interferometric seismic imaging around the active lalor mine in the flin flon greenstone belt canada abstract seismic interferometry which recovers the impulse response of the earth by cross correlation of ambient noise recorded at sets of two receivers has found several applications including the generation of virtual shot gathers for use in seismic reflection processing to evaluate the effectiveness of this passive recording technique in mineral exploration in a hard rock environment 336 receivers recorded 300 h of ambient noise over the volcanogenic massive sulphide deposit of the recently discovered lalor mine in the canadian flin flon greenstone belt a novel time domain beamforming algorithm was developed to search for individual source locations demonstrating that the vast majority of noise originated from the mine and ventilation shafts of the lalor mine the results of the beamforming were utilized in conjunction with frequency wavenumber filtering to remove undesirable mostly monochromatic surface wave noise originating from nearby sources virtual shot gathers were generated along three receiver lines each of which was processed as a separate 2 d reflection line two of the resulting unmigrated reflection profiles are compared against coincident dipmoveout stacked data from a larger coincident 3 d dynamite seismic survey that was also acquired over the lalor mine in 2013 using knowledge of the local geology derived from numerous boreholes coherent events recovered in the passive reflection profiles are inferred to be either spurious arrivals or real reflections some of which can be interpreted in terms of geological contacts indicating the future potential of passive recording surveys in hard rock settings

neotectonic evolution and fault geometry change along a major extensional fault system in the mission and flathead valleys nw montana abstract analysis of 3 5 khz high resolution seismic data from flathead lake combined with results from onshore geologic mapping and literature review from previous studies in the area reveals a significant change in fault geometry and seismic activity along strike of the mission fault system in the mission and flathead valleys of northwestern montana the mission fault system is composed of faults with normal sense of motion and faults with minor oblique slip and strike slip motion it evolves from a single fault strand in the mission valley south of flathead lake into a multiple strand fault system in the flathead lake basin and north of the lake fault activity decreases to the north as suggested by northward decreasing fault scarp heights in the lake basin north of the lake the mission fault system is truncated by oblique strike slip faults and the extensional strain is accommodated by the swan fault another major normal fault north and east of the study area we observed five phases of increased tectonic activity in the lake basin during the last 15 000 years the oldest phase phase b active between 15 000 and 13 000 cal yr bp resulted in fault scarps with up to 14 m of relief along the mission fault and the kalispell finley point fault we calculated average displacement rates as high as 1 mm yr for this oldest phase phases c f represent smaller tectonic events in the lake basin during the last 10 000 cal yr bp offset of seismic reflectors during these younger events is generally at dm scale indicating relatively low average displacement rates

the application of reflection seismology to the investigation of the geometry of near surface units and faults in the blake river group abitibi belt quebec reprocessing of part of a lithoprobe high resolution seismic reflection line across the southern part of the abitibi belt has improved the imaging of shallow reflections and allowed correlation of the data with surface geology enhancement of early reflections was accomplished by focusing on the high frequency content of the data this improved resolution of reflections at two way traveltime as early as 0 3 s and attenuated noise such as shear waves the shallow reflections are interpreted as impedance contrasts at the contact between a metadiabase diorite body and metavolcanics rocks offsets of the reflectors correlate with faults mapped at the surface and indicate a downdropped block which may be of interest for mineral exploration

subsurface mapping in the iberian pyrite belt using seismic reflection profiling and potential field data the iberian pyrite belt ipb hosts world class massive sulphide deposits such as neves corvo in portugal and rio tinto in spain in portugal the palaeozoic volcanic sedimentary complex vsc hosts these ore deposits extending from the gr ndola alcacer region to the spanish border with a nw se to wnw ese trend in the study area between the neves corvo mine region and alcoutim close to the spanish border the vsc outcrops only in a small horst near alcoutim sparse exploration drill hole data indicate that the depth to the top of the vsc varies from several 100 m to about 1 km beneath the mertola formation flysch cover mapping of the vsc to the se of neves corvo mine is an important exploration goal and motivated the acquisition of six 2d seismic reflection profiles with a total length of approximately 82 km in order to map the hidden extension of the vsc the data providing information deeper than 10 km at some locations were integrated in a 3d software environment along with potential field geological and drill hole data to form a 3d structural framework model seismic data show strong reflections that represent several long variscan thrust planes that smoothly dip to the nne outcropping and previously unknown late variscan near vertical faults were also mapped our data strongly suggest that the structural framework of neves corvo extends south eastwards to alcoutim furthermore the vsc top is located at depths that show the existence within the ipb of new areas with good potential to develop exploration projects envisaging the discovery of massive sulphide deposits of the neves corvo type

3d stochastic inversion of gravity data using cokriging and cosimulation a new application has been developed based on geostatistical techniques of cokriging and conditional simulation for the 3d inversion of gravity data including geologic constraints the necessary gravity density and gravity density covariance matrices are estimated using the observed gravity data then the densities are cokriged or simulated using the gravity data as the secondary variable the model allows noise to be included in the observations the method is applied to two synthetic models a short dipping dike and a stochastic distribution of densities then some geologic information is added as constraints to the cokriging system the results show the ability of the method to integrate complex a priori information the survey data of the matagami mining camp are considered as a case study the inversion method based on cokriging is applied to the residual anomaly to map the geology through the estimation of the density distribution in this region the results of the inversion and simulation methods are in good agreement with the surface geology of the survey region

microearthquake activity in the dead sea region summary small earthquakes in the dead sea depression part of the jordan valley dead sea rift were recorded and analysed with 117 identified events of 0 5 ml 4 2 the microseismicity recorded by a local portable network during a period of about 20 months shows a normal rate of seismicity for the region with b values around 0 8 the recorded seismicity is mainly confined to the basin and its boundaries in the southern part of the dead sea basin we found a tendency to clustering which is clearly demonstrated in very similar seismograms of several events recorded at the same station two clusters on the eastern fault are separated by an area with no seismicity for at least 5 yr relative location of events in one of the clusters exhibits a clear north south lineament two active north south left lateral strike slip faults along the east and west boundaries of the southern section of the dead sea basin are distinguished and confirmed by using composite focal mechanism solutions in four out of more than 60 events we found normal faulting where one has a ml 4 1 for 34 events with 1 6 ml 4 2 we found seismic moment estimates m0 of 1 2 1019 m0 2 3 times 1022 dyne cm and brune stress drop estimates s between 0 6 and 92 bars for earthquakes of m0 smaller than about 5 times 1021 dyne cm we found only small variations in corner frequency f0 resulting in decreasing s with decreasing m0 this breakdown of the scaling relation for small earthquakes suggests an fmax slightly lower than 10 hz for the dead sea region the fmax is confirmed by available accelerometer data

3 d inversion of gravity and magnetic data with depth resolution magnetization and density models with depth resolution are obtained by solving an inverse problem based on a 3 d set of potential field data such a data set is built from information on vertical and horizontal variations of the magnetic or gravity field the a priori information consists of delimiting a source region and subdividing it in a set of blocks in this case the information related to a set of field data along the vertical direction is not generally redundant and is decisive in giving a depth resolution to the gravity and magnetic methods because of this depth resolution which derives solely from the potential field data an unconstrained and joint inversion of a multiobservation level data set is shown to provide surprising results for error free synthetic data on the contrary a single observation level data inversion produces an incorrect and too shallow model hence a good depth resolution is likely to occur for the gravity and magnetic methods when based on the information along the vertical direction this is also evidenced by an analysis of the kernel function versus the field altitude level and by a singular value analysis of the inversion operators for both the single and multilevel cases errors connected to numerical upward continuation do not affect the quality of the solution provided that the data set extent is larger than that of the anomaly field application of the method to a 3 d magnetic data set relative to vesuvius indicates that the method may significantly improve interpretation of potential fields

a review of high resolution seismic profiling across the sudbury selbaie noranda and matagami mining camps lithoprobe high resolution seismic surveys have provided the first systematic images of the deep stratigraphy in four major canadian mining camps noranda matagami sudbury and selbaie systematic compressional wave velocity and density measurements in deep boreholes have established that lithological contacts were the main impedance contrast imaged although reflections from faults and deformation zones have also been observed the strongest reflections are attributed to mafic intrusions and some sulphides and oxides integrating seismic physical rock property measurements and geological data has resulted in the revision of several geological models with direct impact on local strategies for deep mineral exploration mining companies have shown an interest in seismic reflection methods and this has led to several follow up studies the application of seismic methods to the direct detection of massive sulphides based on physical rock property measurements has been studied through two dimensional an

shallow high resolution seismic imaging at the ansil mining camp in the abitibi greenstone belt volcanic rocks in and around the ansil mining camp host a large number of massive sulfide mineral deposits a high resolution seismic reflection profile was shot across the camp with the objective of mapping the contacts between the different volcanic units at which most of the ore bodies have been found numerous exploration boreholes define the geology to a depth of 1600 m and allow a precise comparison with the recorded reflections geophysical logs obtained in one deep borehole suggest that reflection coefficients between the andesite rhyolite units of the volcanic stratigraphy are around 0 05 but few corresponding reflections can be identified in the seismic data those reflections in the surface seismic profile that can be correlated with the subsurface geology originate from diorite sills at which reflection coefficients are between 0 05 and 0 11 we suggest that reflections are observed from the diorite sills because the sills were intruded as sheets some along fault planes resulting in inte

archean continental assembly in the southeastern superior province of canada between 1988 and 1993 seismic reflection and refraction surveys were acquired across the medium to high grade opatica plutonic gneiss belt the low grade abitibi greenstone belt and the pontiac metasedimentary belt all of which form part of the late archean superior province shallowly north dipping reflections define a structural style consistent with the northward underthrusting and accretion over about 30 ma of various exotic terranes against a backstop provided by the opatica belt this rapid southward growth of the archean protocraton was driven by at least one north dipping subduction zone as revealed by north dipping reflections that extend to 65 km depth in the upper mantle below the opatica belt in contrast to the mainly orthogneissic opatica and pontiac belts the midcrust of the abitibi belt comprises metasedimentary and igneous rocks plus imbricated units of unknown affinity relict midcrustal accretionary complexes of substantial size whieh are indicative of primary suture zones are interpreted near the northern and southern limits of the abitibi belt an interpreted basal decollement and significantly older ages in the north suggest that the upper crustal greenstone rocks are allochthonous evidence of large scale extension appears to be confined to the southern volcanic zone of the abitibi which developed into a half graben as the original suture zone was reactivated in extension unusually high seismic p wave velocities 7 5 8 2 kms 1 are present in the lower 8 km of the abitibi crust and they correlate well with a downward reduction in seismic reflectivity attributable to late modification of the deepest part of the crust crustal xenolith studies suggest that this process may be linked to early proterozoic magmatism

stress field fluctuations along the dead sea rift since the middle miocene the dead sea transform dst is the suture between the african and the arabian plates both of which subduct northward under the eurasian plate the collision of these plates with eurasia and their relative motion are the source for their internal deformation especially in the vicinity of the dead sea transform geological observations indicate that two distinct paleostrain regimes operated adjacent to the dead sea rift and in the sinai israel subplate 1 wnw shortening less than 10 and nne extension beginning in the turonian is associated with the development of the syrian arc fold belt and attributed to the syrian arc stress field sas and 2 middle miocene to recent nnw shortening and ene extension associated with the 105 km sinistral displacement along the dead sea transform and the opening of the red sea is attributed to the dead sea stress field dss it was originally suggested that the sas terminated during the middle miocene with initiation of the dss however trend and age analysis of many structures shows that formation of sas compatible structures continued after the middle miocene up to the recent in some middle miocene and younger rocks structures such as faults dikes volcanic lineaments and tectonic stylolites compatible with both stress fields were reported in a few locations structures compatible with both stress fields crosscut each other it is suggested that the movements which resulted in the development of the syrian arc and other sas compatible structures are continuing to the recent and that dss movements are superimposed upon them the overlapping of sas and dss structures adjacent to the dst results from spatial and temporal fluctuations in the overall stress state we propose that such variations could be caused by the superposition of large earthquake stress drops associated with movements along the dst on a steady background plate scale stress regime associated with the sas thus dss compatible structures should form in preseismic activity periods when dst related elastic strain is high on the other hand the sas compatible structures should form during interseismic activity times subsequent to large local stress release along the dst

the lithoprobe abitibi grenville transect two billion years of crust formation and recycling in the precambrian shield of canada we summarize the results of lithoprobe studies in the neoarchean southeastern superior province and the mesoproterozoic grenville province in the southeastern precambrian shield of canada through two composite cross sections based on seismic reflection data which define dramatically different styles of crust formation and tectonic accretion in the neoarchean and mesoproterozoic in the neoarchean the structures at the surface are steep with discontinuous and flatter structures at depth much of the crust appears to be juvenile and the predominant process of crustal growth is inferred to have been subduction accretion of primitive crust in a prograding arc system in the mesoproterozoic surface structures are shallow and the seismic character of the crust is continuous over the entire cross section archean parautochthonous rocks and reworked archean crust comprise a very significant proportion of the preserved crust in the mesoproterozoic and provided the backstop to the grenvillian orogeny result

seismic imaging of massive sulfide deposits part i rock properties laboratory measurements of the density rho and compressional wave velocity v p of massive sulfides and host rocks at elevated pressures show that ores occupy a v p rho field which is distinct from that of common silicate rocks and governed by simple mixing rules between the properties of host rocks and pure sulfide minerals the velocities of the most common sulfides are extremely variable ranging from 3 7 km s for galena through 4 7 km s for pyrrhotite 5 6 km s for sphalerite and chalcopyrite to 8 0 km s for pyrite but their densities are always high 7 6 4 6 4 1 4 2 and 5 0 g cc respectively causing ores of even intermediate grade to have high acoustic impedances this suggests that large massive sulfide bodies should make strong to spectacular seismic reflectors depending on their grade mineralogy size and setting in principle it should thus be possible to use high resolution seismic reflection techniques for base metal exploration and delineation

seismic properties of rocks from the flin flon volcanogenic massive sulfide camp seismic properties of rocks from the flin flon volcanogenic massive sulfide vms camp were determined to evaluate the suitability of seismic reflection imaging for mineral exploration and have subsequently aided interpretation of 2 d and 3 d seismic data acquired in the camp seismic impedances of flin flon rocks were determined from laboratory measurements of compressional and shear wave velocity vp vs and density for 61 core samples complementary in situ measurements of vp and density provided by sonic and density logs acquired in nine drill holes allow calculation of synthetic seismic responses sandstones of the missi group show low reflectivity with sparse strong internal reflections resulting from intrusions or thrust interleaved mafic rocks basaltic sequences are generally moderately reflective due to variability in their composition alteration and the effects of foliation and shearing the mine horizon which hosts the known orebodies should be reflective based on the impedance contrast of constituent rhyolite and mafic igneous rocks and the presence of sulfide mineralization however reflectivity of this horizon should be variable due to the significant alteration of the footwall basalt ore zones solid sulfide should range from moderately to very highly reflective depending on their sulfide compositions vertical seismic profiles demonstrate that contacts between major stratigraphic units e g missi group contact with hidden formation volcanic rocks or felsic igneous rocks within the basalts should produce significant reflections whereas some of the internal reflectivity predicted for the basaltic sequences will not be as prevalent

imaging of fracture zones in the finnsjon area central sweden using the seismic reflection method in 1987 the swedish nuclear fuel and waste management co skb funded the shooting of a 1 7 km long high resolution seismic profile over the finnsjon study site using a 60 channel acquisition system with a shotpoint and geophone spacing of 10 m the site is located about 140 km north of stockholm and the host rocks are mainly granodioritic the main objective of the profile was to image a known fracture zone with high hydraulic conductivity dipping gently to the west at depths of 100 to 400 m the initial processing of the data failed to image this fracture zone however a steeply dipping reflector was imaged indicating the field data were of adequate quality and that the problem lay in the processing these data have now been reprocessed and a clear image of the gently dipping zone has been obtained in addition several other reflectors were imaged in the reprocessed section both gently and steeply dipping ones correlations with borehole data indicate that the origin of these reflections are also fracture zones the improvement over the previous processing is caused mainly by 1 refraction statics 2 choice of frequency band 3 f k filtering and 4 velocity analyses in addition to reprocessing the data some further analyses were done including simulation of acquisition using only the near offset channels channels 1 30 and the far offset channels channels 31 60 and determining the damping factor q in the upper few hundred meters based upon the amplitude decay of the first arrivals the data acquisition simulation shows the far offset contribution to be significant even for shallow reflectors in this area contrary to what may be expected a q value of 10 determined from observed amplitude decay rates agrees well with theoretical ones assuming plane wave propagation in an attenuating medium

seismic imaging of the enigmatic sudbury structure the sudbury structure on the southern margin of the superior craton was created by a catastrophic explosion in 1 85 ga and hosts one of the world s largest ni cu reserves as a unique terrestrial geological feature its genesis has been vigorously debated for more than a century in an effort to optimize the image from seismic reflection data acquired across the center of the sudbury structure we have developed a straight line common midpoint binning strategy and employed cross dip corrections these pseudo three dimensional seismic processing techniques coupled with standard processing methods have overcome limitations associated with conventional two dimensional seismic data processing and have substantially enhanced the seismic image warranting a more detailed and reliable structural interpretation the new image has revealed a major previously unrecognized zone of imbricated nw thrusts interpretation of these thrusts provides critical timing constraints relating the sudbury tectonic deformation to deposition of the sudbury basin sediments the onwatin argillites are penetrated by blind thrust faults whereas the overlying chelmsford turbidites are undeformed and most likely postdate the thrusting thus the uniform paleocurrent trends observed in the chelmsford reflect subsequent deformation history and may be dismissed as evidence against an impact origin based on our interpretation of the seismic image the original volume of the sudbury igneous complex likely an impact melt sheet is 1 104 km3 supporting the claim that the sudbury structure represents the eroded and tectonized remanent of one of the largest known impact structure 200 km on earth

illite and hydrocarbon exploration illite is a general term for the dioctahedral mica like clay mineral common in sedimentary rocks especially shales illite is of interest to the petroleum industry because it can provide a k ar isotope date that constrains the timing of basin heating events it is critical to establish that hydrocarbon formation and migration occurred after the formation of the trap anticline etc that is to hold the oil illite also may precipitate in the pores of sandstone reservoirs impeding fluid flow illite in shales is a mixture of detrital mica and its weathering products with diagenetic illite formed by reaction with pore fluids during burial k ar ages are apparent ages of mixtures of detrital and diagenetic end members and what we need are the ages of the end members themselves this paper describes a methodology based on mineralogy and crystallography for interpreting the k ar ages from illites in sedimentary rocks and for estimating the ages of the end members

interpretation of the reflections in the siljan ring area based on results from the gravberg 1 borehole abstract during 1985 about 80 km of surface multichannel seismic reflection data were collected across the meteorite impact in the siljan ring area in central sweden the area consists mainly of granitic and gneissic rock ranging in age from 1400 to 2000 million years with remnants of palaeozoic sedimentary rocks preserved by downfaulting after a meteorite impact at 360 ma thereby forming a circular ring about 40 km in diameter dolerite intrusions ranging in age from 850 to 1700 million years are also present the seismic data revealed several high amplitude laterally continuous sub horizontal reflections in the northern part of the structure the high amplitude reflections and a possible intermediate low velocity zone were contributing factors in choosing the site for the gravberg 1 deep earth gas test well drilling and vertical seismic profiling vsp found that the reflectors were associated with dolerite sills which had intruded into the granite and which range in thickness from a few metres up to 60 m and with a pre impact area extent of at least 800 km 2 studies of amplitude and frequency versus offset afvo show the observations are compatible with a model of simple granite dolerite granite layering

internal structure of the dead sea leaky transform rift in relation to plate kinematics abstract the structures along the dead sea transform rift are related to the motions of the sinai and arabia plates which border it and to the irregularities of their boundaries the total slip was 105 km left lateral but the present structures were formed mainly during the last 40 km of slip which probably occurred in the plio pleistocene along the southern half of the transform the strike slip motion takes place on en echelon faults this produces rhomb shaped grabens or pull aparts which are sometimes composite and in which there is local crustal separation thus much of the transform is leaky these structures occur in a morpho tectonic rift valley delimited by normal faults which express a small component of transverse extension along a few segments the shape of the transform is such that lateral motion produces local transverse compression the geometric relations of the structures along the transform define an eulerian pole of relative plate motions at 32 8 n 22 6 e 0 5 the older motion was somewhat different and is described by a pole located about 5 west of the above then the component of transverse extension and crustal separation was much smaller than now while local transverse compression was more important the northern half of the dead sea transform has an irregular shape and the bordering plates did not remain rigid as lateral motion continued here transverse compression is often important

origin of illite in the lower paleozoic of the illinois basin evidence for brine migrations in the lower paleozoic of the illinois basin three illite polytypes are found 2m 1 of detrital origin and 1m d and 1m of diagenetic origin illite polytype quantification of detrital 2m 1 illite and diagenetic 1m d and 1m illite combined with k ar age dating allows extrapolation to apparent detrital and diagenetic illite ages kinetic modeling of smectite illitization combined with the calculated age of illitization can evaluate different origins of illite the diagenetic illite in the lower paleozoic of the illinois basin is interpreted not to have formed solely by burial diagenesis but mainly during multiple brine events the upper ordovician maquoketa group contains diagenetic illite dominantly 1m d with minor 1m with an extrapolated age of 360 m y 356 377 m y and formed from smectite at temperatures of 50 100 c this age falls within the span of dates for illite smectite i s in k bentonites from the upper mississippi valley and is interpreted to be a combined result of illitization by burial diagenesis and either a hydrothermal brine from the southern and deeper part of the basin or a k rich brine from the michigan basin upper mississippi valley area or forest city basin in ordovician and cambrian shale partings and sandstone older than the maquoketa group the diagenetic illite 1m d in shale and 1m in sandstone has an age of 300 m y and formed at temperatures 140 c this late paleozoic age falls within the range of illites from sandstone in the upper mississippi valley and k bentonites of the appalachian basin it coincides with the alleghany orogeny and is interpreted as having formed by gravity driven flow from the uplifted alleghanian ouachita orogenic belt that drove hot 140 c fluids through the illinois basin

seismic reflection and borehole geophysical investigations in the matagami mining camp a high frequency vibroseis seismic survey was conducted by lithoprobe across a well known section of the matagami mining camp to assess the usefulness of seismic methods in lithological mapping the data have been reprocessed to enhance shallow reflections critical processing steps for the preservation of the shallow features include refraction static corrections cross dip corrections and first break mutes the seismic data were calibrated using geophysical logs from two boreholes adjacent to the profile physical rock property measurements suggest that strong reflectivity within the volcanic sequence occurs at rhyolite gabbro contacts the lower wabassee group a sequence of gabbros and basalts with interlayered rhyolite horizons has been identified as a seismic marker this reflective package overlays the horizon where most sulphide deposits are known to be located in the matagami mining camp seismic reflection methods can be used to map the deep volcanic stratigraphy and structures

intraplate deformation by block rotation and mesostructures along the dead sea transform northern israel combined analysis of mega and meso structures yield the strain inferred stress and tectonic history of the margin of the sinai sub plate in northern israel along the dead sea transform three major stress regimes were developed and have affected the region since the middle miocene one is regional and controlled the left lateral shear along the dead sea transform this one has been active since post early miocene is characterized by 1 trending c 345 and deformed the plate margin by horizontal shear and contemporaneous block rotation this style of deformation is similar to simple shear the second one was local and may be subdivided into distinct stress and strain domains it was characterized by 1 trending e w and 3 trending n s which produced a conjugate set of strike slip faults the region underwent n s elongation by horizontal shear and block rotation similar to the pure shear mechanism this stress regime was active in late miocene to early pliocene time the third and youngest stress regime is extentional with 1 vertical and 3 oriented n s this one has been active since post middle pliocene time producing e w normal faults and minor n s elongation the second and third stress regimes show local distribution and developed as a consequence of the bent geometry of the transform vis a vis the plate slip vector finite element and photoelastic models predict the development of local stress fields and elongation of the plate margin parallel and subparallel to the transform plate boundary the strain of the plate margin in northern israel and southern lebanon indicate remarkable elongation parallel to the dead sea transform by a factor of 1 5 2 1 since the miocene this process of intraplate deformation and the consequent strain is unique to the parts of the plate margin which are adjacent to the bent segment of the transform

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

seismicity of the eastern mediterranean region perspective from the sinai subplate we conducted a comprehensive study of the seismicity of the eastern mediterranean and examined its relation to the regional plate tectonics based on various published catalogs we have constructed a new list of ml 4 earthquakes which were recorded during the years 1900 1991 and represents most of the seismic moment released in the area over this period b values are 1 02 1 0 and 1 07 for the whole sinai subplate the dead sea transform and the cypriot arc respectively seismic efficiency of the dead sea transform is very low about 7 stressing the role of aseismic deformation in that plate border most of the major and moderate events ml 5 occur in belts associated with the geologically documented borders of the sinai subplate the cypriot convergent arc in the north the dead sea transform in the east and the rift of suez in the southwest the latter like the gulf of eilat aqaba was considered aseismic during the first half of the century the northwestern border however could not be delineated low level activity appears within the subplate especially north of latitude 32 n reflecting the breakdown of this part of sinai as it approaches the cypriot convergence zone though most of the seismic moments tend to concentrate along the subplate borders some moderate activity spreads out in wide belts which reflect the complexity of deformation accompanying motion along the subplate borders

bullwinkle a unique 3 d experiment in the spring of 1988 shell offshore inc acquired two orthogonal three dimensional 3 d surveys at prospect bullwinkle located in the green canyon area of the gulf of mexico to aid the development program which began later that year two surveys were acquired because of the complexity of the salt structures in the vicinity of the prospect the independent acquisition and processing of two surveys shot perpendicular to each other provided a unique data set for checking the quality and accuracy of standard 3 d techniques the high development cost of this deep water 410 m turbidite field supported the acquisition of two 3 d data sets to provide a valuable redundancy for stratigraphic interpretation this large scale 3 d experiment has been analyzed in terms of interpretive impact detailed comparisons of the seismic images away from the salt complex show good agreement between the two surveys and verify the relative accuracy and repeatability of the acquisition processing and interpretation techniq

structure and paleostresses in the gilboa region western margins of the central dead sea rift abstract the relationships between tectonic paleostresses and major fault systems are analyzed for the gilboa region the gilboa is a folded block on the western margins of the dead sea transform which has been deformed and uplifted at least since the miocene the tectonic paleostresses in the gilboa were determined by inversion of slip striations along small faults measured in the field and from the trends of basaltic dikes one state of stress dominated the gilboa region since the miocene the principal axes of the calculated stress tensor are 1 at 0 122 2 vertical and 3 at 0 032 this stress fits well with the trends of the syrian arc folds in the gilboa and its is compatible with the observed normal slip along the gilboa fault however this stress is incompatible with the either left lateral slip or normal faulting along the dead sea system possible mechanisms to resolve this incompatibility are discussed

diagenesis of the purington shale in the illinois basin and implications for the diagenetic state of sedimentary rocks of shallow paleozoic basins abstract the clay minerals micas and feldspars of the pennsylvanian age purington shale have been more diagenetically active than generally recognized they have undergone diagenetic changes comparable to those of cenozoic and mesozoic sedimentary rocks buried three to four times as deeply and heated to approximately twice the temperature the purington shale on the western shelf of the illinois basin has experienced maximum burial of 1 0 km and was never heated to more than 60 c except for a very brief time at about 80 c the illite smectite i s of the purington shale has 90 illite the chemical compositions of the feldspar assemblage in the 0 09 0 063 mm fraction differ from most modern detrital suites of feldspars but are similar to diagenetic sequences described by others from much greater burial depths and are extensively but not completely albitized the simplest interpretation of the apparently advanced stage of diagenesis is that the diagenetic processes have been operating at less press

the tectonic evolution of the abitibi greenstone belt of canada based on structural geochemical sedimentological and geochronological studies we have formulated a model for the evolution of the late archaean abitibi greenstone belt of the superior province of canada the southern volcanic zone svz of the belt is dominated by komatiitic to tholeiitic volcanic plateaux and large bimodal mafic felsic volcanic centres these volcanic rocks were erupted between approximately 2710 ma and 2700 ma in a series of rift basins formed as a result of wrench fault tectonics the svz superimposes an older volcanic terrane which is characterized in the northern volcanic zone nvz of the abitibi belt and is approximately 2720 ma or older the nvz comprises basaltic to andesitic and dacitic subaqueous massive volcanics which are cored by comagmatic sill complexes and layered mafic anorthositic plutonic complexes these volcanics are overlain by felsic pyroclastic rocks that were comagmatic with the emplacement of tonalitic plutons at 2717 2 ma the tectonic model envisages the svz to have formed in a series of rift basins which dissected an earlier formed volcanic arc the nvz analogous rift environments have been postulated for the hokuroko basin of japan the taupo volcanic zone of new zealand and the sumatra and nicaragua arcs the difference between rift related submergent volcanism in the svz and emergent volcanism in the nvz resulted in the contrasting metallogenic styles the former being characterized by syngenetic massive sulphide deposits whilst the latter was dominated by epigenetic porphyry type cu au deposits

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

identification of wrench faults using subsurface structural data criteria and pitfalls 1 many structures imaged with reflection seismic can resemble a wrench fault system because of the great structural diversity of strike slip faults and the wide range of contractional and extensional features associated with these faults because of these resemblances numerous faults are misidentified as wrench faults by workers using subsurface structural data credible identification requires combinations of profile and map criteria 1 narrow long straight throughgoing solitary master fault or zone of deformation 2 steep to moderate dip of the master fault at depth 3 offset of the top of basement 4 changes in relative upthrown side separation sense and or fault dip direction at depth or along the strike of the master fault 5 narrow fault slices within the master fault zone that steepen and join at depth negative and positive flower structures 6 different separation sense and orientation of relative upthrown side at these fault slices and 7 coeval en echelon flanking structures the identification should be confirmed with other criteria that refute alternative interpretations the main pitfalls to a reliable identification are not considering alternative structural styles and the misinterpretation of features or patterns that superficially resemble wrench systems the profile geometries of basement involved reverse or normal faults particularly those with structural inversion can resemble the single strand of convergent or divergent wrench faults profile geometries of flower structures can be mimicked by narrow contractional horsts or narrow extensional grabens complexly faulted anticlines or synclines splay faults fault zones intruded by salt or shale and overprinted structures pitfalls in interpreting map relationships are possible when structural patterns combine several tectonic influences are controlled by rock anisotropy or include elements hat are not coeval and if the patterns characteristic of other styles are misinterpreted many erroneous identifications of wrench faults can be eliminated by demonstrating that the investigated fault or feature lacks a straight trace lateral length or throughgoing continuity

a silurian soft bodied biota a new silurian llandoverian biota from wisconsin with a significant soft bodied and lightly sclerotized component is dominated by arthropods and worms the fauna includes the earliest well preserved xiphosure a possible marine uniramian three new arthropods of uncertain affinity and possibly the first paleozoic leech this may be only the second locality to yield a conodont animal lack of a normal shelly fauna suggests an unusual environment the discovery adds significantly to the few such exceptionally preserved faunas known from lower paleozoic rocks

evidence for local shifting of the main fault and changes in the structural setting kinarot basin dead sea transform two new high resolution seismic reflection profiles from the kinarot valley dead sea rift analyzed with older conventional oil exploration profiles throw light on the quaternary evolution of the african arabian transform type plate boundary in the area the present en echelon main faults of the dead sea transform are observed in the seismic data as wide zones of deformation rather than as distinct fault planes a similar zone of deformation is observed in the center of the kinarot basin and may be associated with an extinct trace of the main fault the zemah structure previously mapped and drilled is shown by the new data to be an inactive anticline compression within the basin is suggested as being the result of motion along the now inactive main fault observed in the center of the basin compression and shortening started some 2 m y ago and ended late in the quaternary as a result of changes in the geometry of the transform at present the kinarot basin is subsiding

a vibroseis reflection seismic survey at the buchans mine in central newfoundland we present results from the first major vibroseis seismic reflection survey at a mine site in north america it is demonstrated that conventional high stack fold reflection seismic techniques can image fault structures associated with volcanogenic massive sulfide bodies despite the fact that these structures are locally steeply dipping and produce records with low signal to noise ratios the new lines were recorded at the locations of two earlier experimental explosive surveys that failed to image many strong reflectors the principal reasons for the success of the vibroseis experiment were the proper choice of sweep frequencies for maximum signal to noise ratio the use of high stack fold and the careful analysis of velocities and statics during processing a comparison of the new seismic sections with borehole and other geophysical data indicates that the origin of reflections at buchans can be attributed to various mechanisms including contrasts in lithologies and rock competence and intrusion of diabase sills into pre existing fault zones the best reflections emanate from shallow dipping brittle ductile thrust fault zones characterized by fault gouge within broader fractured zones the two seismic lines presented have proven to be a useful and cost effective supplement to existing borehole and geophysical data and have provided enough new information on the nature of thrust faulting at the mine to significantly influence current exploration plans

characterization of the waukesha illite a mixed polytype illite in the clay mineral society repository the waukesha illite is an excellent example of the illites found in argillaceous rocks typical for paleozoic shales that have undergone significant burial diagenesis during their geologic history it consists of a mixture of detrital 2 m 1 interpreted to be a residuum of karstification within silurian carbonates and diagenetic 1 m and 1 m d illite the chemistry and the age of the illite polytypes are different extrapolating to 100 the 1 m and 1 m d polytypes have an apparent diagenetic age between 295 and 325 ma the chemistry of the 1 m polytype could not be determined because of its low abundance the approximate chemical composition of the 1 m d polytype is 0 67 k 3 6 si and 1 9 al per half unit cell the 2 m 1 polytype has an apparent detrital age between 440 and 520 ma and an approximate chemical composition per half unit cell of 0 78 k 3 4 si and 2 1 al all within our margin of error x ray diffraction xrd results of both random powder and oriented preparations both indicate that the waukesha illite consists of a mixture of illites the xrd patterns of the random powder preparation indicate it is a physical mixture of three different illite polytypes this result was confirmed using 3 different methods 1 by measuring illite polytype specific reflections 2 by mixing illite polytype reference samples and 3 by mixing wildfire calculated xrd patterns decomposition of the illite 001 xrd peak from oriented preparations also indicates mixtures of illites however the proportions of the three illitic components derived from the oriented 001 peak decomposition differ from those results derived from the analysis of the random powder data therefore the shape of the 001 reflection of the waukesha illite cannot be explained by mixing the three different illite polytypes

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

episodic mineralization of hydrothermal illite in the soultz sous forets granite upper rhine graben france episodic and localized illite mineralization is documented in the hydrothermally altered soultz sous forets granite upper rhine graben france separated grain size fractions of altered granite and argillite vein samples contain mixtures of 2m1 and 1m trans vacant illite varieties the platy pseudohexagonal 2m1 illite phases dominate the vein fillings whereas the 1m illite occurs largely as a fibrous pore filling variety which is particularly abundant in the granite matrix multiple phases of fluid injections into the granite body have resulted in different illite assemblages each sample containing a mixture of polytype generations formed during different crystal growth events on the basis of mineralogical and k ar isotopic constraints the ages of these vein mineralizing events are determined by plotting the k ar values of the various grain size fractions against polytype abundance and the fitted volume weighted crystallite thickness distributions the results suggest a permian age for the formation of the studied argillite veins characterized by successive injections of hydrothermal fluids secondary episodes of illite crystallization occurred during jurassic and cretaceous or even younger times in both the veins and the granite matrix there are indications that the polytype structure and composition of illite were strongly influenced by variations in fluid chemistry and the degree of fluid rock interaction as the granite was progressively sealed during post variscan episodic hydrothermal activity

seismic reflection across a continental transform an example from a convergent segment of the dead sea rift three seismic reflection lines in the dead sea rift in northern israel cross the transform plate boundary between arabia and the sinai block of the african plate the arabian plate edge consists of the meshoshim tilted block which we suggest to be partly a result of prerift activity in the sinai block the elevated rosh pinna saddle is faulted over the meshoshim block with a vertical separation of 2 5 3 km much of this separation is due to young reverse faulting which is related to the oblique plate boundary in this area the main fault zone transfers the motion from the western margin of the kinneret zemah graben to the eastern margin of the hula graben immediately north of lake kinneret the main fault is a 1 to 2 km wide zone of extensive deformation and a discrete main fault trace is hard to define further to the north the deformation is less extensive and is concentrated in a narrow fault zone deformation across the plate boundary is asymmetrical and while the meshoshim block is quite coherent the rosh pinna saddle is a highly faulted and deformed positive flower structure

slip rate and locking depth from gps profiles across the southern dead sea transform 1 the dead sea transform is a major strike slip fault bounding the arabia plate and the sinai subplate on the basis of two gps campaign measurements 6 years apart at 17 sites distributed in israel and jordan complemented by israeli permanent stations we compute the present day deformation across the southern segment of the dead sea transform the wadi araba fault elastic locked fault modeling of fault parallel velocities provides a slip rate of 4 9 1 4 mm a and a best fit locking depth of 12 km this slip rate is slightly higher than previous results based only on israeli permanent gps stations data which are located west of the fault it is in good agreement with results based on offset geomorphologic and geologic features that average longer periods of time 10 ka to 1 ma projection in itrf2000 reference frame allows using our data combined with results published earlier to further study the kinematics between arabia nubia and sinai systematic combination of euler poles available in the literature in addition to our new set of data shows that a wide range of arabia sinai pole positions and angular velocities predict reasonable slip rate on the dead sea fault we highlight uncertainties of calculating such poles due to the small size of the blocks and their slow relative motion along a short and almost straight strand of the transform fault which lead to a large trade off between pole location and angular velocity

enhancing base metal exploration with seismic imaging commencing in 1988 and continuing for 5 years lithoprobe acquired a series of high resolution seismic experiments within and near base metal mining camps in canada including the abitibi subprovince of quebec and ontario the world class sudbury ni cu mining district the buchans mine in newfoundland and the thompson ni belt in manitoba this work undertaken in close cooperation with the geological survey of canada and major canadian mining companies stimulated an intensive and broadened series of followup studies with the common objective of assessing potential applications of multichannel seismic mcs imaging for deep mineral exploration and mine development this research was motivated by a widely recognized disparity between the depths from which ores can be profitably mined up to 2 km or more and the resolving depths typically 500 m of commonly used geophysical methods for mineral exploration initial rock property studies established that the expected contrast in acoustic impedance between

tectonic analysis of the dead sea rift region since the late cretaceous based on mesostructures we have measured the orientations of small faults slickensides tectonic stylolites vein with secondary mineralization small folds and dikes in israel and sinai these structures are indicators of paleo stress or strain and provide the pattern of tectonic deformation data were collected at 130 stations most with tens of separate measurements most stations showed consistent deformation stations were located on exposures ranging from precambrian crystalline rocks to pleistocene sediments we have defined two tectonic stress fields each relatively uniform in both time and space one stress field with dominating maximum horizontal compression trending w to wnw in the late cretaceous to eocene rocks in the folds and plateaus west of the dead sea rift the second field with dominating horizontal extension trending e to ene in all rocks inside the rift and proximal thereto the first stress field is called the syrian arc stress and the second is called the dead sea stress a change in style of tectonic deformation which corresponds to the two stress fields is manifested also in the major structures in israel the late cretaceous to neogene deformation is characterized by long wavelength folds and monoclines whereas the neogene to recent deformation is characterized by normal and strike slip faults and volcanic activity

almost a sharp cut a case study of the cross point between a continental transform and a rift based on 3d gravity modeling abstract transform faults displace older structures crossing their paths marking a visible shift between the two sliding plates the fate of these pre transform structures within the damage zone is less understood and so is the dynamics of plate boundaries and their changes through time to what extent are they preserved and what structural heritage do they dictate the current study focuses on a crossing region between the oligo miocene nw trending irbid rift and the n trending miocene to recent dead sea transform dst the structural heritage aspect is examined through 3d forward modeling of gravity data across the kinneret kinarot beit she an kkb basin complex of the dst the model includes pre senonian to recent formations highlighting key volcanic and evaporitic units by modeling the depth thickness and 3d density distribution of each lithological unit the study constructs the volumetric geometry of the sub basins and suggests central stages in its geological development the southern beit she an basin began as part of the irbid rift and was later hijacked by the younger dst at the transform rift cross region the transform displacement initiated en echelon mini basins from the beit she an basin northwards to form the proto kinarot and kinneret sea of galilee basins volcanic phases record the deformation leaving a reliable time frame for the subsidence mode faulting and the role of salt tectonics during the late miocene the lateral displacement formed a trishear structure that evolved by the plio pleistocene into the kinneret kinarot beit she an complex bounded by longitudinal faults stemming from a single deep rooted fault

the economic significance of the bell river complex abitibi subprovince quebec the exposed part of the bell river complex on the northern edge of the abitibi subprovince represents the upper portion of a layered complex with a massive gabbroic main zone being overlain by a magnetite rich gabbroic anorthositic layered zone and a granophyre the cumulate rocks display cryptic variation in mineral and whole rock compositions towards a more evolved signature with stratigraphic height there is a decrease in an content of plagioclase from an73 et an51 and in mg of augite from mg 75 to mg 56 an increase in la yb ratio of whole rocks from 0 5 to 2 9 and a decrease in cr from 770 to 5 ppm and ni from 315 to 45 ppm contents of whole rocks concentrations of platinum group elements pge are mostly below detection limit compositional comparison with the south african bushveld complex shows that the lowest exposed levels of the complex are equivalent to the critical main zone boundary that is in the immediate hanging wall of the pge reefs based on recent geophysical studies showing that the bell river complex is approximately 5 km thick we consider the presence of a hidden ultramafic zone a distinct possibility and propose a site for an exploration drilling programme a comparison of compositional data from the bell river complex and associated basalts and rhyolites of the watson lake and wabassee groups suggests that the three suites are cogenetic based on the fact that the numerous important volcanogenic massive sulphide vms deposits in the region are located around the intrusion and the similar age of the intrusion and the volcanic rocks we support earlier workers in suggesting that the intrusion and the vms deposits are genetically linked that is that the bell river complex provided the heat source that drove the hydrothermal fluids responsible for forming the vms deposits la partie expose du complexe de be11 river sur la bordure septentrionale de la sous province de l abitibi represente la portion superieure d un complexe stratifie incluant une zone principale formee d une masse gabbroique recouverte par une zone stratifiee gabbroique anorthositique riche en magnetite et une unite de granophyre les compositions obtenues sur roches totales et sur mineraux des lithologies b cumulats presentent des variations relativement subtiles neanmoins elles portent la signature d une differenciation magmatique plus prononcee en gravissant les niveaux stratigraphiques on observe une diminution de la composante an du plagioclase de an73 et an51 et du mg de l augite de mg 75 a mg 56 un accroissement pour roches totales du rapport la yb de 0 5 a 2 9 et une decroissance pour roches totales des teneurs en cr de 770 a 5 ppm et en ni de 315 a 45 ppm les concentrations des elements du groupe du platine egp sont quasiment sous leur limite de detection la comparaison de ces compositions avec celles du complexe du bushveld d afrique du sud montre que les niveaux exposes a la base du complexe sont equivalents a la frontiere des zones critique principale c est a dire du toit immediat des filons porteurs des egp les etudes geophysiques recentes ont revele que le complexe de bell river a une epaisseur d environ 5 km et a partir de cette donnee nous inferons l existence d une zone ultramafique cachee et nous proposons un site pour entreprendre un programme de forage d exploration une comparaison des compositions obtenues pour le complexe de bell river avec les basaltes et rhyolites associes des groupes de watson lake et de wabassee suggere que les trois suites sont cogenetiques sachant que de nombreux depots majeurs de sulfures massifs volcanogeniques smv dans la region sont localises tout autour d une intrusion et que l intrusion et les roches volcaniques sont sensiblement du meme ge par consequent nous adherons aux interpretations anterieures suggerant que i intrusion et les depots des smv sont lies genetiquement c est a dire que le complexe de bell river represente la source de chaleur qui activait la circulation des fluides hydrothermaux responsables de la formation des depots de smv

tectonothermal evolution of the triassic flysch in the bayan har orogen tibetan plateau abstract the bayan har orogen comprises a major part of the qingzang dianxi fold region in western china it preserves important information of the tectono thermal evolution covering the time span from the closure of the paleo tethys ocean up to the formation of the himalayas low temperature metamorphic indicators such as mineral assemblages illite crystallinity ic chlorite crystallinity cc illite polytype b cell dimension of k white micas geothermometry of selected minerals were analyzed the values of kubler index ki of the triassic flysch in the bayan har orogen range from 0 23 1 63 2 while arkai index ai in a range of 0 21 0 60 2 iso thermal zones mapped with ki describe a pair of anchizones and an anchiregion within the bayan har orogen the giant yushu anchizone in the southwest extending 750 km long and 100 km wide the zaling eling lakes anchizone in the center about 150 km long and 40 km wide and the xing tong zhe anchiregion in the northeast covering an area of roughly 60 000 km 2 they are separated by diagenetic zones peak metamorphic conditions are estimated around 280 330 c and a low to intermediate n new hampshire pressure type a slight change with increasing then decreasing pressure was observed from sw to ne the relationship between anchimetamorphic pattern of triassic flysch and large scale folds and faults indicates syn to post structural metamorphism compression at the end of the triassic induced by the interaction of the tarim north china and indian blocks caused the closure of the paleo tethys ocean and led to the folding of the triassic flysch within the paleo tethys ocean basin anchimetamorphism may have been caused by crustal thickening of 10 km due to an accretionary wedge setting and a temperature increase in those rocks due to burial such a regional metamorphic pattern would provide important information for reconstruction of palaeotectonic palaeogeograph and the evolutionary history of tibetan plateau

u pb geochronology of the eastern abitibi subprovince part 1 chibougamau matagami joutel region u pb zircon titanite and baddeleyite ages are reported for 20 volcanic and plutonic rock units in the chibougamau matagami and joutel areas of the northern abitibi belt pretectonic magmatism occurred in three main pulses volcanic rocks of the obatagamau formation in the chibougamau area were erupted at 2759 ma following a possible hiatus in igneous activity volcanism accompanied by the emplacement of layered mafic intrusions occurred in the chibougamau matagami and joutel areas in the period of 2730 2722 ma in the chibougamau area a slightly younger period of plutonism between 2720 and 2712 ma is thought to be comagmatic with felsic volcanic rocks in the uppermost part of the roy group syntectonic intrusive rocks in the northern abitibi belt range in age from 2701 to 2693 ma these ages are broadly comparable to ages obtained for syntectonic plutons elsewhere in the abitibi belt suggesting that tectonism associated with the kenoran orogeny occurred at approximately the same time throughout

new insights into the formation of diagenetic illite from tem studies diagenetic illite from the proterozoic chuanlinggou formation china has been investigated using the techniques of transmission electron microscopy tem selected area electron diffraction saed x ray diffraction xrd scanning electron microscopy sem and energy dispersive spectrometer eds polytypes of 1 m d and 1 m illite coexist in the diagenetic illite the 1 m d polymorph is predominant in the 0 2 m size fraction which has high al and low mg contents and irregular crystal shapes lattice fringe imaging and one dimensional structural imaging show abundant structure defects the 1 m d illite has both layer and sheet terminations caused by edge dislocations and layer displacements along c caused by screw dislocations these observations indicate that the disordered 1 m d structure of the diagenetic illite resulted from abundant dislocations the dislocation serves as nucleation sites for the illite nano particles to spontaneously nucleate in the initial stage of illite formation such a nucleation process obeys the ostwald ripening rule the illite only shows a 1 0 nm thickness for each layer in high resolution tem images which suggests that the illite crystals have no mixed smectite layer and the 1 m d illites are authigenic and not illitized from smectite or illite smectite heterogeneous nucleation led to directly crystallization of the 1 m d illite during the initial growth of illite in shale under a low temperature and tectonic stress free environment the results have implications for interpreting the distribution of 1 m d illite in sedimentary rocks

2d joint inversion of geophysical data using petrophysical clustering and facies deformation geologic expertise and petrophysical relationships can be brought together to provide prior information while inverting multiple geophysical data sets the merging of such information can result in more realistic solution in the distribution of the model parameters we have evaluated the geophysical inverse problem in terms of gaussian random fields with mean functions controlled by petrophysical relationships and covariance functions controlled by a prior geologic cross section including the definition of spatial boundaries for the geologic facies the petrophysical relationship problem is formulated as a regression problem upon each facies the inversion of the geophysical data is performed in a bayesian framework we have developed the usefulness of this strategy using a first synthetic case for which we have performed a joint inversion of gravity and galvanometric resistivity data with the stations located at the ground surface the joint inversion was used to recover the density and resistivity distributions of the subsurface in a second step we considered the possibility that the facies boundaries were deformable and their shapes were inverted as well we used the level set approach to perform such deformation preserving a priori topological properties of the facies throughout the inversion with the help of a priori facies petrophysical relationships and the topological characteristics of each facies we made a posteriori inference about multiple geophysical tomograms based on their corresponding geophysical data misfits we have applied this method to a second synthetic case showing that we can recover the heterogeneities inside the facies the mean values for the petrophysical properties and to some extent the facies boundaries using the 2d joint inversion of gravity and galvanometric resistivity data

fault geometry and spatial clustering of microearthquakes along the dead sea jordan rift fault zone abstract earthquakes 1 0 m l 5 3 in the region around the dead sea jordan rift fault zone recorded by the israel scismograph station network issn from 1982 until the beginning of 1989 have been analyzed and interpreted the scismicity pattern clearly reveals activity along three fault zones the dead sea jordan rift fault zone the carmel faraa fault zone and the central sinai negev shear zone microearthquake occurrence tends to cluster in or near tensional features rhomb shaped grabens such as the hula sea of gallilee and dead sea depressions further eight representative focal mechanisms of individual earthquakes or earthquake clusters have been derived the seismicity and focal mechanism solutions near the branching of the carmel faraa and the dead sea jordan rift fault zones suggest a complicated tectonic breakup in this region microearthquakes in the arava may indicate a more complex pattern of active faults than was previously assumed

targeting nickel sulfide deposits from 3d seismicreflection data at kambalda australia abstractthe greenstone belts of the yilgarn craton western australia host numerous archaean gold nickel and iron ore deposits these deposits typically are found in complex geologic structures hidden by a deep heterogeneous and often conductive regolith profile this added complexity limits the depth of penetration for the potential field methods but at the same time opens new revenue possibilities through the application of seismic methods to explore this opportunity we acquired high resolution experimental 3d seismic data over lake lefroy in kambalda western australia the main objective was to map exceptionally complex deep structures associated with kambalda dome survey design used 3d ray tracing to improve the distribution of the common reflection points across ultramafic basalt contacts which host numerous small high grade nickel sulfide deposits a combination of small explosive sources high shot receiver density and exceptionally good coupling over the ultrasalty lake surface prod

seismic reflection imaging over a massive sulfide deposit at the matagami mining camp quebec a 2 d seismic reflection profile was shot across the southern flank of the matagami mining camp almost directly above the recently discovered bell allard massive sulfide deposit now estimated at more than 6 million metric tons all orebodies found in the southern part of the mining camp including bell allard are located at the contact between the primarily basaltic wabassee group and the underlying rhyolitic watson lake group seismic reflections were recorded from the basalt rhyolite contacts of the lower wabassee group as well as from gabbro sills that intrude much of the volcanic stratigraphy a strong reflection from the top of the bell allard orebody was also detected but the reflection does not extend over the full width of the deposit as defined by drilling appearing to correlate with the lower pyrite rich zone faulting which can be interpreted from discontinuities in the observed reflections probably controlled the formation of the bell allard deposit if the interpreted gabbro sills are accepted as isotime markers then faulting of the deeper sill complex defines a series of half grabens within the rhyolitic watson lake group the bell allard deposit is found at the intersection of one of these apparently low angle normal faults with the top of the watson lake group indicating that sulfide mineralization may have been associated with fluid flow along the fault which likely penetrates to the underlying mafic intrusion although the precise geometry of subsurface faulting cannot be estimated from a single 2 d seismic profile these results indicate that a full 3 d seismic survey should allow the mapping of many of the subsurface fault systems and the verification of hypotheses of fault controlled deposit formation

feasibility of virtual source reflection seismology using interferometry for mineral exploration a test study in the lalor lake volcanogenic massive sulphide mining area manitoba canada approximately 300 hours of ambient noise data were recorded on a grid of receivers covering an area of 4 km2 over the lalor mine canada to test the capability of seismic interferometry to image ore deposits in the crystalline rock environment underground mining activities create the main source of ambient noise in the area alongside the ambient noise survey a larger three dimensional active source seismic survey was also acquired and used to evaluate the interferometry results power spectral density calculations show random ambient noise with a frequency range of 2 hz 35 hz a beamforming analysis identified body waves arriving from the west northwest pointing towards the mine and surface waves propagating from the northeast the calculated virtual shot gathers retrieved by cross correlating ambient noise at all receivers were processed following both two dimensional and three dimensional approaches using a sequence similar to the one applied to the activesource three dimensional data the dip moveout stacked section reveals a number of events similar to those observed on the processed active seismic sections in particular the passive seismic interferometry method is capable to partly image shallowly dipping reflections but did not produce convincing images of steeply dipping reflections dip moveout stacked sections obtained with different cross correlation time windows indicate that the strength and number of reflections generally increase with longer noise records however a few reflections at depth show reduced coherency with longer noise time windows the passive seismic interferometry results over the lalor mining area are encouraging but image quality of the passive survey is lower than the acquired active three dimensional survey at the area future ambient noise surveys with longer offsets shorter receiver spacing and wider azimuth distribution are needed in crystalline rock environment to address the potential of the method for mineral exploration

seismic methods in mineral exploration and mine planning a general overview of past and present case histories and a look into the future abstractdue to high metal prices and increased difficulties in finding shallower deposits the exploration for and exploitation of mineral resources is expected to move to greater depths consequently seismic methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration these methods also can be used with varying degrees of success to directly target mineral deposits at depth we review important contributions that have been made in developing these techniques for the mining industry with focus on four main regions australia europe canada and south africa a wide range of case studies are covered including some that are published in the special issue accompanying this article from surface to borehole seismic methods as well as petrophysical data and seismic modeling of mineral deposits at present high resolution 2d surveys mostly are performed in mining areas but there is a general increasing trend in the use of 3

2d analysis of earthquake ground motion in haifa bay israel we study the earthquake response of the zevulun valley basin underlying northern israel s largest urban area with 2d viscoelastic seismic modeling of a detailed geological section we found that amplification of the horizontal vibrations the ratio of basin to no basin response spectra correlates with basin depth in the deepest portion of the basin qishon graben long periods 2 5 sec are amplified by 400 in the shallowest portion of the basin afeq horst shorter periods 0 5 sec are amplified by 300 400 these resonances in the vertical direction through the basin are strong enough that their amplitude overwhelms the amplitude of a previously recognized basin edge effect the horizontal vertical h v fourier spectral ratios based on 124 ambient noise measurements do not fully coincide with the basin to no basin fourier spectral ratios of the simulation but the resonance frequencies found in both methods are alike moreover the relation between the resonance frequency and the depth of the corresponding seismic reflector in the simulation is almost identical to the empirical frequency depth relations obtained from measurements this indicates that the average shear wave velocity of the sedimentary column in the model is consistent with measurements to evaluate the necessity of 2d analysis we performed additional 1d simulations at two locations along the section for the qishon graben 1d analysis underestimates the amplification factor relative to 2d by 25 whereas for the afeq horst 1d and 2d simulations are similar for a hard layer within the soft qishon graben fill we found that when the hard layer is thinner than 50 m its influence on ground motion is small

stochastic inversion of a gravity field on multiple scale parameters using surface and borehole data a 3d stochastic inversion method based on a geostatistical approach is presented for three dimensional inversion of gravity on multiple scale parameters using borehole density and gravity and surface gravity the algorithm has the capability of inverting data on multiple supports the method involves four main steps i upscaling of borehole densities to block densities ii selection of block densities to use as constraints iii inversion of gravity data with selected block densities as constraints and iv downscaling of inverted densities to small prisms two modes of application are presented estimation and simulation the method is first applied to a synthetic stochastic model the results show the ability of the method to invert surface and borehole data simultaneously on multiple scale parameters the results show the usefulness of borehole data to improve depth resolution finally a case study using gravity measurements at the perseverance mine quebec canada is presented the recovered 3d density model identifies well three known deposits and it provides beneficial information to analyse the geology of massive sulfide for the domain under study

stratigraphic and structural aspects of the volcanic rocks of the matagami mining camp quebec implications for the norita ore deposit the matagami mining camp is an important base metal producer in the canadian shield the volcanic stratigraphy of the area is folded into the galinee anticline which is an east west trending and west plunging regional fold the south flank consists of a low strain do main characterized by a southeast trending volcanic sequence dipping moderately at 45 degrees to the south the stratigraphic succession is well defined with the watson lake group at the base comprising a lower dacitic unit and an upper quartz porphyritic rhyodacite unit all but one of the deposits lie along the key tuffite unit located at the top of the watson lake group the north flank of the anticline is affected by a series of east west and northwest trending high angle reverse shears which defines the lac garon high strain zone the volcanic sequence within this zone is displaced into four overlapping sigmoidal segments in which stratigraphic reconstruction is possible the norita massive sulfide deposit located in the center of the north flank has been deformed and faulted its internal metal zonation and its underlying stringer zone were flattened and rotated its present geometry suggests that it was deformed during north side up high angle reverse movement this sense of strain is compatible with the displacement of the marker units inside the lac garon high strain zone and the morphological modifications are believed to be consistent with the movement within this zone it is suggested that the norita massive sulfide deposit is a deformed equivalent of the less deformed south flank massive sulfide deposits and in contrast with an earlier suggestion of a distal origin shares the same genetic traits as the south flank deposits

seismic activity along fault branches of the dead sea jordan transform system the carmel tirtza fault system abstract about 550 earthquakes 1 0 m l 5 3 along the carmel tirtza fault a branching fault of the jordandashdead sea transform system recorded by the israel seismograph network isn between 1984 and 1994 were analyzed the seismicity pattern reveals significant activity often confined to known surface traces of active faults or within local grabens earthquake clusters are also observed the seismicity pattern within the mediterranean seems more diffuse possibly due to observational inaccuracies and insufficient knowledge of how the carmel tirtza fault system extends towards the northwest the seismicity along the carmel tirtza fault system since the beginning of this century is characterized by a b value of about 0 9 for 15 events with 3 1 m l 5 3 we found seismic moment estimates m 0 of 0 7 10 14 m 0 10 17 nm and brune stress drop estimates between 0 9 and 16 4 mpa these characteristics are comparable to those for events occurring on the main dead sea jordan transform fault ten individual earthquake focal mechanisms and three joint focal mechanisms for earthquake clusters have been obtained towards the northeastern part of the carmel tirtza fault system a left lateral motion seems to dominate while the seismicity pattern and the focal mechanism solutions near the branching of the carmel tirtza fault and the dead sea jordan rift suggest the present day existence of a complicated tectonic regime stress inversion assuming one stress tensor for the whole region indicates nne ssw extension and wnw ese compression

active tectonics of the yizre el valley israel using high resolution seismic reflection data abstract we present a series of high resolution seismic reflection lines across the yizre el valley which is the largest active depression in israel off the main trend of the dead sea rift the new seismic reflection data is of excellent quality and shows that the valley is dissected into numerous small blocks separated by active faults the yizre el valley is found to consist of a series of half grabens rather than a single half graben or a symmetrical graben the faults are generally vertical and appear to have a dominant strike slip component but some dip slip is also evident a marked zone of compression near megido is associated with the intersection of the two largest faults in the valley the carmel fault and the gideon fault variable trend of the faults reflects the complexity of the local geology along the boundary between the wide nw se trending farah carmel fault zone and the e w trending basins and ranges in the lower galilee this tectonic complexity is likely to result from a highly variable stress pattern modified by the structures inside it normal faulting in the valley occurred at an early stage of its development as a tectonic depression however strike slip motion on the carmel fault and possibly also on some of the other faults appears to have started together with the onset of normal faulting earthquake hazard in the area appears to be uniform as faults are distributed throughout the yizre el valley