part i a resource estimation based on mineral system modelling prospectivity approaches and analogical analysis a case study of the mvt pb zn deposits in huayuan district china abstract several techniques have been proposed to predict undiscovered mineral resources at the regional scale by integrating multiple spatial datasets and mineral deposit models using geographical information systems gis an unresolved issue however is that predictive proxies are two dimensional gis layers at a regional scale whereas mineralising processes occur in four dimensions i e space and time in the past 10 years mineral system modelling approaches have been proposed and developed for the critical doubt that are described in terms of two characteristics spatial scales and relevant geochemical processes this paper demonstrates the modelling and combination of multiple scales based on mineral system prospectivity analysis and then present a resource estimation method that involves the calculation of three variables in applying a gis based approach to a mineral system we compared the resource estimation in a trap on the district scale to the extrapolation of reserve estimations of representative deposits in the same mineral system the procedure used for the implementation of this method includes i the incorporation of a descriptive model based on the mineral deposit type ii the digitalization of the favourable characteristics of the type of investigated deposit iii the implementation of the mineral system theory approach to pinpoint the locations of potential structural or stratigraphic traps at the district scale using gis based two dimensional prospectivity mapping iv the calculation of similarities and ore bearing ratios v the restructuring of models of favourable features at multiple scales i e district and ore deposit scales and vi the assessment of undiscovered mineral resources in traps this method was used to estimate mvt type pb zn mineralisation in a promising potential region in northwestern hunan province china in addition this study is divided into two parts and this paper mainly describes the methodology

locating and quantifying geological uncertainty in three dimensional models analysis of the gippsland basin southeastern australia abstract geological three dimensional 3d models are constructed to reliably represent a given geological target the reliability of a model is heavily dependent on the input data and is sensitive to uncertainty this study examines the uncertainty introduced by geological orientation data by producing a suite of implicit 3d models generated from orientation measurements subjected to uncertainty simulations the resulting uncertainty associated with different regions of the geological model can be located quantified and visualised providing a useful method to assess model reliability the method is tested on a natural geological setting in the gippsland basin southeastern australia where modelled geological surfaces are assessed for uncertainty the concept of stratigraphic variability is introduced and analysis of the input data is performed using two uncertainty visualisation methods uncertainty visualisation through stratigraphic variability is designed to convey the complex concept of 3d model uncertainty to the geoscientist in an effective manner uncertainty analysis determined that additional seismic information provides an effective means of constraining modelled geology and reducing uncertainty in regions proximal to the seismic sections improvements to the reliability of high uncertainty regions achieved using information gathered from uncertainty visualisations are quantified in a comparative case study uncertainty in specific model locations is identified and attributed to possible disagreements between seismic and isopach data further improvements to and additional sources of data for the model are proposed based on this information finally a method of introducing stratigraphic variability values as geological constraints for geophysical inversion is presented

predictive mapping of prospectivity and quantitative estimation of undiscovered vms deposits in skellefte district sweden mapping of mineral prospectivity and assessment of undiscovered mineral deposits both aim to delineate prospective ground for mineral exploration but the latter is usually carried out exclusive of the former we propose that the spatial distribution of known mineral deposits of the type sought is the key to link mapping of mineral prospectivity and assessment of undiscovered deposits we demonstrate this proposition in regional scale mapping of prospectivity for volcanogenic massive sulphides vms deposits and estimation of undiscovered vms endowment in the skellefte district sweden the results of analyses of the spatial distribution of known vms deposits and their spatial associations with geological features are consistent with existing knowledge of geological controls on vms mineralization in the district and we used them to define spatial recognition criteria of regional scale vms prospectivity integration of layers of evidence representing spatial recognition criteria of vms prospectivity via application of data driven evidential belief functions results in a regional scale map of prospective areas occupying 15 of the district and having fitting and prediction rates of 100 we used the map of prospective areas and proxy measures for degrees of exploration based on the spatial distribution of known vms deposits in one level prediction of undiscovered mineral endowment we obtained estimates of 709 kt undiscovered cu endowment 3190 kt undiscovered zn endowment 95 mt undiscovered ore tonnage and 48 undiscovered vms deposits these estimates are slightly ca 5 on average lower than and thus corroborated by estimates obtained via radial density fractal analysis of the spatial distribution of known vms deposits therefore mineral prospectivity mapping can be a part of mineral resource assessment if the spatial distribution of discovered deposits of the type sought is considered in both predictive modeling processes

a balanced section across the pyrenean orogenic belt evolutionary models that have been proposed for the pyrenean orogenic belt involve gravitational gliding of major thrust sheets to both the north and south of an uplifted central axial zone it has been suggested by previous workers that uplift is a result of alpine compression or long lived strike slip movement on the north pyrenean fault we critically assess these models and propose a new model based on the generation of a thin skinned linked thrust system due to alpine collision of iberia and europe pyrenean alpine tectonics is dominated by southward thrusting on a major sole fault dipping north at approximately 6 within hercynian basement northerly directed thrusts of the north pyrenean zone and northern folded foreland are backthrusts from this sole fault a total orogenic shortening of 106 km in the central pyrenees was achieved between the palaeocene and oligocene at a time averaged rate of 0 62 cm yr 1 a thin skinned model requires that the north pyrenean fault is truncated by both northward and southward moving thrusts and occurs in the footwall of the sole fault some 60km north of its present surface trace

forced folding and basement detached normal faulting in the haltenbanken area offshore norway triassic evaporites affected the structural development of the haltenbanken area of offshore norway during the late jurassic and early cretaceous by mechanically isolating triassic and younger strata from older strata and basement many folds in the haltenbanken area are forced folds above basement involved normal faults forced folds formed at least in part because triassic evaporites behaved ductilely decoupling overlying strata from underlying faulted strata and basement seismic data show that these forced folds are asymmetric flexures that affect lower cretaceous jurassic and triassic strata strata beneath the traiassic evaporites are faulted some forced folds die out along strike into and are cut by basement involved normal faults folding predominated above salt swells where decoupling was enhanced whereas faulting occurred on the flanks of salt swells where salt thicknesses were reduced and decoupling was less effective many normal faults in the haltenbanken area are basement detached and flatten within the triassic evaporites seismic data show that rollover anticlines and antithetic normal faults affect lower cretaceous jurassic and triassic strata within the hanging walls of these basement detached normal faults strata beneath the evaporites are not affected by this deformation some basement detached normal faults may be secondary structures associated with forced folding others especially thosemore with large displacements may have formed in response to gravity sliding less

spatial variability of micropenetration resistance in snow layers on a small slope the mechanisms leading to dry snow slab release are influenced by the three dimensional variability of the snow cover we measured 113 profiles of penetration resistance with a snow micropenetrometer on an alpine snow slope seven distinct layers were visually identified in all snow micropenetrometer profiles the penetration resis tance of adjacent layers did not change abruptly but gradually across layer boundaries that were typically 2 mm thick in two layers penetration resistance varied around 200 over the grid possibly due to wind effects during or after layer deposition penetra tion resistance varied around 25 in five layers statistically significant slope scale linear trends were found for all layers the semivariogram was used to describe the spatial vari ation penetration resistance was autocorrelated but the scale of variation was layer spe cific a buried layer of surface hoar was the most critical weak layer it had little spatial variation the layers in the slab above had higher spatial variation the penetration resist ance of each snow layer had distinct geostatistical properties caused by the depositional processes

star an efficient snow point sampling method the changeable variable and fragile nature of snow creates unique sampling challenges in this paper we present star an efficient field usable method for use in point sampling spatial studies we validate the accuracy of the star method using a comparative monte carlo simulation of 1024 detailed samples of elevation data as spatial snow studies generally attempt to find spatial continuity in layers and other properties we use variogram ranges to compare the ability of four sampling methods to accurately reveal such spatial correlation the three methods compared to star represent gridded gridded random and pure random methods star can be described as a linear random method the simulation shows star s accuracy to be comparable to both gridded and gridded random methods following this comparative process we introduce a new measure of appropriateness for sampling methods the correct convergence on a variogram model which we call correct spatial correlation detection this directly measures how many sampled areas become correctly classified with either spatially correlated or non correlated variance for a given variogram model fit in this measure star performs equivalently to the other methods and in correct convergence it performs as well as pure random sampling

3d computational simulation based mineral prospectivity modeling for exploration for concealed fe cu skarn type mineralization within the yueshan orefield anqing district anhui province china abstract the yueshan orefield is one of the best known fe cu orefields in china and is located within the central yangtze metallogenic belt ofin anhui province china the recent discovery of the skarn type zhuchong fe cu deposit at depth within the orefield has highlighted the prospectivity of this area to host deep seated skarn type mineralization however the effectiveness of traditional geophysical exploration techniques is reduced with increasing depth this combined with recent developments in 3d mineral prospectivity modeling has led to the use of a 3d targeting approach for exploration for deep seated and concealed mineralization in this area however to date the usefulness of this approach has been limited by a lack of an approach that could generate more useful 3d predictive maps this study presents a 3d computational simulation based mineral prospectivity modeling approach that identified several exploration targets for concealed and deep seated skarn type mineralization within the yueshan orefield these prospective targets include areas of known mineralization as well as a number of new targets for future mineral exploration in addition the analysis of the resulting data using a capture efficiency curve indicates that these 3d computational simulation approaches can provide additional predictive information for mineral exploration indicating that 3d computational simulation should have a key role in the development and use of future 3d prospectivity modeling techniques during exploration targeting

sandbox experiments of inverted listric and planar fault systems abstract the kinematic and geometric evolution of basement controlled inversion structures has been analyzed using a plane strain sandbox apparatus the results of two representative scaled analogue models comprising rigid listric and planar detachment faults that both have cut off angles of 60 to the horizontal are described in detail the hangingwall above these detachment geometries was constructed from alternate layers of sand and mica in order to simulate an anisotropic sedimentary sequence in both experiments initial shortening at the onset of inversion was accommodated by bulk strain this was followed by reactivation of the basal detachment together with the main basin controlling planar and listric faults which propagate upwards through the post rift sequence at approximately the same angle as the upper part of the detachment fault i e 60 reactivation of relatively steep intra basinal extensional faults within the cover was restricted to nucleation of reserve faults and thrusts in the region of the tips during approximately the first 10 to 15 contraction this resulted in gently dipping thrusts that propagated upwards through the post rift sequence to produce harpoon shaped structures later in the inversion phase after approximately 15 contraction backthrusts cut through and displaced the original antithetic extensional graben faults producing downward tapering wedge shaped structures at the margins of the basin although deformation in these experiments was limited to purely dip slip displacement the nature of the original extensional faults and their reactivated tip regions resulted in cross sectional geometries that have a marked resemblance to strike slip induced flower structures uplift was asymmetric and centred above the upper part of the main detachment above the listric fault but was more symmetrical and centred above the soling out point of the detachment in the case of the planar fault geometry the results of these experiments show distinct similarities to structures seen on seismic sections form the southern north sea and other inverted sedimentary basins

selective reverse reactivation of normal faults and deformation around reverse reactivated faults in the mesozoic of the somerset coast abstract normal faults exposed in the triassic jurassic limestones and shales of the somerset coast were formed during the mesozoic development of the bristol channel basin reverse reactivation of some of these normal faults occurred during late cretaceous to early tertiary north south contraction the contraction is also evident from thrusts and conjugate strike slip faults preferential reactivation of the normal faults is attributed to 1 decreased fault plane friction 2 domino block rotation 3 displacement magnitude and 4 fault connectivity the geometries of overlapping and underlapping zones in reactivated fault zones are dependent on the existing structural geometry two distinctive styles of displacement accommodation occur between reverse reactivated normal faults 1 formation of a network of strike slip faults conjugate about nne ssw and 2 oblique steeply dipping reverse faults interaction between strike slip and an existing fault is dependent on whether the normal fault was reactivated the range of structures related to the north south contraction has been incorporated into a single deformation model controlled by the northwards movement of the hanging wall of the quantock s head fault pure dip slip movement occurred in the centre of its curved fault trace with a sinistral component at the western tip and a dextral component of displacement and strike slip block rotations occurred at the eastern tip shortening of these blocks was achieved through development of a strike slip fault network and nw striking thrusts in an underlap zone loading of the footwall by the hanging wall block modified the local stress system to allow formation of oblique steeply dipping reverse faults

fault propagation folding in extensional settings examples of structural style and synrift sedimentary response from the suez rift sinai egypt field data from the oligocene miocene gulf of suez rift demonstrate that coeval growth faults folds and transfer zones exerted a major control on synrift stratigraphic sequence development growth folds in the suez rift are related to steeply dipping normal faults that propagated upward resulting in broad upward widening monoclines in overlying strata folding during fault propagation was accommodated by layer parallel slip and detachment along mudstone horizons as well as by normal and rare reverse secondary faults that propagated away from the master fault the eventual propagation of the master fault through to the surface left the steep limb of the monocline and most of the secondary faults in the hanging wall this evolving structural style exerted a marked control on the geometry and stacking patterns of coeval synrift sediments synrift sediments display onlap and intraformational unconformities toward the growth monoclines and buried faults whereas they diverge into broadly synclinal expanded sections away from the growth monocline continued movement across buried faults resulted in the progressive rotation of the monoclinal limb and associated synrift sediments each successively younger sequence dipping basinward at a shallower angle than the previous one the resulting synrift geometries differ significantly from stratal geometries normally anticipated adjacent to normal faults along strike variations in facies stacking patterns are also commonly associated with decreasing displacement across faults and associated folds toward low relief transfer zones data from other rift basins indicate that fault propagation folds are not unique to the gulf of suez

the luanchuan mo w pb zn ag magmatic hydrothermal system in the east qinling metallogenic belt china constrains on metallogenesis from c h o s pb isotope compositions and rb sr isochron ages abstract the luanchuan mo w pb zn ag polymetallic ore district is located in the east qinling metallogenic belt on the southern margin of the north china craton two ore fields nannihu and yuku are recognized in the district and three types of deposits are identified from the two ore fields as follows 1 the 6 proximal porphyry skarn type mo w deposits occurring at the inner contact zone of the granite porphyries 2 the 3 middle skarn hydrothermal type zn deposits and 3 the 8 distal hydrothermal type pb zn ag deposits at the periphery of the porphyry we present c h o isotope compositions of hydrothermal quartz and calcite s pb isotope compositions of sulfide minerals and sphalerite rb sr isochron ages from the 17 deposits the geochemical and geochronological data from the two ore fields all show systematic temporal and spatial variation and primarily lead to the following inferences 1 the temperatures and salinities of the ore forming fluids decreased during mineralization the ore forming fluids gradually evolved from magmatic water to mixed magmatic meteoric water 2 the metallogenic components were primarily derived from igneous rocks with increasing proportions of the materials from the ore bearing rocks 3 the mineralization ages of these deposits are close 147 136 ma which correspond to the emplacement of the granite intrusions 4 the three types of deposits and the ore related late mesozoic intrusives constitute a unified magmatic hydrothermal mineralization system finally we also suggest exploration strategies for the luanchuan ore district

integrated seismic texture segmentation and cluster analysis applied to channel delineation and chert reservoir characterization in recent years 3d volumetric attributes have gained wide acceptance by seismic interpreters the early introduction of the single trace complex trace attribute was quickly followed by seismic sequence attribute mapping workflows three dimensional geometric attributes such as coherence and curvature are also widely used most of these attributes correspond to very simple easy to understand measures of a waveform or surface morphology however not all geologic features can be so easily quantified for this reason simple statistical measures of the seismic waveform such as rms amplitude and texture analysis techniques prove to be quite valuable in delineating more chaotic stratigraphy in this paper we coupled structure oriented texture analysis based on the gray level co occurrence matrix with self organizing maps clustering technology and applied it to classify seismic textures by this way we expect that our workflow should be more sensitive to lateral changes rather than vertical changes in ref

fault development and stress evolution of the post hercynian asturian basin asturias and cantabria northwestern spain abstract the asturian basin an emerged part of the north iberian continental margin has been investigated in terms of fault development and stress evolution the mesozoic history of this domain is mainly linked to the extensional faulting processes which preceded the opening of the bay of biscay preserved jurassic faulted blocks and associated half graben structures bounded by wnw ese to nw se faults are related to a late jurassic kimmeridgian rifting stage this fault system seems to have played a major role during the mesozoic structuring of the basin suggesting an extension oriented approximately ne sw the cenozoic evolution is related to the iberia eurasia convergence and collision leading to compressional and subsequent extensional structures the direction of compression documented in various sites was nnw sse during an initial early middle eocene stage reoriented probably in the oligocene to ne sw this succession of stress regimes was applied to the same three major fault systems ne sw nw se and e w which were inherited from the variscan orogeny some of them having already been involved in the latest stephanian early permian rifting episode during the tertiary compressional phase the nw se trend which is believed to have controlled the late jurassic tectonic development was rejuvenated into dextral strike slip faults whereas the ne sw system moved in a sinistral sense the e w system was reactivated as reverse faults giving rise to a partial inversion of the basin

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

linked sequence stratigraphic and structural evolution of propagating normal faults two distinct phases in the structural evolution of normal faults can be identified in the miocene gulf of suez rift 1 an initial growth fold stage when the fault is a buried structure and 2 a subsequent surface faulting stage during the growth fold stage strata thin and become truncated toward the fault zone and are rotated and diverge away from the buried fault into growth synclines in contrast once the fault breaks surface strata form a divergent wedge which is rotated and thickens into the fault the two tectono stratigraphic styles also occur contemporaneously along the length of a single fault segment growth folding characterizes deformation around the ends of fault segments where the fault is blind whereas the center of fault segments are characterized by surface faulting these observations suggest that marked along strike variation in stratal surfaces and facies stacking patterns will occur in depositional sequences in areas of normal faulting

tectonic implications from re os dating of mesozoic molybdenum deposits in the east qinling dabie orogenic belt abstract the east qinling dabie molybdenum belt is part of a larger east west trending metallogenic belt in eastern china most of the molybdenum deposits occur as porphyry or porphyry skarn type but there are also some vein type deposits following systematic re os dating of molybdenite from 13 deposits and comparisons with two previously dated deposits we have recognized that the molybdenum mineralization in the east qinling dabie belt was developed during hydrothermal activity linked to magmatism and the emplacement of granitoid stocks three pulses of granitoid magmatism and mo mineralization are recognized corresponding to significant tectonic events in the east qinling dabie belt vein type deposits dated at 233 221 ma were formed in detachment fractures indicating localized extension within the collisional setting of the north china and yangtze cratons i type and transitional i and s type granites and related mineralization dated at 148 138 ma may have formed part of a continental magmatic arc with widespread magmatism and back arc extension caused by subduction of the izanagi or paleopacific plate beneath the eurasian continent in a wnw ese direction in the late jurassic early cretaceous both s type and transitional s and i type granite associated porphyry molybdenum deposits dated at 131 112 ma are part of an extensive mineralization event throughout east china that can be ascribed to regional large scale lithospheric thinning delamination and thermal erosion

controls on carbonate platform evolution on active fault blocks the lower cretaceous castro urdiales platform aptian albian northern spain abstract four contrasting carbonate sequences developed in a tectonically active extensional setting in the lower cretaceous aptian albian castro urdiales platform of north spain the four carbonate phases p1 p4 early aptian late aptian earliest albian and early late albian respectively are identified across the platform to basin transition on the basis of sedimentary geometries and internal facies patterns they are vertically separated by four incipient drowning events d1 d4 middle aptian aptian albian boundary early albian and late albian the first carbonate stage p1 corresponds to a low relief carbonate platform characterized by widespread shallow marine depositional environments with a nearly flat organization the second platform stage p2 developed as a rimmed carbonate platform the third carbonate stage p3 evolved from a low relief aggradational platform substage a to a progradational offlapping platform substage b and back to a backstepped aggradational rimmed platform substage c responding to changes in differential subsidence and carbonate production at the beginning of the albian the castro urdiales carbonate platform was broken up by extensional tectonic movements with formation of fault blocks bounded by ne sw and nw se trending faults on the crests of uplifted blocks meteoric processes were active whereas grabens and half grabens acted as channel conduits for terrigenous rich deposits subsidence rates increased during the late early albian late albian the crests of rotated blocks formed paleohighs that nucleated small residual carbonate platforms carbonate stage p4 that were surrounded by deeper water basins this study suggests that the evolution of carbonate platform sequences in the lower cretaceous of castro urdiales was primarily controlled by changes in accommodation space which were most likely driven by intraplate stresses related to extension in the north spanish continental margin during the opening of the north atlantic drowning events in the castro urdiales platform coincide with major crises of cretaceous carbonate production worldwide suggesting that regional tectonism and global oceanic changes interacted to cause phases of platform demise

delineation of potential exploration targets based on 3d geological modeling a case study from the laoangou pb zn ag polymetallic ore deposit china abstract the laoangou pb zn ag polymetallic ore deposit lag is a hydrothermal vein type deposit in the east qinling polymetallic metallogenic belt which is controlled by nw ne and nearly sn trending faults and mainly hosted in the dolomite marble of meiyaogou and baishugou formations within the luanchuan ore district lod although district scale metallogenic prediction related to the pb zn ag deposits in the lod has been attempted there have been no studies to formulate a detailed deposit scale metallogenic prediction of the pb zn ag deposit in 3d space here we selected the lag to formulate a metallogenic prediction model for pb zn ag deposit based on data from 1 10 000 scale geological map and 66 boreholes and 39 sections of exploration lines on 1 1000 scale to extract the salient spatial features of the deposit we apply ordinary weights and weighted weights of evidence followed by boosted weights of evidence logistic regression and information entropy for integrating the features of the ore deposit for exploration targeting the c v fractal method is applied to classify the probabilities accordingly three levels of exploration targets are delineated the first level targets are mainly distributed in the periphery of known orebodies m2 m3 ii 3 and vi which are also located in the ore controlling strata and fault zones the second level targets are located in the region of known orebodies indirectly confirming that the prediction result is reliable and the third level targets which are mainly located at the contact between ore controlling strata and metagabbro bodies offer new targets for exploration in this ore district combining our results obtained in this study with those in previous studies we provide some guidelines for exploration targets in the pb zn ag deposits in the lod which might help in more effectively delineating the target zones

3d geological modeling for prediction of subsurface mo targets in the luanchuan district china abstract three dimensional 3d district scale geoscience information for the luanchuan mo district was integrated for understanding the development of its regional geology and ore forming processes and for decision making about potential targets for mineral exploration the methodology and datasets used were 1 construction of an initial geological model 25 km 20 km 2 5 km using 1 10 000 scale geological map nine geological cross sections and gravity and magnetic data 2 construction of three large scale mo deposits model 5 km 4 km 2 5 km using 1 2000 scale geological and topographic maps 288 boreholes total core length of 158 700 m and 32 1 2000 scale cross sections 3 3d inversion of 1 25 000 scale gravity and magnetic data for identification metallogenic anomaly zones which are associated with jurassic intrusions 4 extraction of ore controlling formation and sequence of the luanchuan group using the large scale 3d models of mo deposits and results of analysis of lithogeochemical samples from outcrops and borehole cores 5 identification of ore forming and ore controlling faults using the large scale 3d model of mo deposits and mineralized jurassic granite porphyry stocks 6 boost weights of evidence and concentration volume c v fractal analyses to integrate metallogenic information and to identify and classify potential mo targets four classes of exploration targets were identified using c v modeling and 3d known orebodies model the first and second class targets are mainly located in three large magma skarn type deposit camps occupying 1 4 km3 with total estimated reserve of 2 3 mt the third class targets which are mainly located in huangbeiling and yuku deposit camps comprising concealed magma skarn type deposits occupy 2 8 km3 and represent a new target exploration zone in the luanchuan district the fourth class targets which are located in the huoshenmiao majuan and daping zones occupy 15 km3 and represent potential mineral resources with likely similar orebody features as the yuku deposit

exploration targeting for orogenic gold deposits in the granites tanami orogen mineral system analysis targeting model and prospectivity analysis abstract a major challenge for mineral exploration geologists is the development of a transparent and reproducible approach to targeting exploration efforts particularly at the regional to camp scales in terranes under difficult cover where exploration and opportunity costs are high in this study a three pronged approach is used for identifying the most prospective ground for orogenic gold deposits in the paleoproterozoic granite tanami orogen gto in western australia a key input to the analyses is the recent development of a 4d model of the gto architectural evolution that provides new insights on the spatio temporal controls over orogenic gold occurrences in the area in particular on the role of pre mineralization pre 1795 ma d gtoe d gto1 d gto2 architecture in localization of gold deposits and the spatial distribution of rock types in 3d this information is used to build up a model of orogenic gold minerals system in the area which is then integrated into the three mutually independent but complementary mineral prospectivity maps namely a concept driven manual and fuzzy analysis and a data driven automated analysis the manual analysis involved 1 generation of a process based gold mineral systems template to aid target selection 2 manual delineation of targets 3 manual estimation of the probability of occurrence of each critical mineralization process based on the available information and 4 combining the above probabilities to derive the relative probability of occurrence of orogenic gold deposits in each of the targets the knowledge based geological information system gis analysis attempts to replicate the expert knowledge used in the manual approach but queried in a more systematic format to eliminate human heuristic bias this involves representing the critical mineralization processes in the form of spatial predictor maps and systematically querying them through the use of a fuzzy logic model to integrate the predictor maps and to derive the western gto orogenic gold prospectivity map the data driven empirical gis analysis uses no expert knowledge instead it employs statistical measures to evaluate the spatial associations between known deposits and predictor maps to establish weights for each predictor layer then combines these layers into a predictive map using a weights of evidence wofe approach application of a mineral systems approach in the manual analysis and the fuzzy analysis is critical potential high value targets identified by these approaches in the western gto lie largely under cover whereas traditional manual targeting is biased to areas of outcrop or sub crop amenable to direct detection technology such as exploration geochemistry and therefore towards areas that are data rich the results show the power of combining the three approaches to prioritize areas for exploration while the manual analysis identifies and employs human intuition and can see through incomplete datasets it is difficult to filter out human bias and to systematically apply to a large region the fuzzy method is more systematic and highlights areas that the manual analysis has undervalued but lacks the intuitive power of the human mind that refines the target by seeing through incomplete datasets the empirical woe method highlights correlations with favorable host stratigraphy and highlights the control of an early set of structures potentially undervalued in the knowledge driven approaches yet is biased due to the incomplete nature of exploration datasets and lack of abundant gold deposits due to the extensive cover the results indicate that the most prospective areas for orogenic gold in western gto are located in the central part of the study area largely in areas blind to previous exploration efforts according to our study the procedure to follow should be to undertake the analyses in the following order manual prospectivity analysis followed by the conceptual fuzzy approach followed by the empirical gis based method undertaking the manual analysis first is important to prevent explorationists from being biased by the automated gis based outputs it is however emphasized that all of the prospectivity outputs from these three methods are possible and they should not be treated as treasure maps but instead as decision support aids therefore a final manual prospectivity analysis redefined by the mutual consideration of output from all of the methods is required the strategy employed in this study constitutes a new template for best practice in terrane to camp scale exploration targeting that can be applied to different terranes and deposit types particularly in terranes under cover and provides a step forward in managing uncertainty in the exploration targeting process

sandbox experiments on basin inversion testing the influence of basin orientation and basin fill analogue modelling experiments using brittle materials are performed to study the inversion of extensional structures asymmetric grabens of two different orientations are first created during a phase of extension and progressively filled they are subsequently shortened in the same direction the aim of our experiments is to determine factors affecting the style of deformation during inversion we specifically investigate variations in thickness and distribution of strong and weak layers constituting the graben fill and in initial basin orientation the main advantage of our experimental set up is that we have a complete control on graben location width infill and orientation before inversion the experiments show that shortening results only in limited reactivation of pre existing normal faults in general forward thrusts and backthrusts cut across normal faults into the footwall of the graben the forward thrusts either propagate parallel to the enveloping surface of faulted blocks or they cut across basin limiting normal faults at various angles the graben fill is mechanically extruded by displacement along forward thrusts that accommodate most of the shortening both pre existing faults and weak graben fill act as zones of weakness during inversion and determine the orientation and location of both backthrusts and forward thrusts the results of our experiments conform well to natural examples of inverted graben structures

a new 3d geological model and interpretation of structural evolution of the world class rio tinto vms deposit iberian pyrite belt spain abstract a new 3d geological model and interpretation of structural evolution of the rio tinto world class vms deposit are presented in this work the rio tinto volcanogenic massive sulfide vms deposit is located in the spanish segment of the iberian pyrite belt and is hosted by felsic porphyritic volcanic rocks and tuffs computer generated 3d modeling of the different orebodies and host rocks has been carried out using data from around 3000 drill core logs allowing us to build 93 cross sections and 6 plants both 50 m spacing this has enabled us to recognize the geometry and relationships between the mineralization and the earliest carboniferous transtensional tectonics through the development of an extensional pull apart basin with two sub basins separated by the nw se trending eduardo fault the sub basins cerro colorado and san dionisio were limited by two e w strike slip faults the northern and southern faults and bounded in the east and west by the nw se trending nerva and western faults respectively the generated pull apart basin was first filled by a basaltic magmatism of mantle origin and later following the deposition of the intermediate complex sedimentary unit by rhyodacitic volcanic rocks of crustal origin the evolution of the subsiding basins caused the development of an e w oriented rollover anticline that affected these filling rocks as a result of a counterclockwise rotation of the stress axes the primitive pull apart basin evolved into a basin affected by e w transtensional sinistral shearing its northern and southern limits were favorable areas for increased hydrothermal fluid flow which gave way to the huge concentration of vms mineralization located near the limits the northern and to a lesser degree the southern extensional faults thus become channel areas for feeding and discharging of the vms and stockwork ores the main mineralizing period was related to this stage subsequently during the variscan transpressional phase the e w extensional faults were reactivated as inverse faults affecting the volcanic sequence of mafic to felsic composition and the intermediate complex sedimentary unit fault propagation folds developed above these faults affecting the massive sulfides the transition series and the culm flysch sediments with buttressing playing a significant role in the geometry of tectonically inverted structures the vms mineralization and cupriferous stockworks were folded and dismembered from the original conduits in the volcanic series and a dextral reactivation of the nw se trending faults also developed finally it should be emphasized that this new 3d geological model is an approach to provide a better insight into the 3d structure of the world class vms rio tinto deposit and could be a key point for further studies providing a new tool to increase knowledge of the vms mineralizations and exploration guidelines elsewhere in the ipb

geochemistry and geochronology of ore bearing and barren intrusions in the luanchuan ore fields of east qinling metallogenic belt china diverse tectonic evolution and implications for mineral exploration abstract the luanchuan ore fields form part of the east qinling metallogenic belt in central china in this study we compare two ore bearing intrusions the shibaogou granitic pluton sbg and the zhongyuku granitic pluton zyk with the ore barren laojunshan intrusion ljs from the luanchuan ore field geochemically all the three intrusions are characterized by high si high k and alkalis together with moderate asi exhibiting i type granite features the rocks especially the ore related plutons also show enrichment in lrees mineral chemistry of biotite from the intrusions exhibits similar features of high si and mg and low al and fe zircon grains from the zyk intrusion yielded a u pb age of 149 6 2 4 ma the zircon grains show ehf t values and two stage model ages tdm2 in the range of 16 8 to 19 7 and 1998 2156 ma respectively the biotite composition and hf isotopic data indicate that the magma was derived by re melting of deep crustal material with minor input of mantle components we evaluate the results to understand the physico chemical conditions petrogenesis and tectonic setting and their implications for mineral exploration the ore bearing plutons show wide ranges of temperature and oxygen fugacity favoring mo w mineralization in addition estimates on pressure and depth of emplacement suggest that lower solidification pressure in a decompressional setting contributed to the evolution of magmatic hydrothermal deposits our data suggest that the zyk has the highest potential for mo w mineralization the ore bearing plutons of zyk and sbg were formed in a transitional tectonic setting from compression to extension with the large scale metallogeny triggered by slab melts at ca 145 ma however the ore barren ljs batholith formed in an extension related geodynamic setting at 115 ma our study shows that different tectonic settings and consequent physico chemical conditions dictated the ore potential of the intrusions in the luanchuan ore district

mapping of prospectivity and estimation of number of undiscovered prospects for lode gold southwestern ashanti belt ghana in the southwestern part of the ashanti belt the results of fractal and fry analyses of the spatial pattern of 51 known mines prospects of mostly lode gold deposits and the results of analysis of their spatial associations with faults and fault intersections suggest different predominant structural controls on lode gold mineralisation at local and district scales intersections of nne and nw trending faults were likely predominantly involved in local scale structural controls on lode gold mineralisation whilst nne trending faults were likely predominantly involved in district scale structural controls on lode gold mineralisation the results of the spatial analyses facilitate the conceptualisation and selection of spatial evidence layers for lode gold prospectivity mapping in the study area the applications of the derived map of lode gold prospectivity and a map of radial density of spatially coherent lode gold mines prospects results in a one level prediction of 37 undiscovered lode gold prospects the applications of quantified radial density fractal dimensions of the spatial pattern of spatially coherent lode gold mines prospects result in an estimate of 40 undiscovered lode gold prospects the study concludes finally that analysis of the spatial pattern of discovered mineral deposits is the key to a strong link between mineral prospectivity mapping and assessment of undiscovered mineral deposits

controls on mineral deposit occurrence inferred from analysis of their spatial pattern and spatial association with geological features in this paper point pattern analysis fractal analysis and fry analysis were employed to study the spatial pattern of known occurrences of mineral deposits of the type sought whereas distance distribution method was applied to study the spatial associations between various geological features and known occurrences of mineral deposits of the type sought in the aroroy district philippines the results of the applications of these spatial analytical techniques support a conceptual model of district scale mechanism of geologic controls on low sulphidation epithermal au mineralization which involves a more or less regular mesh of interlinked zones of extension faults fractures at and or around intersections of nnw and nw trending strike slip faults fractures integration of spatial evidential data layers representing these structural controls and surficial geochemical anomalies via knowledge guided application of data driven evidential belief functions results in delineation of prospective areas occupying about 25 of the district in which there is about 70 likelihood of undiscovered occurrences of low sulphidation epithermal au deposits

iberian plate motions during the mesozoic abstract as more data are collected on the deep parts of the conjugate margins of canada and eurasia models of the early kinematics of iberia become better constrained in order to specify the motions during phases of continental rifting to the west and to the north of iberia we used recent data on the early oceanic spreading in the tagus abyssal plain and added simple assumptions on the geometry the tagus abyssal plain was formed after the end of continental rifting on the southwest portuguese margin in latest jurassic time before chron m 0 118 ma as a first step we close the space adjacent to the m 0 anomaly to keep open only the oldest oceanic part of the tagus plain which is assumed to be latest jurassic to earliest cretaceous in age in a second step we close this space the main results are as follows 1 1 the galicia bank slid along the southern flank of flemish cap this motion is interpreted as a strike slip motion or as a very oblique rifting 2 2 a late jurassic reconstruction of iberia and north america is obtained without considerable overlap and without large motion of microplates such as galicia bank this is possible because a large amount of continental extension occurred over a long time to the north of the grand banks and permitted early motion between north america and eurasia 3 3 a tight initial reconstruction can only be reached if strike slip motion is located between southern eurasia and northern eurasia along a shear zone following the english channel and the transform area between galicia bank and flemish cap

batholith stock scale exploration targeting based on multi source geological and geophysical datasets in the luanchuan mo polymetallic district china abstract the luanchuan mo polymetallic district which hosts world class porphyry skarn type mo w deposits is located in the qinling orogenic belt of the north china craton the mining depth of the porphyry skarn type mo w deposit in the luanchuan district is close to 550 m and most exploration drillholes extend to more than 1000 m the upper crustal architecture is important for understanding the geological setting and metallogenic model for mineral potential targeting on a district scale in this study subsurface intrusions and structures were defined using multi level gravity data processing i e bi dimensional empirical mode decomposition and geophysical inversion including gravity magnetotellurics and controlled source audio frequency magnetotellurics the results of our integrated geological and geophysical studies suggest that the late jurassic granite stocks are controlled by ne nee and nw nww striking faults the porphyry skarn type mo w deposits are distributed around the ore controlling late jurassic granite stocks which are connected to the granite batholith at depth the volume of this batholith is about 96 96 km3 based on geophysical interpretations and geochemical signatures of biotites from the granite stocks the metallogenic potential of the granite stocks at nannihu shangfanggou and huangbeiling is considered to be greater than that of the granite stocks at shibaogou yuku

part ii a demonstration of integrating multiple scale 3d modelling into gis based prospectivity analysis a case study of the huayuan malichang district china abstract this paper constitutes the second part of a study called mineral system modelling prospectivity analysis for mvt pb zn deposit in northwestern hunan province china the methodology is described in part 1 part 2 demonstrates the value of 3d modelling at the district and ore deposit scales the process employed in this paper is as follows i 3d models are constructed at multiple scales i e at the district and ore deposit scales ii an interpretation of the 3d models is presented based on a conceptual geological model iii a map of the mineral potential at depth relying on the conceptual geological model and 3d geometry data is delineated and discussed iv calculations of the volume and ore bearing ratio are improved using 3d geometry v the similarity coefficient used in part 1 is replaced with the quantitative uncertainty of the 3d models and vi the undiscovered mineral resources are estimated in the study area to be consistent with part 1 a case study of the mississippi valley type mvt pb zn mineralization in the huayuan malichang district 36 24 km 2 in northwestern hunan province china is conducted

extensional fault related folding northwestern red sea egypt the duwi and hamadat areas on the northwestern margin of the red sea rift system exhibit superb outcrop examples of kilometric scale extensional fault related folds in this area the nakheil and hamadat faults of the rift border fault system consist of a series of wnw and nw trending segments that link through breached relay ramps the fault hanging walls are characterised by a series of offset synclines with non linear axial traces sub parallel to the faults the synclines are doubly plunging and in the immediate hanging wall to the normal faults the strata dip sub parallel to the fault these folds result from along strike displacement variations on the individual fault segments together with extension related fault propagation folding as the faults propagated upwards through a highly anisotropic pre rift sedimentary section in the duwi area the axial traces of the synclines are offset and bend in the regions of relay ramps in the hamadat area the synclines associated with individual fault segments are separated by transverse hanging wall anticlines that formed where segment linkage occurred numerical simulations of extension related fault propagation folding using a trishear model produce geometries that closely match those of the duwi and hamadat folds the dimensions of these hanging wall synclines and their relationships to fault displacement variations indicate that they are formed by extensional fault propagation folding rather than by frictional drag along the fault surface

transpressional inversion in an extensional transfer zone the saltacaballos fault northern spain abstract this paper deals with an extensional transfer zone and its main structure the saltacaballos fault developed during early cretaceous times and obliquely inverted during the alpine shortening geological mapping and structural analysis were carried out to determine the kinematic history of the deformation the saltacaballos ridge is the relay zone between two major and conjugate normal fault systems the bilbao and the la granja samano fault systems three distinct phases in the structural evolution of this transfer zone can be identified 1 during the initial stages of extensional deformation shallow water marine limestones were deposited on the relay ridge and deep water marls on the flanking depocenters at the same time submarine landslides developed on paleoslope generated either by normal drag or by a fault propagation fold related to the saltacaballos normal fault 2 with increasing displacement normal faults antithetic to the saltacaballos fault were developed probably in response to the collapse of its hanging wall 3 during the subsequent alpine compressional stage these normal faults were reactivated as dextral strike slip faults as a result of transpressional inversion whereas previous extensional fault related folds were tightened at the same time some normal faults were overturned as a consequence of passive rotation in fold limbs

experimental models of extensional forced folds we have used single layer and multilayer clay models to study the development of forced folds above normal faults our modeling results show that the deformation patterns associated with extensional forced folding depend on the dip of the underlying normal fault and the presence of layer parallel detachments in single layer clay models extensional forced folds are upward widening monoclines anticlinal axial surfaces dip in the same direction as underlying master normal faults and synclinal axial surfaces dip in the opposite direction of master normal faults most secondary faults are upward steepening normal faults if master normal faults are steeply dipping however many secondary normal faults become high angle reverse faults at shallow depths the propagation and linkage of secondary faults into through going normal faults terminates the development of extensional forced folds more folding occurs prior to fault linkage if the master normal fault is steeply dipping rather than gently dipping most dipping beds and secondary faults are preserved in the hanging walls of the through oing normal faults in multilayer clay models with layer parallel detachments extensional forced folds are also upward widening monoclines slip on the lowest detachment laterally transfers extension induced by normal faulting and forced folding from the master normal fault to the detachment edge slip on overlying detachments accommodates minor thickness changes associated with upward widening of the fold secondary faults include low angle normal faults near the anticlinal axial surface minor thrust faults near the synclinal axial surface and high angle normal faults above the detachment edge the model predicted deformation patterns are similar to those of extensional forced folds from the gulf of suez and offshore norway this similarity suggests that our modeling results apply to extensional forced folds and can provide guidelines for interpreting field well and seismic data

graben inversion in nature and experiments the inversion of crustal scale basement grabens is studied here through laboratory experiments on small scale models and available oil industry seismic lines from the southern north sea two basic configurations are considered first both the basement and the sedimentary cover are brittle and inversion does not involve any potential decollement between them second the basement and sedimentary cover are separated by a weak ductile layer e g salt which can allow decollement of the cover during both extension and later compression and inversion the second configuration is more complicated and can lead to a large variety of geological structures laboratory experiments were carried out on brittle ductile models built with sand to represent brittle layers basement and sedimentary cover and silicone putty to simulate the decollement layer between basement and cover a mechanically based classification of inversion structures is proposed the effects of some crucial parameters are investigated including obliquity between the direction of shortening and normal faults as well as strength profiles and the presence or absence of salt diapirs the experimental investigation leads to the following conclusions 1 the inversion of the graben by reactivation of normal faults implies that the angle between the direction of compression and the graben is less than 45 2 if there is a superficial decollement e g basement cover interface inversion initiates low dipping thrust faults in the cover localized at graben borders 3 salt diapirs or salt walls localized along the graben borders in the cover are preferential sites for the development of thrust faults and 4 when the cover is decoupled from the basement by a decollement layer inversion induced deformation in the cover which is partitioned between thrust faults along the graben borders and strike slip faults within the graben trending oblique to the graben borders experimental results are compared with field examples in particular from the southern north sea

active normal faulting beneath a salt layer an experimental study of deformation patterns in the cover sequence scaled experimental models show that the presence of a viscous layer such as salt facilitates the development of extensional forced folds above active normal faults the geometries of the extensional forced folds and their associated secondary fault patterns depend on the thickness and viscosity of the viscous layer the thickness of the cover sequence the strength and ductility of the cover sequence and the magnitude and rate of displacement on the underlying master normal fault increasing the thickness of the viscous layer and the cohesive strength and ductility of the overburden enhances the decoupling between the deep and shallow deformation alternatively increasing the viscosity of the viscous layer the thickness of the overburden and the magnitude and rate of displacement on the master normal fault reduces the decoupling between the deep and shallow deformation enhanced decoupling facilitates the formation of broad extensional forced folds and the development of detached secondary faults both near and far from the master normal faults the model predicted deformation patterns closely resemble those observed in the gulf of suez the haltenbanken area of offshore norway and the jeanne d arc basin of the grand banks offshore southeastern canada

seismic evidence of alpine crustal thickening and wedging from the western pyrenees to the cantabrian mountains north iberia 1 the alpine collision between the iberian and european plates resulted in a complex crustal structure beneath the northern iberian peninsula as revealed from a new set of seismic refraction wide angle reflection profiles the study area is characterized by two major e w ranges the cantabrian mountains and the pyrenees which are relayed to the south by the iberian chain important variations in crustal thickness and velocity distribution are found in a 560 km long e w transect in contrast to the typical 30 to 32 km thick european variscan crust of the western end of the profile a continuous alpine crustal root is evidenced from the cantabrian mountains to the central pyrenees with a moho depth of 46 48 km locally rising to 40 km depth in between beneath the basque cantabrian basin another outstanding feature is the inferred presence of high velocities of 6 40 6 75 km s at midcrustal depths which can be associated with portions of a lower crustal wedge from the northern european domain indenting the southern iberian crust during the alpine stage of compression this indentation produces the delamination of the iberian crust with northward underthrusting of its lower half and the consequent crustal thickening the indenting wedge has a discontinuous presence along the longitudinal section as it was controlled and or affected by n s to ne sw structures further evidence of the northward subduction of the iberian plate is provided by another profile toward the aquitaine basin while a n s profile across the iberian chain reveals an alpine midcrustal thickening beneath this belt with moho depths of 42 km

kinematic modelling of extensional fault propagation folding abstract many studies have shown that in extensional basins discrete faulting at depth is commonly linked to more distributed deformation in particular folding at higher levels such extensional fault propagation folds are particularly common where there is a distinct mechanical contrast between faulted basement and sedimentary cover outcrop and analogue modelling studies indicate that such folds form as upward widening zones of distributed deformation monoclines above discrete faults at depth with increasing displacement strain the folds are cut by faults as they propagate upwards into the cover to date however there has been little investigation into the kinematics of linked basement faulting and extensional fault propagation folding here we present a two dimensional kinematic model of linked basement faulting and fault propagation folding which is based upon trishear the model allows investigation of the influence of shear zone geometry and the rate of fault propagation upon the style of folds and the strains associated with them the evolution of linked basement faulting and folding predicted by the model is compared in detail to that observed in an analogue model the kinematic model reproduces well many of the features seen both in the analogue model and reported from outcrop and seismic studies

metallogenic model of the wulong gold district china and associated assessment of exploration criteria based on multi scale geoscience datasets abstract the combined use of geological and geophysical modeling is effective for delineating subsurface exploration criteria and conducting quantitative analyses to determine potential mineral targets in this paper total horizontal derivative multi scale edge detection worms and bi dimensional empirical mode decomposition bemd of district scale gravity and magnetic data were applied to extract geophysical information reflecting deep seated structures and concealed intrusions in addition deposit scale 3d modeling and controlled source audio frequency magnetotelluric data were used to identify potential ore controlling structures the results of our integrated multi scale geological and geophysical studies suggest that the early cretaceous intrusions and gold deposits in the wulong gold district which is located on the liaodong peninsula china at the ne margin of the north china craton ncc are spatially and genetically associated with a network of ne and nw striking faults gravity and magnetic modeling effectively identified buried early cretaceous intrusions and nw striking faults at depths from zero to five kilometers in summary the combined use of multiple source and multi scale geophysical information and multi scale 3d geological modeling facilitated delineation of the metallogenic model and provided exploration criteria for determining potential exploration targets in the study area