origins of heavy oils in the erlian basin ne china abstract the erlian basin is located in the central asia mongolian fold belt between the siberian and sino korean cratons it is a mesozoic continental rift basin composed of 52 individual fault depressions the main phase of rifting took place during the early cretaceous when a series of fluvial lacustrine sediments were deposited each depression forms an independent sedimentary system and behaves as an independent petroleum system hydrocarbon source rocks are found in the upper arshan and lower tengger formations these are mainly type ii source rocks and are mainly located in oil generation window at the present day a series of oilfields and commercial oil flows have been found in the basin highlighting its good petroleum potential many of these oils are heavy six oil samples from the anan and ten from the jirgalangtu depressions have been subjected to routine geochemical analytical techniques in order to evaluate the origins the methods used include gas chromatography of the saturated and aromatic hydrocarbon fractions gas chromatography mass spectrometry of the saturated hydrocarbon fraction and stable carbon isotope analyses the trace metal elements of the biodegraded oils from the jirgalangtu depression were also analysed by atomic absorption spectroscopy two types of heavy oils primary and biodegraded were identified on the basis of these data the former includes both immature and mature heavy oils a filtering and spill process was proposed to explain the origin of primary mature heavy oils or tar mat in the anan depression the biodegraded oils from the jirgalangtu depression were ranked and classified in terms of the degree of biodegradation using a series of geochemical parameters based on the gas chromatographic concentrations and biomarker fingerprints of gas chromatography mass spectrometry of the saturated hydrocarbon fraction the relationship between oil saturation and porosity indicates that the heavy oils in the jirgalangtu depression were biodegraded after they accumulated

heavy mineral sands in the eucla basin southern australia deposition and province scale prospectivity the marine eucla basin in southern australia is emerging as a major new heavy minerals province in australia beach placers are associated with a series of partially buried cenozoic coastal barrier sands formed along an arcuate 2 000 km long basin margin the trace of which is up to 320 km inland of the present coastline the presence of high grade deposits with dominant zircon over ilmenite and lesser amounts of rutile and leucoxene was established with the discovery of the jacinth and ambrosia heavy mineral deposits in late 2004 an additional 10 heavy mineral prospects were subsequently identified and are at various stages of evaluation the eucla basin and its adjacent paleovalley system have a large areal extent that contains a complicated succession of marine and nonmarine strata spanning a wide range of depositional environments four distinct constructional phases for the development of shorelines can be recognized and correlated with major third order sea level events established by others from the marine depositional record as occurring during the middle eocene 42 5 ma late middle eocene 39 36 ma late eocene 36 34 ma and miocene pliocene 15 2 6 ma prevailing westerly winds built extensive dune systems by longshore drift sediment movement was from west to east detrital zircon rocks from the ooldea and barton barriers show a distribution of zircon age that is consistent with the proterozoic musgrave province to the north of the basin as the dominant primary source area of the heavy minerals with a contribution from the albany fraser orogen to the west the likelihood is that these heavy minerals have been recycled via sedimentary basins that flank the musgrave province and include the neoproterozoic to cambrian officer basin and permian to mesozoic deposits of the bight basin our current depositional model is summarized as follows 1 initial rapid transgression and deposition of a shallow marine sand sheet subsequently overlain by shallow marine limestone during middle eocene 2 a major eocene transgression and deposition of a shelf barrier and lagoonal shoreface marine complex during the late middle eocene 3 further transgression and highstand deposition during the late eocene 4 renewed transgression of barrier lagoonal and possibly flooding deltaic sand blanket in the southeastern coastal plain with neotectonic uplift tilting in the western eucla margin during mio pliocene time each stage of reworking increased the potential for heavy mineral concentration in placer deposits

mineralogy geochemistry and fluid action process of uranium deposits in the zhiluo formation ordos basin china abstract some controversies still exist regarding the genesis of sandstone type uranium deposits in the northeastern ordos basin herein based on boreholes and well logging data we selected sandstone samples representing different epigenetic alteration environments as the research object and comprehensively utilized polarizing microscopy scanning electron microscopy electron probe analysis elemental analysis and other test methods to research sandstone genesis the main altered minerals in the sandstone of this area include limonite pyrite achavalite carbonate sulfate clay and uranium minerals the complex characteristics of alteration minerals indicate multi stage fluid mixed mineralization in this area according to the relationship between the major elements in different types of sand bodies the components were classified into three groups the first is the reduction media group including cao mno total oxygen carbon toc s u and burning loss the second is the detrital particle group including sio2 k2o and na2o and the third contains the clay and volcano component group including fe2o3 p2o5 tio2 feo mgo and al2o3 among these the content of reduction media is positively correlated with uranium enrichment whereas detrital particles and clay components reflect the influence of alteration on the sand body composition which indirectly affects the uranium adsorption and precipitation through the normalization of rare earth element ree chondrites we find that the distribution patterns of rees in rocks with different geochemical environments show a fractionation of light and heavy rare earth elements hrees a right leaning enrichment of light rare earth elements lrees and relatively flat hree further via the post archean australian shale paas normalization we observe that the mudstone of the zhiluo formation exhibits a relatively flat curve whereas the sandstones have strongly positive eu anomalies the difference in ree values for different types of sand bodies indicates that although all types of rocks have a similar sedimentary environment their original sediments underwent fluid alterations such as oxidation and reduction based on the uranium mineralization evolution history in the study area the water rock reaction process and mineral alteration sequence were determined on the basis of alteration types and elemental concentrations our findings provide new insight into the petrological significance mineralogy and geochemical composition of uranium deposits in the ordos basin

the rhone glacier was smaller than today for most of the holocene we present the development and application of the novel in situ cosmogenic 14 c 10 be chronometer to recently exposed proglacial bedrock of the rhone glacier switzerland results show that during the holocene the glacier was smaller than today for 6500 2000 yr and larger than today for 4500 2000 yr this pattern is consistent with limited data from other techniques for glaciers in the alps and scandinavia but in contrast to glaciers from the southern alps of new zealand emphasizing the high sensitivity of large mountain glaciers to small climate changes the 14 c 10 be chronometer also shows that abrasion rates beneath the rhone glacier increased with ice speed

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

relationships between meso cenozoic denudation in the eastern tian shan and uranium mineralization in the turpan hami basin nw china constraints from apatite fission track study abstract the eastern tian shan tectonic belt located in the southern domain of the central asian orogenic belt consists of the bogda mountain range turpan hami tuha basin and choltagh mountain range from north to south understanding the meso cenozoic denudation history of the eastern tian shan is critical to unravel the genesis of sandstone type uranium u mineralization in the tuha basin in this paper thirteen granite and sandstone samples were collected along two north south transects in the west of the eastern tian shan for apatite fission track thermochronological study the apatite fission track ages obtained in this study in combination with the thermal history modeling results and previous thermochronological data indicate three main episodes of denudation in the eastern tian shan since the mesozoic i e late jurassic to early cretaceous 160 135 ma late cretaceous to early eocene 100 50 ma and late eocene to early miocene 35 20 ma the late cretaceous denudation events are related to the kohistan dras arc accretion collision that affects the tian shan mountain range extensively whereas the cenozoic ones are related to the india asia collision regional distribution of apatite fission track ages in the eastern tian shan and comparison with u mineralization ages in the tuha basin suggest that the choltagh mountain range began to denudate in the late jurassic exposing high u bearing volcanic rocks on the surface and resulting in significant u mineralization in the southern part of the tuha basin in the cretaceous whereas the bogda mountain range in the north did not experience significant denudation until the late eocene due to the relatively low exhumation of the bogda mountain range and limited exposure of u bearing rocks u mineralization in the tuha basin is minor during the cenozoic but the newly deposited sediments helped the preservation of the u deposits that were formed in the cretaceous

a growing sandstone type uranium district in south yili basin nw china as a result of extension of tien shan orogen evidences from geochronology and hydrology abstract the mesozoic yili basin of nw china represents the largest known concentration of u deposits in china and contains five major deposits namely from west to east the 512 kujie ertai 513 511 510 mengqiguer and 509 deposits pre mining resources within the explored sandstone type uranium deposits in this area are reportedly as much as 20 000 t contained u the mineralization is hosted by the middle lower jurassic shuixigou group which from base to top is divided into the badaowan sangonghe and xishanyao formations the u pb isotopic analysis of ores from the kujie ertai and mengqiguer deposits indicate that they contain high and variable amounts of initial common pb meaning that the only possible way to date these deposits is by using u pb isochrons two major stages of uranium mineralization have been identified by the u pb isotope dating of uranium ores in this region the kujie ertai deposit apparently formed between 23 4 3 3 and 20 18 0 49 ma corresponding to a period of crustal thickening and uplift within the tien shan orogen this event 35 21 ma accommodated the majority of the strain generated by the northward collision of the indian plate with the asian plate however the dating of samples from the mengqiguer deposit yielded much younger ages between 0 61 0 24 and 0 347 0 0048 ma the western tien shan mountains expanded until the pliocene as a result of the far field influence of continuous penetration of the indian plate into the asian plate this activated reverse faults and folds in the piedmont of the tien shan mountains and caused the continuous uplift of the southern flank of the yili basin the uplift caused the erosion of anticline hinge zones introducing significant amounts of oxidizing water into the shuixigou group generating a second stage of uranium mineralization hydrological sampling also suggests that the mengqiguer deposit continues to grow indicating a possible third stage of uranium mineralization 0 ma this also indicates that the u within these deposits is derived not only from u bearing sediments but from the tien shan mountains as a result of groundwater cycling the evolution of the u contents of groundwater that was initially derived from cold springs that flow into the mineralized units indicates that these cold springs have an essential role in mobilizing u from the tien shan mountains with rivers flowing through areas of outcropping mineralized units acting as a source of mineralizing fluids during the formation of the mengqiguer deposit

basin related uranium mineral systems in australia a review of critical features abstract this paper reviews critical features of basin related uranium mineral systems in australia these mineral systems include proterozoic unconformity related uranium systems formed predominantly from diagenetic fluids expelled from sandstones overlying the unconformity sandstone hosted uranium systems formed from the influx of oxidised groundwaters through sandstone aquifers and calcrete uranium systems formed from oxidised groundwaters flowing through palaeochannel aquifers sand and calcrete the review uses the so called source pathway trap paradigm to summarise critical features of fertile mineral systems however the scheme is expanded to include information on the geological setting age and relative timing of mineralisation and preservation of mineral systems the critical features are also summarised in three separate tables these features can provide the basis to conduct mineral potential and prospectivity analysis in an area such analysis requires identification of mappable signatures of above mentioned critical features in geological geophysical and geochemical datasets the review of fertile basin related systems shows that these systems require the presence of at least four ingredients a source of leachable uranium and vanadium and potassium for calcrete uranium deposits suitable hydrological architecture enabling connection between the source and the sink site of accumulation physical and chemical sinks or traps and a post mineralisation setting favourable for preservation the review also discusses factors that may control the efficiency of mineral systems assuming that world class deposits result from more efficient mineral systems the review presents a brief discussion of factors which may have controlled the formation of large deposits in the lake frome region in south australia the chu sarysu and syrdarya basins in kazakhstan and calcrete uranium deposits in the yilgarn region western australia

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

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

an excellent fossil wood cell texture with primary uranium minerals at a sandstone hosted roll type uranium deposit nw china abstract a fossil wood cell texture with pitchblende and coffinite found at a sandstone hosted roll type uranium deposit xinjiang nw china is first reported here for the country in the mineralized sandstone detrital grains consisting of quartz feldspar rock fragments carbonaceous trashes mica and accessory minerals were deposited in early turassic time and were cemented by clays and minor authigenic calcite and quartz pitchblende and minor coffinite are principal ore minerals at the deposit and selectively replaced carbonized fossil wood remnants or filled fossil wood cells an excellent fossil wood cell texture with primary uranium minerals formed replacement of organic debris by primary uranium minerals may be due to a local reducing environment resulting from the production of ch 4 h 2 s or h 2 so 3 in its decomposition and a biochemical reaction indicated by the common presence of framboidal pyrite

fault linkage patterns and their control on the formation of the petroleum systems of the erlian basin eastern china abstract fault linkage patterns in rift basins are very common while the process of fault linkage may be very short it changes sedimentation patterns before and after linkage and controls the development of half grabens the propagation and growth of boundary faults can be divided into a simple fault propagation pattern and a fault growth linkage pattern based on structural style sedimentation patterns and oil source correlations in the erlian basin three types of grabens and petroleum systems can be identified the abei graben is controlled by a single boundary fault and forms an independent petroleum system the saihantala graben is controlled by several linked faults which also has an independent petroleum system the wuliyasitai depression controlled by two boundary fault segments which results in two petroleum systems as not all half grabens develop one petroleum system they may therefore have two or more systems the relay ramps between fault segments before linkage are the locations of deposition of sands and conglomerates and consequently are the focus areas for stratigraphic lithologic trap exploration

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

mineral paragenesis and textures associated with sandstone hosted roll front uranium deposits nw china abstract we present a first paragenetic study of the wuyier wuyisan wuyiyi and shihongtan sandstone hosted roll front uranium deposits northwest china the mineralization is hosted by lower middle jurassic coarse to medium grained sandstones which are dark gray to black due to a mixture of ore minerals and carbonaceous debris the sandstone is alluvial fan braided river facies minerals associated with these deposits can be broadly categorized as detrital authigenic and ore stage mineralization ore minerals consist of uraninite and coffinite this is the first noted occurrence of coffinite in this type of deposit in china sulfide minerals associated with the uranium minerals are pyrite marcasite and less commonly sphalerite and galena the sulfide minerals are largely in textural equilibrium with the uranium minerals however these sulfide minerals occasionally appear to predate as well as postdate the uranium minerals this implies that there are multiple generations of sulfides associated with these deposits the ore minerals occur interstitially between fossilized wood cells in the sandstones as well as replace fossilized wood and biotite the deposits are generally low grade primary uranium minerals associated with the low grade deposits are generally too small ranging from 0 2 to 0 3 m in diameter to be observed by optical microscopy and are only observed by electron microscopy mineral paragenesis and textures indicate that these deposits formed under low temperature 30 50 c conditions

the formation of basal type uranium deposits in south central british columbia the basal type uranium deposits in south central british columbia occur within unconsolidated late miocene fluvial paleochannel sediments that overlie major fault zones within the okanagan highlands intrusive complex prior to the formation of mineralization paleovalleys containing host sediments were flooded by pliocene valley basalts of the plateau basalt formation five uranium deposits have been outlined to date of which the blizzard 4 020 metric tons u and tyee 650 metric tons u are the largest the basement intrusive complex underlying the deposits varies in age from early cretaceous to eocene and is comprised of quartz monzonite granodiorite coryell monzonite porphyritic granite and pegmatite all these phases are fractured and altered due to repeated tectonic activity structural analysis of the complex leads to the conclusion that it is a fabric loosened body of interconnecting fault and fracture systems capable of sustaining well developed intermediate and regional ground water flow systems the mineralized host sediments comprise a complex sequence of interfingering conglomerates arkosic sandstones and mudstones organic material is abundant in many but not all mineralized beds uranium mineralization is present in the form of uranous ningyoite or uranyl saleeite autunite phosphates coating clastic grains and filling voids because of very strong reducing conditions related to large concentrations of marcasite and organic material ningyoite is the only uranium mineral in the tyee deposit whereas the blizzard deposit contains a more complex assemblage of minerals saleeite autunite ningyoite the observed paragenetic sequence of mineral precipitation in the blizzard deposit autunite saleeite ningyoite indicates that the uranyl minerals saleeite and autunite are primary small amounts of zn ni co and mo have been introduced into the blizzard deposit whereas mo is the only nonore forming element enriched in the tyee deposit mn is the only depleted element in both deposits the paleoclimate at the time of ore formation was characterized by a temperate climate accompanied by a moderate amount of uniformly distributed precipitation investigations of the source of the ore forming elements u ca mg po 4 including ground water leaching of the intrusive basement rocks volcanic rocks eocene and host sediments as well as emplacement of ore by hydrothermal activity have led to the conclusion that these elements were derived by ground water leaching of the okanagan highlands intrusive complex the deposits are believed to have formed by the infiltration into fluvial sediments of deep seated structurally controlled ground waters that migrated in a well developed regional hydrologic system within the okanagan highlands intrusive complex research indicates that the ore forming ground waters were cold slightly bicarbonated 150 400 ppm highly uraniferous 10 50 ppb and slightly oxidizing dissolved oxygen 2 4 ppm in addition the ore forming ground waters contained sufficient amounts of ca mg and po 4 to account for the observed mineralogy upon entering the host sediments the ground waters were rapidly acidified as the result of the formation of humic acids and oxidation of iron sulfides mineralization formed after a period of extensional tectonism late miocene early pliocene leading to optimum ground water leaching of the intrusive basement complex and prior to a period of epeirogenesis late pliocene pleistocene uplift which resulted in cessation of the ore forming hydrologic regime the maximum period of formation is estimated to be between 4 and 1 m y

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

geological and exploration models of beach placer deposits integrated from case studies of southern australia abstract the processes leading to the formation of beach placer deposits generally begin inland and terminate at the coast including source rocks being weathered eroded and then transported by streams and rivers to the coast where the sediments are deposited in a variety of coastal environments the coastal sediments are reworked by the action of waves tides longshore currents and wind which are effective processes for sorting the mineral grains based on differences in their size and density resulting in laminated or lens shaped packages of sediments up to tens of meters thick that are rich in heavy minerals detailed studies of sedimentary basins as well as peripheral paleo valleys that drained sediment source areas are important tools in the exploration for heavy mineral resources knowledge of the paleo basin associated valley architecture and the source of heavy minerals concentrated in the shorelines and valleys are useful guides to the potential for and location of economic deposits evidence from sedimentology can be combined with that from other geological and geophysical characteristics to arrive at a general reconstruction of basin and paleovalley architecture and depositional environments complex paleogeography of the shorelines can influence or determine the sites of heavy mineral concentration heavy mineral sands tend to concentrate in certain shoreline settings during storm activity repeated storm erosion and reworking over centuries e g the southeastern coast of australia or millennia e g the eucla and murray basins of australia can progressively enrich heavy mineral sand deposits preservation of these deposits over a geological timeframe of millions of years can ensue through subsidence of coastal sediments and during sea level change that results in either shorelines migrating inland marine transgression or seaward marine regression potentially burying or stranding earlier deposits or reworking them to form younger deposits refinements in remote sensing and geophysical techniques data processing sedimentology and computer aided interpretations provide effective economic and efficient methods for modeling coastal reconstructions and for exploring provinces and terrains prospective for heavy mineral sand deposits landscape topography analysis combined with geophysical methods that can resolve physical property contrasts between the shoreline sediments and underlying sequences are increasingly used in mineral exploration to locate and to reconstruct paleoshorelines and paleovalleys australia has modern and ancient beach placer deposits both of which show many similar geologic features the formation of these heavy mineral deposits provides one of the best examples of applying knowledge of modern systems e g the west and east coasts of australia as an analogue to interpret and understand the geology and form of ancient deposits e g the eucla and murray basins of southern australia this study provides descriptive and exploration models of australia s heavy mineral sand deposits formed in coastal environments which can be applied to similar settings worldwide

cainozoic stratigraphy palaeoenvironments and geological evolution of the lake eyre basin abstract for a large part of inland australia weathering and erosion prevailed from the cenomanian to the late paleocene subsidence commencing in the late paleocene produced a depocentre the lake eyre basin in which sedimentation occurred in three main phases 1 fluviolacustrine sand silt clay and carbonaceous horizons from latest paleocene to middle eocene 2 dolomite and magnesium rich clay and sand deposited in extensive shallow alkaline lakes from latest oligocene miocene and 3 red clay silt and sand were deposited in fluvial lacustrine and aeolian settings during the pliocene and quaternary widespread weathering and silicification of sediments occurred in the late eocene oligocene and again in the pliocene the latter also accompanied by ferruginisation the silcrete sheets were folded into broad domes during the oligocene and again in the pliocene when faulting marginal to the southern ranges also occurred from the late paleocene to early eocene the basin supported rainforest growing in megathermal to mesothermal conditions by the middle eocene vegetation had changed to localised riparian forest in valley bottoms and more open sclerophyllous woodland in the hinterland indicating monsoonal conditions for most of this early tertiary interval deposition was by broad braidstreams flowing northwards in the miocene scattered elements of megathermal forest still existed but open woodland was far more extensive strong climatic seasonality and elevated temperatures promoted the deposition of thick dolomites in giant alkaline lakes the lakes and the diverse vegetation were home to a rich aquatic and terrestrial fauna by the pliocene climate was semiarid and vegetation mainly open casuarinaceae dominated woodland with very rare stands of forest confined to edaphically suitable sites increasing aridity during the quaternary was punctuated by pluvial intervals vast lakes formed during the interglacials largely as a result of higher rainfall in queensland drier windier conditions during the glacials particularly the last led to the development of extensive dunefields

cenozoic eucla basin and associated palaeovalleys southern australia climatic and tectonic influences on landscape evolution sedimentation and heavy mineral accumulation abstract the eucla basin including the vast nullarbor plain lies on the margins of the yilgarn musgrave and gawler cratons in southern australia and owes its distinctive landscape to a unique set of interactions between eustatic climatic and tectonic processes over the last 50 ma understanding of the history of the basin and the palaeovalleys that drained from the surrounding cratons are important because they contain major mineral deposits and the sediments derived from them contain remobilised gold uranium and heavy minerals in particular a remarkably preserved palaeoshoreline sequence along the north eastern margin of the eucla basin is highly prospective for heavy mineral placer deposits the record of marine marginal marine estuarine fluvial and lacustrine environments as constrained mainly by an extensive borehole dataset reflects major depositional events during the palaeocene early eocene middle late eocene oligocene early miocene middle miocene early pliocene and pliocene quaternary these events reflect the key role of eustatic sea level variation which during highstands inundated the craton margins flooding palaeovalleys to up to 400 km inboard of the present coastline however a systematic eastward migration of the depocentre across the eucla basin during the neogene together with apparent flow reversals in a number of palaeovalley systems draining the gawler craton suggest that the eucla basin has also been subject to differential vertical movements expressed as a west side up east side down tilting of 100 200 m this differential movement forms part of a broader north down southwest up dynamic topographic tilting of the australian continent associated with relatively fast 6 7 cm yr northward plate motion since fast spreading commenced in the southern ocean at 43 ma we suggest that the evolving dynamic topography field has played a key role in facilitating development of placer deposits largely through multistage eastward reworking of near shore sequences during highstand transgressive cycles on a progressively tilting platform under the influence of persistent westerly weather systems

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

temperature change is the major driver of late glacial and holocene glacier fluctuations in new zealand advance and retreat of temperate glaciers is largely controlled by changes in temperature and precipitation but the relative importance of these drivers is debated numerical modeling of a new zealand glacier reveals that temperature is the dominant control on glacier length we find that a glacial advance dated to ca 13 000 yr b p requires a cooling event of 3 4 c this mid latitude southern hemisphere cooling is similar in magnitude to the antarctic cold reversal in the vostok ice core record and likely to be a response to the same climate signal

the nuheting deposit erlian basin ne china synsedimentary to diagenetic uranium mineralization sedimentary units deposited during the post rift stage of the erlian basin located in northeast china present an alternation of sandstone and mudstone layers this sedimentological architecture is at the origin of confined permeable reservoirs hosting sandstone type uranium deposits the study of the nuheting deposit offered the opportunity to identify synsedimentary early diagenetic uranium concentrations and diagenetic mineralization hosted in mudstone dominated layers of the erlian formation indicating that a stock of uranium was present in the basin prior to the genesis of sandstone hosted uranium deposits therefore this pre existing stock may constitute a significant source of uranium for the formation of roll front deposits present in other parts of the erlian basin detailed petrographic and geochemical study of drill core samples from the nuheting deposit led to the characterization of different stages related to the formation of the uranium ore bodies and allowed to propose a new metallogenic model uranium mineralization of the nuheting deposit is mainly hosted in dark gray silty mudstone of wetland depositional environment of the late cretaceous erlian formation petrographic observations and emp analyses evidenced that a significant amount of uranium was associated with clay minerals interstratmed clays smectite chlorite palygorskyte illite and kaolinite either adsorbed on mineral surfaces as u vi ions or reduced mainly as uo2 nano to microcrystals disseminated in the clayey matrix which corresponds to synsedimentary early diagenetic concentrations trace elements on pyrite analyzed by la icpms petrographic observations and whole rock geochemical data led to the characterization of a diagenetic uranium mineralization high as 1 50 ppm mo 10 500 ppm and se concentrations in the whole rock and the incorporation of these elements in pyrite highlight reducing conditions within the host rocks during the diagenesis of the erlian formation during the early diagenetic stage uranium was either desorbed from clay minerals and organic materials to be reduced or directly reduced and precipitated as p rich coffinite and pitchblende on pyrite crystals during the late diagenetic stage uranium was redistributed in situ and locally deposited mainly as coffinite on pyrites finally an epigenetic stage of cementation was identified with sulfate and carbonate minerals which may enclose some uranium minerals this epigenetic stage of fluid circulation may be responsible for a minor uranium remobilization therefore the nuheting deposit experienced three main stages i a synsedimentary early diagenetic uranium concentration and mineralization ii a late diagenetic in situ uranium remobilization and deposition on pyrite and iii an epigenetic cementation rock eval pyrolysis indicates that the organic matter contained in host rocks of the nuheting deposit is of type iv inherited from land plant and do not contain free hydrocarbons very low s1 therefore our results do not support that migrated hydrocarbons were involved as a reducing agent for uranium mineralization

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

controls on and prospectivity mapping of volcanic type uranium mineralization in the pucheng district nw fujian china abstract a number of volcanic type uranium deposits occur in pucheng district fujian province china structural controls and volcanic rocks clearly explain the uranium mineralization in this area to explore the subtle spatial associations of uranium occurrences with certain geological features these uranium deposits were subjected to l function fry and fractal analyses the results reveal that 1 these deposits are clustered have a bifractal distribution and are spatially parallel to the ne striking faults 2 the regional scale ne striking and prospect scale ne and nw striking faults exhibit significant spatial associations with uranium deposits as illustrated by the fry models 3 intersections of the faults with larger permeability and connectivity promote the mineralization process and 4 the spatial complexities of structures and lithological contacts quantified by the fractal dimension form strong and positive correlations with uranium occurrences and sizes finally by integrating nine spatial evidential layers representing the controlling factors for the occurrence of mineralization the artificial neural network model was applied to map mineral prospectivity for the uranium mineralization the receiver operating characteristics roc curve and the under the roc curve auc were utilized to measure the performance of the prospectivity models the model is highly capable of mapping uranium prospectivity because the auc is greater than 0 5 and close to 1 the prospectivity mapping confirmed that there is significant potential for uranium mineralization in the study area which opens up new avenues for further explorations on uranium deposits in pucheng district

restudy of acid extractable hydrocarbon data from surface geochemical survey in the yimeng uplift of the ordos basin china improvement of geochemical prospecting for hydrocarbons abstract two geochemical surveys were conducted in 1992 and 2000 respectively in the yimeng uplift of the ordos basin china the earlier survey grid had 1 5 km spacing and the later survey grid had 0 5 0 5 km spacing the acid extractable hydrocarbons of both surveys show similar geochemical trends however the anomalies obtained with traditional statistical methods do not correlate with existing oil gas fields this study reveals two problems in the data and their processing the first one is interference caused by the variation of soil composition we applied a wavelet analysis based method to eliminate this interference in the data of the later survey the second is that micro seepage anomalies did not identify existing oil gas fields and seepage anomalies related with faults had not been previously recognized we modified the logic multiplication cluster analysis and applied a multi fractal model and a back propagation artificial neural network to recognize these two types of anomalies that cannot be recognized with typical statistics in the study area the recognized seepage anomalies display a string bead shaped pattern and some are distributed along a large fault in this area the fault is the main pathway for hydrocarbon migration the micro seepage anomalies are ring shaped and are mostly distributed close to the fault they coincide with oil gas field and structure traps therefore reprocessing of existing geochemical data using these new methods can greatly improve their usefulness in hydrocarbon exploration

under pressure clastic dykes in glacial settings abstract clastic dykes are widespread in glacial settings and we provide examples from switzerland patagonia iceland and the antarctic ranging in age from tertiary to recent on the basis of these examples we establish the general characteristics of clastic dykes and proceed to establish the direction of propagation on sedimentological grounds micromorphological analysis reveals that sedimentation in the dykes is ruled by pressure gradients and that ordinary sedimentological rules do not apply clastic dykes act like safety valves in the subglacial hydraulic system their development depends on specific subglacial conditions like water volume and pressure the nature of the bed sediments or bedrock and the hydraulic properties of the bed a number of scenarios for clastic dyke development are presented as there is not just one set of conditions under which they form development of clastic dykes affects glaciodynamics like velocity and surging and landform formation like till thickness and bedrock disruption

a test of the cosmogenic 3he production rate in the south west pacific 39 s calculation of surface exposure ages using in situ cosmogenic nuclides requires accurate knowledge of local production rates here we report the first attempt to calibrate cosmogenic 3he production in the south west pacific region we present a new radiocarbon chronology that precisely dates the emplacement of the murimotu formation a large debris avalanche deposit in central north island new zealand ca 830 m asl 39 s which occurred 10 4 10 6 cal ka bp measurements of cosmogenic 3he in pyroxene separated from large andesitic blocks exposed during this event yield a sea level high latitude production rate of 120 12 atoms g 1 a 1 lm scaling this is consistent with a recent global compilation comprised predominantly of calibration sites located in the northern hemisphere thus we conclude that the globally compiled cosmogenic 3he production rate is valid in the south west pacific using independent proximal calibrations of cosmogenic isotopes 10be and 14c from quartz in new zealand we derive cosmogenic 3he 10be and 3he 14c production ratios of 32 2 3 2 and 10 6 1 6 respectively

the multiple roles of sulfate reducing bacteria and fe ti oxides in the genesis of the bayinwula roll front type uranium deposit erlian basin ne china the bayinwula roll front type uranium deposit is hosted in sandstones of the early cretaceous saihan formation deposited during the postrift stage of the erlian basin in northeast china the present study aims to characterize 1 the roles of sulfate reducing bacteria and 2 the roles of fe ti oxides in the genesis of the bayinwula deposit drill cores of the host sandstone have been investigated with emphasis on petrographic observations whole rock geochemistry and geochemical and or mineralogical study of fe ti oxides iron disulfide uranium minerals emp la icpms and organic matter rock eval pyrolysis the 34 s value has been measured in situ by sims on the different generations of iron disulfide within regional sandstones preore uranium enrichment u mean 30 4 ppm in whole rock was identified on altered fe ti oxides 38 5 of the whole rock u content and constitutes a major source of uranium for the mineralization petrographic observations and rock eval data indicate that organic matter occurring in the host sandstone is mainly inherited from land plants and corresponds to type iii or type iv kerogens organic matter fragments disseminated in sandstones may also contain significant preore uranium concentration framboidal and collomorph ore stage iron disulfides have moderate to high concentrations of as ni and co and have a light sulfur isotope signature characterized by 34 s values from 30 5 to 7 5 suggesting that sulfur originated from bacterial sulfate reduction which was mainly responsible for 1 the liberation of u from fe ti oxides and organic matter 2 the generation of ore stage iron disulfides and 3 the production of a secondary h 2 s rich reducing barrier involved in the reduction of u vi and the precipitation of u iv uranyl and sulfate ions were transported through the host sandstone by low temperature oxygenated groundwater and u iv was precipitated at the redox front as p rich coffinite and ningyoite dominantly as replacement of ore stage iron disulfides which have partly to totally replaced organic matter and fe ti oxides therefore the combined mineralogical geochemical and isotopic characteristics of the bayinwula roll front uranium deposit support the theory that biogenic processes have widely contributed to the genesis of the uranium mineralization

stable isotope composition of siderite as an indicator of the paleoenvironmental history of oil shale lakes the sediments of two eocene oil shale lakes messel graben and eckfeld maar west germany were analyzed with respect to the distribution chemical and stable isotope composition of siderite the data allow a reconstruction of different stages in the sedimentary and early diagenetic history of the lakes in the messel lake siderite formation started when the sedimentation of laminated sapropelic corg rich sediments was already established the early stage of oil shale sedimentation was characterized by pyrite precipitation in the siderite stage the stable isotope composition of the carbonate suggests methanogenesis to have been an important process at the sediment water boundary layer in the eckfeld lake siderite formation started even before sedimentation of the first sapropelic laminae the stable isotopic composition of the carbonate again indicates an anoxic sediment water boundary layer and strong methanogenesis with the expansion of this environment into the deep water mass sapropel sedimentation became established for both sequences the chemistry and stable isotope composition of the siderites correlates with petrographic and paleontological information about climate dependent fluctuations in the ecological chemical and early diagenetic environment the strong relationship of siderite formation to methanogenesis may be explained by the rate of microbial organic matter degradation which governed both methanogenesis and pco2

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

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

evolution of uranium fractionation processes through time driving the secular variation of uranium deposit types uranium deposit types have evolved considerably from the archean to the present the major global drivers were 1 change of geotectonic conditions during the late archean 2 strong increase of atmospheric oxygen from 2 4 to 2 2 ga and 3 development of land plants during the silurian other significant variations of uranium deposit types are related to unique conjunctions of conditions such as those during phosphate sedimentation in the cretaceous earth s uranium fractionation mechanisms evolved through four major periods the first from 4 55 and 3 2 ga corresponds to formation of a thin essentially mafic crust in which the most fractionated trondheimite tonalite granodiorite ttg rocks attained uranium concentrations of at most a few parts per million moreover the uranium being essentially hosted in refractory accessory minerals and free oxygen being absent no uranium deposit could be expected to have formed during this period the second period from about 3 1 to 2 2 ga is characterized by several widespread pulses of highly fractionated potassic granite strongly enriched in u th and k late in this period peraluminous granite was selectively enriched in u and to a lesser extent k these were the first granite and pegmatite magmas able to crystallize high temperature uraninite the erosion of these granitic suites liberated thorium rich uraninite which would then be concentrated in placer deposits along with pyrite and other heavy minerals e g zircon monazite fe ti oxides within huge continental basins e g witwatersrand south africa and bind river canada the lack of free oxygen at that time prevented oxidation of the uraninite which formed the oldest economic uranium deposit types on earth but only during this period the third period from 2 2 to 0 45 ga records increased oxygen to nearly the present atmospheric level tetravalent uranium from uraninite was oxidized to hexavalent uranium forming highly soluble uranyl ions in water uranium was extensively trapped in reduced epicontinental sedimentary successions along with huge quantities of organic matter and phosphates accumulated as a consequence of biological proliferation especially during the late paleoproterozoic a series of uranium deposits formed through redox processes the first of these developed at a formational redox boundary at about 2 0 ga in the oklo area of gabon all known economically significant uranium deposits related to na metasomatism are about 1 8 ga in age the high grade large tonnage unconformity related deposits also formed essentially during the late paleoproterozoic to early mesoproterozoic the last period 0 45 ga present coincided with the colonization of continents by plants the detrital accumulation of plants within continental siliciclastic strata represented intraformational reduced traps for another family of uranium deposits that developed essentially only during this period basal roll front tabular and tectonolithologic types however the increased recognition of hydrocarbon and hydrogen sulfide migration from oil or gas reservoirs during diagenesis suggests potential for sandstone hosted uranium deposits to be found within permeable sandstone older than the silurian large uranium deposits related to high level hydrothermal fluid circulation and those related to evapotranspiration calcretes are only known during this last period of time probably because of their formation in near surface environments with low preservation potential

geomorphic and sedimentary response of rivers to tectonic deformation a brief review and critique of a tool for recognizing subtle epeirogenic deformation in modern and ancient settings abstract rivers are extremely sensitive to subtle changes in their grade caused by tectonic tilting as such recognition of tectonic tilting effects on rivers and their resultant sediments can be a useful tool for identifying the often cryptic warping associated with incipient and smaller scale epeirogenic deformation in both modern and ancient settings tectonic warping may result in either longitudinal parallel to floodplain orientation or lateral normal to floodplain orientation tilting of alluvial river profiles alluvial rivers may respond to deformation of longitudinal profile by 1 deflection around zones of uplift and into zones of subsidence 2 aggradation in backtilted and degradation in foretilted reaches 3 compensation of slope alteration by shifts in channel pattern 4 increase in frequency of overbank flooding for foretilted and decrease for backtilted reaches and 5 increased bedload grain size in foretilted reaches and decreased bedload grain size in backtilted reaches lateral tilting causes down tilt avulsion of streams where tilt rates are high and steady down tilt migration combing where tilt rates are lower each of the above effects may have profound impacts on lithofacies geometry and distribution that may potentially be preserved in the rock record fluvial sedimentary evidence for past tilting is traditionally based on the assumption that depositional features reminiscent of modern fluvial tectonic effects are evidence for past tectonic effects where it is closely associated with historically active structures or where non tectonic causes cannot be invoked however caution must be exercised when using these effects as criteria for past or current tectonic warping as these effects may be caused by non tectonic factors these non tectonic causes must be eliminated before tectonic interpretations are made

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

paleovalley related uranium deposits in australia and china a review of geological and exploration models and methods abstract the features and similarities in the geology of paleovalley related uranium mineralizing systems in australia and china can be used to refine strategies for exploration paleovalley related uranium resources include sandstone lignite and calcrete style deposits that are developed within the host sediments deposited in paleovalleys the paleovalleys incise either crystalline bedrock or older sedimentary rocks and uranium was deposited and concentrated by the influx of oxidized reduced groundwaters flowing in aquifers within the paleovalley fill the critical features of paleovalley related uranium deposits include sediment and uranium sources geological setting depositional environment age and relative timing of mineralization aquifer characteristics availability and distribution of reductants and preservation potential of the uranium mineral system this set of information provides a basis to establish the uranium mineralization model which can then be used to assist with generating targets for uranium exploration and prospectivity analysis of a region with respect to sino australian examples paleovalley related uranium deposits form mostly around the margins of sedimentary basins and the mineralization is commonly hosted within channel fills contained within paleovalleys developed upon or proximal to precambrian crystalline rocks that contain primary uranium sources the deposits that have been well studied show remarkably similar factors that controlled the formation of paleovalley related uranium deposits basement bedrocks with above background 2 8 ppm u levels of uranium 10 100 ppm that are linked to and or incised by paleovalleys are associated with these deposits and are the inferred source of the uranium in these regions extensive fluvial systems developed particularly during mesozoic and cenozoic times uranium from the bedrock was first dispersed into the sediments and then concentrated to form deposits through successive chemical remobilization precipitation and concentration the deposits formed in continental or marginal marine environments and commonly are associated with reduced lithologies containing pyrite and dispersed organic matter and or seams of lignite or show evidence of infiltrated hydrocarbons the mineralization is developed where oxidizing fluids carrying dissolved u reacted with reductants in the sediments geological geophysical and geochemical features of the paleovalleys and related uranium deposits are used to construct models to understand host sediment distribution fluid flow and ore genesis that can assist exploration for paleovalley hosted uranium deposits precise geometric definition of the basin margin and paleovalley architecture is important in identifying exploration targets and improving the effectiveness of drilling refinements in remote sensing geophysical and data processing techniques in combination with sedimentological and depositional interpretations provide an efficient approach for outlining the principal drainage patterns and channel dimensions to help reduce risk an exploration strategy should combine these technologies with a detailed understanding of the physicochemical parameters controlling uranium mobilization precipitation and preservation

genetic models and exploration implication of the paleochannel sandstone type uranium deposits in the erlian basin north china a review and comparative study abstract since the bayanwula uranium deposit was discovered several paleochannel sandstone type uranium deposits have been found in the manite and wulanchabu sub basins of the erlian basin the paleochannel sandstone type uranium deposits in the erlian basin represent important uranium sources in north china the regional geological settings depositional facies and sequences ore bearing sand bodies and uranium source rocks e g granite and sandstones play important roles in the formation of these deposits three styles of paleochannel sandstone type uranium deposits occur in the erlian basin 1 interlayer oxidation style deposit hosted in the braided river sand bodies of the saihan formation and characterized by laterally zoned mineralization 2 phreatic oxidation style deposits hosted in meandering river sand bodies of the saihan formation showing vertically zoned oxidized mineralization 3 superimposed mineralization style deposits hosted in braided river sand bodies of the saihan formation characterized by an oxidized zone from fluvial channel center to margin which was then overprinted by hydrothermal fluids these three styles of the uranium deposits depend on depositional microfacies and development of deep seated faults which can be used to locate the mineralization and exploration targets within the erlian basin

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

glacier retreat in new zealand during the younger dryas stadial the younger dryas a period of sudden cooling in the northern hemisphere about 12 900 years ago is perhaps the best known example of abrupt climate change but the global extent of the younger dryas is a topic of intense debate particularly in the record of glacial behaviour in new zealand a new reconstruction of the growth and retreat patterns of glaciers in the southern alps in new zealand at the time of the younger dryas supports the suggestion that temperature reductions in the north caused warming and glacial retreat in the southern hemisphere through a series of climate feedbacks the younger dryas during which northern hemisphere temperatures cooled drastically in just a few years is perhaps the best known example of abrupt climate change but its global extent is under debate particularly in the record of glacial behaviour in new zealand these authors present evidence for glacial retreat in new zealand during the younger dryas supporting the hypothesis that northern hemisphere climate changes caused southern hemisphere warming through a series of climate feedbacks millennial scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions the presence of the younger dryas stadial 12 9 to 11 7 kyr ago is established throughout much of the northern hemisphere but the global timing nature and extent of the event are not well established evidence in mid to low latitudes of the southern hemisphere in particular has remained perplexing1 2 3 4 5 6 the debate has in part focused on the behaviour of mountain glaciers in new zealand where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent1 2 3 the interhemispheric behaviour of the climate system during the younger dryas thus remains an open question fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period here we show that new zealand s glaciers retreated after 13 kyr bp at the onset of the younger dryas and in general over the subsequent 1 5 kyr period our evidence is based on detailed landform mapping a high precision 10be chronology7 and reconstruction of former ice extents and snow lines from well preserved cirque moraines our late glacial glacier chronology matches climatic trends in antarctica southern ocean behaviour and variations in atmospheric co2 the evidence points to a distinct warming of the southern mid latitude atmosphere during the younger dryas and a close coupling between new zealand s cryosphere and southern high latitude climate these findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the north atlantic led to a strong interhemispheric thermal gradient8 during late glacial times in turn leading to increased upwelling and co2 release from the southern ocean9 thereby triggering southern hemisphere warming during the northern younger dryas

the sandstone hosted beverley uranium deposit lake frome basin south australia mineralogy geochemistry and a time constrained model for its genesis the sandstone hosted beverley uranium deposit is located in terrestrial sediments in the lake frome basin in the north flinders ranges south australia the deposit is 13 km from the u rich mesoproterozoic basement of the mount painter inlier which is being uplifted 100 to 200 m above the basin by neotectonic activity that probably initiated in the early pliocene the mineralization was deposited mainly in organic matter poor miocene lacustrine sands and partly in the underlying reductive strata comprising organic matter rich clays and silts the bulk of the mineralization consists of coffinite and or uraninite nodules growing around co rich pyrite with an s isotope composition 34 s 1 0 0 3 suggestive of an early diagenetic lacustrine origin in contrast authigenic sulfides in the bulk of the sediments have a negative s isotope signature 34 s ranges from 26 2 to 35 5 indicative of an origin via bacterially mediated sulfate reduction minor amounts of zn bearing native copper and native lead also support the presence of specific reducing microenvironments in the ore zone small amounts of carnotite are associated with the coffinite ore and also occur beneath a paleosoil horizon overlying the uranium deposit provenance studies suggest that the host miocene sediments were derived from the reworking of early cretaceous glacial or glaciolacustrine sediments ultimately derived from paleozoic terranes in eastern australia in contrast the overlying pliocene strata were in part derived from the mesoproterozoic basement inlier mass balance and geochemical data confirm that granites of the mount painter domain were the ultimate source of u and ree at beverley u pb dating of coffinite and carnotite suggest that the u mineralization is pliocene 6 7 3 4 ma the suitability of the beverley deposit for efficient mining via in situ leaching and hence its economic value are determined by the nature of the hosting sand unit which provides the permeability and low reactivity required for high fluid flow and low chemical consumption these favorable sedimentologic and geometrical features result from a complex conjunction of factors including deposition in lacustrine shore environment reworking of angular sands of glacial origin deep pliocene weathering and proximity to an active fault exposing extremely u rich rocks

late glacial and holocene glacier fluctuations in north island new zealand abstract geological records of past glacier extent can yield important constraints on the timing and magnitude of pre historic climate change here we present a cosmogenic 3he moraine chronology from mt ruapehu in central north island new zealand that records fluctuations of new zealand s northernmost glaciers over the last 14 000 years in the mangaehuehu glacier catchment exposure ages and geomorphic observations at our most distal moraine site relative to the current glacier margin show that glacial retreat during the last glacial termination was interrupted by one or more readvances between 14 and 11 ka further up valley moraine boulders deposited at 4 5 ka indicate that glaciers were more extensive during the mid holocene than at any later time the youngest exposure ages in our study 150 450 years constrain the formation of moraines situated within 500 m from the present day mangaehuehu glacier terminus these ages are in agreement with historic sources that show the glacier close to these moraine limits approximately 100 years ago overall our data show that glaciers on mt ruapehu retreated c 3 km since 14 ka in response to a net rise in the local equlibrium line altitude of c 400 m the magnitude of post industrial snowline rise and glacier retreat on mt ruapehu is also consistent with instrumental temperature data that record approximately 0 9 c of warming during the 20th century

petrography and geochemistry of granitoids from the samphire pluton south australia implications for uranium mineralisation in overlying sediments abstract the blackbush uranium deposit jorc inferred resource 12 580 tonnes u located on the north eastern eyre peninsula is currently the only sediment hosted u deposit investigated in detail in the gawler craton uranium is hosted within eocene sandstone of the kanaka beds overlying mesoproterozoic granites of the samphire pluton affiliated with the hiltaba intrusive suite 1 6 ga these are considered the most probable source rocks for uranium mineralisation by constraining the petrography and mineralogy of the granites insights into the post emplacement evolution can be gained which may provide an exploration indicator for other sediment hosted uranium systems three geochemically distinct granite types were identified in the samphire pluton and correspond to domains interpreted from geophysical data all granites show complex alteration overprints and textures with increasing intensity closer to the deposit as well as crosscutting veining alkali feldspar has been replaced by porous k feldspar and albite and plagioclase is overprinted by an assemblage of porous albite sericite calc silicates prehnite pumpellyite and epidote this style of feldspar alteration is regionally widespread and known from hiltaba aged granites associated with iron oxide copper gold mineralisation at olympic dam and in the moonta wallaroo region in two granite types biotite is replaced by calcic garnet calc silicates are indicative of ca metasomatism sourced from the anorthite component of altered plagioclase minor clay alteration of feldspars is present in all samples mineral assemblages in veins include quartz hematite hematite coffinite fluorite quartz and clay minerals minor chlorite and sericite are found in all vein types all granite types are anomalously rich in u concentrations between 10 and 81 ppm highly variable th u ratios as well as hydrothermal u minerals mostly coffinite in granites and veins are clear evidence for u mobility uranium may have been preconcentrated in veins in the upper parts of the pluton and was subsequently leached after deposition of the sediment