key trends in the resource sustainability of platinum group elements abstract platinum group elements pges are increasingly used in a variety of environmentally related technologies such as chemical process catalysts catalytic converters for vehicle exhaust control hydrogen fuel cells electronic components and a variety of specialty medical uses amongst others almost all of which have strong expected growth to meet environmental and technological challenges this century economic geologists have been arguing on the case of abundant geologic resources of pges for some time while others still raise concerns about long term supply yet there remains no detailed analysis of formally reported mineral resources and key trends in the pges sector this paper presents such a detailed review of the pges sector including detailed mine production statistics and mineral resources by principal ore types providing an authoritative case study on the resource sustainability for a group of elements which are uniquely concentrated in a select few regions of the earth the methodology compiled data sets and trends provide strong assurance on the contribution that pges can make to the key sustainability and technology challenges of the 21st century such as energy and pollution control

gravity data as a tool for landfill study this paper shows the potential of gravity data to map a buried landfill bottom topography to this end a gravity inversion method is presented for estimating the landfill s bottom depths at discrete points assuming a decrease of the density contrast with depth according to a hyperbolic law the method s efficiency was tested using synthetic data from simulated waste landfills producing estimated bottom topographies very close to the true ones the method s potentiality has been further evaluated in applying it to the gravity data from the abandoned thomas farm landfill site indiana usa whose bottom topography is known the estimated topography showed close agreement with the known thomas farm landfill s bottom topography

platinum in earth surface environments platinum pt is a rare precious metal that is a strategic commodity for industries in many countries the demand for pt has more than doubled in the last 30years due to its role in the catalytic conversion of co hydrocarbons and nox in modern automobiles to explore for new pt deposits process ores and deal with ecotoxicological effects of pt mining and usage the fundamental processes and pathways of pt dispersion and re concentration in surface environments need to be understood hence the aim of this review is to develop a synergistic model for the cycling of pt in earth surface environments this is achieved by integrating the geological biogeo chemical literature which focuses on naturally occurring pt mobility around ore deposits with the environmental ecotoxicological literature dealing with anthropogenic pt dispersion in pt deposits pt occurs as sulfide telluride and arsenide native metal and alloyed to other pges and iron fe increased mining and utilization of pt combined with the burning of fossil fuels have led to the dispersion of pt containing nano and micro particles hence soils and sediments in industrialized areas urban environments and along major roads are now commonly pt enriched platinum minerals nuggets and anthropogenic particles are transformed by physical and bio geochemical processes complexation of pt ions with chloride thiosulfate ammonium cyanide low and high molecular weight organic acids lmwoas and hmwoas and siderophores can facilitate pt mobilization iron oxides clays organic matter and micro biota are known to sequester pt complexes and particles microbes and plants are capable of bioaccumulating and reductively precipitating mobile pt complexes bioaccumulation can lead to toxic effects on plants and animals including humans bio mineralization in organic matter rich sediments can lead to the formation of secondary pt particles and grains ultimately pt is enriched in oceanic sediments where pt is commonly concentrated in manganese mn oxides when these sediments are subducted pt re enters the magmatic cycle in conclusion this review demonstrates that geological geochemical as well as biological and most recently anthropological processes are strongly interlinked in driving the cycling of pt in surface environments

evolution of cupido and coahuila carbonate platforms early cretaceous northeastern mexico the cupido and coahuila platforms of northeastern mexico are part of the extensive carbonate platform system that rimmed the ancestral gulf of mexico during barremian to albian time exposures of cupido and coahuila lithofacies in several mountain ranges spanning an 80 000 km 2 area reveal information about platform morphology and composition paleoenvironmental relations and the chronology of platform evolution new biostratigraphic data integrated with carbon and strontium isotope stratigraphy significantly improve chronostratigraphic relations across the region these data substantially change previous age assignments of several formations and force a revision of the longstanding stratigraphy in the region the revised stratigraphy and enhanced time control combined with regional facies associations allow the construction of cross sections isopach maps and timeslice paleogeographic maps that collectively document platform morphology and evolution the orientation of the cupido barremianaptian shelf margin was controlled by the emergent coahuila basement block to the northwest the south facing margin is a highenergy grainstone shoal whereas the margin facing the ancestral gulf of mexico to the east is a discontinuous rudist coral reef a broad shelf lagoon developed in the lee of the cupido margin where as much as 660 m of cyclic peritidal deposits accumulated during middle to late aptian time a major phase of flooding forced a retrograde backstep of the cupido platform shifting the locus of shallow marine sedimentation northwestward toward the coahuila block this diachronous flooding event records both the demise of the cupido shelf and the consequent initiation of the coahuila ramp the backstepped coahuila ramp aptianalbian consisted of a shallow shoal margin separating an interior evaporitic lagoon from a low energy muddy deep ramp more than 500 m of cyclic carbonates and evaporites accumulated in the evaporitic lagoon during early to middle albian time restriction of the platform interior dissipated by middle to late albian time with the deposition of peloidal miliolid rich packstones and grainstones of the aurora formation the coahuila platform was drowned during latest albian to early cenomanian time and the deep water laminites of the cuesta del cura formation were deposited this study fills in a substantial gap in the cretaceous paleogeography of the eastern gulf of mexico coast improving regional correlations with adjacent hydrocarbon rich platforms the enhanced temporal relations and chronology of events recorded in the cupido and coahuila platforms significantly improve global correlations with coeval economically important platforms worldwide perhaps con

focused ion beam fib combined with sem and tem advanced analytical tools for studies of chemical composition microstructure and crystal structure in geomaterials on a nanometre scale abstract in order to make meaningful interpretations of trace element and isotopic information from geomaterials prior characterization of the material of interest with respect to structural and chemical homogeneity radiation damage and microstructure is often required transmission electron microscopy tem is a powerful analytical tool that may be used to fully characterise a wide range of synthetic and natural materials the focused ion beam technique fib is an ideal tool for tem sample preparation that allows for the fabrication of electron transparent foils with typical dimensions of 15 10 0 150 m from any region of interest i e site specific and in virtually any material fib sample preparation consumes only a small volume of material approximately 2300 m 3 for a standard foil with the dimensions 15 10 0 150 m leaving most of the material essentially unaffected by the sampling process modern tem facilitates the measurement of chemical composition with unsurpassed spatial resolution e g nanometer scale high resolution imaging and electron diffraction provide important complimentary structural information it is the combination of crystal structure information and chemical composition that allows for the complete characterization of the volume of interest high resolution elemental mapping or line scans may be used to acquire complete energy dispersive x ray analysis edx spectra of a material pixel by pixel subsequent evaluation of the data allows for the correlation of the edx spectrum with the respective elemental map or line scan with an image thus illustrating spatially resolved chemical composition variations at the 0 5 1 0 wt level frequently minerals enclose sub micrometer or even nanometre sized inclusions of minerals fluids or silicate melt which are of great interest to geoscientists nanoinclusions e g in diamond or olivine are of particular interest because they may have preserved their original crystal structure thus providing a geobarometer recording the pressure conditions at the time of formation of the inclusion fib tem are appropriate techniques to sample and subsequently define the chemical composition and the structural state of mineral inclusion on the nanometre scale the combination of fib with an sem allows for 3d information to be obtained from samples including 3d imaging e g phase distribution and volume of the individual phases in symplectites 3d distribution of elements in a specific volume 3d elemental maps and three dimensional texture analysis using electron backscatter diffraction ebsd

stratigraphy and provenance of strata along the san marcos fault central coahuila mexico stratigraphic and petrologic studies supported by geologic mapping north of the san marcos fault central coahuila indicate that as much as 3 000 m of coarse upper jurassic and lower cretaceous detritus was derived from south of the fault two coarse jurassic submarine conglomerate units las palomas and sierra el granizo beds of the la casita formation reflect separate episodes of displacement younger jurassic eolianite and marine sandstone colorado and tanque cuatro palmas beds of the la casita formation record subsequent tithonian fault inactivity neocomian rejuvenation of the fault produced alluvial deposits san marcos formation finer grained paralic or marine strata that are distal and suprajacent and manifest the same faulting are the la mula formation interruption of neocomian displacement is indicated by a tongue of carbonate padilla and barril viejo formations that divides the san marcos into upper and lower members the principal source of this detritus was the wildflysch of the late paleozoic arcproximal las delicias basin and the plutonic rocks that cut it rb sr ages on clasts and from outcrops of granitic rocks are triassic and probably reflect late stage magmatism within the las delicias arc although this arc supplied most of the detritus to the las delicias basin devonian ages on some clasts reveal that an unknown source area lay somewhere nearby during the late part of the paleozoic era the san marcos fault may have served as part of the system of transform faults that connected sea floor spreading ridges of the atlantic with those of the pacific if so then the jurassic units record periods of jurassic activity and inactivity of that system neocomian displacment may have been caused by subsequent isostatic adjustment

integrated high resolution geophysical investigations as potential tools for water resource investigations in karst terrain karstic aquifers can be particularly vulnerable to both pollution from surface activities and large scale dewatering from mineral winning operations this is because of the enhanced vertical and lateral flow paths resulting from the dissolution of carbonate species by rainfall often this process results in the development of voids that can range in size from several centimetres to several tens of metres to date groundwater vulnerability maps for england and wales including karst areas have been produced using a methodology that does not consider the presence of karst features the uncertainties that are presented by the potential for pollution by the presence of water carrying conduits in karst areas where there are proposed or existing limestone quarries require new techniques for detecting and delineating underground cave systems in order for any mapping technique to provide an acceptable assessment of vulnerability the location and spatial distribution of high permeability flow paths need to be established of the available geophysics techniques that may allow for the identification of such features microgravity and resistivity imaging are likely to be the most successful microgravity surveying has the potential to identify the presence and location of such voids and with the integration of electrical tomographic work can provide targets for the location of monitoring boreholes whilst these techniques are intensive and may not be cost effective on a regional scale they do have the potential to provide high resolution data over smaller areas which would be invaluable to any site or area specific assessment of vulnerability

the in vitro growth of gold grains gold colloids octahedral platelets and foils directly and indirectly formed from the reduction of soluble au i thiosulfate and au iii chloride complexes by iron oxidizing bacteria cyanobacteria and sulfate reducing bacteria were combined in an experimental system this system represented simplified biogeochemical conditions occurring within a fluvial environment in which placer au could occur in this study biofilm formation and physical aggregation i e sedimentation processes were critical for the accumulation of nanometer to micrometer sized au particles into grains 4 5 mm in size characterization of grain surface textures by scanning electron microscopy in association with monitoring soluble au concentrations over time suggested that dissolution and reprecipitation processes were occurring at the au grain fluid interface this laboratory model demonstrates that the biogeochemical cycling of au can contribute to the formation of anomalous enrichments such as placer au deposits

cmip5 temperature biases and 21st century warming around the antarctic coast projections of ice sheet mass balance require regional ocean warming projections derived from atmosphere ocean general circulation models aogcms however the coarse resolution of aogcms 1 may lead to systematic or aogcm specific biases and 2 makes it difficult to identify relevant water masses here we employ a large scale metric of antarctic shelf bottom water asbw to investigate circum antarctic temperature biases and warming projections in 19 different coupled model intercomparison project phase 5 cmip5 aogcms forced with two different representative concentration pathways rcps for high emissions rcp 8 5 the ensemble mean 21st century asbw warming is 0 66 0 74 and 0 58 c for the amundsen ross and weddell seas as rs and ws respectively rcp 2 6 ensemble mean projections are substantially lower 0 21 0 26 and 0 19 c all distributions of regional asbw warming are positively skewed for rcp 8 5 four aogcms project warming of greater than 1 8 c in the rs across the ensemble there is a strong rcp independent correlation between ws and rs warming as warming is more closely linked to warming in the southern ocean we discuss possible physical mechanisms underlying the spatial patterns of warming and highlight implications of these results on strategies for forcing ice sheet mass balance projections

weathering of pge sulfides and pt fe alloys in the freetown layered complex sierra leone fresh and weathered rocks and saprolite from horizon b of the freetown layered complex contain platinum group minerals pgm the pgm in the fresh rocks are 1 7 m across including cooperite pts isoferroplatinum pt3fe minor tetraferroplatinum ptfe tulameenite pt2fecu os bearing laurite rus2 and other base metal sulfide bms bearing pgm the weathered rocks contain fewer of those pgm but a high proportion of disordered cu pd bearing pt fe alloys the saprolite hosts scarce smaller 1 3 m ordered ptfe and disordered ptfe3 the pt fe alloys became increasingly fe rich as weathering proceeded pt fe oxides appeared during weathering copper sulfides associated with the primary pgm and cooperite with 3 pd were destroyed to provide the minor cu and pd found in some of the disordered pt fe alloys platinum and pd bearing saprolites have retained the original rock fabric and to a depth of about 2 m surround residual rocks that show progressive weathering corestones ground water passing through the saprolite has transported pt and pd and probably au in solution down slope into saprolite over unmineralized rocks transport is marked by changes in the pt pd ratio indicating that the metals have moved independently palladium is present in marginally higher concentrations in the deeper saprolite than in the corestones suggesting some retention of pd in the deeper saprolite platinum and pd are less concentrated in the upper saprolite than the deeper saprolite indicating surface leaching alteration occurred over a long period in an organic and microbial rich environment that may have contributed to the leaching and transport of pge

foreland basement involved structures basement involved structures commonly occur as long irregular chains of uplifts in foreland basins these structures commonly contain significant hydrocarbon accumulations with most major fields located on the broad crests of these structures the search for complex traps in deeper targets and in subthrust structures requires an improved understanding of the geometry and evolution of these structures characteristic features of basement structures include deformation zones within the sedimentary cover that dissipate significant fault slip and gently dipping frontlimbs and backlimbs fault slip in the basement is usually accommodated in the cover by a triangular widening upward deformation zone on the forelimb with the nature of deformation controlled primarily by the mechanical stratigraphy if the cover contains interlayered competent and incompetent units the incompetent units are characterized by significant penetrative deformation whereas the competent units are faulted after a relatively small amount of penetrative deformation depending on the competency contrast between the basement and cover the nature of basement and the physical conditions of deformation the deformation zone may also propagate downward into the basement gently dipping backlimb and frontlimb panels are related to movement of the hanging wall over synclinal and anticlinal bends in the major fault respectively many basement faults are characterized by a number of synclinal fault bends within the basement which result in long and gently dipping backlimbs forelimb panels are related to anticlinal bends that typically occur at the basement cover interface as well as at one or more locations in the sedimentary cover case studies of well constrained examples of structures from the bighorn and uinta basins and the central basin platform demonstrate the development of these characteristic features and their strong dependence on the mechanical stratigraphy these models and case studies will be useful in interpreting foreland basement structures in areas with poor or limited data

surface transformations of platinum grains from fifield new south wales australia a growing literature is demonstrating that platinum pt is transformed under surface conditions yet bio geochemical processes at the nugget soil solution interface are incompletely understood the reactivity of pt exposed to earth surface weathering conditions highlighted by this study may improve our ability to track its movement in natural systems e g focusing on nanoparticles as a strategy for searching for new undiscovered sources of this precious metal to study dissolution re precipitation processes of pt and associated elements grains of pt fe alloy were collected from a soil placer deposit at the fifield pt field australia optical and electron microscopy revealed morphologies indicative of physical transport as well as chemical weathering dissolution pits cavities striations colloidal nano particles and aggregates of secondary pt platelets as well as acicular iron fe hydroxide coatings were observed fib sem ebsd combined with s m xrf of a sectioned grain showed a fine layer of up to 5 mm thick composed of refined aggregates of 0 2 to 2 mm sized crystalline secondary pt overlying more coarsely crystalline pt fe alloy of primary magmatic origin these results confirm that pt is affected by geochemical transformations in supergene environments structural and chemical signatures of grains surfaces rims and cores are linked to the grains primary and secondary trans formational histories and pt mobility can occur under earth surface conditions intuitively this nanophase pt can disperse much further from primary sources of ore than previously thought this considerable mineral reactivity demonstrates that the formation and or release of pt nanoparticles needs to be measured and incorporated into exploration geochemistry programs

control of regional structural styles and faulting on northeast mexico spring distribution groundwater dependent spring fed ecosystems of the cuatrocienegas basin coahuila mexico host 70 endemic species these desert springs occur primarily aligned along the base of an anticline that bisects the cuatrocienegas basin but the hydrogeologic controls of the springs are poorly understood the hypothesis that spring locations are controlled by subsurface geology such as buried anticlines or faulting versus stratigraphic controls is tested by evaluating 1 regional structural styles 2 fracture models of analogous structures 3 hydrogeologic data and 4 geophysical surveys jurassic and cretaceous siliciclastic and carbonate rocks deposited on the coahuila block west of the cuatrocienegas basin have dips 10 and lack faults because of a structurally rigid granodiorite basement to the east of the coahuila block and around the cuatrocienegas basin the coahuila folded belt has anticlines associated with basement involved faults 10 25 backlimb dips and forelimb dips up to vertical or slightly overturned springs in the western sub basin that represent 85 of total basin discharge are located on zones of highest anticipated fracture density predicted by fracture models of analogous anticlines spring waters reveal elevated temperature 32 35 c and low tritium 1 tritium unit gravimetry and time domain electromagnetic surveys correspond with a best fit cuatrocienegas basin hydrogeologic model of fractures associated with reverse faulting controlling spring locations in the western cuatrocienegas basin springs in the eastern sub basin are located where ephemeral streams have eroded through confining beds along the base of alluvial fans and lack faulting regional variations in structural style are an important control on the location of springs in the cuatrocienegas basin

supergene neoformation of pt ir fe ni alloys multistage grains explain nugget formation in ni laterites ni laterites from the dominican republic host rare but extremely platinum group element pge rich chromitites up to 17 5 ppm without economic significance these chromitites occur either included in saprolite beneath the mg discontinuity or as floating chromitites within limonite above the mg discontinuity both chromitite types have similar iridium group pge ipge enriched chondrite normalized patterns however chromitites included in limonite show a pronounced positive pt anomaly investigation of heavy mineral concentrates obtained via hydroseparation techniques led to the discovery of multistage pge grains i os ru fe ir grains of porous appearance are overgrown by ii ni fe ir and ir fe ni pt phases which are overgrown by iii pt ir fe ni mineral phases whereas ir dominated overgrowths prevail in chromitites from the saprolite pt dominated overgrowths are observed within floating chromitites the following formation model for multistage pge grains is discussed i hypogene platinum group minerals pgm e g laurite are transformed to secondary pgm by desulphurization during serpentinization ii at the stages of serpentinization and or at the early stages of lateritization ir is mobilized and recrystallizes on porous surfaces of secondary pgm serving as a natural catalyst and iii at the late stages of lateritization biogenic mediated neoformation and accumulation of pt ir fe ni nanoparticles occurs the evidence presented in this work demonstrates that in situ growth of pt ir fe ni alloy nuggets of isometric symmetry is possible within ni laterites from the dominican republic

combining outcrop data and three dimensional structural models to characterize fractured reservoirs an example from wyoming combining a detailed outcrop characterization of fracture and fault occurrence with attributes from a three dimensional model of an anticlinally folded clastic reservoir body we determine which characteristics of the structural form and evolution are most closely related to the development of important reservoir scale structures our example reservoir body studied is the frontier formation 1 sandstone in oil mountain an asymmetric anticline on the western flank of casper arch in central wyoming the three dimensional model of the structure was constructed using an iterative scheme designed to maximize interpretation accuracy and precision the model was analyzed to determine the spatial variance in morphologic and kinematic attributes using a quantitative testing approach we found that the intensity of tectonically produced fractures is closely related spatially to rate of dip change and total curvature with the former having the strongest correlation this folding is a low strain process compared to tear faulting which has the strongest spatial correlation to larger strains the location and magnitude of these higher strain areas can be adequately predicted by three dimensional restoration and forward modeling of the upper bounding surface of the reservoir body we use these results to build a predictive model for fault and fracture distribution at oil mountain and to discuss how this approach can aid in the exploitation of analogous producing reservoirs

structural models of faulted detachment folds faulted detachment folds represent a common structural style in several hydrocarbon producing fold and thrust belts including the zagros idaho wyoming utah carpathian and albanide belts and several deep water fold belts including the mississippi fan and per dido belts these structures form in units with high competency contrasts and display a transition in deformational behavior from detachment folding to progressive fault propagation with increasing shortening the structures first form by symmetric or asymmetric detachment folding with the fold wavelength controlled by the thickness of the dominant units volumetric constraints require the movement of material from the synclines to the anticlines contin ued shortening results in tighter folds with limb rotation by hinge migration limb segment rotation and internal shear rotation of limb segments between locked hinges results in thrust faults which propagate through deformation zones on the frontlimb and possibly the backlimb the faults may terminate both up and down section within brittle or ductile deformation zones eventually a through going fault connects one of the major faults with the basal detach ment variations in the structural geometry are related to the rela tive thickness and competency of the units and the mechanisms of deformation because faulted detachment folds superficially resem ble fault propagation folds their geometry can be misinterpreted in areas of poor data quality characteristic features for distinguish ing these structures include 1 smaller variations in anticlinal length during fold evolution 2 a more open and rounded fold geometry 3 complex and nonuniform variations in fault slip 4 a significant variation in deformational behavior among different units and 5 fold fault relationships indicating transition from folding to faulting such as footwall synclines and decapitated fold geometries

uncovering framboidal pyrite biogenicity using nano scale cnorg mapping framboidal pyrite has been used as a paleo redox proxy and a biomarker in ancient sediments but the interpretation of pyrite framboids can be controversial especially where later overgrowths have obscured primary textures here we show how nano scale chemical mapping of organic carbon and nitrogen cn org can detect relict framboids within precambrian pyrite grains and determine their formation mechanism pyrite grains associated with an ediacaran fossil lagerstatte from newfoundland ca 560 ma hold significance for our understanding of taphonomy and redox history of the earliest macrofossil assemblages they show distinct chemical zoning with respect to cn org relict framboids are revealed as spheroidal zones within larger pyrite grains whereby pure pyrite microcrystals are enclosed by a mesh like matrix of pyrite possessing elevated cn org replicating observations from framboids growing within modern biofilms subsequent pyrite overgrowths also incorporated cn org from biofilms with concentric cn org zoning showing that the availability of cn org progressively decreased during later pyrite growth multiple framboids are commonly cemented together by these overgrowths to form larger grains with relict framboids only detectable in cn org maps in situ sulfur isotope data 34 s 24 to 15 show that the source of sulfur for the pyrite was also biologically mediated most likely via a sulfate reducing microbial metabolism within the biofilms relict framboids have significantly smaller diameters than the pyrite grains that enclose them suggesting that the use of framboid diameters to infer water column paleo redox conditions should be approached with caution this work shows that pyrite framboids have formed within organic biofilms for at least 560 m y and provides a novel methodology that could readily be extended to search for such biomarkers in older rocks and potentially on other planets

geometric analysis of hybrid fault propagation detachment folds abstract fault propagation folds and many detachment folds may be analyzed using a single geometric model a modification of a previously published approach allows the interpreter to quantitatively predict thrust fault trajectory and displacement from the geometry of an associated fault propagation detachment anticline because geological and geophysical data typically constrain the mesoscopic and macroscopic forms of folds more completely and more accurately than they constrain faults this technique offers a useful way to rapidly construct balanced structural cross sections in detached fold thrust systems

use of nanosims in the search for early life on earth ambient inclusion trails in a c 3400 ma sandstone ambient inclusion trails ait are enigmatic microtubular structures created by the migration of mineral crystals through a lithified substrate the decomposition of organic material has been suggested as the driving force for the crystal migration but has yet to be rigorously tested ait may hold potential as a biosignature for investigating early life on earth if the associated organic material can be shown to be biological this paper attempts to test the formation mechanism and biogenicity of ait from the c 3400 ma strelley pool sandstone of western australia using nanosims technology in doing so we demonstrate the unique ability of the nanosims to combine sub micron scale imaging with in situ chemical and isotopic data thereby enhancing our ability to evaluate the biogenicity criteria for archaean microstructures enrichments of a suite of major elements c n p s and trace elements co fe ni zn often associated with biological processes are found within several ait in this sandstone c and n enrichments are most common along ait margins and correlate with depletions of si o ca and mg indicating that this material is indeed organic in nature 13 c values of this carbonaceous material average 26 petrographic observations show that some of the ait occur in the centre of detrital sandstone grains where they were sealed from later fluid flow and therefore preserve primary archaean bio geochemistry in contrast ait found around the outer edges of sandstone grains may contain more recent organic material introduced by later fluid migration and are an unreliable biosignature using the petrographic and geochemical data a multi stage model for ait formation and subsequent diagenetic modification is proposed the possible sources of the primary organic material are discussed and we conclude that the data are consistent with a biological origin for these ait an abiogenic origin is more difficult to sustain but cannot yet be completely excluded for ait in general

multiple geometries and modes of fault propagation folding in the canadian thrust belt abstract a multitude of fold models have been proposed to explain the variety of fold geometries which develop in front of thrust faults detailed field fabric and photogrammetric studies of 4 fault cored asymmetrical folds in the thin skinned canadian thrust belt were used to test models of fault propagation folding fold geometries include combinations of angular and rounded fold surfaces highly contorted anticlinal hinge areas and minimal penetrative deformation or changes in bedding thickness interlimb angles generally decrease with increasing shortening indicating progressive fold tightening about fixed anticlinal hinges extensive flexural slip thrusting toward the anticlinal axes of angular folds suggests that kink folding in thin skinned thrust belts is aided by material transfer from both fold limbs into hinge areas fold geometries change dramatically along the strike of individual structures demonstrating the non uniqueness of fault propagation fold geometries no single mode of fault propagation folding can explain the diverse fold geometries seen in the canadian thrust belt this geometric variability can be ascribed to the complex interplay of multiple modes of folding in strata near the causal thrusts oblique shear and flexural slip in triangular shear zones distribute thrust displacements into both rounded and angular folds simultaneous angular folding of overlying strata commonly occurs by progressive kink folding where folds tighten by flexural slip on all fold limbs until the thrust breaks through the fold regional and local differences in the amount of pervasive top to the craton shear needed for progressive kink folding may be partially responsible for the variability of fault propagation fold geometries in thin and thick skinned orogens world wide

gravity anomaly map of north america the gravity anomaly map of north america is the product of a 12 year international effort to compile critically edit and merge gravity anomaly data on a continental and global scale this color pixel map printed on four quadrant sheets at a scale of 1 5 000 000 and including a fifth sheet showing a color index map with data references is the first such map at this large scale to include several hundreds of thousands of precise surface data of the united states canada mexico and central america as well as other high quality surface data from neighboring continental and oceanic areas the map which shows bouguer gravity anomalies on land and free air gravity anomalies over oceans is remarkable for its detail sixty six colors or shadings have been used in a carefully conceived nonlinear scheme to show anomalies at a 5 or 10 mgal interval over a dynamic range from about 300 mgal to 130 mgal

nanoparticle factories biofilms hold the key to gold dispersion and nugget formation biofilms living on gold au grains play a key role in the biogeochemical cycle of au by promoting the dispersion of au via the formation of au nanoparticles as well as the formation of secondary biomorphic au gold grains from queensland australia are covered by a polymorphic organic inorganic layer that is up to 40 m thick it consists of a bacterial biofilm containing au nanoparticles associated with extracellular polymeric substances as well as bacterioform au focused ion beam fib sectioning through the biofilm revealed that aggregates of nanoparticulate au line open spaces beneath the active biofilm layer these aggregates bacterioform au type 1 resulted from the reprecipitation of dissolved au and their internal growth structures provide direct evidence for coarsening of the au grains at the contact between the polymorphic layer and the primary au bacterioform au type 2 is present it consists of solid rounded forms into which crystal boundaries of underlying primary au extend and is the result of dealloying and ag dissolution from the primary au this study demonstrates that 1 microbially driven dissolution precipitation and aggregation lead to the formation of bacterioform au and contribute to the growth of au grains under supergene conditions and 2 the microbially driven mobilization of coarse au into nanoparticles plays a key role in mediating the mobility of au in surface environments because the release of nanoparticulate au upon biofilm disintegration greatly enhances environmental mobility compared to au complexes only

biological role in the transformation of platinum group mineral grains platinum group elements are strategically important metals finding new deposits is becoming increasingly difficult owing to our limited understanding of the processes that affect their mobility in surface environments microorganisms have been shown to promote the mobility of metals around ore deposits here we show that microorganisms influence the mobility of platinum group elements in mineral grains collected from brazil australia and colombia scanning electron microscopy showed biofilms covering the platinum group mineral grains the biofilms contained abundant platinum group element nanoparticles and microcrystalline aggregates and were dominated by proteobacteria many of which were closely related to known metal resistant species some platinum group mineral grains contained carbon nitrogen sulfur selenium and iodine suggesting the grains may be biogenic in origin molecular analyses show that brazilian platinum palladium grains hosted specific bacterial communities which were different in composition from communities associated with gold grains or communities in surrounding soils and sediments nano phase metallic platinum accumulated when a metallophillic bacterium was incubated with a percolating platinum containing medium suggesting that biofilms can cause the precipitation of mobile platinum complexes we conclude that biofilms are capable of forming or transforming platinum group mineral grains and may play an important role for platinum group element dispersion and re concentration in surface environments

detection of underground cavities by combining gravity magnetic and ground penetrating radar surveys a case study from the zaragoza area ne spain a geophysical survey routine is proposed to detect underground cavities and dolines it is based on the sequential application of magnetic low frequency ground penetrating radar gpr and microgravity techniques a case study near zaragoza ebro valley spain demonstrates the applicability of these methods the strong contrast of magnetic and electromagnetic properties and to a lesser scale of density between the doline filling and the surrounding stratified tertiary and quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods