weights of evidence method based on gis for assessing susceptibility to debris flows in kangding county sichuan province china assessing susceptibility to debris flows is of great importance for hazard prevention and mitigation kangding county a region with a high occurrence of destructive geological events was selected as the study area to evaluate the area s susceptibility to debris flows using the weights of evidence method based on arcgis first the determination method of training points was revised the unit cells covered by the debris flow catchments were set as the training points rather than using one point to represent the debris flow catchment then the landforms lithology faults earthquakes and river systems were selected as evidential themes for the analysis the optimum buffer zones cutoff distance of the faults and rivers was determined by the maximum studentized value of the contrast finally the map of the susceptibility to debris flow in kangding county was obtained by combining the evidential themes the susceptibility was categorized as low moderate and high susceptibility the low susceptibility zones cover an area of 6253 km2 accounting for 53 93 of the county area the moderate susceptibility zones cover an area of 3323 km2 accounting for 28 67 of the county area the high susceptibility zones cover an area of 2018 km2 accounting for 17 40 of the county area the moderate susceptibility zones surround the high susceptibility zones the assessment results agree well with field data demonstrating that the revised method is more suitable for debris flow assessment than the previous method the assessment results can be used as guidelines for policy makers regarding prevention and mitigation of debris flow hazards

on the structure of grain boundaries in tectonites abstract grain boundaries in several tectonites have been examined using high voltage and scanning transmission electron microscopy on a gross scale grain boundaries are observed to differ from the host crystal in exhibiting faster rates of preferential etching during ion beam thinning and faster rates of ionization damage during exposure to the electron beam grain boundary features can be grouped according to decreasing size as follows grain junction voids that can form linked networks of tubules arrays of isolated voids and inclusions along the grain boundary surface and a narrow grain boundary film of distorted crystal structure the presence of inclusions in voids and the propensity for electron damage along the boundary suggests that the former were initially fluid filled and that the latter may be hydrated initial microchemical analyses using stem indicate that no compositional difference exists between the grain boundaries and host crystals the overall complex grain boundary structure in tectonites suggests that the effective grain boundary width for intercrystalline diffusion is much greater than that proposed based on metals and that diffusion path lengths along grain boundaries are much less than the theoretical maximum the net effect is to greatly enhance deformation mechanisms dependent on intercrystalline mass transport

gis based mineral potential modeling by advanced spatial analytical methods in the southeastern yunnan mineral district china this paper demonstrates a modeling procedure of mineral potential mapping based on singularity theory and further presents an idea to look into metallogeny of sn cu polymetallic deposits in southeastern yunnan mineral district china by applying a localized regression method mineralization is a typical cascade process generally accompanied by irregular geological geochemical and geophysical signatures singularity index as an efficient anomaly analytical tool helps to identify anomalies as well as characterize formation processes of these anomalies in this study the singularity based mineral potential mapping method was utilized to characterize hydrothermal mineralization associated with magmatic tectonic and sedimentary processes in this district based on the results a mineral prospectivity model was constructed to delineate target areas in addition to mineral prospectivity controlling effects of geo processes on mineralization are spatially non stationary geographically weighted regression analysis was thus employed to investigate these spatially varied controlling effects and it has contributed to improve understanding to local metallogeny in the study area results of the spatial analysis presented can be used to guide following stages of mineral exploration in the district

mineral prospectivity analysis for bif iron deposits a case study in the anshan benxi area liaoning province north east china abstract banded iron formation bif deposits are the most important source of iron in china and they are dominantly distributed in the north china craton ncc the anshan benxi area is situated in the northeastern part of the ncc and is considered to be the most fertile and productive iron metallogenic province in china the recent successive discoveries of large bif deposits in this area especially the world class dataigou bif deposit indicates that there is great potential for iron resources in this area the bif deposits are well defined by magnetic and gravity anomalies and thereby extensive petrophysical and geophysical studies are critical for bif prospective mapping a data driven weights of evidence wofe analysis was used for bif prospectivity modeling the results indicated that prospective areas are generally confined to the precambrian greenstone belt basin and high prospectivity zones class a are mainly distributed in the middle and northeastern parts of the study area moderate prospectivity zones class b are mainly distributed in southwestern and northeastern parts of the study area finally we employed selective human intervention to redefine priority targets to be more reliable the results suggest the method is successful as 82 target areas were narrowed to class a 20 and 11 class b targets the total of class a and class b targets was just over one third of the total number of targets offering a much smaller but effective selection of targets for consideration by mineral explorers

morphology of intergranular pores and wetting angles in pelitic schists studied by transmission electron microscopy in pelitic schists composed mainly of quartz and albite grains the morphology of intergranular pores which were filled with water was studied by transmission electron microscopy tem although some pores are defined by crystallographic planes f face most of their form has an ideal shape determined by interface tensions between grains and fluid high resolution tem observations demonstrate that pore free regions at grain boundaries are tight even at the nanometer scale showing that the wetting angle is larger than 0 in this rock the pore distribution in two grain junctions can be compared to a necklace microstructure developed by instability of a fluid film along the boundary induced by microcracking wetting angles for pores located at grain edges of quartz and albite decrease in the order albite albite quartz quartz and quartz albite the quartz quartz wetting angle in a calcite free sample is smaller than that in a calcite containing sample this angle also changes due to grain misorientation our results confirm that solid solid and solid fluid interfacial energies control the geometry of intergranular fluid in natural rocks

simulation of geological processes using an expert system regional geological processes may be simulated rapidly using a combination of image processing and expert system techniques rapid interactive simulations are achieved with image processing and a reduction of the problem to the two map dimensions in order to manage these multiple simulations expert system software is used to infer the optimum path through the modelling options we illustrate our approach by referring to a computer system designed to produce maps of the prospectivity of carbonate hosted pb zn f ba buried mineralization in the east midlands of england the system simulates the process of mineralization near the end of the carboniferous involving the rapid expulsion of metal rich brines from a series of small shale basins by e w compressive tectonism there is preferential migration of these fluids along reactivated basin bounding faults and deposition of the metals as sulphides within neighbouring limestone platforms computer simulation using this or similar approaches has particular potential for multidisciplinary projects in regional geology where disciplinary expertise in handling different types of data and in performing the simulation needs to be replicated

spatial analysis and visualization of exploration geochemical data abstract this paper briefly reviews the application of geoinformatics in exploration geochemistry from the perspective of spatial analysis and visualization and demonstrates the advantages of geoinformatics in exploring geochemical patterns and identifying geochemical anomalies in particular the application of geoinformatics to geochemical mapping recognition of geochemical anomalies and simulation of geochemical patterns are discussed the benefits of geoinformatics include 1 overlay of geochemical data on a geological map which helps geochemists to understand spatial geochemical patterns and visualize geochemical anomalies 2 local neighbourhood spatial analysis which considers the local spatial structure of geochemical patterns as a powerful tool to identify weak geochemical anomalies and 3 geochemical patterns simulation based on geological constrains which helps to understand geological processes future researches should focus on development and application of various functions for processing geochemical data in a gis to promote the progress of geoinformatics in both geochemical exploration and environmental studies

the blue angel i the mineralogy and petrogenesis of a hibonite inclusion from the murchison meteorite a detailed mineralogie chemical and petrologic study of the blue angel a relatively large 1 5 mm hibonite containing inclusion from the murchison meteorite was performed in an attempt to understand the mechanisms of formation and modification of hibonite rich inclusions the blue angel inclusion is composed of roughly equal amounts of hibonite and calcite with minor amounts of spinel perovskite diopside and an fe rich silicate the inclusion can be divided into three roughly concentric zones a hibonite rich core a calcite rich mantle and a spinel rich layered rim the mineral chemistry and petrography of the blue angel are consistent with a three stage formation history 1 an early stage of nebular condensation which produced the hibonite perovskite and spinel 2 a moderate temperature stage of aqueous alteration and metamorphism occurring on a small planetary body containing co 2 and h 2o during which calcite was formed in the inclusion and 3 the final emplacement of the blue angel into its present position in murchison the study of the blue angel indicates that extensive alteration of ca al rich inclusions cai may have occurred by aqueous alteration and thermal metamorphism followed by explosive mixing processes on a parent body such metamorphic reactions may involve formation and destruction of phases such as melilite and diopside which have been previously thought to be primary condensates the mechanisms proposed for the formation and modification of the blue angel help to explain the secondary phases and oxygen isotope anomalies found in many cai and eliminate the need for invoking kinetically complicated back reactions at very low pressures with a cool part of the solar nebula the contribution of planetary metamorphism in the formation and alteration of cai must be considered along with nebular processes in order to understand the formation of carbonaceous chondrites

weight of evidence and artificial neural networks for potential groundwater spring mapping an application to the mt modino area northern apennines italy abstract locations of potential groundwater springs were mapped in an area of 68 km 2 in the northern apennines of italy based on weight of evidence wofe and radial basis function link net rbfln a map of more than 200 springs and maps of five causal factors were uploaded to arcgis with spatial data modelling extensions the wofe and rbfln potential groundwater spring maps had similar prediction rates allowing about 50 of the training and validation springs to be predicted in about 15 to 20 of the study area the two maps were merged using a heuristic combination matrix in order to produce two hybrid maps one representing susceptible areas in both the wofe and rbfln maps type a while the other representing susceptible areas at least in one of the two maps type b for small cumulated areas the success rate of both hybrid maps was higher than that of the parent maps while for large cumulated areas only the type b hybrid map performed similarly to the parent maps this conclusion suggests different applications of these maps to water management purposes

integrated gis based modelling for the quantitative prediction of magmatic ti v fe deposits a case study in the panzhihua xichang area of southwest china abstract the estimation of undiscovered mineral resources is an important part in the potential value of a mineral field and its long term use this manuscript documents six procedures for estimating the volume of potential mineral resources in an area that is based on integrated geological information forming part of a metallogenic model the technique for this methodology includes 1 the development a metallogenic model or models for mineral deposits in the study area 2 the integration of the characteristics of known mineral anomalies with geology geochemistry and geophysics to establish a predictive model for mineralization 3 the definition of possible mineral resources incorporating predictive models with characteristic analyses the knowledge driven delphi method and magnetic anomalies 4 calculate the parameters for the quantitative prediction areas of known mineral deposits and their estimated dip extension ore bearing coefficients and their similarity coefficients based on explored ore deposits in the area studied 5 complete quantitative predictions using an synthetic volumetric equation and 6 assess zones that are considered prospective for mineral resources the procedure is tested for magmatic ti v fe resources in a known mineralized zone in the sichuan province of china

comparison of 3d prospectivity modeling methods for fe cu skarn deposits a case study of the zhuchong fe cu deposit in the yueshan orefield anhui eastern china abstract three dimensional 3d metallogenic prospectivity modeling has become increasingly important in deep fe cu skarn mineralization prospecting the selection of prediction models and their comparison are of great significance in this paper we integrated the geological and geophysical data from the zhuchong fe cu deposit in the yueshan orefield anhui eastern china to establish the local 3d geological framework we extracted the 3d ore controlling factors quantitatively by means of 3d spatial analysis methods and compared the 3d mineralization locations predicted by the weight of evidence method and the artificial neural network method the results show that both methods can locate most of the known orebodies suggesting that both are relatively reliable in addition the weight of evidence method performed distinctly better than the artificial neural network method in terms of both prediction effectiveness and efficiency therefore the weight of evidence method may be more applicable in 3d prospectivity modelling for fe cu skarn deposits in the region finally the composite area predicted by the two methods is taken as the final prediction result of the mineralization area of the deposit and it is suggested that in the quantitative 3d prediction multiple selection of different methods with good adaptability should be involved in the prediction at the same time and compound prediction method should be used to delineate the target area our work has guiding significance for future deep prospecting and exploitation for other similar fe cu skarn deposits

imprinted textures on apatite a guide to paleoporosity and metamorphic recrystallization fluids play a key role in the transfer of both heat and mass within the crust and in the attainment of chemical equilibrium in metamorphic rocks controlling both reaction rates and deformation mechanisms however our understanding of fluid movement through the deep crust is limited because rocks readily recrystallize and fluids are invariably lost from grain boundaries little is known about how textures evolve during metamorphism since minerals rarely preserve much textural history that can be directly related to grain boundary processes here we report on a study of the surfaces of apatite within gneisses a variety of textural features is preserved on these surfaces including imprinted texture of fossil grain boundaries this texture is linked to deformation that caused a temporary excursion to fine grain size in the surrounding silicates the geometry of paleoporosity is also recorded by microhollows on the apatite surface and gives a unique insight into both fluid behavior within the crust and the textural evolution of rocks

mapping mineral prospectivity for cu polymetallic mineralization in southwest fujian province china abstract in this study both the fuzzy weights of evidence fwofe and random forest rf methods were applied to map the mineral prospectivity for cu polymetallic mineralization in southwestern fujian province which is an important cu polymetallic belt in china recent studies have revealed that the zijinshan porphyry epithermal cu deposit is associated with jurassic to cretaceous yanshanian intermediate to felsic intrusions and faulting tectonics evidence layers which are key indicators of the formation of zijinshan porphyry epithermal cu mineralization include 1 jurassic to cretaceous intermediate felsic intrusions 2 mineralization related geochemical anomalies 3 faults and 4 jurassic to cretaceous volcanic rocks these layers were determined using spatial analyses in support by geodas and arcgis based on geological geochemical and geophysical data the results demonstrated that most of the known cu occurrences are in areas linked to high probability values the target areas delineated by the fwofe occupy 10 of the study region and contain 60 of the total number of known cu occurrences in comparison with fwofe the resulting rf areas occupy 15 of the study area but contain 90 of the total number of known cu occurrences the normalized density value of 1 66 for rf is higher than the 1 15 value for fwofe indicating that rf performs better than fwofe receiver operating characteristics roc were used to validate the prospectivity model and check the effects of overfitting the area under the roc curve auc was greater than 0 5 indicating that both prospectivity maps are useful in cu polymetallic prospectivity mapping in southwestern fujian province

identifying gravity anomalies caused by granitic intrusions in nanling mineral district china a multifractal perspective several power law relationships of geophysical potential fields have been discussed recently with renewed interests including field value distance f r and power spectrum wavenumber p models the singularity mapping technique based on the density concentration area c a power law model is applied to act as a highpass filter for extracting gravity and magnetic anomalies regardless of the background value and to detect the edges of gravity or magnetic sources with the advantage of scale invariance this is demonstrated on a synthetic example and a case study from the nanling mineral district southern china compared with the analytic signal amplitude and total horizontal gradient methods the singularity mapping technique provides more distinct and less noisy boundaries of granites than traditional methods additionally it is efficient for enhancing and outlining weak anomalies caused by concealed granitic intrusions indicating that the singularity method based on multifractal analysis is a potential tool to process gravity and magnetic data

recognition of a hidden mineral deposit by an artificial intelligence program a computer program that uses artificial intelligence techniques has successfully identified the location of a porphyry molybdenum deposit given geological maps of readily available predrilling exploration data for mount tolman in washington state and using rules obtained from a porphyry molybdenum exploration specialist the program called prospector identified the location of previously unknown ore grade mineralization this appears to be the first reported determination of the location of mineralization by such a computer based approach

bayesian assessment of favorability for oil and gas prospects over the reconcavo basin brazil this paper presents a bayesian approach to evaluate remaining potential of oil and gas in the reconcavo basin brazil the purpose is to test a new bayesian weighting methodology and quantify the favorability for the existence of new fields in the basin the methodology implies organization of petroleum system data in descriptive models with which results from drilling are manipulated statistically including analysis of geologic factors that are spatially correlated with both producing and dry areas in the first stage of modeling the essential elements reservoir seal and overburden rocks that control the fundamental processes of generation expulsion migration and entrapment of petroleum accumulation are defined throughout integration of previously published data the petroleum accumulation models of reconcavo basin comprise generation from neocomian shale rocks of the gomo member candeias formation vertical migration along extensional and transfer faults and accumulation in tilted horsts with upper jurassic prerift reservoirs sergi formation or in neocomian turbidite reservoirs in stratigraphic combined traps candeias and marfim formations probability distributions and weights are then calculated through boolean operations among producing and dry areas and each diagnostic criterion evaluated through descriptive models such as source bed thickness onset of organic maturation presence or absence of faults and structural blocks reservoir thickness and seal distribution the final stage of evaluation consists of spatial integration of raster maps that are weighted according to their necessity and sufficiency conditions the results being presented as favorability maps the characterization of favorable areas and their comparison with known fields suggest that such a bayesian approach can contribute to the understanding of petroleum systems as a practical approach that considers the spatial nature of exploration variables

evaluation of uncertainty in mineral prospectivity mapping due to missing evidence a case study with skarn type fe deposits in southwestern fujian province china in this paper the southwestern fujian metallogenic belt one of the important fe polymetallic belts in southern china was chosen as a case study area to evaluate the uncertainty due to missing evidence in mineral prospectivity mapping four geological features were considered important for mineral prospectivity mapping based on the geological model for skarn deposits in the belt 1 the yanshanian granitic intrusions because they provided energy fluids and part of the metal budget 2 faults because they served as pathways for hydrothermal fluids 3 the carboniferous permian carbonate sequences because they supplied part of the metal budget and served as host rocks for ore deposition and 4 geochemical anomalies because they indicate presence of skarn type alteration and mineralization four separate predictive evidence layers depicting each the above geological features were extracted from relevant geoscience data and were integrated using a modified fuzzy weights of evidence model which retains the advantages of both fuzzy weights of evidence and logistic regression modeling the results show that most of the known fe deposits occur in or near and thus have strong correlation with areas of high posterior probabilities as indicated by the delineated prospective areas that occupy only 4 6 of the studied region but contain 88 5 of the total number of known fe deposits different combinations of predictive evidence layers were used to examine prediction uncertainty related to missing evidence plots of accumulative number of fe deposits versus accumulative prospective areas show that the order of the most to the least important evidence of mineral prospectivity in the studied region is favorable rock types geochemical anomalies intrusive rocks faults results of blind testing the prospectivity models indicate that the geological model of fe mineralization in the belt is suitable for predicting exploration target areas for skarn type fe deposits and suggest that the highest risk in follow up exploration is related to sequences of carbonates in the carboniferous permian formations that were likely either not mapped or not represented at the present regional scale of mapping

a prediction model for important mineral resources in china abstract prediction models for mineral resources provide an analytical foundation and method to express the results of resource evaluations the project china national mineral resources assessment initiative was conducted during 2006 2013 with the aim to determine the location quantity and quality of 25 important mineral resources occurring at depths of

spatially quantitative characterization of geological processes associated with polymetallic sn w mineralization in the malipo mineral district southeastern yunnan china abstract the current geographic information system gis based mineral prospecting models focus on delineating high probability locations for mineral deposits these models do not attempt to characterize the geological evolution of the area under study either spatially or quantitatively the study described in this paper demonstrates an innovative approach that quantitatively describes the mineralization processes in a spatial way this improves predictions by adding information concerning the areas geologic evolution this study quantitatively characterizes the mineralization in the malipo mineral district china in relation to tectono magmatic activity from caledonian to yanshanian time these findings extend the existing geological knowledge of the study area a critical step for further investigating and interpreting the geochemical signatures the malipo mineral district is a well studied area and thus appropriate for evaluating a new modeling technique our preliminary results show that the quantitative spatial characterizations retrieved from our model offer highly correlated predictive information regarding geologic evolution when compared with the information obtained from traditional ground truthing investigations therefore employing our model in a new and under studied area would potentially provide significant benefits and advance the level of knowledge in the new area

apatite monazite and xenotime in metamorphic rocks this chapter focuses on phosphates that are significant in metamorphic rocks a quick survey of phosphate mineral descriptions at a commercial mineral web site revealed over 500 phosphate mineral names remarkably only three are common in metamorphic rocks apatite monazite and xenotime and this chapter is restricted to discussion of these minerals apatite monazite and to a lesser extent xenotime have enjoyed intensive study during the previous half century following world war ii considerable study was made of minerals that contain fissionable materials and the sometimes large concentrations of u and th in monazite culminated in a number of seminal papers on the occurrence of that mineral e g overstreet 1967 during the 1970s and early 1980s the study of apatite and monazite turned towards their role as a sink for rees and other trace elements in rocks e g watson 1980 watson and capobianco 1981 throughout this period monazite and to some extent xenotime enjoyed attention as a geochronometer e g parrish 1990 and through today this attention has continued to grow accessory minerals such as monazite xenotime and apatite have come to the forefront of research in metamorphic petrology in recent years for two reasons first it has recently been recognized that trace elements in metamorphic rocks and especially trace element zoning in garnet and other major phases contain considerable detailed information about the reaction history a rock has experienced coupled with the fact that diffusion of many trace elements in metamorphic minerals is in general considerably slower than diffusion of major elements in those same minerals the possibility has recently emerged of recovering details of metamorphic petrogenesis that were previously unattainable inasmuch as accessory minerals play a dominant role in the mass budget of many trace elements attention has naturally turned to their paragenesis it has also recently been discovered that