mass movements in tropical volcanic terrains the case of teziutlan mexico abstract during the last decade soil degradation coupled with global climate changes has increased hydrogeological hazards in mexico in tropical volcanic terrains alteration processes have enhanced the formation of clay minerals that promote water retention and result in soil rock weakness intense seasonal rainfall can trigger the liquefaction and remobilization of these low resistance terrains during the first week of october 1999 heavy rains affected eastern mexico including puebla state as a consequence approximately 3000 mass movements consisting of rock and soil slides and slips debris flows and avalanches were generated in this area in the town of teziutlan puebla which is located on volcanic deposits a single mass movement event caused approximately 150 deaths in the present work we identified two types of mass movements in the teziutlan area type 1 superficial erosion of an unwelded ignimbritic sequence forming small detrital fans and type 2 thin soil slide debris flow from the remobilization of a volcanic sequence composed of clay rich paleosols interbedded with ashfall horizons the clay rich volcanic paleosols favored the formation of perched water tables on a hydraulic aquiclude positive pore water pressures triggered the failure based on these results the principal human settlement in the teziutlan area may be threatened by future debris flows which could cause serious harm to the dense population and severe damage to its infrastructure it is necessary to prevent future deaths and damage by installation of mitigative measures based on detailed studies without any further study it will not be possible to prevent and mitigate a natural disaster with the same magnitude as the 1999 catastrophic hydrogeological phenomena

mapping geochemical anomalies related to fe polymetallic mineralization using the maximum margin metric learning method abstract geochemical anomaly identification is an important task in mineral exploration targeting this task can be regarded as a binary classification problem whereby the aim is to discriminate between anomalous and not anomalous i e background we can analyze geochemical data from the aspects of frequency distributions correlations and variances geometrical properties of geochemical anomalies and scale independence of geochemical patterns in this study we recognize geochemical anomalies based on the intrinsic relationship between geochemical elements which can be addressed by measuring their separation distance as a machine learning method metric learning aims at exploiting the statistical information between the geochemical features in limited training samples and developing a more suitable distance to evaluate the similarity of samples without priori distribution assumptions accordingly a metric learning method based on the maximum margin frame was applied to identify multivariate geochemical anomalies related to fe polymetallic mineralization in the southwestern fujian province of china the geochemical exploration data were firstly translated into a dimensional reduced subspace with the help of maximum margin metric learning mmml the adaptive coherence estimator ace detector from the field of target detection was then employed to identify geochemical anomalies the anomaly results obtained by this integrated procedure using a combination of mmml and ace were compared to those obtained by ace without metric learning using a receiver operating characteristic roc curve the area under the curve value implied superior performance using the combination of mmml and ace suggesting that this hybrid method can be effectively applied to recognize geochemical anomalies linked to mineralization

engineering aspects and time effects of rapid deterioration of sandstone in the tropical environment of sabah malaysia cut slopes in rock masses start to deteriorate directly after excavation due to stress relief and weathering the deterioration is a time dependent process that depends on the local climate and the rock mass including its history and the environment the amount of deterioration per time unit the weathering intensity rate is not a constant over time but is for most rock masses larger when the mass is less weathered and becomes smaller with further progressing weathering a study has been carried out to establish the relationship between weathering intensity rate and exposure time for the intact rock strength irs of sandstone in humid tropical areas the data set for the study was collected in and near kota kinabalu sabah malaysia which has a humid tropical climate the geology in the area consists of thick sequences of sandstone and shale beds of the crocker formation results show that the best relationship between intact rock strength irs and exposure time t is by a logarithmic function irs t 105 34 log 1 t this relationship can likely be used for prediction of the intact rock strength development of similar sandstone over the engineering lifetime of man made slopes in tropical areas

weathering mechanisms and their effects on the landsliding of ignimbrite subject to vapor phase crystallization in the shirakawa pyroclastic flow northern japan abstract ignimbrite which is consolidated by vapor phase crystallization is weathered in humid regions to form a special type of weathering profile that consists of a hydrated zone an exfoliated zone and a disintegrated zone from the depth to the ground surface with each zone having a basal front the ignimbrite is hydrated first and loses a significant amount of phosphorous at the hydration front where rock forming tridymite is dissolved and cristobalite is precipitated the ignimbrite further loses its alkali and alkali earth components at the top of the hydrated zone by reacting with reactive water from the exfoliated zone then the leached layers are exfoliated and become part of the exfoliated zone and then they soften significantly at the top of the exfoliated zone rock is disintegrated so completely that rock texture disappears water from rainstorms infiltrates down to the exfoliation front but penetrates only slightly further downward thus saturating the weathered rock in the exfoliated and disintegrated zones and leading to a landslide with a slip surface within the exfoliated zone

stream sediment geochemical data analysis for district scale mineral exploration targeting measuring the performance of the spatial u statistic and c a fractal modeling abstract recognition of mineralization related geochemical footprints and modeling their multi element dispersion patterns are important aspects to consider when vectoring toward undiscovered ore deposits the collection analysis and interpretation of stream sediment geochemical data together make an exploration method that has proven to be successful at the district scale mineral exploration targeting identifying the possible sources of stream sediment geochemical anomalies and mapping evidence i e footprints of the underlying ore forming processes however are not trivial tasks this is because stream sediment samples represent transported material reflecting the entire geology upstream from the sample locations furthermore indicator element distribution patterns are commonly strongly affected by local factors such as regolith topographic gradient vegetation density and or climate therefore there is a need for finding a better geochemical anomaly separation method regarding the nature of geochemical data obtained from the area sampled the main objectives of this study were 1 evaluating and comparing the spatial u statistic and concentration area fractal modeling methods of anomaly identification both amenable to spatial analysis for recognizing geochemical footprints of porphyry copper mineralization and 2 measuring their performance in the context of district scale exploration targeting in an area located in southeast iran subsequently the methods were first evaluated on a dataset of element contents to decompose anomalous populations finally the geochemical model that proved more efficient with respect to predicting the known mineral deposits was integrated with additional evidence maps to delineate exploration targets our evaluation of the resulting geochemical targeting model demonstrated that the targets derived from this method are robust and worthy of follow up exploration

multivariate spatial analysis of lake sediment geochemical data melville peninsula nunavut canada abstract a multivariate spatial analysis was conducted on a suite of glacial till geochemical data collected over the melville peninsula nunavut canada previous studies demonstrated through the application of multivariate statistical techniques that the composition of the lake sediment geochemistry reflects the underlying geology in northern canada in this study the application of minimum maximum autocorrelation factor analysis maf to glacial till geochemistry has extended the knowledge and description of the underlying geology through the recognition of spatially correlated factors that represent distinct lithologic features and glacial transport processes maps of posterior probabilities for the underlying lithologies were estimated based on the ma factors and compared with those from standard principal component analysis the use of maf provides a measured improvement in predictive mapping irrespective of the choice of lag separation

investigating high zircon concentrations in the fine fraction of stream sediments draining the pan african dahomeyan terrane in nigeria sixteen hundred stream sediments 150 m fraction collected during regional geochemical surveys in central and sw nigeria have high median and maximum concentrations of zr that exceed corresponding zr concentrations found in stream sediments collected from elsewhere in the world with similar bedrock geology x ray diffraction studies on a sub set of the analysed stream sediments showed that zr is predominantly found in detrital zircon grains however the main proximal source rocks pan african older granites of nigeria and their proterozoic migmatitic gneiss country rocks are not enriched in zircon or zr nevertheless u pb la icp ms dating with cathodoluminescence imaging on detrital zircons both from stream sediment samples and underlying pan african older granites confirms a local bedrock source for the stream sediment zircons a combination of tropical chemical weathering and continuous physical weathering both by wet season flash flooding and dry season unidirectional winds are interpreted to have effectively broken down bedrock silicate minerals and removed much of the resultant clay phases thereby increasing the zr contents in stream sediments the strong correlation between winnowing index th al and zr concentration across the study area support this interpretation therefore anomalous high values of zr as well as other elements concentrated in resistant heavy minerals in nigeria s streams may not reflect proximal bedrock concentrations of these elements this conclusion has important implications for using stream sediment chemistry as an exploration tool in nigeria for primary metal deposits associated with heavy minerals

landslides associated with spheroidally weathered mantle of granite porphyry induced by 2011 typhoon talas in the kii peninsula japan abstract typhoon talas brought heavy rain to the kii peninsula japan during 2 5 september 2011 causing hundreds of debris avalanches and debris flows in the southeastern part of the peninsula we undertook field investigations to understand the geological and geomorphological context of the landslides and found that the most important geological factor is spheroidal weathering of granite porphyry this granite porphyry is deeply weathered with corestones in higher elevations and forms low relief surfaces of which marginal areas were the major sources of debris avalanches corestones that failed were embedded in grus in situ or on nearby slopes of mudstone in which the granite porphyry intruded the corestones are made by spheroidal weathering from well developed columnar joints and sheeting joints sheeting joints in the source granite porphyry acted as sliding surfaces both before and during the occurrence of the 2011 debris avalanches

national scale estimation of potentially harmful element ambient background concentrations in topsoil using parent material classified soil stream sediment relationships regulatory authorities require estimates of ambient background concentrations abcs of potentially harmful elements phes in topsoil such data are currently not available in many countries high resolution soil geochemical data exist for only part of england and wales whilst stream sediment data cover the entire landscape a novel methodology is presented for estimating soil equivalent abcs for phes from high resolution hr stream sediment geochemical data grouped by common parent materials pm using arsenic as as an example geometric mean gm values for local pm groups are used to investigate different approaches for transforming sediment to soil equivalent concentrations holdout validation is used to assess i the optimum number of samples for calculating local gm values and ii the optimum scale at which to group data when using linear regression analysis to estimate gm soil abcs from local sediment geochemical values holdout validation showed that the smallest differences were generally observed when five observations were used to calculate the gm and that these should be grouped over the smallest possible area in order to encompass soils over pms with elevated gm as concentrations geometric mean abcs are estimated and mapped for as in mineral soil across all of england and wales within delineations of pm polygons errors for the estimation of soil equivalent gm as abcs based on sediment data for an independent validation set were of a similar magnitude to those from holdout validation applied to the original data suggesting the approach is robust the estimates of soil equivalent abcs suggest that as exceeds the regulatory threshold used in risk assessments for residential land use 20 mg kg1 across 16 of the landscape of england and wales the applicability of the method for cognate landscapes and potential refinements is discussed

weathering profile of non welded ignimbrite and the water infiltration behavior within it in relation to the generation of shallow landslides the mechanism underlying rain induced shallow landslides of non welded ignimbrite is found to be a special type of weathering profile and the behavior of water infiltrating through that profile according to our study of ito ignimbrite in southern kyushu japan rhyolitic volcanic glass the primary component of ignimbrite is first hydrated and dissolved forming halloysite halloysite near ground surface is then transported through the ignimbrite by infiltrating water and becomes clogged in interstices to form clay bands suction monitoring across a weathering profile indicated that downward infiltration of water is disrupted once by a zone of less permeable clay bands and again at the weathering front this disruption at the front is caused by a capillary barrier effect caused by the structure where finer weathered material overlies coarser fresh material this results in a well defined weathering front particularly beneath a slope where water flux is parallel to the front whereas the front is transitional beneath a ridge top where the front is nearly horizontal and the water flux is normal to the front infiltrating water from rain increases the weight of weathered material and decreases the suction within the material which is the final trigger of a shallow landslide of non welded ignimbrite long term weathering which proceeds on the order of years provides slide material

the influence of parent material on topsoil geochemistry in eastern england the topsoil of around 10 000 km2 in eastern england has recently been sampled intensely at 4609 sites to characterize its geochemistry the parent materials which include both solid geology and quaternary sediments range in age from permian to holocene the distributions of the concentrations of major and trace elements have been characterized geostatistically and the role of parent material on their spatial structure anisotropy and their spatial relationships coregionalization have been investigated analysis of variance with the sites grouped by major parent material type showed that this classi cation accounted for 14 to 48 per cent of the variance for the various elements global variograms of 13 elements al as ca cr cu fe mg mo ni p pb ti and u have been computed and modelled eleven of the variograms seem to comprise two structures both of which we modelled with spherical functions one of short range 3 5 to 9 km and the other with a range of 15 to 23 km the models included a nugget variance which varied from 27 per cent for as fe and mg to 63 per cent for p of the total the long range structures are related to the separations of the major parent materials the variograms of several elements showed appreciable anisotropy most notably that of mg anisotropy is evident at short ranges of less than 5 km this accords with the geological structure of the beds which dip from west to east so that their outcrops are elongated from north to south a linear model of coregionalization tted to the data emphasized several important geochemical associations which we interpret elements commonly associated with clay minerals mg al and the clay size fraction ti are dominated by the long range structure of the coregionalization whilst several trace elements as cr ni and u are spatially correlated with fe over short distances through adsorption of the former on the surfaces of fe oxyhydroxides the topsoil around large urban areas is enriched in lead but it is not clear whether anthropogenic sources are responsible for this metal s anomalous spatial relationships with other elements crown copyright 2003 reproduced with the permission of her majesty s stationery of ce published by john wiley sons ltd

a perched high elevation wetland complex in the atacama desert northern chile and its implications for past human settlement a previously undocumented type of wetland is described from the atacama desert in northern chile 3000 m above sea level sustained exclusively by direct precipitation and perched above the regional water table geomorphological mapping pedostratigraphy geochemistry and analysis of contemporary vegetation is used to understand wetland formation and dynamics during historical and present time periods the paleowetland deposits overlie a miocene tuff that acts as an impermeable barrier to water transfer and creates conditions for local shallow ground water these deposits include several paleosols that were formed during periods when precipitation increased regionally at 7755 7300 1270 545 and 400 300 cal yr bp the similarity in timing with other palaeohydrological records for the atacama implies that paleosols from this wetland are proxies for reconstructing past changes in local and regional hydrological cycle archaeological investigations have revealed the presence of two small farms from the late intermediate period i e during the earliest wetter phase represented by the paleosols both farms are located near the paleowetland deposits which suggests that local inhabitants exploited these water sources during late pre hispanic times results of this study improve knowledge of settlement patterns during this and earlier cultural periods

a general analytical solution for the evolution of cliffs accounting for strength degradation seismic action formation of tension cracks and seepage abstract the evolution of natural slopes over time is ruled by several concurrent physical phenomena namely the strength of its component geomaterials and their weakening over time due to weathering processes the occurrence of seismic events seepage and the formation of tension cracks the paper presents analytical solutions obtained considering a succession of discrete failure events landslides progressively altering the slope morphology over time the model derived in the framework of limit analysis assuming plane strain conditions provides a tool for the assessment of whether manufacts and or infrastructures located on a slope subject to various natural degradation phenomena will be affected by the occurrence of failures unlike current empirical and semi empirical models of slope evolution the analytical solution that is here presented is derived by applying principles of soil and rock mechanics therefore it is of general validity so that no ad hoc calibration against past observations of the evolving slope is needed this analytical technique only requires knowledge of the geotechnical parameters characterising the geomaterials comprising the slope of interest namely angle of shearing resistance cohesion c tensile strength unit weight together with knowledge of the relevant seepage scenarios strength degradation processes and seismic events likely to occur results show that that earthquake loading and seepage can substantially decrease slope stability increase the volume of material sliding away during each landslide event and alter the evolution of the slope over time while tensile strength exhibits a less strong influence especially as strength degradation progresses dimensionless ready to use charts are provided for the benefit of practitioners

delineation of temporal variability and governing factors influencing the spatial variability of shallow groundwater chemistry in a tropical sedimentary island summary an attempt has been made to delineate the temporal variability and factors governing the shallow groundwater chemistry using analysis of variance anova and multivariate analysis notably r mode factor fa and hierarchical cluster analysis hca subsequently geostatistical isoplethic maps were applied to convey better understanding on the distribution of selected groundwater parameters the manukan island s shallow aquifer with sedimentary setting that constantly abstracted for freshwater supply has been selected for this study one way anova suggested that neither changes of tide level nor rainfall volume appeared to exert significant influence on the groundwater chemistry of the small island rather the groundwater chemistry was greatly governed by influence from seawater intrusion which characterized by considerable amount of ca na and cl such condition was well explained by a piper diagram where most plots were situated at the middle diamond shaped diagram indicating mixing condition fa likewise revealed that the shallow groundwater receives marked influence from carbonate dissolution and silicate weathering processes especially boreholes located in the inland area this can be clearly noted from the distinct groupings of relationships among different factors hca classified boreholes into three groups according to their locations in the coastal area suggesting significant chemical variations between boreholes with distance from coast such distribution pattern was particularly evident in the isoplethic map overall it appears that the shallow groundwater in the tropical island is not an appropriate source for drinking water in concern to its exceptionally high salinity and several elevated minor elements mn pb and se for this it is suggested that efforts in exploring other alternative sources should be performed outright

modeling the evolution of natural cliffs subject to weathering 1 limit analysis approach 1 retrogressive landsliding evolution of natural slopes subjected to weathering has been modeled by assuming mohr coulomb material behavior and by using an analytical method the case of weathering limited slope conditions with complete erosion of the accumulated debris has been modeled the limit analysis upper bound method is used to study slope instability induced by a homogeneous decrease of material strength in space and time the only assumption required in the model concerns the degree of weathering within the slope and for this we assumed and tested different weathering laws by means of this method the evolution of cliffs subject to strong weathering conditions weathering limited conditions was predicted the discrete succession of failures taking place was modeled taking into account the geometry assumed by slopes as a consequence of previous mass movements the results have been compared with published data from long term slope monitoring and show a good match between experimental observations and analytical predictions the retrogressive evolution of the slope occurs with decreasing size of the unstable blocks following a logarithmic volume frequency relationship a nonlinear relationship is found between mass flux and average slope gradient a set of normalized solutions is presented both by nomograms and tables for different values of slope angle cohesion and internal friction angle

looking back at the centralia coal fire a synopsis of its present status abstract centralia is in the anthracite region of eastern pennsylvania the town is part of the western middle field a large synclinorium in columbia and schuylkill counties residents of centralia set fire to a garbage dump in 1962 and in the process ignited the buck mountain coal bed fractured and moderately dipping strata at the site permitted air to circulate into the subsurface thereby promoting combustion and making it difficult to extinguish the centralia fire as the fire advanced during the 1960s 1970s and early 1980s it did so along four fronts however the fire appears to be advancing on only two fronts today the pennsylvania department of environmental protection is currently monitoring the fire fire associated with the first or cemetery front is advancing approximately 20 m year although attempts were made to fight the fire they were unsuccessful for logistical and monetary reasons most residents of centralia relocated with the assistance of funds approved by the u s congress and disbursed by the state of pennsylvania the inexperience of community leaders in working with state bureaucracy contributed to the difficulties of fighting the fire

weathering distribution in a steep slope of soft pyroclastic rocks as an indicator of slope instability abstract weathering of rocks on steep slopes influences slope instability and sometimes leads to slope failure during heavy rainfall to determine the weathering intensity of hillslope rocks and its inward change from the slope surface measurements of the penetrative hardness of rocks which correlates with their strength were made in some slopes composed of soft pyroclastic rocks on kyushu island japan a gradual reduction in hardness from the interior to the slope surface was recognized within slopes the hardness change was almost concordant with changes in other weathering indices such as rock color clay minerals and apparent grain size the weathered zone indicated by the reduction in hardness was 1 2 m thick at the foot of steep slopes which are frequently subjected to gullying and surface failures whereas the zone was 7 8 m thick at slope summits which are gentle and stable for a long period although the inward change in hardness was gradual on all parts of a slope the change was marked on the foot slope where the strength contrast between weathered and non weathered rock was greater the thickness of the weathered zone on the foot slope therefore controls the volume of failed materials when a failure occurs the difference in weathered thickness between the foot and the summit of a slope much affects the style of failure in general and consequently shapes the characteristic configuration of slopes in this region the estimated weathering rate on a slope surface based on hardness distribution was on the order of 10 2 to 100 cm year 1 assuming a constant rate this rate is far greater than that of other rocks therefore the frequent occurrence of slope failures in this region was attributed to this rapid weathering

concentrations variations and distribution of molybdenum mo in catchment outlet sediments of china conclusions from the china geochemical baselines project abstract the concentrations variations and distribution of molybdenum mo in catchment outlet sediments from china were studied in this contribution based on the results of recently finished continental scale china geochemical baselines cgb project the data from cgb were combined with other published data sets with the purpose of understanding the spatial distribution of mo in china and in addition relating the observed geochemical features to natural and or anthropogenic processes this geochemical mapping with a density of ca 3000 km2 per site involves catchment sediments in two horizons at each site a top sample tos at a depth of 0 25 cm and a bottom sample bos at a depth greater than 100 cm in total 3382 tos and 3380 bos samples were collected the analytical results show that the concentrations of mo in the catchment outlet sediments of china range from 0 07 to 57 86 g g for the tos and 0 09 32 43 g g for the bos the median and mean values of the tos data are 0 73 and 1 01 g g respectively and those of the bos data are 0 71 and 0 94 g g the variations of both the tos and bos are high at this continental scale the mo concentrations vary greatly from one geological and or geographic unit to another for instance from the cathaysia block with the tos and bos median values of 1 22 and 1 46 g g to the north china craton with those of approximately 0 61 and 0 58 g g various processes govern the spatial distribution of mo in the catchment sediments of china but regional scale natural sources e g lithologies predominate sedimentary sandstones and carbonate rocks alluvium in plain terrain and aeolian materials e g loess account for the extensive low concentrations 1 2 g g in the yangtze and cathaysia blocks simultaneously some local mineralized areas can be also identified at this scale because the sampled sites just happened to fall on sediments derived from mineralized rocks or anthropogenic addition by mining activities furthermore the tos share the similar patterns with the bos indicating relatively stable inheritance and no apparent extensive secondary enrichment or depletion in the catchment sediments of china the cgb demonstrates that a series of baseline levels of mo are needed at different regions and scales and ultra low density mapping can still deliver robust geochemical patterns

summary of exploration geochemical and mineralogical studies at the giant pebble porphyry cu au mo deposit alaska implications for exploration under cover exploration geochemical and mineralogical studies by the u s geological survey at the pebble porphyry cu au mo deposit were designed to 1 determine whether the concealed deposit can be detected with surface samples 2 better understand the processes of metal migration from the deposit to the surface and 3 test existing methods for assessing concealed mineral resources and or develop new ones surface water ponds streams and springs pond and stream sediment soils subjected to various leaching techniques and glacial till samples were collected the tilted nature of the undisturbed orebody varying depth of cover and later glacial processes strongly influence the geochemical responses and processes active on the various sample media the multimedia approach aids in identifying possible processes that caused the significant geochemical variations within and among the various media these processes include the following 1 in the pebble west zone thin cover and local exposure of the orebody have facilitated the oxidation of pyrite and other sulfides and associated ferrous ferric iron reactions resulting in the local natural acidification of ponds observed in the west zone and in associated metal anomalies in waters sediments and soils 2 in contrast the east zone is concealed by both glacial deposits and underlying thick cover rocks which precludes the oxidation of sulfides in the underlying orebody low level geochemical anomalies in circumneutral spring and pond waters from the east zone are discernible only by using high resolution inductively coupled plasma mass spectrometry with lower limits of determination two and perhaps three orders of magnitude lower than traditional methods a variety of partial leaches of soils over the east zone reveal geochemical anomalies in a similar suite of elements that may be related to upwelling waters from depth along graben bounding faults 3 the indicator minerals gold jarosite and andradite in till reveal a displaced mineralogical anomaly to the west and south of the pebble orebody as ore related minerals were scraped from the orebody and deposited in till downice of the deposit geochemical anomalies in pond water and sediment over the displaced till are attributed to the ore related minerals in till this orientation study demonstrates the strong control of local geologic and geochemical settings on the effectiveness of different traditional and newer reconnaissance geochemical exploration techniques and thus has important implications for exploration

recognition of an enhanced multi element geochemical signature of porphyry copper deposits for vectoring into mineralized zones and delimiting exploration targets in jiroft area se iran abstract delimiting exploration targets using geochemical exploration data can be a challenging issue when different geochemical signatures represent the same deposit type sought in this regard fuzzy operators have been used to integrate different geochemical evidence layers into a single model for generating target areas in this paper a gis based expected value function was adapted to integrate different geochemical evidence layers into a stronger geochemical signature for delimiting exploration targets then the expected value function and fuzzy operators were compared the comparison demonstrated that the former is more efficient than the later for generating a stronger geochemical evidence layer the higher efficiency of the expected value function is because it simultaneously uses the value of all input variables and their relative importance in the process of integration the proposed approach was evaluated by using a lithogeochemical data set for prospecting porphyry cu deposits in jiroft area kerman province southeast of iran as a case study

a new technique for non destructive field measurement of rock surface strength an application of the equotip hardness tester to weathering studies tafone like depressions have developed on the aoshima sandstone blocks used for a masonry bridge pier in the coastal spray zone a thin layer of partial granular disintegration was found on the surface in depressions to evaluate quantitatively the strength of the thin weathered layer the hardness was measured at the surface of the sandstone blocks using both an equotip hardness tester and an l type schmidt hammer comparison of the two testing results indicates that the equotip hardness value is more sensitive in evaluating the strength of a thin layer of weathered surface rock than the schmidt hardness value by applying two methods i e both the repeated impact method and the single impact method the equotip tester can evaluate the strengths of fresh internal and weathered surficial portions of rocks having a thin weathering layer comparison of the two strengths enables evaluation of strength reduction due to weathering copyright 2007 john wiley sons ltd

geologic factors contributing to landslide generation in a pyroclastic area august 1998 nishigo village japan vertical contrasts in permeability particularly where permeable surface materials overlie impermeable materials that prohibit the downward infiltration of groundwater concentrate the groundwater and become an important focus of landslides that are triggered by intense rainfall just such a hydrogeological structure is present within the pyroclastics in nishigo village in fukushima prefecture japan where intense rainfall of 1200 mm in 6 days generated more than 1000 landslides in august 1998 three types of landslides occurred the first type occurred along the edges of small plateaus where horizontal beds of permeable ash scoria and pumice overlie impermeable mudflow deposits consisting of tuffaceous fines and andesite blocks and massive weakly consolidated ignimbrites the rainfall on the plateaus infiltrated downward first then laterally within the permeable beds finally gushing out at the plateau edges and triggering landslides the second type of landslide occurred where weathered tuff of the same ignimbrite was present with a slip surface at the base of the heavily weathered zone within this heavily weathered zone the tuff exfoliated into thin weak plates running parallel to the slope surface the third type of landslide involved failure of colluvium or ash that filled hollows this type occurred as a result of subsurface erosion caused by the groundwater infiltrating the superficial beds above the impermeable tuff

tropical chemical weathering of hillslope deposits and bedrock source in the aburra valley northern colombian andes abstract tropical chemical weathering produces extensive lateritization and formation of deep weathering profiles both processes are fundamental to landscape evolution and slope instability the aburra valley of the northern colombian andes is characterized by tropical conditions the valley slopes are mostly covered by hillslope deposits originating from four basement rock suites which comprise contrasting granitoid volcanic sedimentary ophiolitic and metamorphic sources respectively tropical chemical weathering of the aburra hillslope deposits and their respective bedrock were examined using x ray fluorescence and x ray diffraction analysis to document and quantify their chemical weathering profiles compositions and mineralogical properties the chemical index of alteration cia loss on ignition loi and the mobiles index imob were used to quantify the degree of weathering of hillslope deposits and bedrock source weathering trends were analyzed using a cn k and a cnk fm diagrams the material mantling the slopes in the aburra valley records an intense weathering history chemical weathering is characterized by increased development of clay minerals kaolinite halloysite and iron and aluminum sesquioxides lateritization characterizes the final stage of the weathering profiles concentrations of cao na2o k2o decrease markedly in the weathering products compared to the fresh bedrock source whereas concentrations of al2o3 fe2o3 and mgo increase significantly cia ratios of matrix slope deposits derived from all four sources near 100 whereas those of boulder slope deposits and saprolites are lower but exceed source rock values different a cn k weathering paths are evident for each lithotype validating the correlation established between the hillslope deposits and their various parents chemical weathering indices in some samples are strongly influenced by the presence of sesquioxides as reflected by high loi anomalously low cia and varying enrichment trends on the a cnk fm diagrams consequently different chemical indices based on different criteria need to be combined to obtain best results as illustrated here by the combination of loi cia and imob the overall results suggest that tropical conditions have dominated for a long time in the northern colombian andes leading to uniformly high weathering indices in matrix slope deposits irrespective of parent lithotype prolonged warm and humid conditions could thus be responsible for the weathering and remobilization of extensive old hillslope deposits during the quaternary however in addition to the influence of climatic factors tectonism has also undoubtedly influenced slope evolution in the aburra valley

process recognition in multi element soil and stream sediment geochemical data abstract stream sediment and soil geochemical data from the upper and lower coastal plains of south carolina usa were studied to determine relationships between soils and stream sediments from multi element associations characteristic compositions were determined for both media primary associations of elements reflect mineralogy including heavy minerals carbonates and clays and the effects of groundwater the effects of groundwater on element concentrations are more evident in soils than stream sediments a winnowing index was created using ratios of th to al that revealed differing erosional and depositional environments both soils and stream sediments from the upper and lower coastal plains show derivation from similar materials and subsequent similar multi element relationships but have some distinct differences in the lower coastal plain soils have high values of elements concentrated in heavy minerals ce y th that grade into high values of elements concentrated into finer grain size lower density materials primarily comprised of carbonates and feldspar minerals mg ca na k al these gradational trends in mineralogy and geochemistry are inferred to reflect reworking of materials during marine transgressions and regressions upper coastal plain stream sediment geochemistry shows a higher winnowing index relative to soil geochemistry a comparison of the 4 media upper coastal plain soils and stream sediments and lower coastal plain soils and stream sediments shows that upper coastal plain stream sediments have a higher winnowing index and a higher concentration of elements contained within heavy minerals whereas lower coastal plain stream sediments show a strong correlation between elements typically contained within clays it is not possible to calculate a functional relationship between stream sediment soil compositions for all elements due to the complex history of weathering deposition reworking and re deposition however depending on the spatial separation of the stream sediment and soil samples some elements are more highly correlated than others

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

soil slips on weathering limited slopes underlain by coarse grained granite or fine grained gneiss near seoul republic of korea abstract the chemical mineral physical and mechanical properties of two soil layers on soil slip scars in slopes underlain by coarse grained granite and fine grained granitic gneiss near seoul republic of korea were examined our aim is to study the effect of the mineral grain size of the bedrock on the soil layer structure and the return period of shallow soil slips because of the coarser slope materials in granite resulting from weathering the permeability is larger and the weathering front has a copious water supply also because of the smaller specific surface area of the minerals restricted leaching produces grus from the bedrock so that the rate of formation of soil and in particular the slip plane due to chemical weathering is faster since on granite slopes the leaching proceeds toward the surface the sliding plane is deeper with coarser soft grus resulting in the existence of a minimum c value in the soil layer on gneiss slopes by contrast leaching cannot proceed with decreasing soil depth and the sliding plane is deeper with finer soft grus just above hard grus and has similar c and values as the upper soft grus because the grain size of both soils is the same in the granite soil layers the sliding plane corresponds to the minimum shearing resistance whereas in the gneiss soil layers the shearing resistance increases gradually with soil depth and the sliding plane is formed when the weathering front is located deeper because of the faster soil formation rate and the shallower slip depth in granite slopes the return period of occurrence of soil slips should be shorter in granite slopes than in gneiss slopes

landscape geochemistry retrospect and prospect 1990 at present the terms environmental geochemistry and applied geochemistry are poorly defined in english in fact they usually mean just what a particular geochemist or geochemist s wishes them to mean there is a less common term landscape geochemistry which describes a holistic scientific discipline aimed at the geochemistry of the environment although little known outside the u s s r the basics of landscape geochemistry were first described more than 60 a ago since then landscape geochemistry has had a history pertinent to all scientists who participate in environmental geochemistry today this review traces the evolution of landscape geochemistry and related disciplines over the past 90 a and shows how they all relate to the development of modern environmental geochemistry worldwide in landscape geochemistry the term landscape refers to both the horizontal stratification of land e g into terrestial bog and aquatic ecosystems which co exist in an area of country and to the vertical stratification within these units e g into vegetation soils etc in these respects landscape geochemistry resembles landscape ecology which is currently a discipline of growing importance in environmental science landscape geochemistry differs from landscape ecology because it focuses attention on all aspects of the behaviour of chemical entities e g isotopes elements and ions in both living and dead matter in landscapes of all kinds from the viewpoint of general geochemistry landscape geochemistry focusess on the interaction of the lithosphere with the hydrosphere atmosphere and biosphere this holistic approach provides a common theoretical background for both pure and applied environmental geochemistry worldwide an important aspect of landscape geochemistry particularly pertinent to environmental geochemistry in the non soviet world today is that the subject provides a link between modern exploration geochemistry and modern environmental science including geochemistry historically landscape geochemistry stems from the russian school of landscape science this developed from the ideas of v v dokuchaev 1846 1903 around the turn of the century concepts unique to landscape geochemistry were first described in the 1920s by one of dokuchaev s students b b polynov 1867 1952 a i perel man 1909 a student of polynov began to teach landscape geochemistry at moscow university in 1952 since then the subject has become firmly established as the focus for fundamental and applied environmental geochemistry in the u s s r this review traces the development of landscape geochemistry from its origins around 1920 until 1990 the volume of literature pertinent to the review is voluminous for this reason attention is usually focused on the basic concepts and principles of landscape geochemistry and related scientific disciplines readers who require more detailed information on subjects covered in this review should consult the references cited the review is organized in four parts the first three trace the historical development of landscape geochemistry and related disciplines in three time periods these are 1 pre 1950 2 between 1950 and 1980 and 3 1980 1990 part 4 uses paradigms to summarize the historical evolution of landscape geochemistry and indicates how a global landscape geochemistry might develop in the future