification of the importance of salt depletion as a prerequisite for earthflow occurrence and by implication presents mapping of porefluid salinity as a method of delineating zones which should be safe from landslide retrogression in this type of sediment

oxygen isotope systematics in a multiphase weathering system in haiti abstract physical and chemical partial dissolution techniques have been applied to a suite of young karst bauxite and laterite samples from the southern peninsula of haiti the 18o values have been obtained for nine mineral species and range from 1 0 for anatase rutile to 33 4 for authigenic quartz on one hand results for quartz calcite kaolinite gibbsite and boehmite compare favourably with 18o values predicted from accepted mineral water fractionation factors assuming modern temperatures 25 2 c and water 18o values 3 1 0 5 on the other hand the 18o values measured for anatase illite smectite chlorite smectite and some iron oxide samples do not compare favourably with predicted values departures from expected values for these minerals may be related to crystallization from water with a different 18o value than modern water an imprecise knowledge of some mineralwater fractionation factors under surficial conditions or nonattainment of isotopic equilibrium between mineral and water during formation partial dissolution techniques hold considerable promise for obtaining quantitative 18o values of individual minerals in single samples of complex fine grained regolith material

origine de la preconsolidation des argiles du saguenay quebec the clays of eastern canada and in particular the saint jean vianney clay in the saguenay region have often been described as clays with a preconsolidation due partly to cementation in order to check this assumption the geological history and the geomorphology of the saguenay region have been analyzed further to the evidence of significant erosion available geotechnical data in the form of variations of water content undrained shear strength and preconsolidation pressure have been analyzed to determine the elevation of the original ground surface in the hypothesis of a preconsolidation resulting from deposition and erosion the results of this analysis are in good agreement with the geological and geomorphological data and they suggest that cementation has had a negligible effect on the preconsolidation of the saguenay clays a regional map of preconsolidation pressures is also presented keywords clay preconsolidation geomorphology erosion shear strength journal translation

vertical and lateral distribution of lacustrine carbonate lithofacies at the parasequence scale in the miocene hot spring limestone idaho an analog addressing reservoir presence and quality lacustrine carbonate lithofacies in the hot spring limestone vary systematically at meter to decameter scales and record paleobathymetry limnologic conditions and paleogeographic influences this unit accumulated during the late miocene in a lake system in an extensional basin complex closely associated with lava flows and volcaniclastics sedimentology and sequence stratigraphy enable understanding and prediction of the occurrence distribution and character of lacustrine carbonates occurrence of lacustrine carbonates is a function of lake basin type in this case a volcanically mediated balanced filled lake basin that contains various lithofacies microbialite grainstone packstone wackestone and carbonate mudstone distribution of lithofacies is strongly controlled by depositional subenvironment and gradient through water depth bottom energy circulation and accommodation internal character of microbialites i e type size porosity vertical and horizontal permeability associated lithotypes diagenesis is influenced by stratal position at the parasequence scale and location along the depositional profile depositional reservoir quality characteristics such as microbialite porosity and thickness grainstone size and sorting and overall carbonate continuity and connectivity peak in the medial sublittoral zone conversely secondary diagenetic effects such as dissolution carbonate and quartz cement and possible authigenic clays are highest in the updip lake plain littoral zones and are less common lakeward thus the medial sublittoral zone has the optimum potential where primary depositional characteristics are best developed and negative secondary diagenetic effects are minimal these strata share many attributes with the cretaceous presalt systems of the south atlantic and can provide insights about controls on potential reservoir character distribution and connectivity for exploration and development

deltas of the lake malawi rift east africa seismic expression and exploration implications high resolution air gun sourced seismic reflection surveys over the offshore regions of five river deltas in lake malawi in the east african rift system reveal considerable variability in acoustic facies and stratigraphic architecture this variability can largely be attributed to the influences of different structural settings and to a lesser degree to high amplitude 100 400 m and high frequency 1000 to 100 000 yr fluctuations in lake level deltas on flexural and axial margins in the rift lake show well developed progradational geometries in contrast a delta on a steep accommodation zone margin distributes coarse sediments over a broad depositional apron rather than concentrating sediment in discrete progradational lobes as on the other deltas a large border ault margin river delta displays the most complex tectonic and stratigraphic architecture of all the deltas studied it contains several delta associated facies including prograding clinoform packages fan deltas stacked against a boundary fault and extensive subaqueous fans flexural margin lowstand deltas may be the most prospective for hydrocarbon exploration due to their large internally well organized progradational lobes and their close proximity to deep water high total organic carbon lacustrine source facies

discovery of the ree minerals and its geological significance in the quyang bauxite deposit west guangxi china most of the karstic bauxite deposits in china are enriched in ree and the ree has commonly been considered to be adsorbed on the surface of clay or diaspore minerals as ion state however occurrence of ree minerals in the bauxite deposits has not been reported by far in the quyang bauxite deposit from guangxi province we find ree minerals the minerals are parisite and churchite parisite is widely distributed in the ooids and matrix inducing positive ce anomaly of the ores whereas churchite is rare and occurred in the core of ooid the compositions of the ree minerals show the eu anomaly can change gently during the weathering and the eu anomaly analyses suggest that the ree in the ores are mostly derived from the underlying carbonates the parisite is formed in an alkaline condition while churchite in an acidic situation the co existence of the two minerals in the ores suggests the permian environment for bauxite formation is complex with great change of ph value moreover parisite is inferred to be formed earlier than the churchite

importance of hydrogeological conditions during formation of the karstic bauxite deposits central guizhou province southwest china a case study at lindai deposit abstract karstic bauxite deposits are widespread in central guizhou province sw china and high grade ores are frequently sandwiched with overlying coal and underlying iron rich layers and form a special coal bauxite iron structure the lindai deposit which is one of the most representative karstic bauxite deposits in central guizhou province was selected as a case study based on textural features and iron abundances bauxite ores in the lindai deposit are divided into three types of ores i e clastic compact and high iron the bauxite ores primarily comprise diaspore boehmite kaolinite illite and hematite with minor quartz smectite pyrite zircon rutile anatase and feldspar the al 2 o 3 53 76 8 wt is the main chemical contents of the bauxite ore samples in the lindai district followed by sio 2 fe 2 o 3 tio 2 cao mgo s and p etc our geological data on the lindai deposit indicated that the ore bearing rock series and its underlying stratum have similar rare earth elements distribution pattern and similar y ho zr hf and eu eu values additionally all ore bearing rock samples are rich in mgo range from 0 16 wt to 0 68 wt and the plots of the dolomites and laterites lie almost on or close to the weathering line fit by the al bearing rocks in zr vs hf and nb vs ta diagrams suggesting that the underlying middle cambrian shilengshui formation dolomite is the parent rock of bauxite resources in the lindai district simulated weathering experiments on the modern laterite from the shilengshui formation dolomite in the lindai bauxite deposit show that hydrogeological conditions are important for karstic bauxite formation si is most likely to migrate its migration rate is several magnitudes higher than those of al and fe under natural conditions the reducing inorganic acid condition is the most conducive to al enrichment and si removal fe does not migrate easily in groundwater al enrichment and fe removal can occur only in acidic and reducing conditions with the presence of organic matter the geological and experimental studies show that coal bauxite iron structure in lindai deposit is formed under certain hydrogeological conditions i e since lateritic bauxite or al rich laterite deposited upon the semi closed karst depressions si can be continuously removed out under neutral acidic groundwater conditions the coal carbonaceous rock overlying the bauxitic materials were easily oxidized to produce acidic h 2 s h 2 so 4 etc and reductant groundwater with organic materials that percolated downward resulting in enrichment of al in underlying bauxite it also reduced fe 3 to its easily migrating form fe 2 moving downward to near the basal carbonate culminated in precipitating of ferruginous fes 2 feco 3 etc strata of the coal bauxite iron structure thus the bauxitic materials experienced al enrichment and si and fe removal under above certain hydrogeological conditions forming the high quality bauxite

seismic reflection imaging of a geothermal aquifer in an urban setting a seismic reflection survey that was conducted in downtown boise idaho to help city planners site a new well for injection of spent geothermal water illustrates some methods to safely and successfully employ a seismic reflection survey in an urban setting the objective of the seismic survey was to estimate the depth and continuity of a basalt and rhyolite volcanic sequence well siting was based on geothermal aquifer depth location of interpreted faults projected thermal impact of injection on existing wells surface pipe extension costs and public land availability seismic acquisition tests and careful processing were used to ensure high quality data while minimizing the potential for damage along city streets a video camera placed in a sewer and a blast vibration monitor were used to confirm that energy from the seismic source a 75 in3 land air gun did not damage nearby buildings street surfaces or buried utilities along the survey lines walkaway seismic tests were also used to compare sign

slope instability and valley formation in canadian soft clay deposits the purposes of the paper are to examine the deepening of valleys in clay deposits of eastern canada and in particular to look at the changes in the groundwater regime and slope stability conditions during valley formation field observations and laboratory testing indicate that the rate of valley deepening in champlain clay deposits is of the order of only a few millimetres a year owing to the low erodibility of the intact clay the clay banks are however more erodible owing to alteration and fissuration the stratigraphy of eastern canadian clay deposits can be simplified by considering it to be a stratum of low permeabilityconfined between two boundary layers of relatively high permeability which are the till layer at the base and a weathered crust or coarse grained layer at the top as the valley bottom get closer to the bottom till layer the groundwater regime and consequently the stability conditions are modified during the process of valley formation the groundwater regime passes through a

timing and duration of north american glacial lake discharges and the younger dryas climate reversal abstract radiocarbon dated sediment cores from the champlain valley northeastern usa contain stratigraphic and micropaleontologic evidence for multiple high magnitude freshwater discharges from north american proglacial lakes to the north atlantic of particular interest are two large closely spaced outflows that entered the north atlantic ocean via the st lawrence estuary about 13 200 12 900 cal yr bp near the beginning of the younger dryas cold event we estimate from varve chronology sedimentation rates and proglacial lake volumes that the duration of the first outflow was less than 1 yr and its discharge was approximately 0 1 sv 1 sverdrup 106 m3 s 1 the second outflow lasted about a century with a sustained discharge sufficient to keep the champlain sea relatively fresh for its duration according to climate models both outflows may have had sufficient discharge duration and timing to affect meridional ocean circulation and climate in this report we compare the proglacial lake discharge record in the champlain and st lawrence valleys to paleoclimate records from greenland ice cores and cariaco basin and discuss the two step nature of the inception of the younger dryas

high k alkali basalts of the western snake river plain idaho abrupt transition from tholeiitic to mildly alkaline plume derived basalts abstract basaltic volcanism in the western snake river plain underwent an abrupt change circa 700 ka to 900 ka from low k tholeiitic basalt and ferrobasalt to high k transitional alkali basalt the low k tholeiitic basalts share major element trace element and isotopic characteristics with olivine tholeiites of the eastern snake river plain and must have been derived by similar processes from similar sources in contrast the younger high k alkali basalts share major element trace element and isotopic characteristics with plume derived alkali basalts of ocean islands suites like hawaii we conclude that this abrupt transition reflects either or both the erosion of pre existing mantle lithosphere in the wake of the yellowstone snake river plume or the depletion of this lithosphere in fusible components so that it no longer contributed to the overall mass flux of magma the abruptness of the transition implies that it may have a catastrophic origin such as lithospheric delamination caused by a rayleigh taylor instability beneath the idaho batholith

genesis of ree minerals in the karstic bauxite in western guangxi china and its constraints on the deposit formation conditions abstract karstic bauxites in western guangxi china comprise two subtypes permian bauxite and quaternary bauxite the quaternary bauxite originated from the breaking up rolling and accumulating of permian bauxite in karstic depressions in quaternary various types of rare earth element ree minerals were discovered during the formation of the permian and quaternary bauxites from the xinxu longhe and tianyang bauxite deposits in this study five types of ree minerals including bastnasite parisite cerianite rhabdophane and churchite were identified bastnasite and parisite are the most abundant and they are widely developed in the permian ore and also present in the quaternary ore obvious variations in bastnasite and parisite ree compositions were observed which is ascribed to distinctions in the source materials in the primary weathering profile from different areas the mode of occurrence of bastnasite and parisite suggests they were mainly precipitated under alkaline and reducing conditions during the permian bauxite forming stage and underwent intensive corrosion in the quaternary churchite was formed during the permian weathering stage under acidic condition both cerianite and rhabdophane occur in fractures within the permian bauxite ore indicating that both formed during the quaternary weathering stage it is considered that the rhabdophane enriched in ce have formed locally in the process of that the ce3 released from bastnasite rapidly entered the rhabdophane lattice before being oxidized to ce4 cerianite was mainly found in association with mn al hydroxides suggesting that the released ce3 was oxidized into ce4 and precipitated cerianite in fractures within the permian bauxite ore mass balance equations reveal a depletion in nearly all rees during the transformation from the permian to the quaternary bauxite ore mainly caused by the dissolution of bastnasite and parisite the genesis of the ree minerals together with the occurrence of other minerals indicates that intensively acidic and oxidizing conditions developed before the formation of the permian bauxite ore towards the end of the permian the conditions became reducing and alkaline favorable for the large scale bauxitization the quaternary bauxite forming stage was characterized by variable ph and eh conditions with acidic ph 4 6 and oxidizing eh 2 conditions at the surface of the exposed permian bauxite ore

the causes and effects of aging in quick clays the physicochemical properties of a clay from la baie quebec were found to be typical of champlain quick clays very low plasticity liquidity index greater than 3 sensitivity greater than 500 and ph of about 9 5 the mineralogy is characterized by the abundance of primary or rock flour minerals such as feldspar quartz amphibole and calcite with illite as the principal clay mineral the pore water chemistry consists predominantly of sodium bicarbonate low concentrations of sulfate calcium and magnesium and high alkalinity and ph are attributed in part to anaerobic sulfate reduction processes taking place in situ quick clay samples stored in the laboratory showed signs of aging regardless of the storage procedure the remoulded strength and the liquid limit increased with time whereas the sensitivity the liquidity index and the ph decreased the water content plastic limit and undisturbed strength remained practically unchanged the pore water concentrations of calcium magnesium and su

a conceptual tectonostratigraphic model for seismic facies migrations in a fluvio lacustrine extensional basin one of the most fundamental differences between lacustrine basins and many marine basins is the stratigraphic response to differential tectonic subsidence because the water volume of a lake is finite tilting of the valley floor redistributes the lake water if the lake water level is below a hinge point fulcrum that experiences no net subsidence the lake shoreline is translated toward the site of subsidence and a deeper lake forms this tectonostratigraphic model for rift lake sedimentation is tested in a seismic and sequence stratigraphic study of deltaic and lacustrine deposits that accumulated in a cenozoic extensional basin beneath goshute valley nevada seismic sequences exhibit an internal cyclic stacking hierarchy of seismic reflections interpreted as the stratigraphic response of a lowstand paleolake to tectonism forced regression and subsequent lake level restoration transgressive and highstand systems tracts

evaluation of preconsolidation pressure and the overconsolidation ratio from piezocone tests of clay deposits in quebec the preconsolidation pressure and overconsolidation ratio profiles are the most important factors related to the mechanical behaviour of clay deposits they are interpreted on the basis of a limited number of laboratory tests but the near continuous information provided by the piezocone can allow local data to be extrapolated to an entire site numerous methods have been proposed for relating piezocone data to preconsolidation pressure and the overconsolidation ratio but their validity is still uncertain in this paper nine methods are compared on the basis of data collected on 31 sensitive clay sites in quebec whose preconsolidation pressure profiles are well known each method is briefly presented and the most promising are identified the simplest method which directly relates preconsolidation pressure to net tip resistance also appears to be the most effective key words clay preconsolidation pressure overconsolidation ratio piezocone correlations

genesis of the guangou karstic bauxite deposit in western henan china abstract the guangou bauxite deposit in western henan china is located in the north china block and to the north of the north qinling orogenic belt the orebody is hosted within the lower member of the carboniferous benxi formation which overlies unconformably upon the ordovician majiagou formation in the lower member of the benxi formation the bauxite orebody with a diaspore illite anatase mineral assemblage is sandwiched between underlying ferric clay illite hematite goethite and overlying top clay kaolinite quartz goethite according to field observations and geochemical evidence including trace and rare earth element ree compositions especially zr hf ratios the ferric clays were weathered from the underlying argillaceous limestones in the majiagou formation during this weathering process trace elements s zn ni cr v sc f ba and be are depleted li rb and b are enriched and zr hf bi ta ga nb and th are relatively immobile rees exhibit evident differentiation with enrichment of la ce pr and nd and depletion of gd tb dy ho er tm yb and lu the bauxite formed in weak reducing slightly basic water conditions according to the geneses of coexisting diaspore and anatase and it was altered during the epigenetic and second exposure periods forming kaolinite and goethite respectively interelemental relationship analyses of the ores suggest that the elemental behaviors of trace elements and rees in the bauxitization process are mainly controlled by the mineral compositions in bauxite ore and chemical properties of the elements for instance zircon rutile and anatase contain zr hf nb ta w and u based on geochemical evidence together with age data and chemical compositions of the detrital minerals both distant igneous rocks in the plate margin and paleozoic carbonates and precambrian rocks inside north china block provide the miscellaneous material for the bauxite ore and the top clay

pore pressure response to barometric pressure change in champlain clay prediction of the clay elastic properties abstract champlain sea clay deposits play a crucial role in limiting contaminant migration to underlying aquifers in the saint lawrence river valley champlain sea clays are well known as being prone to landslide and sample disturbance estimation of their elastic properties using their in situ loading efficiency would provide mechanical properties for the soil dynamic analyses and immediate settlement calculations encountered in geotechnical projects determination of loading efficiency can be envisioned as a very small strain test in this paper we describe a detailed monitoring program for 10 vibrating wire piezometers installed within sealed boreholes on 5 study sites near montreal in quebec canada the pore pressure response to barometric pressure variation was analyzed with three methods linear regression visual inspection and multiple regression which gave loading efficiencies between 0 7 and 0 95 these values were then used to estimate the elastic properties of the clay formation vertical compressibility and specific storage on the order of 1 10 6 kpa 1 and 1 10 5 m 1 were respectively obtained for most of the monitoring sites a comparison of compressibility values derived from the in situ loading efficiency method with those obtained with pressuremeter oedometer and pulse tests confirmed that clay compressibility is strain dependent the pore pressures measured on the study sites have been corrected by applying the multiple regression and visual inspection methods for most piezometers both methods provided nearly identical results however for deep piezometers the multiple regression method provided smoother pore pressure time series than the visual inspection method the vertical hydraulic gradient obtained with corrected pressure data was shown to change significantly on some test sites during the monitoring period

extension of the yellowstone plateau eastern snake river plain and owyhee plateau formation of the late cenozoic volcanic province comprising the owyhee plateau eastern snake river plain and yellowstone plateau has been accompanied by east northeast directed crustal extension a new vector of 45 mm yr n56 degree e for the migration of silicic volcanism across the volcanic province is calculated if migration of volcanism reflects west southwest continental drift over a mantle plume a zone of crustal extension must separate the volcanic province from the more slowly moving north american craton space time relations of basin fill in the adjacent basin and range province provide evidence for a zone of extension about 125 km wide coincident with and east of coeval silicic volcanism since 16 ma the zone of extension has migrated along with silicic volcanism maintaining its position between the province and the unextended craton

intra vent peperites related to the phreatomagmatic 71 gulch volcano western snake river plain volcanic field idaho usa abstract the western snake river plain volcanic field in sw idaho contains up to 400 basaltic vents and centers that produced lava shields pahoehoe lava fields scoria cones and a great variety of phreatomagmatic volcanoes between late miocene and middle pleistocene time tephra deposits produced by phreatomagmatic eruptions are particularly well exposed in the walls of the snake river canyon where thick accumulations of pyroclastic rocks indicate widespread phreatomagmatic eruptive events throughout most of the volcanic history of the region previously many of the phreatomagmatic deposits were considered to be the products of subaqueous eruptions that took place on the floor of one or more large freshwater intra continental lakes recent field based observations confirm the presence of widespread phreatomagmatic pyroclastic rocks however some that had been interpreted as being subaqueous exhibit textural features that are more consistent with subaerial depositional environments intrusive and extrusive magmatic bodies with features associated with peperite formation have also been identified most of these peperites can be attributed to magma sediment mixing in intra crater conduit or vent settings and therefore they can only be used as widespread paleoenvironmental indicators with limitations to demonstrate magma and surface water e g lake non explosive interaction one of the studied sites 71 gulch volcano was previously used to indicate the presence of a shallow lake at this site there is clear field evidence that peperitic feeder dykes contacted muddy sandy siliciclastic sediments forming globular peperite the peperitic feeder dykes transition to pillowed ponded lava up section the ponded lavas are partially surrounded by a 5 m thick unit composed of gently dipping dune bedded volcanic glass shard rich unsorted tuff and lapilli tuff containing abundant impact sags caused by volcanic lithics we suggest that the 3d architecture of the erosional remnant of 71 gulch volcano does not require the presence of a lake at the time of its formation it is equally possible that that it represents a subaerial phreatomagmatic upper conduit crater filling succession this interpretation opens up many questions about the mio pliocene evolution of sw idaho the timing of the volcanism and its association with the evolution of the lacustrine systems in the region in addition re evaluations of the volcanic features in sw idaho have some general implications for the usage of phreatomagmatic pyroclastic rocks for paleoenvironmental reconstruction

the carbon isotope composition of organic matter occluded in iron nodules abstract this study presents 13 c and 14 c results for soil organic carbon and carbon occluded by iron nodules from a quaternary soil profile developed on basalt in western victoria australia the results suggest that the 13 c value of organic matter in the iron nodules is directly inherited from the surrounding soil profile without isotopic fractionation and that therefore the 13 c value of organic matter occluded by the iron nodules can be related to the vegetation present during nodule formation however 14 c results suggest that iron nodules are not closed systems with respect to organic carbon and that even chemically resistant immobile particulate carbon of probable microbial origin has been added to the nodule carbon pool since formation nevertheless the turnover time for chemically resistant particulate carbon in the iron nodules is at least three times that for the same fraction in the surrounding soil making iron nodules useful repositories of palaeoenvironmental information particularly where they have been removed from the active surface soil layer by burial

volcanic ash beds recorders of upper cenozoic silicic pyroclastic volcanism in the western united states stratigraphic relationships and tephrochronologic information for volcanic ash beds 4 0 0 1 m y of the western interior allow the recognition of at least 68 different ash falls the average reoccurrence rate based on the succession of the isotopically dated ash beds is near one eruption every 57 000 years the ash beds were grouped into two chemical types rhyolitic and dacitic the main property that distinguishes dacitic from rhyolitic ashes is the larger ca and mg and smaller k content in dacitic ashes dacitic volcanic ashes were defined to have more than 0 55 wt ca rhyolitic ashes were subdivided further into two types w and g type based on the presence of biotite in the w type and its absence in g type w type rhyolitic ashes are chalky white have less than 0 55 wt fe have colorless glass shards of pumiceous habit g type rhyolitic ashes are light to medium gray have from 0 55 to 2 0 wt fe in the glass shards lack biotite have colorless platy bubble wall and bubble junction glass shards dacitic ashes are light gray to grayish brown have more than 0 55 wt fe and ca and have a complex mixture of colorless to light brown shards including pumiceous fibrous chunky and bubble wall and bubble junction types w type rhyolitic ashes possibly formed from magmas that were cooler 695 to 830 c and thus more viscous than the hotter 870 to 1000 c magma progenitors of g type ashes based on fe ti oxide mineral compositions primary microphenocrysts in the ash beds comprise assemblages of the following quartz sanidine plagioclase biotite amphibole clinopyroxene orthopyroxene fayalite zircon apatite allanite chevkinite sphene magnetite and ilmentite fayalite and chevkinite only have been found in g type biotite and sphene only have been found in w type rhyolitic ashes are highly evolved and contain 74 79 wt sio2 dacitic ashes vary from 67 77 wt sio2 al ranges from 10 5 to 14 5 wt al2o3 mg ranges from 0 06 to 1 0 wt mgo and fe as fe3o4 ranges from 0 50 to 4 1 wt dacitic ash beds have the most 0 80 3 8 wt as fe3o4 and rhyolitic ashes have the least 0 50 1 9 wt as fe3o4 ca varies from an unusually low amount 0 25 wt cao in a few rhyolitic ashes to as much as 2 2 in some dacitic ashes rhyolitic glasses show larger eu deficiencies compared to dacitic glasses on rare earth element diagrams w type rhyolitic glasses have moderately large la to sm ratios and have la contents from about 30 to 100 times chondrite values g type rhyolitic glasses also have moderately large la to sm ratios and contain somewhat more la than do the w type rhyolitic ashes generally from 100 to 300 times chondrites amounts

the coal bauxite iron structure in the ore bearing rock series as a prospecting indicator for southeastern guizhou bauxite mines bauxite deposits in southeastern guizhou occur in the lower permian liangshan formation the rock series bearing the sedimentary bauxite exhibit a typical coal bauxite iron structure in which the lower part consists of bauxitic shale intercalated with siderite concretions the middle part consists of bauxitic rock intercalated with multilayer lenticular or earthy bauxite and the upper part consists of carbonaceous shales and sandstones intercalated with coal seams the paralic coastal and paludal depositional environments at one time had a stable tectonic setting by studying the elemental geochemistry of the ore bearing rock series it can be seen that the common presence of the coal bauxite iron structure has resulted from 1 the extensive desilication and iron depletion during the formation of the sedimentary bauxite due to the varying physical and chemical environment and 2 the sufficient supply of organic matter by the external environment such geological anomalies that resulted from the physical and chemical changes during the formation of the layered structure in the ore bearing rock series can serve as a mineralization indicator in prospecting for new deposits

the 14c dates and 13c 12c ratios of soil organic matter as a means of studying the past vegetation in intertropical regions examples from colombia south america abstract the 14 c ages and 13 c 12 c values were obtained on soil organic matter of various soils sampled in the guasca valley adjacent to the high plain of the sabana de bogota in the colombian cordillera oriental a soil distribution is observed as a function of climatic and altitudinal changes in the lowest parts of the valley planosols are found from the bottom of the valley to 2700 2800 m at altitudes up to 2900 m brunizems and ferrisols occur above 3000 m andic soils are almost everywhere present in more humid mountain zones at present the landscape is widely open without any natural forest nevertheless it was proved by pollen analytical data that at altitudes up to 3000 m the andean forest replaced a paramo formation 13 000 yr ago to conciliate the facts with the known evolution of the vegetal population a first hypothesis consists of admitting that open landscapes were due to a recent anthropogenic destruction of the forest the forest degradation hypothesis was tested by determination of the 13 c 12 c ratio because the trees have a 13 c of 25 to 28 influence of plants with c 3 photosynthesis pathway whereas herbs characteristic of open vegetation such as tropical grasses may have a 13 c of 23 to 16 due to a c 4 photosynthetic cycle the organic matter dated at 13 000 30 000 yr has 13 c close to 25 in the andic soil zone this indicates that at elevations of around 3000 m a cold paramo vegetation was probable for organic matter dated at 12 000 6000 yr 13 c shows a variation from 23 to 21 that does not indicate forest conditions it is uncertain that a forest stage occurred in the past for the planosols brunizem and ferrisol organic matter dated at 13 000 20 000 yr has a 13 c 23 compatible with the paramo vegetational phase occurring at that time for organic matter dated at 9500 yr and less 13 c varies from 20 to 17 these values do not confirm the evidence of forest conditions but rather the existence of open vegetation typified by a mixture of c 3 plants shrubs and rare trees and tropical graminaea thus the 13 c values prove that the valley has known drier and warmer influences that prevented the forest from developing during the holocene to explain the origin of the open landscapes of the valley the hypothesis of recent human deforestation must be discarded moreover the valley appears as a persistent dry enclave in the oriental cordillera

expansion of c4 grasses in the late miocene of northern pakistan evidence from stable isotopes in paleosols stable isotopic clay mineralogic and bulk chemical analyses were conducted on paleosols of the neogene siwalik sections in northern pakistan in order to reconstruct floodplain environments over the past 17 ma the stable carbon isotopic composition of soil carbonate mean 13c pdb 10 2 and associated organic matter mean 13c pdb 24 1 in paleosols representing 17 7 3 ma reveal that floodplain vegetation was dominated by c3 plants at 7 3 ma a shift toward more positive carbon isotopic values began signaling the gradual expansion of c4 grasses onto the floodplain from 6 ma to present carbon isotopic values for paleosol carbonate mean 13c pdb 0 6 and organic matter mean 13c pdb 14 4 are uniformly enriched in 13c indicating the presence of nearly pure c4 grassland the scarcity of kaolinite and abundance of smectite and pedogenic carbonate in most paleosols suggest that rainfall in the region remained 1 0 1 25 m yr or less for the entire 17 ma of record paleosols in the lower portion of the section lack organic a horizons but have reddish b horizons often containing secondary iron oxide nodules leaching depths of soil carbonate in these older paleosols are typically greater than those in the plio pleistocene part of the section where organic a horizons are common and b horizons are markedly more yellow the combined evidence suggests that the mature paleosols in the pre 7 3 ma part of the record are dominantly calcareous alfisols or mollisols that once underlay nearly pure c3 vegetation perhaps trees and shrubs while calcareous mollisols underlying c4 grassland dominate the upper part of the record the carbon and oxygen isotopic trends in the paleosol record in pakistan are also evident in the diet of fossil mammals and in paleosols from nepal thus demonstrating that these paleoenvironmental changes in floodplain vegetation may be continent wide local effects such as the development or intensification of the asian monsoon driven by uplift of the tibetan plateau may have led to the expansion of c4 grasses if however the expansion of c4 grasses proves globally synchronous then a larger scale cause such as a marked decrease in co2 may be the driving mechanism

proprietes caracteristiques des argiles de l est du canada the compilation of numerous geotechnical data has allowed the definition of the main physical mechanical and hydraulic properties of marine and lacustrine clays of eastern canada as well as the establishment of correlations between some of these properties the possible uses of these correlations are described this study shows that the clays of eastern canada exhibit a behaviour similar to that of other clays but that they are characterized by a higher degree of structuration keywords physical properties mechanical properties hydraulic properties clays canada correlations journal translation

mass change calculations in altered rock series a technique is presented whereby precursors of altered rocks in a fractionated rock series can be identified and changes in chemical components mass and volume accurately calculated the procedure utilizes elements with high degrees of immobility in hydrothermal and associated interactive water rock systems igneous rock series and sedimentary and metamorphic rocks with primary continuity of chemical composition are amenable to this treatment in the procedure for igneous rocks best fit fractionation lines are established for an immobile igneous compatible incompatible element pair the latter element functioning as the fractionation monitor alteration paths are linear and pass through the origin intersections of the fractionation and alteration lines yield the immobile element concentrations in the precursors to the altered rocks mobile components are determined from fractionation lines and monitor values total mass changes are proportional to the displacement of altered samples from the fractionation line masses of other elements in an altered sample reconstructed values are recalculated to the concentration of the monitor element in the precursor chemical changes are the differences between the calculated precursor compositions and the reconstructed altered rock compositions errors are mainly a function of the positioning of the fractionation lines

palaeosols in early himalayan foreland basin sequences demonstrate latitudinal shift related long term climatic change the palaeogene sedimentary record in the himalayan foreland basin contains palaeosols that are interpreted as reflecting changes in climate through time with the passage of the indian plate from the equator to 30 n latitude to understand spatial and temporal variation in the occurrence of diagnostic palaeosol types 12 exposed stratigraphic sections were investigated and studied in detail using petrographic and geochemical techniques including scanning electron microscopy and x ray mineralogy oxisol bauxite is a karst bauxite that occurs in crudely bedded and laminated forms it contains gibbsite goethite and kaolinite and shows chemical index of alteration values close to 100 demonstrating intense weathering no gradual change in the concentrations of trace and rare earth elements is recorded however their behaviour suggests that the oxisol was produced by weathering of basalt under a warm and humid climate histosol coal found stratigraphically higher than oxisols contains woody structures dominated by vitrinite maceral the histosol is interpreted as having originated from an undisturbed peat developed in a swamp of high tree density under wet tropical climatic conditions up section calcrete profiles of stages 3 and 4 containing rhizoliths pellets filamentous calcite and microcodium have developed by pedogenic processes large negative stable carbon 8 5 to 11 2 and oxygen isotope values 8 5 to 12 6 suggest that the studied calcretes formed under the influence of meteoric water and soil organic matter in dry sub tropical climatic conditions the formation of oxisol in a warm and humid climate was possible in the equatorial region when part of the indian subcontinent was close to the equator the coal developed under a humid climate when the northern tip of the indian subcontinent reached the intertropical convergence zone while the pedogenic calcrete formed once the sub tropical climatic zone was reached hence it is suggested that these palaeosols formed in different climatic zones during northward drift of the indian plate and that the drift brought them to their present positions between 30 n and 35 n within the sub tropical climatic zone

geochemistry and secular trends in the middle late permian karst bauxite deposits northwestern iran abstract this study focuses on the middle late permian bauxite deposits found within karstic depressions and sinkholes of carbonates of the ruteh and nessen formations northwestern iran data concerning five karst bauxite deposits each related to a different stratigraphic position within the bedrock were selected to address the chemical distribution and inter elemental relationships especially for critical elements factors that control bauxite formation and the parental affinity the analyzed samples mainly clayey bauxite and bauxitic clay are characterized by large compositional fluctuations involving both major and trace elements the major element composition is dominated by sio2 tio2 al2o3 and fe2o3 among the critical elements compositional fluctuations induce the occurrence of outliers for co nb ta lree and hree similar to other trace elements such as ba sr cr u and zr elemental mobility indicates that most of elements are generally depleted among the critical elements co is enriched only in several samples of the older deposits and ree are enriched in some samples of the younger deposits factor analysis suggests that due to the observed al ga covariance fairly acidic conditions were never attained during bauxitization and that detrital resistant minerals concentrated during a bauxitization stage promoting al ti accumulation furthermore the u co variance with low soluble elements nb ta and th suggests that u was mostly conservative during the formation of deposits cobalt co varies with cr and these elements accumulated during later bauxitization stages when the massive leaching of silica occurred the cia ciw and pia paleo weathering proxies indicate an upward weathering increase which suggests a trend toward more extreme weathering conditions in a wetter and warmer climate according to the permian global warming this is consistent with an upward increasing ba sr ratio and the inspection of the a cn k plot where the younger deposits fall close to the a k edge involving a clayey precursor requires a rainfall increase interestingly the upward trend toward a warmer and wetter climate was also coupled with paleo redox conditions promoting cerium oxidation as depicted by the ce ce values finally the eu anomaly and the sm nd ratio indicate that the studied bauxite deposits were mainly derived from a mafic protolith that formed in the middle late permian as a consequence of the volcanism that affected the entire iranian platform a cluster of karst bauxites however has eu eu values lower than the average standard deviation range of the mafic rocks suggesting a possible contribution of a more differentiated and less mafic protolith similarly the u th ratio at large supports the hypothesis of a mafic protolith for the middle late permian bauxite deposits although some samples show the u th values well above the average standard deviation range of the mafic rocks likely indicating that processes promoting the accumulation of resistant minerals with high u th ratios cannot be excluded this means that in this case the u th ratio does not necessarily reflect the protolith of karst bauxites and that more in general this proxy needs to be carefully interpreted when used to assess the parental affinity of residual rocks

geochemistry of the apulian karst bauxites southern italy chemical fractionation and parental affinities article i nfo this study focuses on a late cretaceous karst bauxite deposit in the murge area of the apulia district southern italy the first analysis of the vertical distributions of a wide range of elements including rees and selected trace elements throughout the deposit was shown in order to identify the processes determining element frac tionation during the evolution of the bauxite the studied karst bauxite deposit exhibits an ooidal texture is mineralogically homogeneous and contains higher abundances of boehmite than of hematite kaolinite and anatase the major element composition of the bauxite is dominated by elevated concentrations of sio2 t io2 a l2o3 a nd fe2o3 and analyses of element mo bility within the bauxite indicate that all elements except for nb and ni and to a lesser extent cr are depleted relative to the immobile element ti r mode factor analysis revealed a number of key findings i some low solubility elements e g zr th ti v ga were concentrated in detrital zircon and monazite zr th in anatase ti v and possibly in boehmite and hematite ga during the later stages of bauxitisation ii fe and cr were concentrated during wet conditions whereas al and co accumulated during dry conditions iii distributions of the light rees lrees and the heavy rees hrees are controlled by the same processes suggesting that little lree hree fractionation occurred during bauxite formation and iv the behaviour of cerium is different from that of the other rees and highly variable cerium anomalies are observed across the deposit with three characteristic ce ce maxima with values ofn2 parisite was the only authigenic cerium mineral detected during this study thus we propose a three step model to explain the distribution of ce cerianite is dissolved by cerium reduction is transported by downward moving meteoric water per descensum and finally parisite is precipi tated this cycle was repeated several times in the apulian karst bauxite in response to eh decreases under alka line conditions promoted by fluctuations in the groundwater level finally we used the value of the eu anomaly todiscuss theparental affinity or protolith of thebauxite the value of the eu anomaly min eu eu 0 76 max eu eu 0 89 indicates that the bauxite was not derived from carbonates but rather that the majority of the bauxite was influenced by intermediate to mafic magmatic sources eu eu vs sm nd diagram suggests that the parental material for the bauxite was derived from a combination of a distant magmatic source and clastic material derived from a continental margin northern africa to the south

strength development with burial in fine grained sediments from the saguenay fjord quebec following a sedimentological and geotechnical investigation two main types of materials were identified in the saguenay fjord 1 organic rich sediments deposited by continuous sedimentation and 2 unbioturbated sediments deposited rapidly by episodic events the consolidation state of sediments with depth were analysed in all subsurface deposits sediments are overconsolidated irrespective of the depositional processes however in continuously deposited sediments strength develops more rapidly than in turbidites or mass flows in the surficial bioturbated layer strength and liquidity index gradients are at a maximum and the rate of strength variation can reach values as high as 9 kpa kpa results from one dimensional creep tests suggest that in the organic poor turbidites the strength development is controlled at least partly by thixotropic strengthening for bioturbated clays it appears that the viscosity and the aggregating potential of organic matter controls the evolution of the strength

mineralogical and geochemical evolution of the bidgol bauxite deposit zagros mountain belt iran implications for ore genesis rare earth elements fractionation and parental affinity the present study focuses on the late cretaceous bidgol bauxite deposit in the zagros simply fold belt sw iran the orebody is located in the eroded major nw se trending koh e hosseyn anticline and hosted as discontinuous stratified layers and lenses within the upper member of the cenomanian turonian sarvak formation detailed mineralogical analysis reveals that diaspore hematite goethite anatase clinochlore chamosite and calcite are the major mineral components accompanied by minor amounts of detrital and ree bearing minerals such as rutile zircon and parisite the ore texture suggest that the bauxite material has an authigenic origin but in some parts it has been transported short distances from a primary in situ environment and redeposited in karstic depressions the spheroidal pisolites of the bidgol bauxite formed under conditions of low water activity favouring the formation of large diaspore cores and a single dry to wet climatic fluctuation the mass change calculations relative to the immobile element ti show that elements such as si fe mg k na and sr are leached out of the weathered system al ni zr ga cr and ba are concentrated in the residual system and hf ta co rb cs be and u are relatively immobile during the bauxitisation processes the nb th y v sc sn and ree are relatively immobile in the initial stage of bauxitisation processes in the bauxite ores but were slightly mobile at the later stage of bauxitisation geochemical data reveal progressive enrichment of the ree and intense lree hree fractionation toward the lower parts of the bauxite profile cerium behaves differently from the other rees especially lree and show positive anomalies in the upper horizons that gradually become negative in the deeper parts of the profile the distribution and fractionation of trace elements and rees during the bauxitisation process in the bidgol deposit are mainly controlled by the presence of ree bearing minerals fluctuations in soil solution ph ree ionization potential and the presence of bicarbonates or organic matter geochemical analyses confirm a protolith contribution from the bedrock argillaceous limestone and suggest that the source material for the bidgol bauxite was provided from a siliciclastic material derived from a continental margin the mid turonian uplift led to the formation of karstic topography rubbly breccia and a layer of ferruginous argillaceous debris that was affected by lateritic weathering under humid tropical climate subsequently mobile elements are removed from the profiles while al fe and ti are enriched resulting in the formation of the pristine bauxite materials when the platform subsided into the water again the pristine bauxitic materials were partly converted to bauxite during the exposure of bauxite orebodies on the limbs and crests of anticlines and subsequent eroding and accumulation in the karstic depressions during folding and faulting in oligocene miocene important factors such as intensity of the weathering drainage and floating flow may have improved the qualities of the bauxite ores

fan deltas and braid deltas varieties of coarse grained deltas two types of coarse grained deltas are recognized fan deltas and braid deltas fan deltas are gravel rich deltas formed where an alluvial fan is deposited directly into a standing body of water from an adjacent highland they occupy a space between the highland usually a fault bounded margin and the standing body of water in contrast braid deltas here introduced are gravel rich deltas that form where a braided fluvial system progrades into a standing body of water braid deltas have no necessary relationship with alluvial fans as exemplified by fluvioglacial braid deltas braid deltas have previously been classified as fan deltas even though the geomorphic and sedimentologic settings of the two systems can be vastly different braid deltas are a common present day geomorphic feature and are abundant in the geological record fan deltas and braid deltas can be distinguished in the rock record by distinctive subaerial components of these depositional systems the shoreline and subaqueous components of both are similar fan delta sequences have a subaerial component that is an alluvial fan facies comprising interbedded sheetflood debris flow and braided channel deposits fan deltas produce small a few tens of square kilometres wedge shaped bodies of sediment commonly displaying high variability in paleocurrent patterns and abrupt changes in facies the deposits are generally very coarse grained with large out sized clasts very poorly sorted matrix rich polymictic heterolithic partially cemented by penecontemporaneous carbonate and have low porosity and permeability braid deltas in contrast have a subaerial component consisting entirely of braided river or braidplain facies their deposits display better sorting roundness and clast orientation than do fan delta sediments they lack a muddy matrix they display size grading and bar migration they commonly have a sheet geometry with high lateral continuity tens to hundreds of square kilometres and they exhibit moderate to high porosity and permeability valuable paleogeographic and tectonic information concerning the proximity of highlands and major fault zones may be misinterpreted or lost if these two coarse grained deltaic systems are not differentiated

chemical characteristics and evolution of the laterite profile in hazaridadar bauxite plateau madhya pradesh india a chemical study of the laterite profile developed over basalts in the hazaridadar plateau in madhya pradesh india is presented based on data obtained from intensive exploration in ascending order the profile consists of lithomarge saprolite laterite and bauxite with laterite the formation of the profile essentially involves desilication and hydration in absolute terms there is no major gain or loss in tio 2 and al 2 o 3 judging from the chemical character of the different zones the profile has been evolved by gradual in situ weathering of basic rocks under favorable conditions it is postulated that the profile has been developed in three distinct stages first formation of lithomarge by partial desilication and hydration has been followed next by the formation of a laterite horizon with a fixed composition in terms of al 2 o 3 fe 2 o 3 desilication is more or less complete in this stage finally differential leaching of al 2 o 3 and fe 2 o 3 and the downward migration of the latter have resulted in the formation of a zone of bauxite within the laterite at the top and another of laterite at the bottom the latter showing evidence of deposition of secondary fe 2 o 3 zones favoring free movement of water in the top levels of the laterite are suggested as favorable horizons for enrichment in al 2 o 3

paleoclimatic significance of lake level fluctuations in the lahontan basin abstract an energy flux balance model has been developed which treats evaporation as a function of air temperature surface water temperature precipitable water aloft the amount height and type of sky cover and the optical air mass the model has been used to estimate the mean historical evaporation rate for pyramid lake nevada using as input climatic data from the reno area averaged over the period 1950 1975 estimated and measured values of the mean annual evaporation rate were found to be in good agreement the model was used to simulate changes in the level the surface area and the volume of paleo lake lahontan in particular possible climatic states responsible for past high stands 1270 and 1330 m were investigated a conservative range of discharge values was used in the calculations results of the simulations indicate the fundamental importance of sky cover in the creation and destruction of large lake systems

mineralogical characteristics of the superlarge quaternary bauxite deposits in jingxi and debao counties western guangxi china abstract in recent decades more than 0 5 billion tons of ores scattered in the quaternary laterite in western guangxi china have been explored the ores were derived from a bauxite horizon in permian via physical break up and re sediment process utilizing various test methods i e xrd dta tg dtg sem eds and epma the mineralogical characteristics of the quaternary bauxite ores in jingxi and debao counties were investigated xrd was used together with tg dtg to obtain relatively accurate ore mineral abundance diaspore is the major phase whereas hematite kaolinite anatase chamosite gibbsite goethite illite and rutile are minor diaspore is characterized by a small particle size low degrees of crystallinity and complex chemical composition both gibbsite and goethite have a varied particle size and goethite crystals contain high al substitution and si it is clarified that diaspore chamosite and anatase were formed in a mildly reduced and alkaline depositional environment in permian while gibbsite hematite goethite and part kaolinite were precipitated from al 3 si 4 and fe 3 enriched solutions within an quaternary oxidized environment the ions al 3 si 4 and fe 3 are mostly released from chamosite in its dissolution process the different physicochemical conditions between the permian depositional and the quaternary weathering periods resulted in a complex mineral assemblage in the quaternary bauxite

the lachenaie clay deposit some geochemical and geotechnical properties in relation to the salt leaching process this paper summarizes a detailed geotechnical and geochemical characterization program for the champlain clay deposit in lachenaie quebec presently the clay pore water is saline the main objective of the testing program was to study the leaching of the clay saline pore water since its deposition four issues are discussed in this paper first the deposit is shown to comprise two distinct clay layers with contrasting geotechnical properties the liquid limit and grain size distribution are the properties that best distinguish the two materials the upper layer is more plastic while the lower one is relatively silty the occurrence of these two layers is shown to be in agreement with some recent findings in quaternary geology second the relatively high pre consolidation pressures of the clay in the lachenaie area are shown to be coherent with an erosion scenario and the elevation of a neighbouring bluff previously interpreted as an erosion terrace third the relatively constant hydraulic conductivit

paleolimnology evolution in rift basins the ischigualasto villa union basin central western argentina during the triassic abstract extensional basins offer a high preservation potential for sedimentary and fossil records nonmarine rift basins contain diverse environments including fluvial and lacustrine lake deposits have long been recognized as significant archives of the paleoenvironmental record the ischigualasto villa union basin represents the only nearly continuous continental triassic record with up to 6000 m of alluvial fluvial and lacustrine deposits the deep lacustrine interval is known as the los rastros formation and consists of several lacustrine deltaic cycles a detailed facies analysis allowed the characterization of five facies associations and two types of cycles 1 a shoreline dominated progradational type i cycle containing facies association a offshore lacustrine deposits and facies association b marginal palustrine deposits along the shoreline of the lake or facies association c lacustrine siliciclastic coastal deposits and 2 a delta dominated progradational type ii cycle characterized by facies association a offshore lacustrine and prodelta deposits facies association d delta front deposits and facies association e delta plain deposits the sedimentary evolution of the chanares los rastros sequence is defined within this extensional setting as one depositional sequence with three system tracts lowstand transgressive and highstand system tract biotic abiotic and sedimentologic data allowed the interpretation of the limnologic dynamics of the los rastros paleolake as a deep freshwater lake within a half graben exhibiting meromixis and showing a change from moderate eutrophic conditions with low oxygen content to relatively oxygenated oligotrophic conditions the successive fluctuations recorded in lake level are considered in the sequence stratigraphic framework of bohacs et al to reflect the relative balance of sediment and water input versus accommodation in an overfilled lacustrine basin

geochemical discrimination of clastic sedimentary rock sources abstract factors controlling the geochemistry of a clastic sedimentary rock can include 1 composition of source terrain 2 chemical weathering 3 hydraulic sorting 4 diagenesis 5 metamorphism and 6 hydrothermal alteration a linear solution inferring source terrain composition from geochemistry of the sediment is impossible in this multivariate system as several unknowns will commonly be present the use of graphical analysis of element pairs circumvents the problem chemically immobile elements will maintain invariant ratios during rock mass change caused by either addition or depletion of mobile elements this results in chemically immobile element scattergrams exhibiting linear trends along radians extending from the origin if the major mineral phases of the immobile elements have behaved in a hydrodynamically similar manner as chemically mobile element plots will produce a scatter of points this relationship can be used to test chemical immobility and similarity in hydrodynamic sorting history the constraint on analysis is that the source area must be compositionally uniform or the sediment well mixed prior to delivery to the basin a second technique using sio2 plots has also been developed to investigate element mobility and hydrodynamic behaviour of the mineral phases containing the elements sio2 immobile element plots result in a linear arrangement of points extending towards either 0 or 100 sio2 the 0 intercept position occurs for elements with major mineral phases concentrated in sand the 100 intercept for those concentrated in clays plotting chemically mobile elements produces different patterns and this can be used to gain information on alteration and sorting history elemental ratios for chemically immobile elements with similar hydrodynamic behaviour will be the same as those for the weighted average composition of the source material this provides a powerful tool for deducing source terrain from sediment geochemistry techniques outlined above were tested on archaean metasandstones from superior province canada immobile element ratio diagrams for nb al ti and zr al ti indicate that a calc alkaline extrusive intrusive suite lying to the north of the study area was the source and not five other volcanic suites in the region this conclusion agrees with previous clast lithology studies and accentuates the applicability of the geochemical techniques

hammer seismic reflection imaging in an urban environment subsurface characterization within urban centers is critically important for city planners municipalities and engineers to estimate groundwater resources track contaminants assess earthquake or landslide hazards and many other similar objectives improving geophysical imaging methods and results while minimizing costs provides greater opportunities for city project planners and geophysicists alike to take advantage of the improved characterization afforded by the particular method seismic reflection results can provide hydrogeologic constraints for groundwater models provide slip rate estimates for active faults or simply map stratigraphy to provide target depth estimates while many traditional urban seismic transects have included the use of vibroseis sources to improve reflection signals and attenuate cultural noise low cost and high quality near surface seismic reflection data can be obtained within an urban environment using impulsive sources at a variety of scales and at production rates

the graveyard point intrusion an example of extreme differentiation of snake river plain basalt in a shallow crustal pluton the graveyard point intrusion is the only known example of a wellexposed differentiated mafic pluton associated with the late miocene pleistocene magmatism of the western snake river plain srp it is exposed in a 6 km by 4 km area adjacent to the oregon idaho border and exposures range in thickness from 20 to 160 m the thicker parts of the intrusion are strongly differentiated and contain a 25 60 m thick section of well laminated cumulus textured gabbros that grade upward into pegmatoidal ferrogabbro evolved liquids formed sheets of fe rich siliceous granophyre at least two injections of magma are indicated by abrupt discontinuities in the rock and mineral compositions and by the lack of mass balance between the bulk intrusion and its chilled borders the laminated gabbros are interpreted to have formed from a tongue of augite and plagioclase crystals that were carried in with the second pulse of magma following the final emplacement of the intrusion in situ differentiation proceeded through a two stage process the ferrogabbros are explained as interstitial liquids forced out of the crystal mush by compaction and the siliceous granophyres are interpreted to be residual liquids that migrated out of the partly crystallized ferrogabbros in response to the exsolution of volatiles because the geochemical trend inferred for the mafic to intermediate composition liquids in the graveyard point intrusion is similar to the trend for many western snake river plain lavas the pluton may be a good model for shallow sub volcanic magma chambers elsewhere in the srp however some western srp lavas contain anomalously high concentrations of p2o5 which are best explained by mixing within the active crustal mush column or with partial melts of previously formed differentiated mafic intrusions

the permeability of natural soft clays part ii permeability characteristics reply the permeability characteristics of a number of intact natural soft clays from quebec the usa and sweden have been investigated in the laboratory the variation of permeability with void ratio is best represented in terms of a linear e vs lg k relation which is generally valid in the range of volumetric strains encountered in engineering practice the permeability at the in situ void ratio is shown to be a complex function of such parameters as the void ratio the clay fraction the plasticity index and the fabric of the clay permeability anisotropy is negligible in marine clays the e vs lg k relationships of the various clays tested are well ordered in terms of an empirical parameter ip clay fraction irrespective of the geological origin of the clay the slope of the e vs lg k relationship referred to as permeability change index ck is simply related to the initial void ratio by ck 0 5eo keywords permeability clays laboratory tests permeability anisotropy permeability void ratio re

seismic expression and geological significance of a lacustrine delta in neogene deposits of the western snake river plain idaho high resolution seismic reflection profiles and well data from the western snake river plain basin are used to identify a buried lacustrine delta system within neogene idaho group sediments near caldwell idaho the delta system is detected 305 m 1000 ft deep near the center of the basin by progradational clinoform reflections having dips of 2 5 a slope typical of prodelta surfaces of modern lacustrine delta systems the prodelta slope relief corrected for compaction indicates the delta system prograded northwestward into a lake basin 255 m 837 ft deep resistivity logs in the prodelta mud and clay facies are characterized by gradual upward increase in resistivity and grain size over a thickness of about 100 m 300 ft lithology of the prodelta is mostly c lcareous claystone with several layers of fine sand some of which fine upward indicating a density flow mechanism of transport and deposition delta plain and front sediments are mostly very fine grained well sorted sand separated by thin mud layers these sediments produce several to five cycles of horizontal high amplitude reflections with a toplap relationship to prodelta clinoforms the sands have an abrupt lower contact with prodelta muds and have high resistivity on logs in this study permeable lacustrine sands within a predominantly mud and clay section are located by using high resolution seismic reflection data identification of a delta system in the idaho group provides insight into the history of pliocene lake idaho the present depth of the delta prodelta facies contact of 305 m 1000 ft is 445 to 575 m 1460 1900 ft below the lake deposits on the margins estimated subsidence from compaction is 220 m 656 ft and the remaining 225 to 325 m 740 1066 ft is attributed to tectonic downwarping and faulting the original lake area had been reduced to one third of the original 13 000 km2 5000 mi2 by the time the delta front prograded to the caldwell area the original lake area may have been sufficient to evaporate most of the inflow and the lake may have only occasionally spilled into other basins diminished area for evaporation later in the history of the lake combined with reduced evaporation accompanying onset of the ice ages may have caused the lake to rise and overtop a basin sill about 2 ma and subsequently deepen hells canyon

regional implications of heat flow of the snake river plain northwestern united states abstract the snake river plain is a major topographic feature of the northwestern united states it marks the track of an upper mantle and crustal melting event that propagated across the area from southwest to northeast at a velocity of about 3 5 cm yr the melting event has the same energetics as a large oceanic hotspot or plume and so the area is the continental analog of an oceanic hotspot track such as the hawaiian island emperor seamount chain thus the unique features of the area reflect the response of a continental lithosphere to a very energetic hotspot the crust is extensively modified by basalt magma emplacement into the crust and by the resulting massive rhyolite volcanism from melted crustal material presently occurring at yellowstone national park the volcanism is associated with little crustal extension heat flow values are high along the margins of the eastern and western snake river plains and there is abundant evidence for low grade geothermal resources associated with regional groundwater systems the regional heat flow pattern in the western snake river plains reflects the influence of crustal scale thermal refraction associated with the large sedimentary basin that has formed there heat flow values in shallow holes in the eastern snake river plains are low due to the snake river plains aquifer an extensive basalt aquifer where water flow rates approach 1 km yr below the aquifer conductive heat flow values are about 100 mw m 2 deep holes in the region suggest a systematic eastward increase in heat flow in the snake river plains from about 75 90 mw m 2 to 90 110 mw m 2 temperatures in the upper crust do not behave similarly because the thermal conductivity of the plio pleistocene sedimentary rocks in the west is lower than that in the volcanic rocks characteristic of the eastern snake river plains extremely high heat loss values averaging 2500 mw m 2 and upper crustal temperatures are characteristic of the yellowstone caldera

argillite debris converted to bauxite during karst weathering evidence from immobile element geochemistry at the olmedo deposit sardinia the olmedo bauxite deposit occurs in the nurra district of northwest sardinia it forms a stratiform horizon in cretaceous limestone and marl uplift in mid cretaceous had exposed recently deposited limestone to karst weathering and a layer of argillaceous debris accumulated on its surface and was partly converted to bauxite intermediate products were desiccated marl bauxitic argillite and argillaceous bauxite subsidence followed and the bauxite was preserved by the deposition of late cretaceous limestone and other sediments uplift in oligocene miocene time with ensuing erosion exposed the bauxite horizon to its present configuration concentrations of normative minerals illustrate chemical processes and the build up of al in the bauxite horizon plots of chemical data and correlation coefficients show that al ti zr nb th cr and v were immobile during the bauxitization process mass changes point to large net removal of si mg and k from the system although some of this material and slightly mobile al were reprecipitated in the underlying argillite and altered marl immobile element ratios trace the source of the bauxite to the underlying argillaceous limestone al in the bauxite was accumulated from the degradation of 25 to 50 m of the argillaceous limestone

seismic imaging through the volcanic rocks of the snake river plain insights from project hotspot hotspot the snake river geothermal drilling project was undertaken to better understand geothermal systems across the snake river plain volcanic province a series of surface and borehole seismic profiles were obtained to provide insights into volcanic stratigraphy and test the capabilities of engineering scale seismic imaging in such terranes the kimberly site drilled through 1 9 km of mostly rhyolite with thin sedimentary interbeds in the upper part of the section the kimama site drilled through 1 9 km of mostly basalt with sedimentary interbeds at 200 m depth and 1700 m depth the mountain home site contained numerous sediment and volcanic rock layers downhole and surface vibroseis seismic results suggest sedimentary interbeds at depth correspond with low velocity high temperature zones that relate to reflections on seismic profiles our results suggest that eruption flow volumes can be estimated and flow boundaries can be imaged with surface seismic methods using relatively high fold and wide angle coverage high frequency attenuation is observed at all sites and this deficit may be countered by acquisition design and a focus on signal processing steps separation of surface and body waves was obtained by muting and the potential for large static effects was identified and addressed in processing an accurate velocity model and lithology contacts derived from borehole information improved the confidence of our seismic interpretations

origin and geochemical evolution from ferrallitized clays to karst bauxite an example from the lower cretaceous of ne spain abstract four outcrops of lower cretaceous barremian karst bauxites located in teruel ne spain were analysed the deposits show a heterogeneous chaotic lithostructure consisting of pisolitic bauxite blocks embedded in lateritic red clays filling karst cavities the research has focused on the geochemical study of major minor and trace elements including some critical to industry of both the bauxites and clays the objective was to investigate the bauxite precursor material and to characterize the system s geochemical evolution geochemical analyses were carried out by inductively coupled plasma optical emission and mass spectroscopy an absolute weathering index has been calculated to estimate element mobility assuming ti as an immobile element and the upper continental crust ucc as parent material further selected samples were observed by field emission scanning electron microscopy the data indicate that both the bauxites and red clays originated by intense chemical weathering from more mafic argillaceous sediments than the ucc ongoing weathering caused the bauxitization of the upper parts of the original profile preventing the lower parts from being bauxitized thus producing the ferrallitized clays underlying the pisolitic bauxites subsequent karst reactivation gave rise to the current lithostructure ferrallitization is related to fe sc and v enrichment on the other hand although bauxites are relatively enriched in some elements compared to clays the more intense chemical weathering associated with bauxitization led to chemical homogenization and widespread element depletion during the bauxitization al ti zr cr and probably hf and the critical element nb behaved as more immobile elements in the system bauxitization also enhanced homogenization and depletion of the ree which is more pronounced for the lree hree trends seem to be partly related to the concentration of ti oxides in the bauxites whereas p bearing phases more frequent in the clays control the lree subsequent to bauxitization partial kaolinization of the bauxite took place related to the circulation of acid solutions that also caused the karst reactivation these late processes caused some al depletion in the bauxites and enhanced fe loss together with v and to a lesser extent ge

transvaporite model of ore genesis and an exploration strategy for new giant ore deposits abstract in the current work we stand for the revival of the transvaporite ore genesis model which was introduced by hungarian academician e szadeczky kardoss more than half a century ago but has now fallen out of favor and superseded by the orthomagmatic model our arguments in support of the transvaporite model are based on the contemporary overpressure theory developed for mesozoic cenozoic petroleum basins we propose a new variant of the transvaporization model whereby the formation of giant ore deposits occurs in the areas where former petroleum rich basins are intersected by large igneous provinces lips at such sites structural magmatic activity leads to hydrocarbon deposits being destroyed and many new ore deposits being created beneath a new regional volcanic fluid seal built by rapidly accumulating up to 3 4 km in 1 ma lava flows in such conditions a zone of significant overpressure that is 1 4 1 8 times higher than hydrostatic pressure develops subsequently under the influence of compressive mechanism of mass transfer gas saturated brines of sedimentary rocks migrate toward intruding melts and then mix with them as a result unusual rocks transvaporites are formed and giant ore deposits created here we review six supergiant ore deposits of various types and ages with different associations of metals and host rocks including the norilsk district in russia cu ni co pt pd el teniente los bronces district in chile cu mo almaden deposit in spain hg ermakovskoe deposit in russia be pebble copper deposit in southern alaska cu mo au and olympic dam deposit in southern australia u cu au ree noting that all listed metals in each and every deposit do reach giant reserves in all these deposits transvaporization appears to play the key role in ore genesis given the 1 short duration of the main ore genesis stage a significant practical implication of the transvaporite model is that it should modify future strategies for ore deposits exploration instead of pursuing just any deposit exploration efforts should focus specifically on giant ore deposits concentrating search efforts at the sites where former petroleum basins have been intersected by lips basin analysis of enriched oil and gas provinces is already being conducted in detail by seismic transects involving two dimensional cross sections and areal surveys followed by three dimensional mapping of productive reservoirs the same strategy should be applied to ore bearing regions but at better precision and accuracy given the smaller velocity contrast in seismic wave propagation in ore rocks compared with oil and gas bearing sedimentary rocks important advances in the ore geology of lips such as geological mapping and gravity and magnetic surveys have already produced significant new data these studies can be divided into two types which first involve a general description of the lip and are then followed by an investigation of major intrusions likely to be directly linked to ore genesis a combination of these investigations into hydrocarbon basins and lips will lay the foundation for transvaporite exploration which will be the key criterion for the successful search for new giant ore deposits

content and mode of occurrences of rare earth elements in the zagrad karstic bauxite deposit niksic area montenegro abstract three vertical sections through the zagrad deposit of jurassic karst bauxite in central montenegro have provided knowledge of the vertical distribution of major and some selected trace elements including rare earth elements ree variations in the mineralogy particularly those hosting ree have been studied this has revealed the presence of authigenic mineral phases such as xenotime mottramite and monazite best proved using raman microprobe analysis as well as residual phases such as zircon titanite and monazite the mobility of the elements during bauxitization processes has been studied to show that the ree minerals ensure progressive concentration of these elements during removal of major elements through weathering the similarity of normalized ree in the bauxite to the typical post archean australian shales paas and upper continental crust ucc profile and the preserved eu anomaly are evidence that the bauxite was not derived from carbonates and represents alteration of shale marly limestone and volcanogenic or proximal igneous sourced detritus that accumulated in the original karst landform mass change during bauxitization using ti as index element and compared to paas composition revealed almost 100 depletion of si and weak enrichment in al deeper parts of the deposit with authigenic minerals exhibit very strong enrichment in all ree the bauxite ores have high ree contents 693 5 6953 4 ppm especially lree contents 582 8 4882 9 ppm while hree contents 106 6 2070 5 ppm are much lower

downward remagnetization of a 74 m thick zone in lake sediments from palaeo lake idaho nw united states locating the gauss matuyama geomagnetic boundary within a dual polarity zone

orebody vertical structure and implications for ore forming processes in the xinxu bauxite deposit western guangxi china abstract the xinxu bauxite orebodies which are contained in quaternary depressions overlying strata of permian to devonian age were formed through the break up oxidation and re sedimentation of a pre existing permian bauxite horizon with progressive karsitification the underlying strata of the quaternary orebodies were eroded out downwards in sequence gradually transiting from permian to devonian thus an older underlying stratum generally infers a higher degree of weathering a total of 47 exploration wells sampled each meter were chosen from several orebodies to evaluate the vertical distribution of four major components al 2 o 3 fe 2 o 3 sio 2 and loss on ignition in the ores the vertical evenness is quantified via a box gliding multifractal model the small width of the multifractal spectrum suggests that the vertical ore quality is even overall indicating an intertwining break up and mixing up processes during evolution of the quaternary orebody although the four components show complex spatial distributions topographic elevation displays a positive relationship with the mean fe 2 o 3 content and a negative correlation with the vertical unevenness of al 2 o 3 and fe 2 o 3 in the wells this is taken to reflect the more uniform oxidizing environment in the higher depressions which facilitates a homogeneous and greater increase of fe 2 o 3 content throughout the orebody in contrast the redox conditions in lower depressions are less oxidizing and varied in space inducing great variation in degree of fe 2 o 3 increase in the ores this study also demonstrates that in the xinxu deposit the ore forming redox environment has more impact on the ore quality than the degree of weathering as the contents show irregular vertical changes in the lower depressions it follows that it is the ancient redox environment rather than the modern conditions which affect the orebody vertical structure this clarifies the fact that the vertical structure of the orebody is jointly constrained by the physical melange accumulation of ores and the differences between the ancient redox environments in the higher and lower locations these factors should be the primary factors affecting the vertical structure of karst bauxite deposits

the formation of representative lateritic weathering covers in south central guangxi southern china the mineralogy and geochemistry have been studied in three representative lateritic weathering covers close to the tropic of cancer guangxi south china with the purpose of studying formation and evolution processes of lateritic covers in this region the x ray diffraction and scanning electron microscope analysis results indicate that the contents particle sizes shapes and structures of secondary minerals such as iron and clay minerals are distinctly different in ferruginous nodular horizon and mottled clay layer of lateritic profiles the ferruginous nodules are characterized by high concentrations of iron and aluminum and low contents of silicon the energy analysis suggests that there are element exchanges between hematite crystal and clay minerals the mass balance calculation results show that there is exogenetic input of iron into lateritic covers especially within the ferruginous nodular horizon compared to the bottom layer of the profile the scanning electron microscope images also confirm that voids and fractures in ferruginous nodules were filled with ferruginous material derived from soil solution this could be a significant interpretation for the negative correlations between fe2o3 and al2o3 the iron and manganese oxides in ferruginous nodular horizon have an apparent effect on the adsorption and precipitation of cerium strontium compared to other alkali metal and alkali earth metal elements concentrates in mottled clay layer variation in the he gt ratio reflected by the o fe ratio in a small ferruginous concretion indicates that climate changes altered aqueous activity of the soil environment finally a model for the formation and evolution of typical lateritic weathering covers in south central guangxi supported by all the data was proposed

geochemical study of laterites of the jamnagar district gujarat india implications on parent rock mineralogy and tectonics abstract the laterite deposits occur in a linear stretch along the northern arabian sea coast in the jamnagar and porbandar districts of gujarat state india these deposits are characterised by presence of gibbsite kaoline calcite quartz anatase natroalunite goethite and hematite and relicts of mafic minerals and plagioclase on the basis of petro mineralogy and geochemistry these deposits are grouped as aluminous laterites fe2o3 1 45 3 84 av 3 13 al2o3 39 31 57 24 av 45 80 and laterites fe2o3 9 84 32 21 av 25 13 al2o3 34 74 49 59 av 41 27 the major trace and ree characteristics of laterites indicate that these were formed in situ by the alteration of parent rocks of trachytic andesitic composition and the process of bauxitisation followed the path of destruction of kaolinite and deferruginisation the correlation patterns of several trace and rare earth elements and their preferential enrichment have indicated that there is an influence of precursor rock on the distribution of trace elements the jamnagar laterite deposits occur as capping over the deccan trap basaltic lava flows and pyroclasic deposits lateritisation prevailed during palaeocene age when india was separated from the seychelles and passing over the equator during this time climate morphology and drainage conditions were favourable for lateritisation that result in the formation of jamnagar and other laterite deposits within the deccan province flood basaltic provinces of deccan columbia north australia and hawaii appear good location for hosting laterite deposits due to their wide areal extent small geological time span and uniform chemical composition however comparison of the major flood basaltic provinces of the world has indicated that their palaeopositions along with palaeoclimate morphology and drainage are equally important factors for facilitating lateritisation

methods of interpretation of borehole falling head tests performed in compacted clay liners the interpretation of falling head tests in cased boreholes is discussed these tests are commonly used to measure hydraulic conductivity of compacted clay liners and are often part of the construction quality assurance program three methods of interpretation are reviewed with data sets collected from real tests two of these methods have been the subject of past research by other authors the hvorslev or time lag method and the velocity method after the limitations of these two approaches have been underlined a third method is proposed it uses a best linear unbiased estimator to fit the theoretical head difference function in a plot of falling water column elevation as a function of time z t method the hvorslev method is found unreliable and is not recommended the velocity method is theoretically sound but statistical uncertainty can become high when this method is used in testing materials with low hydraulic conductivity such as clay liners materials with low hydraulic conductivity tend to

anatase nanoparticles on supergene platinum palladium aggregates from brazil titanium mobility in natural waters abstract supergene aggregates of platinum palladium pt pd intermetallic compounds from the corrego bom sucesso alluvial deposit minas gerais brazil are coated with abundant poorly crystalline nanoparticles of anatase tio 2 the anatase coating is widespread suggesting that the surface of the pt pd grains catalytically destabilised ti which was likely dissolved by organic ligands in the ground waters association of tio 2 nanocrystallites with organic matter further suggests that biogenic processes could have mediated their formation these anatase coated pt pd grains demonstrate an unexpected ti mobility in supergene environments

on the use of the kozeny carman equation to predict the hydraulic conductivity of soils the saturated hydraulic conductivity of a soil can be predicted using empirical relationships capillary models statistical models and hydraulic radius theories a well known relationship between permeability and the properties of pores was proposed by kozeny and later modified by carman the resulting equation is largely known as the kozeny carman kc equation although the two authors never published together in the geotechnical literature there is a large consensus that the kc equation applies to sands but not to clays this view however is supported only by partial demonstration this paper evaluates the background and the validity of the kc equation using laboratory permeability tests test results were taken from publications that provided all of the information needed to make a prediction void ratio and either the measured specific surface for cohesive soils or the gradation curve for noncohesive soils the paper shows how to estimate the specific surface of a noncohesive soil from its g

millennial scale climate changes manifest milankovitch combination tones and hallstatt solar cycles in the devonian greenhouse world sub milankovitch rhythmic features in sedimentary records have been reported from throughout geological time however their origin remains enigmatic in particular during so called greenhouse periods in earth s history to better understand such short term climatic changes we sampled two 3 m thick intervals of early devonian hemipelagic carbonate at 1 cm resolution in the pod barrandovem section czech republic greenhouse conditions prevailed during early devonian times and the chosen resolution enables the detection of millennial scale climate change as recorded by elemental abundances we used a previously published astrochronology for the section to transform the studied series from the stratigraphic into the time domain spectral analysis of the time calibrated log transformed ti records reveal obliquity and precession cycles confirming the applied astrochronology additional spectral peaks with periods of 2 3 2 7 6 8 and 10 12 k y appear in both records furthermore a 1 5 k y periodicity close to the pleistocene dansgaard oeschger oscillation is also identified but only in the record with higher accumulation rate 3 5 cm k y bi coherence spectra reveal that the 6 8 and 10 12 k y periodic components are combination tones of milankovitch cycles we infer the shorter 2 5 k y periodicity to be the result of solar forcing related to the hallstatt cycle these new observations strengthen the case for an external origin of millennial scale features