the physical basis of mb ms and variable frequency magnitude methods for earthquake explosion discrimination we use recent results from deterministic numerical modeling of earthquakes and explosions to develop an improved physical basis for earthquake explosion discrimination we use six three dimensional finite difference simulations of earthquakes for the earthquake source models and four empirical and four numerical models for explosions in different materials four factors contribute to the success of the mb ms discriminant source spectra focal mechanism near source elastic properties and interference of p spectral differences contribute about 0 5 magnitude unit to the separation between earthquake and explosion populations for large events but this difference vanishes for events with mb 4 0 using a frequency band of 0 5 3 0 hz for small events the vfm discriminant is complementary to mb ms in several ways vfm is improved by p interference while mb ms is degraded vfm is more effective for hard rock explosions while mb ms will preferentially discriminate explosions in low velocity materials and vfm is insensitive to fault orientation vfm is more sensitive to noise and regional attenuation differences than mb ms simultaneous use of both methods should allow improved discrimination of small events

involvement of magmatic fluids at the laloki and federal flag massive sulfide cu zn au ag deposits astrolabe mineral district papua new guinea sulfur isotope evidence we present the first sulfur s isotope data of sulfides sulfates pyrite in host mudstone and bulk sulfur of gabbroic rocks from the laloki and federal flag massive cu zn au ag deposits in the astrolabe mineral district papua new guinea early stage pyrite marcasite chalcopyrite and sphalerite from laloki display wide range of 34s values from 4 5 to 7 0 n 16 late stage pyrite chalcopyrite and sphalerite have restricted 34s values of 1 9 to 4 7 n 16 the mineralizing stage these correspond to had moderately saline 5 9 8 4 nacl eq wt mineralizing fluids of possible magmatic origin a single analysis of late stage barite has a value of 34s 17 9 which is likely similar to coexisting seawater sulfate pyrite from the foot wall mudstone at laloki has very light 34s values of 36 1 to 33 8 n 2 which suggest an organic source for s pyrite marcasite and chalcopyrite from federal flag show 34s values of 2 4 to 1 9 n 2 consistent with a magmatic origin either leached from intrusive magmatic rocks or derived from magmatic hydrothermal fluids the very narrow range and near zero 34s values 1 0 to 0 6 of bulk gabbroic samples is consistent with mantle derived magmatic s sulfur isotope characteristics of sulfides and sulfates are however very similar to base metal sulfide accumulations associated with modern volcanic arcs and sedimented mid ocean ridges the most reasonable interpretation is that the range of the sulfide and sulfate 34s values from both laloki and federal flag massive sulfide deposits is indicative of the complex interaction of magmatic fluids seawater gabbroic rocks and mudstone

calc alkaline volcanism along the eastern margin of the namaqua mobile belt south africa a possible middle proterozoic volcanic arc abstract the boksputs and upington sequences of the areachap group present along the eastern margin of the namaqua mobile belt in southern africa contain amphibolites with chemical properties which suggest that they are the metamorphic products of arc related precursors the amphibolites which form the predominant rock type of the jannelsepan formation of the areachap group are subdivided on mineralogical grounds into massive and pyroxene amphibolite the massive amphibolite of the boksputs sequence chemically resembles low k arc tholeiite while the pyroxene amphibolite is slightly more calc alkaline in character the massive amphibolite of the upington sequence is predominantly calc alkaline while the pyroxene amphibolite shows a strong shoshonitic affinity the chemical differences between the two metavolcanic sequences are interpreted in terms of arc polarity and arc maturity the present position of the associated granite plutons of the keimoes suite indicates that the two sequences most probably represent fragments of an originally northwest trending arc system with a southwest northeast polarity the possibility of a north south polarity however cannot be ruled out the chemical characteristics may be indicative of arc maturity the upington sequence thus represents a more mature and the boksputs sequence a less mature portion of a middle proterozoic arc system the areachap group is interpreted as an accretion feature with characteristics generated in a subduction environment

unconventional pattern of reservoir facies distribution in epeiric successions lessons from an outcrop analog lower keuper germany this article presents 1 a process oriented description of an outcrop analog for epeiric successions 2 a discussion of fundamental characteristics of epeiric basin fills and 3 a generic depositional model which may be used for improved reservoir prediction in epeiric settings the case study focuses on the upper ladinian mixed siliciclastic carbonate lower keuper formation it is composed of storm generated tide generated and bioturbated facies paleogeographically the succession shows an unusual lateral energy zonation comprising a seaward low energy zone close to wave base an intermediate reservoir prone high energy zone within wave base and a landward low energy zone above wave base stratigraphically the lower keuper formation is subdivided into meter scale transgressive regressive cycles correlatable over distances of more than 500 km cycle boundaries are interpreted to be isochronous within the resulting chronostratigraphic framework facies distributions have been mapped out in three dimensions revealing that reservoir prone facies are most extensive in shoreline detached positions reservoir bodies are thin have sheetlike geometries but extend for several tens of kilometers and are stacked in an aggradational facies architecture additionally the reservoir prone facies is thicker developed in zones of stronger subsidence a few kilometers wide linked to underlying basement blocks resulting unconventional reservoir prediction strategies for similar shallow marine epeiric settings should target shoreline detached high energy facies belts that are preferentially developed within zones of stronger subsidence controlled by basement tectonics

sulfur cycling at the mid atlantic ridge a multiple sulfur isotope approach abstract the role of sulfur in two hydrothermal vent systems the logatchev hydrothermal field at 14 45 n 44 58 w and several different vent sites along the southern mid atlantic ridge smar between 4 48 s and 9 33 s and between 12 22 w and 13 12 w is examined by utilizing multiple sulfur isotope and sulfur concentration data isotope compositions for sulfide minerals and vent h 2 s from different smar sites range from 1 5 to 8 9 in 34 s and from 0 001 to 0 051 in 33 s these data indicate mixing of mantle sulfur with sulfur from seawater sulfate combined 34 s and 33 s systematics reveal that vent sulfide from smar is characterized by a sulfur contribution from seawater sulfate between 25 and 33 this higher contribution compared with epr sulfide indicates increased seawater sulfate reduction at mar because of a deeper seated magma chamber and longer fluid upflow path length and points to fundamental differences with respect to subsurface structures and fluid evolution at slow and fast spreading mid ocean ridges additionally isotope data uncover non equilibrium isotopic exchange between dissolved sulfide and sulfate in an anhydrite bearing zone below the vent systems at fluid temperatures between 335 and 400 c 34 s values between 0 2 to 8 8 for dissolved and precipitated sulfide from logatchev point to the same mixing process between mantle sulfur and sulfur from seawater sulfate as at smar 34 s values between 24 5 and 6 5 and 33 s values between 0 001 and 0 125 for sulfide bearing sediments and mafic ultramafic host rocks from drill cores taken in the region of logatchev indicate a clear contribution of biogenic sulfides formed via bacterial sulfate reduction basalts and basaltic glass from smar sites with 33 s 0 008 reveal lower 33 s lower values than suggested on the basis of previously published isotopic measurements of terrestrial materials we conclude that the combined use of both 34 s and 33 s provides a more detailed picture of the sulfur cycling in hydrothermal systems at the mid atlantic ridge and uncovers systematic differences to hydrothermal sites at different mid ocean ridge sites multiple sulfur isotope measurements allow identification of incomplete isotope exchange in addition to isotope mixing as a second important factor influencing the isotopic composition of dissolved sulfide during fluid upflow furthermore based on 33 s we are able to clearly distinguish biogenic from hydrothermal sulfides in sediments even when 34 s were identical

geochemistry and metamorphism of the prieska zn cu deposit south africa the prieska orebody is a 50 million ton massive sulfide zn cu deposit situated near the eastern border of the middle proterozoic namaqua province of southern africa the strata bound stratiform deposit lies in a terrane which has been affected by high grade metamorphism and intense deformation textures now seen in the ore and country rocks are not primary but reflect the complex tectono metamorphic history the deposit is contained in a peraluminous unit underlain by a metadacite and overlain by a composite sequence containing metapelites metabasic rocks and a variety of reworked volcanic rock types amphibolite layers that originated as intrusive basaltic dikes and sills are found in all of these rock types it is suggested that the massive sulfide ore formed above hydrothermally altered metadacite the rock types thus derived include a gedrite bearing assemblage the metamorphic equivalent of a chloritic alteration pipe and a quartz perthite sillimanite gneiss representing silicified and sericitized sediments at the floor of the discharge basin overlying these rocks is the massive sulfide unit calcite anhydrite barite rocks immediately above the ore may have formed a sulfate carbonate capping during sulfide deposition the prieska deposit and other smaller sulfide deposits in the same region have geochemical features including metal composition and pb and s isotope characteristics that distinguish them from the important massive sulfide deposits of the central part of the namaqua province whereas the prieska deposits are related to hydrothermal action in a volcano sedimentary sequence no metamorphic equivalents of alteration pipes have been found at the sediment hosted aggeneys gamsberg deposits

lithological controls on seismicity in granitic rocks seismicity induced from a tunnel excavation through two lithological units granite and granodiorite at the canadian underground research laboratory url is analyzed in an attempt to understand observed lithological differences in the damage zone development the results from seismicity recorded by the 16 triaxial accelerometer array found the damage zone around granite excavations to have more events occurring ahead of the tunnel face and a shorter overall seismic response time than the granodiorite petrographic analysis of the rock samples show stress relief microcracking predominantly in the larger quartz crystals suggesting that these are the weakest mineral grains we propose that initial in situ cracking occurs in the large quartz crystals significantly reducing the strength and resulting in rapid formation of the excavation damage zone the smaller grained more homogenous granodiorite shows less stress relief microcracking probably due to the stresses being distributed over a larger number of grain boundaries from the seismic and petrographic evidence we propose that the crack initiation stress is lower in the granite than the granodiorite the events from the granite and granodiorite have a similar range in magnitude m w 2 9 to 4 2 and source dimension r 0 13 0 51 m they have a mean p to s wave corner frequency ratio of 1 0 probably indicating relatively slow rupture velocities about 25 of the events have an s to p wave energy ratio less than 10 agreeing with previous source mechanism studies which find a number of events at this depth have significant isotropic components

metamorphic imprints upon sulphide mineralisation at boksputs northern cape south africa a small stratiform fe cu zn mineralisation has been examined from boksputs within the metavolcanic areachap group 1 5 ga along the eastern boundary of the namaqua province distinctly deformational and metamorphic features within the mineralisation can be separated into an early and a late fabric the former is related to an early prograde metamorphism m1 and also to a subsequent mild retrogression m2 which can be regionally distinguished in the silicate mineralogy whilst the latter fabric is derived during a severe retrogressive event m3 that is concentrated especially in shearzones that cut the mineralisation a release of secondary sulphur bearing fluids during m3 is evidenced by new growth and redistribution of sulphides and by local replacement of pyrrhotite by pyrite

evaluating isotopic equilibrium among sulfide mineral pairs in archean ore deposits case study from the kidd creek vms deposit ontario canada recent developments in the measurement of 34s and 33s in sulfide minerals provide a new framework to evaluate isotopic equilibrium among sulfide minerals and a new tool to investigate mineralizing processes or sources of sulfur in ore forming systems isotopic equilibrium requires that values of 34s and 33s are highly correlated between mineral pairs and that deviations quantified as 33s from a reference mass dependent fractionation are the same for both minerals within experimental error in this contribution we apply this framework for the first time to natural samples and evaluate isotopic equilibrium among sulfide minerals from the archean kidd creek volcanogenic massive sulfide deposit in ontario canada two of eight sulfide mineral pairs showed clear isotopic disequilibrium in agreement with interpreted paragenetic relationships six other pairs have isotopic compositions that are consistent with equilibrium we discuss the implications of these results for the interpretation of mineral paragenesis and sulfur isotope geothermometry at kidd creek this technique offers new possibilities for evaluating sulfur isotope systematics in archean 2 45 ga ore deposits in which the range of 34s values is small but non zero values of 33s are common

the northeastern ohio earthquake of 31 january 1986 was it induced abstract on 31 january 1986 at 11 46 est an earthquake of m b 5 0 occurred about 40 km east of cleveland ohio and about 17 km south of the perry nuclear power plant the earthquake was felt over a broad area including 11 states the district of columbia and parts of ontario canada caused intensity vi vii at distances of 15 km and generated relatively high accelerations 0 18 g of short duration at the perry plant thirteen aftershocks were detected as of 15 april with six occurring within the first 8 days two of the aftershocks were felt magnitudes for the aftershocks ranged from about 0 5 to 2 5 focal depths for all of the earthquakes ranged from 2 to 6 km except for one small earthquake all of the aftershocks occurred in a very tight cluster with a north northeast orientation focal mechanisms of the aftershocks exhibit predominantly oblique right slip motion on nearly vertical nodal planes oriented n15 to 45 e with a nearly horizontal p axis north of east three deep waste disposal wells are currently operating within 15 km of the epicentral region and have been responsible for the injection of nearly 1 2 billion liters of fluid at pressures reaching 112 bars above ambient at a nominal depth of 1 8 km estimates of stress inferred from commercial hydrofracturing measurements suggest that the state of stress in northeastern ohio is close to the theoretical threshold for failure along favorably oriented preexisting fractures this implies that effective stress conditions near the bottom of the two most active wells may be at or near the critical level for incipient failure two and possibly three earthquakes have occurred within less than 5 km from the wells since 1983 the relative distance to the main shock epicenter and its aftershocks about 12 km the lack of large numbers of small earthquakes typical of many induced sequences the history of small to moderate earthquakes in the region prior to the initiation of injection and the attenuation of the pressure field with distance from the injection wells however all argue for a natural origin for the 1986 earthquakes in contrast the proximity to failure conditions at the bottom of the well and the probable spatial association of at least one earthquake suggest that triggering by well activities cannot be precluded

three dimensional evolution of the keuper of the paris basin based on detailed isopach maps of the stratigraphic cycles tectonic influences detailed isopach maps of the stratigraphic cycles of the keuper of the paris basin are used to reconstruct the 3d evolution of the basin cycle by cycle and to investigate the influence of tectonic movements the major base level cycles record variations in the rate of subsidence in time and space the area of greatest subsidence which was confined to the east of the basin during the scythian carnian cycle shifted northwestwards during the carnian liassic cycle within the marnes irisees inferieures the e w faults abruptly limited the extent of salt deposits to the north and south by forming a corridor where subsidence was greater the westward shift of areas of subsidence induced by the migration of fault activity enhanced the migration of salt series which was bounded by the saint martin de bossenay fault the cessation of fault activity in the eastern part of the basin marked the end of halite sedimentation from the gres a roseaux formation a general northwestward tilt of the basin with corresponding depocentre migration induced a truncation within the marnes irisees superieures the depocentres were located in the west which was the site of most fault activity which influenced the fluvial deposits by creating tilted blocks where sediment could accumulate

spectral discrimination of nts explosions and earthquakes in the southwestern united states using high frequency regional data a high frequency seismic station has been operating since march 1987 near nelson nv records of earthquakes at regional distances from the station show substantially more energy at frequencies above 10 hz than records of nuclear tests of comparable magnitude on the nevada test site this contradicts the predictions made by investigators who have advocated high frequency monitoring for nuclear test detection and identification measuring the slopes of the pg velocity spectra between 4 and 30 hz successfully discriminates 11 nts explosions from 36 earthquakes recorded in the first seven months of operation the spectral differences may result from the respective source depths with the earthquakes occurring deeper and in faster material than the explosions

an evaluation of seismic decoupling and underground nuclear test monitoring using high frequency seismic data an effective solution to the problem of the detection and identification of low yield coupled and fully decoupled underground nuclear explosions appears available via use of high frequency seismic data ranging up to 30 or 40 hz in order to evaluate detection identification capabilities when using such data it is necessary to estimate 1 spectral characteristics and relative amplitudes of both p and s waves from explosions and earthquakes over the frequency band from 5 to 40 hz 2 signal transmission characteristics over this band through pertinent types of earth structure and 3 recording system and ground noise characteristics over this frequency band in this study each of these topics is considered in turn as they relate to detection and discrimination of the signals from low yield coupled and decoupled explosions in the regional and teleseismic distance ranges estimates of the capabilities of specific hypothetical networks to detect and identify insofar as signal to noise ratio is an important factor in identification explosions within the ussr are then considered these estimates of signal detection capability provide the central focus for the study as they serve to translate diverse and rather complex sets of observational data and theory into concrete predictions of monitoring capability following the assessment of detection capabilities the problem of identification of small events is considered with particular emphasis on discrimination at regional distances where the network is calculated to provide signals of high signal to noise ratio the principal results and conclusions of this study are as follows 1 seismic system noise can be suppressed to levels well below ground noise at quiet sites up to frequencies at least as high as 30 40 hz when using presently available hardware 2 average amplitudes of high frequency noise in a variety of geological environments are very low and change little with time or season 3 transmission of high frequency p and s wave signals in the regional distance range in stable continental areas and shields is nearly as efficient as at 1 hz with effective q factors in shield areas being about 9000 and 4000 for high frequency pn and sn respectively while the effective q for pn waves in tectonic areas is about 1000 4 a properly designed and deployed network of 25 simple three component nonarray stations internal to the ussr and 15 similar stations surrounding the ussr is predicted to be capable of multistation detection at high signal to noise ratio of fully decoupled 1 kt explosions located at all potential decoupling sites within the ussr 5 by inference from the quantitative agreement of empirical observations and theoretical predictions when using lower frequency data over a great range of explosion yields we conclude that procedures based on the use of both detectable p and s waves will serve to identify explosion generated seismic signals at least as small as those expected from a fully decoupled 1 kt explosion

laser microprobe sulphur isotope analysis of arsenopyrite experimental calibration and application to the boliden au cu as massive sulphide deposit abstract metamorphic remobilization of arsenopyrite rich ores is a globally important process which can lead to significant concentrations of gold in order to understand this and related processes relations of sulphur isotopes can give a number of important clues to resolve such relations in detail we have successfully calibrated and applied a laser combustion system for in situ analysis of sulphur isotopic compositions of arsenopyrite experimental calibration of the laser fractionation factor 0 4 was obtained by using compositionally and isotopically homogeneous natural samples from ore deposits at boliden sweden and freiberg germany subsequent to detailed microscopic study the s isotope ratios of these samples were measured by conventional and laser combustion techniques the present application to different types of arsenopyrite in the palaeoproterozoic metamorphosed vhms ores of the boliden au cu as deposit skellefte district northern sweden shows that the sulphur isotope composition of arsenopyrite is essentially unmodified during medium grade metamorphic recrystallization and remobilization here massive arsenopyrite ore is crosscut by later veins that carry a complex quartz sulphosalt sulphide assemblage the latter ore type is markedly au rich compared to the host ore and thus of significant economic interest we find that both ore types exhibit very similar sulphur isotope compositions ca 2 to 3 v cdt which is similar to most massive sulphide deposits in the skellefte district thus the crosscutting au rich vein ore has inherited the sulphur isotope composition from sulphur liberated by metamorphic reactions affecting the massive ore and most likely also inherited the au through this mechanism the latter finding clearly has important implications both for the general discussion on and the prospecting for similar high grade au ores in this world class mining region

faults of the central part of the lewis and clark line and fragmentation of the late cretaceous foreland basin in west central montana the lewis and clark line is a prominent zone of strike slip dip slip and oblique slip faults that extends from near wallace idaho to east of helena montana faults of this zone have been intermittently active from middle proterozoic to holocene time and because of numerous tectonic overprints controversy continues about displacement directions and times of displacement along specific faults geologic mapping shows evidence that many principal faults of the lewis and clark line such as the st marys helena valley bald butte ninemile and osburn faults had right separation or slip that ranged between 28 and 11 km and this displacement probably occurred during late cretaceous time other faults such as the elevation mountain placer creek and ranch creek faults have late cretaceous right separations that range between 8 and 3 2 km and the mount sentinel fault zone has between 6 5 and 3 km of right separation of probable late cretaceous age subsidiary structures of the lewis and clark line postdate paleozoic and lower cretaceous rocks and predate late cretaceous stocks at some places subsidiary faults and folds that have age constraints have slip directions compatible with right slip along adjacent principal faults sedimentation patterns of lower and upper cretaceous rocks indicate that faults of the lewis and clark line fragmented the foredeep region of the foreland basin into separate northern and southern basins in late cretaceous time the lower and upper cretaceous blackleaf formation albian and lower cenomanian was deposited in a continuous foredeep basin that extended across the lewis and clark line from north of the canadian border to southwestern montana a distance of about 450 km north of the lewis and clark line middle and upper cenomanian rocks are absent and a thin sequence of uppermost cenomanian to campanian rocks was deposited in a marine environment that changed to a strand line and continental environment in early campanian time south of the lewis and clark line middle and upper cenomanian deposits are also absent but a thick sequence of turonian to campanian rocks was deposited in brackish water and strand line environments and during later campanian time in a continental environment in the region between the st marys helena valley and bald butte faults a barrier may have formed that served as a local sediment source between foredeep regions in the northern and southern foreland basin during the period 91 to 75 ma south of the bald butte fault an extensional tectonic regime contributed to a higher sediment accumulation rate in the foredeep region along the north border of the southern basin 30 cm 1 000 yr as compared to lower sediment accumulation rates 6 9 and 7 8 cm 1 000 yr in the foredeep region of the south part of the northern basin

seismic moments local magnitudes and coda duration magnitudes for earthquakes in central california onscale seismograms recorded at stations in the u s geological survey s usgs central california seismic network calnet have been used to estimate the seismic moment m and local magnitude ml for earthquakes of 1 ml 4 located on the san juan bautista and parkfield sections of the san andreas fault the coyote lake section of the calaveras fault the sargent fault and near livermore these data together with m and ml estimates for 4 ml 6 earthquakes in these areas cannot be fit with a single linear log m versus ml relation rather the data are consistent with log m 1 5 ml 16 for 3 ml 6 with log m 1 2 ml 17 for 1 1 2 ml 3 1 2 and with a slope of to 1 fro 1 2 ml 1 1 2 whereas usgs coda duration magnitude md is consistent with ml for 1 1 2 ml 3 md is larger than ml at ml 1 1 2 and smaller than ml at ml 3 log m can be estimated to a precision of 0 2 for 1 md 3 1 2 earthquakes in central california by applying log m 1 2 md 17 to the md that have been routinely published by the usgs

improvements in mining induced microseismic source locations at the lucky friday mine using an automated whole waveform analysis system for years severe rockburst problems at the lucky friday mine in northern idaho have been a persistent safety hazard and an impediment to production an mp250 based microseismic monitoring system which uses simple voltage threshold picking of first arrivals has been used in this mine since 1973 to provide source locations and energy estimates of seismic events recently interest has been expressed in developing a whole waveform microseismic monitoring system for the mine to provide more accurate source locations and information about source characteristics for this study we have developed a prototype whole waveform microseismic monitoring system based on a 80386 computer equipped with a 50 khz analog digital convertor board the software developed includes a data collection program a data analysis program and an event detection program whole waveform data collected and analyzed using this system during a three day test have been employed to investigate sources of error in the hypocenter location process and to develop an automatic phase picker appropriate for microseismic events

overview of the subsurface structural pattern of the paris basin france insights from the reprocessing and interpretation of regional seismic lines abstract the study presents the methodology used by the french geological survey brgm for the building reprocessing and interpretation of selected regional seismic lines in the paris intracratonic basin france the 14 constructed e w and n s regional transects represent a total of 2 516 km length and are based on the merge of 240 seismic single profiles recorded by petroleum operators between 1971 and 1995 the regional lines have been selected to cross the main oil fields of the paris basin as well as high potential areas for oil exploration a first difficulty was to recover the raw data necessary to build up the regional transects the signal reprocessing harmonization and merge of the single seismic lines constituent of the regional transects are then described these operations represent the cornerstone of the study we put the emphasis on the primary static corrections as the targeted structures are commonly spatially associated with large seismic velocity variations in the upper cretaceous chalk and tertiary sedimentary cover the interpreted regional transects definitely give complementary information to the existing studies which generally lack seismic and therefore structural data we give an overview of the main structural and geometrical features of the paris basin inversion structures major unconformities as well as permo carboniferous basins we also describe the structural pattern and show the close relationships between the faults geometry the faults density and the geological evolution of the paris basin we distinguish 1 few large scale polyphase faults with a variscan origin representing the first order structural frame of the paris basin 2 monophase normal faults with strike slip features representing the subsurface prolongation of cenozoic grabens cropping out in the neighbourhood 3 deep normal faults sealed by the base calcareous dogger sequence related to the permo liassic extensional tectonic regime this large scale view of the paris basin has highlighted several potential exploration targets

fault plane solutions for the 1984 morgan hill california earthquake sequence evidence for the state of stress on the calaveras fault fault plane solutions for 946 aftershocks of the april 24 1984 morgan hill california m6 2 earthquake reveal a pattern of complex faulting within a 10 km wide zone surrounding the calaveras fault the fault plane solutions fall into three groups strike slip mechanisms located along the calaveras fault with north northwest striking dextral slip planes nearly parallel to the fault strike slip mechanisms located northeast of the calaveras fault with north striking dextral slip planes and reverse mechanisms located southwest of the calaveras fault with northeast or southwest dipping slip planes the average azimuth of p axes for aftershocks located on the calaveras fault is n10 1 e in contrast the average azimuths of p axes for aftershocks northeast and southwest of the calaveras fault are n49 7 e and n37 3 e respectively by assuming that the earthquakes occur on preexisting cracks in response to a uniformly oriented regional stress field we are able to infer from the observed average slip directions an orientation for 1 the axis of maximum horizontal compression 63 80 from the local strike of the calaveras fault such a high angle orientation of 1 is incompatible with the classical andersonian model of strike slip faulting but is consistent with an alternate model in which a weak calaveras fault is driven by plate motion slightly convergent with respect to the san andreas fault system in central california if this inferred high angle uniform stress field is combined with the changes in the static stress field calculated with elastic dislocation theory for the 1984 morgan hill main shock the resulting stress field predicts most of the observed spatial pattern of the aftershocks and their fault plane solutions the orientations of the inferred aftershock slip planes are generally consstent with the fracture orientations predicted by the coulomb failure criterion areas with predicted increases in the coulomb failure function of only a few tenths of a megapascal correspond to areas of intense aftershock activity the invariance of focal mechanisms in the vicinity of the south end of the main shock rupture before and after the main shock suggests that the magnitude of compressive stress in this area is at least 10 mpa in addition to explaining a preponderance of the seismic observations of the aftershock sequence the presence of a predominantly fault normal compressive regional stress field accounts for the contemporary development of folds reverse faults and topographic relief observed throughout the central california coast ranges

the carnian pluvial event in western europe new data from iberia and correlation with the western neotethys and eastern north america nw africa regions abstract at the beginning of the late triassic a period of increased precipitation occurred over large tracts of central pangea the carnian pluvial event it was a short lived event 1 ma coeval with a marked sea level fall and active rifting new and classical sections of carnian age in the iberian peninsula have been studied and a new correlation scheme is proposed for the iberian domain integrating field data and subsurface electric log data this is the first time that the portuguese and spanish late triassic carnian sediments are correlated the carnian pluvial event is identified in the iberian peninsula as a continental clastic wedge manuel fm and coeval sediments in between marine evaporite formations during a marked sea level drop event its age is considered to be julian early carnian by palynological and paleogeographic considerations a new correlation of the late triassic sediments of the iberian peninsula with coeval sediments of western europe nw africa and eastern north america is proposed and a new paleogeographical map of central eastern pangea for this period is presented in order to demonstrate that the geographical extent of the siliciclastic sediments related to the carnian pluvial event was much larger than accepted before

formation of volcanogenic massive sulfide deposits the kuroko perspective abstract the main objective of this paper is to identify the geochemical hydrological igneous and tectonic processes that led to the variations in the physical size geometry and chemical mineralogy metal ratios and zoning characteristics of volcanogenic massive sulfide deposits with respect to space from a scale of mining district size area to a global scale and time from a all volcanogenic massive sulfide deposits vmsds appear to have formed in extensional tectonic settings such as at mid ocean spreading centers backarc spreading centers and intracontinental rifts and failed rifts all vmsds appear to have formed in submarine depressions by seawater that became ore forming fluids through interactions with the heated upper crustal rocks submarine depressions especially those created by submarine caldera formation and or by large scale tectonic activities e g rifting become most favorable sites for the formation of large vmsds because of hydrological physical and chemical reasons the fundamental processes leading to the formation of vmsds include the following six processes 1 1 intrusion of a heat source typically a 10 3 km size pluton into an oceanic crust or a submarine continental crust causes deep convective circulation of seawater around the pluton the radius of a circulation cell is typically 5 km the temperature of fluids that discharge on the seafloor increases with time from the ambient temperature to a typical maximum of 350 c and then decreases gradually to the ambient temperatures in a time scale of 100 to 10 000 years the majority of sulfide and sulfate mineralization occurs during the waxing stage of hydrothermal activity 2 2 reactions between low temperature t 2 4 as disseminated gypsum and anhydrite in the country rocks 3 3 reactions of the modified seawater with higher temperature rocks at depths during the waxing stage cause the transformation of the seawater to metal and h 2 s rich ore forming fluids the metals and sulfide sulfur are leached from the county rocks the previously formed gypsum and anhydrite are reduced by fe 2 bearing minerals and organic matter providing additional h 2 s the mass of high temperature rocks that provide the metals and reduced sulfur is typically 10 11 tons 40 km 3 in volume the roles of magmatic fluids or gases are minor in most massive sulfide systems except for so 2 to produce acid type alteration in some systems 4 4 reactions between the ore forming fluids and cooler rocks in the discharge zone cause alteration of rocks and precipitation of some ore minerals in the stockwork ores 5 5 mixing of the ore forming fluids with local seawater within unconsolidated sediments and or on the seafloor causes precipitation of primitive ores with the black ore mineralogy sphalerite galena pyrite barite anhydrite 6 6 reactions between the primitive ores with later and hotter hydrothermal fluids cause transformation of primitive ores to matured ores that are enriched in chalcopyrite and pyrite variations in the mineralogical and elemental characteristics the geometry and the size of submarine hydrothermal deposits are controlled by the following four parameters 1 a the chemical and physical characteristics of seawater composition temperature density which depend largely on the geographical settings e g equatorial evaporating basins 2 b the chemical and physical characteristics of the plumbing system lithology fractures 3 c the thermal structure of the plumbing system which is determined largely by the ambient geothermal gradient and the size and temperature of the intrusive and 4 d the physical characteristics of the seafloor depth basin topography for example the submarine hydrothermal deposits developed in basaltic plumbing systems are generally poor in pb and ba compared to those developed in felsic plumbing systems the lower temperature systems are generally poorer in sulfides but richer in iron oxides and sulfates the higher temperature and larger hydrothermal systems tend to produce chalcopyrite and pyrite rich ores contrasts in the metal ratios between the noranda type archean vmsds and the younger vmsds reflect the differences in the geothermal gradient of the plumbing systems the submarine hydrothermal deposits developed in the near equatorial regions tend to form large continuous bedded type ores because of the likeliness of creating large stratified basins the basic processes of submarine hydrothermal mineralization have remained essentially the same throughout the geologic history from at least 3 5 billion year ago to the present

seismicity induced by gas production i correlation of focal mechanisms and dome structure from august 1976 to june 1979 more than 220 seismic events were recorded by a 7 station network operating over an active gas field in france 120 earthquakes with magnitudes greater than 1 0 were selected for a detailed study in order to understand the seismic response to a decrease in the gas reservoir pressure of 50 mpa composite focal mechanisms were determined for these events we found that where preexisting fractures were known from well logs faults with the most favorable orientation were reactivated in the part of the gas field where no preexisting faults were known orientation of the fracture planes was close to the orientations of stratigraphic interfaces our kinematic model constrained by the distribution of the earthquakes and their focal mechanisms consists of the downward dropping of a block located close to the top of the gas field the main faults as defined by the spatial density of the seismic activity define the limits of this block the displacements observed along these faults can be either normal or reverse mechanism dependent on the preexisting orientation of each fault another important result is the evidence that the depletion of the gas reservoir exerts the major influence on local seismic displacements obscuring the effect of regional setting

evidence for remotely triggered microearthquakes during salt cavern collapse summary microseismicity is a good indicator of spatio temporal evolution of physical properties of rocks prior to catastrophic events like volcanic eruptions or landslides and may be triggered by a number of causes including dynamic characteristics of processes in play or and external forces we show evidence of triggered microseismicity observed in the vicinity of an underground salt cavern prone to collapse by a remote m 7 2 earthquake which occurred 12 000 km away high dynamic range broad band records reveal the strong time correlation between a dramatic change in the rate of local high frequency microseismicity and the passage of low frequency seismic waves including body love and rayleigh surface waves pressure was lowered in the cavern by pumping operations of brine out of the cavern we demonstrate the near critical state of the cavern before the collapse by means of 2 d axisymmetric elastic finite element simulations on this basis we show that the increment of stress necessary for the failure of the dolomite layer which ensures the stability of the whole system is of the same order of magnitude as the maximum dynamic stress magnitude observed during the passage of the earthquakes waves this suggests that the stress oscillations due to the seismic waves correlated with the recorded microearthquakes induced damage of the overburden which eventually led to the collapse of the salt cavern we show that the contribution of rayleigh waves is the most efficient to trigger microseismicity at periods close to the natural fundamental frequency of the cavern system found at about 10 20 s by investigating the impulse response of the cavern overburden brine system

sulfur isotope evidence for magmatic contributions to submarine and subaerial gold mineralization conical seamount and the ladolam gold deposit papua new guinea conical seamount is a submarine alkali basalt volcano situated 10 km south of lihir island in the tabar feni island chain papua new guinea polymetallic zn pb ag au as sb veins pyritic stockwork and hydrothermally altered rocks discovered on the summit of conical seamount represent a unique example of submarine gold mineralization with mineralogical chemical and textural characteristics common to some subaerial epithermal systems the giant ladolam epithermal gold deposit 42 moz au is situated in the crater of an alkali stratovolcano on lihir island portions of the epithermal mineralization and alteration assemblages at ladolam are similar to those observed on conical seamount conical seamount has the lightest hydrothermal i e nondiagenetic sulfide d34s values 17 5 to 6 1 measured to date from modern sea floor hydrothermal systems a previous model for the conical seamount hydrothermal system suggested a contribution of magmatic volatiles in the earliest stages of mineralization stage 1 followed by a combination of sulfur leached from the underlying volcanic rocks and reduced seawater sulfate during the main base and precious metal precipitating event stage 2 new sulfur isotope data allow a reinterpretation of this model that suggests a greater input of magmatic volatiles plus boiling throughout both stage 1 and 2 mineralization sulfides from the ladolam gold deposit have a range of sulfur isotope values 12 9 to 3 6 similar to that of conical seamount these sulfur isotope data have previously been interpreted as the result of magmatic volatiles escaping from a crystallizing magma and mixing with dilute meteoric ground water anhydrite associated with the gold mineralization has two populations of d34s values 8 14 and 20 22 which indicate the interaction of magmatic volatiles with seawater that has previously been discounted the range of sulfide and sulfate d34s values at ladolam is reinterpreted to be due to a complex interaction of magmatic hydrothermal fluids meteoric ground water and seawater native sulfur in thermal areas in luise caldera and pyrite in offshore hydrothermal vents in luise harbor have similar d34s values to the ladolam epithermal mineralization indicating that fluids similar to the young ladolam ore forming event are still reaching the floor of luise caldera sulfur isotope data from conical seamount and the ladolam deposit suggest that magmatic volatiles have contributed a significant amount of sulfur to both these gold rich hydrothermal systems

strata bound copper iron sulfide mineralization in a proterozoic front arc setting at boksputs northwest cape south africa a possible besshi type deposit a low grade copper iron sulfide deposit is present at boksputs in the northwest cape south africa it occurs in the proterozoic amphibolite belt the areachap group along the eastern margin of the namaqua mobile belt

review of published rockburst events and their contributing factors abstract through a review of selected published case study data from around the world in situ conditions that contribute to rockburst events have been identified this review was carried out to assist research associated with developing numerical modelling techniques to reproduce rockbursting within a large scale mine models for predictive purposes contributing factors identified through the case study review include unfavourable stress states excavation geometry size and orientation in relation to the principal stresses and rate and direction of advance factors also incorporated unfavourable rock mass characteristics that included mineralogy contrasts in geomechanical properties and geological intensifiers dykes faults etc

seismic tomography in the ostrava karvina mining region the effective algorithm of seismic tomography was applied to the simultaneous determination of the velocity field in the medium and the location of hypocentres of events in the area of the underground seismological network in the ostrava karvina mining region okr although the configuration of the network is unsuitable and the used data are relatively unreliable after classifying the data it is possible to obtain representative information that demonstrates the existence of significant inhomogeneities of the medium in the area under study in addition it is possible to obtain more precise hypocentre parameters of local seismic events

mining induced microseismic event location errors accuracy and precision of two location systems the accuracy and precision of microseismic event locations were measured analyzed and compared for two types of location systems anolog and digital in the first system relative times of first arrival were estimated from analog signals using automated hardware circuitry station positions were estimated from mine map coordinates and event locations were determined using the bld blake leighton and duvall direct solution method in the second system arrival times were manually measured during interactive displays of digital waveforms station coordinates were surveyed and the sw gbm salamon and wiebols godson bridges and mckavanagh direct basis function was used to solve for locations both systems assume constant isotropic seismic velocity of slightly different signals data sets calibration blast signals with known source site and origin time and microseismic event signals were recorded by each location system employing the same array of high frequency 5 khz accelerometers with 150 m maximum dimension the calibration blast tests indicated a location precision of 2 m and accuracy of 10 m for the analog system location precision and accuracy for the digital system measured 1 m and 8 m respectively numerical experiments were used to assess the contributions of errors in velocity arrival times and station positions on the location accuracy and precision for each system measured and estimated errors appropriate to each system for microseismic events were simulated in computing source locations for comparison with exact synthetic event locations discrepancy vectors between exact locations and locations calculated with known data errors averaged 7 7 and 1 4 m for the analog and digital systems respectively these averages are probably more representative of the location precision of microseismic events since the calibration blast tests produce impulsive seismic arrivals resulting in smaller arrival time pick errors in the analog system for both systems location accuracy is limited by inadequate modeling of the velocity structure consequently when isotropic velocity models are used in the travel time inversions the increased effort expended with the digital location system does not for the particular systems studied result in increased accuracy

besshi type vms deposits of the rudny altai central asia for the first time in the rudny altai we propose to distinguish besshi and kuroko type deposits previously considered as members of a single massive sulfide polymetallic group the ores of the two deposit types differ in mineral composition with pyrite pyrrhotite chalcopyrite sphalerite mineralization in the besshi type deposits versus pyrite sphalerite galena chalcopyrite gold mineralization in the kuroko type deposits the besshi type deposits are restricted to the irtysh terrane and associated with deformed and metamorphosed greenschist to mid amphibolite facies mafic siliciclastic rock sequences this contrasts with the well preserved kuroko type deposits hosted in bimodal volcanic sequences in the devonian carboniferous rudny altai magmatic arc our u pb 40ar 39ar and re os isotope dating of sulfides and host rocks of the besshi type deposits suggests that they were probably formed during the early paleozoic in a back arc rift setting they were then metamorphosed during devonian times within the accretionary wedge in front of the rudny altai arc synchronously with formation of the kuroko type deposits

moment tensors and other source parameters of mining induced earthquakes in tautona mine south africa abstract induced seismicity exhibits diverse source mechanisms that are often difficult to constrain for small events here we use data from the in mine seismic network the natural earthquake laboratory in south african mines network and a temporary program for the array seismic studies of the continental lithosphere deployment in tautona mine south africa to determine full moment tensors of 100 mining induced earthquakes in the magnitude range 2 7 m w f test to determine the need for including an isotropic component with an extra degree of freedom in the solution the results indicate 82 of the events have well constrained solutions and 45 of the well constrained events require an isotropic source term throughout the magnitude range both deviatoric and implosive mechanisms are observed with implosive ratios of volume change to shear deformation v of 1 03 to 0 15 two explosive events are observed at m w 0 5 and 0 2 with v 0 15 and 0 51 respectively for the largest events we determine maximum slip and apparent stress a and find values consistent with those of natural tectonic earthquakes with 0 1 a 9 2 mpa our results support previous speculation on the nature of isotropic components of mining induced earthquakes in which events of all sizes begin as shear failure that may intersect a void tunnel or stope and cause collapse whereas only small events result in explosive sources

source parameters and rupture velocity of small m 2 1 reservoir induced earthquakes summary we calculate stress drop and rupture speed for ml 2 1 shallow reservoir induced earthquakes and find them to be similar to those of large natural earthquakes previous studies have suggested that hydrofractures mining and reservoir induced earthquakes have lower average stress drop than natural tectonic earthquakes this difference might result from the different tectonic setting or the shallower hypocentral depths of induced earthquakes alternatively difficulties in correcting for attenuation and site effects in earlier studies may lead to underestimation of stress drop in addition most studies assume the rupture velocity of small reservoir induced earthquakes to be the same as for the large earthquakes we analyse a set of 101 ml 2 1 earthquakes induced by changing water level in the acu reservoir ne brazil the earthquakes are shallow depth 5 km and the region has negligible natural seismicity we use three different approaches to calculate the source parameters of the six largest 1 9 ml 2 1 earthquakes we model the individual spectra to find corner frequency frequency independent q and long period amplitude we use collocated small earthquakes as empirical green s functions to calculate the spectral ratios and determine the relative source time functions estimates of the source duration and corner frequency imply stress drops in the range of 26 179 mpa these are similar to or higher than tectonic earthquakes suggesting that the shallow hypocentral depth and the presence of water do not affect stress drop we observe clear directivity for one of the earthquakes and use the azimuthal variation in pulse width to estimate a rupture velocity of 0 6

seismic event discrimination abstract discrimination of small events begins with detection association and location recent advances in detection include use of updated measures of the noise variance to control the false alarm rate and updating the noise amplitude spectrum n for application of the optimum detection filter s n 2 where s is the signal spectrum postdetection processes of interest include determination of signal azimuth and emergence angle from linear three component processing association programs have recently been improved by implementation of techniques taking advantage of information provided by arrays location advances include modification of the a priori travel time residual covariance matrix to account for the fact that travel time residuals are correlated at stations near to each other simultaneous determination of location and phase velocity when using regional phases and direct use of phases other than p e g pg lg s pp and pkpbc according to most source theories small earthquakes and explosions have the same flat displacement spectrum for p waves at teleseismic frequencies aside from location discrimination therefore rests on focal mechanism differences and generation of shear waves by earthquakes the m s m b discriminant rests on the shear wave generation but there is overlap of explosions and earthquakes at low magnitudes for dip slip earthquakes low frequency 0 3 hz p waves are weak from explosions due to the surface pp reflections p pp amplitude ratios for earthquakes vary over the focal sphere in a way impossible for a pair of explosions regional discrimination shows promise in the ratio of maximum amplitudes before and after sn and in the observed fact that shear phases from explosions detonated near high impedance contrasts are of lower frequency than those from earthquakes in the same region possibly due to the generation of the explosion shear phases by p to s scattering recent experimental analyses show that there is almost no decoupling at high frequencies in agreement with earlier theories these frequencies may be observable at regional distances

observations of heterogeneous stope convergence behavior and implications for induced seismicity analysis of stope convergence measurements in a burst prone lead zinc silver mine is being used by the u s bureau of mines to study rock burst processes three convergence gages were installed in a 3 m wide stope of the galena mine with an inter gage distance of approximately 8 m the two month period immediately after installation during which the subsequent cut of the pillar was made is the subject of the analysis described in this paper microseismicity rates and locations local magnitude 5 and above were also recorded during this period coseismic convergence steps within the 10 minute sample interval are observed at various times on all three gages the convergences of the three gages do not track one another indicating the blocky nature of deformation in this stope at a 10 meter or smaller size scale the behavior of the three gages is different with respect to coseismic and interseismic convergence during the study period for one of the gages 82 of total closure occurs coseismically the other two gages show much smaller percentages of coseismic convergence 30 and 35 and proportionately higher percentages of interseismic steady creep this heterogeneous convergence behavior may be indicative of the relative stability of the faults in the vicinity of each gage an examination of stability models shows that the mine geometry related spatial variation in normal stress acting on an existing set of faults may explain the observed behavior

stable isotope signatures of water rock interaction in mid ocean ridge hydrothermal systems sulfur oxygen and hydrogen reaction path models of seawater basalt interaction at mid ocean ridges similar to those presented by bowers and taylor 1985 are extended to include sulfur isotopic exchange equilibria the effects of variable contribution of sulfur from basalt and of high and low temperature reduction of sulfate in the fluid are considered results of the model calculations are compared with 34s analyses of disseminated sulfides in altered basalts chimney sulfides and fluids collected from mid ocean ridge hot springs the calculations indicate that under the physical conditions of water rock interaction in mid ocean ridge circulation systems the overwhelming influence on the sulfur isotope signature of exiting fluids is basaltic sulfur no trace of 34s enrichment by reduction of seawater sulfate is recorded in hot spring fluids unless the reduction occurs at high temperature 350 c or near the venting areas a comparison of recent oxygen and hydrogen isotope data from several vent sites suggests that contributions of altered basalt and fluid with a significant history of low temperature interaction with basalt can be qualitatively assessed

high resolution sequence stratigraphy of an alluvial fan fan delta environment stratigraphic and geodynamic implications an example from the keuper chaunoy sandstones paris basin abstract facies analysis of the chaunoy formation conducted as the first stage of this study reveals that the corresponding fluvial system essentially involved bedload deposition 2 d and 3 d megaripple migration and debris flow deposition such processes are characteristic of alluvial fan depositional environments these alluvial fan deposits pass laterally eastward into a shallow lacustrine environment in stage 2 of the study electrofacies are defined by well log analysis and then matched with sedimentary facies defined by core analysis electrofacies associations and depositional environments are then inferred directly from well logs on this basis six electrofacies characterizing the main sedimentary facies associations and depositional environments within the chaunoy formation are defined channel lag deposits channel infilling lake or flood plain overflow deposits and paleosols stage 3 involves establishing correlations based on high resolution sequence stratigraphy within these continental deposits the procedure consists in analysing high frequency fluctuations in baselevel defined from sedimentological studies and calibrated on well log signatures the correlations show that the top of the chaunoy formation is diachronous the formation is subdivided here into three stratigraphic units from base to top chaunoy i ii and iii this study shows that the degree of preservation of continental deposits varies with stratigraphic cycle genetic sequences and genetic sequence sets are asymmetrical with the baselevel rise being better preserved than the baselevel fall while for minor cycle deposits may be similarly preserved during baselevel rise and fall the sequence stratigraphy pattern of the genetic sequences and the genetic sequence sets can result from climatic and or tectonic factors but their effects are difficult to distinguish at the scale of the minor chaunoy i cycle or the chaunoy ii cycle preservation is similar during the baselevel rise and fall that implies that the chaunoy minor cycles were influenced by load discharge resulting in greater accommodation space which could result from climatic or tectonic fluctuations the chaunoy formation was deposited as part of a major baselevel rise during the carnian liassic cycle during this cycle the paris basin was generally tilted to the northwest producing the intra marnes irisees superieures truncation which seems to have been induced by large scale wavelength tectonic deformation detailed isopach maps of minor baselevel cycles in chaunoy i with inferred depositional environments are used to define the extent of depositional environments and fault activity during baselevel rise and fall during emplacement of the braided alluvial fan and lacustrine deposits of the chaunoy formation fault activity which was confined to the western part of the basin controlled the preservation potential i e the thickness of the deposits and depositional environment profiles within the chaunoy i and ii cycles the increased thickness of the sandstone deposits to the northeast and the onlap at the top of chaunoy i can be explained by local fault activity and by the general tilting of the basin the chaunoy iii sandstones are confined to the western part of the basin and seem to have been controlled by local factors only

mining induced seismicity in faulted geologic structures an analysis of seismicity induced slip potential relationships between the locations of mining induced seismic events local fault structure and mine geometry were examined in a deep hard rock mine in northern idaho stopes experiencing rock bursts and other large seismic events were found to fall into two structural regimes the silver vein and the n48 w trend a steeply dipping plane of seismic activity that is subparallel to major local steeply dipping faults which bound blocky structures the n48 w trend also intersects a shaft that was seriously damaged when fault gouge was expelled into the opening during a 3 month period of high seismic energy release models of stress interaction are used to support the hypothesis that mining induced deformation was mobilized along a 1 5 km length of the n48 w trend specifically numerical models are used to simulate rupture of seismic events and estimate induced changes in the quasi static stress field a coulomb failure criterion is used with these results to estimate the spatial variation in potential for slip on planes parallel to local faulting increases in the potential for slip on fault planes subparallel to the n48 w trend are consistent with activation of deformation along its 1 5 km length for events with constant seismic moment stress drop is shown to be far more important than source dimension in elevating slip potential along the observed plane of seismic activity

a collision related pressure temperature time path for prieska copper mine namaqua natal tectonic province south africa abstract prieska copper mine lies in highly metamorphosed gneisses of the 1100 ma namaqua natal tectonic province of south africa close to its boundary with the kaapvaal craton the complex stratigraphy of the mining district is thought to have formed in a 1300 ma arc environment while the ore is regarded as a volcanogenic massive sulphide deposit petrographic study of key peraluminous and metabasic rock types led to the recognition of four principal metamorphic events m 1 4 which together with three deformation phases constitute an orogenic cycle staurolite garnet kyanite m 1 parageneses reflect medium pressure metamorphism but are largely obscured by the dominant m 2 muscovite free cordierite garnetsillimanite assemblages the latter reflect the metamorphic peak at about 730 c and 4 1 kbar with partial melting suppressed by dry conditions m 2 peak temperatures at different localities within the 30 km long mining district vary between 550 and 800 c suggesting a localized heat source m 3 sillimanite phlogopite grain boundary reactions represent a brief hydration event in p t conditions close to those of m 2 m 4 parageneses which feature retrograde kyanite staurolite garnet muscovite and chlorite are developed only in f 3 shear zones and represent a near isobaric return to a geotherm close to that which prevailed during m1 p t data for the metamorphic cycle is integrated with comprehensive geochronology to develop a model ptt path for the prieska mine region the model envisages an orogenic cycle at the end of a 1300 900 ma wilson cycle characterised by collision crustal thickening followed by a long period of uplift and erosion the peak metamorphic conditions are ascribed to two short lived essentially contact metamorphic events due to the intrusion of the plat sjambok anorthosite suite the 400 ma wilson cycle 300 ma orogeny and 0 05 mm yr uplift rate envisaged for prieska mine are long and slow compared with phanerozoic examples however similar parameters seem to characterize more than one proterozoic event

geochemical characteristics of pyrite in the dabaozhuang deposit in the middle lower yangtze river metallogenic belt eastern china abstract dabaozhuang is a pyrite deposit in the luzong volcanic basin eastern china and has similar exhalation sedimentary features to volcanic massive sulfide deposits vms which commonly form in seawater to better understand the ore forming process of this special type of deposit we employed shrimp si and la icp ms to measure sulfur isotope and trace element compositions of anhydrite and four types of pyrite from the dabaozhuang deposit shrimp in situ sulfur isotope analysis indicates a narrow range in 34s of anhydrite 21 0 21 7 and variable ranges for pyrite 9 9 10 7 for pyrite vein in the deep py i 9 2 to 2 0 for cyclic annular and oval shaped pyrite in massive ore py ii 3 1 5 3 for massive or disseminated pyrite in the footwall tuff and hematite py iii and 29 7 to 30 4 for euhedral and coarse pyrite in the carbonate cement py iv 33s and 36s in four types of pyrite have no abnormal values indicating that sulfur isotope fractionation is mainly controlled by thermochemical sulfate reduction tsr the higher 34s values in type i pyrite and anhydrite indicate a mixing process of magmatic fluid and evaporates at depth py ii and iv have negative 34s data indicating the formation temperature of pyrite decreases because of the mixing of lake water 34s values in py iii are close to magmatic sulfur which shows the igneous sulfur tuff is an important sulfur source for the disseminated mineralization cobalt and ni content also show that the formation temperature of py i is highest and py iv is lowest this research indicates that the vms like deposits could be formed in continental volcanic lakes and are genetically related to so42 rich ioa iron oxide apatite deposits

source parameters of small earthquakes recorded at 2 5 km depth cajon pass southern california implications for earthquake scaling a 2 5 km deep triaxial seismometer at cajon pass in southern california has recorded several hundred earthquakes ml4 0 occurring within the san andreas fault system at 2 5 km seismic background noise is below amplifier sensitivity and the 2 250 hz spectral range of recorded seismic motion is wider and higher than that of most natural event catalogs compared with downhole recorded motion seismic amplitudes at the surface are amplified below 10 hz and severely attenuated above 30 hz we estimate that qs is at least 1000 for wave motion at 2 5 km and below and qp is over 2000 the range of source dimensions in the downhole recorded catalog is 10 m to 70 m ml 2 0 mo 108 nm to ml 2 7 mo 1013 nm the plot of log source radius vs log moment has a straight line trend compatible with earthquake scaling at constant stress drop inferred stress drops are scattered between 1 and 500 bars there is no evidence in the catalog for the proposed minimum source dimension at 100 m when the cajon pass borehole catalog containing some of the smallest recorded natural earthquakes is combined with 800 larger events from previous studies the moment radius trend suggests that natural earthquakes are self similar over a magnitude range m 2 to 8 we suggest that inferences of minimum source dimension are more likely due to bias in bandlimited individual catalogs than to properties of the seismic crust

the response of creeping parts of the san andreas fault to earthquakes on nearby faults two examples rates of shallow slip on creeping sections of the san andreas fault have been perturbed on a number of occasions by earthquakes occurring on nearby faults one example of such perturbations occurred during the 26 january 1986 magnitude 5 3 tres pinos earthquake located about 10 km southeast of hollister california seven creepmeters on the san andreas fault showed creep steps either during or soon after the shock both left lateral ll and right lateral rl steps were observed a rectangular dislocation in an elastic half space was used to model the coseismic fault offset at the hypocenter for a model based on the preliminary focal mechanism the predicted changes in static shear stress on the plane of the san andreas fault agreed in sense ll or rl with the observed slip directions at all seven meters for a model based on a refined focal mechanism six of the seven meters showed the correct sense of motion two possible explanations for such coseismic and postseismic steps are 1 that slip was triggered by the earthquake shaking or 2 that slip occurred in response to the changes in static stress fields accompanying the earthquake in the tres pinos example the observed steps may have been of both the triggered and responsive kinds a second example is provided by the 2 may 1983 magnitude 6 7 coalinga earthquake which profoundly altered slip rates at five creepmeters on the san andreas fault for a period of months to years the xmm1 meter 9 km northwest of parkfield california recorded ll creep for more than a year after the event to simulate the temporal behavior of the xmm1 meter and to view the stress perturbation provided by the coalinga earthquake in the context of steady state deformation on the san andreas fault a simple time evolving dislocation model was constructed the model was driven by a single long vertical dislocation below 15 km in depth that was forced to slip at 35 mm yr in a rl sense a dislocation element placed in the seismogenic layer under xmm1 was given a finite breaking strength of sufficient magnitude to produce a parkfield like earthquake every 22 years when stress changes equivalent to a coalinga earthquake were superposed on the model running in a steady state mode the effect was to make a segment under xmm1 that could slip in a linear viscous fashion creep ll and to delay the onset of the next parkfield like earthquake by a year or more if static stress changes imposed by earthquakes off the san andreas can indeed advance or delay earthquakes on the san andreas by months or years then such changes must be considered in intermediate term prediction efforts

continuous catchment scale monitoring of geomorphic processes with a 2 d seismological array 1 distributed activity of geomorphic processes with different spatiotemporal scales is hard to monitor in detail with conventional methods but might be detected with seismometers from july to september 2010 we deployed 14 seismometers to evaluate the ability of a two dimensional array with small interstation distances 11 km to continuously monitor geomorphic processes in a mountain catchment 370 km2 in taiwan spectral analysis of seismic records highlights different sources with high frequency content 1 hz consistent with hillslope and river processes using a common detection algorithm and a location technique based on the timing of seismic amplitude we have located 314 near surface events most of which 69 occurred during daily convective storms event activity was positively correlated with the precipitation intensity but this relation was not uniform in the catchment high resolution satellite images and air photos did not show geomorphic change during the study which did not have any episodes of extreme precipitation a majority of events 61 were collocated with preexisting geomorphic features landslide scars gullies within the uncertainty on location 9 of interstation distance the combination of event location and timing suggests a geomorphic source of recorded signals and most events had the seismic characteristics of rockfall debris avalanches or slides reactivation of prior erosion sites by such processes is difficult to detect with imagery but can possibly be resolved by seismic monitoring when proven this approach will allow a spatially comprehensive survey of geomorphic activity at the catchment scale with temporal detail sufficient to evaluate the exact meteorological conditions under which process events occur

three dimensional accommodation analysis of the keuper of the paris basin discrimination between tectonics eustasy and sediment supply in the stratigraphic record abstract during the keuper the paris basin was an intracratonic sedimentary basin filled by continental deposits using paleo environmental isopach and paleo altitude maps we estimate the variations of accommodation rate at the scale of stratigraphic minor hemi cycle 1 3 ma an analysis of the short and long wavelength accommodation variations allows us to assess the relative influence of tectonics eustasy and sediment supply on the stratigraphic record our data suggest a pattern of subsidence along three trends e w in the carnian e w to nne ssw in the norian and ne sw in the norian rhaetian during the keuper the paris basin accurately records the different phases of the opening of the tethys ocean associated with a rotation of the extension direction the norian cycle could thus reflect the intraplate stresses in a transitional period between the triassic and the liassic

brine pool deposition for the zn pb cu massive sulphide deposits of the bathurst mining camp new brunswick canada i comparisons with the iberian pyrite belt abstract the ordovician zn pb cu massive sulphide ore deposits of the bathurst mining camp share many features with those of the devonian carboniferous iberian pyrite belt particularly the tendency to large size tonnage and metal content shape as far as can be determined after allowing for deformation metal content particularly fe cu pb zn and sn mineral assemblages pyrite arsenopyrite pyrrhotite and lack or rarity of sulphates sulphide textures particularly framboidal pyrite lack of chimney structures and rubble mounds irregular metal or mineral zoning and the low degree of zone refining compared to hokuroku ores the major differences between the provinces are the lack of vent complexes and the presence of sn cu ores in the iberian pyrite belt there are also similarities in the geological setting of the two camps both lie within continental terranes undergoing arc continent and continent continent collision and in each case massive sulphide mineralisation followed ophiolite obduction the ore deposits are associated with bimodal volcanic rocks derived from morb and continental crust and marine shales and mineralisation was locally accompanied or followed by deposition of iron formations fluid inclusion data from veins in stockworks from at least six of the iberian massive sulphide deposits point to sulphide deposition having taken place in basins containing mostly spent saline ore forming fluids brine pools and it is suggested that most of the major features of the bathurst deposits can be explained by similar processes the proposed model is largely independent of ocean sulphate and o 2 content whereas low values of each are requisites for the current spreading plume model of sulphide deposition in the bathurst camp

rare earth element and isotopic evidence for the genesis of the prieska massive sulfide deposit south africa the prieska orebody is contained in high grade metamorphic peraluminous rocks birdwing shaped rare earth element profiles and high epsilon nd values are observed in rocks under the ore these characteristics are interpreted to reflect an early magmatic dominated alteration stage during which heavy rare earth elements and highly radiogenic nd were added to the rocks rocks studied above the ore display normal rare earth element profiles and country rock epsilon nd the generally high mg fe ratios of all the altered rocks are thought to indicate pervasive late alteration by seawater derived fluids the alteration processes appear to be linked to the cooling of a hypothetical high level intrusion derived from the depleted mantle the existence of this type of magmatism is also indicated by the occurrence of amphibolites higher up in the sequence which have flat rare earth element profiles and high epsilon nd

sequence architecture within a low accommodation setting an example from the permian of the galilee and bowen basins queensland australia the coal bearing upper permian betts creek beds bcb of the northeastern intracratonic galilee basin in north central queensland australia record sedimentation within an alluvial coastal plain in a low accommodation basin margin setting six third order depositional sequences are preserved within the bcb and are characterized by a sequence architecture that is overall relatively thin 15 m 49 ft condensed and top truncated sequences have a lowstand systems tract composed of extensive braided fluvial sheet sandstones a transgressive systems tract characterized by tidally influenced fluvial sheet sandstones and bioturbated estuarine mudrocks and a highstand systems tract composed of coastal plain mudrocks and coals sequences can be correlated throughout the entire galilee basin and related to the lithostratigraphy established in the adjacent bowen basin a foreland basin to the east the overall late permian fill is considered a second order sequence the stacking patterns show an overall retrogradational to progradational architecture suggestive of relatively low accommodation space sequences show an extremely laterally continuous geometry 1000 km 600 mi and are relatively uniform in thickness sequences do not show evidence of onlap toplap or erosional truncation but instead are thin in areas of low accommodation and expand into areas of higher accommodation that these third order sequences can be traced across basins with differing tectonic regimes together with the persistent sheetlike nature of the sequences suggests that tectonic effects on the sequence architecture were minimal the basin fill covers a time interval during which two glacial events occurred in the final stages of the late paleozoic ice age suggesting that changes in glacioeustasy may have been the dominant controls on the sequence architecture of the late permian succession in the galilee basin of northeastern australia

age and primary architecture of the copperton zn cu vms deposit northern cape province south africa abstract the prieska copper mine copperton deposit located in the northern cape province of south africa exploited from 1972 to 1994 a very large ca 47 mt pre mining resource massive sulphide lens containing on average ca 1 cu and 2 zn the orebody occurred as a stratiform stratabound tabular lens hosted by the subvertically dipping copperton formation which is part of the intensely deformed and highly metamorphosed areachap group the latter represents a 1 3 1 24 ga continental volcanic island arc that was accreted onto the western margin of the kaapvaal craton during the initial stages of the 1 2 1 0 ga namaquan orogeny the present contribution is aimed at resolving important uncertainties surrounding the architecture age and origin of this world class base metal deposit despite intense deformation and high grade metamorphism the original architecture of the deposit is found to be unusually well preserved with a stratabound zone of intense hydrothermal alteration below and a series of characteristic cap rocks above the massive sulphide orebody geochemical data and radiometric ages for host rocks and massive sulphide ores lead to the conclusion that the copperton deposit comprises a very large chimney type volcanogenic massive sulphide deposit that formed at 1 28 1 29 ga the deposit meets many of the criteria of the bimodal siliciclastic or bimodal felsic types of vms deposits

comparison of ground motion from tremors and explosions in deep gold mines seismic body waves from tamped chemical explosions two with yields of 50 and one of 150 kg were compared with corresponding data from three mining induced tremors with a view to testing methods of discriminating between the two types of events detonated at depths of about 2 km all three explosions generated p waves for which the low frequency spectral asymptotes agree well with corresponding results scaled down from nuclear shots at the nevada test site for the two smaller explosions recorded underground at hypocentral distances ranging from 234 to 871 m the p wave corner frequencies defined by the intersections of the low and high frequency asymptotes are also in fine agreement with scaled down results from the nevada test site for the 150 kg explosion which was recorded only at the surface it appears that 2 39 km of upward propagation caused the corner frequency to be at least a factor of 4 lower than anticipated due to attenuation all three explosions generated s waves that appear to be a consequence of deviatoric stress release in the immediate environs of the explosions the three tremors analyzed here generated p and s waves whose spectra and source parameters agree well with standard earthquake source models with regard to discrimination based on p wave spectra we conclude that for events of fixed low frequency spectral asymptotes the explosions typically have higher corner frequencies than tremors or earthquakes although counterexamples certainly exist interestingly the 150 kg explosion was identified as such on the basis of p and s wave polarities that are incompatible with the normally expected double couple source model instead these initial motions are consistent with an explosion in conjunction with normal faulting the body wave spectra of this explosion and those of a nearby tremor however were indistinguishable

mechanics of seismic instabilities induced by the recovery of hydrocarbons we review earthquake distributions associated with hydrocarbon fields in the context of pore pressure diffusion models poroelastic stress transfer and isostasy theory these three mechanisms trigger or induce seismic instabilities at both local scale d 5 km and at regional scale d 20 km the modeled changes in stress are small 1 mpa whatever the tectonic setting each mechanism corresponds to different production processes 1 local hydraulic fracturing due to fluid injection induces seismic slip on cracks ml 3 within the injected reservoir through decreasing the effective stress 2 pure fluid withdrawal causes pore pressure to decrease within the reservoir it triggers adjustments of the geological structure to perturbations related to the reservoir response to depletion poroelastic mechanisms transfer this stress change from the reservoir to the surrounding levels whereml 5 seismic instabilities occur either above or below the reservoir 3 massive hydrocarbon recovery induces crustal readjustments due to the removal of load from the upper crust it can induce larger earthquakes ml 6 at greater distance from the hydrocarbon fields than the two other mechanisms

seismicity and tectonic stress in the coeur d alene mining district abstract the coeur d9alene mining district lies within a minor zone of seismicity in northern idaho along the lewis and clark zone a 400 km long system of west northwest trending faults rockbursts seismic events that cause damage in mines have become increasingly common in the coeur d9alene district during recent years our epicenter map of the district shows only 52 seismic events since 1982 however magnitude frequency analysis suggests that regional seismograph coverage is complete only for events above magnitude 2 8 and that 90 per cent of the seismic events above magnitude 1 5 are not located by the regional seismograph network a fault plane solution for the 1 august 1988 magnitude 4 1 tectonic earthquake that occurred 15 km northeast of mullan idaho shows together with previous in situ stress measurements that the coeur d9alene mining district lies within a regional northeast southwest extensional regime with the maximum compressive stress directed northwest southeast this orientation is deleterious for mining as it favors right lateral slip on the steeply dipping west northwest trending faults and bedding planes common in the district low level seismicity in the immediate vicinity of the lucky friday mine is driven in the short term by mining rate as is evident from the decreased levels of seismic activity on weekends when mining does not take place in the longer term cycles of tectonic stress build up and release may be important large rockbursts at the mine seem to be followed by several months of seismic quiescence

trace elemental and sulfur lead isotopic variations in metamorphosed volcanogenic massive sulfide vms mineralization systems an example from the keketale pb zn ag deposit nw china abstract the effects of post vms volcanogenic massive sulfide deformation metamorphism on sulfide trace element and sulfur lead isotopic compositions remain unclear the greenschist to lower amphibolite facies metamorphosed keketale vms pb zn ag deposit located in the devonian maizi volcanic sedimentary basin in the chinese altay nw china provides an opportunity to resolve the abovementioned issue two mineralization stages are recognized at keketale including 1 primary banded massive and disseminated ores derived from sea floor hydrothermal mineralization and 2 ore remobilization as represented by intensively deformed ores and quartz polymetallic sulfide ore veins that crosscut the primary ores sulfide trace elements data suggest that stage ii pyrite and pyrrhotite have higher contents of cu zn ag sb and pb whereas contents of these elements are higher in stage i sphalerite and galena than their stage ii counterparts such elemental remobilization was probably caused by the rapid intragrain diffusion and subsequent fluid mediated liberation with trace elements re precipitated as particles within the same grain and nearby minerals respectively the 34scdt values in both stages show a trimodal distribution 25 9 to 22 7 17 0 to 10 6 and 0 6 to 2 1 sulfide mineral pairs formed during primary vms mineralization are not in sulfur isotopic equilibrium and only localized re equilibration occurs during deformation and metamorphism in addition the lead isotopic values of galena from remobilized sulfide veins overlap with those of the stage i galena and pyrite these data indicate that regional deformation and metamorphism of the keketale deposit can be approximated as a closed system in terms of sulfur lead isotopes whilst the presence of the anomalously low 34s values minimum 25 9 and the distinct lead isotopic ratios of sulfides from the calcite quartz veins argue for that in the late part of the metamorphic event some exotic lead and light sulfur were sourced from outside the ore field in situ 34s values of stage i sulfides vary widely 17 0 to 2 1 suggesting that the sulfur was originated from bacterial sulfate reduction bsr of marine sulfates with probably some magmatic input lead isotopes of the sulfides and mineralized meta sedimentary volcanic rocks display a linear distribution between the mantle and upper crust line in the 206pb 204pb vs 207pb 204pb diagram the lead source may be derived from both felsic volcanic rocks and mafic igneous rocks and or magmatic volatiles and the sulfur lead isotopes may result from a shallow level seawater circulating process an additional group of lead isotopic compositions of the meta volcanic rocks show elevated present day 206pb 204pb 207pb 204pb and 208pb 204pb values probably due to decay of th and u carried by deeply penetrative circulation 13 km of co2 f cl rich hydrothermal metamorphic fluids both syn vms shallow seawater and post vms deep metamorphic fluids circulation processes are critical for the metal concentration at keketale

numerical modelling of anomalous microseismicity influenced by lithological heterogeneity in longwall top coal caving mining abstract mining induced microseismicity has been extensively used to evaluate the potential for rock bursts and coal and gas outbursts in underground coal mines in a research project completed a few years ago it was observed that characteristics of microseismicity around a working longwall panel were fairly consistent over the monitoring period until a lithological heterogeneity zone with a relatively high coal strength was reached the current research presented in this paper aims at achieving a better understanding of the effect of lithological heterogeneity on microseismic activity in longwall coal mining the heterogeneous zone inferred from the tomography measurements was first digitalised and implemented into a 3d geomechanical model a microseismicity modelling approach which combines deterministic stress and failure analysis together with a stochastic fracture slip evaluation was used to simulate the evolution of microseismicity induced by the progressive face advance passing through the heterogeneous zone the heterogeneity was taken into account by varying the material strength and the fracture attributes of the elements within the high strength zone results have shown that both the high rock strength of coal lithotype and low power law scaling exponent of fractures within this zone contribute to the reduction in fitted b values from frequency magnitude distribution of microseismicity and the increase in fitted gaussian distribution parameters to the logarithmic event energy these deviations are believed to result from the combined effects of increased stress drops and slipped fracture sizes when the heterogeneous zone is approached

erratum to variations of sulphur isotope signatures in sulphides from the metamorphosed ming cu au volcanogenic massive sulphide deposit newfoundland appalachians canada the ming deposit is an early ordovician bimodal mafic cu au volcanogenic massive sulphide vms deposit in the newfoundland appalachians that was metamorphosed to upper greenschist lower amphibolite facies conditions and deformed in the silurian and devonian the ming deposit consists of several spatially proximal ore bodies of which the 1806 zone 1807 zone ming south up plunge and down plunge and the lower footwall zone are the focus of this paper the ore bodies have similar stratigraphic sequences the ore bodies can be divided into 1 a silicified horizon that caps the massive sulphides 2 semi massive to massive sulphides and 3 sulphide mineralization in a rhyodacitic footwall sulphide mineralization in a rhyodacitic footwall includes a sulphide stringers immediately below the semi massive to massive sulphides and b chalcopyrite pyrrhotite pyrite stringers distally from semi massive to massive sulphides in the lower footwall zone pyrite chalcopyrite pyrrhotite arsenopyrite and galena were analysed by in situ secondary ion mass spectrometry sims for sulphur isotope compositions the isotopic signatures of pyrite chalcopyrite pyrrhotite and arsenopyrite fall within a limited range of 2 8 to 12 0 for semi massive to massive sulphides and sulphide mineralization in the footwall the silicified horizon capping the semi massive to massive sulphides has higher 34s 5 8 19 6 especially for pyrrhotite mean 17 2 2 2 n 8 the sulphur isotope composition of galena is more heterogeneous especially within semi massive to massive sulphides and sulphide stringers ranging from 0 8 to 17 3 mean 6 1 4 3 n 35 and 7 6 to 17 1 mean 13 7 5 3 n 3 respectively geothermometric calculations give insufficient formation and metamorphism temperatures for neighbouring mineral pairs because sulphides were not in isotopic equilibrium while deposited in early ordovician or re equilibrated during silurian devonian metamorphism respectively therefore original isotopic compositions of sulphides at the ming deposit have been preserved modelling of the source of sulphur shows that 1 reduced seawater sulphate and 2 sulphur leached from igneous wall rock and or derived from magmatic fluids are the main sources of sulphur in the ming deposit the influence of igneous sulphur igneous wall rock magmatic fluids increases with temperature and is an important sulphur source for the semi massive to massive sulphides and footwall mineralization in addition to a contribution from thermochemical sulphate reduction tsr of seawater it is difficult to distinguish between sulphur leached from igneous rocks and magmatic fluid related sulphur and it is possible that both sources contributed to the ores at the ming deposit in addition to igneous sulphur the heavy isotopes of the silicified horizon are consistent with the sulphur in this horizon being derived only from thermochemical sulphate reduction of early ordovician seawater sulphate

scaling relations for seismic events induced by mining the values of seismic moment ands wave corner frequency from 1575 seismic events induced in south african canadian polish and german underground mines were collected to study their scaling relations the values ofp wave corner frequency from 649 events were also available seismic moments of these events range from 5 103 to 2 1015 n m moment magnitude is from 3 6 to 4 1 thes wave corner frequency ranges from 0 7 to 4438 hz and thep wave corner frequency is between 5 and 4010 hz the slope of a regression line between the logarithm ofs andp wave corner frequencies is equal to one and the corner frequencies ofp waves are higher than those ofs waves on the average by about 25 percent in studies of large and moderate earthquakes it has been found that stress drop is approximately independent of the seismic moment which means that seismic moment is inversely proportional to the third power of corner frequency such a behavior was confirmed for most of the data considered here a breakdown in the similarity betwen large and small events seems to occur for the events with moment magnitude below 2 5 the average values of seismic moment referred to the same range of corner frequency however are vastly different in various mining areas

sulfur isotope characteristics of metamorphosed zn cu volcanogenic massive sulfides in the areachap group northern cape province south africa zn and cu rich massive sulfide ores of volcanogenic origin volcanogenic massive sulfide vms deposits occur as stratiform stratabound lenses of variable size hosted by gneisses amphibolites and schists of the areachap group in the northern cape province of south africa the areachap group represents the highly deformed and metamorphosed remnants of a mesoproterozoic volcanic arc that was accreted onto the western margin of the kaapvaal craton during the 1 0 1 2 ga namaquan orogeny sulfur isotope data 34s are presented for 57 sulfide separates and one barite sample from five massive sulfide occurrences in the areachap group although sulfides from each site have distinct sulfur isotope values all 34s values fall within a very limited range 3 0 to 8 5 barite has a 34s value of 18 5 very different from that of associated sulfides at one of the studied sites kantienpan a distinct increase in 34s of sulfides is observed from the massive sulfide lens into the disseminated sulfides associated with a distinct footwall alteration zone sulfide sulfide and sulfide barite mineral pairs which recrystallized together during amphibolite and lower granulite facies metamorphism are not in isotopic equilibrium sulfur isotope characteristics of sulfides and sulfates of the zn cu ores in the areachap group are however very similar to base metal sulfide accumulations associated with modern volcanic arcs and unsedimented mid ocean ridges it is thus concluded that profound recrystallization and textural reconstitution associated with high grade regional metamorphism of the massive sulfide ores of the areachap group did not result in extensive sulfur isotopic homogenization this is similar to observations in other metamorphosed vms deposit districts and confirms that massive sulfide ores remain effectively a closed system for sulfur isotopes for both sulfides and sulfates during metamorphism