geochemical constraints on the origin of calcite veins and associated limestone alteration ordovician viola group arbuckle mountains oklahoma u s a abstract isotopic and elemental analyses constrain the origins of two types of calcite veins and associated limestone alteration in the ordovician viola group arbuckle mountains oklahoma u s a calcite from small millimeter wide veins has similar 87 sr 86 sr ratios 0 70781 0 70792 and 13c values 1 4 to 1 6 pdb to host viola limestone 87 sr 86 sr 0 70779 0 70794 13c 2 2 to 1 7 pdb indicating that the fluids from which the vein calcite precipitated were chemically buffered by the host limestone the low 18o values 8 2 to 5 5 pdb of the vein calcite relative to the host limestone 5 0 to 3 1 pdb suggest that the vein calcite probably precipitated from 18o depleted meteoric water calcite from large veins 5 50 cm wide is characterized by radiogenic 87 sr 86 sr ratios 0 70887 0 70915 and low 13c values 8 0 to 2 5 pdb relative to host viola limestone such isotopic compositions demonstrate that the fluids responsible for the formation of the large veins were enriched in 87sr and depleted in 13c relative to the host limestone the 18o values 4 8 to 3 7 pdb of calcite from the large veins coupled with the presence of hot 50 90 c and saline fluid inclusions constrain the formation of the vein calcite to 18o enriched 18 o 2 smow fluids on this basis calcite from the large veins is believed to have precipitated from basin derived fluids adjacent to the large veins alteration zones up to 0 5 m wide have developed in host limestone relative to other limestones the altered limestones display radiogenic 87 sr 86 sr ratios 0 70792 0 70880 low 13c values 8 2 to 2 0 pdb and low sr concentrations the similar isotopic compositions of the altered limestone to those of the large veins suggest that alteration of limestones was also caused by basinal fluids

chemistry and petrography of calcite in the ktb pilot borehole bavarian oberpfalz germany the ktb kontinentales tiefbohrprogramm der bundesrepublik deutschland pilot borehole in northeast bavaria germany penetrates 4000 m of gneiss amphibolite and subordinate calc silicate lamprophyre and metagabbro there are three types of calcite in the drilled section 1 metamorphic calcite in calc silicate and marble 2 crack filling calcite in all lithologies and 3 replacement calcite in altered minerals crack filling and replacement calcite postdate metamorphic calcite multiple calcite generations in individual cracks suggest that different generations of water repeatedly flowed through the same cracks cracks that eventually filled with calcite carried water to sites where replacement calcite formed by plagioclase hydrolysis or other decarbonation reactions whole rock contents of all three calcite types range from 35 wt in near surface calc silicate to 0 1 wt in amphibolite with calcite filled cracks at 3872 m calcite contains average sr concentrations of 180 ppm and mn concentrations of 3980 ppm crack filling calcite microdrilled from thin sections has average 13c 9 0 2 2 and 18o 10 5 1 5 values are 1 standard deviation crack filling mineral assemblages that include calcite originally formed at temperatures of 150 350 c presently crack filling calcite is in chemical and isotopic equilibrium with saline to brackish water in the borehole at temperatures of 120 c the saline to brackish water contains a significant proportion of meteoric water re equilibration of crack filling calcite to lower temperatures means that calcite chemistry tells us little about water rock interactions in the crustal section at temperatures higher than 120 c

oman exotics oceanic carbonate build ups associated with the early stages of continental rifting the so called oman exotic limestones form isolated masses from boulder size to 1 000 m thick of middle to upper permian and upper triassic fossiliferous limestones and crop out within imbricated thrust slices beneath the semail ophiolite in the oman mountains permian exotics are of dominantly reef and forereef facies whereas triassic exotics are more typically of back reef and lagoonal facies they are commonly associated with a substrate of alkalic and transitional tholeiitic basalts and are interpreted as a series of reef associated carbonate buildups deposited in part on oceanic islands or seamounts close to the site of initial rifting of the oman continental margin

mapping of muslim bagh ophiolite complex pakistan using new remote sensing and field data abstract tethys is a relational gis database that combines geophysical remote sensing geochemical and geochronological data developed as a flexible resource for studying magmatic and geodynamic responses to continental collisions in this paper we demonstrate utility of our database by integrating field remote sensing and structural data for detailed mapping and tectonic emplacement of muslim bagh ophiolite of western pakistan this ophiolite forms the uppermost part of a nappe pile which accreted onto the indian continental margin during the closure of the neo tethys during a pre terminal collision that predated the final closure of tethys during the major collision between india and eurasia utilizing the tethys landsat aster imagery and a digital elevation model developed from the aster data are used to characterize the lithology and structure of the area use of image processing techniques improved the geologic map of the area for a better understanding of the tectonic emplacement of the muslim bagh ophiolite for the first time we report that the dikes in the muslim bagh ophiolite are cutting the metamorphic sole our preliminary geochemical data for sheeted dike complex suggest chemical affinities with arc related rocks this observation suggests that dikes were intruded in an island arc environment soon after the ophiolite was formed

introducing a terrestrial carbon pool in warm desert bedrock mountains southwestern usa growth of the phoenix metropolitan area led to road cut or house platform exposures of the internal bedrock material of surrounding semiarid mountain ranges similar exposures in the surrounding sonoran and mojave deserts reveal the presence of sedimentary calcium carbonate infilling the preexisting fracture matrix of the bedrock field surveys at 31 sites with bedrock fractures filled with carbonate referred to as bffc in the following text reveal an average of 0 079 0 036 mtc m2 stored in the upper 2 m of analyzed bedrock exposures backscattered electron microscopy images indicate the presence of carbonate at the micron scale not included in this estimate of carbon storage pilot radiocarbon and sr isotope analyses suggest that one of the surveyed bffc veins was flushed into the bedrock from a nonbedrock source during the wetter last glacial period in the late pleistocene

detection of hydrothermal mineralized zones associated with listwaenites in central oman using aster data abstract listwaenites are highly altered ultramafic rocks that are potentially associated with economic mineralization and research on these is extremely important worldwide in the present study the classification of mineralized listwaenites developed along the serpentinite amphibolite interface of the semail ophiolite its associated lithology and the zones of alteration and mineralization in the fanjah saddle of the central oman mountains region of the sultanate of oman are carried out using advanced spaceborne thermal emission and reflection radiometer aster satellite data the developed band ratioing principal component analysis pca and the spectral angle mapper sam supervised classification and image processing techniques applied on the aster data set have proved their capability for better interpretation and identification of hydrothermally altered rocks and associated mineralization the hyperspectral tools minimum noise fraction mnf pixel purity index ppi and nd visualizer extracted end member spectra and sam classification clearly show the occurrence of minerals and their spatial distributions the promising results are verified and confirmed in the field by identification of alteration and mineralization such as listwaenites silicification serpentinization and talc alteration and are validated further through laboratory analysis the confirmation of the occurrence of base metal mineralization along the serpentinite amphibolite interface in listwaenites suggests that detailed investigation in this and other arid regions which have similar geological conditions may locate mineral deposits the hyperspectral tools applied on aster satellite data show that these can be used as a powerful tool to explore the listwaenites and the potential associated mineralization in other arid geographical regions worldwide

traces of epigenetic hydrothermal activity at yucca mountain nevada preliminary data on the fluid inclusion and stable isotope evidence samples of opal quartz calcite crusts from the 7 8 km long tunnel excavated under yucca mountain were studied to determine their origin calcite in these crusts commonly forms relatively large up to 1 5 cm euhedral crystal terminations in some crusts layers of chalcedony and patches of opal alternate with calcite layers chalcedony commonly grades into euhedral quartz crystals quartz also forms microdruses of individual crystals up to 8 mm in size fluorite was identified in four samples fluid inclusion studies on calcite revealed formation temperatures of 35 85 c gas filled inclusions are apparently of low density p 1 bar at room temperature and contain aromatic hydrocarbons in four studied calcite samples values of 18o remain virtually constant across crusts 10 6 to 12 1 v pdb in one sample the earliest part of calcite had 18o of 19 in this part of the sample the highest fluid inclusion temperatures 70 85 c were measured the secondary calcite found at yucca mountain is commonly interpreted as being formed through a pedogenic process from rain waters percolating in the vadose zone and carrying dissolved carbonate from overlying soils e g stuckless j s peterman z e muchs d r 1991 u and sr isotopes in ground water and calcite yucca mountain nevada evidence against upwelling water science 254 551 554 nas nrc 1992 ground water at yucca mountain how high can it rise national academy press washington dc roedder e whelan j f vaniman d t 1994 fluid inclusion studies of calcite veins from yucca mountain nevada tuffs environment of formation high level radioactive waste management proc int conf am nucl soc la grande park il pp 1854 1860 our data indicate that the calcite opal quartz with minor fluorite crusts from the presently unsaturated vadose zone of yucca mountain were formed from low temperature hydrothermal aqueous fluids in the saturated phreatic environment the issue has direct bearing on the suitability of yucca mountain as a site for permanent geological disposal of the high level nuclear waste

paleotransport of lanthanides and strontium recorded in calcite compositions from tuffs at yucca mountain nevada usa secondary calcite occurs in both saturated and unsaturated hydrologic zones sz and uz respectively in the tuffs at yucca mountain nevada usa in the upper uz the major constituents of the calcite crystal structure c o have surface origins at greater depth there is a barren zone straddling the water table where calcite is rare and mixing of surface and subsurface sources may occur deep in the sz distinctive mn calcites reflect deep sources including ca released as analcime or albite formed and carbonates derived from underlying paleozoic rocks in the uz and in the barren zone above the deep mn calcites variations in calcite lanthanide chemistry can be used to distinguish rhyolitic from quartz latitic sources lanthanide ratios and sr contents of calcites record the chemical evolution of waters flowing through the uz and upper sz variations in calcite chemistry in the uz and in the barren zone show that 1 sr which is readily exchanged with clays or zeolites is essentially removed from some flowpaths that are in contact with these minerals and 2 traces of mn oxides found in the tuffs have a significant effect on groundwater chemistry in the uz and in the barren zone by removing almost all ce from solution evidenced by characteristic ce depletions in calcite throughout this zone extreme ce removal may be a result of ce oxidation ce 3 ce 4 at the surfaces of some mn oxides particularly rancieite higher sr contents and lack of ce depletions in the deeper mn calcites reflect different ages origins and transport systems the calcite record of lanthanide and sr transport in the uz shows that minor minerals clays and zeolites and even trace minerals mn oxides will affect the compositions of groundwaters that flow over distances greater than a few tens of meters

overview of calcite opal deposits at or near the proposed high level nuclear waste site yucca mountain nevada usa pedogenic hypogene or both calcite opal deposits cod at yucca mountain were studied with respect to their regional and field geology petrology and petrography chemistry and isotopic geochemistry and fluid inclusions they were also compared with true pedogenic deposits tpd groundwater spring deposits gsd and calcite vein deposits cvd in the subsurface some of the data are equivocal and can support either a hypogene or pedogenic origin for these deposits however sr c and o isotope fluid inclusion and other data favor a hypogene interpretation a hypothesis that may account for all currently available data is that the cod precipitated from warm co2 rich water that episodically upwelled along faults during the pleistocene and which upon reaching the surface flowed downslope within existing alluvial colluvial eluvial or soil deposits being formed near or on the topographic surface the cod acquired characteristics of pedogenic deposits this subject relates to the suitability of yucca mountain as a high level nuclear waste site

ages and stable isotope compositions of secondary calcite and opal in drill cores from tertiary volcanic rocks of the yucca mountain area nevada stable isotope compositions of fracture and cavity filling calcite from the unsaturated zone of three drill cores at yucca mountain tertiary volcanic complex indicate that the water from which the minerals precipitated was probably meteoric in origin a decrease in 18 o in the calcite with depth is interpreted as being due to the increase in temperature in drill holes corresponding to an estimated average geothermal gradient of 34 per kilometer a few of the calcite samples and all of the opal samples yielded uranium series ages older than 400 000 yr although most of the calcite samples yielded ages between 26 000 and 310 000 yr the stable isotope and uranium series dates from precipitated calcite and opal of this reconnaissance study suggest a complex history of fluid movement through the volcanic pile and episodes of fracture filling predominantly from meteoric water during at least the past 400 000 yr

silver base metal epithermal vein and listwaenite types of deposit crnac rogozna mts kosovo part i ore mineral geochemistry and sulfur isotope study abstract pb zn ag vein and listwaenite types of mineralization in crnac deposit western vardar zone were deposited within several stages i the pre ore stage comprises pyrite arsenopyrite pyrrhotite quartz kaolinite and is followed by magnetite pyrite ii the syn ore stage is composed of galena sphalerite tetrahedrite and stefanite and iii the post ore stage is composed of carbonates pyrite arsenopyrite and minor galena the vein type mineralization is hosted by jurassic amphibolites and veins terminate within overlying serpentinites mineralized listwaenites are developed along the serpentinite amphibolite interface the reserves are estimated to 1 7 mt of ore containing in average 7 6 lead 2 9 zinc and 102 g t silver sulfides from the pre and syn mineralization assemblage of the vein and listwaenite types of mineralization from the crnac pb zn ag deposit have been analyzed using microprobe crush leachates and sulfur isotopes the pre ore assemblage precipitated under high sulfur fugacities f s 2 10 8 10 6 bar from temperatures ranging between 350 c and 380 c most likely water rock reactions boiling and or increase of ph caused an increase of 34 s of pyrite toward upper levels within the deposit the decomposition of pre ore pyrrhotite to a pyrite magnetite mixture occurred at a fugacity of sulfur from f s 2 8 7 10 10 to 9 6 10 9 bar and fugacity of oxygen from f o 2 2 4 10 30 to 3 1 10 28 bars indicating a contribution of an oxidizing fluid i e meteoric water during pre ore stages of hydrothermal activity the crystallization temperatures obtained by the sphalerite galena isotope geothermometer range from 230 to 310 c the 34 s values of pre and syn ore sulfides pyrite galena sphalerite 34 s 0 3 5 9 point to magmatic sulfur values of 34 s of galena and sphalerite are decreasing upwards due to precipitation of early formed sulfide minerals post ore assemblage precipitated at temperature below 190 c based on data presented above we assume two fluid sources i a magmatic source supported by sulfur isotopic compositions within pre and syn ore minerals and a high mol of fluorine found within pre and syn ore leachates and ii a meteoric source deduced by coincident pyrite magnetite intergrowth sulfur isotopic trends within syn ore minerals and decrease of crystallization temperatures from the pre ore stage 380 350 c towards the syn ore 310 215 c and post ore stages

the distribution and discrimination of shallow authigenic carbonate in the pliocene pleistocene palomas basin southern rio grande rift nine types of authigenic carbonate are present in the pliocene pleistocene alluvial fan and axial fluvial sediment of the palomas half graben in the southern rio grande rift pedogenic and other vadose carbonate includes 1 pedogenic carbonate of stage ii and stage iii morphology underlying bw and bt horizons 2 mudstones in which the carbonate nodules may be pedogenic or the result of shallow groundwater invasion of the vadose zone 3 pedogenic calcic nodules and tubules in eolian sand and 4 gully bed cement of proximal fan conglomerates formed by infiltration and evaporation of surface runoff shallow groundwater carbonate exists as 5 thin 30 50 cm massive beds with an upper fringe of nodules and tubules precipitated at the water table and in the capillary fringe 6 thick 1 5 3 m massive beds deposited by lateral flow of groundwater or at springs and 7 thin 30 cm calcified root mats associated with near surface water saturated sediment or springs phreatic spar cements 8 occupy the interstices of conglomerates and sandstones and locally exist as 9 oriented concretions groundwater carbonates are best developed near the toes of the large hanging wall derived alluvial fans whereas phreatic cement preferentially exists in footwall derived alluvial fan conglomerates pedogenic carbonate is distinguished from groundwater carbonate by the association with other diagnostic paleosol horizons a predominantly vertical arrangement of root traces peds desiccation cracks and calcic tubules and by gradational contacts the 13 c and 18 o values are similar among pedogenic and shallow groundwater carbonate although locally nodules in eolian sand and gully bed cement have higher 18 o values perhaps due to the effects of evaporation some phreatic cements may be distinguished from pedogenic and shallow groundwater carbonate by lower values of 13 c and 18 o authigenic carbonate in footwall derived alluvial fan sediment has consistently higher values of 13 c than that in hanging wall derived sediment which may reflect differences in vegetative type and or density on either side of the basin

mapping of moho and moho transition zone mtz in samail ophiolites of sultanate of oman using remote sensing technique abstract moho and moho transition zone mtz of the samail ophiolite of sultanate of oman are characteristic to potential occurrences of chromite deposit hydrothermal mineralization and serpentinization mapping of moho and mtz and discriminating them in between the mafic and ultramafic rocks in ophiolite sequence are more significant and important the present study describes the remote sensing spectral characters of minerals and rocks of the moho and mtz and discriminates the moho of wadi al abyad of nakhl massif and wadi nidab and wadi abda regions of sumail massif in the visible and near infrared vnir and short wavelength infrared swir spectral regions using low cost multispectral satellite data of the advanced spaceborne thermal emission and reflection radiometer aster results of this study show that the red green blue rgb color composite images of aster spectral bands 8 3 and 1 and 8 7 and 4 are able to delineate the moho and mtz of the regions the rgb images of aster band ratios 4 8 4 1 3 2 4 3 and 1 3 2 4 6 5 7 9 8 are capable to discriminate the mantle material ultramafic harzburgites and crustal rocks mafic gabbros the occurrence of such rock types is demonstrated by detection of their minerals using spectral angle mapper sam image processing method the presence of moho and mtz and associated lithologies are verified in field at wadi al abyad wadi nidab wadi abda wadi tayin wadi fizh and several locations of nakhl regions of samail ophiolites the laboratory study shows the occurrence of typical minerals namely olivine orthopyroxene and clinopyroxene in the harzburgite and the minerals such as plagioclase clinopyroxene hornblende orthopyroxene and olivine in the layered gabbro the spectral properties of the rocks are studied using portable infrared mineral analyzer pima spectrometer and the occurrences of minerals are confirmed by x ray diffraction xrd analyses this study demonstrates the sensor capability of aster to map moho and mtz and thus it is recommended to the geoscientists and geophysicists working on moho and mtz the satellite image interpretations of moho and mtz and the associated rocks and minerals are consistent with the field research studies carried out in these regions our images have potential to map the chromites mineralized zone and dunites refractory materials bearing mtz

evidence for a hypogene paleohydrogeological event at the prospective nuclear waste disposal site yucca mountain nevada usa revealed by the isotope composition of fluid inclusion water abstract secondary calcite residing in open cavities in the unsaturated zone of yucca mountain has long been interpreted as the result of downward infiltration of meteoric water through open fractures in order to obtain information on the isotopic composition d and 18 o of the mineral forming water we studied fluid inclusions from this calcite water was extracted from inclusions by heated crushing and the d values were measured using a continuous flow isotope ratio mass spectrometry method the 18 o values were calculated from the 18 o values of the host calcite assuming isotopic equilibrium at the temperature of formation determined by fluid inclusion microthermometry the d values measured in all samples range between 110 and 90 similar to holocene meteoric water coupled 18 o d values plot significantly 2 to 8 to the right of the meteoric water line among the various processes operating at the topographic surface and or in the unsaturated zone only two processes evaporation and water rock exchange could alter the isotope composition of percolating water our analysis indicates however that none of these processes could produce the observed large positive 18 o shifts the latter require isotopic interaction between mineral forming fluid and host rock at elevated temperature 100 c which is only possible in the deep seated hydrothermal environment the stable isotope data are difficult to reconcile with a meteoric origin of the water from which the secondary minerals at yucca mountain precipitated instead they point to the deep seated provenance of the mineral forming waters and their introduction into the unsaturated zone from below i e a hypogene origin

evolution of the conceptual model of unsaturated zone hydrology at yucca mountain nevada abstract yucca mountain is an arid site proposed for consideration as the united states first underground high level radioactive waste repository low rainfall approximately 170 mm yr and a thick unsaturated zone 500 1000 m are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment the framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr early conceptual models assumed that very small volumes of water infiltrated into the bedrock 0 5 4 5 mm yr or 2 3 percent of rainfall that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded fractured rocks it was believed that the matrix had to be saturated for fractures to flow however accumulating evidence indicated that infiltration rates were higher than initially estimated such as infiltration modeling based on neutron borehole data bomb pulse isotopes deep in the mountain perched water analyses and thermal analyses mechanisms supporting lateral diversion did not apply at these higher fluxes and the flux calculated in the lower welded unit exceeded the conductivity of the matrix implying vertical flow of water in the high permeability fractures of the potential repository host rock and disequilibrium between matrix and fracture water potentials the development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data particularly fracture flow deep in the unsaturated zone this paper presents the history of the evolution of conceptual models of hydrology and numerical models of unsaturated zone flow at yucca mountain nevada flint a l flint l e kwicklis e m bodvarsson g s fabryka martin j m 2001 hydrology of yucca mountain reviews of geophysics in press this retrospective is the basis for recommendations for optimizing the efficiency with which a viable and robust conceptual model can be developed for a complex site

uranium rich opal from the nopal i uranium deposit pena blanca mexico evidence for the uptake and retardation of radionuclides abstract the nopal i uranium deposit of the sierra pena blanca mexico has been the focus of numerous studies because of its economic importance and its use as a natural analog for nuclear waste disposal in volcanic tuff secondary uranyl minerals such as uranophane ca uo2 sio3oh 2 h2o 5 and weeksite k na 2 uo2 2 si5o13 h2o 3 occur in the vadose zone of the deposit and are overgrown by silica glaze these glazes consist mainly of opal a which contains small particles of uraninite uo2 and weeksite close to a fault between brecciated volcanic rocks and welded tuff a greenish silica glaze coats the altered breccia yellow silica glazes from the center of the breccia pipe and from the high grade pile coat uranyl silicates predominantly uranophane and weeksite all silica glazes are strongly zoned with respect to u and ca and the distribution of these elements indicates curved features and spherical particles inside the coatings the concentrations of u and ca correlate in the different zones and both elements inversely correlate with the concentration of si zones within the silica glazes contain u and ca in a 1 1 ratio with maximum concentrations of 0 08 and 0 15 at for the greenish and yellow glazes respectively suggesting trapping of either ca1u1 aqueous species or particles in the colloidal silica x ray photoelectron spectroscopy xps fourier transform infra red spectroscopy ftir and oxygen isotope ratios measured by secondary ion mass spectrometry sims indicate higher u6 u4 ratios higher proportions of si oh groups and lower 18o values for the greenish silica glaze than for the yellow silica glaze these differences in composition reflect increasing brecciation porosity and permeability from the center of the breccia pipe yellow silica glaze toward the fault green silica glaze where the seepage of meteoric water and eh are higher

uranium bearing opals products of u mobilization diffusion and transformation processes understanding the retention mechanism of u by amorphous silica i e opal in the environment is of great importance to nuclear waste disposal because opals can retain u for millions of years uraniferous opals from spor mountain and the thomas range utah u s a are examined in terms of their mineralogical chemical and isotopic compositions uranium rich zones composed of most likely vorlanite cauo 4 occur in fibrous opal ct termed lussatite along the interface of the phase with microcrystalline quartz red to black colored precipitates of vorlanite also occur in the interstices between fibers and grains in lussatite and massy opals respectively the high abundance of vorlanite in certain growth zones can be explained by the diffusion of ca and u along boundaries of layers grains and fibers and by the release of ca and u through the transformation of opal a into opal ct and from opal ct into microcrystalline quartz similar o isotope compositions of opal ct and associated microcrystalline quartz indicate that crystallization processes and deposition of subsequent layers of opal occurred from fluids of similar origin and t differences in the isotope and chemical composition between uraniferous opals microcrystalline quartz the sio 2 polymorph moganite and pyrolusite indicate the past occurrence of various alteration processes involving fluids of different composition and t the results of this study indicate that assemblages of opal and microcrystalline quartz can retain u for millions of years as long as confined pore spaces between different generations of opal and quartz or between growth features of opal provide space for the nucleation and adsorption of u bearing phases and species

physical and stable isotope evidence for formation of secondary calcite and silica in the unsaturated zone yucca mountain nevada abstract calcite and silica form coatings on fracture footwalls and cavity floors in the welded tuffs at yucca mountain the potential site of a high level radioactive waste repository these secondary mineral deposits are heterogeneously distributed in the unsaturated zone uz with fewer than 10 of possible depositional sites mineralized the paragenetic sequence compiled from deposits throughout the uz consists of an early stage assemblage of calcite fluorite zeolites that is frequently capped by chalcedony quartz intermediate and late stage deposits consist largely of calcite commonly with opal on buried growth layers or outermost crystal faces of the calcite coatings on steep dipping fractures usually are thin 3 mm with low relief outer surfaces whereas shallow dipping fractures and lithophysal cavities typically contain thicker more coarsely crystalline deposits characterized by unusual thin tabular calcite blades up to several cms in length these blades may be capped with knobby or corniced overgrowths of late stage calcite intergrown with opal the observed textures in the fracture and cavity deposits are consistent with deposition from films of water fingering down fracture footwalls or drawn up faces of growing crystals by surface tension and evaporated at the crystal tips fluid inclusion studies have shown that most early stage and some intermediate stage calcite formed at temperatures of 35 to 85 c calcite deposition during the past several million years appears to have been at temperatures 18 o values although others have interpreted the elevated temperatures as evidence of hydrothermal activity and flooding of the tuffs of the potential repository the authors conclude that the temperatures and fluid inclusion assemblages are consistent with deposition in a uz environment that experienced prolonged heat input from gradual cooling of nearby plutons the physical restriction of the deposits and therefore fluid flow to fracture footwalls and cavity floors and the heterogeneous and limited distribution of the deposits provides compelling evidence that they do not reflect flooding of the thick uz at yucca mountain the textures and isotopic and chemical compositions of these mineral deposits are consistent with deposition in a uz setting from meteoric waters percolating downward along fracture flow paths

the application of remote sensing techniques to the study of ophiolites abstract satellite remote sensing methods are a powerful tool for detailed geologic analysis especially in inaccessible regions of the earth s surface short wave infrared swir bands are shown to provide spectral information bearing on the lithologic structural and geochemical character of rock bodies such as ophiolites allowing for a more comprehensive assessment of the lithologies present their stratigraphic relationships and geochemical character most remote sensing data are widely available for little or no cost along with user friendly software for non specialists in this paper we review common remote sensing systems and methods that allow for the discrimination of solid rock lithologic components of ophiolite complexes and their structural relationships ophiolites are enigmatic rock bodies which associated with most if not all plate collision sutures ophiolites are ideal for remote sensing given their widely recognized diversity of lithologic types and structural relationships accordingly as a basis for demonstrating the utility of remote sensing techniques we briefly review typical ophiolites in the tethyan tectonic belt as a case study we apply integrated remote sensing studies of a well studied example the muslim bagh ophiolite located in balochistan western pakistan on this basis we attempt to demonstrate how remote sensing data can validate and reconcile existing information obtained from field studies the lithologic and geochemical diversity of muslim bagh are representative of tethyan ophiolites despite it s remote location it has been extensively mapped and characterized by structural and geochemical studies and is virtually free of vegetative cover moreover integrating the remote sensing data with ground truth information thus offers the potential of an improved template for interpreting remote sensing data sets of other ophiolites for which little or no field information is available

thermal history of the unsaturated zone at yucca mountain nevada usa abstract secondary calcite silica and minor amounts of fluorite deposited in fractures and cavities record the chemistry temperatures and timing of past fluid movement in the unsaturated zone at yucca mountain nevada the proposed site of a high level radioactive waste repository the distribution and geochemistry of these deposits are consistent with low temperature precipitation from meteoric waters that infiltrated at the surface and percolated down through the unsaturated zone however the discovery of fluid inclusions in calcite with homogenization temperatures th up to 80 c was construed by some scientists as strong evidence for hydrothermal deposition this paper reports the results of investigations to test the hypothesis of hydrothermal deposition and to determine the temperature and timing of secondary mineral deposition mineral precipitation temperatures in the unsaturated zone are estimated from calcite and fluorite hosted fluid inclusions and calcite 18o values and depositional timing is constrained by the 207pb 235u ages of chalcedony or opal in the deposits fluid inclusion th from 50 samples of calcite and four samples of fluorite range from 35 to 90 c calcite 18o values range from 0 to 22 smow but most fall between 12 and 20 the highest th and the lowest 18o values are found in the older calcite calcite th and 18o values indicate that most calcite precipitated from water with 18o values between 13 and 7 similar to modern meteoric waters twenty two 207pb 235u ages of chalcedony or opal that generally postdate elevated depositional temperatures range from 9 5 to 1 9 ma new and published 207pb 235u and 230th uages coupled with the th values and estimates of temperature from calcite 18o values indicate that maximum unsaturated zone temperatures probably predate 10 ma and that the unsaturated zone had cooled to near present day temperatures 24 26 c at a depth of 250 m by 2 4 ma the evidence of elevated temperatures persisting in ash flow tuffs adjacent to parent calderas for as much as 8 ma is a new finding but consistent with thermal modeling simulations using the heat code demonstrate that prolonged cooling of the unsaturated zone is consistent with magmatic heat inputs and deep seated sub water table hydrothermal activity generated by the large magma body 8 km to the north that produced the 15 11 ma ash flows and ash falls that make up yucca mountain the evidence discussed in this and preceding papers strongly supports unsaturated zone deposition of the secondary minerals from descending meteoric waters although depositional temperatures reflect conductive and possibly vapor phase convective heating of the unsaturated zone related to regional magmatic sources until perhaps 6 ma depositional conditions similar to the present day unsaturated zone have prevailed for at least the past 2 4 ma

mapping of an ophiolite complex by high resolution visible infrared spectrometry the sumail massif of the oman peridotite has been surveyed by the high spectral resolution imager hymap the field measurements have been taken simultaneously to the hymap campaign with a ger 3700 spectrometer to compare the two data sets further calibration and atmospheric correction are made through empirical line corrections a continuum removal by a modified gaussian model on reflectance is then performed for each pixel to minimize atmospheric scattering and shadowing effects classification from spectral distance is established using field observations and comparisons at full spectral resolution to identify peridotite subunits harzburgites and dunites and to distinguish plagioclase wehrlites from gabbros detections of hydrothermal transformations of olivine in serpentines and their alteration in carbonates along fracture networks characterized by narrow spectral signatures validate the classification this demonstrates the utility of the high spectral resolution and the development of appropriate processing methods for geological identifications

visible and near infrared spectra of carbonate rocks reflectance variations related to petrographic texture and impurities grain size statistics derived from thin section point measurements were used to classify carbonate rock textures and to identify related spectral characteristics in the visible and near infrared 0 4 2 5 m wavelength range although the statistics did not permit all the carbonate textural varieties generally recognized by petrologists to be distinguished three broad textural classes of pure carbonate material were found that produced distinctive spectra further refinement of the statistical technique may permit other textural classes to be identified however internal scattering in carbonate rocks is a complex phenomenon involving the grain size distribution as well as the nature and abundance of inclusions and internal grain defects to yield an optimum textural classification for spectroscopic studies all such scattering contributors would have to be quantified the spectral effects of iron oxide clay silica and organic matter impurities were examined by comparing texturally similar pure and impure carbonate rock samples of these impurities organic matter had the greatest spectral influence and amounts as low as 0 01 wt commonly caused marked reductions in sample brightness and absorption band intensity in contrast the spectral effects of rock texture were subtle and could only be identified in samples that were nearly free of organic matter impurities the pronounced organic matter spectral effects imply that the organic matter in most carbonates is very finely disseminated samples collected from different regions usually showed different degrees of organic spectral quenching however no correlations were evident between sample reflectance and contained kerogen h c ratios or kerogen amounts additional analytical work is needed to examine organic matter compositional variation and associated spectral quenching effects in detail from the present study it appears likely that contained organic matter will be a dominant factor in the visible and near infrared spectral expression for most carbonate rocks and perhaps for other sedimentary lithologies spectral quenching by organic matter will likely complicate remote sensing and laboratory spectral determinations of carbonate composition on the other hand variations in quenching may prove to be useful for distinguishing rocks that have experienced unusual diagenetic thermal or other conditions affecting the organic matter contents

an evaluation of paired δ18o and 234u 238u 0 in opal as a tool for paleoclimate reconstruction in semi arid environments abstract authigenic opal deposits are widespread in semi arid and arid environments and often contain high uranium concentrations that facilitate high precision dating by u series and u pb geochronology however despite their ubiquity and utility for placing temporal constraints on surficial processes the potential for authigenic opal deposits to be used as archives of past climate variability remains largely unexplored compared with more frequently used authigenic carbonate deposits here we investigate the potential for authigenic opal deposits to provide records of paleoclimate and paleohydrologic variability through the development of a combined record of uranium 234 u 238 u 0 and oxygen 18 o isotope variability using in situ ion microprobe methods on opal deposits from pinnacles national park california that precipitated from approximately 16 to 3 ka pinnacles opal 234 u 238 u 0 suggests a moderate decrease in net infiltration from the early to middle holocene coincident with the timing of increasing aridity inferred from sierra nevada lake records while pinnacles opal 18 o indicates a relative increase in subtropical storms at the same time a shift to more north pacific sourced storms commenced after 5 ka coincident with the easing of aridity in northern california and increased storminess in the sierra nevada as indicated by lake sediment records these results suggest that useful insights about past hydrologic change can be gleaned from authigenic opal deposits and that these deposits have the potential to enhance the spatial and temporal coverage of paleoclimate reconstructions in regions where other archives might be scarce however further study of the influence of water in opal on 18 o variability and additional in situ analysis of 18 o variability on longer lived opal deposits with uniform growth histories are necessary to verify the controls on this potential proxy similarly further investigation into short term and spatial variability in 234 u 238 u sw will improve qualitative and quantitative applications of 234 u 238 u 0 in authigenic opal deposits enhancing our ability to use this promising new paleoclimate archive

aster capability in mapping of mineral resources of arid region a review on mapping of mineral resources of the sultanate of oman abstract advanced space borne thermal emission and reflection radiometer aster has exclusive capability to map minerals and ore deposits and able to discriminate rock types useful for geological applications especially the improved spectral and spatial resolutions of spectral bands of the sensor are well utilized by the exploration geologists working on arid region where the surface deposits are directly exposed to the sensor without disturbances of the vegetation several fruitful research studies have been carried out to map mineral resources in arid region with inaccessible rugged mountains and deserts area where it is difficult to do conventional geological mapping these were demonstrated and documented in the scientific publications using the aster spectral bands and image processing methods this study reviews scientific literatures published on mapping of the economic mineral resources of the sultanate of oman using aster and simples image processing methods

18o 16o evidence for an early short lived 10 yr fumarolic event in the topopah spring tuff near the proposed high level nuclear waste repository within yucca mountain nevada usa abstract 18 o 16 o analyses of rock samples from the exploratory studies facility esf and from three other locations in the vicinity of yucca mountain nevada suggest that the uppermost 5 20 m of the 12 8 ma topopah spring tuff displays a characteristic 18 o 16 o pattern that is indicative of short lived 10 yr high temperature 500 c fumarolic meteoric hydrothermal activity hydrothermally altered rock is characterized by 1 3 m thick zones of 18 o depleted groundmass down to 18 o 5 5 located above and locally within the upper vitrophyre as well as complementary 2 4 m thick overlying zones of 18 o enriched as high as 18 o 13 7 mineralogically altered groundmass thirty four samples of the topopah spring tuff collected below the upper vitrophyre are not hydrothermally altered and correspondingly display a more uniform set of 18 o values 18 o 8 6 to 11 1 sanidine phenocrysts from fumarolically altered tuff in the upper cooling unit are petrographically pristine and also display uniform 18 o values 18 o 7 80 0 45 which are in isotopic equilibrium with other phenocryst phases at magmatic temperatures the 18 o 16 o signature displayed by the upper part of the topopah spring tuff is analogous to that produced by short lived 10 25 yr high temperature 500 c fumarolic activity in the bishop tuff and in the 1912 ash flow sheet in the valley of ten thousand smokes alaska the remarkable preservation of a fragile fumarolic 18 o 16 o signature in the upper part of the topopah spring tuff indicates that no subsequent hydrothermal alteration of this part of the tuff has occurred

sims analyses of minor and trace element distributions in fracture calcite from yucca mountain nevada usa abstract fracture lining calcite samples from yucca mountain nevada obtained as part of the extensive vertical sampling in studies of this site as a potential high level waste repository have been characterized according to microbeam scale 25 30 m trace and minor element chemistry and cathodoluminescent zonation patterns as bulk chemical analyses are limited in spatial resolution and are subject to contamination by intergrown phases a technique for analysis by secondary ion mass spectrometry sims of minor mn fe sr and trace ree elements in calcite was developed and applied to eighteen calcite samples from four boreholes and one trench sims analyses of ree in calcite and dolomite have been shown to be quantitative to abundances bulk chemical signatures noted by vaniman 1994 allowed correlation of minor and trace element signatures in yucca mountain calcite with location of calcite precipitation saturated vs unsaturated zone for example upper unsaturated zone calcite exhibits pronounced negative ce and eu anomalies not observed in calcite collected below in the deep unsaturated zone these chemical distinctions served as fingerprints which were applied to growth zones in order to examine temporal changes in calcite crystallization histories analyses of such fine scale zonal variations are unattainable using bulk analytical techniques in addition lree particularly ce scavenging of calcite precipitating solutions by manganese oxide phases is discussed as the mechanism for ce depletion in unsaturated zone calcite

consequences of slow growth for 230th u dating of quaternary opals yucca mountain nv usa thermal ionization mass spectrometry and data are reported for uranium rich opals coating fractures and cavities within the silicic tuffs forming yucca mountain nv the potential site of a high level radioactive waste repository high uranium concentrations up to 207 ppm and extremely high activity ratios up to about 106 make microsamples of these opals suitable for precise dating conventional ages range from 40 to greater than 600 ka and initial activity ratios between 1 03 and 8 2 isotopic evidence indicates that the opals have not experienced uranium mobility however wide variations in apparent ages and initial ratios for separate subsamples of the same outermost mineral surfaces positive correlation between ages and sample weights and negative correlation between ages and calculated initial are inconsistent with the assumption that all minerals in a given subsample was deposited instantaneously the data are more consistent with a conceptual model of continuous deposition where secondary mineral growth has occurred at a constant slow rate up to the present this model assumes that individual subsamples represent mixtures of older and younger material and that calculations using the resulting isotope ratios reflect an average age ages calculated using the continuous deposition model for opals imply average mineral growth rates of less than 5 mm m y the model of continuous deposition also predicts discordance between ages obtained using different radiometric methods for the same subsample differences in half lives will result in younger apparent ages for the shorter lived isotope due to the greater influence of younger materials continuously added to mineral surfaces discordant and u pb ages obtained from outermost mineral surfaces at yucca mountain support this model

backarc thrust faulting and tectonic uplift along the caribbean sea coast during the april 22 1991 costa rica earthquake surface deformation and a tsunami accompanied the destructive april 22 1991 costa rica panama earthquake ms 7 5 along a 135 km stretch of caribbean coast coseismic uplift was measured between the lower and upper limits of sessile intertidal organisms stranded on coral reefs the preearthquake and postearthquake high tide levels located from driftwood lines on beaches and the preearthquake and postearthquake tide levels as pointed out by local residents the nature and distribution of offshore vertical displacements were further constrained from analysis of measured run up heights and reported arrival times of the tsunami uplift detected along the coast jumped within 4 km from zero to 157 cm near limon and generally decreased over a distance of 70 km southward to the border with panama these data map an axis of uplift that intersects the coastal beach ridge just north of the port of moin and runs offshore to the east and south roughly parallel to the coast no surface faulting was found the earthquake and tsunami were generated by backarc thrusting along faults that bound the north panama deformed belt and dip from the caribbean sea beneath costa rica and northern panama combined geodetic and seismological data indicate that the main rupture dips landward at an angle of about 30 and is approximately 40 km wide and 80 km long dislocation models suggest 2 2 m of slip on a causative thrust fault striking between 105 and 120 we estimate that the repeat time for this type of earthquake is 200 to 1100 years the historical record and new isotopic data favor the middle of the range

natural radionuclide mobility and its influence on u th pb dating of secondary minerals from the unsaturated zone at yucca mountain nevada abstract extreme u and pb isotope variations produced by disequilibrium in decay chains of 238u and 232th are found in calcite opal chalcedony and mn oxides occurring as secondary mineral coatings in the unsaturated zone at yucca mountain nevada these very slowly growing minerals mm my 1 contain excess 206pb and 208pb formed from excesses of intermediate daughter isotopes and cannot be used as reliable 206pb 238u geochronometers the presence of excess intermediate daughter isotopes does not appreciably affect 207pb 235u ages of u enriched opal chalcedony which are interpreted as mineral formation ages opal and calcite from outer younger portions of coatings have 230th u ages from 94 6 3 7 to 361 3 9 8 ka and initial 234u 238u activity ratios ar from 4 351 0 070 to 7 02 0 12 which indicate 234u enrichment from percolating water present day 234u 238u ar is 1 in opal chalcedony from older portions of the coatings the 207pb 235u ages of opal chalcedony samples range from 0 1329 0 0080 to 9 10 0 21 ma increase with microstratigraphic depth and define slow long term average growth rates of about 1 2 2 0 mm my 1 in good agreement with previous results measured 234u 238u ar in mn oxides which pre date the oldest calcite and opal chalcedony range from 0 939 0 006 to 2 091 0 006 and are 1 in most samples the range of 87sr 86sr ratios 0 71156 0 71280 in mn oxides overlaps that in the late calcite these data indicate that mn oxides exchange u and sr with percolating water and cannot be used as a reliable dating tool in the u poor calcite samples measured 206pb 207pb ratios have a wide range do not correlate with ba concentration as would be expected if excess ra was present and reach a value of about 1400 the highest ever reported for natural pb calcite intergrown with opal contains excesses of both 206pb and 207pb derived from rn diffusion and from direct recoil from u rich opal calcite from coatings devoid of opal chalcedony contains 206pb and 208pb excesses but no appreciable 207pb excesses observed pb isotope anomalies in calcite are explained by rn produced excess pb the rn emanation may strongly affect 206pb 238u ages of slow growing u poor calcite but should be negligible for dating fast growing u enriched speleothem calcite

spectral characterization and aster based lithological mapping of an ophiolite complex a case study from neyriz ophiolite sw iran abstract the neyriz ophiolite occurs along the zagros suture zone in sw iran and is part of a 3000 km obduction belt thrusting over the edge of the arabian continent during the late cretaceous this complex typically consists of altered dunites and peridotites layered and massive gabbros sheeted dykes and pillow lavas and a thick sequence of radiolarites reflectance and emittance spectra of neyriz ophiolite rock samples were measured in the laboratory and their spectra were used as endmembers in a spectral feature fitting sff algorithm laboratory spectral reflectance measurements of field samples showed that in the visible through shortwave infrared vnir swir wavelength region the ultramafic and gabbroic rocks are characterized by ferrous iron and fe mg oh spectral features and the pillow lavas and radiolarites are characterized by spectral features of ferric iron and al oh the laboratory spectral emittance spectra also revealed a wide wavelength range of si o spectral features for the ophiolite rock units after continuum removal of the spectra the sff classification method was applied to the vnir swir 9 band stack and to the 11 band data set of swir and tir data sets of the advanced spaceborne thermal emission and reflection radiometer aster sensor using field spectra as training sets for evaluating the potential of these data sets in discriminating ophiolite rock units output results were compared with the geological map of the area and field observations and were assessed by the use of confusion matrices the assessment showed in terms of kappa coefficient that the sff classification method with continuum removal applied to the swir data achieved excellent results which were distinctively better than those obtained using vnir swir data and tir data alone