syenite associated disseminated gold deposits in the abitibi greenstone belt canada a distinct group of gold deposits in the abitibi greenstone belt is spatially associated with quartz monzonite to syenite stocks and dikes the deposits occur mainly along major fault zones in association with preserved slivers of alluvial fluvial timiskaming type sedimentary rocks the deposits consist of disseminated sulfide replacement zones with variably developed stockworks of quartz carbonate k feldspar veinlets within zones of carbonate albite k feldspar and sericite alteration the syenitic intrusions are broadly contemporaneous with deposition of timiskaming sedimentary rocks and together with disseminated gold mineralization they have been overprinted by subsequent regional folding and related penetrative cleavage disseminated gold orebodies occur within composite syenitic stocks or along their margins along satellite dikes and sills and along faults and lithologic contacts away from intrusions orebodies in these different positions are interpreted to represent proximal to distal components of large magmatic hydrothermal systems centered on and possibly genetically related to composite syenitic stocks

the candelaria punta del cobre iron oxide cu au zn ag deposits chile several iron oxide rich cu au zn ag deposits define an approximately 5 km wide and at least 20 km long belt along the eastern margin of the coastal batholith near copiapo chile this belt includes the large candelaria mine and a group of middle and small sized mines in the punta del cobre district which is located about 3 km northeast of the candelaria deposit estimated geologic resources of the belt are on the order of 700 to 800 million metric tons mt at 1 0 percent cu the ore occurs in veins breccia and stringer bodies and in replacement bodies that are roughly concordant to bedding the orebodies are hosted mainly by volcanic and volcaniclastic rocks of the punta del cobre formation and in places also occur in volcaniclastic intercalations in the lower part of the overlying early cretaceous chanarcillo group most of the larger orebodies in the belt are located where northwest trending brittle faults intersect the contact between massive volcanic and volcaniclastic rocks these northwest faults and a major northeast trending ductile shear zone control portions of the ore of the candelaria deposit chalcopyrite is the only hypogene cu mineral the cu au ore is characterized by abundant magnetite and or hematite and by locally elevated concentrations of ag zn mo and light rare earth elements the ore is hosted mainly in zones with biotite potassium feldspar calcic amphibole epidote alteration at candelaria in the punta del cobre district ore in the deeper parts of the deposits is similarly associated whereas at shallow levels it occurs in zones of biotite potassium feldspar or albite chlorite calcite alteration mineralization at candelaria punta del cobre took place under relatively oxidized conditions manifested by the formation of specular hematite in parts of the district the pseudomorphic replacement of early specular hematite by magnetite during the main iron oxide formation marks a shift toward more reduced conditions or higher temperatures the bulk of the magnetite probably formed at temperatures of about 500 to 600 c the main sulfide stage followed with formation of pyrite and chalcopyrite at temperatures of 470 to 328 c subsequent martitization of the magnetite points to a temperature decrease cooling of the hydrothermal system is also indicated by the homogenization temperatures of 236 c of saline fluid inclusions in late stage calcite oxygen isotope combined with microthermometric data suggest that magmatic fluids or nonmagmatic fluids equilibrated with magmatic silicates were dominant during the main copper mineralization relatively light oxygen isotope signatures of fluids in equilibrium with late calcite suggest mixing with a nonmagmatic fluid e g basinal brines or meteoric waters during the late stages of hydrothermal activity sulfur isotope ratios of chalcopyrite pyrite pyrrhotite and sphalerite from the bronce candelaria las pintadas santos and socavon rampa deposits range from 34scdt values of 0 7 to 3 1 per mil this narrow range of sulfur isotope ratios near 0 per mil is consistent with sulfur of magmatic origin anhydrite from the candelaria mine paragenetically overlaps with chalcopyrite fluid inclusions in this anhydrite homogenize between 340 and 470 c and it has 34scdt values between 14 5 and 17 5 per mil a sulfate sulfide value of 13 4 per mil for a sample with coexisting anhydrite and chalcopyrite is consistent with sulfide sulfate fractionation at temperatures on the order of 400 c ore lead isotope signatures are homogeneous and similar to those of least altered volcanic host rocks and nearby intrusive rocks radiometric ages including new 40ar 39ar ages for hydrothermal alteration at candelaria point to a main cu au mineralization event at candelaria punta del cobre at around 115 ma the ages indicate that ore formation was broadly coeval with batholithic granitoid intrusions and with regional uplift they further imply that the cu au zn ag deposits formed at shallow crustal levels 3 km the stable isotope data the presence of previously reported hypersaline co2 rich fluid inclusions in the main cu ore stage and saline fluid inclusions in late stage calcite the oxidized character of the first ore fluid pulses and the mineralization age coeval with nearby intrusive activity are consistent with but not unequivocally evidence of magmatic fluid contribution into the hydrothermal system

results from the mars global surveyor thermal emission spectrometer the thermal emission spectrometer spectra of low albedo surface materials suggests that a four to one mixture of pyroxene to plagioclase together with about a 35 percent dust component provides the best fit to the spectrum qualitative upper limits can be placed on the concentration of carbonates 10 percent olivine 10 percent clay minerals 20 percent and quartz 5 percent in the limited regions observed limb observations in the northern hemisphere reveal low lying dust hazes and detached water ice clouds at altitudes up to 55 kilometers at an aerocentric longitude of 224 degrees a major dust storm developed in the noachis terra region the south polar cap retreat was similar to that observed by viking

accuracy of plagioclase compositions from laboratory and mars spacecraft thermal emission spectra 1 plagioclase the most abundant mineral in many terrestrial and martian igneous rocks exhibits a range of compositions that reflects changing conditions during crystallization thermal emission spectrometers tes themis and mini tes on board mars spacecraft provide a means of determining average plagioclase compositions directly we demonstrate that spectrally modeled average plagioclase compositions in terrestrial basalts andesites and dacites correspond to measured values to within 10 6 an molar ca ca na 100 of weighted average values and 13 14 an of normative compositions analyses of spectra from two component plagioclase mixtures varied by volume and composition provide additional insight into potential effects of plagioclase zoning considering the variability in types of observed plagioclase zoning patterns in terrestrial volcanic rocks normal zoning calcic cores and sodic rims cannot be assumed and thus cannot account for an apparent sodic bias seen in previous spectrally modeled compositions this bias is better explained by higher abundances of sodic groundmass plagioclase relative to calcic phenocrysts deconvolution modeling of laboratory spectra of physical mixtures convolved to various instrument resolutions predicts that tes themis and mini tes spectra may be used to extract plagioclase compositions to within 9 12 an 11 12 an and 8 12 an respectively of measured values in coarse sand plagioclase mixtures with 1 standard deviations of 4 an for laboratory tes and mini tes resolutions and 6 an for themis resolution

thermal infrared reflectance and emission spectroscopy of quartzofeldspathic glasses 1 this investigation seeks to better understand the thermal infrared tir spectral characteristics of naturally occurring amorphous materials through laboratory synthesis and analysis of glasses because spectra of glass phases differ markedly from their mineral counterparts examination of glasses is important to accurately determine the composition of amorphous surface materials using remote sensing datasets quantitatively characterizing tir 5 25 m spectral changes that accompany structural changes between glasses and mineral crystals provides the means to understand natural glasses on earth and mars a suite of glasses with compositions analogous to common terrestrial volcanic glasses was created and analyzed using tir reflectance and emission techniques documented spectral characteristics provide a basis for comparison with tir spectra of other amorphous materials glasses clays etc our results provide the means to better detect and characterize glasses associated with terrestrial volcanoes as well as contribute toward understanding the nature of amorphous silicates detected on mars

simultaneous inversion of mantle properties and initial conditions using an adjoint of mantle convection through the assimilation of present day mantle seismic structure adjoint methods can be used to constrain the structure of the mantle at earlier times i e mantle initial conditions however the application to geophysical problems is restricted through both the high computational expense from repeated iteration between forward and adjoint models and the need to know mantle properties such as viscosity and the absolute magnitude of temperature or density a priori we propose that an optimal first guess to the initial condition can be obtained through a simple backward integration sbi of the governing equations thus lessening the computational expense given a model with known mantle properties we show that a solution based on an sbi generated first guess has smaller residuals than arbitrary guesses mantle viscosity and the effective rayleigh number are crucial for mantle convection models neither of which is exactly known we place additional constraints on these basic mantle properties when the convection induced dynamic topography on earth s surface is considered within an adjoint inverse method besides assimilating present day seismic structure as a constraint we use dynamic topography and its rate of change in an inverse method that allows simultaneous inversion of the absolute upper and lower mantle viscosities scaling between seismic velocity and thermal anomalies and initial condition the theory is derived from the governing equations of mantle convection and validated by synthetic experiments for both one layer viscosity and two layer viscosity regionally bounded spherical shells for the one layer model at any instant of time the magnitude of dynamic topography is controlled by the temperature scaling while the rate of change of topography is controlled by the absolute value of viscosity for the two layer case the rate of change of topography constrains upper mantle viscosity while the magnitude of dynamic topography determines the temperature scaling lower mantle viscosity when upper mantle lower mantle density anomaly dominates the flow field this two stage scheme minimizes the tradeoff between temperature and lower mantle viscosity for both cases we show that the theory can constrain mantle properties with errors arising through the adjoint recovery of the initial condition for the two layer model this error is manifest as a tradeoff between the temperature scaling and lower mantle viscosity

dynamic restoration of profiles across diapiric salt structures numerical approach and its applications abstract the backstripping method that is widely used in basin analysis sometimes fails for salt bearing basins because the highly mobile and buoyant salt deforms its sedimentary overburden we present a numerical approach for 2 d dynamic restoration of cross sections through successive earlier depositional stages the approach is based on a solution of the inverse problem of the gravitational rayleigh taylor instability and combines the galerkin spline finite element method with interface tracking and a backstripping method our model interprets basin profiles as multiple layers of viscous fluids with various densities and viscosities the evolution of salt structures is modelled backward in time by removing successively younger layers and restoring older layers and any diapirs to the stage they were likely to have been we test the sensitivity of the restoration technique to small variations in density of the layers at different stages in the evolution of diapiric structures the applicability of the technique was demonstrated by reconstructions of upbuilt and downbuilt diapirs the technique is used to restore a depth converted seismic cross section through the south eastern part of the pricaspian salt basin mature salt diapirs in the section are shown to have been downbuilt from a salt layer with an initially uniform thickness as a result of differential sedimentary loading until the end of the triassic before one of the diapirs was buried and actively upbuilt the numerical approach is well suited for restoration of cross sections with ductile overburdens but despite limitations can be developed to 3 d restorations and other rheologies

forward and reverse modeling of the three dimensional viscous rayleigh taylor instability a combined nite dierence spectral method is used to model the 3d viscous rayleigh taylor instability numerically calculated growth rate spectra are presented for an initial sinusoidal perturbation of the interface sep arating two fluids with amplitude 10 3 h and 0 2h w here h is the height of the system at small initial amplitude growth rate spectra closely follow linear theory whereas the calculation with higher initial amplitude shows wavelength selection towards 3d perturbations numerical simulations and analytical theory are used to evaluate the applicability of previous 2d numerical models which is shown to depend on 1 the wavelength and amplitude of an initially 2d si nusoidal perturbation and 2 the amplitude of background noise it is also shown that reverse backward modeling is capableofrestoringtheinitialgeometryaslongasoverhangs are not developed if overhangs are present the possibility ofrestoringtheinitialconditionsislargely dependentonthe stage of overhang development

impact of glacier changes on ecosystem of proglacial lakes in high mountain regions of east siberia russia mountain lakes in east siberia have been studied for recent changes in water chemistry turbidity and diatom assemblages preserved in bottom sediments we performed a regional analysis of the relative effect of climate and glacier changes on change in diatom diversity and supply of meltware in proglacial lakes we analysed sediment records from east siberian glacier lakes using geochemical and diatoms proxies we found that dramatic changes in communities and abundance of diatoms and biogenic proxy could be induced by low nutrient concentrations in glacial lakes and high turbidity due to active degradation of glaciers and snow patches as a result of the global increase in temperature in the northern hemisphere our evidences show that diatoms have been gradually decreased since ca the 1880s a significant tendency towards diatom reducing occurred at high summer regional temperatures this tendency may be attributed to the fact that glaciers and snow patches thawed actively in east siberia during ca 1880 1958 which was induced by the beginning of the recent warming ca 1850 1860 and a long period of relatively warm regional climate from ca 1900 to 1960

numerical analysis of how sedimentation and redistribution of surficial sediments affects salt diapirism abstract two dimensional finite element models are used to study how sedimentation and redistribution of sediments on the upper surface affects the development of subsurface salt diapirs a rising diapir creates a bulge flanked by topographic lows in a generally accumulating sedimentary pile we find that the rate at which this topography is flattened by erosion and redeposition controls the style of diapirism this is because the redistribution of material from topographic highs to flanking lows is equivalent to changing the effective forces acting on the salt redistributing a potential topography modulates diapiric growth rate the main effects of including surficial sediment redistribution in numerical models of diapirism are 1 1 diapirs grow 10 100 times faster 2 2 diapirs may rise above their level of neutral buoyancy and extrude 3 3 diapirs assume finger or stock like shapes rather than mushroom or balloon on string shapes 4 4 layers in the surrounding sediments remain nearly horizontal and only steepen sharply near the diapir in effect the rate of redistribution of surficial overburden strongly controls the mode of diapirism sediment redistribution referred to as erosion for brevity is modeled using a one dimensional diffusion equation we show the results of two different erosion rates infinitely slow no erosion and extremely fast which redistributes surficial sediments but does not remove them from the system we show that the shapes of model diapirs rising beneath surfaces subjected to rapid erosion simulate salt diapirs in the gulf of mexico columnar diapirs indicate rapid deposition on the shelf and plug like diapirs slow sedimentation on the abyssal plane diapirs rising beneath surfaces with negligible erosion have the mushroom shapes interpreted for salt diapirs in central iran

surface mineral mapping at steamboat springs nevada usa with multi wavelength thermal infrared images abstract the purpose of this study was to evaluate the use of airborne multispectral and hyperspectral thermal infrared tir image data for mapping surface minerals characteristic of active geothermal systems tir image data from the master multispectral spectrometer and the sebass hyperspectral spectrometer were acquired over steamboat springs nevada usa in september 1999 spectral emissivity information was extracted from the data and used to generate mineral maps using the master data it was possible to map the extent of the active geothermal area as well as silica rich vs clay rich areas using the sebass data the same areas could be mapped and additionally the presence of several minerals including opal quartz alunite anorthite albite and kaolinite could be identified the sebass data also detected previously unidentified hydrous sulfate minerals tamarugite and alunogen forming around active fumaroles laboratory spectral data and xrd analyses of field samples confirmed the dominant mineral phases identified remotely the airborne field and laboratory data together with temperature anomaly and fumarole location data from other studies were synthesized and linked to the surface geology to determine the diagnostic surface mineral expression that could be mapped with tir remotely sensed data for future exploration for similar geothermal systems opaline sinter deposits are the most diagnostic surface expression of hot spring activity at steamboat springs because they represent areas of the recent geyser activity the differentiation between opal and chalcedony deposits and the identification of hydrous sulfate minerals forming around active fumaroles are also important because chalcedony represents ancient sinter deposits and hydrous sulfate minerals indicate locations of fumaroles that may be venting diffusely with no geyser activity the surface expression of the geothermal system at steamboat springs is small which emphasizes the need for high spatial resolution airborne imagers the 90 m pixels of aster tir data over the same area were only capable of resolving the area of past and recent sinter deposits together master multispectral tir data covered the entire area 12 km 2 at 5 m spatial resolution and were capable of defining the extent of the sinter deposits and zones of hydrothermally altered rocks the sebass image swath was too narrow 256 m to add significant spatial information to the overall map but the high spectral content identified several important minerals related to the local geology and the mineralogic surface expression of the geothermal system

a systematic technique for the sequential restoration of salt structures abstract a method is described for the sequential restoration of cross sections in areas of salt tectonics where deformation is confined to the salt and higher layers the subsurface geometry evolves with time through the interaction of various processes sedimentation compaction isostatic adjustment thermal subsidence if present faulting and salt withdrawal diapirism the technique systematically calculates and removes the effects of each of these processes during specified time intervals defined by the interpreted horizons it makes no assumptions about salt kinematics and generally results in the area of the salt layer changing through time the method is described for restoration of extensional terranes but it is also suitable for areas of contractional salt tectonics with only minor modifications after converting an interpreted seismic profile to depth the top layer is stripped off and the underlying section is decompacted according to standard porosity depth functions a deep baseline unaffected by compaction or deformation is used to restore any isostatic compensation or thermal subsidence isostasy is calculated according to the airy model and differential sedimentary loading across a section is shown to be approximately balanced by changes in salt thickness so that the load is evenly distributed after these processes have been reversed the resulting geometry and the seismic data are used to create the sea floor template for structural restoration fault offsets are removed and the layers down to the top salt are restored to this template while the base salt remains fixed the resulting space between the restored top salt and the fixed base salt defines the restored salt geometry in addition the difference between the sea floor template and a fixed sea level provides a measure of the change in water depth ignoring eustatic changes in sea level the technique is applied to an interpreted seismic profile from the eastern green canyon ewing bank area of offshore louisiana the section is characterized by a variety of salt structures including salt rollers a diapiric massif a remnant salt sheet and a salt weld which are shown to have derived from an originally continuous salt sheet which has been modified by sedimentary loading early loading created vertical basin growth that was accommodated primarily by salt withdrawal and associated diapiric rise through the process of downbuilding once the salt weld formed continued sedimentation was accommodated by a lateral increase in basin size caused by down dip extension on listric growth faults

structural features and formation conditions of mud diapirs in the andaman sea basin data from offshore oil and gas explorations have revealed that mud diapirs occur widely not only at continental margins but also in foreland basins and may have played an important role in the entrapment of oil and gas although the structural features and formation mechanism of salt diapirs have been extensively investigated mud diapirs are still not fully understood largely due to the difficulty of identifying them from seismic data in this paper the structural features and main controlling factors of mud diapirs in the andaman sea basin are investigated based on seismic profiles combined with drilling data and regional tectonic settings the results show that there are five types of mud diapir in the andaman sea basin turtleback mud diapir mud dome piercing mud diapir mud volcano and gas chimney like mud diapir turtleback mud diapirs mainly occur in the southern segment of the accretionary wedge of the andaman sea basin which is far from the bengal fan and characterized by low deposition rate and strong compression tectonic setting piercing mud diapirs exist mainly in the central segment of the accretionary wedge which is close to provenances of sediments and characterized by rapid sedimentation rates large mudstone thickness and transpressional tectonic setting mud domes and mud volcanoes mainly occur in the northern segment of the accretionary wedge which is characterized by rapid sedimentation rates large mudstone thickness and sedimentary wedge growth tectonic setting the gas chimney like mud diapirs only occur in the northern segment of the back arc depression close to the sagaing strike slip fault belt which is characterized by high deposition rate large mudstone thickness and high geothermal gradient these features suggest that thick mudstone deposit rapid sedimentation rates large geothermal gradient strong tectonic stress and gravitational spreading and sliding may have prompted the formation of mud diapirs in the andaman sea basin

quartzose mafic spectral feature space model a methodology for extracting felsic rocks with aster thermal infrared radiance data abstract the original spectral features of felsic rocks are often intermingled with other surface objects which results in difficulty of detecting felsic rocks using remote sensing techniques few felsic rock indices were proposed and visual interpretation with rgb false color composition is widely used to detect felsic rocks this paper aims to construct a two dimensional spectral feature space model to extract felsic rocks using aster thermal infrared radiance data the study area is located in northern qinghai province western china with average altitude of approximately 4200 m a large number of training pixels of mafic ultramafic rock quartz rich rock felsic rock carbonate rock and vegetation were selected from the aster images as samples of these surface objects then we used a quartz rich rock index qi qi band14 0 844 band12 1 897 and a mafic ultramafic rock index mi mi 0 915 band10 band13 1 437 to generate a two dimensional scatter plot the plot was named after quartzose mafic spectral feature space qmfs the samples show an approximate triangular shape in the qmfs mafic ultramafic rock quartz rich rock and carbonate rock are located in separate locations in the three vertex regions respectively while felsic rock is located in the central region of the triangle next we calculated a linear belt of silicate rocks in which silicate rocks vary regularly by using a linear regression analysis in the qmfs statistical characteristics of the felsic rock samples are analyzed afterwards a polygon which delineates the distribution of felsic rock samples was constructed from the linear belt of silicate rocks then we generated a system of inequalities based on the equations of the edges of the polygon the application of the inequalities to the aser images shows a good performance of the qmfs for extracting felsic rocks

the use of ftir methods for rapid determination of contents of mineral and biogenic components in lake bottom sediments based on studying of east siberian lakes technique for estimation of contents of the major components of lake bottom sediments using single peak analysis procedure has been developed the technique allows estimation of biogenic silica bsi total inorganic carbon tic total organic carbon toc and quartz and feldspars content in bottom sediments the calibration models are based on the following spectral regions bands at 646 cm 1 feldspars 695 cm 1 quartz 874 cm 1 tic the range from 818 to 835 cm 1 bsi the range of c h vibrations 2800 3000 cm 1 toc the technique has been probed for a number of eastern siberian lakes and results are compared with the data of other methods it has been shown that the use of single peak analysis procedure allows very rapid ftir estimation of the major components content in bottom sediments with accuracy which is acceptable for many tasks

quantitative compositional analysis of sedimentary materials using thermal emission spectroscopy 1 application to sedimentary rocks thermal emission spectroscopy is used to determine the mineralogy of sandstone and mudstone rocks as part of an investigation of linear spectral mixing between sedimentary constituent phases with widespread occurrences of sedimentary rocks on the surface of mars critical examination of the accuracy associated with quantitative models of mineral abundances derived from thermal emission spectra of sedimentary materials is necessary although thermal emission spectroscopy has been previously proven to be a viable technique to obtain quantitative mineralogy from igneous and metamorphic materials sedimentary rocks with natural variation of composition compaction and grain size have yet to be examined in this work we present an analysis of the thermal emission spectral 270 1650 cm 1 characteristics of a suite of 13 sandstones and 14 mudstones x ray diffraction and traditional point counting procedures were all evaluated in comparison with thermal emission spectroscopy results from this work are consistent with previous thermal emission spectroscopy studies and indicate that bulk rock mineral abundances can be estimated within 11 2 for detrital grains i e quartz and feldspars and 14 8 for all other mineral phases present in both sandstones and mudstones in comparison to common in situ techniques used for determining bulk rock composition clay sized to fine silt sized grained phase identification is less accurate with differences from the known ranging from 5 to 24 on average nevertheless linear least squares modeling of thermal emission spectra is an advantageous technique for determining abundances of detrital grains and sedimentary matrix and for providing a rapid classification of clastic rocks

numerical models of complex diapirs abstract numerically modelled diapirs that rise into overburdens with viscous rheology produce a large variety of shapes this work uses the finite element method to study the development of diapirs that rise towards a surface on which a diapir induced topography creeps flat or disperses erodes at different rates slow erosion leads to diapirs with mushroom shapes moderate erosion rate to wine glass diapirs and fast erosion to beer glass and column shaped diapirs the introduction of a low viscosity layer at the top of the overburden causes diapirs to develop into structures resembling a napoleon hat these spread lateral sheets

infrared spectroscopy in geochemistry exploration geochemistry and remote sensing penelope king michael ramsey and gregg swayze editors mineralogical association of canada short course series volume 33 2004 284 pp isbn 0 921294 33 6 price 40 this 284 page long volume including 20 color plates and an index is a collection of invited papers that originated from a short course on infrared spectroscopy for geoscientists organized by the mineralogical association of canada as outlined in the preface of the volume the main objective of the short course was to update geoscientists on advances in infrared technology being developed in the laboratory through to satellite based systems with particular emphasis on measurement and mapping of mineral composition for more effective ore deposit exploration as well as for environmental monitoring and assessment of natural and anthropogenic processes such a volume would in theory be of interest to readers of economic geology particularly those interested in understanding how a new generation of proximal and remote spectral sensing technologies can be used to measure and target prospective economic mineralization the book essentially aims to

mapping surface mineralogy and scattering behavior using backscattered reflectance from a hyperspectral midinfrared airborne co sub 2 laser system miraco sub 2 las airborne high spectral resolution thermal infrared tir miraco sub 2 las reflectance data were evaluated for mapping surface mineralogy and scattering behavior for a variety of semi arid geological test sites in australia miraco sub 2 las is a rapidly tuned airborne co sub 2 laser system that measures backscattered bidirectional reflectance at 100 wavelengths between 9 1 and 11 2 spl mu m for 2 m footprints in line profile mode an operational methodology is described that permits reduction of the raw airborne signal to ground reflectance this ground reflectance has two major properties namely wavelength dependent mineralogical variations and reflection albedo variations related to surface roughness comparisons between the airborne miraco sub 2 las spectra and laboratory directional hemispherical reflectance dhr spectra show the same spectral shapes though differences in average reflectance albedo occur for some types of rocks the minerals identified using miraco sub 2 las include silicates for example quartz microcline plagiodase almandine spessartine talc tremolite and kaolinite and carbonates dolomite and magnesite as well as vegetation dry and green many of the diagnostic spectral features that allow identification of these materials are narrow 0 2 spl mu m making them difficult to detect with broadband tir systems like the airborne tims and satelliteborne aster based on an empirical relationship between the minimum and maximum reflectance established using laboratory dhr spectra a method is proposed that allows the use of miraco sub 2 las data to identify surfaces that are characterized by lambertian or specular scattering the miraco sub 2 las results show that lambertian type scatterers include soils and many types of isotropic rocks

automated lithological mapping using airborne hyperspectral thermal infrared data a case study from anchorage island antarctica the thermal infrared portion of the electromagnetic spectrum has considerable potential for mineral and lithological mapping of the most abundant rock forming silicates that do not display diagnostic features at visible and shortwave infrared wavelengths lithological mapping using visible and shortwave infrared hyperspectral data is well developed and established processing chains are available however there is a paucity of such methodologies for hyperspectral thermal infrared data here we present a new fully automated processing chain for deriving lithological maps from hyperspectral thermal infrared data and test its applicability using the first ever airborne hyperspectral thermal data collected in the antarctic a combined airborne hyperspectral survey targeted geological field mapping campaign and detailed mineralogical and geochemical datasets are applied to small test site in west antarctica where the geological relationships are representative of continental margin arcs the challenging environmental conditions and cold temperatures in the antarctic meant that the data have a significantly lower signal to noise ratio than is usually attained from airborne hyperspectral sensors we applied preprocessing techniques to improve the signal to noise ratio and convert the radiance images to ground leaving emissivity following preprocessing we developed and applied a fully automated processing chain to the hyperspectral imagery which consists of the following six steps 1 superpixel segmentation 2 determine the number of endmembers 3 extract endmembers from superpixels 4 apply fully constrained linear unmixing 5 generate a predictive classification map and 6 automatically label the predictive classes to generate a lithological map the results show that the image processing chain was successful despite the low signal to noise ratio of the imagery reconstruction of the hyperspectral image from the endmembers and their fractional abundances yielded a root mean square error of 0 58 the results are encouraging with the thermal imagery allowing clear distinction between granitoid types however the distinction of fine grained intermediate composition dykes is not possible due to the close geochemical similarity with the country rock

the salt dome problem a multilayered approach the dynamical evolution of buoyancy driven geological systems is mainly influenced by two physical parameters density and equivalent viscosity salt structures are an appropriate geological representation of these systems important variations of these parameters are directly related to changes in mass and thus the internal structures themselves and their changes in time become significant parameters in order to decipher these structures in nature by means of experiments it is therefore necessary to extend model calculations on intrusion processes to multilayer systems a two dimensional finite element program has been developed to simulate the rise of individual diapirs through multi layered overburdens exhibiting newtonian viscous rheologies this program includes the following features arbitrarily shaped interfaces between different fluid boundaries layers of finite thickness and subsidence of the model within the model frame as well as time and depth dependent material properties this paper is concerned with single diapirs intruding upbuilt multilayered overburdens the effect of a subsiding salt base due to pure downbuilding and differential loading of gravitationally unstable distributions of mass variable density and viscosity of the overburden with depth control the shape and ascent rates of diapiric bodies the subsidence history of salt structures dominates the development of maximum horizontal pressure gradients with time and thus the ascend histories of diapirs

rheological and tectonic modeling of salt provinces abstract technological improvements and a more rigorous research approach have led the petroleum industry to renew and expand its interest in physical modeling of faulting associated with halokinesis salt tectonics and the formation of structural hydrocarbon traps can be reproduced in models using viscous polymers for the substratum and frictional plastic granular materials for the overburden the fault patterns simulated in these dynamically scaled models are remarkably similar to those in depth converted seismic sections scale models are therefore useful for generating new concepts and for reconstructing the structural evolution of hydrocarbon traps although even unsealed models may help generating ideas the full transfer of quantitative data requires that models be dynamically scaled to their natural prototypes previously published scaling theory for salt tectonics has erroneously assumed fluid behaviour of the overburden this paper provides a sound scaling approach for geological deformations involving brittle overburdens on ductile substrata rheological data from overburden rocks and salt are compiled and compared to model rheologies using dimensions of laboratory analogs and other intrinsic material properties scaling approaches are compared and rules are formulated for achieving dynamic similarity in models of salt tectonics including those with synkinematic sedimentation

salt redistribution during extension and inversion inferred from 3d backstripping abstract a 3d backstripping approach considering salt flow as a consequence of spatially changing overburden load distribution isostatic rebound and sedimentary compaction for each backstripping step is used to reconstruct the subsidence history in the northeast german basin the method allows to determine basin subsidence and the salt related deformation during late cretaceous early cenozoic inversion and during late triassic jurassic extension in the northeast german basin the deformation is thin skinned in the basinal part but thick skinned at the basin margins the salt cover is deformed due to late triassic jurassic extension and late cretaceous early cenozoic inversion whereas the salt basement remained largely stable in the basin area in contrast the basin margins suffered strong deformation especially during late cretaceous early cenozoic inversion as a main question we address the role of salt during the thin skinned extension and inversion of the basin in our modelling approach we assume that the salt behaves like a viscous fluid on the geological time scale that salt and overburden are in hydrostatical near equilibrium at all times and that the volume of salt is constant because the basement of the salt is not deformed due to decoupling in the basin area we consider the base of the salt as a reference surface where the load pressure must be equilibrated our results indicate that major salt movements took place during late triassic to jurassic e w directed extension and during late cretaceous early cenozoic nne ssw directed compression moreover the study outcome suggests that horizontal strain propagation in the salt cover could have triggered passive salt movements which balanced the cover deformation by viscous flow in the late triassic strain transfer from the large graben systems in west central europe to the east could have caused the subsidence of the rheinsberg trough above the salt layer in this context the effective regional stress did not exceed the yield strength of the basement below the rheinsberg trough but was high enough to provoke deformation of the viscous salt layer and its cover during the late cretaceous early cenozoic phase of inversion horizontal strain propagation from the southern basin margin into the basin can explain the intensive thin skinned compressive deformation of the salt cover in the basin the thick skinned compressive deformation along the southern basin margin may have propagated into the salt cover of the basin where the resulting folding again was balanced by viscous salt flow into the anticlines of folds the huge vertical offset of the pre zechstein basement along the southern basin margin and the amount of shortening in the folded salt cover of the basin indicate that the tectonic forces responsible for this inversion event have been of a considerable magnitude

a 850 year record climate and vegetation changes in east siberia russia inferred from geochemical and biological proxies of lake sediments east siberia is very sensitive to moisture regimes because it is located in a margin area where moisture from the north atlantic is strongly depleted and the penetration of the east asian monsoon is weak and rare in winter months the siberian anticyclone strongly blocks and reduces the external influences on the region the high latitude of the study area at 52 n is probably sensitive to variation in insolation and solar activity we analysed a 42 cm long sediment record from lake mountain located in east siberia russia for geochemical mineralogical subfossil diatoms chironomids and pollen to provide a reconstruction of the climate history of the area for the last 850 years according to our reconstruction a clear decrease in summer temperatures occurred in east siberia after ca 1400 and we linked this temperature drop with the beginning of the little ice age the coldest summer occurred about ca 1570 1700 and 1830 1900 we assumed that the most significant changes of the lake bio productivity and the catchment area were occurred about ca 1160 1350 1350 1590 1590 1730 1730 1900 and 1940 to the present the most dramatic period with unfavorable climate conditions for lake biota was during 1590 1730

geothermal evolution of the astrakhan arch region of the pricaspian basin the astrakhan arch region contains one of the largest sub salt structures of the pricaspian basin where perspectives for hydrocarbon generation and accumulation in the devonian to carboniferous deposits are considered to be high the paper addresses the problem of structural and geothermal evolution of the region deformed by salt movements initially we developed a model of the regional structural evolution along a geological profile using the volume balancing and back stripping methods and geo logical constraints on the sedimentation erosion and paleo water depths then we developed geothermal models along the study profile associated with the regional structural evolution the models were constrained by the temperatures measured in four deep boreholes along the profile we show that the present temperatures and heat flux are influenced by the presence of salt diapirs since the early carboniferous and till middle permian times the temperatures predicted by the models vary significantly due to the regional transgression and the presence of sea water the temperature of devonian carboniferous carbonates increases since the late permian time of post salt deposition and attains its maximum values in the sw part of the profile if the model assumptions concerning the constant vertical and zero lateral heat fluxes are valid we can conclude that hydrocarbons are most likely to be generated in the sw part of the region for the post early permian time

phase segregation boiling and reinjection at the los azufres geothermal field mexico monitored by water stable isotopes chloride and enthalpy abstract monitoring the impact of brine reinjection is crucial to the sustainable exploitation of geothermal resources reinjection monitoring at the los azufres geothermal field mexico has historically been carried out by investigating the temporal and spatial evolution of chloride and the stable isotopic composition of water here we review the evolution of the stable isotopic composition of the total fluid discharge td since the earliest measurements in 1980 integrating new data obtained in 2014 based on dtd and 18otd values measured in 2014 two groups of fluids were identified the first group is characterized by dtd and 18otd similar to those measured in previous survey years 1980 1982 1983 1986 and 2000 the second group shows a large positive shift in the hydrogen isotopic composition dtd of 10 compared to the first group the evolution of reinjected brines and production wells over time between 1980 and 2014 shows 18otd and dtd enrichment until 2000 this is followed between 2000 and 2014 by a slight decrease in 18otd values and a net increase in dtd explained by extensive phase segregation and boiling at temperatures of over 280 c the observed trend suggests that a steam phase caused by boiling is invading the reservoir and the phenomenon is observed in both production and reinjected fluids a comparison of the spatially kriged 2000 and 2014 18otd and dtd datasets reveals that reinjected brine is spreading progressively to the eastern part of the field mainly in the southern production zone spz and through e w corridors delimited by the e w fault systems which underlie the secondary permeability of the reservoir however reinjection is still not able to suppress boiling in the main production zone this situation needs to be taken into account in developing future reinjection strategies to counterbalance the substantial fluid extraction from the field

restoration of cross sections to constrain deformation processes of extensional terranes abstract restoring balanced cross sections constrains the possible deformation processes affecting extensional terranes with a ductile substratum such as salt and syndeformational sedimentation cross sections are divided into fault blocks and shear domains each of which can be undeformed with a different set of parameters the success of restorations is judged by compatibility between the blocks and the reasonableness of the restored structures fault blocks in physical models restore with simple shear at about 60 dipping in the direction which removes extension corresponding to an antithetic orientation in the hangingwalls of normal growth faults and subparallel to the fault in the footwall other components of the deformation are rigid rotation translation and decompaction shear angles inferred from natural examples are more varied ranging from vertical to moderately inclined nearly always dipping in a direction that removes extension

numerical modelling of salt diapirism influence of the tectonic regime abstract in the context of sedimentary basin mechanics salt diapirism has usually been described as a phenomenon initiated and driven by gravity instabilities associated with buoyant forces or differential loading this result holds essentially for an approximation of linear rheologies of both salt and overburden this has been contested by recent analog models and analytical studies buoyancy alone cannot drive salt diapirism through a brittle overburden regional extension or compression could be a necessary mechanism likely to promote salt diapirism numerical models are presented here to describe the relative effects of gravity and lateral forces on the dynamics of salt diapirism the numerical scheme is based on a viscoplastic approximation of deformations and an updated lagrangian description of kinematics which allows a study of large non linear deformations of salt bodies and the evolution of material interfaces this scheme takes into account brittle and ductile deformations of sediments moreover it describes the initiation and evolution of shear bands which play a crucial role in basin mechanics and especially in the dynamics of salt diapirism we show why extension is the most propitious driving mechanism of diapirism necking and faulting induced by extension promote and drive salt diapirism in the case of a brittle overburden this result holds with or without buoyancy forces this demonstrates that buoyancy which alone is not sufficient to break a brittle overburden is not a necessary mechanism either buoyancy however enhances diapirism induced by lateral forces in contrast with extension salt diapirism during compression is strongly constrained by the rheology of the overburden a brittle mode of deformation favours faulting rather than buckling induced thrusting and thickening of the overburden inhibit massive diapirism and favour the confinement of small salt plugs finally the post extension stability of a mature diapir produced by extension is presented

numerical approach to problems of gravitational instability of geostructures with advected material boundaries summary we present a numerical approach for solving 2 d mantle flow problems where the chemical composition changes abruptly across intermediate boundaries the method combines a galerkin spline technique with a method of integration over regions bounded by advected interfaces to represent discontinuous variations of material parameters it allows direct approximation of a natural free surface position instead of a posteriori calculation of topography from the normal stress at the upper free slip boundary we formulate a model where a viscous incompressible fluid filling a square box is divided into layers not necessarily horizontal by advected boundaries across which the density and viscosity change discontinuously no slip or free slip conditions are assumed at the model sides the suggested approach being eulerian avoids the difficulties due to material discontinuities at intermediate boundaries like the moho or the earth s surface and is also free from the deficiencies of the lagrangian approach always resulting in mesh distortion we present two geophysical cases analysed by this technique the first case concerns the formation of sedimentary basins under the effects of heavy bodies sinking in the asthenosphere and of load due to sedimentary infills the second case demonstrates the evolution of salt diapirs and shows how their growth is affected by a laterally inhomogeneous sedimentary layer this numerical approach is well suited for problems of gravitational instability with discontinuities of density and viscosity across advected boundaries

the geodynamic evolution of the precaspian basin kazakhstan along a north south section abstract several hypotheses exist for the origin and evolution of the precaspian basin there are more than 20 km of sediments deposited yet there is little consensus on the causes of the subsidence except for the presence of a thick salt layer lower permian the main problem is the chronostratigraphic interpretation of the sediments in the centre of the basin where the calibration of seismic data with well data from the basin margins is problematic at deep levels the age of the deepest sediments could be either riphean or devonian a generalised cross section of the precaspian basin roughly perpendicular to the central elongated e w depocentre is used to represent the basin s evolution several evolutionary steps from the end of the riphean until the present are demonstrated tectonic subsidence analysis indicates that there are six main phases of evolution 1 subsidence during an active rifting phase in riphean times 2 rifting during the vendian ordovician poorly dated 3 significant subsidence during the late devonian in an extensional context possibly due to back arc rifting 4 acceleration of subsidence during the late carboniferous permian synchronous with or just following the closure of the uralian ocean a major subsidence phase in the dniepr donets basin and possible subduction to the south of the basin 5 renewed rifting during the triassic coincident with a general phase of extension in eurasia and the opening of the neo tethys and 6 neotectonic subsidence resulting from crustal down bending in a generally compressional setting the nature of the crust underlying the basin is not well known it could be riphean early palaeozoic or devonian oceanic crust or continental crust attenuated during the several episodes of supposed rifting between the riphean and the triassic estimations of crustal thickness in the basin vary and they depend on the interpretation of a high velocity layer situated at the base of the crust the presence and general distribution of this layer is confirmed by gravity data it may be considered as the uppermost mantle as oceanic crust metamorphosed into eclogite at depth during collision and then exhumed and emplaced at the base of the crust or as lower crust transformed in situ into eclogites the crustal thinning factor leading to the observed present crustal thickness assuming an initial thickness of 40 km is 3 3 in the two first cases and 2 in the latter if the crust is considered to be continental the geophysical and subsidence data are discussed in terms of basin forming mechanisms such as 1 intracontinental rifting of early palaeozoic devonian or permo triassic ages 2 oceanisation of continental crust during riphean or devonian time 3 eclogititisation at the base of the crust in the upper mantle or by metamorphism of subducted oceanic crust and 4 down bending due to compressional forces or mantle flow induced by subduction collision processes in carboniferous and recent times

thermal infrared spectroscopy and partial least squares regression to determine mineral modes of granitoid rocks 1 in this paper we present an approach to extracting mineralogic information from thermal infrared tir spectra that is not based on an input library of pure mineral spectra nor tries to extract spectral end members from the data instead existing modal mineralogy for a number of samples are used to build a partial least squares regression plsr model that links the mineralogy of the samples to their respective tir spectral signatures the resulting plsr models can be applied to a larger group of samples for which the mineralogic composition can be estimated from the tir spectra alone thermal infrared reflectance spectra were recorded from 1330 625 cm 1 7 5 to 16 0 m the method is tested on igneous rocks from a porphyry copper deposit in yerington nevada as a reference modal mineralogic composition was determined with traditional polarization microscopy on thin sections partial least squares regression models were developed to link the thermal infrared spectra to the thin section determined mineral modes of alkali feldspar plagioclase and quartz as well as the average plagioclase composition information results indicate that rock samples can be classified successfully in a quartz alkali feldspar plagioclase diagram based on thermal infrared spectroscopy and partial least squares regression modeling estimated errors for the mineralogic composition model results were found to be smaller or equal to traditional methods with errors of 5 1 absolute for alkali feldspar 8 5 absolute for plagioclase and 6 9 absolute for quartz the regression model for plagioclase composition predicted with estimated errors of 7 8 mol anorthite

continuous restoration of deformed shapes through the construction of a reverse displacement gradient and its application to granite emplacement in central north china this paper presents a new technique to restore 2d 3d deformed shapes by minimization of the misfit between measured and theoretical reverse displacement gradients owing to its relatively direct and objective nature the procedure ensures continuity of displacement across the boundaries between abutting elements the procedure also minimizes the additional distortion of the elements that results from the compatibility of retro deformation between abutting elements we apply the technique to the mesozoic fangshan granodioritic pluton fgp in western beijing central north china based upon the measured strain of deformed enclaves about 78 area of the present central zone can be restored by retro deformation of the marginal and transitional zones as a result of the emplacement of the central zone deformation also occurred in both the outer zones and the wall rocks predominantly by ductile flow the associated deformation in the outer zones with or without the involvement of the wall rocks created space for the emplacement of the central zone in addition vertical expansion was effective in creating space for subsequent emplacement producing approximately one third of the volume created by later expansion thus ballooning is a viable mechanism for emplacement of the fgp

paleostress pattern and salt tectonics within a developing foreland basin north western subhercynian basin northern germany analysing the paleostress field in sedimentary basins is important for understanding tectonic processes and the planning of drilling campaigns the subhercynian basin of northern germany is a perfect natural laboratory to study the paleostress field in a developing foreland basin the simple layer cake geometry of the basin fill is dominated by several piercing and non piercing salt structures we derived the paleostress field from the orientation of fracture sets faults slickensides and stylolites on a regional scale the basin fill is characterized by a horizontal compressional paleostress vector that is mainly nne ssw oriented which reflects the late cretaceous inversion phase in central europe we show that the local paleostress field is distinctly perturbated due to the salt structures along the edge of the salt pillows the maximum horizontal paleostress vector is deflected by up to 90 from the regional trend in the case of the elm salt pillow it forms a radial pattern restoration of balanced cross sections demonstrates at least 9 of the shortening of the north western part of the subhercynian basin was achieved by folding the salt structures in the north western subhercynian basin are the result of varying stress conditions initial extension in the triassic caused first salt movements that prevailed during the jurassic and early cretaceous most important is the late cretaceous contractional phase that shortened the diapirs and led to the formation of the salt pillows between diapirs due to detachment folding we derive four main controlling factors for such salt dominated contractional basins 1 the wedge shape basin fill is the product of the dynamic load at the southern margin of the basin 2 a basal salt layer fed the diapirs and acted as a detachment horizon during the later shortening 3 detachment folding was the dominating deformation mechanism during contraction and 4 the pre existing diapirs controlled the position of the detachment folds

thermal infrared spectroscopy on feldspars successes limitations and their implications for remote sensing abstract minerals of the feldspar group are the most common on earth feldspars are economically important in two ways either as industrial minerals or as a vector to ore for mineral deposits in order to use feldspars for classifying rock compositions or metasomatic conditions during rock alteration events there is a need for analytical methods to identify and classify feldspars traditionally feldspar composition and structure have been investigated using methods such as optical microscopy electron microprobe analysis empa cathodoluminescence and x ray diffraction xrd analysis in this paper infrared techniques 0 7 25 m are reviewed in detail and investigated in how far some of the traditional analytical methods can be replaced by infrared spectroscopy successes as well as limitations of infrared approaches are highlighted and existing work is scrutinized in terms of its applicability to remote sensing techniques even though numerous studies on mid infrared mir spectroscopy of feldspars exist their results often cannot be directly related to remote sensing applications examples are the effects of feldspar twinning exsolution textures and structural state on infrared spectra the applicability of the results to emission remote sensing requires further research it has been shown that linear unmixing of laboratory infrared spectra of rocks works fairly well detection limits for feldspar are around 5 and plagioclase composition can be determined within error margins of 4 anorthite component infrared spectroscopy can however not detect compositional zonation or different generations of feldspars infrared spectra represent the current average plagioclase and average alkali feldspar composition in the sample with several new airborne instruments under development it is opportune to focus upcoming research efforts on developing standardized processing techniques and spectral feldspar indices for thermal infrared imagery commercially interesting products include numbers of feldspars species plagioclase and alkali feldspar composition their structural state and relative or semi quantitative abundance in the rocks

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

quantitative compositional analysis using thermal emission spectroscopy application to igneous and metamorphic rocks the mineral composition of a suite of igneous and metamorphic rocks was determined using the thermal infrared emission spectra of these rocks in a linear spectral deconvolution algorithm this algorithm assumes that the infrared spectrum of each rock is a linear mixture of the component mineral spectra weighted by volume abundance a diverse suite of 36 common rock forming and accessory minerals was used in the deconvolution the model was tested by comparing the mineralogy derived from the infrared spectrum with petrographically estimated abundances for 45 igneous and 51 metamorphic rock samples the mineral abundances derived from these two techniques agree to within 67 15 for the primary minerals feldspar pyroxene quartz and calcite dolomite and 69 17 for secondary minerals such as micas and amphiboles these differences are comparable to the error for traditional thin section mode estimates which are 65 15 for major minerals and 5 for minor minerals the detection limit for the primary and secondary minerals found in the rocks analyzed ranged from 5 to 10 each major rock type studied here was easily distinguished by its spectral characteristics the best results in both the qualitative determination of the rock type and dominant minerals and the quantitative reproduction of absorption features and mineral composition were obtained for igneous rock samples for metamorphic rocks pelite and quartzo feldspathic samples gave slightly better results than calcareous or mafic samples a controlled analysis in which the end member suite was reduced based on an initial estimate of the rock type only improved the results by several percent for most primary and secondary minerals the quality of the obtained results demonstrates that a linear deconvolution of infrared emission spectra provides an accurate rapid technique for determining the quantitative mineral composition of rock samples in a laboratory and has application to future in situ measurements

thermal infrared remote sensing and kirchhoff s law 1 laboratory measurements by the end of this century the earth observing system eos will provide worldwide thermal infrared multispectral images of the earth presenting geologists with a new kind of remote sensing data for interpretation thus it has become essential to understand the spectral emittance behavior of terrestrial surface materials perhaps the most fundamental question to be answereed is the extent to which such materials follow kirchhoff s law epsilon 1 r under laboratory and field conditions especially when a sample displays a thermal gradient we present the first rigorous quantitative comparison of directional and hemispherical reflectance and directional emittance of rock and soil samples in the laboratory with thermal gradients induced by heating them from below and allowing them to radiate to a colder background the results show that only an extemeley low density sample composed of fine particles sifted into a fairy castle structure displays a thermal gradient steep enough within the infrared skin depth to cause significant 6 departure from kirchhoff s law there is no detectable effect on the more normal terrestrial samples such as soils and rocks measured in the laboratory even when semitransparent coatings are involved thus both emittance and reflectance measurements can be used to calculate sample emissivity for most terrestrial surface materieals however the effect on kirchhoffian behavior of different field environments which may induce a steeper thermal gradient in particulate samples has yet to be determined and some low density surface materials like newly fallen snow frost and efflorescent salts on playas have yet to be measured in emittance

plagioclase compositions derived from thermal emission spectra of compositionally complex mixtures implications for martian feldspar mineralogy 1 the compositions of plagioclase the most abundant mineral in the martian crust reflect changing conditions during magmatic evolution plagioclase contains spectral features at thermal infrared wavelengths that permit its detection by thermal emission spectrometers thermal emission spectrometer tes thermal emission imaging system themis and miniature tes mini tes on mars spacecraft previous studies have determined the accuracy with which average plagioclase compositions can be modeled in simple two component sand mixtures and terrestrial volcanic rocks studies of terrestrial rock analogs suffer from difficulties in accurately determining the average plagioclase composition for comparison with the spectrally modeled composition sand mixtures however provide a means of controlling plagioclase compositions for direct comparison to those modeled by linear deconvolution this has allowed us to address how compositional complexity may affect our ability to derive average plagioclase compositions from thermal emission data in this study we examine the accuracy with which average plagioclase compositions can be modeled from emission spectra of complex mixtures of three four and five compositions of coarse 500 850 m plagioclase sand additionally we examine multiphase mixtures of plagioclase with pyroxene olivine magnetite and ilmenite that are analogous to selected martian surface materials increasing the number of plagioclase compositions or introducing additional mineral phases does not affect the accuracy previously reported for modeling average plagioclase compositions plagioclase can be modeled to within 6 an of measured compositions at laboratory tes themis and mini tes resolution within 1 standard deviation

sebass hyperspectral thermal infrared data surface emissivity measurement and mineral mapping this study focuses on mapping surface minerals using a new hyperspectral thermal infrared tir sensor the spatially enhanced broadband array spectrograph system sebass sebass measures radiance in 128 contiguous spectral channels in the 7 5 to 13 5 m region with a ground spatial resolution of 2 m in september 1999 three sebass flight lines were acquired over virginia city and steamboat springs nevada at sensor data were corrected for atmospheric effects using an empirical method that derives the atmospheric characteristics from the scene itself rather than relying on a predicted model the apparent surface radiance data were reduced to surface emissivity using an emissivity normalization technique to remove the effects of temperature mineral maps were created with a pixel classification routine based on matching instrument and laboratory measured emissivity spectra similar to methods used for other hyperspectral data sets e g aviris linear mixtures of library spectra match sebass spectra reasonably well and silicate and sulfate minerals mapped remotely agree with the dominant minerals identified with laboratory x ray powder diffraction and spectroscopic analyses of field samples though improvements in instrument calibration atmospheric correction and information extraction would improve the ability to map more pixels these hyperspectral tir data nevertheless show significant advancement over multispectral thermal imaging by mapping surface materials and lithologic units with subtle spectral differences in mineralogy

mineralogy at meridiani planum from the mini tes experiment on the opportunity rover the miniature thermal emission spectrometer mini tes on opportunity investigated the mineral abundances and compositions of outcrops rocks and soils at meridiani planum coarse crystalline hematite and olivine rich basaltic sands were observed as predicted from orbital tes spectroscopy outcrops of aqueous origin are composed of 15 to 35 by volume magnesium and calcium sulfates a high silica component modeled as a combination of glass feldspar and sheet silicates 20 to 30 and hematite only minor jarosite is identified in mini tes spectra mini tes spectra show only a hematite signature in the millimeter sized spherules basaltic materials have more plagioclase than pyroxene contain olivine and are similar in inferred mineral composition to basalt mapped from orbit bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites bright wind streak material matches global dust waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering

first use of an airborne thermal infrared hyperspectral scanner for compositional mapping in may 1999 the airborne thermal infrared hyperspectral imaging system spatially enhanced broadband array spectrograph system sebass was flown over mormon mesa nv to provide the first test of such a system for geological mapping several types of carbonate deposits were identified using the 11 25 m band however massive calcrete outcrops exhibited weak spectral contrast which was confirmed by field and laboratory measurements because the weathered calcrete surface appeared relatively smooth in hand specimen this weak spectral contrast was unexpected here we show that microscopic roughness not readily apparent to the eye has introduced both a cavity effect and volume scattering to reduce spectral contrast the macroroughness of crevices and cobbles may also have a significant cavity effect the diminished spectral contrast is important because it places higher signal to noise ratio snr requirements for spectroscopic detection and identification this effect should be factored into instrumentation planning and interpretations especially interpretations without benefit of ground truth sebass had the required high snr and spectral resolution to allow us to demonstrate for the first time the ability of an airborne hyperspectral thermal infrared scanner to detect and identify spectrally subtle materials

the aster spectral library version 2 0 abstract the advanced spaceborne thermal emission reflection radiometer aster on nasa s terra platform has been widely used in geological and other science studies in support of aster studies a library of natural and man made materials was compiled as the aster spectral library v1 2 and made available from http speclib jpl nasa gov the library is a collection of contributions in a standard format with ancillary data from the jet propulsion laboratory jpl johns hopkins university jhu and the united states geological survey usgs a new version of the library v2 0 is now available online or via cd which includes major additions to the mineral and rock spectra the aster library provides a comprehensive collection of over 2300 spectra of a wide variety of materials covering the wavelength range 0 4 15 4 m

composition and thermal inertia of the mawrth vallis region of mars from tes and themis data abstract clay mineral bearing deposits previously discovered on mars with near infrared 0 3 5 m remote sensing data are of major significance for understanding the aqueous history geological evolution and past habitability of mars in this study we analyzed the thermal infrared 6 35 m surface properties of the most extensive phyllosilicate deposit on mars the mawrth vallis area clay mineral bearing units which in visible images appear to be relatively light toned layered bedrock have thermal inertia values ranging from 150 to 460 j m 2 k 1 s 1 2 this suggests the deposits are composed of a mixture of rock with sand and dust at 100 meter scales dark toned materials that mantle the clay bearing surfaces have thermal inertia values ranging from 150 to 800 indicating variable degrees of rockiness or induration of this younger sedimentary or pyroclastic unit thermal emission spectrometer tes spectra of the light toned rocks were analyzed with a number of techniques but none of the results shows a large phyllosilicate component as has been detected in the same surfaces with near infrared data instead tes spectra of light toned surfaces are best modeled by a combination of plagioclase feldspar high silica materials similar to impure opaline silica or felsic glass and zeolites we propose three hypotheses for why the clay minerals are not apparent in thermal infrared data including effects due to surface roughness sub pixel mixing of multiple surface temperatures and low absolute mineral abundances combined with differences in spatial sampling between instruments zeolites modeled in tes spectra could be a previously unrecognized component of the alteration assemblage in the phyllosilicate bearing rocks of the mawrth vallis area tes spectral index mapping suggests that fe mg clays detected with near infrared data correspond to trioctahedral fe2 clay minerals rather than nontronite like clays the average mineralogy and geologic context of these complex interbedded deposits suggests they are either aqueous sedimentary rocks altered pyroclastic deposits or a combination of both

numerical simulation of rayleigh taylor instability for single and multiple salt diapirs abstract the diapiric ascent of light rocks through a denser oberburden is simulated using a new numerical method based in part on finite differences rocks are modelled as viscous newtonian liquids and the internal interfaces are located with the help of passive markers these markers are relocated using a new algorithm equivalent to a cellular automaton rule this allows the markers to be redistributed very rapidly this new method appears to be well adapted to quickly resolving geological problems simulations of the growth of a single dome are performed under various viscosity ratios for the salt and the overburden the effect of asymmetrical initial deformations of the salt layer is to produce diapiric structures that slowly return to symmetry as the diapir matures and rises in an isotropic medium simulations involving continuous sedimentation of the overburden are also performed an initial geometry on a basin margin in which multiple diapirs eventually develop is studied diapirs grow relatively rapidly near the centre while on the margins the salt layer flows upward following the basement simulations with salt that is more viscous than sediments show the development of previously unnoticed asymmetrical structures

numerical modelling of the displacement and deformation of embedded rock bodies during salt tectonics a case study from the south oman salt basin large rock inclusions are embedded in many salt bodies and these respond to the move ments of the salt in a variety of ways including displacement folding and fracturing one mode of salt tectonics is downbuilding whereby the top of a developing diapir remains in the same vertical position while the surrounding overburden sediments subside we investigate how the differential displacementofthe top saltsurface causedbydownbuilding inducesductilesaltflowand the associ ated deformation of brittle stringers by an iterative procedure to detect and simulate conditions for the onset of localization of deformation in a finite element model in combination with adaptive remeshing the model set up is constrained by observations from the south oman salt basin where large carbonate bodies encased in salt form substantial hydrocarbon plays the model shows that depending on the displacement of the top salt the stringers can break very soon after the onset of salt tectonics and can deform in different ways if extension along the inclusion dom inates stringersarebrokenbytensilefracturesandboudinageatrelativelyshallowdepth spacingof the boudin bounding faults can be as close as 3 4 times the thickness of the stringer in contrast salt shortening along the inclusion may lead to folding or thrusting of stringers

selection of hyspiri optimal band positions for the earth compositional mapping using hytes data abstract the national aeronautics and space administration nasa has proposed the launch of a new space borne sensor called hyspiri hyperspectral and infrared imager which will cover the spectral range from 0 4 12 m two instruments will be mounted on hyspiri platform 1 a hyperspectral instrument which can sense earth surface between 0 4 and 2 5 m at 10 nm intervals and 2 a multispectral infrared sensor will acquire images between 3 and 12 m in eight spectral bands one in mid infrared mir and seven in thermal infrared tir the tir spectral wavebands will be positioned based on their importance in various applications this study aimed to identify hyspiri optimal tir wavebands position for earth compositional mapping a genetic algorithm coupled with the spectral angle mapper ga sam was used as a spectral bands selector high dimensional hytes hyperspectral thermal emission spectrometer emissivity spectra comprised of 202 spectral bands of cuprite and death valley regions were used to select meaningful subsets of bands for earth compositional mapping the ga sam was trained for fifteen mineral classes and the algorithms were run iteratively 50 times high calibration 95 and validation 90 accuracies were achieved with a limited number seven of spectral bands selected by ga sam the knowledge of important band positions will help the scientists of the hyspiri group to place spectral bands in regions where accuracies of earth compositional mapping can be enhanced

infrared reflectance spectra 2 2 15 μm of plagioclase feldspars laboratory results show that 1 the christiansen frequency cf feature in mid infrared reflectance spectra of powders can be used to accurately distinguish plagioclase composition and 2 the wavelength position of the cf is not affected by vitrification of the plagioclase although the cf position does not distinguish glass from crystalline forms of plagioclase other features combination tone overtone restrahlen bands in the mid ir spectra of plagioclase can be used for that purpose these results have important implications for application of thermal emission spectroscopy to mapping the surface composition of regolith covered planetary bodies like the moon mars and asteroids

identification of sand sources and transport pathways at the kelso dunes california using thermal infrared remote sensing the kelso dune field is located in the eastern mojave desert california at the terminus of a sand transport pathway which has its primary source at the mojave river wash 50 km to the west initial examination of 1984 airborne thermal infrared multispectral scanner tims data showed significant spectral variations that indicate potential mineralogic heterogeneities within the active dunes this result prompted the collection of a suite of 48 sand samples in 1990 and the acquiring of new tims data in 1995 this new data set was used to test a newly developed linear spectral retrieval algorithm in conjunction with a spectral library of end member minerals results of this analysis produced images of end member minerals that showed marked variations within the dunes in addition standard petrographic techniques revealed that the dunes contain mineralogic variations and were much less quartz rich 42 than previously reported 70 90 point count results agreed with the spectral data to within an average of 5 3 for tims derived and 3 1 for laboratory derived mineralogic abundances high concentrations of several of the end member minerals on the surrounding alluvial fans indicate a potential nearby source for these minerals most evident is the presence of potassium feldspar from the fan that emanates from the providence mountains east of the dunes this previously unidentified potential sand input is not visible with other remote sensing techniques and was confirmed with additional field sampling much of the quartz and some plagioclase feldspar however appear to have been transported from the mojave river wash source as previously reported this study also validates the potential of using thermal remote sensing from future satellite based instruments to globally monitor desert fringe areas susceptible to the changing conditions of sand encroachment