along strike variations of earthquake apparent stress at the nicoya peninsula costa rica subduction zone oceanic plates vary in temperature topography and sediment load as they enter subduction zones these variations persist along the subduction interface causing perturbations in coupling and earthquake rupture processes we explore the effects of variable subducting plate structure on microseismicity rupture characteristics along the nicoya peninsula costa rica the subducting cocos plate has low relief along the northern and central portion of the peninsula with seamounts present at the southern tip of the peninsula we compute apparent stresses for 94 ml 2 5 4 2 earthquakes along the plate interface using waveform coda and find along strike variations that mimic bathymetric variability median stress values are higher 3 2 mpa in the smooth northern region with lower values in the central 2 1 mpa and southern 0 7 mpa segments higher apparent stresses along a zone of little suspected subduction topography imply increased coupling or higher friction along the interface these results agree with geodetic and other seismic studies that suggest variable plate coupling along the nicoya peninsula

regional moment tensor inversion for strong aftershocks of the august 17 1999 izmit earthquake mw 7 4 we analyzed the source mechanisms of the thirty largest aftershocks 4 0 ml 6 2 of the august 17 1999 izmit earthquake mw 7 4 by applying the regional moment tensor inversion method using data from near regional broadband stations the inversion solutions were compared to 17 well constrained first motion solutions and were seen to be in good agreement we found that the dominance of strike slip motion is the main characteristic of the izmit earthquake sequence significant aftershock activity was recorded to the west and east of the un ruptured extremities in the east the aftershocks located near the town of duzce represent an early replica of the november 12 1999 duzce earthquake mw 7 2 in terms of locations and source mechanisms in the marmara sea where the fault geometry is still very poorly resolved most aftershocks have right lateral strike slip solutions with strike direction parallel to the submerged branches of the north anatolian fault

reply to the comments by marignac and cathelineau on the paper by sanchez espana et al source and evolution of ore forming hydrothermal fluids in the northern iberian pyrite belt massive sulphide deposits sw spain evidence from fluid inclusions and stable isotopes mineralium deposita 38 519 537

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

low temperature low pressure deformation and metamorphism of the vangorda massive sulphide orebody yukon canada the vangorda orebody is a small stratiform massive sulphide orebody located in anvil district yukon canada the orebody consists of fineto medium grained semi massive and massive sulphides with a common sulphide mineralogy of pyrite pyrrhotite sphalerite galena and minor chalcopyrite the host rocks and the sulphide lithofacies have been complexly deformed during two phases of deformation d1 and d2 and associated metamorphism m1 and m2 the effects of d1 and m1 are penetratively overprinted by d2 and m2 d2 and m2 resulted in tight to isoclinal f2 folding of the orebody remobilisation of the sulphides recrystallisation and development of shear zones along the limbs of the f2 folds chlorite thermometry and sulphide thermobarometry have been carried out on the host phyllites and on the sulphides chlorite was analysed from the s1 and s2 foliations in the phyllites to determine m1 and m2 temperatures respectively however no difference was found between chlorite compositions in these foliations and a mean temperature of 363 c was calculated from the tetrahedral a1iv occupancy arsenopyrite thermometry yielded a comparable mean temperature of 336 c sphalerite inclusions in m2 pyrite porphyroblasts from d2 shear zones were analysed for pressure using the sphalerite hexagonal pyrrhotite pyrite barometer inclusions were analysed in an attempt to determine if relic m1 sphalerite and hence pressure signature was preserved inclusion compositions appear to reflect only m2 conditions and yielded a mean pressure of 4 0 kb sphalerite hexagonal pyrrhotite assemblages were analysed from d2 shear zones to determine the m2 pressure using the sphalerite hexagonal pyrrhotite barometer these calculations yielded a mean pressure of 6 1 kb the m2 temperatures and pressures calculated using these calibrations are in good agreement with those estimated from petrogenetic relationships

long period regional wave moment tensor inversion for earthquakes in the western united states source parameters of moderate to large size mw 4 5 earthquakes in the western united states from 1992 to 1994 are determined by point source moment tensor inversion of complete long period t 35 50 s ground motions recorded at regional distances 1 12 stable long period signals are obtained by low pass filtering records from the very broadband seismometers recently deployed in several networks in the western united states these signals are dominated by fundamental mode rayleigh and love waves which have very simple waveforms due to the limited dispersion on the short paths to regional stations since long period motions are relatively insensitive to the attenuation model and crustal structure used in the inversion they provide robust constraints on the seismic moment and faulting geometry as long as adequate azimuthal coverage is available comparisons of solutions for 21 events with results of other regional and teleseismic wave inversions are made to assess the model dependence and uncertainties of our regional centroid moment tensor rcmt solutions rcmt inversion has limited source depth resolution for shallow crustal events but the focal mechanism and seismic moment determinations prove quite stable over a range of source depths in the crust as well as over a range of crustal propagation models simultaneous waveform inversion of shorter period body wave signals can improve the source depth resolution by applying path corrections for heterogeneous crustal structure shorter period surface wave energy can also be inverted allowing the methodology to be extended to lower magnitude regional events as well the rcmt procedure requires minimal signal processing only a sparse broadband network and a simple laterally homogeneous propagation model thus it can readily be automated and applied in near real time to events in the magnitude range from 4 5 to 7 5 distributed over an area as large as the western united states

quartz cemented breccias from the mid atlantic ridge samples of a high salinity hydrothermal upflow zone textural mineralogical chemical and fluid inclusion studies on a suite of quartz rich sulfide bearing greenstone breccias indicate that high salinity high fluid flow systems were recently active on the mid atlantic ridge south of the kane fracture zone these systems involved fluids with temperatures close to 300 c and salinities almost 3 times that of seawater rounded pebblelike fragments enclosed within a matrix of euhedral quartz crystals appear to have been cemented by quartz deposition from a moving fluid which attained velocities in excess of 1 m s homogenization temperatures and freezing point depression effects in fluid inclusions from texturally early and late quartz crystals indicate temporal evolution of fluid temperatures and nacl equivalent salinities from 290 c and 10 wt to 200 c and 4 7 wt during alteration and cementation of the breccias highly variable cobalt concentrations in the evolving hydrothermal solutions are indicated by fine scale oscillatory zoning in euhedral pyrite within the breccias a continuous supply of the high salinity fluids may be generated either by supercritical two phase separation at depths well below the level of inclusion entrapment or by retrograde dissolution of hydroxy chloride phases in the deeper portions of the hydrothermal system either model requires the initial temperature of the deeply circulating fluids to have been distinctly higher than 415 c and the fluid to have been cooled by conduction or by mixing with lower temperature seawater prior to entrapment within the inclusions

the geometry of the north anatolian transform fault in the sea of marmara and its temporal evolution implications for the development of intracontinental transform faults the north anatolian fault is a 1200 km long strike slip fault system connecting the east anatolian convergent area with the hellenic subduction zone and as such represents an intracontinental transform fault it began forming some 13 11 ma ago within a keirogen called the north anatolian shear zone which becomes wider from east to west its width is maximum at the latitude of the sea of marmara where it is 100 km the marmara basin is unique in containing part of an active strike slip fault system in a submarine environment in which there has been active sedimentation in a paratethyan context where stratigraphic resolution is higher than elsewhere in the mediterranean it is also surrounded by a long civilised rim where historical records reach well into the second half of the first millennium bce before common era in this study we have used 210 multichannel seismic reflexion profiles adding up to 6210 km profile length and high resolution bathymetry and chirp profiles reported in the literature

a new sulphur isotopic study of some iberian pyrite belt deposits evidence of a textural control on sulphur isotope composition the sulphide deposits of the iberian pyrite belt ipb represent an ore province of global importance our study presents 113 new sulphur isotope analyses from deposits selected to represent the textural spectrum of ores measured 34s values range from 26 to 10 mostly for massive and stockwork ores in agreement with data previously published in situ laser 34s analyses reveals a close correlation of 34s with texture primary diagenetic textures are dominated by relatively low 34s 8 to 2 whereas stockwork feeder textures are dominated by higher 34s 3 to 5 intermediate textures mainly coarse textures in stratiform zones have intermediate 34s although they are mostly dominated by the high 34s component rare barite has a homogeneous 34s around 18 which is consistent with direct derivation from lower carboniferous seawater sulphate a dual source of sulphide sulphur in the ipb deposits has been considered a hydrothermal source derived from reduction of coeval seawater sulphate in the convective systems is represented by sulphide in the feeder zones here variations in 34s are caused by variations in the extent of the sulphate reduction which governs the so4 h2s ratio the second end member was derived from the bacterial reduction of coeval seawater sulphate at or near the surface as reflected in the primary textures a distinct geographical variation in 34s and texture from sw more bacteriogenic and primary textures to ne more hydrothermal textures and 34s which reflects a variation in the relative input of each source was likely controlled by local geological environments given that the sulphur isotope characteristics of the ipb deposits are unlike most vms and kuroko deposits and noting the dominance of a mixed reduced sedimentary and volcanic environment we suggest that the ipb could represent an ore style which is intermediate between volcanic and sedimentary hosted massive sulphide types

the precious metal rich south hercules mineralization western tasmania a possible subsea floor replacement volcanic hosted massive sulfide deposit south hercules is a newly delineated disseminated to semimassive base metal sulfide deposit with significant gold and silver grades the deposit lies a kilometer along strike south from the hercules mine a 2 0 mt polymetallic massive sulfide deposit in the mount read volcanics belt western tasmania the mineralization and alteration at the south hercules deposit has been divided into two major facies the mineralized sulfide facies and the carbonate facies the carbonate facies interfingers with and surrounds the upper part of the sulfide facies the mineralized sulfide facies includes three zones a massive pyrite or barite zone a siliceous or stringer sulfide zone and a sphalerite galena or pyrite zone the carbonate facies also consists of three zones a blebby carbonate chlorite zone a massive carbonate zone and a cherty carbonate zone the massive pyrite or barite zone contains significant gold grades and occurs mostly at the top of the sulfide facies this zone is characterized by colloform aggregates of pyrite and compact massive pyrite in chert the siliceous or stringer sulfide zone is a silicified and sericitized tuffaceous shale with disseminated to stringer pb zn mineralization the massive sphalerite galena or pyrite zone contains subordinate gold and silver and occurs as thin lenses toward the base of the sulfide facies significant zinc and lead values occur throughout the mineralized sulfide facies with the highest values occurring along stratigraphically controlled layers copper values are conspicuously low throughout the south hercules deposit rarely exceeding 0 5 percent the carbonate facies is conspicuous by its lack of significant precious metal and base metal grades mineragraphic investigations indicate that electrum occurs in two general associations with pyrite and with other sulfides such as sphalerite galena and tetrahedrite the electrum locked in the pyrite euhedra is generally fine grained 5 40 mu m whereas the electrum associated with other sulfides displays a range between 5 and 200 mu m microprobe analysis indicates that the fineness 1 000 au au ag wt for gold in the deposit ranges from 427 to 965 the delta 18 o isotope composition of the carbonate varies from 9 8 to 16 7 per mil and the delta 13 c values range from 3 5 to 0 6 per mil the calculated isotopic composition of the ore fluid at 150 degrees and 250 degrees c is consistent with derivation from evolved seawater sulfur isotope analyses of selected samples from the mineralized facies give delta 34 s values of 8 2 to 14 1 per mil which is in the same range as values from the rosebery deposit and consistent with values of sulfur derived from cambrian seawater the form texture mineralogy stable isotopes and fluid inclusion data for the south hercules deposit suggest that it was formed largely by a subsea floor replacement process from relatively low temperature 150 degrees 250 degrees c near neutral fluids the very low copper content and relatively high au ag pb zn ratio of the ores support a low temperature environment in which gold was transported as the au hs 2 super complex and pb and zn were transported as chloride complexes

link between coulomb stress changes and seismic activation in the eastern marmara sea after the 1999 izmit turkey earthquake 1 we investigate the effect of dynamic and static stress changes produced by the 1999 izmit earthquake on four preexisting seismic clusters located in the eastern marmara sea beyond the western termination of the earthquake rupture these four clusters show long lasting modifications in their seismicity rate we observe that these seismic activity variations are related to stress changes dynamic stress pulses activate strike slip faulting instantaneously but in the absence of a concomitant static coulomb stress increase this activation is short lived indeed a large dynamic stress combined with a negative static coulomb stress may result in an immediate activation followed by the occurrence of a seismicity shadow in contrast the activation of extensional clusters begins slowly and takes a few days to fully develop it is also remarkably long lasting and does not follow a classical omori decay more than 10 years after the earthquake the extensional clusters located near the termination of the rupture where static stress and pressure changes were high are still activated

a complex seismogenic shear zone the duzce segment of north anatolian fault turkey abstract this work highlights how surface geological data can integrate and complete a fault characterization including its seismogenic depth we investigated the area struck by the november 1999 mw 7 1 earthquake that ruptured the duzce segment of the north anatolian fault zone nafz after the august 1999 mw 7 4 izmit earthquake to explore the persistency or evolution of the active fault setting at the surface we compared detailed coseismic surface expressions with the long term morphology and structural architecture of the duzce zone we identified a simple 1999 coseismic fault trace cft and an older complex fault system rfs involving a wider zone of deformation two different parts of the duzce segment were recognized a western section presents a staircase trajectory of the coseismic fault trace that reactivated part of the older fault system an eastern section presents a straight coseismic fault trace that cross cuts the older and complex fault system the western duzce fault segment splays out from the izmit counterpart of the nafz forming a releasing fault junction by comparing a model of its coseismic surface deformation field with the long term morphology we observed that the present topography of this western section results from the nafz activity by repeating coseismic deformations like those in 1999 the mechanical interaction in the release fault junction produces local transtension across the western duzce fault and justifies its stable complexity it does not evolve into a straight trace the surface boundary between the duzce fault sections also separates at depth two fault sections one with low slip to the west and another with a big asperity to the east thus the izmit duzce interaction 1 may produce an unfavorable setting for a build up of asperities in the western duzce segment and 2 could delay the propagation of the izmit rupture along the duzce segment that nucleates mainshocks only on its eastern section in other words the arrangement of the fault junction may permanently control how the two sections of the duzce fault behave and rupture

investigation of the tectonics of the main marmara fault by means of deep towed seismic data abstract we report a study of the active principal deformation zone pdz of the main marmara fault mmf in the sub basins of the sea of marmara by means of deep towed seismic pasisar as well as multi beam bathymetry data collected by ifremer s r v le suroit in september 2000 our main objective is to investigate the active deformation within the uppermost sedimentary layers with a much higher resolution than hitherto has been available to the west of the sea of marmara the pdz is located along the southern flank of the tekirdag basin where the sediments are affected by steep reverse faults dipping toward the north e w strike slip faults are also observed in the central part of the tekirdag basin and thrusting occurs along its n50 trending margin we interpret these structures in terms of a slight clockwise rotation in the basin north of the pdz to the east the pdz enters the central basin and follows a steep scarp along the southern flank of a tectonic depression the scarp consists of an en echelon fault system with a normal component these faults are combined with small parallel anticlines and synclines that extend along the southern portion of the depression the northern scarp of the depression is made of a mixed system of faults with both normal and reverse components associated with anticlines and synclines these faults are best interpreted as right lateral strike slip faults with a vertical component that is dominantly normal these faults and the sigmoid shape of the depression are compatible with a clockwise rotation above the pdz this recent tectonic structure appears to be superimposed over a pre existing graben that is now essentially deactivated the pdz continues eastwards out of the central basin as a n50 e trending nw verging thrust system toward the kumburgaz basin that is located on a restraining bend of the pdz this shortening zone consists of two main n60 e trending branches the northern one is more pronounced and composed of two successive restraining bends the southern branch is smoother and forms a gently curved connection between the two segments of the pdz this suggests that the pdz migrates southward to cut through this restraining bend further east the pdz enters the cinarcik basin along its northern scarp active deformation observed on the pasisar profiles along the 290 trending eastern portion of this scarp consists of n110 5 trending dextral strike slip faults connecting short segments of active n130 140 normal faults that control elongated depocenters along the southern flank of the cinarcik basin the e w izmit fault enters the basin from the east pasisar data confirm the extension of the izmit strike slip fault into the cinarcik basin and the large development of normal faulting along the southern flank of the basin some of the normal faulting observed here may be related to horse tail termination of the izmit fault while most of it is the expression of strain partitioning

discrimination of the fault plane by waveform modeling a case study for moderate sized earthquakes in taiwan using nearby strong motion recordings and a finite source model we determine the focal mechanisms and identify the activated fault planes of two earthquakes of seismotectonic interest in taiwan the 15 december 1993 tapu m w 5 5 and the 17 july 1998 rueyli m w 5 7 these events occurred about 35 km apart in the same geological province which is characterized mainly by north northeast trending thrust faults as well as some strike slip faults they are moderate sized events that did not produce surface ruptures therefore the identification of fault planes appears a significant issue for this region accommodated in a complex tectonic environment and constitutes the main objective of this article both events were located in the vicinity of the chukou tachienshan fault system which is known to be dominated by east dipping thrust faults and both earthquakes resulted in almost pure reverse source mechanisms however we find that the two ruptures dip in opposite directions the northwest dipping fault of the tapu earthquake being in disagreement with the nearby fault system for the rueyli event we show that fault plane discrimination becomes effective when more than three stations are used and that certain stations contribute more than others we infer that this latter event occurred on one of the secondary east dipping thrust faults parallel to the tachienshan fault

source and evolution of ore forming hydrothermal fluids in the northern iberian pyrite belt massive sulphide deposits sw spain evidence from fluid inclusions and stable isotopes a fluid inclusion and stable isotopic study has been undertaken on some massive sulphide deposits aguas tenidas este concepcion san miguel san telmo and cueva de la mora located in the northern iberian pyrite belt the isotopic analyses were mainly performed on quartz chlorite carbonate and whole rock samples from the stockworks and altered footwall zones of the deposits and also on some fluid inclusion waters homogenization temperatures of fluid inclusions in quartz mostly range from 120 to 280 c salinity of most fluid inclusions ranges from 2 to 14 wt nacl equiv a few cases with th 80 110 c and salinity of 16 24 wt nacl equiv have been also recognized in addition fluid inclusions from the soloviejo mn fe jaspers 160 190 c and 6 wt nacl equiv and some late to post hercynian quartz veins 130 270 c and 4 wt nacl equiv were also studied isotopic results indicate that fluids in equilibrium with measured quartz 18ofluid 2 to 4 chlorites 18ofluid 8 14 dfluid 45 to 27 whole rocks 18ofluid 4 7 dfluid 15 to 10 and carbonates 18oankerite 14 5 16 13cfluid 11 to 5 evolved isotopically during the lifetime of the hydrothermal systems following a waxing waning cycle at different temperatures and water rock ratios the results fluid inclusions 18o d and 13c values point to a highly evolved seawater along with a variable but significant contribution of other fluid reservoirs such as magmatic and or deep metamorphic waters as the most probable sources for the ore forming fluids these fluids interacted with the underlying volcanic and sedimentary rocks during convective circulation through the upper crust

the rupture process and asperity distribution of three great earthquakes from long period diffracted p waves moment tensor source mechanisms for the largest twenty nine shallow earthquakes from 1981 m s 6 5 have been determined using long period rayleigh wave spectra and p wave first motions recorded by the international deployment of accelerograms ida global digital seismic network gdsn and world wide standardised seismic network wwssn these are compared with the centroid moment tensor mechanisms presented by dziewonski and woodhouse which were obtained in a contrasting manner in most cases the source is well represented by a single double couple mechanisms with good agreement of scalar moment and orientation between the two studies apparent mismatches for other cases may be interpreted in terms of source complexity we emphasise the objectivity of comparing moment tensor elements apparent discrepancies in the moment and orientation of double couple fault plane solutions are usually due to differences in the mxz and myz moment tensor elements which are poorly constrained by long period data

crustal lineament control on magmatism and mineralization in northwestern argentina geological geophysical and remote sensing evidence abstract the relationship between long lived deep crustal lineaments and the locations of magmatic centers and associated mineral deposits has been investigated in the puna region of northwestern argentina through the analysis of regional aeromagnetic surveys landsat images and geological information the good exposure and excellent preservation of basement and supracrustal geology in this region makes it particularly suitable for such a study at a regional scale several contrasting magnetic domains are recognized which correlate with crustal geology two basement domains are separated by a nne trending boundary which is believed to correlate with a paleozoic suture zone between the pampia to the southeast and arequipa antofalla terranes to the northwest locally overlying these basement terranes is the cenozoic magmatic domain which is best developed in the n s trending volcanic arc at the western edge of the puna the cordillera occidental in addition four southeast trending volcanic zones extend for several hundred kilometers across the puna many important mineral deposits and areas of hydrothermal alteration are associated with these volcanic breakouts and we have selected three such areas for more detailed study bajo de la alumbrera argentina s largest porphyry copper deposit cerro galan the largest ignimbrite caldera in argentina with associated hydrothermal alteration zones and el queva a historic polymetallic district located within a major volcanic range a comparison of lineament maps generated from aeromagnetic and landsat tm images reveals broad correlation between these different remote sensing techniques which respectively highlight subsurface magnetic and surface geological features in addition the locations of magmatic and hydrothermal centers can be related to the interpreted structural framework and are seen to occur near the intersections of major lineament zones it is suggested that in three dimensions such intersection zones form trans lithospheric columns of low strength and high permeability during transpressional or transtensional tectonic strain and may thereby serve as conduits for magma ascent to the shallow crust pooling of large volumes of deeply derived magma in shallow crustal magma chambers may then result in voluminous devolatilization and the formation of hydrothermal mineral deposits it is important to note that in this model structural intersections serve as facilitators for magma ascent and volatile exsolution but do not in themselves cause this process other factors such as magma supply rate and tectonic stress are essential primary ingredients and local magmatic and volcanic processes affect the ultimate potential for ore formation nevertheless we suggest that lineament analysis provides a valuable framework for guiding the early stages of mineral exploration other regional and local geological considerations must then be applied to identify priority targets within this framework

centroid single force inversion of seismic waves generated by landslides the centroid moment tensor cmt waveform inversion method of dziewonski et al 1981 is modified to analyze long period seismic waves generated by single force events such as the gigantic landslides associated with the 1980 eruption of mount st helens we refer to the method as centroid single force csf inversion as the result of the inversion we obtain the spatio temporal centroid and three components of a vector we call the csf vector which is the seismic point source representation of a landslide and whose direction is the opposite of the direction of sliding the sealer magnitude of the csf vector measures the overall size of the landslide and is given by mcsf md where m is the mass of the sliding object and d is the sliding distance we apply csf inversion to the long period surface waves generated by the 1980 mount st helens event the 1975 kalapana earthquake and the 1974 mantaro landslide using seismograms from the gdsn ida and hglp networks the csf solution for the st helens event is remarkably consistent with the actual geological observations and proves the efficacy of csf inversion the csf solution for the kalapana event does not fit the overall waveforms better than the cmt solution does however because the cmt solution does not explain the observed love wave radiation pattern it may be necessary to invoke a combination of both types of mechanism for this event although the geometry of the csf solution the direction of the force for the mantaro event is consistent with the actual landslide mcsf is about 5 times smaller than that expected from the mass and travel distance of the landslide estimated by geological observations this discrepancy may suggest either the relatively aseismic nature of this landslide or that the total volume of the slide was overestimated by analogy to single station cmt inversion single station csf inversion also appears to be stable and useful

an introduction to remobilization information from ore body geometry and experimental considerations abstract mobilization involves the translocation and concentration of originally dispersed metallic constituents remobilization is the translocation resulting in modified concentration and distribution of pre existing metalliferous concentrations mobilization and remobilization proceed by chemical liquid state mechanical solid state and mixed processes the paradox of remobilization is that the more complete the process the more difficult becomes substantiation regional metamorphic remobilization is commonly invoked to explain the morphology of supposedly once stratiform massive sulphides and their feeder and alteration systems analysis of the principal dimensions of stratiform massive sulphides in non metamorphic and regionally metamorphosed deposits shows that whereas comparative morphology may be a guide to remobilization it does not constitute proof similarly feeder and alteration morphology suggests that geometric analysis may be of value in establishing mechanical remobilization but the more complex alteration distributions which exist could well lead to misinterpretation in highly deformed terranes ore composition internal structure and zonation influence the ore s capacity to be remobilized mechanical remobilization requires rheological divergence between sulphides and their host rocks experimental deformation of dry sulphides shows that most common sulphides pass through the brittle ductile transition before entering the field of regional metamorphism but that the strength order of sulphides silicates and carbonates remains dynamic until all are undergoing steady state flow within this context experimental strength orders support galena weakest experimental considerations indicate that during diagenesis and early prograde metamorphism the brittle ductile transition will result in widely distributed micro and mesoscale mechanical remobilization nevertheless there is usually insufficient gross behavioural contrast to engender discordant macroscale remobilization possible exceptions particularly in relation to thrusting are outlined but we conclude that macroscale mechanical remobilization during the brittle ductile transition is an uncommon occurrence experimental data were also examined relative to subsequent prograde to peak metamorphism and strength contrasts during decaying and retrogressive metamorphism because the largest strength difference between sulphides and the host sequence is in the lower part of the 350 650 c metamorphic range we contend that macroscale mechanical remobilization is more probable during prograde metamorphism in the 350 500 c interval we similarly believe that macroscale mechanical remobilization is more likely during deformation accompanying retrogressive cooling in the range 500 350 c and we note that it may also result from deformation exploiting the brittle ductile contrasts between silicate and sulphide rocks during the water deficient non retrogressive metamorphic decay cycle chemical mobilization and remobilization require the dissolution of base metals by metamorphic fluids the compositions of hydrothermal low grade metamorphic fluids and their precipitates in active geothermal systems show that the fluids can dissolve transport and form concentrations of base and precious metals similarly fluid inclusion compositions from low to medium grade metamorphic rocks show that such fluids can dissolve a few ppm of base metals in both cases low salinities and low dissolved base metal contents raise doubts over whether such metamorphic fluids can form ore grade base metal concentrations we submit that they can metamorphogenesis is favoured by high initial base metal concentrations preferential dissolution of sulphides over silicates and fluid dominated metamorphism as found in a multiple pass fluid system preferential dissolution of sulphides and the need for high water rock ratios are supported by theoretical considerations experimental work on mafic felsic and sedimentary source rocks and field based studies in the context of mobilization the work strongly implies that prograde metamorphic devolatilization and a mobile fluid phase have substantial ore forming capability retrograde revolatilization does not remobilization is more complex although favoured by high initial metal concentrations dissolution is inhibited by the low permeability of homogeneous low silicate massive sulphides and the consequent peripheral fluid channeling it is conversely enhanced by fine grainsize in discordant fluid focussing retro grade shear zones in all cases for remobilization to form a new ore body both fluid flow and the precipitation process must be focussed and efficient

ground motion scaling in the marmara region turkey summary predictive relationships for the ground motion in the marmara region northwestern turkey are parametrized after regressing three component waveforms from regional earthquakes in the frequency range 0 4 15 0 hz and in the distance range 10 200 km the data set consists of 2400 three component recordings from 462 earthquakes recorded at 53 stations moment magnitudes m w range between 2 5 and 7 2 the largest event for which we have waveforms available m w 7 2 occurred in duzce on 1999 november 12 the aftershocks of that earthquake together with the aftershocks of the 1999 august 17 izmit event m w 7 4 are included in the dataset regressions are performed independently on fourier velocity spectra and on peak ground velocities for a large number of sampling frequencies a simple model is used to relate the logarithm of the measured ground motion to excitation site and propagation terms results obtained for peak velocities are used to define a piecewise continuous geometrical spreading function g r a frequency dependent q f and a distance dependent duration function the latter is used through random vibration theory rvt in order to predict time domain characteristics i e peak values of the ground motion the complete model obtained for the peak ground motion was used to match the results of the regressions on the fourier amplitudes fourier velocity spectra for the combined horizontal motion are best fit by a hinged quadrilinear geometrical spreading function for observations in the 10 200 km hypocentral distance ranges as a function of frequency f 100 f 1 0 hz r 1 0 for r 30 km r 0 6 for 30 100 km the frequency dependent crustal shearwave quality factor q f coefficient q f 180 f 0 45 the t 5 75 per cent duration window provides good agreement between observed and predicted peak values by modelling the behaviour of the small earthquakes at high frequency we also quantified a regional parameter 0 055 s spectral models with one single corner frequency brune and with two corner frequencies atkinson and silva fit the observed high frequency excitation levels equally well whereas the model by atkinson and silva fits the low frequency observations slightly better than brune s rvt is used to predict the absolute levels of ground shaking following boore s implementation of the stochastic ground motion model boore s smsim codes our regional empirical predictive relationships are compared to the ones adopted in several regions of the world from california to western united states

m b pn scale for the korean peninsula and site dependent pn amplification the korean peninsula is located in the far eastern eurasian plate margin where crustal structures vary laterally causing significant raypath dependent modulations of crustal phases the discriminative variations of crustal phases hinder application of conventional local magnitude scales in the continental margin the mantle lid phase is less affected by the crustal structures than the crustal phases providing a better constraint to magnitude estimation a regional body wave magnitude scale based on the mantle lid p wave pn mb pn is developed for regional events around the korean peninsula the mb pn scale is determined to be mb pn 0 380 0 299 log a 2 012 0 122 log d where a is the peak to peak pn amplitude in m and d is the epicentral distance in km the mb pn estimates of regional events around the korean peninsula are determined the mb pn estimates are compared with other available magnitude estimates mb lg ml the influence of structures beneath stations on pn amplification is investigated from inter station magnitude residuals a characteristic spatial variation of inter station magnitude residuals with strengths mostly between 6 and 6 but with maximum strengths of 10 is observed the inter station magnitude residuals appears to be correlated well with geological and seismic structures in the crust

shrimp u pb dating of the antucoya porphyry copper deposit new evidence for an early cretaceous porphyry related metallogenic epoch in the coastal cordillera of northern chile the antucoya porphyry copper deposit 300 mt at 0 45 total cu is one of the largest deposits of a poorly known early cretaceous porphyry belt in the coastal cordillera of northern chile it is related to a succession of granodioritic and tonalitic porphyritic stocks and dikes that were emplaced within jurassic andesitic rocks of the la negra formation immediately west of the n s trending sinistral strike slip atacama fault zone new zircon shrimp u pb data indicate that the porphyries of antucoya crystallized within the time span from 142 7 1 6 to 140 6 1 5 ma 2 and late unmineralized nw se trending dacite dikes with potassic alteration and internal deformation crystallized at 141 9 1 4 ma the antucoya porphyry copper system appears to be formed after a change of stress conditions along the magmatic arc from extensional in the late jurassic to transpressive during the early cretaceous and provides support for an early cretaceous metallogenic episode of porphyry type mineralization along the coastal cordillera of northern chile

genesis of the silvermines zinc lead barite deposit ireland fluid inclusion and stable isotope evidence the silvermines zinc lead barite deposit occurs adjacent to a major normal fault system within a sequence of mississippian tournaisian sandstones shales limestones and dolomites it comprises large synsedimentary syndiagenetic and smaller underlying epigenetic orebodies fluid inclusions within the epigenetic minerals are dominated by a simple liquid vapor type which in places contains one to five solid phases the commonest of which is calcite single phase liquid inclusions are commonest in barite single phase vapor and vapor liquid inclusions are occasionally found in quartz barite and carbonates although there is no indication of extensive boiling fluid inclusion salinities range from 8 to 28 equiv wt percent nacl with modes at 14 and 19 wt percent leachate studies show the fluids to have high sodium concentrations with lesser variable amounts of potassium and calcium and uniformly low magnesium concentrations k na 0 03 0 23 ca na 0 03 0 28 mg ca 0 1 0 67 fluid inclusions within synsedimentary syndiagenetic barite are highly saline indicating the possible presence of a brine pool at the site of ore deposition homogenization temperatures range from 50 degrees to 260 degrees c with most between 140 degrees and 220 degrees c there is a mode at 190 degrees c and a subsidiary group at 140 degrees c required pressure corrections are less than 5 degrees c if the pressure within the epigenetic ore zones was purely hydrostatic as is reasonable a minimum seawater depth of approximately 80 m is required to prevent boiling of some fluids for the whole deposit there is a negative correlation between homogenization temperature and salinity for quartz hosted inclusions which is interpreted as the involvement of two or possibly three fluids in the mineralizing process we suggest that high temperature 8 to 12 equiv wt percent nacl fluids mixed with lower temperature 18 to 22 equiv wt percent nacl fluids both within and below the ore zone during mineralization fluid inclusion waters have delta d values of 24 to 49 per mil for quartz 23 to 29 per mil for dolomite 41 to 55 per mil for barite 46 per mil for sphalerite and 58 per mil for galena the delta 18 o values of the mineralizing fluids calculated from mineral values range from 1 1 to 7 7 per mil for quartz and 1 8 to 5 7 per mil for dolomite these data best represent aqueous fluids that have equilibrated with the geosynclinal sequence and granites underlying the deposit they also suggest that local carboniferous surface and ground waters may have contained a deuterium depleted meteoric component the fluid inclusion evidence presented refutes a model involving the expulsion of carboniferous formation waters and indicates little if any involvement of magmatic waters the geologic geochemical and fluid inclusion evidence best fits a model involving the convection of carboniferous surface waters in the putative thick geosynclinal sequence and associated granitoids below the deposit with a contribution from lower paleozoic formation waters mineral precipitation resulted from fluid mixing in the ore zone with some contribution from carbonate wall rock reactions and possibly boiling

a tectonostratigraphic synthesis of the sub andean basins implications for the geotectonic segmentation of the andean belt the tectonic structural and depositional history of 19 sub andean foreland and eight southern caribbean basins has been synthesized and is summarized by regional geohistory charts these charts recapitulate the subsidence regimes recognized and have been used to evaluate correlations between genetically related stratigraphic sequences based on spatial and temporal changes in palaeo depositional setting the sub andean region can be subdivided longitudinally into several tectonostratigraphic domains the differential amount of subsidence between two adjacent tectonostratigraphic provinces or sub provinces relies on the presence of a transverse zone of structural accommodation the location of these transfer zones correlates with a number of known and several newly identified zones of intracontinental deformation combined with changes in the structural geometry of the andean fold and thrust belt and the relative dominance of basement fault systems along the length of the andean foreland it is suggested that the andean belt can be separated into five tectonic domains which are themselves bounded by transverse structural accommodation zones representing the multiphase reactivation of pre existing basement fault systems the influence of these broad zones of transcontinental deformation is most apparent during the triassic jurassic period suggesting that they were intimately associated with accommodating intraplate stresses during the breakup of the gondwana supercontinent

paleogene clockwise tectonic rotations in the forearc of central andes antofagasta region northern chile 1 for the central valley of northern chile antofagasta region a paleomagnetic analysis of data from 108 sites mainly in mesozoic and paleogene volcanic rocks has yielded stable remanent magnetization directions for 86 sites from these data we infer clockwise tectonic rotations of up to 65 within the forearc domain of the central andes the apparent relationship between tectonic rotations and structural trends suggests that rotations occurred mainly during the incaic orogenic event of eocene early oligocene age a few paleomagnetic results obtained in neogene rocks do not show evidence of clockwise rotations hence the development of the bolivian orocline during late neogene time cannot be explained by simple bending of the whole margin these results demonstrate that tectonic rotations within the forearc and pre cordillera are key elements of early andean deformation which should be taken into account by kinematic models of mountain building in the central andes

remobilisation of base metals and gold by variscan metamorphic fluids in the south iberian pyrite belt evidence from the tharsis vms deposit the tharsis massive sulphide deposit one of the major vms type deposits in the iberian pyrite belt ipb was severely deformed by the variscan tectono thermal events the question of whether or not these events affected the metal distribution in the deposit has been addressed by simultaneously studying the mineral parageneses tharsis stockwork and the fluid circulation at local and regional scales the results are 1 the early paragenesis in the stockwork q1 quartz pyrite chlorite phengitefcobaltitefankerite was strongly overprinted by a late post kinematic mineral deposition including new quartz veins q3 quartz and base metal sulphides chalcopyrite sphalerite bi and te minerals pyrite and galena and gold 2 at a regional scale fluids accompanying the peak metamorphism conditions ca 300 mpa ca 300 jc were of c o h n nacl type co2 dominated with ch4 and n2 and are considered to be metamorphic on the basis of microthermometry and geochemistry the late to post kinematic evolution retrograde stage was characterised by a pressure drop down to 40 mpa lithostatic to hydrostatic transition and a heat input leading to temperatures z430 jc then decreasing to temperature around 170 jc fluids of the retrograde type exhibit both dilution of the c o h n nacl fluid by a low salinity meteoric water and progressive loss of volatile components 3 fluids of the retrograde type pervasively percolated through the tharsis stockwork and were responsible for the strong mineral overprint on the early deformed paragenesis all the measurable fluid inclusions f i record these late fluids there are primary fluid inclusions in q1 but they are systematically imploded due to the external overpressure generated by the variscan tectonic events although base metal distribution in the stockwork is basically the result of the

re os isotope systematics for the lince estefania deposit constraints on the timing and source of copper mineralization in a stratabound copper deposit coastal cordillera of northern chile the lince estefania stratabound copper deposit in the michilla district is one of the most important deposits in the coastal cordillera of northern chile and is one of the most representative of this type of deposit chalcocite and bornite characterize the main stage of hypogene copper sulfide mineralization rhenium and osmium isotopes are used here to constrain the age of hypogene mineralization and the source of osmium contained in these ore minerals a re os isochron yielded an age of 160 16 ma 2 with an associated initial 187os 188os ratio of 1 06 0 09 mean square of weighted deviates 1 8 this age is consistent with available geochronological data from volcanic rocks that host the mineralization and associated alteration phases the high initial 187os 188os ratio indicates a lower crustal component for the source of os and by inference the cu sulfides that contain this os late hematite occurs as an isolated phase or more commonly is associated with the chalcocite bornite and supergene chalcocite covellite associations analyses performed on pure hematite indicate a disturbance of the re os system and hence this mineral phase is not useful as a re os geochronometer

source transport and fate of rhenium selenium molybdenum arsenic and copper in groundwater associated with porphyry cu deposits atacama desert chile we collected groundwaters in and around a large 313 mt at 1 08 cu and 0 3 cutoff undisturbed porphyry copper deposit spence in the hyperarid atacama desert of northern chile which is buried beneath 30 180 m of miocene piedmont gravels groundwaters within and down flow of the spence deposit have elevated se up to 800 g l re up to 31 g l mo up to 475 g l and as up to 278 g l concentrations compared to up flow waters interpreted to represent regional groundwater flow in contrast cu is only elevated up to 2036 g l in groundwaters recovered from within the deposit cu concentrations are low down gradient of the deposit the differential behavior of the metals metalloids occurs because the former group dissolves as anions enhancing their mobility whereas the base metals dissolve as cations and are lost from solution most likely through adsorption to clay surface exchange sites and through formation of secondary copper chlorides carbonates and oxides most groundwaters within and down flow of the deposit have eh ph values around the feii feiii phase boundary limiting the impact of fe oxyhydroxides on oxyanions mobility se re mo and as are all mobile with filtered unfiltered samples 1 to the limit of sampling 2 km down gradient from the deposit the increase in ore related metals metalloids and sulfate and decrease in sulfate s isotope ratios from values similar to regional salars 4 to 8 34scdt to lower values closer to hypogene sulfides 1 to 4 34scdt is consistent with active water rock reactions between saline groundwaters and the spence deposit it is likely that hypogene and or supergene sulfides are being oxidized under the present groundwater conditions and mineral saturation calculations suggest that secondary copper minerals antlerite atacamite malachite may also be actively forming suggesting that supergene and exotic copper mineralization is possible even under the present hyperarid climate of the atacama desert

a break in self similarity in the lunigiana garfagnana region northern apennines 1 in this study stable source parameters are determined for small earthquakes in the lunigiana garfagnana region using an empirical methodology based on coda envelope measurements that are significantly less affected by the source radiation pattern directivity and heterogeneous path variation than traditional direct wave measurements we find evidence that the scaled energy er m0 increases with moment and source spectra are not self similar for 3 0 mw 4 6 the calibration procedure allows for an independent check of three important features 1 that the empirical path corrections provide consistent amplitude measurements for the same event at different stations distances and azimuths 2 that the long period levels of the source spectra are consistent with independent m0 derived from long period waveform modeling 3 that small event spectra are flat below a conservative estimate of the corner frequency and thereby effectively accounting for near site attenuation

estimates of attenuation structure in the cinarcik basin of the marmara sea northwest turkey abstract the attenuation structure 1 q in the sediments of the cinarcik basin of the marmara sea was estimated from the raw shot data of a multi channel seismic reflection experiment using a wavelet modeling technique the estimated attenuation called the effective q is the sum of the inelastic absorption and the apparent attenuation the estimated effective q values along the north south trending seismic profiles are interpreted together with their time migrated seismic sections there are several local minima in the boundary separating the low

source parameters for 1999 north anatolian fault zone aftershocks we develop a data set of aftershock recordings of the 1999 m 7 4 izmit and m 7 2 duzce turkey earthquakes to study their source parameters we combined seismograms from 44 stations maintained by several sources organizations to obtain a unified data set of events 2 1 mw 5 5 we calculate source parameters of these small earthquakes by two methods that use different techniques to address the difficulty in obtaining source spectra for small earthquakes subject to interference from site response one method program netmoment nm hutchings 2004 uses spectra of direct s waves in a simultaneous inversion of local high frequency network data to estimate seismic moment source corner frequency f c site attenuation k and whole path q this approach takes advantage of the source commonality in all recordings for a particular earthquake by fitting a common brune source spectrum to the data with a and individual k the second approach mayeda et al 2003 uses the coda method cm to obtain nonmodel based source spectra and moment estimates from selected broadband recording sites we found that both methods do well for events that allow the comparison with seismic moment estimates derived from waveform modeling also source spectra obtained from the two methods are very closely matched for most of the events they have in common we use an f test to examine the trade off between k and f c picks identified by the direct s wave method about half of the events could be constrained to have less than a 50 average uncertainty in f c and k we used these source spectra solutions to calculate energy and apparent stress and compare these to estimates from the selected good quality source spectra from cm both studies have values mutually consistent and show a similar increase in apparent stress with increasing moment this result has added merit due to the independent approaches to calculate apparent stress we conclude that both methods are at least partially validated by our study and they both have usefulness for different circumstances of recording local small earthquakes cm would work well in studies for which there is a broad magnitude range of events and nm works well for local events recorded by band limited recorders

the precordilleran fault system of chuquicamata northern chile evidence for reversals along arc parallel strike slip faults abstract the chilean precordillera situated between the longitudinal valley and the western cordillera of northern chile was the site of the andean magmatic arc from the late cretaceous to the eocene oligocene boundary magmatism came to an end during the incaic tectonic phase 38 ma which caused arc normal shortening and the development of longitudinal dextral strike slip faults precordilleran fault system this magmatic arc tectonism is also related to the formation of the chuqicamata porphyry copper ore deposit as well as of other important deposits of this type in the precordillera structural investigations in and around the chuqicamata open pit mine have shown that wrench tectonics determined the kinematics of the area the n s striking west fissure which separates a 35 ma old non mineralised pluton to the west from a central late paleozoic basement ridge containing the mineralization became a sinistral fault along with other parallel faults in the area the central part is separated from similar paleozoic rocks to the east by the messabi este fault and a narrow faulted and sheared syncline of mesozoic cenozoic sediments this fault bears structures indicating dextral movements which probably are of an age that is similar to the mylonites 34 8 ma in the western pluton the dextral movements preceded the sinistral shear thus the fault system of chuqicamata displays a reversal of arc parallel shear movements according to the orientation of quartz veins in the mineralized body it is presumed that the sense of displacement of these strike slip motions reversed when mineralization started at about 32 ma during this time the stress field must have changed fundamentally the incaic phase dextral transpression is supposed to have been induced by the oblique vector of plate motion the following sinistral transtension corresponds to a time of reduced convergence rate and possibly reduced plate coupling as however the vector of plate motion remained unchanged during that time oblique subduction cannot be used as an argument for arc parallel sinistral shear movements

an application of the coda methodology for moment rate spectra using broadband stations in turkey a recently developed coda magnitude methodology was applied to selected broadband stations in turkey for the purpose of testing the coda method in a large laterally complex region as found in other albeit smaller regions coda envelope amplitude measurements are significantly less variable than distance corrected direct wave measurements i e l sub g and surface waves by roughly a factor 3 to 4 despite strong lateral crustal heterogeneity in turkey they found that the region could be adequately modeled assuming a simple 1 d radially symmetric path correction after calibrating the stations isp iskb and malt for local and regional distances single station moment magnitude estimates m sub w derived from the coda spectra were in excellent agreement with those determined from multistation waveform modeling inversions exhibiting a data standard deviation of 0 17 though the calibration was validated using large events the results of the calibration will extend m sub w estimates to significantly smaller events which could not otherwise be waveform modeled the successful application of the method is remarkable considering the significant lateral complexity in turkey and the simple assumptions used in the coda method

geometry and genesis of feeder zones of massive sulphide deposits constraints from the rio tinto ore deposit spain vein related data have been collected around the giant rio tinto orebody in southern spain within the root zones of the massive sulphide deposits here we report the main results of this study concerning the geometry of the stockwork and the conditions of formation although field and thin section studies have shown that a wide range of vein configurations exist from micro cracks fluid inclusion planes to large paleo flow channels two groups seem to dominate the first corresponds to small constricted micro cracks and capillary flow channels now mainly filled with quartz whereas the veins of the second group have large widths are continuous over several meters and are filled with quartz and sulphides most are tension veins and only very few quartz tends to post date the quartz dominated veins quartz pyrite the vein thickness and spacing distribution is modal rather than logarithmic and their densities are not fractal but are characterized by a poisson distribution from the immediate sub surface zone to more than 100 m below the base of the massive sulphide deposits most hydrothermal quartz sulphide stockwork veins are sub parallel to the base of the massive sulphide deposit the assumption that the base of this deposit corresponds to a paleo horizontal plane implies that most veins were sub horizontal this is particularly evident for small veins but the larger ones can be strongly oblique to the base of the deposit the hydrothermal fluids that generated the massive sulphide deposits and underlying stockworks were very saline and probably underwent sub or super critical phase separation in the root zones of the system this phase separation was the probable mechanism producing the periodic over pressures of at least 20 mpa that were necessary to generate the sub horizontal veins of the stockworks

strong ground motion during the largest aftershock mw 5 8 of the 1999 izmit earthquake turkey abstract we present a preliminary study of strong ground motion during the largest aftershock mw 5 8 of the 1999 izmit earthquake mw 7 4 turkey at 11 55 on 13 september 1999 the peak ground acceleration observed near the epicentre of this aftershock was in agreement with that predicted by standard empirical prediction equations its spectral source parameters of the largest aftershock are also typical for a mw 5 8 earthquake at greater epicentral distances there is an order of magnitude in scatter in peak ground acceleration values for this aftershock which is attributed to site effects the presence of thick layers of low velocity sediments caused significant amplification of s waves in the avcilar district of istanbul at frequencies of 1 hz explaining the observed concentration of damage there as a result of the izmit mainshock

effects of greenschist facies metamorphism and related deformation on the mobrun massive sulfide deposit quebec canada the mobrun zn cu ag au deposit in the noranda mining camp is hosted by archean mafic and felsic submarine volcanic rocks the deposit comprises three massive sulfide complexes the main and satellite lenses near surface and the 1100 orebody at depth the rocks have been subjected to lower greenschist facies metamorphism and related deformation which resulted in changes in ore textures development of shear zones and veins systems remobilization of gold and formation of a new mineral electrum within the orebodies both mechanical and chemical processes operated to produce secondary textures and structures resulting from brittle deformation ductile deformation and annealing the specific deformation mechanisms include brittle failure and cataclastic flow dislocation glide dislocation creep and solution precipitation creep the main and satellite lenses are characterized by excellent preservation of primary sulfides deposited from and reworked by synvolcanic hydrothermal fluids these orebodies were affected to a limited degree by mechanical processes of deformation in contrast the 1100 orebody is characterized by a higher degree of development of textures and structures related to metamorphism and deformation especially those formed by chemical processes the differences may be due to the greater depth of the 1100 orebody relative to the other lenses as regional metamorphic isograds are subhorizontal and more extensive interaction between metamorphic fluids and the 1100 lens

source parameters of the june 29 1992 little skull mountain earthquake from complete regional waveforms at a single station the june 29 1992 m sub b 5 5 little skull mountain earthquake occurred 20 km southeast of yucca mountain within the boundaries of the nevada test site this event was recorded at a very broadband station located about 310 km to the east at kanab utah both body and surface waves from this single station were used in a grid search technique for the best fitting double couple moment tensor the technique minimizes the misfit between reflectivity generated complete synthetic seismograms and the three component displacement data via a search over the strike dip and rake of the source in the passband of 50 15 s period the grid search results in a well defined nearly pure normal mechanism with a strike of 35 degrees a dip of 54 degrees a rake of minus 87 degrees and a seismic moment of 4 1 x 10 sup 17 n m applying the same technique to the large aftershock on july 5 1992 the authors obtain a somewhat less well defined minimum with a strike of 358 degrees a dip of 36 degrees a rake of minus 177 degrees and a moment of 4 3 x 10 sup 15 n m the minimum compression axes of these mechanisms are consistent with northwest southeast extension in the basin and range 14more refs 7 figs less

composition of groundwaters associated with porphyry cu deposits atacama desert chile elemental and isotopic constraints on water sources and water rock reactions abstract groundwaters were collected around the spence porphyry copper deposit atacama desert northern chile to study water porphyry copper ore bodies interaction and test hypotheses regarding transport of metals through thick overburden leading to the formation of soil geochemical anomalies the deposit contains 400 mt of 1 cu and is completely buried by piedmont gravels of miocene age groundwaters were recovered from the eastern up hydraulic gradient upflow margin of the spence deposit from within the deposit and for two kilometers down flow from the deposit water table depths decrease from 90 m at the upflow margin to 30 m 1 5 km down flow groundwaters at the spence deposit are compositionally variable with those upflow of the deposit characterized by relatively low salinities 900 7000 mg l and na so42 type compositions these waters have compositions and stable isotope values similar to regional groundwaters recovered elsewhere in the atacama desert of northern chile in contrast groundwaters recovered within and down flow of the deposit range in salinity from 10 000 to 55 000 mg l one groundwater at 145 000 mg l and are dominantly na cl type waters dissolved sulfate values are however elevated compared to upflow waters and 34scdt decreases into the deposit from 4 to 2 consistent with increasing influence of sulfur derived from oxidation of sulfide minerals within the deposit the increase in salinity and conservative tracers cl br li and na and the relationship between oxygen and hydrogen isotopes suggests that in addition to water rock reactions within the deposit most of the compositional variation can be explained by groundwater mixing with perhaps a minor role for evaporation a groundwater mixing scenario implies a deeper more saline groundwater source mixing with the less saline regional groundwater flow system flow of deeper more saline groundwater along pre existing structures has important implications for geochemical exploration and metal transport models

explanation for many of the unusual features of the massive sulfide deposits of the iberian pyrite belt newly published fluid inclusion data from quartz in stockwork veins beneath seven massive sulfide lenses in the iberian pyrite belt suggest that the lenses were formed from fluids that on reaching the sea reversed buoyancy and ponded in basins sulfides quenched in the resulting brine pool would have settled to form a sulfide mud this process provides a relatively efficient trapping mechanism for metal in the fluids and effectively excludes ambient seawater accounting for the deposits tending to have the characteristics of large size sheet like form absence of relict chimney structures and a mineral content characterized by pyrite arsenopyrite and absence or scarcity of barite marcasite and fe oxides if total s was less than total metals in the stockwork fluids some or all of the more soluble zn and pb could have been swept from the basin at the overflow accounting for the variable but generally low zn and pb contents of the ores the lack of sedimentary source for the high salinities implicates magmatic intrusions possibly similar to those related to sn w mineralization

a sulphur isotopic study of the bleikvassli zn pb cu deposit nordland northern norway the bleikvassli zn pb cu deposit occurs in the uppermost allochthon in the caledonides of northern norway the orebody is enclosed in amphibolite facies schists and gneisses underlain by amphibolites and it has been classified as a sediment hosted massive sulphide sedex deposit the stratiform ore is dominantly pyritic with a basal layer of pyrrhotitic ore sulphide veins occur in the footwall the orebody generally has a limited range of 34s from 0 3 to 4 5 x 2 4 1 2 1 n 26 the lowest 34s values 0 3 2 3 were found in sulphide veins in the footwall and vent proximal stratiform ore more distal pyritic zn pb ore has heavier average 34s values up to 4 5 the ore sulphides were deposited from a hydrothermal solution with 34s about 2 perhaps with the incorporation of a minor portion of sulphide from the ambient seawater the hydrothermal solution probably acquired most of its sulphide from the underlying mixed lithology notably basaltic rocks sulphide produced by thermochemical reduction of seawater in the deep conduit system may also have been incorporated bacteriogenic sulphide is not likely as a major source of ore sulphur in the massive ore sulphide incorporated in distal pyrite which have 34s from 12 to 10 could have formed either by oxidation of the hydrothermal sulphide or by bacterial reduction of seawater sulphate in the depositional environment exchange of sulphur isotopes probably took place only on a localized scale during caledonian metamorphism the bulk sulphur isotopic composition of the ore being preserved in a hand specimen scale

the aftershock signature of supershear earthquakes recent studies show that earthquake faults may rupture at speeds exceeding the shear wave velocity of rocks this supershear rupture produces in the ground a seismic shock wave similar to the sonic boom produced by a supersonic airplane this shock wave may increase the destruction caused by the earthquake we report that supershear earthquakes are characterized by a specific pattern of aftershocks the fault plane itself is remarkably quiet whereas aftershocks cluster off the fault on secondary structures that are activated by the supershear rupture the post earthquake quiescence of the fault shows that friction is relatively uniform over supershear segments whereas the activation of off fault structures is explained by the shock wave radiation which produces high stresses over a wide zone surrounding the fault

estimating absolute site effects the authors use previously determined direct wave attenuation functions as well as stable coda derived source excitation spectra to isolate the absolute s wave site effect for the horizontal and vertical components of weak ground motion they used selected stations in the seismic network of the eastern alps and find the following 1 all hard rock sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0 5 and 12 hz the available bandwidth on both the horizontal and vertical components 2 hard rock site transfer functions showed large variability at high frequency 3 vertical motion site transfer functions show strong frequency dependence and 4 h v spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions 5 traditional relative site terms obtained by using reference rock sites can be misleading in inferring the behaviors of true site transfer functions since most rock sites have non flat responses due to shallow heterogeneities resulting from varying degrees of weathering they also use their stable source spectra to estimate total radiated seismic energy and compare against previous results they find that the earthquakes in this region exhibit non constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes to correct the vertical and horizontal s wave spectra for attenuation they used detailed regional attenuation functions derived by malagnini et al 2002 who determined frequency dependent geometrical spreading and q for the region these corrections account for the gross path effects i e all distance dependent effects although the source and site effects are still present in the distance corrected spectra the main goal of this study is to isolate the absolute site effect as a function of frequency by removing the source spectrum moment rate spectrum from the distance corrected s wave spectra typically removing the s wave source spectrum is difficult because of inadequate corrections for the source radiation pattern directivity and random interference in addition to complexities near the source 2 d and 3 d structure beneath the recording site will result in an azimuth dependent site effect since the direct wave only samples a narrow range in take off and back azimuth angles multi station averaging is needed to minimize the inherent scatter to minimize these complicating effects they apply the coda methodology outlined by mayeda et al 2003 to obtain stable moment rate spectra this methodology provides source amplitude and derived source spectra that are a factor of 3 to 4 times more stable than those derived from direct waves since the coda is commonly thought of as scattered energy that samples all ray parameters and back azimuths it is not very sensitive to the source radiation pattern and 3 d structure this property makes it an excellent choice for use in obtaining average properties of the source site and path effects in a region due to the characteristics of the techniques used in this study all the inverted quantities are azimuthally averaged since the aximuthal information is lost in the processing

atacamite formation by deep saline waters in copper deposits from the atacama desert chile evidence from fluid inclusions groundwater geochemistry tem and 36 cl data the presence of large amounts of atacamite in oxide zones from ore deposits in the atacama desert of northern chile requires saline solutions for its formation and hyperarid climate conditions for its preservation we investigated the nature and origin of atacamite forming solutions by means of coupling groundwater geochemical analyses with fluid inclusion data high resolution mineralogical observations and chlorine 36 36cl data in atacamite from the mantos blancos and spence cu deposits in both deposits the salinities of fluid inclusions in atacamite are comparable to those measured in saline groundwaters sampled from drill holes the average salinity of fluid inclusions in atacamite for the mantos blancos and spence deposits 7 9 and 2 3 wt nacleq respectively are strongly correlated to the salinities at which gypsum supersaturates from groundwaters in both deposits total dissolved solids 5 9 and 1 3 wt nacleq respectively this correlation is confirmed by transmission electron microscopy observations of atacamite bearing samples revealing an intimate association between atacamite and gypsum that can be traced down to the nanometer scale 36cl data in atacamite provide new lines of evidence concerning the origin and age of the saline waters that formed atacamite in various stratabound and porphyry cu deposits from the atacama desert all atacamite samples show very low 36cl to cl ratios 11 10 15 to 28 10 15 at at 1 comparable to previously reported 36cl to cl ratios of deep formation waters and old groundwaters in addition 36cl to cl ratios in atacamite correlate with u and th concentration in the host rocks but are independent from distance to the ocean this trend supports an interpretation of the low 36cl to cl ratios in atacamite as representing subsurface production of fissiogenic 36cl in secular equilibrium with the solutions involved in atacamite formation therefore 36cl in atacamite strongly suggest that the chlorine in saline waters related to atacamite formation is old 1 5 ma but that atacamite formation occurred more recently 1 5 ma than suggested in previous interpretations our data provide new constraints on the origin of atacamite in cu deposits from the atacama desert and support the recent notion that the formation of atacamite in hyperarid climates such as the atacama desert is an ongoing process that has occurred intermittently since the onset of hyperaridity

a reappraisal of the structure of the spanish segment of the iberian pyrite belt the major structural features of the iberian pyrite belt are described in terms of geometry deformation mechanisms scale timing kinematics and the mutual relationships among the various architectural elements the result of such an analysis allows this zone to be considered as a s verging thin skinned fold and thrust belt propagating southwards over a mid crustal basal detachment this was the response in the footwall of the suture to the major phase of hercynian oblique collision between the south portuguese plate and the ossa morena zone of the iberian autochthon this thin skinned event inverted a previous extensional structure acquired during the initial stages of the collisional process and intimately linked to the formation of the ore deposits that make this region a world class metallogenic province

the mattagami lake mine archean zn cu sulfide deposit quebec hydrothermal coprecipitation of talc and sulfides in a sea floor brine pool evidence from geochemistry 18 o 16 o and mineral chemistry orebody 2 is 21 million metric tons grading 10 5 percent zn 0 17 percent cu and 0 014 oz au plus 1 15 oz ag per short ton quartz in the orebody has a delta 18 o of 10 to 11 9 per mil or approximately 2 per mil heavier than footwall quartz signifying precipitation temperatures 250 degrees to 280 degrees c this is corroborated by filling temperatures of primary fluid inclusions within gangue quartz t f 240 degrees 270 degrees c both isotopic and fluid inclusion temperatures signify a broad thermal zonation from approximately 270 degrees c at the base to approximately 240 degrees c at the top of the orebody minimum water depths of 300 m are indicated from nonboiling hydrothermal fluids of 3 to 5 weight percent nacl equivalent at approximately 250 degrees c a approximately 50 degrees c cooling of fluids during passage from the footwall to a suggested sea floor brine pool above the ore zone may have been induced by turbulent mixing of approximately 20 percent pristine archean marine bottom water at approximately 70 degrees c downward into the brine pool chert in the overlying key tuffite has delta 18 o of 10 to 12 per mil probably representing equilibrium precipitation from brine pool fluids at 200 degrees to 250 degrees c spreading laterally across the sea floor in a gravitationally stable boundary layer modified journal abstract

fluid inclusion petrography abstract a procedure of fluid inclusion studies is proposed with emphasis on the criteria of selecting fluid inclusions for detailed microthermometry and spectroscopic analysis an overview of descriptive and genetic classifications of fluid inclusions in single crystals and in massive rocks is given with the intention of further differentiating the commonly used terms primary and secondary fluid inclusions some principles of fluid inclusion modification are explained cathodoluminescence cl studies of quartz with the optical high power cl microscope and the electron microprobe provided with a cl detector are an important help in fluid petrography cl textures are subdivided in primary growth textures and a wide variety of secondary microtextures which are in part induced by fluid inclusions the latter is grouped in textures indicative of local lower crystal order increasing defect structures and microtextures indicative of local quartz healing reduction of the defect structures microtextures showing the genetic relationship between fluid inclusions and the host mineral provide information about the possible post entrapment changes of fluid inclusions and therewith testify their geological relevance

flow mechanisms in sulphide minerals abstract the sulphide minerals as a group display a diverse range in strength and mechanical behaviour in crustal environments deforming by a range of different flow mechanisms which can lead to the development of characteristic microfabrics the dependence of creep rate on imposed parameters such as stress difference temperature grainsize effective confining pressure and the activities of various components varies for each type of flow mechanism for particular phases changes in the dominant operative flow mechanism may occur in response to changes in the imposed environmental variables at high applied stress differences low effective confining pressures and low temperatures brittle failure and cataclastic flow are significant deformation mechanisms in some sulphide minerals at elevated confining pressures brittle failure can be suppressed and low temperature plasticity processes involving dislocation glide and or deformation twinning may operate with decreasing applied stress difference and at elevated temperatures even though strain may be accommodated largely by dislocation glide deformation may be rate controlled by recovery processes and dynamic recrystallization may be significant in influencing microfabric development the operation of dislocation glide processes leads to the development of crystallographic preferred orientations at very low applied stress difference various grainsize dependent atomic transfer deformation mechanisms may be important in many fluid present low to medium grade metamorphic environments solution precipitation creep processes are active in the deformation of some sulphide phases in fluid absent situations grain boundary diffusion creep may be significant at higher temperatures where intragranular diffusion is relatively rapid lattice diffusion creep processes are expected to be a major deformation mechanism in fine grained sulphide assemblages at elevated temperatures grain boundary sliding may be an important deformation mechanism

exploring for deeply covered mineral deposits formation of geochemical anomalies in northern chile by earthquake induced surface flooding of mineralized groundwaters northern chile is a major producer of copper from porphyry deposits most ores worked to date were exposed near the surface exploration is now focused on deposits along a basement unconformity buried under piedmont gravels deposited by ca 10 ma two recent discoveries the spence and gaby sur deposits are covered by gravel soils above these deposits have anomalies for elements present in saline mineralized groundwaters the anomalies occur above fracture zones in the gravels believed to represent the upward propagation of basement faults that guided emplacement of the porphyries we propose that during earthquakes in this seismically active region there was pumping of saline basement waters up the faults and fracture zones entraining mineralized groundwaters from the deposits after surface flooding and evaporation elements were redistributed by infrequent rains sampling shows that surface active cations such as cu 2 1 were adsorbed and retained in the top few centimeters of soil whereas nacl and porphyry indicator elements that dissolve as anions se re and as are not adsorbed and are removed to 40 cm depth given the 10 m y interval since the gravels were deposited and the hyperarid climate of the atacama desert anomalies may have formed by repeated episodes of seismically induced flooding company geochemical surveys show that such features are numerous in northern chile producing linear zones of saline soils plus other constituents of local groundwaters e g b and i where faults controlling these features intersect mineralization elements specific to the mineralization are also present saline zones may be outlined in the field by measuring the conductivity of soil plus water slurries sampling for full geochemical analyses can be limited to areas so defined anomalies may be generated along fault lines in other seismically active wetter climates but only for elements that are adsorbed on soil minerals although the context of the study is mineral exploration the process may be relevant to the formation of geochemical features of environmental interest above major faults

characterization of aftershock fault plane orientations of the 1999 izmit turkey earthquake using high resolution aftershock locations 1 joint inversion for hypocentral parameters and the velocity field is nowadays a state of the art tool to obtain high resolution images of seismically active regions in this study we focus on the location accuracy of aftershocks of the 1999 mw 7 4 izmit nw turkey earthquake we obtained a new velocity model for the region and depicted its improvement on absolute locations in terms of uncertainty and misfit two well developed aftershock clusters located in the akyazi area and karadere duzce region were analyzed in detail based on a waveform cross correlation approach that allowed improving the location accuracy by a factor of 6 relocation results reveal that hypocenters form narrow planes of activity that can be correlated with focal mechanisms of the larger aftershocks as well as nearby clouds of activity with no internal structure down to the resolved scale of 300 m

moment magnitudes of local regional events from 1d coda calibrations in the broader middle east region abstract reliable moment magnitude estimates for seismic events in the middle east region can be difficult to obtain due to the uneven distribution of stations the complex tectonic structure and regions of high attenuation in this study we take advantage of the many new broadband seismic stations that have become available through improved national networks and numerous temporary deployments we make coda envelope amplitude measurements for 2247 events recorded by 68 stations over 13 narrow frequency bands ranging between 0 03 and 8 hz the absolute scaling of these spectra was calculated based on independent waveform modeling solutions of the moment magnitudes for a subset of these events to avoid circularity using our 1d path calibrations we determined coda based magnitudes for a majority of the events we obtain fairly good agreement with waveform modeled seismic moments for the larger events m w 4 5 at low frequencies 0 7 hz because of unaccounted 2d path effects as well as mixing of both sn coda and lg coda which have different attenuation behavior this scatter leads to increased variance in the magnitudes estimated for smaller events in which low frequency amplitudes are below the noise levels and the higher frequencies are the only signals available we quantify the expected variance in coda envelope amplitudes as a function of frequency using interstation scatter as our metric the net results of this study provide thousands of new 1d coda magnitude estimates for events in the broad region as well as the necessary initial starting model for use in a new related 2d coda study pasyanos et al 2016 online material table of site terms and moment magnitudes

fluid inclusions of the massive sulfide deposits in the skellefte district sweden abstract the massive sulfide deposits of the skellefte district are located in northern sweden the ores are hosted by precambrian submarine volcanics and sedimentary rocks both rocks and ores have been deformed and metamorphosed mainly to greenschist facies aqueous two phase liquid vapor primary inclusions in sphalerite quartz and calcite from six mines ravliden kristineberg ostra hogkulla bjurtrask renstrom and langdal indicate that the sulfide ores were formed under non boiling conditions during two major stages of hydrothermal activity at temperatures of 210 and 295 c respectively the ore forming fluids were ca na cl bearing hydrothermal solutions with a salt content of 4 2 eq wt nacl later recrystallization of the ores occurred at lower temperatures involving solutions with higher salinities

the mantos blancos copper deposit an upper jurassic breccia style hydrothermal system in the coastal range of northern chile the upper jurassic mantos blancos copper deposit 500 mt at 1 0 cu located in the coastal range of northern chile displays two superimposed hydrothermal events an older phyllic alteration probably related to felsic magmatic hydrothermal brecciation at 155 ma and younger 141 142 ma potassic propylitic and sodic alterations coeval with dioritic and granodioritic stocks and sills and dioritic dikes main ore formation is genetically related to the second hydrothermal event and consists of hydrothermal breccias disseminations and stockwork style mineralization associated with sodic alteration hypogene sulfide assemblages show distinctive vertical and lateral zoning centered on magmatic and hydrothermal breccia bodies which constitute the feeders to mineralization a barren pyrite root zone is overlain by pyrite chalcopyrite and followed upwards and laterally by chalcopyrite digenite or chalcopyrite bornite the assemblage digenite supergene chalcocite characterizes the central portions of high grade mineralization in the breccia bodies fluid inclusions show evidence of boiling during the potassic and sodic alteration events which occurred at temperatures around 450 460 c and 350 410 c and salinities between 3 53 and 13 45 wt nacl eq respectively the hydrothermal events occurred during episodic decompression due to fluid overpressuring hydrofracturing and sharp changes from lithostatic to hydrostatic conditions sulfur isotope results of hypogene sulfide minerals fall in a narrow range around 0 per mil suggesting a dominance of magmatic sulfur carbon and oxygen isotopic data of calcites from propylitic alteration suggest a mantle derived carbon and oxygen isotope fractionation due to low temperature alteration

aeromagnetic signature of porphyry copper systems in northern chile and its geologic implications the compilation of a large aeromagnetic high resolution dataset acquired for base metals exploration in northern chile between lat 19 45 s and 27 15 s revealed a pattern of transorogenic regional magnetic anomalies these anomalies occur as generally east west stripes of negative residual magnetic intensity of more than 100 nanotesla nt they have an east west extension of some tens of kilometers and a north south width of some 5 to 10 km some of them can be observed continuously from the coast to the volcanic belt their residual intensity is typically more than 100 nt they also show a loose north south spacing it is observed that all known porphyry copper deposits of the investigated segment are spatially related to these transverse magnetic anomalies we propose that the transverse magnetic anomalies are the magnetic response to the loci of emplacement of intrusive bodies of batholithic size along paths of the advancing magmatic front of the active continental margin the occurrence of several important porphyry copper deposits grouped in clusters within a district is explained as being related to a common parental intrusive complex which is geophysically signaled by a corresponding transverse magnetic anomaly a possible implication of the observed relationship between porphyry copper deposits and transverse magnetic anomalies is the quasideterministic restriction of porphyry copper deposits to certain orogen transverse loci necessary condition and the corresponding consequences for future exploration strategies

the filon norte orebody tharsis iberian pyrite belt a proximal low temperature shale hosted massive sulphide in a thin skinned tectonic belt the filon norte orebody tharsis iberian pyrite belt is one of the largest pyrite rich massive sulphide deposits of the world the present structure of the mineralization consists of an internally complex low angle north dipping thrust system of variscan age there are three major tectonic units separated by thick fault zones each unit with its own lithologic and hydrothermal features they are internally organized in a hinterland dipping duplex sequence with high angle horses of competent rocks igneous and detritic rocks and massive sulphides bounded by phyllonites the mineralization is within the lower unit and is composed of several stacked sheets of massive sulphides and shales hosting a stockwork zone with no obvious zonation the intermediate unit is made up of pervasively ankeritized shales and basalts spilites here hydrothermal breccias are abundant the upper unit is the less hydrothermally altered one and consists of silicified dacites and a diabase sill the tectonic reconstruction suggests that the sequence is inverted and the altered igneous rocks were originally below the orebody carbon oxygen and sulphur isotopes in the massive sulphides and hydrothermal rocks as well as the mineral assemblage and the paragenetic succession suggest that the sulphide precipitation in the sea floor took place at a low temperature 150 c without indication at least in the exposed section of a high temperature copper rich event sporadic deep subsea floor boiling is probably responsible for the formation of hydrothermal breccias and the wide extension of the stockwork its co au enrichment is interpreted as being related with the superposition of some critical factors such as the relationship with black shales the low temperature of formation and the boiling of hydrothermal fluids the present configuration and thickness of the orebody is due to the tectonic stacking of a thin and extensive blanket 2 4 km2 of massive sulphides with low aspect ratio they were formed by poorly focused venting of hot modified seawater equilibrated with underlying rocks into the seafloor massive sulphide precipitation took place by hydrothermal fluid quenching bacteriogenic activity and particle settling in an unusual restricted euxinic and shallow basin brine pool with a low detritic input but with important hydrothermal activity related to synsedimentary extensional faulting resedimentation of sulphides seems to be of major importance and responsible for the observed well mixed proximal and distal facies the tectonic deformation is largely heterogeneous and has been mostly channelled along the phyllonitic tectonized shales deformation bands thus sedimentary and diagenetic textures are relatively well preserved outside the deformation bands in the massive sulphides superimposed variscan recrystallization is not very important and only some early textures are replaced by metamorphic tectonic ones the stockwork is much more deformed than the massive sulphides the deformation has a critical effect on the present morphology of the orebody and the distribution of the ore minerals this deposit is a typical example of the sheet like shale hosted anoxic low temperature and zn rich massive sulphides developed in a ensialic extensional basin

the determination of source parameters for small earthquakes from a single very broadband seismic station the installation of very broadband seismic stations makes it possible to recover the source parameters of small earthquakes 2 5 ml 5 0 which occur at local and regional distances if the gross crustal structure along the travel path is known it is possible to use the p sv and sh displacement waveforms from a single station to determine the seismic moment tensor although the details of the crustal structure strongly affect the body waveforms at regional distances the signature of the seismic source orientation on the waveform is robust at frequencies less than 1 3 hz we explore the trade offs between crustal model hypocentral depth and filtering for a linear moment tensor inversion procedure the procedure is tested on two small earthquakes which occurred in the rio grande rift and were recorded at the iris usgs station anmo the agreement between the single station moment tensor inversion fault plane parameters and those determined from local first motions is excellent

tectonics of the jurassic early cretaceous magmatic arc of the north chilean coastal cordillera 22 26 s a story of crustal deformation along a convergent plate boundary the tectonic evolution of a continental magmatic arc that was active in the north chilean coastal cordillera in jurassic early cretaceous times is described in order to show the relationship between arc deformation and plate convergence during stage i circa 195 155 ma a variety of structures formed at deep to shallow crustal levels indicating sinistral arc parallel strike slip movements from deep crustal levels a sequence of structures is described starting with the formation of a broad belt of plutonic rocks which were sheared under granulite to amphibolite facies conditions bolfin complex the high grade deformation was followed by the formation of two sets of conjugate greenschist facies shear zones showing strike slip and thrust kinematics with a nw se directed maximum horizontal shortening i e parallel to the probable late jurassic vector of plate convergence a kinematic pattern compatible to this plate convergence is displayed by nonmetamorphic folds thrusts and high angle normal faults which formed during the same time interval as the discrete shear zones during stage ii 160 150 ma strong arc normal extension is revealed by brittle low angle normal faults at shallow levels and some ductile normal faults and the intrusion of extended plutons at deeper levels during stage iii 155 147 ma two reversals in the stress regime took place indicated by two generations of dikes an older one trending ne sw and a younger one trending nw se sinistral strike slip movements also prevailed during stage iv until 125 ma when the atacama fault zone originated as a sinistral trench linked strike slip fault the tectonic evolution of the magmatic arc is interpreted in terms of coupling and decoupling between the downgoing and overriding plates the structures of stages i and iv suggest that stress transmission due to seismic coupling between the plates was probably responsible for these deformations however decoupling of the plates occurred possibly due to a decrease in convergence rate resulting in extension and the reversals of stages ii and iii

moment energy stress drop and source spectra of western united states earthquakes from regional coda envelopes we present a new method to estimate stable seismic source parameters such as energy moment and orowan stress drop using regional coda envelopes from as few as one broadband station we use the method to compute path and site corrected seismic moment rate spectra for 117 recent western united states earthquakes empirical green s function corrections were applied to our surface and body wave coda envelope measurements to generate s wave source spectra these source spectra provide stable single station estimates of radiated seismic energy es and seismic moment mo that for common events are in excellent agreement with network averaged estimates obtained using local and regional data teleseismic moment estimates are compatible with our regional results but teleseismic energy estimates appear to be nearly an order of magnitude low we estimated the seismic moment of events ranging between mw 2 2 and 7 3 and energy estimates for which we had measured at least 70 of the total energy generally events above mw 3 3 we use these estimates to examine the behavior of derived parameters such as the orowan stress drop 2 es mo while the earthquakes we studied have a small range in orowan stress drop generally between 0 1 and 20 mpa they show a strong tendency for orowan stress drop to increase with moment approximately as mo0 25 we believe this is a source effect and is not due to inadequate bandwidth or attenuation correction and note that this trend appears to continue for microearthquakes as described in a recent deep borehole study in southern california many of the large high stress drop earthquakes show complexity in their moment rate spectra near the corner frequency and cannot be fit by a simple square model instead above the first corner frequency the spectral decay ranges between f 1 0 and f 1 5 this leads to larger estimates of radiated energy than predicted with a simple square model and has implications for seismic hazard estimation coda envelopes have three main advantages over direct arrivals for estimating seismic moment and energy 1 coda amplitudes vary little with geology and source radiation anisotropy and allow accurate single station applications 2 path corrected coda amplitude measurements can be applied to very large regions allowing a comparison of source parameters throughout the western united states using a common methodology and stations 3 because long period coda can last for hours for large local and regional events it allows the analysis of seismograms with clipped early arrivals

regional body wave attenuation using a coda source normalization method application to mednet records of earthquakes in italy we develop a new methodology to determine apparent attenuation for the regional seismic phases pn pg sn and lg using coda derived source spectra the local to regional coda methodology mayeda 1993 mayeda and walter 1996 mayeda et al 2003 is a very stable way to obtain source spectra from sparse networks using as few as one station even if direct waves are clipped we develop a two step process to isolate the frequency dependent q first we correct the observed direct wave amplitudes for an assumed geometrical spreading next an apparent q combining path and site attenuation is determined from the difference between the spreading corrected amplitude and the independently determined source spectra derived from the coda methodology we apply the technique to 50 earthquakes with magnitudes greater than 4 0 in central italy as recorded by mednet broadband stations around the mediterranean at local to regional distances this is an ideal test region due to its high attenuation complex propagation and availability of many moderate sized earthquakes we find that a power law attenuation of the form q f q sub 0 f sup y fit all the phases quite well over the 0 5 to 8 hz band at most stations the measured apparent q values are quite repeatable frommore event to event finding the attenuation function in this manner guarantees a close match between inferred source spectra from direct waves and coda techniques this is important if coda and direct wave amplitudes are to produce consistent seismic results less

source process and tectonic implication of the january 20 2007 odaesan earthquake south korea abstract the source process for the 20th of january 2007 mw 4 5 odaesan earthquake in south korea is investigated in the low and high frequency bands using velocity and acceleration waveform data recorded by the korea meteorological administration seismographic network at distances less than 70 km from the epicenter synthetic green functions are adopted for the low frequency band of 0 1 0 3 hz by using the wave number integration technique and the one dimensional velocity model beneath the epicentral area an iterative technique was performed by a grid search across the strike dip rake and focal depth of rupture nucleation parameters to find the best fit double couple mechanism to resolve the nodal plane ambiguity the spatiotemporal slip distribution on the fault surface was recovered using a non negative least square algorithm for each set of the grid searched parameters the focal depth of 10 km was determined through the grid search for depths in the range of 6 14 km the best fit double couple mechanism obtained from the finite source model indicates a vertical strike slip faulting mechanism the nw faulting plane gives comparatively smaller root mean squares rms error than its auxiliary plane slip pattern event provides simple source process due to the effect of low frequency that acted as a point source model three empirical green functions are adopted to investigate the source process in the high frequency band a set of slip models was recovered on both nodal planes of the focal mechanism with various rupture velocities in the range of 2 0 4 0 km s although there is a small difference between the rms errors produced by the two orthogonal nodal planes the sw dipping plane gives a smaller rms error than its auxiliary plane the slip distribution is relatively assessable by the oblique pattern recovered around the hypocenter in the high frequency analysis indicating a complex rupture scenario for such moderate sized earthquake similar to those reported for large earthquakes

active faults and evolving strike slip basins in the marmara sea northwest turkey a multichannel seismic reflection study abstract the north anatolian fault is a 1200 km long transform fault forming the boundary between the anatolian and eurasian plates near its western end it strikes through the marmara sea and is responsible for the creation of three deep marine depressions the north anatolian fault system and the linked basins in the eastern marmara sea were studied using newly acquired multi channel seismic reflection data in the marmara sea the north anatolian fault consists of a main strand and a few subsidiary branches the main strand is made up of the ganos 15 km long central marmara 105 km and north boundary 45 km fault segments the north boundary fault joins in the east to the izmit segment which was ruptured during the m s 7 4 earthquake on 17 8 1999 the north boundary fault is highly oblique to the regional displacement vector which results in the generation of a symmetrical fault wedge basin this cinarcik basin is a wedge shaped deep marine depression south of istanbul it is about 50 km long up to 20 km wide and 1250 m deep and is filled with pliocene to quaternary sediments over 3 km thick the north boundary fault joins in the west to the transpressional central marmara fault around the restraining segment boundary the syntransform sediments are being deformed into a large anticlinorium the cinarcik basin started to form when the westward propagating north anatolian fault intersected a northwest trending pre existing fault zone during the pliocene and bifurcated into nw and sw trending segments forming a transform transform transform type triple junction dextral strike slip movement along the arms of the triple junction led to the development of the cinarcik basin the present fault geometry in the marmara region was achieved later during the mid pliocene following the termination of the triple junction geometry south of the main north anatolian fault system there is a second active strike slip fault in the marmara sea made up of several segments a highly asymmetrical fault bend basin comprising pliocene quaternary sediments over 2 5 km thick is forming along a releasing fault segment of this south boundary fault system

microearthquake activity before the izmit earthquake in the eastern marmara region turkey 1 january 1993 17 august 1999 a telemetered seismic network izinet consisting of 13 stations has been in operation since 1993 in the western extension of the north anatolian fault zone nafz in the eastern marmara region the network was established to study microearthquake activity in this region which had been known as a seismic gap until the occurrence of the 17 august 1999 izmit kocaeli earthquake m w 7 4 for the last 7 yr about 3250 events were recorded and located local magnitudes of these events which were determined based on the duration of seismic coda waves were generally smaller than 4 0 seismicity in the time period studied clusters in five areas most of the events are found to be shallower than 20 km it turned out that before the 17 august 1999 izmit earthquake the izmit adapazari region was seismically more active than the other regions in the western extension of the nafz manuscript received 30 august 2000

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

coseismic and early post seismic slip associated with the 1999 izmit earthquake turkey from sar interferometry and tectonic field observations summary we use combined tectonic field observations and sar data to determine an improved model of the slip associated with the 1999 izmit earthquake which ruptured the north anatolian fault at the eastern end of the sea of marmara the leading goal is to understand the main features of the coseismic and post seismic deformation which are captured together in the sar data to achieve this we make a critical analysis of the ers1 2 sar data which allows atmospheric effects to be identified and removed we also use detailed field mapping and measurements of the earthquake surface rupture dislocations in elastic half space and a forward modelling strategy allow us to obtain a slip model by steps a trial and error approach is combined with conventional inversion techniques to determine the slip in the different regions of the fault the sar data are well explained with three main zones of high slip along the fault releasing a total moment of 2 3 10 20 nm mw 7 6 which is higher than the seismological estimates 1 7 2 0 10 20 n m the inhomogeneous slip distribution correlates with fault segments identified at the surface the izmit rupture appears to have extended 30 km west of the hersek peninsula into the sea of marmara with slip tapering fro m2mt ozero the western end of the rupture is located 40 km sse from istanbul we show that some features seen near to mudurnu and gevye and previously interpreted as slip on secondary faults are explained mostly as atmospheric effects correlated with the topography using our approach and the available gps data we obtain a slip model that represents the coseismic slip alone which suggests that the moment release during the main shock was 1 9 10 20 nm mw 7 5 consistent with the seismological estimates we conclude that the sar data include the effects of 2 m of fast after slip during the month following the main shock within a zone of the fault located 12 24 km below the epicentral region near the hypocentre at a depth of 18 km the fault appears to have experienced dynamic slip of 1 m associated with the main shock followed by 2 m of rapidly decelerating post seismic shear during the following month we suggest that the distribution of heterogeneous slip and loading along the different fault segments may be important factors controlling the propagation of large earthquake ruptures along the north anatolian fault

evidence for non constant energy moment scaling from coda derived source spectra 1 we present two lines of evidence showing the ratio of seismically radiated energy er to seismic moment mo increases with increasing moment for crustal events spanning 5 orders in seismic moment this ratio often referred to as the scaled energy er m0 has been elusive and the subject of recent debate within the seismological community because significant frequency dependent corrections must be made to account for source and path heterogeneity it is not uncommon that energy estimates of the same event by different researchers have significantly different values to minimize some of the potential problems we used the regional coda methodology outlined by mayeda et al 2003 on 4 large earthquake sequences mw 7 4 and 7 2 izmit duzce mw 7 2 gulf of aqaba mw 7 3 landers and mw 7 2 hector mine this methodology has been shown to provide the lowest variance estimate of the source spectrum when compared against traditional direct wave estimates in our first approach we made energy estimates from coda derived spectra and observed that increases with increasing moment for 3 7 mw 7 4 in our second approach we used the simple idea outlined by prieto et al 2004 to directly test for self similarity under self similarity earthquake source spectra scaled by 3 should have the same shape to test this one needs very stable spectra either through spectral stacking of direct wave spectra or by the use of stable coda derived spectra for all sequences we found that the mainshocks and larger aftershocks had significantly different spectral shapes than the smaller events the scaled 3 spectra of the larger events represented an upper bound having larger amplitudes near the corner frequency in fact an 3 5 scaling moved the larger events closer to the mean of the spectral population though the spectral shape differences persisted these results strongly suggest that earthquakes are not scaling self similarly and that complexities in the rupture process such as variable slip velocity exist between small and large events

source parameters of the sierra madre earthquake from regional and local body waves we inverted the three component long period data recorded by the terrascope array for the june 28 1991 sierra madre california event to determine the seismic moment and source orientation of the mainshock ml 5 8 remarkably four of the six stations were located 159 2 0 7 km from the epicenter variations in absolute traveltime were smaller than 2 and 3 for pn and sn whereas the surface waves displayed greater variation similarities in the waveforms and the small variance in traveltime suggest that a common green s function can be used to invert the data we used the whole waveforms excluding the fundamental surface waves at the more distant stations to invert for source parameters the results of the inversion indicated that this event was predominately a thrust type earthquake where the strike rake and dip were determined to be 235 74 and 50 respectively the seismic moment was determined to be 2 5 1024 dyne cm the source duration was found to be about 1 0 seconds by direct measurement of the s wave recorded at the pasadena station located 21 km from the epicenter considering circular rupture we obtain a stress drop of 460 bars

oxygen and hydrogen isotopes in the volcano sedimentary complex of huelva iberian pyrite belt example of water circulation through a volcano sedimentary sequence abstract the minerals of basic and acidic rocks from the volcano sedimentary sequence in the huelva area spain iberian pyrite belt display an extended 18o enrichment quartz 18o values from quartz keratophyres vary from 10 5 to 17 0 and feldspar 18o values from 14 4 to 16 0 for the spilite or spilitized dolerites 18o values vary from 9 9 to 13 4 for feldspar from 6 4 to 9 8 for chlorite from 3 7 to 4 3 for ilmenite and from 13 6 to 14 0 for quartz but pyroxene exhibits magmatic values from 5 3 to 6 1 with an exception at 7 5 the chlorite d values vary from 34 to 43 this is attributed to hydrothermal alteration with seawater enriched in 18o by circulation through sediments the temperatures of interaction determined from isotopic fractionations between minerals range from 400 to 520 c calculated d and 18o values for water in equilibrium with the minerals at isotopic temperatures range from 16 to 5 and from 8 3 to 12 8 respectively a model of circulation of seawater through a pile of sedimentary rocks and then through basaltic rocks is proposed to explain the high18o compositions of the rocks from the huelva district water rock mass ratios calculated from this model range between 0 3 and 0 7 for the determined range of temperatures

the role of the antofagasta calama lineament in ore deposit deformation in the andes of northern chile during the late jurassic early oligocene interval widespread hydrothermal copper mineralization events occurred in association with the geological evolution of the southern segment of the central andes giving rise to four ns trending metallogenic belts of eastward decreasing age late jurassic early cretaceous late paleocene early eocene and late eocene early oligocene the antofagasta calama lineament acl consists of an important dextral strike slip ne trending fault system deformation along the acl system is evidenced by a right lateral displacement of the late paleocene early eocene metallogenic belts furthermore clockwise rotation of the early cretaceous mantos blancos copper deposit and the late paleocene lomas bayas porphyry copper occurred in the late eocene early oligocene metallogenic belt a sigmoidal deflection and a clockwise rotation is observed in the acl the acl is thought to have controlled the emplacement of early oligocene porphyry copper deposits 34 37 ma toki genoveva quetena and opache whereas it deflected the late eocene porphyry copper belt 41 44 ma esperanza telegrafo centinela and polo sur ore deposits these observations suggest that right lateral displacement of the acl was active during the early oligocene we propose that the described structural features need to be considered in future exploration programs within this extensively gravel covered region of northern chile