relocation and assessment of seismicity in the iran region summary more than 2000 instrumentally recorded earthquakes occurring in the iran region during the period 1918 2004 have been relocated and reassessed with special attention to focal depth using an advanced technique for 1 d earthquake location a careful review of starting depths association of teleseismic depth phases and the effects of reading errors on these phases are made and when necessary waveforms have been examined to better constrain ehb focal depths uncertainties in ehb epicentres are on the order of 10 15 km in the iran region owing to the earth s lateral heterogeneity and uneven station distribution uncertainties of reviewed ehb focal depth estimates are on the order of 10 km as compared to about 4 km for long period p and sh body waveform inversions nevertheless these ehb depth estimates are sufficiently accurate to resolve robust differences in focal depth distribution throughout the iran region and within their errors show patterns that are in agreement with the smaller number of earthquakes whose depths have been confirmed by body wave modelling or local seismic networks the importance of this result is that future earthquakes with apparently anomalous depths can easily be identified and checked if necessary most earthquakes in the iranian continental lithosphere occur in the upper crust with the crustal shortening produced by continental collision accommodated entirely by thickening and distributed deformation in the zagros mountains nearly all earthquakes are confined to the upper crust depths 20 km and there is no evidence for a seismically active subducted slab dipping ne beneath central iran by contrast in southeastern iran where the arabian seafloor is being subducted beneath the makran coast low level earthquake activity occurs in the upper crust as well as to depths of at least 150 km within a northward dipping subducting slab near the oman line a region transitional between the zagros and the makran seismicity extends to depths of up to 30 45 km in the crust consistent with low angle thrusting of arabian basement beneath central iran in north central iran along the alborz mountain belt seismic activity occurs primarily in the upper crust but with some infrequent events in the lower crust particularly in the western part of the belt the talesh where the south caspian basin underthrusts nw iran earthquakes that occur in a band across the central caspian following the apscheron balkhan sill between azerbaijan and turkmenistan have depths in the range 30 100 km deepening northwards these are thought to be connected with either incipient or remnant northeast subduction of the south caspian basin basement beneath the east west trending apscheron balkhan sill curiously in this region of genuine mantle seismicity there is no evidence for earthquakes shallower than 30 km

shallow creep on the haiyuan fault gansu china revealed by sar interferometry interferometric synthetic aperture radar data are used to map the interseismic velocity field along the haiyuan fault system hfs at the north eastern boundary of the tibetan plateau two m 8 earthquakes ruptured the hfs in 1920 and 1927 but its 260 km long central section known as the tianzhu seismic gap remains unbroken since 1000 years the envisat sar data spanning the 2003 2009 period cover about 200 300 km2 along three descending and two ascending tracks interferograms are processed using an adapted version of roi pac the signal due to stratified atmospheric phase delay is empirically corrected together with orbital residuals mean line of sight velocity maps are computed using a constrained time series analysis after selection of interferograms with low atmospheric noise these maps show a dominant left lateral motion across the hfs and reveal a narrow 35 km long zone of high velocity gradient across the fault in between the tianzhu gap and the 1920 rupture we model the observed velocity field using a discretized fault creeping at shallow depth and a least squares inversion the inferred shallow slip rate distribution reveals aseismic slip in between two fully locked segments the average creep rate is 5 mm yr 1 comparable in magnitude with the estimated loading rate at depth suggesting no strain accumulation on this segment the modeled creep rate locally exceeds the long term rate reaching 8 mm yr 1 suggesting transient creep episodes the present study emphasizes the need for continuous monitoring of the surface velocity in the vicinity of major seismic gaps in terms of seismic hazard assessment

the drenchwater deposit alaska an example of a natural low ph environment resulting from weathering of an undisturbed shale hosted zn pb ag deposit abstract the drenchwater shale hosted zn pb ag deposit and the immediate vicinity on the northern flank of the brooks range in north central alaska is an ideal example of a naturally low ph system the two drainages drenchwater and false wager creeks which bound the deposit differ in their acidity and metal contents moderately acidic waters with elevated concentrations of metals ph 4 3 zn 1400 g l in the drenchwater creek drainage basin are attributed to weathering of an exposed base metal rich massive sulfide occurrence stream sediment and water chemistry data collected from false wager creek suggest that an unexposed base metal sulfide occurrence may account for the lower ph 2 7 3 1 and very metal rich waters up to 2600 g l zn 260 g l cu and 89 g l tl collected at least 2 km upstream of known mineralized exposures these more acidic conditions produce jarosite schwertmannite and fe hydroxides commonly associated with acid mine drainage the high metal concentrations in some water samples from both streams naturally exceed alaska state regulatory limits for freshwater aquatic life affirming the importance of establishing base line conditions in the event of human land development the studies at the drenchwater deposit demonstrate that poor water quality can be generated through entirely natural weathering of base metal occurrences and possibly unmineralized black shale

the southern caspian a compressional depression floored by a trapped modified oceanic crust the south caspian intracontinental depression floored by oceanic basement is a relatively stable block with minor deformation surrounded by active fold thrust belts of arcuate form talesh alborz and kopeh dagh mountains which have undergone intense late cainozoic crustal shortening the basin is interpreted as a neogene quaternary compressional depression bounded by multi role mountain bordering reverse faults and apparently floored by a late paleozoic triassic or late mesozoic early tertiary modified oceanic crust trapped along an old geosuture it may be a relic of an old paleozoic triassic ocean or else a marginal sea developed behind a mesozoic paleogene ocean and analysis of geological and geophysical data enables a scheme to be suggested the general arcuate shape of the alborz and the talesh bordering mountain belts follows the pattern of the supposed rigid and thickened ocean crust of south caspian depression a tectono sedimentary study of the south caspian region coupled w

on diagenesis dolomitisation and mineralisation in the irish zn pb orefield marine calcite cementation and lithification of carboniferous carbonate sediments hosting zn pb mineralisation in the irish orefield occurred at or near the seafloor a relatively early fine grained grey replacive dolomite preferentially developed in micrite is widely developed in the waulsortian limestone formation the main host to mineralisation and is pervasive in the southeastern midlands in proximity to the leinster massif this dolomite formed after the first four main stages of calcite cementation but probably also developed within tens of metres of the seafloor as evidenced by incorporation of clasts of dolomite in intraformational sedimentary breccias later coarse grained white dolomite preferentially replaced coarser components of the waulsortian limestone and infilled residual vuggy porosity whilst some of this coarse dolomite may be related to the fine replacive dolomite event a common spatial association with fault zones coupled with primary fluid inclusion data suggest that a significant proportion of this phase precipitated during the onset of fault controlled subsidence and widespread hydrothermal circulation within the irish midlands area fluids up to 250 c and 10 15 wt nacl equivalent sourced from a lower palaeozoic basement equilibrated fluid reservoir infiltrated the carbonate sequence via faults and fractures the more localised development of dolomite cemented breccias white matrix breccias that are frequently associated spatially with mineralisation was a consequence of the increased focusing of these hydrothermal fluids ore formation was broadly synchronous with development of the white dolomite breccias but only happened where mixing occurred between the hydrothermal ore fluids and localised near surface reservoirs of low temperature h2s rich brine in the waulsortian this process led to the precipitation of a distinctive black dolomite that forms a broad halo to massive sulphides although ore stage sulphides postdate significant diagenesis of the host rocks and often display epigenetic textures the fact that much of the cementation occurred soon after carbonate deposition means that mineralisation does not have to have formed after significant burial in fact the occurrence of clasts of hydrothermal dolomite and sulphides in intraformational debris flow breccias is only consistent with mineralising processes occurring in the near seafloor environment relatively soon after host rock deposition the regional development of a distinctive pink dolomite associated with faults and fractures was a post ore event and is considered to mark a regional brine migration linked to the onset of the variscan orogeny the development of this new tectonic and flow regime may have been responsible for the cessation of economic mineralisation in ireland

advection of fluids at the front of the sicilian neogene subduction complex abstract the sicilian accretionary prism shows a large southward imbricated system of thrust sheets the frontal part of the belt has been tectonically emplaced in plio pleistocene times major decollement surfaces and sole thrusts at the base of and inside the prism consist of melanges with a blocks in matrix fabric in the frontal part two superposed decollement levels are recognized the upper one located at the base of the paleogene neogene sedimentary series and the basal one at the base of duplexes triassic miocene sedimentary series syntectonic dewatering of the sedimentary sections occurred along decollements and thrust faults involving hydrofracture and mineralized vein development inside the deep sole thrusts rooted in the basal decollement hydrofractured blocks show different generations of syntectonic quartz and calcite extensional veins while in the upper decollement only calcite veins have been observed both quartz and calcite veins show aqueous primary fluid inclusions of low salinity with low trapping temperature for fluids in the upper decollement if we assume that at the time of deformation the main heat source was the regional conductive geothermal gradient the trapping temperatures of the fluids inside veins of the deep sole thrusts are higher than those predicted by the pilo pleistocene gradient for this subduction zone and correspond to a thermal anomaly we suggest that the frontal sicilian prism supported localized transient fluid flow of deep freshwater sourced from two different origins a shallow one for fluids now trapped in the upper decollement and a deep internal origin 6 10 km minimum depth for the hot fluids channelized along the basal decollement and now trapped inside the sole thrust of the mt scalpello duplex area

controls on stylolite development morphologic lithologic and temporal evidence from bedding parallel and transverse stylolites from the u s appalachians quantification of morphology of bedding parallel and transverse or tectonic stylolites from the southern appalachians reveals that regardless of tectonic setting or stylolite orientation lithologic heterogeneity controls stylolite development for example stylolites in more heterogeneous carbonate lithologies packstones and grainstones are more serrate than those in wackestones and mudstones similarly early forming stylolites are more serrate than late forming stylolites and computer simulations suggest that decreases in porosity or other lithologic heterogeneity cause the less serrate nature of late forming stylolites the linkage of a stylolite s morphology to its time of development should allow field estimation of timing of stylolitization and thus of timing of loading or compression although bedding parallel and transverse stylolites generally result from different kinds of compression morphological relations indicate that their development follows the same fundamental patterns bedding

geophone ground coupling for frequencies much lower than the coupling resonant frequency the geophone accurately follows the ground motion but for higher frequencies the coupling can alter both the amplitude and phase of the seismic signal the normal planting of vertical geophones in the field results in coupling adequate for conventional recording that uses frequencies less than 100 hz however for very loose soils or for high frequency seismic recording i recommend that the geophones be buried to place the geophones in firmer soil the coupling resonant frequency for vertical geophones is determined by the firmness of the soil and i have measured resonant frequency ranging from 100 to 500 hz at different locations because the firmness of the soil increases with depth the coupling resonant frequency can be increased by burial of the geophones or by the use of longer spikes the rocking of horizontal geophones causes a low frequency coupling resonance it is crucial that horizontal geophones be planted with their bases firmly contacting the soil geophones so planted have a resonance around 130 hz whereas those 1 cm off the ground can have a resonance of 30 hz or lower soil conditions have little effect on the resonant frequency horizontal geophones with 1 inch spikes are as well coupled as those with longer spikes but the best coupling is achieved by burial of the geophones modified journal abstract

gps and gravity constraints on continental deformation in the alborz mountain range iran a network of 54 survey gps sites 28 continuous gps stations and three absolute gravity ag observation sites have been set up in the alborz mountain range to quantify the present day kinematics of the range our results allow us to accurately estimate the motion of the south caspian block scb for the first time and indicate rotation of the scb relative to eurasia accounting for the left lateral motion in the alborz range in light of these new results it clearly appears that deformation rates vary along the range the eastern part accommodating mainly left lateral strike slip 2 mm yr 1 south of the range and 5 mm yr 1 north of the range with a very low range normal shortening rate on the khazar thrust fault similar to 2 mm yr 1 and the western part accommodating range normal shortening similar to 6 mm yr 1 on the khazar thrust fault with a left lateral component of similar to 2 mm yr 1 north of the range and 1 mm yr 1 south of the range these present day kinematics agree with geomorphologic estimated slip rates but not the long term deformation corroborating the idea that the kinematics of the range have changed recently due to the change of scb motion modelling of the interseismic deformation suggests a deep locking depth on the central western segment of the khazar fault similar to 30 km in agreement with the baladeh earthquake rupture and aftershock ranging between 10 and 30 km given this unusual deep locking depth and the 34 degrees dip of the thrust a large part of the alborz range is located above the seismically coupled part of the fault based on our ag measurements this part of the range seems to uplift at a rate of 1 5 mm yr 1 in agreement with terrace uplift

interseismic deformation of the shahroud fault system ne iran from space borne radar interferometry measurements the shahroud fault system is a major active structure in the alborz range of ne iran whose slip rate is not well constrained despite its potential high seismic hazard in order to constrain the slip rate of the eastern shahroud fault zone we use space borne synthetic aperture radar interferometry with both ascending and descending envisat data to determine the rate of interseismic strain accumulation across the system we invert the slip rate from surface velocity measurements using a half space elastic dislocation model the modeling results are consistent with a left lateral slip rate of 4 75 0 8 mm yr on the abr and jajarm strands of the shahroud fault with a 10 4 km locking depth this is in good agreement with the 4 6 mm yr of left lateral displacement rate accumulated across the total shahroud fault system obtained from gps measurements

characterization and imaging of a hydrothermally active near vertical fault zone in crystalline rocks based on hydrophone vsp data abstract a shallow hydrothermally active fault zone embedded in fractured crystalline rocks of the central swiss alps has been drilled and geophysically explored in view of its potential analogies to planned petrothermal reservoirs in the alpine foreland vertical seismic profiling vsp experiments have been performed using a 24 channel borehole hydrophone array with a sensor spacing of 1 m in order to image the fault core and to detect hydraulically open fractures the dense sensor spacing allows for an accurate sampling of the wavefields this in turn enables their separation through standard seismic processing methodologies thus allowing for the generation of seismic body wave vsp profiles and a tube wave corridor stack which maps brittle deformation in the surrounding rock mass multiple offset hydrophone vsp data were acquired with a crooked line survey geometry and processed with 3d methods hereby a laterally changing velocity cube representative of the vertical structural variations associated with the fault zone is generated and utilized for kirchhoff pre stack depth migration psdm imaging the resulting seismic image delineates various vertical structures notably the target fault zone the interpretation of the vsp data is complemented by and corroborated through a suite of geophysical borehole logs which characterize the fine scale petrophysical variations in response to brittle deformation in the fault core and the surrounding damage zones this study exemplifies typical targets of hardrock seismic exploration where the structures are frequently near vertical discontinuous and where acoustic impedance contrasts are commonly associated with deformation as such it illustrates the benefits of using borehole seismic methods in such environments and the use of borehole hydrophone arrays for targeting fractures and shear zones

extrusion tectonics and subduction in the eastern south caspian region since 10 ma reply we examine active deformation of the region surrounding the eastern south caspian sea using a combination of seismic geological geodetic and geomorphological data global positioning system gps velocities indicate a westward component of motion of the south caspian basin relative to eurasia and central iran we identify major zones of shear the ashkabad and shahrud fault zones that accommodate this westward extrusion on either side of the south caspian block estimates of total strike slip motion could at present day slip rates derived from gps observations be achieved in 10 m y therefore the northwest extrusion of the south caspian region which is accommodated by subduction beneath the north caspian region stable eurasia along the apsheron balkan sill may also date from that time this suggests that the onset of subduction may be older than previous estimates ranging from 1 8 to 5 5 ma our results are summarized in a new kinematic model that significantly clarifies the active tectonics of this complicated region

shallow seismic reflection mapping of the overburden bedrock interface with the engineering seismograph some simple techniques where unconsolidated overburden exceeds 20 m in thickness the reflection method may be efficiently used with a 12 channel engineering seismograph to map topography on the overburden bedrock interface as well as possible structure within the overburden the two techniques we suggest are the simplest forms of reflection profiling which can be applied with a minimum amount of equipment which we suggest is a 12 channel enhancement seismograph a 12 geophone array and a hammer source these techniques require good transmission characteristics of the overburden as well as a sharp velocity discontinuity at the overburden bedrock interface for data processing and display a microcomputer is essential

vertical hydrophone cable acquisition and imaging on land we acquired seismic data using a vertical hydrophone cable in a shallow fluid filled borehole over the blackfoot oil field in alberta canada the hydrophone data were recorded simultaneously with a surface seismic survey using dynamite sources in addition buried three component 3 c geophone data were acquired near the vertical cable we observe that events on the hydrophone records are in phase with corresponding geophone data tube waves which can be a problem on hydrophone data are suppressed using a predictive deconvolution operator imaging using the hydrophone data results in a section that correlates well with a surface seismic image from vertical component geophone data an anomaly interpreted to be associated with the sand reservoir in the area is evident on the hydrophone image as well as on the surface seismic sections the vertical hydrophone cable promises excellent imaging potential for land applications

hydrophone vsp surveys in hard rock abstractseismic imaging in hard rock environments is gaining wider acceptance as an exploration technique and as a mine planning tool to date 13 successful case studies have been acquired in australia the images generated from hard rock targets exhibit large levels of complexity and their interpretations remain an active area of study to assist the imaging and better understand the source of the reflections observed vertical seismic profiling vsp can be employed this technique is not readily applied to hard rock environments because cost and operational issues often prove prohibitive we propose the use of hydrophone arrays as a cost effective solution to vsp acquisition we highlight the key challenges in using these receivers and propose solutions to overcome them by careful acquisition methodologies and refined signal processing techniques the tube waves that have up to now compromised the use of hydrophones for vsp acquisition can be effectively mitigated we show that the data acquired with

tracing element sources of hydrothermal mineral deposits ree and y distribution and sr nd pb isotopes in fluorite from mvt deposits in the pennine orefield england fluorite from mississippi valley type mvt deposits in the south pennine orefield england displays significantly different distributions of rare earths and yttrium rey compared to fluorite from similar mvt deposits in the north pennine orefield samples from the south pennine orefield display negative ce and positive gd and y anomalies but lack any eu anomaly indicating that the rey were mobilized from relatively pure marine sedimentary carbonates in marked contrast fluorite from the north pennine orefield lacks any ce and gd anomalies but shows a pronounced positive eu anomaly suggesting that the rey were provided by different source rock s that the mineralizing hydrothermal fluid had experienced higher temperatures prior to fluorite precipitation and that it was derived from deeper crustal levels in the north compared to the south the isotopic composition of sr in blue john fluorite from the south pennine orefield suggests that sr was mobilized from lower carboniferous tournaisian limestones whereas pb isotopes suggest that in contrast to rey and sr pb was derived from aluminosilicate rocks neither nd nor sr or pb isotopes can be used to radiometrically date the formation of blue john fluorite all isotope systems studied indicate that the limestone host rock of this fluorite mineralization did not contribute to the trace element budget of the hydrothermal fluid our results show that different solutes in a natural water hydrothermal fluid groundwater etc may be derived from different sources and that the study of a small set of elements or isotope ratios may not provide full insight into the genesis or history of a mineralization or a hydrothermal fluid our data provide evidence for the uncoupling of sr nd and pb during fluid rock interaction and fluid migration and show that the use of plots such as 87sr 86sr vs end to learn about mixing relationships as is commonly done in igneous geochemistry is unreliable when applied to natural waters and their precipitates

time dependent land uplift and subsidence in the santa clara valley california from a large interferometric synthetic aperture radar data set 1 we invert 115 differential interferograms derived from 47 synthetic aperture radar sar scenes for a time dependent deformation signal in the santa clara valley california the time dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between sar scene acquisitions a nonlinear range change signal is extracted from the ers insar data without imposing a model of the expected deformation in the santa clara valley cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of sunnyvale uplift is also observed east of san jose seasonal uplift and subsidence dominate west of the silver creek fault near san jose with a maximum peak to trough amplitude of 35 mm the pattern of seasonal versus long term uplift provides constraints on the spatial and temporal characteristics of water bearing units within the aquifer the silver creek fault partitions the uplift behavior of the basin suggesting that it acts as a hydrologic barrier to groundwater flow while no tectonic creep is observed along the fault the development of a low permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of quaternary units

active transtension inside central alborz a new insight into northern iran southern caspian geodynamics the tectonic activity in the alborz mountain range northern iran is due both to the northward convergence of central iran toward eurasia and to the northwestward motion of the south caspian basin with respect to eurasia inducing a left lateral wrenching along this range these two mechanisms give rise to a nne ssw transpressional regime which is believed to have affected the entire range for the last 5 6 2 m y in this paper we show that the internal domain of central alborz is not affected by a transpressional regime but by an active transtension with a wnw ese extensional axis we show that this transten sion is young middle pleistocene it postdates an earlier n s compression and may have been initiated when the south caspian basin started moving consequently our results suggest that the south caspian basin motion may have taken place more recently than previously proposed

the post eocene evolution of the doruneh fault region central iran the intraplate response to the reorganization of the arabia eurasia collision zone

near surface vsp surveys using the seismic cone penetrometer we have found that high quality vertical seismic profile vsp data can be collected for near surface applications using the seismic cone penetrometer cone mounted accelerometers are used as the vsp receivers and a sledgehammer against the cone truck baseplate is used as a source this technique eliminates the need to drill a borehole thereby reducing the cost of the survey and results in a less invasive means of obtaining vsp data two sh wave vsp surveys were acquired over a deltaic sand silt sequence and compared to an sh wave common depth point cdp reflection profile the vsp data were processed using a combination of singular value decomposition filtering deconvolution and f k filtering to produce the final vsp extracted traces the vsp traces correlate well with cone geotechnical logs and the cdp surface seismic data the first breaks from the vsp can be used to generate shear wave velocity profiles that are important for time to depth conversion and the velocity correction of the cdp surfac

the 1994 sefidabeh eastern iran earthquakes revisited new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault in 1994 three shallow earthquakes of mw 6 occurred close together on blind thrusts near sefidabeh in eastern iran in an earlier study of the teleseismic waveforms the geomorphology and the faulting in the epicentral region it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system whose activity could be detected by its effect on the surface drainage in this study we present a sar interferogram that precisely determines the location and amount of coseismic surface displacements showing that the earthquakes in the sefidabeh sequence probably occurred on en echelon fault segments associated with three stepping ridges we also present u th dates of 100 ka for lake deposits uplifted by the growing ridge from the cumulative dated uplift and knowledge of the surface displacements due to an earthquake sequence we estimate that 120 such events have occurred in the past 100 ka with an average recurrence interval of 830 yr and an average convergence rate of 1 5 mm yr 1 on the sefidabeh thrust each estimate has an uncertainty of a factor of two either way we argue that the sefidabeh fault originally formed by coalescence of many small fault segments and has grown in length at about 2 cm yr 1 in the past 100 ka though the coseismic surface deformation observed in the sar interferogram closely resembles folding the overall topography does not because of inherited topography associated with earlier geological deformation in spite of this the activity of the buried thrust fault can easily be detected by its effect on the surface drainage a significant lesson when interpreting landscapes that are not entirely due to the present day deformation

an examination of tube wave noise in vertical seismic profiling data tube waves act as noise that camouflages upgoing and downgoing body wave events which are the fundamental seismic data measured in vertical seismic profiling vsp in two onshore vertical seismic profiles the principal source of tube waves is shown to be surface ground roll that sweeps across the well head secondary tube wave sources revealed in these vsp data are the downhole geophone tool itself and the bottom of the borehole body wave signals are also shown to create tube waves when they arrive at significant impedance contrasts in the borehole such as changes in casing diameter computer simulated vertical geophone arrays are used to reduce these tube waves but such arrays attenuate and filter body wave events unless static time shifts are made so that the body wave signal occurs at the same two way time at each geophone station consequently actual downhole vertical geophone arrays are not an effective means by which tube waves can be eliminated power spectra comparisons of tube wave and compr

multistory duplexes with forward dipping roofs north central brooks range alaska the endicott mountains allochthon has been thrust far northward over the north slope parautochthon in the northern brooks range progressively younger units are exposed northward within the allochthon to the south the incompetent hunt fork shale has thickened internally by asymmetric folds and thrust faults northward the competent kanayut conglomerate forms a duplex between a floor thrust in hunt fork and a roof thrust in the kayak shale to the north the competent lisburne group forms a duplex between a floor thrust in kayak and a roof thrust in the siksikpuk formation both duplexes formed from north vergent detachment folds whose steep limbs were later truncated by south dipping thrust faults that only locally breach immediately overlying roof thrusts within the parautochthon the kayak lisburne and siksikpuk equivalent echooka formation form a duplex identical to that in the allochthon this duplex is succeeded abruptly northward by detachment folds in lisburne these folds are parasitic to an anticlinorium interpreted to reflect a fault bend folded horse in north slope basement with a roof thrust in kayak and a floor thrust at depth these structures constitute two northward tapered internally deformed wedges that are juxtaposed at the base of the allochthon within each wedge competent units have been shortened independently between detachments located mainly in incompetent units the basal detachment of each wedge cuts upsection forward northward to define a wedge geometry within which units dip regionally forward these dips reflect forward decrease in internal structural thickening by forward vergent folds and hindward dipping thrust faults

high ree and y concentrations in co cu au ores of the blackbird district idaho analysis of 11 samples of strata bound co cu au ore from the blackbird district in idaho shows previously unknown high concentrations of rare earth elements ree and y averaging 0 53 wt percent ree y oxides scanning electron microscopy indicates ree and y residence in monazite xenotime and allanite that form complex intergrowths with cobaltite suggesting coeval co and ree y mineralization during the mesoproterozoic occurrence of high ree and y concentrations in the blackbird ores together with previously documented saline rich fluid inclusions and cl rich biotite suggest that these are not volcanogenic massive sulfide or sedimentary exhalative deposits but instead are iron oxide copper gold iocg deposits other strata bound co deposits of proterozoic age in the north american cordillera and elsewhere in the world may have potential for ree and y resources iocg deposits with abundant light ree should also be evaluated for possible unrecognized heavy ree and y mineralization

cementation hydrothermal alteration and zn pb mineralization of carbonate breccias in the irish midlands textural evidence from the cooleen zone near silvermines county tipperary a reply sir we are delighted to respond to the comments of reed and wallace on our paper on the origin of breccia hosted base metal mineralization in the irish ore field lee and wilkinson 2002 reed and wallace s thesis is that the mineralized breccias we have described within the mississippian waulsortian limestone formation at cooleen are not of sedimentary origin and therefore by extension that synsedimen tary breccias do not exist elsewhere in the ore field if correct one of a number of lines of evidence that have been used to infer a near sea floor origin for at least a component of sulfide mineralization in ireland that of reworked clasts of sulfide within sedimentary breccias would be invalidated contrary to the suggestion of reed and wallace the existence of sedimentary breccias spatially associated with mineralization in the waulsortian is universally accepted in the literature mine based investigations that include underground observations as well as drill core data and sedimentological studies have concluded that the stratiform wedge shaped breccia bodies commonly developed within the waulsortian limestone facies are sedimentary debris flows of courceyan age boyce et al 1983 taylor 1984 andrew 1986 clifford et al 1986 somerville et al 1992 submarine fault scarp sedimentary breccias are common in sediment hosted zn pb deposits e g goodfellow et al 1993 and display the same characteristics as the breccias at cooleen hitzman and beaty 1996 p 125 also recognized that synsedimentary breccias are present within the waulsortian at both silvermines and lisheen but went on to state that textural and field relationships clearly show that the principal episode of brecciation postdated regional burial dolomiti zation inferring a hydrothermal origin for the ore hosting breccias while we would not agree with this conclusion particularly in relation to the silvermines area we accept that the ore hosting breccias at lisheen galmoy and silvermines have been

multi interferogram method for measuring interseismic deformation denali fault alaska summary studies of interseismic strain accumulation are crucial to our understanding of continental deformation the earthquake cycle and seismic hazard by mapping small amounts of ground deformation over large spatial areas insar has the potential to produce continental scale maps of strain accumulation on active faults however most insar studies to date have focused on areas where the coherence is relatively good e g california tibet and turkey and most analysis techniques stacking small baseline subset algorithm permanent scatterers etc only include information from pixels which are coherent throughout the time span of the study in some areas such as alaska where the deformation rate is small and coherence very variable it is necessary to include information from pixels which are coherent in some but not all interferograms we use a three stage iterative algorithm based on distributed scatterer interferometry we validate our method using synthetic data created using realistic parameters from a test site on the denali fault alaska and present a preliminary result of 10 5 5 0 mm yr 1 for the slip rate on the denali fault based on a single track of radar data from ers1 2

zinc isotopes in sphalerite from base metal deposits in the red dog district northern alaska analyses of sphalerite samples from shale hosted massive sulfide and stratigraphically underlying vein breccia deposits in the red dog district in northern alaska show a range of 66zn values from zero to 0 60 per mil the lowest values are observed in the vein breccia deposits and the stratigraphically overlying but structurally displaced shale hosted massive sulfide deposits show a systematic trend of increasing 66zn values from south to north main aqqaluk paalaaq anarraaq the 66zn values are inversely correlated with sphalerite fe mn ratio and also tend to be higher in low cu sphalerite consistent with precipitation of lower 66zn sphalerite closer to the principal hydrothermal fluid conduits the most likely control on isotopic variation is rayleigh fractionation during sulfide precipitation with lighter zinc isotopes preferentially incorporated in the earliest sphalerite to precipitate from ore fluids at deeper levels vein breccias and close to the principal fluid conduits in the orebodies followed by precipitation of sulfides with higher 66zn values in shallower and or more distal parts of the flow path there is no systematic variation among the paragenetic stages of sphalerite from a single deposit suggesting an isotopically homogeneous zinc source and consistent transport deposition conditions and or dissolution reprecipitation of earlier sphalerite without significant fractionation decoupled zn and s isotope compositions are best explained by mixing of separate metal and sulfur bearing fluids at the depositional site the results confirm that zn isotopes may be a useful tracer for distinguishing between the central and distal parts of large hydrothermal systems as previously suggested and could therefore be of use in exploration

hydrophone vsp imaging at a shallow site we evaluated the capabilities of vertical seismic profiling vsp for imaging the complex heterogeneous unconsolidated sedimentary structures at a shallow site we deployed a 24 level hydrophone array with 0 5 m level spacing down a preexisting poly vinyl chloride pvc cased well data acquisition time was quick only 15 multioffset shot points using a hammer on plate source were needed to acquire reflection data between the water table at 3 m and the bedrock at 35 m to produce a depth section image this image extended 9 m from the receiver well yielding resolutions between fresh water bearing sands and impermeable muds and clays of better than 1 m depth accuracy of the image was confirmed by good correlation with cone penetrometer logs we used conventional wavefield separation and vsp cdp mapping techniques to image the data tube waves created by seismic arrivals at cross sectional area changes in the borehole fluid column were the primary source of coherent noise in the data the tube wave arriv

reactive surface area control of the dissolution kinetics of biogenic silica in deep sea sediments abstract flow through dissolution experiments demonstrate that the specific reactive surface area of biogenic silica decreases significantly with depth in surficial sediments of the southern ocean specific surface areas obtained from nitrogen gas bet adsorption isotherms however do not exhibit the systematic changes of the specific reactive surface area inferred from the kinetic experiments furthermore the decrease in surface reactivity of the siliceous skeleton fragments continues at depths in the sediments where there is no longer a net release of silicic acid to the pore waters thus the specific reactive surface changes most likely reflect a progressive reduction of the surface density of reactive sites aging during burial rather than the preferential dissolution of a more reactive fraction of siliceous debris deposited from the water column the observed aging of the silica surfaces has important consequences for the benthic regeneration of nutrient silicic acid from deep sea sediments

multistage hydrothermal silicification and fe tl as sb ge ree enrichment in the red dog zn pb ag district northern alaska geochemistry origin and exploration applications geochemical analyses of major trace and rare earth elements ree in more than 200 samples of variably silicified and altered wall rocks massive and banded sulfide silica rock and sulfide rich and unmineralized barite were obtained from the main aqqaluk and anarraaq deposits in the red dog zn pb ag district of northern alaska detailed lithogeochemical profiles for two drill cores at aqqaluk display an antithetic relationship between sio2 al2o3 and tio2 zr which together with textural information suggest preferential silicification of carbonate bearing sediments data for both drill cores also show generally high tl sb as and ge and uniformly positive eu anomalies eu eu 1 0 similar high tl sb as ge and eu eu values are present in the footwall and shallow hanging wall of zn pb ag sulfide intervals at anarraaq but are not as widely dispersed net chemical changes for altered wall rocks in the district on the basis of average al normalized data relative to unaltered black shales of the host kuna formation include large enrichments 50 of fe ba eu v s co zn pb tl as sb and ge at both red dog and anarraaq si at red dog and sr u and se at anarraaq large depletions 50 are evident for ca at both red dog and anarraaq for mg p and y at red dog and for na at anarraaq at both red dog and anarraaq wall rock alteration removed calcite and minor dolomite during hydrothermal decarbonation reactions and introduced si eu and ge during silicification sulfidation reactions deposited fe s co zn pb tl as and sb barite mineralization introduced ba s and sr light ree and u were mobilized locally this alteration and mineralization occurred during mississippian hydrothermal events that predated the middle jurassic cretaceous brookian orogeny early hydrothermal silicification at red dog took place prior to or during massive sulfide mineralization on the basis of the dominantly planar nature of zn pb veins which suggests filling of fractures that developed in previously lithified rock uniformly low ca and mg and uniformly negative ce anomalies in highly siliceous red dog wall rocks reflect hydrothermal decarbonation reactions and pervasive silicification owing to conductive cooling of oxidized metalliferous fluids similar ca and mg depletions are evident at anarraaq but generally lack associated silicification possibly because temperatures of the hydrothermal fluids were too low 180 c or because the thermal contrast between the fluids and wall rocks was smaller owing to the greater depth of alteration and mineralization there compared with red dog chalcophile element anomalies fe zn pb tl as sb in wall rocks at both red dog and anarraq are attributed to sulfidation reactions coeval with subsurface zn pb ag mineralization during the mixing of oxidized metalliferous fluids with h2s rich fluids derived locally within the kuna formation sedimentary wall rocks in the red dog district are characterized by a distinctive suite of geochemical anomalies especially for zn pb tl as sb ge and eu eu at the aqqaluk deposit wall rocks without visible sphalerite or galena 300 ppm zn pb have anomalous eu eu tl sb and as for up to 100 m stratigraphically below zn rich silica rock at anarraaq the tl anomaly is most extensively developed and enrichment relative to unaltered black shale of the kuna formation is present up to 62 m above the highest zn pb sulfide zones the magnitude of the enrichment and systematic behavior of tl in the district make tl a promising geochemical exploration guide for red dog type zn pb ag deposits elsewhere

the 2004 may 28 baladeh earthquake mw 6 2 in the alborz iran overthrusting the south caspian basin margin partitioning of oblique convergence and the seismic hazard of tehran we use teleseismic waveform analysis and locally recorded aftershock data to investigate the source processes of the 2004 baladeh earthquake which is the only substantial earthquake to have occurred in the central alborz mountains of iran in the modern instrumental era the earthquake involved slip at 10 30 km depth with a south dipping aftershock zone also restricted to the range 10 30 km which is unusually deep for iran these observations are consistent with co seismic slip on a south dipping thrust that projects to the surface at the sharp topographic front on the north side of the alborz this line is often called the khazar fault and is assumed to be a south dipping thrust which bounds the north side of the alborz range and the south side of the south caspian basin though its actual structure and significance are not well understood the lack of shallower aftershocks may be due to the thick pile of saturated overpressured sediments in the south caspian basin that are being overthrust by the alborz a well determined earthquake slip vector in a direction different from the overall shortening direction across the range determined by gps confirms a spatial separation partitioning of left lateral strike slip and thrust faulting in the alborz these strike slip and thrust fault systems do not intersect within the seismogenic layer on the north side though they may do so on the south the earthquake affected the capital tehran and reveals a seismic threat posed by earthquakes north of the alborz located on south dipping thrusts as well as by earthquakes on the south side of the range closer to the city

spatial variations in late quaternary slip rates along the doruneh fault system central iran the doruneh fault system dfs is one of the major active strike slip faults in the arabia eurasia collision zone despite its geological activity no large m 6 5 historical or instrumental earthquakes have been recorded along it to date the rate and distribution of slip as well as the seismic behavior of the dfs have been unknown we reconstructed 67 geomorphic offsets recorded by three successive alluvial abandonment surfaces q1 q2 and q3 displaced along the western wfz and central cfz fault zones the determined ages of 12 36 and 120 ka using in situ produced 10 be and 36 cl cosmogenic nuclides for theses surfaces allowed to estimate three sets of individual left lateral slip rates and consequently to describe the spatiotemporal distribution of slip along the cfz and wfz the slip rates averaged over time intervals of 36 and 120 ka reveal variable slip rates along length but similar slip rates at a point with a maximum rate of 8 2 mm yr during the holocene however the fault slip behavior appears more complex with a maximum rate of 5 3 mm yr the cfz is divided into two 4 km apart segments with symmetrical slip distributions relative to a persistent boundary which has not been ruptured over the last 12 ka the maximum length of seismic fault segments varies from 70 to 100 km which could produce earthquakes with a magnitude of m w 7 2 7 4 this emphasizes the necessity of segmentation models for long strike slip faults that may not necessarily rupture along their whole length during a single earthquake

silica and germanium in pacific ocean hydrothermal vents and plumes dissolved silica si and inorganic germanium ge concentrations were measured in hydrothermal fluids from black smoker vents on the east pacific rise 21 n epr and the southern juan de fuca ridge 45 n sjdfr north and south cleft sites axial volcano these typically display end member concentrations ranging from 16 to 23 mm si and 150 to 280 nm ge and end member ge si ratios clustering between 8 and 14 10 6 more than 10 fold greater than the ratio entering the ocean via rivers 0 54 10 6 and being recycled in seawater 0 7 10 6 excess concentrations of dissolved si and ge above oceanic background are observed in mid water hydrothermal plumes over mid ocean ridge mor spreading centers on the southern epr sepr 10 20 s and the sjdfr the largest si and ge concentration anomalies occur over the north cleft segment of the sjdfr these are a factor of three greater than anomalies over the sepr 10 20 s excess ge correlates with excess3he in plumes at a ge 3he molar ratio of about 1 104 approximately the same ratio as in black smokers these observations combined with low abundances of ge in femn rich metalliferous sediments suggest that ge and si behave conservatively in mid ocean ridge hydrothermal plumes a simple ocean si and ge balance constrained by the global river silica flux and ge si ratios in hydrothermal vents rivers and biogenic silica suggests that the global hydrothermal silica flux is about 1 4 1011 mole yr 1 much lower than that estimated from3he either 1 70 80 of the ge flux to the ocean is removed in as yet undiscovered sinks not opal or 2 only 10 of the mantle to ocean3he and heat fluxes is associated with mor hydrothermal convection through the 350 c isotherm 90 is off ridge or 3 the oceanic ge si 3he and87sr86sr balances today are far from steady state

petrographic geochemical and fluid inclusion evidence for the origin of siliceous cap rocks above volcanic hosted massive sulfide deposits at myra falls vancouver island british columbia canada massive sulfides at the myra falls volcanic hosted massive sulfide vhms camp vancouver island british columbia canada are overlain by white chert black chert argillite and siltstone white chert is best developed above the battle orebody where it forms a siliceous caprock 3 5 m thick above the massive sulfides there is a gradational lateral change from white chert above massive sulfides to black chert and unaltered argillite 100 to 150 m south of the battle orebody chert horizons are also located above the ridge and extension ore zones but only minor chert lies above the hw orebody which is instead overlain by a thick argillite sequence the chert and argillite share similar sedimentologic and petrologic features including abundant parallel laminations interbedded turbidites radiolarian rich layers soft sediment deformation scours flame structures and small phosphatic concretions these features indicate that white and black chert formed as a replacement of mudstone rather than as exhalative or biogenic deposits silicification occurred early in the depositional history of the fine grained sediments and was contemporaneous with some ore formation early syndepositional features are still visible in the chert with primary pore spaces such as radiolarian tests filled by silica rutile apatite and minor sulfides displaying open space crystal growth the presence of minor ore clast breccias above the orebody indicates that at least parts of the battle orebody were exposed on the sea floor metal zoning is observed in the cap rock horizon above the battle orebody with higher cu zn and cd contentrations in chert directly above massive sulfides higher pb sb and ag contentrations in black chert at the edge of the siliceous cap rocks and lower metal concentrations in the distal argillite primary fluid inclusions in spherical quartz patches in chert above the battle orebody indicate that hydrothermal fluids passing through sediment were between 135 to 250c and had salinities ranging from 3 0 to 12 1 wt percent nacl equiv these data are similar to those for fluid inclusions measured in quartz interstitial to sulfides in the underlying battle orebody which have temperatures of homogenization ranging from 140 to 250c and salinities from 3 0 to 12 4 wt percent nacl equiv fluid inclusions in the battle orebody display a slight increase in salinity and homogenization temperature with depth which may reflect the overprinting of earlier high temperature stages by cooler fluids as the hydrothermal system waned or varying degrees of mixing between hydrothermal fluids and seawater a minimum depth for deposition of the cap rocks 200 m is estimated based on sedimentologic features such as fine parallel laminations and interbedded sandstone turbidites which indicate deposition below storm wave base greater water depths 1 000 1 500 m are suggested by the lack of evidence of boiling in fluid inclusions low o2 concentrations in the bottom water of the battle basin are suggested by the absence of bioturbation lack of fossils of benthic fauna degree of pyritization values 0 90 elevated zn pb cu cd as sb ag ba and v low fe and mn and v v ni 0 8 in the unaltered argillite paleosea floor reconstructions indicate that the battle and hw orebodies formed in small basins along a northwest trending ridge the finegrained sediments were deposited in depocenters within paleotopographic lows hydrothermal fluid densities estimated from fluid inclusions at myra falls range from 0 88 to 1 05 g cm3 and are higher than for many other vhms deposits however they are close to the density of seawater at 2c and a 2 000 m depth 1 028 g cm3 replacement textures in the siliceous cap rocks above the battle deposit the sheetlike morphology of the siliceous cap rocks and lateral metal zonation indicates that diffuse lateral flow of hydrothermal fluids through the porous sea floor sediments was more important than the buoyant rise of hydrothermal fluids into the water column however buoyant venting during formation of the battle deposit is indicated by positive eu anomalies and elevated metal values in argillite of the battle basin reflecting the wide dispersal of plume particulates the range of fluid densities indicate that the hydrothermal fluids emerging onto the sea floor and flowing laterally through porous sea floor sediments would have varied from buoyant to neutrally buoyant to negatively buoyant

global positioning system constraints on the active tectonics of ne iran and the south caspian region article history we present a velocity field compiled from a network of 27 permanent and 20 campaign gps stations across ne iran this new gps velocity field helps to investigate how arabia eurasia collision deformation is accommodated at the northern boundary of the deforming zone the present day northward motion decreases eastward from 11 mm yr at tehran 52 e to 1 5 mm yr at mashhad 60 e n s shortening across the kopeh dagh binalud and koh e sorkh ranges sums to 4 5 0 5m m yr at longitude 59 e the available gps velocities allow us to describe the rigid body rotation of the south caspian about an euler pole that is located further away than previously thought we suggest that two new stations mavt and mar2 which are sited far from the block boundaries are most likely to indicate the full motion of the south caspian basin these stations suggest that nw motion is accommodated by right lateral slip on the ashkabad fault at a rate of up to 7 mm yr and by up to 4 6 mm yr of summed left lateral slip across the shahroud left lateral strike slip system our new gps results are important for assessing seismic hazard in ne iran which contains numerous large population centers and possesses an abundant historical earthquake record our results suggest that the fault zones along the eastern alborz and western kopeh dagh may accommodate slip at much faster rates than previously thought fully assessing the role of these faults and the hazard that they represent requires independent verification of their slip rates through additional gps measurements and geological fieldwork

theoretical far field radiation from a low frequency horizontal acoustic point force in a vertical borehole a subsurface point body force can be realized using a body force on the axis of a small radius borehole drilled perpendicular to the force this observation originally made by kitsunezaki 1980 is having a significant impact in shear wave logging and may potentially affect downhole seismic sources applying the principle of reciprocity to this finding a horizontal vibration sensor on the axis of a vertical hole will be unaffected by the existence of the hole at low frequencies numerical methods determine both the frequency below which and the offset beyond which borehole related effects are negligible if the shear wavelength is greater than ten times the diameter of the hole and if the measurement is made at least one shear wavelength from the point force then the borehole effects will be minimal

intense silicification of footwall sedimentary rocks in the stockwork alteration zone beneath the brunswick no 12 massive sulphide deposit bathurst new brunswick intensely silicified volcaniclastic mudstones that underlie the brunswick no 12 massive sulphide deposit in northern new brunswick resemble silicified rocks described in the immediate footwall of many ancient and modern massive sulphide deposits the white to grey cryptocrystalline silica in the silicified rocks becomes more common with proximity to the vent and is most abundant immediately below the massive sulphide zone mass balance analysis of altered footwall sedimentary rocks on the 850 m level of the mine shows that sio2 increases up to 300 the high silica enrichment in the feeder zone is consistent with the presence of cherty silica in the massive sulphides and in associated exhalative iron formation coincident with silicification are enrichments in s feot mgo mno cao p2o5 f cl y cu co cr and ni as well as light rare earth elements and eu oxygen isotope analyses of chloritized and silicified footwall sedimentary rocks suggest that the hydrothermal fluid had a 18o composition o

a metamorphosed potassic alteration zone associated with the bleikvassli znpbcu orebody northern norway abstract the bleikvassli zn pb cu deposit is located in amphibolite facies schists and gneisses in the rodingsfjellet nappe complex north norwegian caledonides a microcline gneiss occurs as a lens shaped body up to 250 m thick in the footwall and as small irregular bodies in the hanging wall the microcline gneiss contains 40 75 microcline and is characterized by a spotty texture the footwall microcline gneiss is chemically zoned with highest k 2 o content 10 12 wt and highest alkali to alumina ratio 0 76 in the central part the mica and plagioclase contents increase towards the margins of the gneiss which grades laterally into the surrounding kyanite mica schist the field relations and the chemical composition of the gneiss indicate that the potassium rich protolith formed by addition of alkalies sio 2 and heat to a pelitic sediment the microcline gneiss has thus been interpreted as the central part of a hydrothermal alteration zone associated with the bleikvassli orebody

reactive flow models of the anarraaq zn pb ag deposit red dog district alaska the red dog ore deposit district in the brooks range of northern alaska is host to several high grade shale hosted zn pb deposits due to the complex history and deformation of these ore deposits the geological and hydrological conditions at the time of formation are poorly understood using geological observations and fluid inclusion data as constraints numerical heat and fluid flow simulations of the anarraaq ore deposit environment and coupled reactive flow simulations of a section of the ore body were conducted to gain more insight into the conditions of ore body formation results suggest that the ore body and associated base metal zonation may have formed by the mixing of oxidized saline metal bearing hydrothermal fluids 200 c with reducing hs rich pore fluids within radiolarite rich host rocks sphalerite and galena concentrations and base metal sulfide distribution are primarily controlled by the nature of the pore fluids i e the extent and duration of the hs source forward modeling results also predict the distribution of pyrite and quartz in agreement with field observations and indicate a reaction front moving from the initial mixing interface into the radiolarite rocks heuristic mass calculations suggest that ore grades and base metal accumulation comparable to those found in the field 18 zn 5 pb are predicted to be reached after about 0 3 my for initial conditions 30 ppm zn 3 ppm pb 20 deposition efficiency

near surface seismic traveltime tomography using a direct push source and surface planted geophones information about seismic velocity distribution in heterogeneous near surface sedimentary deposits is essential for a variety of environmental and engineering geophysical applications we have evaluated the suitability of the minimally invasive direct push technology for near surface seismic traveltime tomography geophones placed at the surface and a seismic source installed temporarily in the subsurface by direct push technology quickly acquire reversed multioffset vertical seismic profiles vsps the first arrival traveltimes of these data were used to reconstruct the 2d seismic velocity distribution tomographically after testing this approach on synthetic data we applied it to field data collected over alluvial deposits in a former river floodplain the resulting velocity model contains information about high and low velocity anomalies and offers a significantly deeper penetration depth than conventional refraction tomography using surface planted sources and receivers at the investigated site a combination of refraction seismic and direct push data increases resolution capabilities in the unsaturated zone and enables reliable reconstruction of velocity variations in near surface unconsolidated sediments the final velocity model structurally matches the results of cone penetration tests and natural gamma radiation data acquired along the profile the suitability of multiple rapidly acquired reverse vsp surveys for 2d tomographic velocity imaging of near surface unconsolidated sediments was explored

rapid strain accumulation on the ashkabad fault turkmenistan from atmosphere corrected insar 1 we have measured interseismic deformation across the ashkabad strike slip fault using 13 envisat interferograms covering a total effective timespan of 30 years atmospheric contributions to phase delay are significant and variable due to the close proximity of the caspian sea in order to retrieve the pattern of strain accumulation we show it is necessary to use data from envisat s medium resolution imaging spectrometer meris instrument as well as numerical weather model outputs from the european centre for medium range weather forecasts ecmwf to correct interferograms for differences in water vapor and atmospheric pressure respectively this has enabled us to robustly estimate the slip rate and locking depth for the ashkabad fault using a simple elastic dislocation model our data are consistent with a slip rate of 5 12 mm yr below a locking depth of 5 5 17 km for the ashkabad fault and synthetic tests support the magnitude of the uncertainties on these estimates our estimate of slip rate is 1 25 6 times higher than some previous geodetic estimates with implications for both seismic hazard and regional tectonics in particular supporting fast relative motion between the south caspian block and eurasia this result reinforces the importance of correcting for atmospheric contributions to interferometric phase for small strain measurements we also attempt to validate a recent method for atmospheric correction based on ecmwf era interim model outputs alone and find that this technique does not work satisfactorily for this region when compared to the independent meris estimates

comparisons of downhole geophones and hydrophones receiver tests were conducted to compare the responses of downhole geophones and hydrophones commercial receiver tools use a maximum of eight geophone levels however we use hydrophones because we can record 48 levels simultaneously for frequencies above 300 hz signal to background noise ratios for hydrophones and geophones in a prototype tool were comparable this prototype tool is a lightweight large clamping force device that can record higher frequencies than commercial geophone tools for frequencies below 300 hz signal to noise ratios were greater for the geophones than for the hydrophones a commercial geophone tool had lower low frequency signal to background noise ratios than the prototype tool but greater than those of the hydrophones further analysis was performed to determine why the signal to background noise ratios for geophones were greater than those for hydrophones at low frequencies the measured signal level for a hydrophone was 2 4 times that for a geophone compared with a t

comparative elemental and oxygen isotope geochemistry of jasperoid in the northern great basin evidence for distinctive fluid evolution in gold producing hydrothermal systems this comparative geochemical study of jasperoid in the northern great basin is based on 65 samples from 10 carlin type gold deposits and 22 similar but apparently barren hydrothermal systems multielement geochemistry coupled with oxygen isotope data indicate that hydrothermal fluids in barren and mineralized systems evolved in different ways and that there are fundamental geochemical differences among the various gold producing deposits of the area much of the variation in the jasperoid geochemical data can be explained in terms of seven abstract end member components obtained through factor analysis three of these components factors dominate the results and are related to common products of alteration and mineralization in epithermal systems of the northern great basin element associations for these factors are factor 1 tio 2 al 2 o 3 la k 2 o sr fe 2 o 3 th factor 2 au ag sb sio 2 as pb and factor 3 w b v zn co au cao ni mn cu samples from barren systems are predominantly associated with high factor 1 loadings whereas samples from mineralized systems are generally characterized by high loadings of factor 2 and or factor 3 factor 1 is related to residual argillically altered noncarbonate constituents in original host rocks factor 2 is related to hydrothermal silica jasperoid and is characterized by many of the so called pathfinder elements used in great basin exploration factor 3 although characterized by a transition metal assemblage is related to syngenetic inclusions of hydrothermal calcite within jasperoidal silica high factor 2 loadings are associated with samples from the windfall and northumberland deposits but not with samples from other gold producing systems in the study factor 3 on the other hand is the dominant component in most samples from the carlin gold quarry maggie creek pinson and preble deposits it therefore appears that there are at least two geochemically discernible types of gold deposits in the northern great basin these types are represented in this study by the windfall deposit factor 2 at one extreme and by the gold quarry deposit factor 3 at the other other deposits including alligator ridge and tonkin springs are intermediate between these extremes in this study the hydrothermal geochemistry of the jerritt canyon samples is obscured by a chert related compositional factor jasperoid samples from gold producing ore deposits have delta 18 o values ranging from 3 to 20 per mil whereas jasperoid samples from analogous barren systems have delta 18 o values ranging from 3 to 11 per mil this indicates that at least some fluids in ore related hydrothermal systems were relatively 18 o rich compared to those in barren systems jasperoid samples having high delta 18 o values invariably have high factor 3 loadings the elemental and isotopic geochemistry of jasperoid samples indicates that hydrothermal fluids in individual gold producing systems of the northern great basin evolved in different ways it appears that high co 2 contents were a critical distinguishing feature of deeply circulating fluids in the hydrothermal systems associated with high factor 3 loadings within the scope of this study it therefore appears that the systems located on the carlin and getchell trends mineral belts must have been relatively co 2 rich fluids in these systems would have been relatively reactive and perhaps more efficient at extracting gold and other metals from rocks in fluid exchange reservoirs moreover the generally high 18 o character of ore stage fluids in these systems as inferred from jasperoid compositions is indicative of extensive water rock exchange the largest gold deposits in the jasperoid study area appear to have been high co 2 high 18 o systems the primary source of co 2 in these systems is uncertain it does appear however that deep crustal structure rather than the lithologic character of fluid exchange reservoirs was probably a dominant factor governing the distribution of high co 2 systems in the northern great basin

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

ordovician aleman ribbon cherts an example of silicification prior to carbonate lithification abstract the ordovician aleman formation southwestern new mexico is primarily composed of dolomite with ribbons of chert the presence of stromatolites relict evaporite nodules and other features indicates an intertidal to shallow subtidal depositional environment the stromatolitic layers are preferentially silicified with dissolution of opaline sponge spicules providing the main if not sole source of silica silicification occurred in both the vadose and phreatic realms essentially penecontemporaneous with accumulation of the sediment and concomitant with dolomitization this is indicated by the preservation in silicified form of original anhydrite lath morphology central cavities in chert nodules partially filled with geopetal matrix dolomite and matrix dolomite immediately adjacent to conchoidal fractures of silicified carbonate grainstones the latter relationship indicates that the chert was rigid and fractured before the carbonate host sediments were lithified

geochronology of the western and central brooks range alaska implications for the geologic evolution of the anarraaq and red dog zn pb ag deposits a compilation of published geochronology of rocks and minerals from the western and central brooks range provides a framework for understanding the complex history of the brooks range and northern alaska a simplified timeline of events comprises 1 devonian extension 2 mississippian extension and zn pb ag mineralization 3 a passive interval 4 pre brooks range orogeny rock formation and thermal event 5 inception of brooks range orogeny 6 exhumation and the end of main stage deformation and 7 subsequent episodic deformation this compilation is supplemented by new 40ar 39ar dates of white mica from the anarraaq and red dog zn pb ag barite deposits from the western brooks range the deposits are hosted in black shale and carbonate rocks of the late mississippian early pennsylvanian kuna formation quartz pyrite white mica grains in sedimentary rocks above the anarraaq deposit yield an age of 195 0 2 0 ma and paragenetically late quartz pyrite white mica from the main orebody at the red dog deposit has an age of 126 1 0 7 ma these white micas are much younger than the age of zn pb ag mineralization at red dog 338 5 8 ma re os age of pyrite the date for white mica from anarraaq 195 ma appears to be related to a large scale thermal event in the region immediately before the inception of the brooks range orogeny the white mica from the red dog deposit 126 ma correlates with the later stages of the orogeny a period of blueschist metamorphism extension and rapid exhumation which varied with geographic location these dates suggest that the red dog deposits underwent significant hydrothermal overprinting during multiple episodes of the brooks range orogeny

hydrothermal biogenic and seawater components in metalliferous black shales of the brooks range alaska synsedimentary metal enrichment in a carbonate ramp setting trace element and os isotope data for lisburne group metalliferous black shales of middle mississippian early chesterian age in the brooks range of northern alaska suggest that metals were sourced chiefly from local seawater including biogenic detritus but also from externally derived hydrothermal fluids these black shales are interbedded with phosphorites and limestones in sequences 3 to 35 m thick deposition occurred mainly on a carbonate ramp during intermittent upwelling under varying redox conditions from suboxic to anoxic to sulfidic deposition of the black shales at 335 ma was broadly contemporaneous with sulfide mineralization in the red dog and drenchwater zn pb ag deposits which formed in a distal marginal basin relative to the composition of average black shale the metalliferous black shales n 29 display large average enrichment factors 10 for zn 10 1 cd 11 0 and ag 20 1 small enrichments 2 10 are shown by v cr ni cu mo pd pt u se y and all rare earth elements except ce nd and sm a detailed stratigraphic profile over 23 m in the skimo creek area central brooks range indicates that samples from at and near the top of the section which accumulated during a period of major upwelling and is broadly correlative with the stratigraphic levels of the red dog and drenchwater zn pb ag deposits have the highest zn toc total organic carbon cu toc and tl toc ratios for calculated marine fractions no detrital component of these three metals average authigenic detrital free contents of mo v u ni cu cd pb ge re se as sb tl pd and au show enrichment factors of 4 3 103 to 1 2 106 relative to modern seawater such moderate enrichments which are common in other metalliferous black shales suggest wholly marine sources seawater and biogenic material for these metals given similar trends for enrichment factors in organic rich sediments of modern upwelling zones on the namibian peruvian and chilean shelves the largest enrichment factors for zn and ag are much higher 1 4 107 and 2 9 107 respectively consistent with an appreciable hydrothermal component other metals such as cu pb and tl that are concentrated in several black shale samples and are locally abundant in the red dog and drenchwater zn pb ag deposits may have a partly hydrothermal origin but this cannot be fully established with the available data enrichments in cr up to 7 8 106 are attributed to marine and not hydrothermal processes the presence in some samples of large enrichments in eu up to 6 1 107 relative to modern seawater and of small positive eu anomalies eu eu up to 1 12 are considered unrelated to hydrothermal activity instead being linked to early diagenetic processes within sulfidic pore fluids initial os isotope ratios 187os 188os calculated for a paleontologically based depositional age of 335 ma reveal moderately unradiogenic values of 0 24 to 0 88 for four samples of metalliferous black shale a proxy for the ratio of coeval early chesterian seawater is provided by initial 187os 188os 335 ma ratios of four unaltered black shales of the coeval kuna formation that average 1 08 nearly identical to the initial ratio of 1 06 for modern seawater evaluation of possible sources of unradiogenic os in the metalliferous black shales suggests that the most likely source was mafic igneous rocks that were leached by externally derived hydrothermal fluids this unradiogenic os is interpreted to have been leached by deeply circulating hydrothermal fluids in the kuna basin followed by venting of the fluids into overlying seawater we propose that metal bearing hydrothermal fluids that formed zn pb ag deposits such as red dog or drenchwater vented into seawater in a marginal basin were carried by upwelling currents onto the margins of a shallow water carbonate platform and were then deposited in organic rich muds together with seawater and biogenically derived components by syngenetic sedimentary processes metal concentration in the black shales was promoted by high biologic productivity sorption onto organic matter diffusion across redox boundaries a low sedimentation rate and availability of h2s in bottom waters and pore fluids

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

an up to date crustal deformation map of iran using integrated campaign mode and permanent gps velocities we present the most extensive and up to date unified gps velocity field for iran we processed the data collected during 10 yr 2006 2015 from the iranian permanent gnss network ipgn and combined them with previously published velocity solutions from the gps survey measurements during 1997 2013 we analysed this velocity field using a continuum approach to compute a new strain rate map for this region and we designed a block model based on the main geological morphological and seismic structures comparison between both approaches suggests similar results and allows us to present the first comprehensive first order fault slip rate estimates for the whole of iran our results confirm most of the results from previous geodetic studies however we also show a trade off between the coupling ratio of the iranian makran subduction interface and the kinematics of the faults north of the makran in the jazmurian depression indeed although too scarce to accurately estimate a coupling ratio we show that coupling higher than 0 4 on the plate interface down to a depth of 25 km will induce extension on the e w faults in the jazmurian region however the sites close to the shoreline suggest a low coupling ratio hence the coupling on this plate interface is probably more complicated than previously described and the iranian makran subduction interface mechanical behaviour might be similar to that on the hellenic subduction zone

synlithification deformation processes of the cretaceous sediments of the ivory coast ghana transform margin a way to detail the margin history the ivory coast ghana margin is a typical transform margin along which large scale tectonism has been well documented the cretaceous sediments of the ivory coast ghana transform margin were subjected to numerous tectonic gravitational and hydrothermal forces during lithification in this paper we infer the order of occurrence of deformation regimes from characteristic deformations observed in samples of ocean drilling program odp leg 159 three main types of minor scale deformation are identified and characterized in terms of geometry rheology and kinematics 1 extensional structures such as normal faults and irregular veins with angular indented walls that are widely recorded at all odp sites 2 compressional structures that are confined to the marginal ridge of the ivory coast ghana transform margin and include reverse faults folds and vertical crenulation cleavage and 3 various types of shear zone at low angles with respect to bedding which are continuous throughout the cretaceous succession of the ridge structural analysis combined with thin section observation shows that most of these deformations occurred in water rich sediments the extensional minor scale structures are related to the early cretaceous rifting stage of the margin as characterized at regional scale by half grabens and tilted blocks the compressional structures observed in the samples are attributed to turonian santonian positive inversion tectonics and related to the occurrence of large scale flower structures and inverted extensional blocks in contrast the shear zones at low angles with respect to bedding observed throughout the cretaceous series are linked to local gravity induced tectonics

ground motion measurement in the lake mead area nevada by differential synthetic aperture radar interferometry time series analysis probing the lithosphere rheological structure 1 we measure ground motion around the lake mead nevada using synthetic aperture radar interferometry the lake water level has fluctuated through time since impoundment in 1935 to quantify the deformation due to water level variations over the past decade and to constrain the crust and mantle rheological parameters in the lake area we analyze 241 interferograms based on 43 ers images acquired between 1992 and 2002 all interferograms have a high coherence due to arid conditions most of them show strong atmospheric artefacts tropospheric phase delays are estimated and corrected for each interferogram by analyzing the phase elevation correlation corrections are validated using data from the era40 global atmospheric reanalysis corrected interferograms are inverted pixel by pixel to solve for the time series of ground motion in the lake area temporal smoothing is added to reduce random atmospheric artefacts the observed deformation is nonlinear in time and spreads over a 50 50 km2 area we observe a 16 mm subsidence between 1995 and 1998 due to an 11 m water level increase followed by an uplift due to the water level drop after 2000 we model the deformation taking into account the loading history of the lake since 1935 a simple elastic model with parameters constrained by seismic wave velocities does not explain the amplitude of the observed motion the two layer viscoelastic model proposed by kaufmann and amelung 2000 with a mantle viscosity of 1018 pa s adjusts well the data amplitude and its spatiotemporal shape

active tectonics of the east alborz mountains ne iran rupture of the left lateral astaneh fault system during the great 856 a d qumis earthquake the 856 a d qumis earthquake m7 9 is the most destructive earthquake to have occurred in iran killing more than 200 000 people and destroying the cities of damghan and the old parthian capital of shahr i qumis hecatompylos this study combines evidence of historical seismicity with observations of the geomorphology and paleoseismology to provide the first detailed description of active faulting in the damghan region of the east alborz mountains iran regional left lateral shear is accommodated on the astaneh damghan and north damghan faults quaternary alluvial fans have been displaced along the astaneh fault with 15 20 m stream offsets recording the cumulative displacement over the last two to five earthquakes a paleoseismology study from a single trench along a 5 10 km segment of the astaneh fault reveals a rupture prior to 1300 a d and significantly later than 600 b c despite the limitations of a single trench in documenting the spatial and temporal evolution of the fault over the late quaternary we are nevertheless able to bracket the last event to a time period consistent with the 856 a d earthquake two older earthquakes were also identified during the holocene occurring between 600 b c and 4600 b c and between 4600 b c and 9600 b c the location of our trench within a bend on the astaneh fault which could act as a barrier to rupture propagation means the three earthquakes recovered from our trench over the holocene may represent a minimum further trenching will reveal how the astaneh fault ruptures over repeated earthquakes and consequently the magnitude and extent of slip during the 856 a d earthquake

considerations for high resolution vsp imaging vertical seismic profiling vsp data can complement surface seismic data where higher resolution is desired or necessary to fully understand a reservoir vsp data typically provide greater resolution because of the inherently smaller fresnel zone and because the bandwidth is usually wider than comparable surface seismic data high fidelity images are required for effective reservoir monitoring also special situations exist such as attempting to image beneath salt or volcanics where vsp data can potentially yield superior results because the seismic energy travels through the distorting overburden only once

the importance of siliceous radiolarian bearing mudstones in the formation of sediment hosted zn pb ba mineralization in the selwyn basin yukon canada sediment hosted massive sulfide shms mineralization occurred in three main episodes during the evolution of the selwyn basin yukon and northwest territories canada in the macmillan pass district tom and jason deposits the upper devonian strata of the earn group host the youngest least deformed examples of shms mineralization the earn group comprises gray to black homogeneous mudstones which have been deformed in the cordilleran fold and thrust belt are weathered and poorly exposed this makes stratigraphic correlations and the recognition of prospective units very challenging the host rock siliceous mudstone and mineralized intervals at the tom and jason zn pb ba deposits have been sampled from drill core major element chemistry and total organic carbon toc data are presented for the host rock samples from two drill holes tyk 5 n 18 76 17 n 19 all mudstones contain between 2 and 5 wt toc and 67 to 83 wt sio2 subtle alteration marked by potassium loss k2o al2o3 50 radiolarians by volume within the mineralized horizons and in barren time equivalent strata and therefore are a useful stratigraphic marker unit in otherwise homogeneous featureless fine grained mudstones the presence of highly siliceous carbonaceous mudstone units with preserved radiolarians suggests that in the late devonian there is a link between biological productivity in the water column the resultant sedimentation and the shms deposits these biosiliceous lithologies may be particularly favorable host rocks to shms mineralization for the following reasons 1 high porosities during early diagenesis preserve volume and enhance permeabilities in partially lithified sediments which are important parameters for subseafloor replacement mineralization 2 these units are rich in organic materials due to their deposition in productive settings and have a high capacity for the generation of sulfide via sulfate reduction therefore we suggest there is a link between times of high biological activity and productivity in oceans sediments derived from those processes and shms deposits

mineralogical and chemical variations castellanos shale hosted zn pb ba deposit northwestern cuba the shale hosted castellanos sedimentary exhalative zn pb ba deposit of jurassic age in northwestern cuba consists of pyrite sphalerite and galena in a hydrothermal quartz carbonate barite matrix with very little clastic or shale matrix the northeastern end of the zn pb ba lens overlies a transgressive cu stringer zone which is interpreted as the vent or feeder channel for the exhalative mineralization abundance patterns in the sulfide assemblage define layering within the deposit in the southwestern part of the deposit sphalerite and galena increase and pyrite decreases stratigraphically upward within individual layers to the northeast near the vent sphalerite and galena decrease upward parallel to pyrite in the area of the vent the basal carbonate is exclusively dolomite however calcite abundance increases rapidly upward remote from the vent dolomite is the dominant carbonate from the base to the top of the deposit carbonate and barite are the main gangue minerals near the discharge site quartz is the major gangue mineral in the southwestern section these and other variations result from differences in a ca super 2 f oh2 temperature and sigma s relative to sulfide forming cations especially fe super 2 at the discharge site and in the depositional basin some distance from the vent

a hydrophone vertical seismic profiling experiment to reduce the cost of vsp data acquisition it is necessary to record the vsp signal from a vertical array of geophones for a single operation of the source until a vertical array of clamped three component geophones is available it seems logical to evaluate the capabilities of a vertical array of hydrophones which is much easier to fabricate it is well known that elastic waves in the solid couple to pressure waves in the borehole fluid it is also well known that this coupling excites in the borehole fluid energy known as tube wave noise that dominates the borehole pressure signal after the first arrival the borehole acts as a waveguide in this paper we test the effectiveness of velocity filtering of the borehole pressure signal to attenuate the slowly propagating tube wave noise and enhance the faster propagating body wave signals our initial test satisfactorily extracted from the hydrophone array data a strong reflected event that was also observed in the conventional clamped geophone vsp take

rare earth elements and hydrothermal ore formation processes abstract the geochemical behaviour of ree is influenced by nearly all important hydrothermal ore formation processes including fluid rock interactions fluid precipitations adsorption and scavenging onto particles and changes in fluid temperature pressure ph eh alkalinity and ligand concentration destabilization of ree complexes in response to these physicochemical changes and possible chemical crystallographic controls determine the concentration and distribution of ree within hydrothermal minerals mineraloids and amorphous phases alteration assemblages of intrusive related mineralisations may exhibit a wide range of ree distributions and ree fractionation trends the ree distribution within these hydrothermally altered lithologies will depend on the ree concentration in the rock and the fluid the partitioning behaviour of the ree between the rock phases and the fluid and the types of alteration reactions which take place reactive rocks such as carbonate rich lithologies of skarn deposits may gain or loose significant amounts of ree during fluid rock interactions ree geochemical investigations combined with fluid inclusion and stable isotope studies may point to the origin of alteration products and the source s of ore fluids ancient massive sulphide ores commonly exhibit anomalous eu concentrations similar to many recent submarine hydrothermal precipitates the recognition of hydrothermal fluid seawater sedimentary or volcanically derived ree distributions within ores chemical sediments and hydrothermally altered lithologies may help to constrain genetic modelling of massive sulphide deposits care should be taken with the interpretation of ree distributions from metamorphosed hydrothermal ore deposits becase metamorphic and diagenetic alteration reactions may change the ree distributions mobility of ree may occur during diagenesis of carbonate rich rocks and during the development of shear zones and migmatites in contrast very large fluid rock ratios are necessary to cause significant changes in ree patterns of silicate rich rocks during diagenesis and regional metamorphism

geologic setting petrology and geochemistry of stratiform sphalerite galena barite deposits red dog creek and drenchwater creek areas northwestern brooks range alaska similar stratiform sphalerite galena barite deposits occur in the red dog creek area de long mountains quadrangle and in the drenchwater creek area howard pass quadrangle northwestern brooks range alaska the deposits located approximately 180 km apart are hosted by mississippian and pennsylvanian strata of the kagvik structural sequence of late paleozoic and early mesozoic age this sequence is situated in the lowermost structural plate of a series of predominantly east striking shallow dipping thrust plates that characterize the regional structure the deposits occur in shale tuff tuffaceous sandstone altered chert and quartz exhalite these units are in places interlayered with or adjacent to bedded or nodular barite or submarine keratophyre flows chert and shale commonly contain abundant highly altered fine grained feldspar pumice lapilli and mafic volcanic rock fragments the main types of occurrences at red dog creek are 1 disseminated and stratiform sulfides thinly bedded in organic rich mississippian and pennsylvanian shale and chert 2 massive sulfide veins and breccia fillings in silicified mississippian and pennsylvanian shale and 3 stratiform sulfide bearing lenses subdivided into 3a quartz exhalite with up to several percent sulfides and barite 3b massive sulfide quartz lenses with up to several percent barite and 3c barite quartz lenses with up to several percent sulfides at drenchwater creek sulfides and barite occur as 1 disseminations in shale chert tuff and tuffaceous sandstone 2 disseminations to aggregates in quartz exhalite and 3 occurrences in veins crosscutting cleavages in brecciated chert and shale the stratiform sulfides occur in zones up to several thousand meters long and several tens of meters thick preliminary grades at red dog creek are 17 1 percent zinc 5 0 percent lead and 2 4 oz silver per ton contained in at least 85 million tons the range of sulfide sulfur isotope values at red dog creek is 16 6 per mil to 3 6 per mil sphalerite averages 0 8 per mil pyrite is isotopically lighter than coexisting sphalerite in quartz exhalite and massive sulfide lenses this isotopic relationship is compatible with paragenetic relationships which show pyrite crystallized both earlier and later than other sulfides galena is isotopically lighter than coexisting sphalerite three groups of geologically and isotopically distinct barites exist including isotopic values appropriate for derivation from late paleozoic seawater sulfate early in the depositional sequence isotopically light pyrite formed from organically reduced seawater sulfate sphalerite galena late pyrite and some barite precipitated from two sulfur bearing solutions that mixed at the mineralization site isotopically light barite associated with sulfides precipitated from oxidized h 2 s without seawater sulfate contribution lead isotope data from red dog and drenchwater creeks are compatible with generation of lead in a phanerozoic mature island arc setting a typical orogene or possibly a back arc type intracratonic basin the stratiform sphalerite galena barite deposits probably formed in an incipient island arc environment near a continental margin containing magmas of keratophyric and andesitic composition where metal laden hydrothermal fluids discharged into a deep water low energy environment later intense deformation associated with plate docking and thrusting disrupted and partly remobilized and stratiform deposits