tectonic classification of cenozoic iberian foreland basins abstract the iberian microcontinent stands out because of its intense alpine intraplate deformation this is reflected in a large number of cenozoic basins of very different sizes most of the contacts between topographic highs and basins are thrust or strike slip faults all these basins seem to have undergone a common sedimentary evolution comprising four stages initiation of sedimentation intense syn tectonic infilling change from endorheic to exorheic drainage and accelerated erosion related to fluvial incision this simple evolutionary model shows a migration from east to west in which basins are still tectonically active at the atlantic margin of iberia this common evolution is also found in a series of geometrical characteristics such as the ratio r of length of strike slip fault and length of thrust fault that are very similar in both types of basin border settings thrust related basins are mainly associated with segmented pop downs whereas the main basins have the characteristics of open ramp basins strike slip related basins are mostly transpressive structures although small pull apart basins are usual along the vilarica and messejana faults for basin areas larger than 100 1000 km 2 a constant r value of 0 6 is found including the ebro duero madrid lower tagus and badajoz basins within the iberian microcontinent the total amount of cenozoic contractional deformation was distributed between strike slip and thrust faults with an r ratio close to 0 6 however for small basins this parameter seems to depend on the type of fault range or deformation belt pure strike slip transtension transpression and pop up independently of its local tectonic development

studies of colloids and suspended particles cigar lake uranium deposit saskatchewan canada abstract the cigar lake u deposit is located in northern saskatchewan in the eastern part of the athabasca sandstone basin and consists of a high grade ore body up to 55 u located at a depth of 430 m as part of a study to evaluate the analog features of this deposit with respect to a disposal vault for waste nuclear fuel colloids 1 450 nm and suspended particles 450nm in groundwater have been investigated to evaluate their effect on element transport through the u deposit tangential flow ultrafiltration was used to concentrate particles from 501 groundwater samples in order to characterize the size distribution concentration composition and natural radionuclide content of particles in representative parts of the u deposit although cigar lake groundwaters contain particles in all sizes ranging from 10 nm to slightly larger than 20 m most samples contained a relatively high concentration of colloids in the 100 400 nm size range particle compositions are similar to the composition of minerals in the sandstones and ore body suggesting that particles in groundwater are generated by the erosion of fracture lining minerals as a result particle concentrations in groundwater are affected by the integrity of the host rock in some piezometers the high initial concentrations of suspended particles which may have been drilling artifacts decreased during the collection of the first 350 1 although colloid concentrations fluctuated during sampling there are no indications that these concentrations will be permanently reduced by continued groundwater pumping the observed colloid and suspended particle concentrations in the deep groundwaters are too low to have a significant impact on radionuclide migration provided that radionuclide sorption is reversible if radionuclides are irreversibly sorbed to particles they cannot sorb to the host rock and their migration can only be evaluated with an understanding of particle mobility the data for dissolved and particulate u th and ra were used to calculate field derived distribution ratios rd between particles and groundwater the wide range of observed rd values indicates that these radionuclides in particulate form are not in equilibrium with groundwater u series isotope data indicated that most of the u and ra on particles was derived from groundwater some particles could have retained their u for as long as 8000 a the u and ra contents of particles in the ore and surrounding clay zones are significantly higher than in particles from sandstone suggesting that the clay has been an effective barrier to particle migration

evidence for pleistocene wet aeolian dune and interdune accumulation s pedro da maceda north west portugal outcrops and cored counter flushed boreholes in the coastal area between espinho and aveiro north west portugal were investigated to reconstruct the changing patterns of sedimentation during the late pleistocene holocene to obtain a common comparison basis the grain size data from outcrop and borehole samples were analysed the outcrops and the cored parts of the boreholes were dated by radiocarbon and optically stimulated luminescence the results show that on top of pebble rich beds of fluvial origin a wet aeolian dune and interdune environment was active during the later part of the pleistocene turning to dry aeolian at the transition to the holocene the data indicate also that aeolian accumulation was controlled by vegetation changes climate and groundwater table fluctuations during the holocene a podzol formed on the pleistocene dunes and extensive vegetation precluded major aeolian accumulations remobilization of sand started again because of human deforestation and last but not least the little ice age

size and composition of inorganic colloids in a peri alpine glacial flour rich lake from june 2004 to october 2005 particle size distributions psd and the mineralogy of inorganic colloids in lake brienz a glacial flour rich swiss lake and in its tributaries the aare and lutschine rivers were quantified by single particle counting based on light scattering 0 1 2 m combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction the two lake tributaries differ in terms of the geology of their catchment area and in their hydrology the river lutschine s glacial regime is unperturbed while the river aare has been significantly modified by hydroelectric installations the dependence of the colloid concentration numbers on colloid diameters can be described by a power law distribution in all cases the power law slopes in the river aare were consistently smaller and the total colloid number concentrations consistently higher mean values 3 89 and 6 2 108 ml 1 respectively than in the river lutschine 3 61 and 1 7 108 ml 1 the measured psd in the lake were dependent on season and depth homogenous in the whole epilimnion in winter and modified by river intrusions in summer in this season the presence of a river turbid plume above the thermocline is a significant source of colloids in the epilimnion where their concentration was high mean value 5 1 107 ml 1 the same main mineral types were found in the different systems 2 1 minerals feldspars chlorite and quartz with a few particles of oxides differences in their relative concentrations in the rivers essentially reflecting the geological differences of the respective catchment areas made it possible to trace the origin of the mineral colloids present in lake surface waters throughout the year the relationship between colloid size and mineralogy was assessed showing that different minerals have distinct size distributions in the rivers where almost no aggregates were observed psd would essentially be the result of the nature particle formation and mineralogy of the colloids whereas in the lake aggregation and sedimentation processes would also play a role particularly in summer

characterization of natural colloids from a river and spring in a karstic basin colloids are known to transport contaminants over long distances in natural media despite this potentially harmful effect very few studies have been undertaken in subsurface aquifers this paper presents the first results of a study of natural colloids and particles in a karstic aquifer the site was chosen for its coverage by clay layers and peat which deliver various and numerous particle types in water the methodological part describes three methods used for size determination and sample fractionation of surface water and spring water these methods have been adapted for the treatment of multiple samples due to the rapid discharge variation typical of karstic aquifers the analysis of many particle size distributions psd shows that they can be described by a pareto law the variation of the slope of the psd at the spring is mainly dependent on discharge this behavior is interpreted as a washing of the karstic drains during the first phase of high flow events fractionation of the samples allowed application of various characterization techniques to particle size classes x ray diffraction xrd patterns showed that most of the mineral particles originated from quaternary deposits and limestones however the use of scanning electron micrsocopy with energy dispersive spectrometer sem eds detailed the composition of individual particles and revealed particles not found by xrd these techniques also showed the high complexity of the natural particles and the important place of coprecipitation in their formation consequences on the fluxes of particulate matter and its potential role as a carrier of contaminants are discussed

the chemical and mineralogical variations in the nickel mineralization associated with the kambalda dome western australia the volcanic peridotite associated nickel deposits at kambalda western australia consist of a number of orebodies or shoots located on the flanks of a broad domal structure within an archean greenstone belt in the yilgarn block chemical and mineralogical analyses of carted ore samples demonstrate that there is a systematic variation in sulfide bulk composition and mineralogy between shoots this is shown by positive correlations between the ni tenor of the shoots and their co cu pyrite and spinel contents these variations permit division of the shoots into three broad groups occupying distinct geographic positions in relation to the kambalda dome the variation in ni tenor between shoots is suggested to be caused by oxidation occurring prior to or during extrusion resulting in disequilibrium in f sub o 2 between the sulfide and silicate melts as equilibrium is reapproached oxidation of the sulfide proceeds resulting in a change in the partitioning behavior of fe and consequently the ni content of the sulfide melt increases tapping of the silicate sulfide melts at different degrees of departure from equilibrium could account for the observed compositional variation between the shoots emplacement of the sulfides is interpreted to have taken place as a single eruptive event the coincidence of spinel rich zones with high pyrite and cr contents at most major sulfide rich sulfide poor interfaces e g between massive and disseminated sulfides within the ore zone suggests that post extrusive but premetamorphic oxidation of the sulfides occurred at these positions this oxidation is due to disequilibrium in f sub o 2 between the silicate and sulfide during cooling and crystallization of the magma

translating the mineral systems approach into an effective exploration targeting system abstract holistic mineral systems approaches are being increasingly adopted in the study of ore deposits but application in industry has been suboptimal because of the lack of a conceptual framework to help translate the mineral system understanding to practical application a four step process is proposed for linking the conceptual mineral system with data available to support exploration targeting these steps include translation from 1 critical processes of the mineral system to 2 constituent processes of the mineral system to 3 targeting elements reflected in geology and 4 targeting criteria used to detect the targeting elements directly or by proxy this translation process is illustrated using examples from komatiite hosted ni cu pge and orogenic au mineral systems ranking of targets must be at the critical process level rather than the current practice of mixing processes elements and proxies the significance of targeting elements and their mappable criteria changes as a function of the scale at which the critical processes operate and the availability of relevant geoscience datasets this scale dependence is rarely recognised in current practice sources of uncertainty when translating the mineral system understanding into an effective exploration targeting system include 1 resolution of a mappable criterion in a dataset 2 how well the targeting criterion reflects the targeting element 3 how well the targeting element reflects the critical process and 4 whether the process being mapped is critical for the genesis of a mineral deposit the first three sources of uncertainty collectively are termed the representativeness of the targeting criteria i e how representative is a mappable criterion of the constituent process for which it is a proxy the last source of uncertainty reflects our lack of understanding of the processes that control mineralisation and highlights areas for further research

ore controls in the charters towers goldfield ne australia constraints from geological geophysical and numerical analyses the approach taken in this paper namely synthesising a wealth of previous information with new data and a genetic model in combination with integrated numerical analyses led to new insights into the geological controls on the localisation of auriferous veins and residual prospectivity of the charters towers goldfield ne australia the method also has implications for the assessment of other mature goldfields worldwide despite a number of different ore controls having operated within the charters towers goldfield the controlling factors can be linked to a single genetic model for orogenic granitoid hosted lode gold mineralisation in a brittle deformation regime d4 of ne sw to nne ssw shortening under conditions of supralithostatic fluid pressure and low stress difference spatial autocorrelation results suggest district scale alignment of the auriferous veins parallel to and overlapping with the ese wnw to e w striking charters towers ravenswood lineament a major crustal boundary in the basement to the ravenswood batholith at the camp scale auriferous veins have abundance and proximity relationships with nw se nnw sse ne sw and ene wsw oriented lineaments suggesting that structures that controlled gold deposition in one camp did not necessarily control mineralisation in other camps fractal dimensions obtained with the box counting method range from 1 02 to 1 10 whereas veins in the charters towers city camp are characterised by a significantly higher fractal dimension of 1 28 this discrepancy may be taken to imply that most or all outcropping and near surface deposits within the charters towers city camp have been found and that new discoveries are more likely to occur at greater levels of depth or outside the boundaries of this camp the new understanding has implications for the assessment of the residual prospectivity of the charters towers goldfield where large areas of prospective rock types and structures e g approximately 40 of the charters towers ravenswood lineament are hidden under cover this parameter space was inaccessible to the historic prospectors and has received relatively little attention from recent explorers the following steps are suggested for the development of a targeting strategy for lode gold exploration in areas of the goldfield under cover 1 identify from geological and geophysical data the ene wsw 15 and nnw sse 15 striking structures and geological boundaries within a 20 km wide corridor parallel to and centred upon the charters towers ravenswood lineament the potential control on gold deposit distribution at the regional to district scale 2 interpret from geological and geophysical data the distribution of pre middle devonian granitoids within these areas that are the preferred host rocks of the payable gold deposits 3 deduce from geophysical data the ene wsw 15 and nnw sse 15 striking structures that cut or bound the intrusions identified in step 2 4 locate segments along the structures identified in step 3 that deviate most from the geometry of a straight line e g potential bends or splays and or intersect other structures or geological contacts or both and 5 define and rank potential targets within the prospective areas identified in step 4 and systematically test the best ones

facies architecture of an archean komatiite hosted ni sulphide ore deposit victor kambalda western australia implications for komatiite lava emplacement nickel sulphide mineralisation is located in structural embayments or troughs at the base of thick basal komatiite lava flows at the victor ore body kambalda western australia primary contact relations and textural and vesicle distribution of the host komatiite lavas particularly the development of coherent or quench fragmented margins is consistent with emplacement of komatiites under laminar flow conditions however the absence of sedimentary units beneath komatiites with coherent flow tops in the ore environment seems contradictory and suggests both turbulent and passive laminar emplacement respectively the presence of erosive basal contacts in the ore environment suggests the komatiite lava was initially turbulent and probably open channel fed it is during this initial stage that both erosion and deposition of the nis deposits occurred as the flow evolved widened and thickened laminar flow conditions prevailed the komatiites are inferred to have flowed in a laminar state through the development of interior magma tubes beneath surface crusts and to have grown endogenously

the late quaternary coastal forests of western iberia a study of their macroremains plant remains collected from the portuguese coast some of them in situ were examined to provide local information on the vegetation of the iberian atlantic area over the last 35 000 years pinus gr sylvestris nigra from the wurm period was identified in sandy soils along with quercus gr robur petraea and fraxinus sp the presence of in situ remains of this pinus group on the northern portuguese coast indicates the local temperature and precipitation conditions that must have reigned at this time thirty two in situ pinus pinaster remains close to the mouth of the river tagus show the importance of this taxon in this area during the first half of the holocene other holocene macroremains indicate the presence of non riparian taxa quercus gr robur petraea and castanea sp hygrophilous plants fraxinus sp populus sp alnus sp and sambucus sp and shade intolerant taxa erica cinerea vagans

a new method for spatial centrographic analysis of mineral deposit clusters abstract a centrographic method for analysing mineral deposit clusters is illustrated using the komatiite hosted kambalda nickel sulphide deposit cluster yilgarn craton western australia in this method the standard distance circle divides the cluster into a more endowed inner part and a less endowed peripheral part the standard deviational ellipse another centrographic object depicts the preferred northwest southeast trend of nickel orebodies at kambalda weighted centrography shows that nickel endowment is greater in the eastern than western part of the cluster the spatio geometric interaction of the circle and ellipse splits the cluster into several partitions the relative concentration of nickel orebodies or endowment within a partition in relation to their concentration within the entire cluster is termed capture efficiency komatiite areal trace exhibits higher nickel orebody capture efficiency than spatio geometric partitions however some spatio geometric partitions exhibit nickel endowment capture efficiencies comparable to that of komatiite furthermore nickel orebody and endowment capture efficiencies of komatiite are elevated only within the standard distance circle these results suggest that at kambalda i the standard distance circle is a prime window for understanding the komatiite hosted nickel system and ii spatio geometric partitions are plausible locales for spatial analysis of nickel orebodies and endowment the proposed centrographic method is potentially useful in mineral resource estimations and mineral exploration targeting

the significance of linear trends and clusters of fault related mesothermal lode gold mineralization gold deposits from the laverton region western australia form both linear trends and cluster like distributions in map view associated with regional scale shear zone systems clusters of deposits are common and they form 5 5 km domains spaced every 15 to 20 km in contrast there is also a linear trend of mineralization that can be traced continuously for 20 km along a shear zone in detail mineralization is found in a range of different rock types and is hosted in fault shear zone networks that are smaller than the adjacent regionalscale shear zones by several orders of magnitude a mixture of different fault types comprise these mineralized fault shear networks often within the same gold field although thrust and reverse faults are a common component of the richer deposits e g sunrise dam wallaby granny smith the seismogenic behavior of fault systems during mineralization can explain these observations illustrated by simple stress transfer models that show the location of aftershock distributions around different fault types strike slip ruptures on regional scale structures can repeatedly trigger restricted clusters of aftershocks these aftershock clusters describe vertical pipe like domains in three dimensions in contrast regional scale thrust or reverse ruptures trigger continuous more diffuse domains of aftershocks along the full strike of the rupture thus ruptures along regional strike slip structures are able to trigger ruptures on preexisting thrust faultsshears at the deposit scale when they do so the thrust aftershocks generate a vertical domain of elevated permeability over the depth of the crust where the individual flow paths are likely to be highly tortuous increasing the potential for fluid rock interaction or fluid mixing the existence of linear trends and cluster like distributions of deposits at laverton may be consistent with two different ages of mineralization in this gold camp the results also show that distributions of deposits provide an indication of the kinematics of the regional fault systems that they relate to and that stress transfer modeling is a simple non computationally demanding technique that is easily adapted to exploration for fault related mineral deposits

lagoa da apulia a residual lagoon from the late holocene nw coastal zone of portugal the lagoa da apulia is a unique feature in the nw coastal zone of portugal a remaining form from a lagoon complex system that during the late holocene was dominant in the region this system was mainly neotectonically controlled occupying a depressed area bounded by faults on a palaeozoic rocky lower platform today observable on beaches at low tide with the intention of knowing the main architecture of the palaeo lagoon geophysical prospecting with gpr and resistivity was carried out accordingly six cores were taken and the sedimentary and mineralogical facies and diatom and foraminifer contents were analysed and five rich organic layers were dated by radiocarbon analysis with the data an evolutionary environment reconstruction model was created for this palaeo lagoon and the main structural features of the neighbouring area

natural colloids and suspended particles in the whiteshell research area manitoba canada and their potential effect on radiocolloid formation abstract natural colloids 1 450 nm and suspended particles 450 nm were characterized in groundwaters of the whiteshell research area of southern manitoba to evaluate their potential role in radionuclide transport through fractured granite data on particle concentrations size distributions compositions and natural radionuclide content were collected to predict radionuclide formation and to provide a database for future colloid migration studies the concentrations of colloids between 10 and 450 nm ranged between 0 04 and 1 mg l the concentrations of suspended particles which require higher groundwater velocities for transport varied from 0 04 to 14 mg l colloid 10 450 nm concentrations as low as these observed in whiteshell research area groundwater would have a minimal effect on radionuclide transport assuming that radionuclide sorption on colloids is reversible if radiocolloid formation is not reversible and radionuclide containing colloids cannot sorb onto fracture walls the importance of natural colloids in radionuclide transport will depend upon particle migration properties

stress pattern in portugal mainland and the adjacent atlantic region west iberia the portuguese mainland territory is located close to the azores gibraltar plate boundary in a tectonic setting responsible for significant neotectonic and seismic activities however few data concerning the present regional lithospheric stress field were available as testified by recently published maps of stress indicators for the europe and mediterranean regions one of the authors already presented a synthesis on this subject cabral 1993 where geological and geophysical stress indicators were considered in this paper we introduce new information mainly a considerable amount of borehole breakout data the updated data set comprises 32 reliable stress indicators showing a mean azimuth of 145 standard deviation 21 for the maximum horizontal stress direction shmax on the average the geological data are rotated clockwise and the focal mechanism data deviated anticlockwise to that azimuth while the borehole elongation results are consistent with the mean shmax trend these differences in stress trend suggest a regional progressive rotation of the shmax direction from nnw sse to wnw ese since the upper pliocene to estimate stress trajectories new and published stress indicators in the adjacent atlantic area and northern africa were also investigated showing a very uniform nw se shmax trend in west iberia a high level of horizontal compressive stress acting oblique to the western portuguese continental margin is inferred and interpreted in view of a proposed regional geodynamical model of activation of this passive margin with the nucleation of a subduction zone in the atlantic sw of iberia at the gorringe submarine bank which is propagating northward along the base of the continental slope at the transition between thinned and normal continental crust

combining fractal analysis of mineral deposit clustering with weights of evidence to evaluate patterns of mineralization application to copper deposits of the mount isa inlier nw queensland australia the clustering of mineral occurrences and their spatial associations with particular geological features are critical aspects of mineral distributions for exploration and understanding ore genesis variations in the degree of clustering of mineral occurrences or geological features can be measured by fractal dimensions obtained from a shifting box counting method spatial associations between mineral occurrences and geological features can be quantified by the weights of evidence wofe method using the contrast value which increases with the strength of the spatial relationship a new method is proposed to evaluate mineral occurrence distributions by combining the power of fractal analysis of clustering with the wofe approach the method compares the correlation between the variation in degree of clustering of mineral occurrences and a geological feature in a study area with the contrast value of the same feature the possible outcomes can be simplified into four scenarios depending on whether the correlation in variation of clustering and the contrast are high or low respectively each outcome has specific exploration implications if either a high correlation in variation of clustering or a high contrast value is obtained the geological feature can be used for exploration targeting the integrated fractal and wofe approach is applied to copper occurrences in the proterozoic mount isa inlier nw queensland australia which hosts large numbers of copper deposits 1 869 occurrences including the world class mount isa copper deposit variation in clustering of copper occurrences has a positive correlation with variation in clustering of fault bends r 0 823 fault intersections r 0 862 and mafic rocks r 0 885 wofe results indicate that the copper occurrences are spatially associated with fault intersections and bends and with mafic rocks analyses were carried out separately for the two major lithostratigraphic sequences in the inlier the eastern and western successions the western succession copper occurrences are apparently more clustered than those of the eastern succession which may reflect a lower degree of exploration and or geological factors the association of copper occurrences with mafic rocks compared with fault bends and intersections is greater in the eastern succession which may reflect genetic factors correlations in the variation of clustering of mineral occurrences and geological features have a linear relationship with the contrast values and the spatial association between all geological features and copper occurrences constitute high correlation high contrast cases the linear relationship suggests that the geological features that control the clustering of the copper occurrences could be the same features that control their localization

particle size and mineralogical composition of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg particle size distributions and the mineralogy of inorganic colloids in waters draining the adit of an abandoned mine goesdorf luxembourg were quantified by single particle counting based on light scattering 100 nm 2 m combined with transmission electronic microscopy coupled with energy dispersive spectroscopy and selected area electron diffraction this water system was chosen as a surrogate for groundwaters the dependence of the colloid number concentration on colloid diameters can be described by a power law distribution in all cases power law slopes ranged from 3 30 to 4 44 depending on water ionic strength and flow conditions the same main mineral types were found in the different samples 2 1 phyllosilicates illite and mica chlorite feldspars albite and orthoclase calcite and quartz with a variable number of fe oxide particles the colloid mineralogical composition closely resembles the composition of the parent rock spatial variations in the structure and composition of the rock in contact with the waters i e fissured rock versus shear joints are reflected in the colloid composition the properties of the study colloids as well as the processes influencing them can be considered as representative of the colloids present in groundwaters

holocene evolution on galician coast nw spain an example of paraglacial dynamics abstract the recent evolution and the present coastal dynamic in middle atlantic latitudes as the coast of galicia can be considered in a paraglacial context the fossilization of eemian coastal landforms by deposits developed under cold conditions followed by a paraglacial environment during the holocene transgression the characteristics of the different types of deposits and the rising sea level curve controlled the evolution of the coastline showing the co existence of bluff retreat and continental sedimentation

shore platform abrasion in a para periglacial environment galicia northwestern spain abstract the schmidt rock test hammer was used to study the effect of abrasion on shore platforms in galicia northwestern spain on platforms where tidally induced weathering salt wetting and drying etc is dominant rock strength is significantly lower than in areas where abrasion is or has been active in the recent past this suggests that abrasion removes weathered surface material exposing the stronger less weathered rock below abrasion downwearing measured with a transverse micro erosion meter ranged between 0 13 and 1 8 mm yr 1 over the last year most active abrasion occurs in the upper part of the intertidal zone but weathering is slowly destroying formerly abraded surfaces at lower elevations these abandoned surfaces were abraded by materials supplied by erosion of fluvio nival and periglacial slope deposits that covered or partially covered parts of the galician coast during the middle and late weichselian during the holocene rising sea level and erosion of the slope deposits caused the abrasion zone to gradually migrate up to its present position near the high tidal level the spatial and temporal role of abrasion on this coast is therefore closely associated with the exhumation and inheritance of ancient platform surfaces from beneath weichselian deposits

spatial statistical analysis of the distribution of komatiite hosted nickel sulfide deposits in the kalgoorlie terrane western australia clustered or not the spatial distribution of mineral deposits is a critical component of predictive estimation of undiscovered mineral resources nickel sulfide deposits in the kalgoorlie terrane of western australia the world s premier province for komatiite hosted nickel sulfide deposits are generally perceived to be clustered we apply distance based spatial analysis methods nearest neighbor and k function to determine the spatial distribution pattern of nickel sulfide deposits in the kalgoorlie terrane results of these spatial analyses indicate the komatiite bodies that contain the nickel sulfide deposits in the terrane are clustered in contrast nickel sulfide deposits within komatiite bodies are either randomly distributed or dispersed and not clustered therefore the apparent clustering of nickel sulfide deposits within the kalgoorlie terrane may be a mere expression of the underlying clustering of the host komatiite bodies these findings have two main implications 1 nickel exploration models implemented through area selection based on localization controls of favorable komatiite bodies followed by direct detection of deposits within komatiite bodies have spatio statistical validity and 2 a poisson distribution could be a plausible initial model for predicting the number of nickel sulfide deposits within a komatiite body

evaluation of the uncertainty in estimation of metal resources of skarn tin in southern china abstract this study is concerned with the problem of how many undiscovered mineral deposits can be expected to occur in the vicinity of any known deposit especially if the deposit is nearly mined out skarn tin deposits in southern china were chosen to demonstrate that fractal modeling can be a useful tool to characterize the spatial temporal distribution of mineral deposits and to quantify their grades and tonnages the results show that the spatial temporal distribution of skarn tin deposits as well as their grades and tonnages satisfy fractal statistic and suggest that 14 skarn tin deposits could be found around a known skarn tin deposit within a radius of 80 km monte carlo simulation was used to combine the number of deposits and the frequency distributions of grade and tonnage and to capture the uncertainty in estimation of metal resources at the 90 50 and 10 confidence levels tin metal resources amount to 6 ton 200 ton and 1 0 10 4 ton around a known tin deposit within a radius of 80 respectively

nickel sulfide deposits in australia characteristics resources and potential abstract australia s nickel sulfide industry has had a fluctuating history since the discovery in 1966 of massive sulfides at kambalda in the eastern goldfields of western australia periods of buoyant nickel prices and high demand speculative exploration and frenetic investment the nickel boom years have been interspersed by protracted periods of relatively depressed metal prices exploration inactivity and low discovery rates despite this unpredictable evolution the industry has had a significant impact on the world nickel scene with australia having a global resource of nickel metal from sulfide ores of 12 9 mt five world class deposits 1 mt contained ni and a production status of number three after russia and canada more than 90 of the nation s known global resources of nickel metal from sulfide sources were discovered during the relative short period of 1966 to 1973 australia s nickel sulfide deposits are associated with ultramafic and or mafic igneous rocks in three major geotectonic settings 1 archean komatiites emplaced in rift zones of granite greenstone belts 2 precambrian tholeiitic mafic ultramafic intrusions emplaced in rift zones of archean cratons and proterozoic orogens and 3 hydrothermal remobilized deposits of various ages and settings the komatiitic association is economically by far the most important accounting for more than 95 of the nation s identified nickel sulfide resources the ages of australian komatiitic and tholeiitic hosted deposits generally correlate with three major global scale nickel metallogenic events at 3000 ma 2700 ma and 1900 ma these events are interpreted to correspond to periods of juvenile crustal growth and the development of large volumes of primitive komatiitic and tholeiitic magmas caused by large scale mantle overturn and mantle plume activities there is considerable potential for the further discovery of komatiite hosted deposits in archean granite greenstone terranes including both large and smaller high grade 5 to 9 ni deposits that may be enriched in pges 2 to 5 g t especially where the host ultramafic sequences are poorly exposed analysis of the major komatiite provinces of the world reveals that fertile komatiitic sequences are generally of late archean 2700 ma or paleoproterozoic 1900 ma age have dominantly al undepleted al 2 o 3 tio 2 15 to 25 chemical affinities and often occur with sulfur bearing country rocks in dynamic high magma flux environments such as compound sheet flows with internal pathways facies kambalda type or dunitic compound sheet flow facies mt keith type most precambrian provinces in australia particularly the proterozoic orogenic belts contain an abundance of sulfur saturated tholeiitic mafic ultramafic intrusions that have not been fully investigated for their potential to host basal ni cu sulfides voisey s bay type mineralization the major exploration challenges for finding these deposits are to determine the pre deformational geometries and younging directions of the intrusions and to locate structural depressions in the basal contacts and feeder conduits under cover stratabound pge ni cu cr deposits hosted by large archean proterozoic layered mafic ultramafic intrusions munni munni panton of tholeiitic affinity have comparable global nickel resources to many komatiite deposits but low grades

characterization and dating of coastal deposits of nw portugal minho neiva area a record of climate eustasy and crustal uplift during the quaternary abstract this study presents the characterization and numerical dating of quaternary coastal deposits of nw portugal located between the mouths of the minho and neiva rivers they record continental small alluvial fans and streams and transitional aeolian dunes interdune ponds estuary sandy and gravelly beaches paleoenvironments quartz and k feldspar optically stimulated luminescence osl dating is employed as well as ams 14 c dating a staircase of coastal terraces abrasion shore platforms was identified altimetry a s l and ascribed to the following probable marine isotope stages mis t1 20 18 m mis11 t2 ca 13 m mis9 t3 9 3 7 3 m mis7 t4 5 5 4 5 m mis5 t5 3 5 2 0 m mis5 the terraces have some preserved sedimentary facies that includes coeval beach sediments on the lowest four a late pleistocene to holocene sedimentary cover comprises four sub units a the lower sub unit corresponding to ferruginous stream deposits and aeolian dunes dated ca 67 61 ka mis4 probably related with sub humid to arid mid cold conditions b on the slopes the lower sub unit is overlapped by sandy silty colluvium and sandy alluvial deposits dated ca 56 28 ka mis3 and probably reflecting cold mid cold and wet dry climate conditions c this sub unit is topped by soliflucted lobes and sandy silty silty deposits recording cold and dry climate dated 20 13 ka mis2 and d a top sub unit dated to 16 18th century recording little ice age events consisting of fluvial sediments coeval with temperate climate evolving to aeolian dunes from the maunder minimum cold windy dry conditions

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

spatial data analysis of mineral deposit point patterns applications to exploration targeting abstract systematic spatial analysis of mineral deposit point patterns can reveal significant spatial properties of mineral systems with major implications for regional mineral prospectivity modelling for valid results a study area needs to be clearly defined taking into account permissiveness of the geological units for a particular mineral system and effects of cover standard statistical tests assuming an isometric contiguous study area with regionally homogeneous distribution of deposits are likely to produce invalid results analysis of regional uniformity of spatial deposit density is required for adequate design and interpretation of tests for clustering spatial distribution of orogenic gold deposits in the hodgkinson province in queensland and the western lachlan orogen in victoria australia indicates the presence of significant regional linear metallogenic zones probably controlled by deep crustal domain boundaries oblique and not related to any recognised major faults within the metallogenic zones in both regions individual gold occurrences are strongly clustered into ore fields but the distribution of ore fields is random

late pleistocene raised beaches of coastal estremadura central portugal abstract we present new stratigraphic sedimentological and chronological data for a suite of tectonically raised beaches dating to marine isotope stages 5 4 and 3 along the estremadura coast of west central portugal the beach deposits are found in association with ancient tidal channels and coastal dunes pollen bearing mud and peat and middle paleolithic archaeological sites that confirm occupation of the coastal zone by neanderthal populations the significance of these deposits is discussed in terms of the archaeological record the tectonic and geomorphic evolution of the coast and correlation with reconstructions of global climate and eustatic sea level change direct correlation between the estremadura beach sections is complicated by the tectonic complexity of the area and the age of the beach deposits which are near or beyond the limit of radiocarbon dating evidence from multiple sites dated by ams radiocarbon and optical luminescence methods suggests broad synchroneity in relative sea level changes along this coast during marine isotope stage 3 two beach complexes with luminescence and radiocarbon age control date to about 35 ka and 42 ka recording a rise in relative sea level around the time of heinrich event 4 at 39 ka depending on assumptions about eustatic sea level at the time they were deposited we estimate that these beaches have been uplifted at rates of 0 4 4 3 mm yr 1 by the combined effects of tectonic halokinetic and isostatic processes uplift rates of 1 2 mm yr 1 are likely if the beaches represent sea level stands at roughly 40 m below modern as suggested by recent eustatic sea level reconstructions evidence from coastal bluffs and the interior of the study area indicates extensive colluvial fluvial and aeolian sedimentation beginning around 31 ka and continuing into the holocene these geomorphic adjustments are related to concomitant changes in climate and sea level providing context that improves our understanding of late pleistocene landscape change and human occupation on the western iberian margin

optically stimulated luminescence dating of a danish eemian coastal marine deposit a test of accuracy abstract it is difficult to test convincingly luminescence dating techniques beyond the range of 14c and yet this is essential if claims that optically stimulated luminescence dating using quartz can reach back to beyond 105 years are to be given credence one possible approach is to use coastal marine sand identified as eemian by an examination of the palaeoecology the eemian period in northern europe is considered to last from 132 to 116 ka marine samples are likely to be linked most closely to at least part of this period and modern coastal sands are known to be well bleached thus from a luminescence dating perspective eemian marine sand can be considered to be of known age and it is very likely to be well bleached we have examined such a known age deposit on the east coast of jutland consisting of about 10 m of fine sand grading up from silty clays and clays in the lower part of the section this material is confidently expected to have been deposited during the very late saalian and early mid eemian 133 125 ka we report on the ages of 25 samples associated with this profile the observed overall precision is compared with the calculated precision on individual ages and the mean value of all the ages is compared with the expected mean of 130 ka

relation between colloid composition and the environment of their formation application to the el berrocal site spain abstract in the framework of nuclear waste topics the role of colloids is more and more emphasized in relation to the transport of radioelements in natural groundwaters we attempt here to check if the nature and physico chemical characteristics of the colloids from the granitic site of el berrocal are closely related to the bedrock composition the colloids are studied in three types of groundwaters sulfate and carbonate waters in different redox conditions as well as colloidal suspensions extracted from clayey materials present in the fractures the particle size distributions are performed by photon correlation spectroscopy their chemical composition is obtained by x ray microanalysis after transversal ultrafiltration the main results deal with the chemical composition of colloids they are mainly composed of silica aluminosilicate phases and fe ti al oxyhydroxides in the case of the carbonate and oxidized hydrofacies traces of mg cu zn ba s as well as carbonate phases zn ca occur in the particular case of the sulfate hydrofacies traces of s mg cu are identified finally in the less oxidized and carbonate groundwater a lot of phases consist of sulphur with cu zn fe as well as of carbonate with cu zn fe ca and mg for the clayey suspensions colloids are mainly composed of illite and silica in conclusion the contribution of the bedrock as well as the influence of the physico chemical conditions are discussed in order to decipher the role of neoformation and dispersion processes in the colloid formation

sea level changes during the pleistocene holocene in the nw coastal zone of portugal research was undertaken to establish the present coastal dynamics of the area south of espinho portugal with special emphasis on the migration inland of beaches and the retreat of cliffs during at least the last century besides the holocene units the silvalde paramos tijuca formation 2310 80 yr bp to 500 80 yr bp and the cortegaca beach formation 6850 60 yr bp to 950 80 yr bp a pleistocene unit the maceda beach formation 29 600 690 yr bp to 14300 160 yr bp with trunks of pinus sylvestris was recognized the cortegaca beach formation comprises a truncated podzol profile the al horizon dating from 3490 60 yr bp to 950 80 yr bp the study and the dating of the pleistocene and the holocene formations suggest a model of evolution related to sea level fluctuations and neotectonics during the interval between 29 000 690 yr bp and the post xvth century little ice age the final purpose of the research is to apply the results to the prediction of the coastal zone evolution and particularly to influence policy with respect to coastal zone management this policy must take into account the inland migration of the beaches and the cliff retreat as a consequence of the natural dynamics of the earth that cannot be arrested or controlled by man

spatial distribution of ore deposits conventional spatial distributions such as the negative binomial and neyman scott have been proposed as models for the clustered distribution of ore deposits b b mandelbrot has proposed that ore deposits are clustered at many different scales and that fractal distributions are appropriate the apparent fractal characteristics of geologic controls on the locations of hydrothermal deposits self similar systems of fractures circulation cells and magmatic intrusions support his proposal examination of the spatial distribution of 4775 hydrothermal precious metal deposits in the basin and range western united states reveals fractal distributions acting within two scale ranges together covering the entire range from 1 to 1000 km this result gives additional credibility to concepts of regional controls on mineralization such as metallogenic provinces and tectonostratigraphic terranes the distribution of these ore deposits about a known occurrence follows a regular radial density law within a range of radii r of 1 to 15 km the probability density function of these deposits is given by d 0 46 r 1 17 and within a range of radii of 15 to 1000 km by d 0 08 r 0 83 where d is deposits per square kilometre

evolution and inheritance of a rock coast western galicia northwestern spain there is increasing evidence that shore platforms and other elements of rock coasts may be inherited at least in part from interglacial stages when sea level was similar to today s most of this evidence which includes ancient beaches and datable terrestrial deposits has been obtained from areas of resistant slowly eroding rock where the platforms often appear to be much too wide to have developed since the sea reached its present level it is much more dif cult to demonstrate that inheritance has occurred in areas of weaker rock which generally lack any datable material the coast of western galicia in northwestern spain has shore platforms in igneous and metamorphic rocks that were deeply weathered during the tertiary these platforms are closely associated with ancient beaches from the last interglacial stage and associated periglacial and uvio nival deposits that covered and fossilized most of the eemian platforms and cliffs during the late middle and late weichselian glacial stage the sedimentary processes and the thickness and facies of the sediments were determined by the height aspect and gradient of the coastal mountains and their distance from the coast radiocarbon dating sedimentary analysis and platform morphology indicate that the shore platforms of galicia have been inherited from at least the last interglacial stage they were fossilized in places beneath thick weichselian deposits and then exhumed during the holocene transgression the abundant evidence for inheritance in galicia has important implications for other coasts in fairly weak rocks where such evidence is generally lacking copyright 2003 john wiley sons ltd

particle size and mineralogical composition of inorganic colloids in glacier melting water and overlying ice in an alpine glacier oberaargletscher switzerland

large scale distributed deformation controlled topography along the western africa eurasia limit tectonic constraints in the interior of the iberian peninsula the main geomorphic features mountain ranges and basins seems to be arranged in several directions whose origin can be related to the n s plate convergence which occurred along the cantabro pyrenean border during the eocene lower miocene time span the iberian variscan basement accommodated part of this plate convergence in three e w trending crustal folds as well as in the reactivation of two left lateral nne ssw strike slip belts the rest of the convergence was assumed through the inversion of the iberian mesozoic rift to form the iberian chain this inversion gave rise to a process of oblique crustal shortening involving the development of two right lateral nw se shear zones crustal folds strike slip corridors and one inverted rift compose a tectonic mechanism of pure shear in which the shortening is solved vertically by the development of mountain ranges and related sedimentary basins this model can be expanded to nw africa up to the atlasic system where n s plate convergence seems also to be accommodated in several basement uplifts anti atlas and meseta and through the inversion of two mesozoic rifts high and middle atlas in this tectonic situation the microcontinent iberia used to be firmly attached to africa during most part of the tertiary in such a way that n s compressive stresses could be transmitted from the collision of the pyrenean boundary this tectonic scenario implies that most part of the tertiary eurasia africa convergence was not accommodated along the iberia africa interface but in the pyrenean plateboundary a broad zone of distributed deformation resulted from the transmission of compressive stresses from the collision at the pyrenean border this distributed intraplate deformation can be easily related to the topographic pattern of the africa eurasia interface at the longitude of the iberian peninsula shortening in the rif betics external zones and their related topographic features must be conversely related to more local driven mechanisms the westward displacement of the exotic alboran domain other than n s convergence the remaining nnw sse to nw se latest miocene up to present convergence is also being accommodated in this zone straddling iberia and morocco at the same time as a new ill defined plate boundary that is being developed between europe and africa

structural controls on nickel sulphide ore shoots in archaean komatiite kambalda wa the volcanic trough controversy revisited abstract structural evaluation of the extensive exploration database for the kambalda tramways area archaean yilgarn craton western australia is addressing the long outstanding issue of whether the trough structure embayments that partly confine the nickel sulphide nis ore shoots are volcanic or tectonic in origin the trough structures are complex linear domains associated with talc carbonate alteration overprinting thickened komatiite overlying footwall basalt two end member trough structure types are recognised 1 re entrant trough structures and 2 open trough structures the re entrant trough structures are narrower at the top than at the base strongly asymmetric in cross section restricted in distribution to kambalda dome and transgress and truncate ore the open trough structures are wider at the top than at the base weakly asymmetric in cross section prevalent outside kambalda dome and are mineralised along their lateral margins in addition to trough associated ore other nis ore shoots overlie near planar komatiite basalt contacts and are overlain by serpentinite with relict igneous textures all these features indicate the possibility that the trough structures reflect structural folding thickening and alteration at rock contacts marking different competency during regional fold thrusting consequently nis exploration strategies should consider structural and metamorphic features as well as volcanologic and stratigraphic features recognition of folding and thrusting patterns related to major competency contrasts in favourable komatiite basalt stratigraphy near the crest of regional anticlines and domes would aid exploration success

is vegetation responsible for glacial inception during periods of muted insolation changes the marine isotope stage 11 interglacial centred at similar to 400 ka appears to be the best candidate for understanding climatic changes in the context of low insolation forcing such as that of our present interglacial direct correlation between terrestrial pollen and marine climatic indicators and ice volume proxy from deep sea core md01 2447 off northwestern iberia shows for the first time the phase relationship between southwestern european vegetation sea surface temperatures in the northeastern atlantic mid latitudes and ice volume during mis 11 a warmest 32 000 years long period and three following warm cold cycles occurred synchronously on land and ocean the end of the warmest period sees the glacial inception which coincides with the replacement of warm deciduous forest by conifer pine fir expansion in northwestern iberia and consequently with the southward migration of the tree line in high latitudes in response to declining summer insolation as weak insolation changes alone cannot account for ice growth the associated vegetation changes must now be considered as a potential major feedback mechanism for glaciation initiation during mis 11 c 2005 elsevier ltd all rights reserved

the geology of the kambalda nickel field western australia the kambalda nickel field contains the major concentration of volcanic peridotitc associated nickel ores in the archean of australia it occupies an area of 400 km 2 underlain by two sequences of ultramafic mafic and felsic volcanics and sedimentary rocks which can be broadly correlated with previously erected regional stratigraphic sections most ores occur in the lower kambalda sequence at the base of the kambalda ultramafic rocks the ultramafic rocks of the upper bluebush sequence contain only minor mineralization four phases of deformation occurred over an interval of more than 300 m y resulting in a dominant north northwest structural trend faulting was active during original volcanism and continued intermittently until after mafic felsic dike intrusion the ultramafic rocks have been serpentinized and all rocks have exerienced low strain upper greenschist to lower amphibolite facies metamorphism and variable carbonation and potash metasomatism the kambalda ultramafic rocks are of variable thickness and in places exceed 1 000 m the lower member of the ultramafic rocks occupying approximately one third of the sequence comprises thicker high magnesium flows i e generally 36 volatile free mgo commonly separated by sulfidic quartz albite sediments thinner lower magnesium flow units characterize much of the upper member the ores occur in 24 shoot complexes each containing multiple ore surfaces caused by structural dislocation of a few grouped ribbonlike original orebodies eighty percent is contact ore occurring at the base of the lowermost ultramafic flow and generally occupying elongate troughs in the footwall basalt ultramafic contact these troughs are thought to be original volcanic depressions which focused later deformation the remainder is hanging wall ore usually occurring directly above contact ore at the base of the second or third ultramafic flow hanging wall orebodies occasionally grade into stratigraphically equivalent interflow sediments the ores contain varying proportions of massive matrix and disseminated sulfides the hypogene mineral assemblage is pyrrhotite pentlandite pyrite chalcopyrite but millerite is locally significant the massive ores in particular are commonly severely deformed and some have been remobilized tens of meters from their original contact position metamorphism has caused recrystallization of the ores and some redistribution of elements there is commonly marked variation of mineralogy and s ni ratios between contact and overlying hanging wall ores and within and between original ore surfaces within shoots but the relative contributions of primary composition and metamorphism to this variation are uncertain in ore environments the footwall basalt ultramafic contact is more deformed than in non ore environments the basal ultramafic flows are thicker and richer in magnesium the trend toward lower magnesium flows upward through the ultramafic formation is less well developed and there is better textural development and compositional differentiation within flows non ore environments usually contain interflow sediments whereas there is generally a sediment free prism of ultramafic rocks above ore environments most ores are interpreted to have originated by either simultaneous or sequential extrusion of sulfide melts and ultramafic lavas rich in olivine phenocrysts along active linear fissures in a basaltic ocean floor volcanic exhalations probably contributed to minor ore in sulfidic sediments