delineating alteration footprints from field and aster swir spectra geochemistry and gamma ray spectrometry above regolith covered base metal deposits an example from abra western australia

detectability of minerals on desert alluvial fans using reflectance spectra we analyzed the visible and near infrared reflectance spectra of soil samples collected from desert alluvial and colluvial surfaces in the cuprite mining district nevada these surfaces are downslope from hydrothermally altered volcanic rocks that contain spectrally characteristic minerals such as alunite and kaolinite coarse fractions of the soils on the alluvial fans are mineralogically variable and express the upslope lithologies fine fractions are remarkably similar mineralogically and spectrally in all samples because of dilution of local mineral components by regionally derived windblown dust theoretical models for spectral mixing and for particle size effects were used to model the observed spectral variations diagnostic mineral absorption bands in the spectra of fan materials were enhanced by computationally removing the spectrum of the homogenous fine soil component detection limits for minerals were found to be controlled by the sensitivity of the instrument the spectral contrast between the mineral and the background and the relative brightnesses of the mineral and the background these results show that spectral mixing models are useful for analyzing data with high spectral resolution obtained by field and aircraft spectrometers

application of the crosta technique for porphyry copper alteration mapping using etm data in the southern part of the iranian volcanic sedimentary belt abstract many of the known porphyry copper deposits in iran are situated in the central iranian volcanic belt the area under study is located in the southern part of this belt and covers an area of about 6600 km2 the climate in the area is semi arid given the poor soil development and poor vegetation cover but abundant outcrops the arid semi arid part of the belt is most suitable for remote sensing study enhanced thematic mapper plus etm images have been used for alteration mapping crosta method was found useful for enhancing the areas in which the regolith contains a high proportion of hydroxyl and iron oxide minerals the crosta method has been used on selected 4 and 6 bands areas with iron oxide and hydroxyl minerals have been enhanced by using six bands of etm data

assessing the utility of visible to shortwave infrared reflectance spectroscopy for analysis of soil weathering intensity and paleoclimate reconstruction abstract visible to shortwave infrared reflectance vswir spectroscopy is a fast and efficient approach for estimation of soil properties in order to test whether soil weathering intensity can be predicted using reflectance spectra in the vswir range 350 2500 nm and to examine the efficacy of this methodology to supplement or substitute for traditional mineralogical and geochemical techniques of paleoclimate reconstruction we investigated a quaternary soil sequence at shengli in the sichuan basin of southwestern china vswir absorption bands can be characterized by geometrical parameters including position p depth d width w asymmetry as and full width at half maximum f our results indicate that spectral features in the visible to near infrared vnir 350 1000 nm range can be interpreted in terms of the presence and or concentration of individual fe oxide phases spectrally detected water is mostly bound in clay minerals and this single dominant water source facilitates interpretation of shortwave infrared swir 1000 2500 nm parameters soil spectral parameters were compared with the fe oxide mineralogy major element composition and clay mineralogy of soil samples obtained from conventional laboratory analyses strong correlations are found between vnir parameters and fe oxide mineralogy with d 900 serving as the best proxy for total ferric iron concentration p 900 and d 700 d 500 exhibit similar variation trends and relationships to the hematite hematite goethite h h g ratio of soil samples confirming their value as monsoonal weathering intensity proxies lower values of p 900 and d 700 d 500 indicate warmer and seasonally drier pedoenvironments reflecting a stronger east asian summer monsoon the utility of some swir parameters for assessment of weathering intensity declines in inhomogeneous soils e g those having vermiform structure thus spectral evaluation of weathering intensity is most effective in soils that are relatively homogeneous for which weathering degree is highly correlated to as 2200 d 2200 d 1900 and as 1400 the utility of these spectral proxies depends mainly on the mineral composition of soils and the application type i e laboratory versus field studies the application of vswir in the field e g imaging spectroscopy or is shows promise for rapid in situ mapping of weathering intensity thus providing a convenient approach to paleoclimate reconstruction in remote and inaccessible regions

regional analysis of tertiary volcanic calderas western u s using landsat thematic mapper imagery abstract the basin and range province of southern nevada is an excellent setting to study landsat imagery over volcanic rock assemblages the area is semiarid sparsely vegetated and contains relatively youtful 6 14 ma volcanic calderas with compositionally diverse volcanic rock assemblages investigation of rock spectra whole rock geochemistry desert varnish and landsat imagery indicates that the longer wavelength visible and near infrared thematic mapper tm bands 3 5 and 7 provide more effective lithologic discimination than the shorter wavelength bands due partly to deeper penetration of lower frequency energy and greater primary rock compositional response spectral contamination of vegetation degrades lithologic information in tm band 4 thus ratios color composites and intensity saturation hue images using tm bands 3 5 and 7 generally lead to superior lithologic contrast shorter wavelength tm bands 1 and 2 are affected more by surficial weathering products including desert varnish which may or may not provide an indirect link to lithologic identity these relationships lead to a rock varnish albedo difference that aids identification of desert varnish on leucocratic rocks using tm band 2 5 and 5 2 ratio images principles component color composites provide best overall lithologic contrast but not specific lithologic identification pc2 tends to contain lithologically dominant variance and combines favorably with other images influenced strongly by lithology late magmatic differentiates that are evolved with respect to alkalies and the incompatible elements exhibit steep spectral curves throughout the tm bands 5 7 interval leading generally to low 5 7 ratios and dark contrast on 5 7 ratio images guidelines for lithologic analysis of volcanic terrain using landsat tm imagery are outlined

origins of marslike spectral and magnetic properties of a hawaiian palagonitic soil a palagonitic soil hwmk1 from mauna kea hawaii has marslike spectral and magnetic properties reflectivity spectra of 20 m size separates resemble spectra for martian bright regions and reflectivity spectra of coarser size separates have some spectral characteristics in common with spectra for martian dark regions the bulk soil is magnetic with a saturation magnetization of 0 98 a m2 kg of sample 10 a m2 kg of fe at 296 k petrographic observations show that the soil contains separate populations of black and orange tephra particles which are relatively unaltered fragments of tachylite merocrystalline basalt and extensively weathered palagonitized fragments of sideromelane clear brown basalt glass respectively although both types of particles contain plagioclase and olivine microphenocrysts their iron oxide mineralogies are substantially different as documented by mossbauer and static magnetic measurements a strongly magnetic opaque iron oxide titanomagnetite is associated with black particles and is responsible for the magnetic nature of the soil a relatively weakly magnetic superparamagnetic ferric oxide and minor hematite are associated with orange particles and are responsible for the color the more highly weathered state higher state of oxidation of orange particles is a consequence of the faster weathering palagonitization rate for their sideromelane precursors than for tachylite increasing state of oxidation decreasing saturation magnetization and increasing near ir reflectivity with decreasing particle diameter of bulk soil are manifestations of the increasing proportions of palagonitic material as particle diameter decreases

sub pixel mapping of alunite and jarosite using aster data a case study from north of semnan north central iran abstract a widespread series of volcanic rocks and younger intrusive bodies are exposed in the north and northeastern semnan north central iran they show an intermediate to felsic composition which have undergone various types of alteration including alunite and jarosite in this research aster data were used for sub pixel mapping of these typical minerals using the mixtured tuned matched filtering mtmf algorithm the spectral properties of field samples were measured by an asd spectroradiometer and their spectra were analyzed through a visual comparison to the usgs spectral library however the z profile method was used for extraction of target spectra from pixels in which the occurrence of desired minerals were verified by other methods the mtmf output results revealed pixels with the highest fractions of alunite and jarosite dominantly near the altered rhyolitic and andesitic tuffs as well as in adamelites it is suggested that an integration of mtmf method and the aster data is a powerful approach for sub pixel mapping of alunite and jarosite which could be applicable in mineral exploration projects

stress field in the ryukyu kyushu wadati benioff zone by inversion of earthquake focal mechanisms abstract the study addresses the space distribution of the stress field in the kyushu ryukyu wadati benioff zone based on homogeneous data of earthquake focal mechanisms and the inverse technique by gephart and forsyth j geophys res 89 1984 9305 the used data set consists of 148 harvard cmt solutions and 22 earthquake focal mechanisms listed in previous studies the stress field parameters are determined for 0 40 41 100 and h 100 km depth ranges the top 100 km layer of the wadati benioff zone wbz is characterized by strike normal maximum compression 1 and steeper than the slab minimum compression 3 the last indicating for unbalanced slab pull force the tokara channel divides the subduction into two parts of different stress regime at depth greater than 100 km to the south of the channel the slab is under slab parallel 1 and slab normal 3 while its northern part beneath kyushu is under slab parallel extension and slab normal compression the results of recent studies on the regional velocity structure and geochemistry of the volcanic lava indicate that the most plausible reason for the observed stress field difference below 100 km in the northern and rest part of the arc is the presence of hot low viscosity upper mantle west of kyushu the results of this study indicate that the forces involved in the contemporary subduction dynamics in the ryukyu kyushu wadati benioff zone are related to the convergence between the philippine sea plate and the eurasian plate the trench suction force slab pull the slab anchor force and in the southern central part of the arc mantle resistance

mineralogy and geochemistry of alteration induced by hydrocarbon seepage in an evaporite formation a case study from the zagros fold belt sw iran abstract leaking hydrocarbon and associated fluids produce a reduced environment which initiates diagenetic reactions in the rocks and soils overlying hydrocarbon reservoirs this article introduces mineralogical and geochemical alterations induced by hydrocarbon seepages in the gachsaran evaporite formation masjed soleiman zagros folded belt sw iran using various geochemical methods x ray diffraction xrd analysis revealed two dominant groups of mineralogical changes in the anomalous zone including 1 spotty occurrences of jarosite natroalunite and sulfur 2 simultaneous decrease of sulfate and increase of carbonate the 13c values of carbonate phases vary between 8 9 and 32 3 which support a partial contribution of hydrocarbon in these phases ph measurements of rock samples indicated that hydrocarbon seepage causes decrease of ph though not very significantly however ph in areas that show ongoing sour hydrocarbon seepage among rarely pure gypsum beds decrease to 0 09 which produces acid sulfate soil trace element concentrations indicated that cr co ni v cd u cu and zn increase in various patterns around the hydrocarbon seepages excepting the areas with very low ph

estimation of surface iron oxide abundance with suppression of grain size and topography effects abstract mineral forms of iron oxide such as hematite goethite and jarosite are important because they are widely distributed at the earth s surface and because they are used as indicators for mineral exploration iron oxide abundance in rocks containing these minerals can be estimated from the absorption depth at wavelengths of around 900 nm in a reflectance spectrum but this depth is also affected by extraneous factors such as grain size and topography this paper investigated the effect of grain size on reflectance spectra and proposed a method for estimating iron oxide abundance in surface rocks by using remotely sensed data with suppression of the effects of grain size and topography reflectance spectra were measured in a laboratory from rock powder samples of different grain sizes containing iron oxide minerals while the reflectance increased with decreasing grain size the presence of ferric iron caused the absorption depth to be almost constant at around 900 nm irrespective of the chemical composition of the sample in addition the difference between the reflectance at 550 nm and 760 nm slope was a function of grain size iron oxide abundance can be estimated accurately by mcr 900d which is the maximum absorption depth at the absorption center after the effect of grain size and topography was suppressed by slope and the continuum removal method which takes the ratio between the original spectrum and its continuum respectively correlation of mcr 900d results with datasets of actual spectral and chemical iron oxide laboratory measurements revealed that the mineral forms also need to be considered mcr 900d results were significantly correlated with rock samples classified as containing different forms of iron oxide minerals hematite goethite and jarosite finally mcr 900d was applied to an aviris dataset for the cuprite site in nevada usa the results represented the enrichment zones of iron oxide within hydrothermally altered areas

abundance and distribution of ultramafic microbreccia in moses rock dike quantitative application of mapping spectroscopy moses rock dike is a tertiary diatreme containing serpentinized ultramafic microbreccia sum located on the colorado plateau in utah field evidence indicates that sum was emplaced first followed by breccias derived from the permian strata exposed in the walls of the diatreme and finally by complex breccias containing basement and mantle derived rocks sum is primarily found dispersed throughout the matrix of the diatreme we examined the nature of sum abundance and spatial distribution using data collected remotely by the airborne imaging spectometer ais the minerals serpentine gypsum and illite as well as desert varnish and the lithologies sum and various sandstones were identified from the ais data six end members sum two types of sandstone gypsiferous soil clay rich soil desert varnish were chosen to represent the dominant lithologies of the surface in moses rock dike region spectra of these end members were used in an intimate mixing model to deconvolve the ais spectral data into surface abundance coefficients for each component using a nonnegative least squares inverse algorithm the results of this calculation of surface composition are consistent with field observations and investigations sum distribution and abundance in the matrix of the diatreme were examined in detail and two distinct styles of sum dispersion were observed one style is characterized by high to moderate sum abundance surrounded by halos of lesser sum abundance the dispersion halos grade steeply into regions of the matrix with little to no sum the second style is characterized by moderate sum abundances and broad dispersion halos with sum distributed across the entire width of the diatreme these dispersion styles are consistent with emplacement of the dike as a fluidized solid volatile system where sum which is emplaced early becomes reincorporated into the turbulent flow of the diatreme by abrasion and comminution by paniculate matter carried along in the eruption this eroded material is then dispersed throughout the matrix by eddy diffusion the first style represents an early arrested phase of the eruption sequence while the second style represents a more mature phase distributions of the second style probably indicate the location of channels where flow was concentrated during later stages of eruption since both styles are observed at the same level of erosion this indicates that the duration of eruption varied along strike at moses rock dike

empirical methods to estimate the strength of jointed rock masses abstract the ultimate strength and deformation of jointed rock mass are important parameters that designers look for in selecting sites for foundations of civil and mining engineering structures in rocks in the field it is extremely difficult to stress a rock mass to its ultimate failure stress consequently the field tests are performed up to a certain predefined stress level it is shown in this study that the results of these tests can be used to arrive at the ultimate strength of the rock mass a large number of uniaxial compressive strength ucs tests were conducted on the specimens of jointed block mass having various combinations of orientations and different levels of interlocking of joints four dominating modes of failure were observed the strength and the tangent elastic modulus values of the mass for a specific failure mode when plotted on the deere miller classification chart are found to follow an empirical straight line indicating strong correlation between them using the gradient of this empirical line correlations have thus been suggested to assess the ultimate strength of the jointed rock mass the findings of the study have been verified by applying it to estimate the ultimate rock mass strength of nine rock types from few dam sites in the lower himalayas the ultimate strength obtained by the present methodology is compared with that obtained through the q classification system it is concluded that reasonably good estimates on field strength of jointed rocks are possible by using the correlations suggested in this study

relative scale and the strength and deformability of rock masses abstract the strength and deformation of rocks depend strongly on the degree of fracturing which can be assessed in the field and related systematically to these properties appropriate mohr envelopes obtained from the rock mass rating rmr classification system and the hoek brown criterion for outcrops and other large scale exposures of fractured rocks show that rock mass cohesive strength tensile strength and unconfined compressive strength can be reduced by as much as a factor often relative to values for the unfractured material the rock mass deformation modulus is also reduced relative to young s modulus a cook book example illustrates the use of rmr in field applications the smaller values of rock mass strength and deformability imply that there is a particular scale of observation whose identification is critical to applying laboratory measurements and associated failure criteria to geologic structures

spectral and geochemical characterization of onshore hydrocarbon seep induced alteration in the dezful embayment southwest iran the presence of hydrocarbon seeps at the surface is indirect evidence of the presence of mature source rocks within a geological system at depth chemical changes in the environment of surface rocks caused by hydrocarbon seeps cause mineralogical alterations to determine the nature of the alterations and the influences of lithology and type of seep rock samples were collected from altered and unaltered evaporite and marly limestone formations in the dezful embayment southwest iran reflectance spectroscopy bulk rock wet chemical analyses and sulfur carbon and oxygen isotopic analyses were used to delineate surficial alterations and relate alterations to hydrocarbons seeping from underlying reservoirs in addition the boosted regression trees brt method was used to predict the presence of alterations from spectral indices comparisons of geochemical data and spectral data of altered evaporites and altered marly limestones showed that the minerals within alteration facies have distinctive spectral chemical and isotopic signatures gas induced alterations were characterized by the formation of gypsum and native sulfur and depletion in the released in natural gas reacted with gypsum in the evaporite sediments and calcite in the marly limestone formations which led to precipitation of secondary gypsum and native sulfur oil induced alterations were characterized by formation of secondary calcite and depletion in the oxidation of seeping oil and reactions between this oil and host rocks caused precipitation of secondary calcite within both formations the combination of fieldwork data and spectral geochemical data showed a connection exists between surficial alterations and underlying petroleum reservoirs which can be used in exploration campaigns

diagenesis in oxidising and locally reducing conditions an example from the triassic skagerrak formation denmark abstract diagenetic changes in red and white parts of the skagerrak formation triassic from onshore wells in denmark were analysed by scanning electron microscope electron microprobe and petrographic microscope in reflected and transmitted light the diagenetic sequences of the red and white parts of the skagerrak formation are in many ways the same early infiltration clays followed by precipitation of caliche calcite dolomite mixed layer illite smectite quartz feldspar kaolin minerals illite chlorite and anhydrite with increasing burial differences between the red and white parts of the skagerrak formation comprise oxidation stage in detrital minerals oxidation of glauconite in the red part and reduction of biotite in the white part the presence of eogenetic authigenic minerals pyrite and poikilotopic calcite in the white part hematite and red coatings in the red part the amount of mesogenetic authigenic kaolin minerals larger in the white part the chemistry of mesogenetic authigenic chlorite mg rich in the red part and fe rich in the white part and the preservation stage of detrital opaque minerals magnetite hematite chromite ilmenite show none or minor alteration in the red part whereas they have been almost completely altered in the white part as the differences between red and white areas are found both in early eogenetic and in mesogenetic authigenic minerals different oxidising conditions must have prevailed immediately after the deposition and continued into burial oxidising conditions were dominant in the arid triassic climate and the widespread red colour of the skagerrak formation was probably formed during early diagenesis due to precipitation of iron oxides or hydroxides locally reducing areas were formed probably by oxidation of organic material precipitation of oxidised iron minerals was thus prevented and the original white colour was preserved reducing conditions prevailed until the reducing agent was exhausted then an outer rim of the reduction spot might locally have been secondarily oxidised these changing redox conditions explain the occurrence of hematized authigenic pyrite and crandallite group minerals in red areas

discrimination of iron alteration minerals in visible and near infrared reflectance data field and laboratory studies were conducted to relate the mineralogy of rock and soil samples containing hematite fe2o3 goethite feooh and jarosite kfe3 so4 2 oh 6 to their reflectance properties in visible and near infrared wavelengths field reflectance measurements of regolith containing one or more of these minerals were made in the goldfield nevada mining district with a four channel radiometer the mineralogy and reflectance properties of regolith samples collected from these field measurement sites were then determined by laboratory studies mossbauer spectroscopy was used to identify the iron minerals present and their relative proportions the reflectance spectra of samples containing hematite and goethite were characterized by a reflectance minimum near 900 nm the location of this minimum could be accounted for by the relative proportions of hematite and goethite present in the samples under certain conditions it may be feasible to estimate the relative proportions of hematite and goethite on the earth s surface by determining the location of this near infrared reflectance minimum in high spectral resolution remote sensing data in addition the field measurements suggest that the ratio of band passes at 852 and 982 nm may be used to distinguish qualitatively among hematite goethite and jarosite thus maps of the distribution of these minerals may be derived from scanner images acquired in those band passes

a geo engineering classification for rocks and rock masses abstract in this article an attempt is made to assess the reliability of predicting the uniaxial compressive strength and the corresponding modulus of a rock mass by current approaches these two basic engineering properties when estimated from rock mass rating rmr q and geological strength index gsi indicate hardly any change in the modulus ratio with the change in the quality of the rock mass from very good to very poor however the modulus ratio obtained from the relations involving the joint factor j f indicate a definite decrease in the modulus ratio with a decrease in the quality of the rock mass the strength and modulus in the unconfined and confined states the modulus ratio and failure strain in the unconfined case were linked to j f in earlier publications based on a large experimental database some of these relations were adopted to verify the response of jointed test specimens the response of the rock mass during excavations for mining and civil underground chambers in establishing ground reaction curves including the extent of the broken zone and the bearing capacity of shallow foundations the joint factor is now linked to rmr q and gsi the prediction of compressive strength and modulus of the rock mass appears to be more suitable for classifying the rock based on these properties the deere and miller engineering classification applicable to intact rocks has been suitably modified and adopted the results of different modes of failure of jointed specimens establish definite trends of changes in the modulus ratio originating from the intact rock value on the modified deere and miller plot a geo engineering classification is evolved by considering strength modulus quantifiable weathering index and lithological aspects of the rock

characterization of microseepage induced diagenetic changes in the upper red formation qom region iran part ii a new insight using reflectance spectroscopic analysis abstract the classic microseepage model supports the notion that hydrocarbon pools leak to the surface over time and trigger an array of diagenetic physicochemical and mineralogical changes in the overlying sediments mapping the induced alteration mineralogy for microseepage targeting has been an appealing yet ambiguous practice mostly because of our incomplete understanding of the diversity of changes occurring in the environment to close this gap an integrated spectroscopic approach is adopted here to investigate the variability quantity and physicochemistry of diagenetic minerals induced by active microseepage systems over the alborz oil reservoir in the qom region iran the area includes an effectively sealed carbonate reservoir overlain by thick oligocene sediments of the upper red formation a large suite of samples collected from microseepage affected zones was spectrally characterized in the 350 2500 nm wavelength region and then statistically contrasted against unaffected samples gathered from a nearby control area the analysis reveals a novel array of mineralogic indicators for microseepage systems it indicates that smectites montmorillonite nontronite al rich mixed layer illite smectite fe rich chlorite and traces of palygorskite constitute the clay alterations this array is associated with the enrichment of k2o and loss of na2o and mgo from the system as indicated by x ray fluorescence measurements in the arid climate of the region the iron rich red beds fe2o3 6 are only moderately bleached and thus the subsequent chemical weathering of the relict irons has triggered goethite al poor and likely ferrihydrite and maghemite precipitation consequently besides the typical ferric iron bleaching the modification in the mineralogy of iron oxides oxyhydroxides marked by a shift in the absorption minimum at 900 nm is suggested as an additional indicator of microseepage systems fe chlorites constitute the dominant ferrous mineral present in the environment the affected strata are also associated with prevalent calcite and gypsum cements and occasionally jarosite occurrences based on the silica contents of the host rock the microseepage induced alterations are classified into two categories namely felsic and mafic wherein the latter is typified by the assemblages described here this study provides new insights into microseepage induced alterations and highlights the significance of reflectance spectroscopic techniques in facies determination and the alteration footprints mapping of onshore microseepage systems

a study on the uplift mechanism of tongjiezi dam using a coupled hydro mechanical model during filling in 1992 of the tongjiezi reservoir in southwest china it was noticed that the dam body and the rock masses on the right side of the valley were uplifted up to 22 2 mm and 24 3 mm respectively after reservoir filling in 1993 the uplift continued but the rate decreased and the measured maximum uplift increased from 22 2 mm to 27 5 mm in the dam body and from 24 3 mm to 28 9 mm in the rock masses from 1993 to 2004 based on the geological features of the dam site and observed geomechanics data a numerical method is used to evaluate the representative elementary volume rev and to identify the parameters related to the mechanical and hydraulic properties of the rock mass furthermore a coupled hydro mechanical model is presented to describe the uplift process the simulated results agree well with those measured in addition the time dependent deformation is studied in the laboratory and numerically it is concluded that with the specific hydrogeological conditions at the tongjiezi dam site hydro mechanical coupling during and after the reservoir impoundment is the main factor contributing to the uplift and the time dependent deformation is due to the rheological behavior of rock masses under seepage pressure

dark materials in valles marineris indications of the style of volcanism and magmatism on mars rifting on the equatorial canyon system of valles marineris provides a unique view of the interior of the martian crust to depths reaching 7 km exposing several in situ bedrock units which testify to past volcanic and magmatic processes on mars a thick regionally extensive deposit observed in coprates and juventae chasmata is interpreted on the basis of spectral reflectance erosional morphology and tendency for eolian mobilization to be composed of mafic glass possibly an ancient martian analogue of the lunar terra mantling deposits spectral mapping suggests that the dark floor covering materials in the lower canyons are derived from this unit a series of cliffs in the ophir chasma wall rock is interpreted to be exposures of resistant bedrock the spectral signature of this massive and uniform unit most closely resembles that of terrestrial mafic rocks altered to or coated by crystalline hematite application of computer mapping techniques to probable young volcanic materials in the central troughs yields an inferred distribution of volcanic activity consistent with the interpretation of extrusion along faults near the margins of the canyon floors this result supports the hypothesis that the valles originated through tectonic extension

investigations of the cerro colorado pluton northern chile using enhanced landsat thematic mapper images digitally enhanced landsat thematic mapper tm images of the cerro colorado pluton northern chile were studied the bulk of the intrusion is magnetic rich and laboratory spectra of the fresh surfaces of field samples are severely quenched weathering and oxidation of the magnetite has reduced the quenching effects allowing features due to the primary mineralogy of the rock to be resolved in the spectra of the weathered surfaces and consequently on the enhanced imagery in most cases the weathering alters the overall albedo of the rock and it may introduce additional features into the rock spectra due to iron hydroxides and clay minerals as yet it does not seem to the author that tm data alone could be used for lithological mapping some control is necessary in the form of fieldwork or pre existing maps

mineralogical characterization of rock surfaces formed by hydrothermal alteration and weathering application to remote sensing the value of 50 mu m was used as an approximate maximum penetration depth to include all mineral species which may contribute to a reflectance signal jarosite and alunite occur only in altered areas whereas hematite and goethite occur in both altered and unaltered areas incorporation of aluminum into hematite occurs only in unaltered areas the spectral shift to longer wavelengths which accompanies aluminum substitution should be useful in delineating mineralized zones modified journal abstract

mapping hydrocarbon induced mineralogical alteration in the northern tian shan using aster multispectral data seepage from hydrocarbon reservoirs can cause a number of chemical and or mineralogical changes in overlying rocks and soils these surface changes can be detected by remote sensing imaging systems the advanced spaceborne thermal emission and reflection radiometer aster is an advanced multispectral imaging system in the visible and near infrared vnir to shortwave infrared swir region band ratios of aster vnir and swir data to detect red bed bleaching and secondary carbonate formation induced by hydrocarbon seepage are proposed through analysis of the spectral properties of rock samples results show that aster band ratios of 2 1 and 4 8 can discriminate bleached red beds and secondary carbonate minerals due to hydrocarbon seepage in the northern tian shan they are in good agreement with mineral identification using x ray diffraction the ratio technique derived from aster data may provide a potential approach for hydrocarbon exploration in areas with sparse vegetation cover

comparison of geomagnetic planetary reference fields over italy abstract geomagnetic field measurements on a network at 106 repeat stations 1 3000 km2 and a second order network at 2550 stations 1 100 km2 were completed in 1981 total intensity and the horizontal and vertical component of the field were measured at all stations and in addition declination was measured at the first order stations normal fields for each element were computed from the first order network measurements using a second degree polynomial in latitude and longitude and comparisons were made for total intensity with 3 planetary reference fields the use of the polynomial normal normal field is suggested to draw anomaly maps

quantitative mineralogy from infrared spectroscopic data i validation of mineral abundance and composition scripts at the rocklea channel iron deposit in western australia visible near to shortwave infrared reflectance spectra vnir swir 400 2 500 nm wavelength region provide quantitative measurements of mineral abundances and mineral physicochemistries from drill core samples of channel iron ore the infrared spectral reflectance measurements of drill core samples from the rocklea channel iron deposit located in the hamersley basin of western australia were validated against x ray flouresence xrf and x ray diffraction xrd the reflectance data were collected using a csiro hy logging system from 180 reverse circulation and 14 diamond drill cores spanning a depth from surface to 55 m below surface intersecting the rocklea deposit the mineralogy of this channel iron deposit comprises chiefly goethite both vitreous and ochreous forms with lesser amounts of hematite and variable amounts of quartz kaolinite smectite both dioctahedral and trioctahedral varieties and carbonate both dolomite and calcite iron ore and waste rock mineralogy were extracted from the infrared spectroscopic reflectance data using the geometry depth wavelength of continuum removed reflectance spectra with depths of absorption features proportional to mineral abundance and wavelength positions proportional to chemical composition for any one mineral a number of its diagnostic spectral features are used to determine its mineral abundance and composition in order to avoid complications with minerals that spectrally overlap with part of the diagnostic spectral features of the mineral of interest this method that combines multiple spectral features to identify and quantify minerals is transferable to all types of infrared reflectance spectroscopic data collected from drill core to satellites final products include iron oxyhydr oxide content root mean square error rmse 9 1 wt fe al clay content rmse 3 9 wt al 2 o 3 hematite goethite ratio rmse 9 0 wt goethite vitreous versus ochreous goethite not easily measured using other analytical techniques clay mineral type kaolinite montmorillonite and nontronite and carbonate composition dolomite vs calcite the rocklea infrared reflectance spectroscopy based mineral abundance and composition results have been used in an associated study to characterize the architecture of the rocklea channel iron deposit with implications for exploration mining and ore genesis

relationship between rock physical properties and spectral mineralogy applied to exploration for an unconformity related uranium deposit saskatchewan canada infrared spectroscopy ir has been used to characterize clay and clay size minerals present in drill cores that are associated with unconformity related uranium deposits physical properties have

determining the size and shape of blocks from linear sampling for geotechnical rock mass classification and assessment classifying and assessing geotechnical aspects of rock masses involves combining parameters in various ways guided by empirical considerations to derive quantitative geotechnical parameters geological structures and the deformation history of rocks underpin the nature of rock masses the kinematics of a deforming rock mass may occur as sliding along throughgoing discontinuities or as distributed sliding on block faces distributed sliding will tend to disrupt the continuity of planar structures such that data on the size and shape of blocks is needed rather than relying on discontinuity orientation data alone orientation and spacing data can be combined to provide a geometric analysis of block systems from linear samples such as drill core dihedral angles and spacing of sequential pairs of discontinuities provides a sample of the size and shape of blocks that can be interpreted stereologically further detail can be derived by combining neighbouring intersections that enclose or partially enclose individual blocks the shape and size of a block can be represented on a stereograph with the enclosing faces shown as poles and their perpendicular distance from an arbitrary point inside the block shown as a number identifying the size and shape of specific blocks rather than relying on statistical methods is beneficial to critical aspects of design such as analysing keyblocks that would be exposed during excavations the detailed characterization of block size and shape is also a step toward interpreting the kinematics of rock mass deformation and the analysis of rock masses as ultra close packed dilatant granular systems

on relations between earthquake population and asperity population on a fault data were compiled on the trend of teleseismic short period t 1 4 s peak amplitude and spectral level vs m 0 for log m 0 26 slopes in log log scale of these trends were estimated as b 0 35 and 0 39 respectively for a similar trend of seismogram peak factor peak to rms amplitude ratio the slope estimate is p 0 13 0 39 disagrees with the 752 spectral model but can be explained by the multiasperity fault model of gusev 1989 if the typical asperity size 2r a is assumed to grow slowly with m 0

mineralogy composition and alteration of mars pathfinder rocks and soils evidence from multispectral elemental and magnetic data on terrestrial analogue snc meteorite and pathfinder samples major element multispectral and magnetic properties data were obtained at ares vallis during the mars pathfinder mission to understand the compositional mineralogical and process implications of these data we obtained major element mineralogical and magnetic data for well crystalline and nanophase ferric minerals terrestrial analogue samples with known geologic context and snc meteorites analogue samples include unaltered palagonitic and sulfatetic tephra from mauna kea volcano hydrolytic and acid sulfate alteration steam vent material from kilauea volcano hydrolytic alteration and impactites from meteor crater relithification salient results for mars pathfinder include 1 band depths bd530b and bd600 and the reflectivity ratio r800 r750 are consistent with the dominant ferric mineral being nanophase ferric oxide associated with an unknown amount of h2o and occurring in composite particles along with subordinate amounts of other ferric minerals hematite and hematite plus nanophase goethite are most consistent with the data but maghemite akaganeite schwertmannite and nanophase lepidocrocite are also possible interpretations ferric oxides that are consistently not favored by the data as sole alteration products are jarosites and well crystalline goethite and lepidocrocite 2 the strength of the ferric adsorption edge r750 r445 implies the fe3 fe2 values for pathfinder rock and soil are within the ranges 0 7 3 and 3 20 respectively 3 ferrous silicates are indicated for subsets of pathfinder rocks and soils one subset has a band minimum near 930 nm that can attributed to low ca pyroxene alternatively the band could be a second manifestation of certain ferric oxides including nanophase goethite maghemite akaganeite and schwertmannite another subset has a negative spectral slope from 800 to 1005 nm which could result from the high energy wing of a high ca pyroxene and or olivine band a mixture of bright and dark materials and for rocks thin coatings of bright dust on dark rocks 4 chemical data on pathfinder rocks and soils are consistent with two component mixtures between an andesitic rock with low mgo and so3 concentrations soil free rock and a global basaltic soil with high mgo and so3 concentrations rock free soil pathfinder rock free soil can be modeled as a chemical mixture of snc meteorites and the pathfinder soil free rock 5 pathfinder soil cannot be obtained by chemical alteration of pathfinder rocks by any of the hydrolytic and acid sulfate alteration processes we studied presumably global mixing has obscured and possibly erased the elemental signatures of chemical alteration 6 the strongly magnetic phase in palagonitic and sulfatetic tephra is titanomagnetite and possibly its oxidation product titanomaghemite fe ti spinels the saturation magnetization of the tephra samples 0 5 2 0 am2 kg is at or below the low end of the range inferred for martian dust 4 2 am2 kg implying that lithogenic fe ti spinels are a possible candidate for the martian strongly magnetic phase 7 the predominantly palagonitic spectral signature and magnetic nature of martian soil and dust are consistent with glassy precursors with imbedded fe ti spinel particles comparison with lunar glass production rates suggests that production of sufficient quantities of glassy materials on mars by volcanic and impact processes is sufficient to account for these observations

estimation of rev size and three dimensional hydraulic conductivity tensor for a fractured rock mass through a single well packer test and discrete fracture fluid flow modeling abstract a new methodology is presented to determine the representative elementary volume rev size and three dimensional 3 d hydraulic conductivity tensor for a fractured rock mass first a 3 d stochastic fracture network model was built and validated for a gneissic rock mass based on the fracture data mapped from scanline surveys at the site this validated fracture network model was combined with the fracture data observed on a borehole to generate a stochastic deterministic fracture network system in a cubic block around each packer test conducted at a different depth region in the same borehole each packer test was simulated numerically applying a developed discrete fracture fluid flow model to estimate the influenced region or effective range for the packer test a cubic block of size 18 m with the packer test interval of length about 6 5 m located at the centre of this block was found to be suitable to represent the influenced region using this block size the average flow rate per unit hydraulic gradient defined as the transmissivity multiplied by mean width of flow paths field for fractures was calibrated at different depth regions around the borehole by numerically simulating the packer tests conducted at different depth regions the average flow rate per unit hydraulic gradient of the fractures that intersect the borehole was considered to be quite different to the average flow rate per unit hydraulic gradient of the fractures that do not intersect the borehole a relation was developed to quantify the ratio between these two parameters by studying the directional hydraulic conductivity behaviour of different cubic block sizes having the validated stochastic fracture network and calibrated hydraulic parameters a rev for the hydraulic behaviour of the rock mass was estimated to be a block size of 15 m the hydraulic conductivity tensor in 3 d computed through regression analysis using the calculated directional hydraulic conductivity values in many directions was found to be significantly anisotropic the principal directions of the hydraulic conductivity tensor were found to be agreeable with the existing fracture system of the site further the geometric hydraulic conductivity calculated was found to be comparable to the hydraulic conductivity estimated through the radial flow assumption in continuum porous media

estimation of rock mass deformation modulus and strength of jointed hard rock masses using the gsi system abstract rock mass characterization is required for many applications in rock engineering practice including excavation design support design stope design amongst others for these purposes it is necessary to obtain design input parameters such as deformation moduli and strength parameters for numerical modeling although such parameters can ultimately be determined from in situ tests at the preliminary design stage where access to underground is limited the practical way to obtain these parameters is to apply a rock mass classification system to characterize the rock mass and estimate the rock mass properties over the years many classification systems such as rqd rock mass rating q and geological strength index gsi systems have been developed amongst them the q system is widely used for rock support system design and the gsi system is used for estimating design parameters the gsi system is the only rock mass classification system that is directly linked to engineering parameters such as mohr coulomb hoek brown strength parameters or rock mass modulus however the application of the existing gsi system is hindered by the facts that the use of the system is to some extent subjective and requires long term experience in the present study a quantitative approach to assist in the use of the gsi system is presented it employs the block volume and a joint condition factor as quantitative characterization factors the approach is built on the linkage between descriptive geological terms and measurable field parameters such as joint spacing and joint roughness the newly developed approach adds quantitative means to facilitate use of the system especially by inexperienced engineers the gsi system is applied to characterize the jointed rock masses at two underground powerhouse cavern sites in japan gsi values are obtained from block volume and joint condition factor which in turn are determined from site construction documents and field mapping data based on gsi values and intact rock strength properties equivalent mohr coulomb strength parameters and elastic modulus of the jointed rock mass are calculated and compared to in situ test results the point estimate method is implemented to approximate the mean and variance of the mechanical properties of the jointed rock masses it is seen that both the means and variances of strength and deformation parameters predicted from the gsi system are in good agreement with field test data

considerations and proposal for a best utilization of igrf over areas including a geomagnetic observatory abstract a comparison in the italian area of igrf with a normal field computed at 1979 0 for the same area using 112 repeat stations suggested the use of a particular polynomial approximation of igrf for total intensity this approximation keeps the igrf spatial gradients without changing their time variation while it correctly updates the absolute secular variation level using absolute values from the closest observatory the mathematical procedure used can be extended to compute reference fields for any area that includes a geomagnetic observatory

regional scale demarcation of alteration zone using aster imageries in south purulia shear zone east india implication for mineral exploration in vegetated regions abstract regional scale demarcation of alterations is an important preliminary step in mineral exploration advanced spaceborne thermal emission and reflection radiometer aster imageries here have been used for alteration mapping and iron rich e g gossans area demarcation in a highly vegetated and relatively unexplored part of eastern india namely south purulia shear zone spsz the area is surrounded by mineral rich singhbhum shear zone ssz but the mineral potentiality of spsz has not yet been proven alteration mineral assemblages are comprise of iron rich alteration gossan clay alteration with varying amounts of iron content sericitization ferruginization and chloritization in this paper we discuss a few advantages and limitations of commonly used satellite image processing techniques for mineral mapping we integrate the outputs of band ratio principal component analysis pca pca loading and thresholding termed as directed pca dpca for delineating mineral potential areas our approach mapped the alteration zones with overall 74 accuracy our study leads to demarcation of 28 alteration area within a 10 km wide and 60 km long stretch of spsz two areas namely lawa 23 1 39 31 n 86 4 2 55 e and sindurpur 23 4 38 30 n 86 5 3 99 e were identified as mineral potential zone samples from those areas were studied using xrf microscope and sem with the conclusive presence of mineralization lawa is potential for hydrothermal polymetallic sulfides along with gold mineralization sindurpur is potential for secondary iron and manganese mineralization the study shows that dpca is a useful tool for aster data processing for narrowing target area in preliminary stages of exploration in vegetated zones

multiasperity fault model and the nature of short period subsources we suggest to consider the breaking of an asperity i e a small contact patch between fault walls as a typical subsource producing an elementary short period radiation pulse from a source of a large earthquake based on the results ofdas andkostrov we propose formulas to describe amplitudes and spectra of acceleration for a multiasperity fault source model the stress drop over an asperity is determined in several ways the estimates agree to give the average value of several hundred bar theoretical acceleration spectral shapes for the case of similar asperities agree with the observed ones they reproduce such features as lower frequencyf1 slope peak and high frequency cutoff the statistical stress drop distribution over the population of asperities and also the related distribution of peak accelerations are discussed there distributions are found to be the power law ones with exponent near to 2 this means that acceleration peaks are formed normally by breaking of individual asperities we consider small earthquakes as produced by breaking of single asperities this idea explains the observed correlation between the upper cutoff frequency of acceleration spectrum and the typical characteristic frequency of small earthquakes