origin timing and temperature of secondary calcite silica mineral formation at yucca mountain nevada the origin of secondary calcite silica minerals in primary and secondary porosity of the host miocene tuffs at yucca mountain has been hotly debated during the last decade proponents of a high level nuclear waste repository beneath yucca mountain have interpreted the secondary minerals to have formed from cool descending meteoric fluids in the vadose zone critics citing the presence of two phase fluid inclusions argued that the minerals could only have formed in the phreatic zone from ascending hydrothermal fluids understanding the origin temperature and timing of these minerals is critical in characterizing geologically recent fluid flux at the site and has significant implications to whether waste should be stored at yucca mountain petrographic and paragenetic studies of 155 samples collected from the exploratory studies facility esf and repository block cross drift ecrb tunnels indicate that heterogeneously distributed calcite with lesser chalcedony quartz opal and fluorite comprise the oldest secondary minerals these are typically overgrown by intermediate aged calcite often exhibiting distinctive bladed habits the youngest event recorded across the site is the deposition of mg enriched up to 1 wt and depleted growth zoned calcite intergrown with u enriched opal the cyclical variation in mg enrichment and depletion is probably related to climate changes that have occurred during the last few million years the distribution of secondary minerals is consistent with precipitation in the vadose zone fluid inclusion petrography of sections from the 155 samples determined that 96 of the fluid inclusion assemblages fias contained liquid only inclusions that formed at ambient temperatures 35 c however 50 of the samples n 78 contained relatively rare fia that contain both liquid only and liquid plus vapor inclusions herein termed two phase fias that formed at temperatures above 35 c virtually all of these two phase fias occur in paragenetically old calcite rare two phase inclusion assemblages were also observed in early fluorite and quartz and early intermediate calcite homogenization temperatures trapping temperatures across yucca mountain are generally 45 to 60 c but higher temperatures reaching 83 c were recorded in calcite from the north portal and ramp of the esf cooler temperatures of 35 to 45 c were recorded in the intensely fractured zone multiple populations of two phase fias from lithophysal cavities in the esf and ecrb cross drift indicate early fluid cooling with time from temperatures 45 c in early calcite to 35 to 45 c in paragenetically younger calcite freezing point depressions range from 0 2 to 1 6 c indicating trapping of a low salinity fluid the majority of intermediate calcite and all outermost mg enriched calcite contains rare all liquid inclusions and formed from ambient temperature 35 c fluids carbon and oxygen isotope data reveal a consistent trend of decreasing 13 c from 9 5 to 8 5 and increasing 18 o from 5 2 to 22 1 values from paragenetically early calcite to mg enriched growth zoned calcite depleted d values 131 to 90 of inclusion fluids from intermediate and the youngest mg enriched calcite indicate derivation from surface meteoric fluids recalculation of 18 oh2o values of 12 to 10 is consistent with derivation from paleometeoric fluids results of integrated u pb dating opal and chalcedony and fluid inclusion microthermometry indicate that two phase fias that trapped fluids of 50 c are older than 6 29 0 30 ma two phase fias in parage netically later calcite which formed from fluids of 35 to 45 c are older than 5 32 0 02 ma there is no evidence for trapping of fluids with elevated temperatures during the past 5 32 my the youngest mg enriched calcite intergrown with opal began to precipitate between about 1 9 to 2 9 ma and has continued to precipitate within the past half million years the presence of liquid only inclusions and the consistent occurrence of mg enriched calcite and opal as the youngest event indicate a minor but chemically distinct ambient temperature 35 c fluid flux during the past 2 to 3 my copyright 2003 elsevier science ltd

a slab in depth three dimensional geometry and evolution of the indo australian plate geoscientists use plate tectonics to explain many aspects of both continental evolution and evolution of the planet as a whole the subduction of material at convergent plate boundaries forms a fundamental component to the theory of plate tectonics plates continents subduction zones and spreading centers all exhibit motion and geometric evolution so to try and resolve the past geometries of the planet geologists have utilized plate tectonic reconstructions here we present a three dimensional image of the subducted indo australian plate below southeast asia and show that the geometry of the subducted slab at depth is intimately related to the geometric evolution of se asia over the past 50 ma including the collision of india with the asian continent we show how the once semicontinuous subducting indo australian plate has been segmented during collision between india australian and the subduction margin to the north thus we have found that the geometry of the subducted plate should form a key component to the interpretation of the evolution of earth s surface as complexities and evolution of the subducted plate are manifest in the evolution of the overriding plate

late cretaceous oceanic crust and early tertiary foreland basin development euboea eastern greece in northern euboea eastern greece late cretaceous platform carbonates of the pelagonian zone pass depositionally upwards into maastrichtian hemipelagic limestones possibly reflecting a rifting event in the adjacent neotethys this is followed by a c 1 km thick unit of siliciclastic turbidites debris flows and detached limestone blocks thrust intercalations of ophiolitic rocks comprise altered pillow basalts and ultramafic rocks with ophicalcite calcite veins in sheared serpentinite contain planktonic foraminifera and the ophicalcite is directly overlain with a depositional contact by globotruncana bearing pelagic limestones and calciturbidites of maastrichtian age the ophiolitic rocks are interpreted as late cretaceous oceanic crust and mantle that formed at a fracture zone or rifted spreading axis within a neotethyan vardar basin to the east during the early tertiary palaeocene eocene the neotethyan basin began to close with development of a subduction accretion complex mainly comprising sheared trench type sandstones associated with ophiolitic slices in response to trench margin collision the pelagonian carbonate platform foundered and limestone debris flows and olistoliths were shed into a siliciclastic foreland basin suturing of the neotethyan ocean basin then resulted in westwards thrusting of oceanic units over the foreland basin thrusting of slices of inferred late cretaceous pelagonian carbonate platform slope and large scale recumbent folding

evidence for neotethys rooted within the vardar suture zone from the voras massif northernmost greece abstract three conflicting models are currently proposed for the location and tectonic setting of the eurasian continental margin and adjacent tethys ocean in the balkan region during mesozoic early tertiary time model 1 places the eurasian margin within the rhodope zone relatively close to the moesian platform a tethyan oceanic basin was located to the south bordering a large serbo pelagonian microcontinent model 2 correlates an integral serbo pelagonian continental unit with the eurasian margin and locates the tethys further southwest model 3 envisages the pelagonian zone and the serbo macedonian zone as conjugate continental units separated by a tethyan ocean that was sutured in early tertiary time to create the vardar zone of northern greece and former yugoslavia these published alternatives are tested in this paper based on a study of the tectono stratigraphy of a completely exposed transect located in the voras mountains of northernmost greece the outcrop extends across the vardar zone from the pelagonian zone in the west to the serbo macedonian zone in the east within the voras massif six east dipping imbricate thrust sheets are recognised of these units 1 4 correlate with the regional pelagonian zone in the west and related almopias sub zone by contrast units 5 6 show a contrasting tectono stratigraphy and correlate with the paikon massif and the serbo macedonian zone to the east these units form a stack of thrust sheets with unit 1 at the base and unit 6 at the top unstacking these thrust sheets places ophiolitic units between the pelagonian zone and the serbo macedonian zone as in model 3 additional implications are first that the paikon massif cannot be seen as a window of pelagonian basement as in model 1 and secondly jurassic andesitic volcanics of the paikon massif locally preserve a gneissose continental basement ruling out a recently suggested origin as an intra oceanic arc we envisage that the almopias vardar ocean rifted in triassic time followed by seafloor spreading the almopias ocean was consumed beneath the serbo macedonian margin in jurassic time generating subduction related arc volcanism in the paikon massif and related units ophiolites were emplaced onto the pelagonian margin in the west and covered by late jurassic pre kimmeridgian conglomerates other ophiolitic rocks formed within the vardar zone ano garefi ophiolite unit 4 in latest jurassic early cretaceous time and were not deformed until early tertiary time the vardar zone finally sutured in the early tertiary creating the present imbricate thrust structure of the voras mountains

the geohydrologic setting of yucca mountain nevada abstract this paper provides a geologic and hydrologic framework of the yucca mountain region for the geochemical papers in this volume the regional geologic units which range in age from late precambrian through holocene are briefly described yucca mountain is composed of dominantly pyroclastic units that range in age from 11 4 to 15 2 ma the principal focus of study has been on the paintbrush group which includes two major zoned and welded ash flow tuffs separated by an important hydrogeologic unit referred to as the paintbrush non welded ptn the regional structural setting is currently one of extension and the major local tectonic domains are presented together with a tectonic model that is consistent with the known structures at yucca mountain streamflow in this arid to semi arid region occurs principally in intermittent or ephemeral channels near yucca mountain the channels of fortymile wash and amargosa river collect infrequent runoff from tributary basins ultimately draining to death valley beneath the surface large scale interbasin flow of groundwater from one valley to another occurs commonly in the region regional groundwater flow beneath yucca mountain originates in the high mesas to the north and returns to the surface either in southern amargosa desert or in death valley where it is consumed by evapotranspiration the water table is very deep beneath the upland areas such as yucca mountain where it is 500 750 m below the land surface providing a large thickness of unsaturated rocks that are potentially suitable to host a nuclear waste repository the nature of unsaturated flow processes which are important for assessing radionuclide migration are inferred mainly from hydrochemical or isotopic evidence from pneumatic tests of the fracture systems and from the results of in situ experiments water seeping down through the unsaturated zone flows rapidly through fractures and more slowly through the pores of the rock matrix although capillary forces are expected to divert much of the flow around repository openings some may drip onto waste packages ultimately causing release of radionuclides followed by transport down to the water table

improved spatial resolution for u series dating of opal at yucca mountain nevada usa using ion microprobe and microdigestion methods two novel methods of in situ isotope analysis ion microprobe and microdigestion were used for 230th u and 234u 238u dating of finely laminated opal hemispheres formed in unsaturated felsic tuff at yucca mountain nevada proposed site for a high level radioactive waste repository both methods allow analysis of layers as many as several orders of magnitude thinner than standard methods using total hemisphere digestion that were reported previously average growth rates calculated from data at this improved spatial resolution verified that opal grew at extremely slow rates over the last million years growth rates of 0 58 and 0 69 mm m y were obtained for the outer 305 and 740 m of two opal hemispheres analyzed by ion microprobe and 0 68 mm m y for the outer 22 m of one of these same hemispheres analyzed by sequential microdigestion these pleistocene growth rates are 2 to 10 times slower than those calculated for older secondary calcite and silica mineral coatings deposited over the last 5 to 10 m y dated by the u pb method and may reflect differences between miocene and pleistocene seepage flux the microdigestion data also imply that opal growth rates may have varied over the last 40 k y these data are the first indication that growth rates and associated seepage in the proposed repository horizon may correlate with changes in late pleistocene climate involving faster growth during wetter cooler climates glacial maximum slower growth during transition climates and no growth during the most arid climate modern data collected at this refined spatial scale may lead to a better understanding of the hydrologic variability expected within the thick unsaturated zone at yucca mountain over the time scale of interest for radioactive waste isolation

the collision tectonics of the southern greek neotethys continental collision in the aegean area has produced a collage of micro continental blocks which were accreted to the active margin of eurasia in early tertiary times studies undertaken in the argolis peninsula of southern greece located at the southern end of the pelagonian continental terrane confirm that this block was rifted from gondwana in mid triassic times by mid jurassic times at the latest actively spreading oceanic basins had opened in both the pindos and vardar zones on either side of this block identification of late cretaceous oceanic basalts within an accretionary complex in the eastern argolis peninsula extends the history of the neotethys beyond late jurassic ophiolite emplacement previously believed to be the result of continental collision the cretaceous ocean basins were relict jurassic features as no rifting event is known which can account for their formation following ophiolite obduction after a phase of late cretaceous oceanic spreading in the eastern vardar oceanic basin early tertiary collision occurred as a result of northeast dipping subduction along the eastern margins of both pindos and vardar branches of the neotethys two distinct nappe emplacement vectors are identified in the argolis peninsula after accounting for neotectonic rotations these are interpreted to reflect sw directed orthogonal collision in the west and nw directed emplacement in the east resulting from tranpressional collision along the southern end of the pelagonian block

subduction of continental lithosphere in the banda sea region combining evidence from full waveform tomography and isotope ratios article i nfo we provide new insight into the subduction of old continental lithosphere to depths of more than 100 km beneath the banda arc based on a spatial correlation of full waveform tomographic images of its lithosphere with he pb nd and sr isotope signatures in its arc volcanics the thickness of the subducted lithosphere of around 200 km coincides with the thickness of precambrian lithosphere as inferred from surface wave tomography while the deep subduction of continental material in continent continent collisions is widely recognised the analogue process in the arc continent collision of the banda region is currently unique the integrated data suggest that the late jurassic ocean lithosphere north of the north australian craton was capable of entraining large volumes of continental lithosphere the banda arc example demonstrates that continental lithosphere in arc continent collisions is not generally preserved thus increasing the complexity of tectonic reconstructions in the particular case of timor the tomographic images indicate that this island is not located directly above the northern margin of the north australian craton and that decoupled oceanic lithosphere must be located at a considerable distance north of timor possibly as far north as the northern margin of the volcanically extinct arc sector the tomographic images combined with isotope data suggest that subduction of the continental lithosphere did not lead to the delamination of its complete crust a plausible explanation involves delamination within the continental crust separating upper from lower crustal units this interpretation is consistent with the existence of a massive accretionary complex on timor island with evidence from pb isotope analysis for lower crust involvement in arc volcanism and with the approximate gravitational stability of the subducted lithosphere as inferred from the tomographic images the subduction of continental lithosphere including crustal material beneath the banda arc indicates that global injection rates of continental material into the mantle may have been underestimated and that continental subduction in arc continent collisions may have contributed more to isotopic signatures of earth s mantle than previously recognised

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

india asia convergence driven by the subduction of the greater indian continent the most spectacular example of plate convergence on earth was the motion of the indian plate towards eurasia and the subsequent collision density estimates of the greater indian continent after its upper crust is scraped off at the himalayan front suggest that this continental plate is readily subductable potentially explaining why the convergence did not halt on collision the most spectacular example of a plate convergence event on earth is the motion of the indian plate towards eurasia at speeds in excess of 18 cm yr 1 ref 1 and the subsequent collision continental buoyancy usually stalls subduction shortly after collision as is seen in most sections of the alpine himalayan chain however in the indian section of this chain plate velocities were merely reduced by a factor of about three when the indian continental margin impinged on the eurasian trench about 50 million years ago plate convergence accompanied by eurasian indentation persisted throughout the cenozoic era1 2 3 suggesting that the driving forces of convergence did not vanish on continental collision here we estimate the density of the greater indian continent after its upper crust is scraped off at the himalayan front and find that the continental plate is readily subductable using numerical models we show that subduction of such a dense continent reduces convergence by a factor similar to that observed in addition an imbalance between ridge push and slab pull can develop and cause trench advance and indentation we conclude that the subduction of the dense indian continental slab provides a significant driving force for the current india asia convergence and explains the documented evolution of plate velocities following continental collision

understanding the genesis of nonmarine calcite deposits through quadrupole mass spectrometric analysis of fluid inclusion gases abstract quadrupole mass spectroscopy was used to analyze fluid inclusion volatiles in different types of nonmarine calcites including travertines phreatic calcretes hydrothermal vein calcites and pedogenic calcites the objectives of the study were to determine if there were any diagnostic or characteristic differences between the inclusion volatiles from the different calcites and to see if the quadrupole results could be used to understand the processes and environmental conditions that controlled calcite precipitation the calcites formed under saturated conditions have water dominated inclusions with well constrained n 2 ar ratios and either co 2 or n 2 as the dominant inclusion gas some calcretes and travertines were exceptions to the above characteristics but it is likely that these were subjected to secondary precipitation in an environment different from the primary precipitation phase results for the pedogenic calcites are quite different from calcites formed in water saturated systems pedogenic calcites have gas dominated water poor inclusions unexpectedly large ch 4 contents low o 2 contents and highly variable n 2 ar ratios the dominance of ch 4 and low o 2 contents in the pedogenic calcites suggest that anaerobic conditions occurred during at least part of the precipitation process scanning electron microscope sem examination of the pedogenic calcites shows fungal remains bacteria like forms and gels from fungi or plant roots the quadrupole and sem results suggest pedogenic calcite precipitation occurred as a result of aerobic and ultimately anaerobic microbial decay processes

erratum to reply to the comment on physical and stable isotope evidence for formation of secondary calcite and silica in the unsaturated zone yucca mountain nevada by y v dublyansky s e smirnov and g p palyanova applied geochemistry 19 2004 1879 1889

pedogenesis of siliceous calcretes at yucca mountain nevada abstract siliceous calcretes in faults near yucca mountain nevada have been interpreted by some observers as evidence of seismically triggered eruptions of deep water such an origin could have important consequences if yucca mountain is developed as an unsaturated site for disposal of high level nuclear waste at odds with this hypothesis are the absence of features that should be present at fault fed springs e g fissure ridge mounds with microterraces and the preservation within root casts of delicate pedogenic microfossils such as calcified filaments and needle fiber calcites chemical evidence of pedogenic origin is found in fe and sc enrichments that require prior weathering of detritus in the calcretes as opposed to direct incorporation of adjacent unweathered bedrock carbonate and silica abundances and accumulation rates are well within the scope of pedogenic processes sources of carbonate are eolian whereas silica is derived in part by dissolution of local volcanic glasses but also by extensive dissolution of unstable silica minerals tridymite and cristobalite that are abundant in the local tuffs the siliceous calcretes at yucca mountain are pedogenic and provide no evidence in support of conjectured spring activity

genesis of lavas of the taupo volcanic zone north island new zealand the taupo volcanic zone forms part of the taupo hikurangi subduction system and comprises five volcanic centres tongariro taupo maroa okataina and rotorua tongariro volcanic centre is formed almost entirely of andesite while the other four centres contain predominantly rhyolitic volcanics and later fissure eruptions of high al basalt estimated total volume of each lava type are as follows 2 km3 of high al basalt 10 000 km3 of rhyolite and ignimbrite 97 4 the location of the andesites and vent alignments suggest a source from a subduction zone underlying the area however the lavas differ chemically from island arc andesites such as those of tonga in particular by having higher contents of the alkali elements light ree and sr and pb isotopes this suggests some crustal contamination and it is considered that this may occur beneath the wide accretionary prism of the subduction system amphibolite of the subduction zone will break down between 80 and 100 km and a partial melt will rise a multi stage process of magma genesis is then likely to occur high al basalts are thought to be derived from partial melting of a garnet free peridotite near the top of the mantle wedge overlying the subduction zone locations of the vents controlled largely by faults within the crust rhyolites and ignimbrites were probably derived from partial melting of mesozoic greywacke and argillite under the taupo volcanic zone initial partial melting may have been due to hydration of the base of the crust the water having come from dehydration of the downgoing slab the partial melts would rise to form granodiorite plutons and final release of the magma to form rhyolites and ignimbrites was allowed because of extension within the taupo graben dacites of the bay of plenty probably resulted from mixing of andesitic magma with small amounts of rhyolitic magma but those on the eastern side of the rotorua taupo area were more likely formed by a higher degree of partial melting of the mesozoic greywacke argillite basement this may be due to intrusion of andesite magma on this side of the taupo volcanic zone

reconstruction of the deformed collision zone between india and asia by backward motion of lithospheric blocks 1 on the basis of a synthesis of tectonic data available on the india asia collision we present a first attempt to reconstruct the evolution of the collision zone assuming that the deformation of the lithosphere is localized along narrow shear zones and that the interiors of mantle blocks in between remain relatively undeformed we define block contours from the fault pattern and move back the blocks along their boundary faults along convergent or extensional boundaries the crust is assumed to shorten or stretch coherently step by step we go backward in time to finally reach the collision onset for each time step we find a solution compatible with the data set available and the position of the adjacent blocks for each block the search for compatibility at the scale of the entire collision zone allows for solving the kinematics of regions with fewer data and suggests plausible scenarios for regions where data is lacking for each step we calculate large scale displacement maps and determine euler poles for each block for the most recent time step the map proposed is compared to gps motions the deformation budget implies that extrusion absorbed 30 of the convergence between india and siberia during the entire collision span but varied with time accounting for as little as 3 or as much as 60 of this convergence at different epochs

limited hydrologic response to pleistocene climate change in deep vadose zones yucca mountain nevada abstract understanding the movement of water through thick vadose zones especially on time scales encompassing long term climate change is increasingly important as societies utilize semi arid environments for both water resources and sites viewed as favorable for long term disposal or storage of hazardous waste hydrologic responses to pleistocene climate change within a deep vadose zone in the eastern mojave desert at yucca mountain nevada were evaluated by uranium series dating of finely layered hyalitic opal using secondary ion mass spectrometry opal is present within cm thick secondary hydrogenic mineral crusts coating floors of lithophysal cavities in fractured volcanic rocks at depths of 200 to 300 m below land surface uranium concentrations in opal fluctuate systematically between 5 and 550 g g age calibrated profiles of uranium concentration correlate with regional climate records over the last 300 000 years and produce time series spectral peaks that have distinct periodicities of 100 and 41 ka consistent with planetary orbital parameters these results indicate that the chemical compositions of percolating solutions varied in response to near surface climate driven processes however slow micrometers per thousand years relatively uniform growth rates of secondary opal and calcite deposition spanning several glacial interglacial climate cycles imply that water fluxes in the deep vadose zone remained low and generally buffered from the large fluctuations in available surface moisture during different climates

cenozoic plate reconstruction of southeast asia abstract the india eurasia collision alone set up a series of chain reactions and caused the formation and destruction of sedimentary basins within the domain of the collision belt changes in the rate and angle of convergence between the india and eurasia plates reflect different stages of tectonic development in southeast asia for example extrusion of the indochina block induced the consumption of the pre existing proto south china sea along northeastern kalimantan and led to the eventual opening of the south china sea along the south china margin subsequent motions of the sino burma thailand malay peninsula sumatra and kalimantan blocks have produced a succession of basins stretching from north sumatra to central thailand and on to the natuna area we present reconstructions of the southeast asia region at 60 ma 50 ma 40 ma 30 ma 20 ma 15 ma 10 ma and 5 ma it is clear from the reconstructions that the impact between greater india and southeast asia took place in the northwestern part of southeast asia the duration for the impact was probably from the middle eocene to early miocene this timing is in good agreement with the dating of the main red river fault motion wu et al 1989 scharer et al 1990 since the impact between greater india and southeast asia was basically west of the burma block there is no reason to assume that the sumatra malay peninsula and kalimantan should extrude to the southeast first along the left laterally displaced mae ping and three pagodas fault zones as suggested by peltzer and tapponnier 1988 if the opening of the central thailand basins the gulf of thailand and the malay basin are taken into consideration a dextral megashear zone is required to compensate the relative motion between indochina and the malay peninsula this dextral megashear zone might even extend into western kalimantan and serve as a boundary between the indochina block and kalimantan

episodic caldera volcanism in the miocene southwestern nevada volcanic field revised stratigraphic framework 40ar 39ar geochronology and implications for magmatism and extension the middle miocene southwestern nevada volcanic field swnvf is a classic example of a silicic multicaldera volcanic field in the great basin more than six major calderas formed between 15 and 7 5 ma the central swnvf caldera cluster consists of the overlapping silent canyon caldera complex the claim canyon caldera and the timber mountain caldera complex active from 14 to 11 5 ma and centered on topographic timber mountain locations of calderas older than the claim canyon caldera source of the tiva canyon tuff are uncertain except where verified by drilling younger peralkaline calderas black mountain and stonewall mountain formed northwest of the central swnvf caldera cluster we summarize major revisions of the swnvf stratigraphy that provide for correlation of lava flows and small volume tuffs with the widespread outflow sheets of the swnvf new laser fusion 40 ar 39 ar isotopic ages are used to refine and revise the timing of eruptive activity in the swnvf the use of high sensitivity mass spectrometry allowed analysis of submilligram sized samples with analytical uncertainties of 0 3 1 permitting resolution of age differences as small as 0 07 ma these results confirm the revised stratigraphic succession and document a pattern of episodic volcanism in the swnvf major caldera episodes belted range crater flat paintbrush timber mountain and thirsty canyon groups erupted widespread ash flow sheets within 100 300 k y time spans and pre and post caldera lavas erupted within 100 300 k y of the associated ash flows peak volcanism in the swnvf occurred during eruption of the paintbrush and timber mountain groups when over 4500 km 3 of metaluminous magma was erupted in two episodes within 1 35 m y separated by a 750 k y magmatic gap peralkaline and metaluminous magmatism in the swnvf overlapped in time and space the peralkaline tub spring and grouse canyon tuffs erupted early and the peralkaline thirsty canyon group tuffs and stonewall flat tuff erupted late in the history of the swnvf flanking the central volumetrically dominant peak of metaluminous volcanism magma chemistry transitional between peralkaline and metaluminous magmas is indicated by petrographic and chemical data particularly in the overlapping grouse canyon and area 20 calderas of the silent canyon caldera complex volcanism in the swnvf coincided with the miocene peak of extensional deformation in adjoining parts of the great basin although regional extension was concurrent with volcanism it was at a minimum in the central area of the swnvf where synvolcanic faulting was dominated by intra caldera deformation significant stratal tilting and paleomagnetically determined dextral shear affected the southwestern margin of the swnvf between the paint brush and timber mountain caldera episodes larger magnitude detachment faulting in the bullfrog hills southwest of the central swnvf caldera cluster followed the climactic timber mountain caldera episode postvolcanic normal faulting was substantial to the north east and south of the central swnvf caldera cluster but the central area of peak volcanic activity remained relatively unextended in postvolcanic time volcanism and extension in the swnvf area were broadly concurrent but swnvf area were broadly concurrent but in detail they were episodic in time and not coincident in space

subsidence history of the north indian continental margin zanskar ladakh himalaya nw india detailed geological field mapping has allowed the restoration of two full stratigraphic sections through the highly deformed mesozoic and early tertiary fold and thrust belt of the north indian continental margin the two sections which are representative of a proximal and a distal facies on the margin have been backstripped using standard techniques profiles of the tectonic subsidence and uplift through the pre collisional history of the margin have been constructed and compared with the predictions of simple thermal and mechanical models the pre collisional history can be explained by a thermal model with an initial age of rifting of 270 ma and a stretching factor of c 1 2 this model accounts for the general exponential decrease in the backstripped tectonic subsidence the model fails however to completely explain the subsidence and uplift history of the margin since the late cretaceous the history during this time is characterized by uplift at the most proximal location and an increase in subsidence at the most distal location we attribute these differential vertical movements to flexural loading of the north indian margin by obduction of the spontang ophiolite the best fit model is one in which a 70 km wide wedge shaped load tapering from 10 to 0 km thick is emplaced on rifted lithosphere with an elastic thickness t e of 5 10 km these results which are in accord with the late cretaceous timing of obduction and the structure of the spontang ophiolite provide new constraints on the t e structure of extended continental lithosphere 120 150 ma after a rifting event

mesozoic extensional history of the southern tethyan continental margin in the se aegean the islands of rhodes alimnia and symi are situated at the eastern end of the hellenic arc well exposed on these islands are a series of nappes composed of mesozoic early tertiary principally carbonate sequences which formed the sedimentary cover of the southern tethyan margin and were stacked during alpine deformation in the late palaeogene the stratigraphy of these sequences is described and interpreted as preserving a transition from a carbonate platform through slope to basin the sequences formed part of the cover of a passive continental margin but this margin differed from typical modern margins in recording several episodes of extension with no clear evidence of ocean crust formation in the se aegean three important episodes of extension are recorded a platform basin topography was initiated by mid late triassic rifting late liassic extension led to platform collapse and development of carbonate slopes and renewed late cretaceous extension further reduced the size of carbonate platforms the late cretaceous extension was probably linked to the formation of ocean crust further east in cyprus and turkey sedimentological evidence indicates that the slope was eastward facing and the platform basin margin was orientated approximately north south this evidence is not consistent with previously proposed palaeogeographic reconstructions of the region based on tracing the isopic zones of the hellenides through the arc a new two dimensional reconstruction of the form of the southern tethyan margin in the se aegean is proposed

the ophiolites of the tibetan geotraverses lhasa to golmud 1985 and lhasa to kathmandu 1986 ophiolite belts are found in tibet along the zangbo banggong and jinsha river sutures and in the anyemaqen mountains the eastern extension of the kunlun mountains where studied the zangbo suture ophiolites are characterized by apparently thin crustal sequences 3 3 5 km an abundance of sills and dykes throughout the crustal and uppermost mantle sequences common intraoceanic melanges and unconformities and an n morb petrological and geochemical composition the ophiolites probably formed within the main neo tethyan ocean and the unusual features may be due to proximity to ridge transform intersections rather than to genesis at very slow spreading ridges as the current consensus suggests the banggong suture ophiolites have a supra subduction zone petrological and geochemical composition although at least one locality in the ado massif shows morb characteristics however it is also apparent that the dykes and lavas show a regional chemical zonation from boninites and primitive island arc tholeiites in the south of the ophiolite belt through normal island arc tholeiites in the central belt to island arc tholeiites transitional to n morb in the north the ophiolites could represent fragments of a fore arc island arc back arc complex developed above a jurassic northward dipping subduction zone and emplaced in several stages during convergence of the lhasa and qiangtang terranes the ophiolites of the jinsha river suture have a n morb composition where analysed but more information is needed for a proper characterization the anyemaqen ophiolites where studied have a within plate tholeiite composition and may have originated at a passive margin it is not however certain whether true oceanic lithosphere as opposed to strongly attenuated continental lithosphere existed in this region

tectonics sinking continents the sequence of events during the collision between india and eurasia has long been contested numerical simulations imply that the key to the puzzle could lie in the subduction of continental lithosphere

subduction history of the tethyan region derived from seismic tomography and tectonic reconstructions 1 in the mantle underneath the tethyan suture zone large volumes of positive velocity anomalies have been imaged by seismic tomography and interpreted as the present day signature of subducted tethyan lithosphere we investigate the mesozoic cenozoic subduction history of the region by integrating independent information from mantle tomography and tectonic reconstructions three different subduction scenarios for the tethyan oceanic lithosphere representative for the available tectonic reconstructions are used to predict the present thermally anomalous volumes associated with the lithospheric surface subducted since the late mesozoic next these predicted thermal volumes and their expected positions are compared to the relevant anomalous volumes derived from seismic tomographic images in this analysis we include among others the possible effects of ridge subduction and slab detachment after the cenozoic continental collisions absolute plate motion and slab thickening in the mantle our preferred subduction model comprises the opening of large back arc oceanic basins within the eurasian margin the model points to slab thickening by a factor of 3 in the mantle in which case the estimated volumes allow for active oceanic spreading 1 2 5 cm yr in the tethyan lithosphere during convergence our results further indicate the occurrence of early oligocene slab detachment underneath the northern zagros suture zone followed by both westward and eastward propagation of the slab tear and diachronous eocene to miocene slab detachment below the eastern to western himalayas free sinking rates of the detached material of 2 cm yr in the lower mantle provide the best fit between the tomographic mantle structure and our tethyan subduction model

u and sr isotopes in ground water and calcite yucca mountain nevada evidence against upwelling water hydrogenic calcite and opaline silica deposits in fault zones at yucca mountain nevada have created considerable public and scientific controversy because of the possible development of a high level nuclear waste repository at this location strontium and uranium isotopic compositions of hydrogenic materials were used to test whether the veins could have formed by upwelling of deep seated waters the vein deposits are isotopically distinct from ground water in the two aquifers that underlie yucca mountain indicating that the calcite could not have precipitated from ground water the data are consistent with a surficial origin for the hydrogenic deposits

u pb ages of secondary silica at yucca mountain nevada implications for the paleohydrology of the unsaturated zone abstract uranium th and pb isotopes were analyzed in layers of opal and chalcedony from individual mm to cm thick calcite and silica coatings at yucca mountain nevada usa a site that is being evaluated for a potential high level nuclear waste repository these calcite and silica coatings on fractures and in lithophysal cavities in miocene age tuffs in the unsaturated zone uz precipitated from descending water and record a long history of percolation through the uz opal and chalcedony have high concentrations of u 10 to 780 ppm and low concentrations of common pb as indicated by large values of 206pb 204pb up to 53 806 thus making them suitable for u pb age determinations interpretations of u pb isotope systems in opal samples at yucca mountain are complicated by the incorporation of excess 234u at the time of mineral formation resulting in reverse discordance of u pb ages however the 207pb 235u ages are much less affected by deviation from initial secular equilibrium and provide reliable ages of most silica deposits between 0 6 and 9 8 ma for chalcedony subsamples showing normal age discordance these ages may represent minimum times of deposition typically 207pb 235u ages are consistent with the microstratigraphy in the mineral coating samples such that the youngest ages are for subsamples from outer layers intermediate ages are from inner layers and oldest ages are from innermost layers 234u and 230th in most silica layers deeper in the coatings are in secular equilibrium with 238u which is consistent with their old age and closed system behavior during the past 0 5 ma the ages for subsamples of silica layers from different microstratigraphic positions in individual calcite and silica coating samples collected from lithophysal cavities in the welded part of the topopah spring tuff yield slow long term average growth rates of 1 to 5 mm ma these data imply that the deeper parts of the uz at yucca mountain maintained long term hydrologic stability over the past 10 ma despite significant climate variations u pb ages for subsamples of silica layers from different microstratigraphic positions in individual calcite and silica coating samples collected from fractures in the shallower part of the uz welded part of the overlying tiva canyon tuff indicate larger long term average growth rates up to 23 mm ma and an absence of recently deposited materials ages of outermost layers are 3 5 ma these differences between the characteristics of the coatings for samples from the shallower and deeper parts of the uz may indicate that the nonwelded tuffs ptn located between the welded parts of the tiva canyon and topopah spring tuffs play an important role in moderating uz flow

an example of high pressure low temperature metamorphic rocks from an island arc the paikon series innermost hellenides greece the paikon series is considered to be a volcanic arc sequence with a mainly neritic sedimentary sequence and bimodal tholeiitic volcanism of early mesozoic age the metamorphic assemblages are syn to post kinematic with respect to a pre tithonian tectonic phase and range from the lawsonite chlorite albite facies through transitional na amphibole greenschist facies to the chlorite sub zone of the greenschist facies the metamorphic imprint of the paikon series corresponds to a temperature range from less than 330 c to 450 c under a total pressure from 3 kbar to 6 7 kbar the overprinting of these facies on an earlier blueschist assemblage related either to a subduction zone or to a tectonic overpressure caused by thrusting is suspected

age spreading rates and spreading asymmetry of the world s ocean crust we present four companion digital models of the age age uncertainty spreading rates and spreading asymmetries of the world s ocean basins as geographic and mercator grids with 2 arc min resolution the grids include data from all the major ocean basins as well as detailed reconstructions of back arc basins the age spreading rate and asymmetry at each grid node are determined by linear interpolation between adjacent seafloor isochrons in the direction of spreading ages for ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated by geological estimates of the ages of passive continental margin segments the age uncertainties for grid cells coinciding with marine magnetic anomaly identifications observed or rotated to their conjugate ridge flanks are based on the difference between gridded age and observed age the uncertainties are also a function of the distance of a given grid cell to the nearest age observation and the proximity to fracture zones or other age discontinuities asymmetries in crustal accretion appear to be frequently related to asthenospheric flow from mantle plumes to spreading ridges resulting in ridge jumps toward hot spots we also use the new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using three alternative age depth relationships the new set of grids helps to investigate prominent negative depth anomalies which may be alternatively related to subducted slab material descending in the mantle or to asthenospheric flow a combination of our digital grids and the associated relative and absolute plate motion model with seismic tomography and mantle convection model outputs represents a valuable set of tools to investigate geodynamic problems

inorganic calcite morphology roles of fluid chemistry and fluid flow abstract evaluation of calcite crystal habits and fabric and their relation to precipitating fluids in spelean environments indicates that habit variations are controlled primarily by degree of supersaturation at less than 6 times supersaturation crystal habits are limited to those with shallow to steep rhombohedral forms i e 1011 4041 with increasing supersaturation scalenohedrons extremely steep rhombohedrons pinacoids and hexagonal prisms are developed slight elongation due to differences in crystal dimensions of these forms may arise i e scalenohedrons versus shallow rhombohedrons at extreme supersaturation 12 times curvature of crystal faces or curved surfaces appear the development of fibrous versus equant fabrics is the result of changes or modification of reactant supply rates and the number of crystallites nuclei present under rapid flow conditions growth rates are accelerated and greater numbers of nuclei are present thus compromise boundaries parallel to c axis and perpendicular to flow and substrate are rapidly attained in the absence of flow fewer crystallites are present and larger well developed crystals or branching forms dictated by saturation conditions arise in the absence of flow at low supersaturation elongate composite crystals and hence fibrous fabrics may result from migration of the fluid crystal interface as a result of changing or oscillating water levels a flow control mechanism can be applied to numerous geological conditions in which transitions from fibrous to equant crystal morphologies are observed

example of ensialic ophiolites emplaced in a wrench zone innermost hellenic ophiolite belt greek macedonia the innermost hellenic ophiolite belt of northern greece comprises discontinuous ophiolites of the guevgueli and chalkidiki complexes field structural chemical and geochronological data indicate that they are broadly autochthonous and were emplaced into continental crust along a northwest southeast wrench zone during the middle and late jurassic variations in structure and petrology along the belt can be related to changes in the tectonics of emplacement from extensional to transcurrent

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

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

the three metamorphic belts of the hellenides a review and a kinematic interpretation summary new results obtained in the three metamorphic belts of the hellenides suggest that each belt has a different structure geotectonic setting and evolution the external metamorphic belt of peloponnesus crete has probably resulted from nappe movement in the vicinity of an evolving island arc system the blueschists occurring within this external belt are allochthonous and have been transported with other nappes over the external carbonate platform of the pre apulian plattenkalk ionian tripolitza almyropotamos units this implies that there was only one true blueschist domain initiated in the cycladic area during early eocene the kinematic interpretation is based on the distinction of a and b structures and on the nature of the shear zones between the different domains especially that between the metamorphic hellenides below and the non metamorphic hellenides above the existence of the probably lower palaeozoic meta sedimentary sequence of kastoria in the northern pelagonian zone indicates that the overlying ophiolite bearing almopias unit has been derived from within the hercynian domain the kastoria sedimentary sequence the ophiolites of vertiskos and the carbonate platform of pangeon are considered to be most likely elements of a probable hercynian orogeny

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

sedimentary geology as a key to understanding the tectonic evolution of the mesozoic early tertiary paikon massif vardar suture zone n greece abstract this paper demonstrates how sedimentary evidence can provide a key to elucidating the regional tectonic and palaeoceanographic significance of a complex partly metamorphic terrane in this case the paikon massif the paikon massif is located centrally within the vardar axios zone of n greece and is critical to the reconstruction of neotethys in the e mediterranean region the massif is here restored as a single tectono stratigraphic unit of jurassic to early tertiary age that originated along the margin of a continental unit known as the serbo macedonian zone in this area a mesozoic oceanic basin the almopias ocean opened in the triassic between the serbo macedonian continent to the ne and another continental unit the pelagonian zone to the sw initial deep water deposition along the northwesterly passive margin of the almopias ocean is represented within the paikon massif by metamorphosed redeposited carbonates and hemipelagic sediments gandatch formation above this the jurassic paikon volcanic group comprises two volcanogenic units of island arc type livadia and kastaneri formations the arc developed along the sw margin of the serbo macedonian continent in response to ne subduction of the almopias ocean the subduction also resulted in the opening of a related back arc basin in mid late jurassic represented by the guevgueli ophiolite now to the ne of the paikon massif the massif underwent ductile deformation and inferred hp lt metamorphism during late jurassic time related to subduction beneath the serbo macedonian active margin exhumation took place rapidly by kimmeridgian time followed by a shallow water transgression khromni limestones subsequent emergence and fluvial deposition ghrammos formation reflect a regional extensional or transtensional event following a marine transgression influenced by eustatic sea level rise and tectonic subsidence aptian albian a carbonate platform developed throughout the paikon massif cretaceous transgressive limestones short lived emergence turonian was followed by deepening in the campanian maastrichtian and pelagic carbonate deposition buff pelagic carbonates overlying terrigenous turbidites tchouka flysch form part of an early tertiary foredeep in a regional contractional setting late stage shortening resulted in bivergent thrusting and folding to form the paikon massif as a large anticlinal pop up structure near the axis of the suture zone localised transpression and neotectonic extension complete the picture

when and where did india and asia collide timing of the collision between india and asia is the key boundary condition in all models for the evolution of the himalaya tibetan orogenic system thus it profoundly affects the interpretation of the rates of a multitude of associated geological processes ranging from tibetan plateau uplift through continental extrusion across eastern asia as well as our understanding of global climate change during the cenozoic although an abrupt slowdown in the rate of convergence between india and asia around 55 ma is widely regarded as indicating the beginning of the collision most of the effects attributed to this major tectonic episode do not occur until more than 20 ma later refined estimates of the relative positions of india and asia indicate that they were not close enough to one another to have collided at 55 ma on the basis of new field evidence from tibet and a reassessment of published data we suggest that continent continent collision began around the eocene oligocene boundary 34 ma and propose an alternative explanation for events at 55 ma

variable anelastic attenuation and site effect in estimating source parameters of various major earthquakes including m w 7 8 nepal and m w 7 5 hindu kush earthquake by using far field strong motion data strong motion records of recent gorkha nepal earthquake m w 7 8 its strong aftershocks and seismic events of hindu kush region have been analysed for estimation of source parameters the m w 7 8 gorkha nepal earthquake of 25 april 2015 and its six aftershocks of magnitude range 5 3 7 3 are recorded at multi parametric geophysical observatory ghuttu garhwal himalaya india 600 km west from the epicentre of main shock of gorkha earthquake the acceleration data of eight earthquakes occurred in the hindu kush region also recorded at this observatory which is located 1000 km east from the epicentre of m w 7 5 hindu kush earthquake on 26 october 2015 the shear wave spectra of acceleration record are corrected for the possible effects of anelastic attenuation at both source and recording site as well as for site amplification the strong motion data of six local earthquakes are used to estimate the site amplification and the shear wave quality factor q at recording site the frequency dependent q f 124f 0 98 is computed at ghuttu station by using inversion technique the corrected spectrum is compared with theoretical spectrum obtained from brune s circular model for the horizontal components using grid search algorithm computed seismic moment stress drop and source radius of the earthquakes used in this work range 8 20 1016 5 72 1020 nm 7 1 50 6 bars and 3 55 36 70 km respectively the results match with the available values obtained by other agencies