turbulent velocity profiles for smooth and rough open channel flow velocity measurements using a laserdoppler anemometer are carried out in a fully developed rectangular subcritical open channel flow on smooth and rough beds the average roughness heights of t

controls on the composition of ni cu sulfide deposits as illustrated by those at noril sk siberia the ni cu pge ore deposits of the noril sk region have developed in feeder channels for permo triassic continental flood basalt volcanism particularly within 100 to 300 m thick elongate stratified intrusions that merge with an extensive system of peripheral sills through which the magma is thought to have continued to surface the mineralization is centered within two ore junctions the noril sk and talnakh ore junctions principal ore types include massive ore which occurs typically below or at the lowest margin of the intrusions disseminated ore in picritic and taxitic gabbrodolerite which constitute the lower part of the intrusions and copper ore which either forms an impregnation in hornfelsic country rock adjacent to massive ore or occupies the matrix of breccia zones that have developed at the front and upper contact of the intrusions although showing a close spatial relationship to the intrusions the massive ore particularly that underlying the northwest talnakh intrusion appears to have been injected separately over 500 samples have been analyzed for ni cu s pt pd rh ru ir os and au by nis fire assay acid dissolution and neutron activation the massive ore of the kharayelakh orebody beneath the northwest talnakh intrusion has fractionated as injection proceeded from east to west with the fractionated liquid moving progressively farther west this liquid has also soaked into the surrounding hornfels to produce the cu rich mantle and above the western part of the kharayelakh orebody where the cu enrichment is most pronounced has also affected the lower part of disseminated ore zones within the intrusion study of the disseminated ore has revealed that this has not fractionated to a great degree and that adequate sampling gives an average composition close to that of the primary sulfide liquid disseminated ore from different parts of the talnakh ore junction are characterized by very different metal tenors with rh ranging from 4 000 to 10 000 ppb the composition of the disseminated ore is modeled as the result of initial low tenor sulfides becoming trapped in the ore bearing intrusions and then interacting with successive surges of new magma passing along the feeder channels represented by their host intrusions on the way to the surface the different tenors of the different ore junctions and parts of ore junctions are the consequence of the effective number of times the magma passing through a particular channel exceeds the amount of sulfide within the channel higher ratios leading to higher tenors

temperature dependence of sulfide and sulfate solubility in olivine saturated basaltic magmas abstract the sulfur concentration at pyrrhotite and anhydrite saturation in primitive hydrous basaltic melt of the 2001 2002 eruption of mt etna was determined at 200 mpa t 1050 1250 c and at log fo2 from fmq to fmq 2 2 fmq is fayalite magnetite quartz oxygen buffer at 1050 c au sample containers were used a double capsule technique using a single crystal olivine sample container closed with an olivine piston embedded in a sealed au80pd20 capsule was developed to perform experiments in s bearing hydrous basaltic systems at t 1050 c pyrrhotite is found to be a stable phase coexisting with melt at fmq fmq 0 3 whereas anhydrite is stable at fmq 1 4 fmq 2 2 the s concentration in the melt increases almost linearly from 0 12 0 01 to 0 39 0 02 wt s at fes saturation and from 0 74 0 01 to 1 08 0 04 wt s at anhydrite saturation with t ranging from 1050 1250 c the relationships between s concentration at pyrrhotite and or anhydrite saturation mgo content of the olivine saturated melt t and log fo2 observed in this study and from previous data are used to develop an empirical model for estimating the magmatic t and fo2 from the s and mgo concentrations of h2o bearing olivine saturated basaltic melts the model can also be used to determine maximum s concentrations if fo2 and mgo content of the melt are known the application of the model to compositions of melt inclusions in olivines from mt etna indicates that the most primitive magmas trapped in inclusions might have been stored at log fo2 slightly higher than fmq 1 and at t 1100 1150 c whereas more evolved melts could have been trapped at t 1100 c these values are in a good agreement with the estimates obtained by other independent methods reported in the literature

boundary shear stress in spatially varied flow with increasing discharge the distribution of the wall shear stress on the bed and sidewalls of an open channel receiving lateral inflow was obtained from experimental measurements of the distribution of the velocity in the viscous sublayer using a laser doppler velocimeter the experiments were conducted in a 0 4 m wide by 7 5 m long flume lateral inflow was provided into the channel from above via sets of nozzles positioned toward the downstream end of the flume lateral inflow was provided over a length of 1 9 m the results indicate that the local boundary shear stresses are significantly influenced by lateral inflow the significant variation occurs near and around the region where the lateral inflow enters the channel at various measurement positions along the lateral inflow zone mean boundary mean wall and mean bed shear stresses were obtained and compared the results indicate that the mean boundary shear stresses increase from the upstream to the downstream ends of the lateral inflow zone the results also indicate t

kinetic controls on the partitioning of trace elements between silicate and sulfide liquids mass transfer between sulfide and silicate liquids is often discussed elements pge has resulted from liquation immiscible by reference to a mass ratio between hypothetical liquid reservoirs liquid phase separation of sulfide liquid from mafic or at equilibrium defined as r in an open system not at equilibrium ultramafic silicate magma a central assumption of modthe mass of silicate melt from which a growing sulfide droplet els of magmatic sulfide deposit formation is that the base appears to have scavenged chalcophile elements will depend on metals and pge are strongly partitioned into the sulfide diffusivities di and dfes of the element and of the fes component melt previous discussions of the process by which sulfide in the silicate melt respectively on the degree of supersaturation of liquids become enriched in chalcophile metals have fothe melt with fes c o on the radius a of the droplet and on the cused almost exclusively on models in which coexisting velocity v with which the droplet is advected through the melt so bodies of sulfide and silicate melt are considered to be that in equilibrium at all times the intent of this paper is to demonstrate that natural sulfide deposits preserved in igneous rocks will in many r 1 c fes o di 1 2 adiv dfes 1 2 adfesv instances record metal distributions that never attained equilibrium as a result of the kinetic constraints on metal chalcophile elements are expected to show inter element variations partitioning between phases the consequences are that in d spanning several orders of magnitude in some melts leading different elements will seem to show evidence for equito large inter element variations in effective r in a given sulfide libration at different silicate sulfide mass ratios within body these variations in effective r will lead to spatial separations single sulfide bodies i describe the time dependent evolubetween zones of maximum enrichment of chalcophile elements tion of metal distributions in silicate sulfide melt systems produced during fractional segregation of sulfide in layered intrusions starting with analytical solutions for simple boundary whereas it has proven impossible to model the generation of spatially conditions and then adapting them to more complex offset stratiform horizons in the australian munni munni layered systems as numerical models intrusion using equilibrium partition coefficients the present kinetic model reproduces the observed patterns with great fidelity

the diffuse transition between the zagros continental collision and the makran oceanic subduction iran microearthquake seismicity and crustal structure summary the nature of the transition between the zagros intra continental collision and the makran oceanic subduction is a matter of debate either a major fault cutting the whole lithosphere or a more progressive transition associated with a shallow gently dipping fault restricted to the crust microearthquake seismicity located around the transition between the transition zone is restricted to the west of the jaz murian depression and the jiroft fault no shallow micro earthquakes seem to be related to the nnw sse trending zendan minab palami active fault system most of the shallow seismicity is related either to the zagros mountain belt located in the west or to the ns trending sabzevaran jiroft fault system located in the north the depth of microearthquakes increases northeastwards to an unusually deep value for the zagros of 40 km two dominant types of focal mechanisms are observed in this region low angle thrust faulting mostly restricted to the lower crust and strike slip at shallow depths both consistent with ns shortening the 3 d inversion of p traveltimes suggests a high velocity body dipping northeastwards to a depth of 25 km this high velocity body probably related to the lower crust is associated with the deepest earthquakes showing reverse faulting we propose that the transition between the zagros collision and the makran subduction is not a sharp lithospheric scale transform fault associated with the zendan minab palami fault system instead it is a progressive transition located in the lower crust the oblique collision results in partial partitioning between strike slip and shortening components within the shallow brittle crust because of the weakness of the pre existing zendan minab palami faults

adv measurements of velocity distributions in a gravel bed flume velocity measurements carried out by an acoustic doppler velocimeter adv in a rectangular laboratory ume having a gravel bed are presented the velocity pro les are measured in six verticals of the channel cross section having an increasing distance from 4 to 38 5 cm from the ume wall the experimental runs are carried out for ve different bed arrangements characterized by different concentrations of coarser elements and for the two conditions of small and large scale roughness for both hydraulic conditions the velocity measurements are rst used to test the applicability of the dean pro le and of the logarithmic pro le corrected by a divergence function proposed in this paper then for each value of the depth sediment ratio h d84 the non dimensional friction factor parameter is calculated by integration of the measured velocity distributions in the different verticals of the cross section finally a semi logarithmic ow resistance equation is empirically deduced copyright 2003 john wiley sons ltd

bed shear from velocity profiles a new approach a new binary law of velocity distribution has been developed to describe the velocity profile for the entire flow region the law is a combination of logarithmic law valid in the wall inner region and parabolic law valid in the core outer region of the flow the validity of the law has been established based on earlier data on flat plates rough and smooth pipes and experimental data obtained from rigid walled open channels with plane sand beds a procedure of estimating bed shear stress from the proposed law of velocity distribution using the measured velocity profile has been evolved bed shear estimates made according to this procedure are in agreement with the values obtained from uniform flow analysis in the case of open channel flow over a sediment bed the proposed method of estimating the bed shear stress from the observed velocity profiles is found to be particularly useful in cases where it is difficult to determine precisely the true bed level such as in the case of flow over sediment beds

the effect of water and fo2 on the ferric ferrous ratio of silicic melts new experiments on the effect of dissolved water on the ferric ferrous ratio of silicic melts have been performed at 200 mpa between 800 c and 1000 c and for fo2 between nno 1 35 and nno 6 6 water saturated conditions were investigated compositions studied include six metaluminous synthetic melts with feotot progressively increasing from 0 47 to 4 25 wt two natural obsidian glasses one peraluminous and the other peralkaline and a synthetic rhyolitic glass having the composition of the matrix glass of the june 15 1991 pinatubo dacite ferrous iron was analyzed by titration and feotot by electron microprobe variation of quench rate was found to have no detectable effect on the ferric ferrous ratio of the hydrous silicic melts investigated at nno no dependence of the ferric ferrous ratio with temperature is observed at fo2 nno 1 the experimental ferric ferrous ratios are equal or lower than calculated the peralkaline samples show the same type of behaviour a non linear relationship between xfe2o3 xfeo and fo2 implies that a term for dissolved water must be added to the kc equation if it is to be applied to the calculation of ferric ferrous ratios of hydrous silicic melts above nno 1 the ferric ferrous ratio is essentially controlled by the anhydrous melt composition and fo2 however differences exist between measured and calculated ferric ferrous ratios of silicic melts that are not all attributable to the effect of dissolved water additional work is needed to describe more precisely the dependence of the ferric ferrous ratio on anhydrous melt composition the oxidizing effect of water is restricted to relatively reduced magmatic liquids in oxidized calk alkaline magma series the presence of dissolved water will not largely influence melt ferric ferrous ratios

modeling s wave amplitude patterns for events in the kurile slab using three dimensional gaussian beams 1 the shear velocity structure of the subducted kurile slab is modeled using shear wave amplitude residual spheres we measure long period sh and scsh phase amplitudes for 10 intermediate and deep focus earthquakes recorded at world wide standardized seismograph network and canadian seismic network stations from 1967 to 1986 after correction for source radiation pattern geometric spreading and empirical receiver upper mantle effects the data for intermediate depth kurile slab events show smoothly varying amplitude residual sphere patterns with low amplitudes concentrated in the direction down the slab dip the data are modeled using three dimensional dynamic ray tracing and a three dimensional gaussian beam method starting models are taken from previous p and s wave arrival time residual sphere studies three dimensional ray tracing indicates that ray patterns and resulting amplitudes are very sensitive to the depth extent of the slab and to the position of the event relative to the across slab velocity gradient this sensitivity allows us to place some constraints on the kurile slab geometry position of each event within the slab and penetration depth of coherent slab structure our final slab model is defined by an asymmetric error function that peaks at 4 higher velocity than preliminary reference earthquake model 25 km from the top of the slab the total width of the thermal anomaly averages 140 km the slab is tabular and extends to 670 km in the northern half of the kurile subduction zone in the southern half of the subduction zone the slab flattens along the 670 km discontinuity and deflects laterally persisting to 750 km depth

characteristics of supercritical flow below sluice gate supercritical flow below a sluice gate in a horizontal smooth rectangular channel is investigated to explain the effect of the inflow condition on the characteristics of the hydraulic jump the movement of jump location to variations of tailwater level is also examined so the position of the jump in a horizontal apron can be stabilized the distributions of mean velocities and turbulence intensities were obtained with a laser doppler velocitymeter for a wide range of supercritical froude numbers the development of the turbulent boundary layer the water surface profile and the location of the critical point the point where the limit of the boundary layer crosses the water surface are predicted by an approach to the boundary layer analysis and the agreement of those observations with the experimental data is presented using the analyzed water surface profiles the movement of jump location to variations of tailwater level is predicted accurately and verified by laboratory experiments

remote determination of the velocity index and mean streamwise velocity profiles when determining volumetric discharge from surface measurements of currents in a river or open channel the velocity index is typically used to convert surface velocities to depth averaged velocities the velocity index is given by k ub usurf where ub is the depth averaged velocity and usurf is the local surface velocity the usgs united states geological survey standard value for this coefficient k 0 85 was determined from a series of laboratory experiments and has been widely used in the field and in laboratory measurements of volumetric discharge despite evidence that the velocity index is site specific numerous studies have documented that the velocity index varies with reynolds number flow depth relative bed roughness and with the presence of secondary flows a remote method of determining depth averaged velocity and hence the velocity index is developed here the technique leverages the findings of johnson and cowen 2017 and permits remote determination of the velocity power law exponent thereby enabling remote prediction of the vertical structure of the mean streamwise velocity the depth averaged velocity and the velocity index

a new genetic model for the giant ni cu pge sulfide deposits associated with the siberian flood basalts the kharaelakh intrusion is one of several sill like multiphase gabbroic intrusions that host world class ni cu pge deposits in the noril sk talnakh region the sulfide ores of the kharaelakh intrusion are characterized by elevated 34s values 10 12 and high pge concentrations e g up to10 ppm pt the 34s values require addition of crustal s with elevated isotope ratios such as evaporite bearing country rocks 34s 20 and r factors magma sulfide mass ratios of 2 000 if pt content in the magma is similar to the values in the coeval most undepleted lavas 10 ppb such a discrepancy can be explained by sulfide resorption by a new flux of mantle derived magma into a deep staging chamber to form pge enriched magma interaction of the pge enriched magma with evaporite bearing country rocks in the plumbing system at higher crustal levels could have produced sulfide liquids with high pge contents as well as elevated 34s values mass balance calculations indicate that 0 9 wt percent anhydrite assimilation from evaporite bearing country rocks is required to explain the elevated 34s values of the sulfide ores this model although developed purely based on data from the kharaelakh deposit can also be applied to other coeval ni cu pge deposits for the coeval noril sk i and talnakh deposits different depths of anhydrite assimilation in the respective plumbing systems are required this model differs from the previously proposed models in detail but reenforces the idea that chalcophile element depletion in continental flood basalts is a useful exploration tool for ni cu pge deposits associated with coeval subvolcanic intrusions

magma differentiation and mineralisation in the siberian continental flood basalts new major trace element and sr and nd isotope data are presented for selected lavas from the three uppermost formations in the siberian trap and on over 60 samples of the associated intrusive rocks the lavas from a 1400 m section are remarkably homogeneous and apart from four samples of basaltic andesites sio2 48 4 49 6 mgo 8 1 6 3 and mg 54 58 tio2 1 05 1 6 sr 1 7 and nd 3 8 1 3 there is no significant depletion in ni and cu or coupled increase in sio2 and la sm which so characterise the underlying nadezhdinsky formation rocks the intrusive rocks are considered in 5 groups following naldrett et al the alkaline rocks group 1 dolerites with a range of ti contents groups 2 and 3 and differentiated intrusions not associated with ore junctions group 4 all exhibit restricted initial sr and nd values of 3 32 and 3 5 to 3 2 respectively in contrast the intrusions related to ore junctions noril sk and lower talnakh types 5a and 5b trend towards higher sr and lower nd with sr 17 59 and nd 2 9 to 3 4 in the noril sk type and 41 66 and 3 7 to 6 2 respectively in the lower talnakh type the roles of crustal contamination and partial melting in the continental mantle lithosphere are briefly reviewed a minimum of three components are required to explain the basalt data which are therefore inconsistent with simple mixing between plume derived magmas and crustal material rather magmas were derived from both the mantle lithosphere and the underlying asthenosphere and crustal contamination modified the composition of specific magma types the minor and trace element characteristics of the contaminant appear to have been similar to those of an inferred deep seated crustal melt rather than an upper crustal melt or a bulk sediment the between suite variations in the intrusions are similar to those in the lavas but in addition there are within suite variations attributed to late stage open system differentiation within the noril sk and lower talnakh type intrusions in the preferred model in which sulphide precipitation occurred in response to the crustal contamination processes responsible for the elevated la sm and lower nd of the lower talnakh and nadezhdinsky rocks sulphide precipitation took place before the crystallization of the silicate phases currently preserved in the intrusive rocks

geochemistry and origin of the intrusive hosts of the noril sk talnakhcu ni pge sulfide deposits the world class deposits of cu ni and platinum group elements pge of the noril sk talnakh district in russia are hosted by relatively small complex mafic ultramafic bodies that intrude permian sedimentary rocks and the lowermost suites of the siberian continental flood volcanic sequence the noril sk type ore bearing intrusions immediately overlie and are probably penecontemporaneous with weakly mineralized intrusions of the lower talnakh type which have similar petrological features but contrasting and much more variable nd os and sr isotopic compositions several types of spatially associated intrusions were emplaced after the ore bearing intrusions and the flood volcanic sequence to clarify relations between the various types of igneous bodies flood volcanic rocks noril sk type intrusions lower talnakh type intrusions and later intrusions and to help understand the formation of the ore deposits we undertook a detailed geochemical and nd os and sr isotopic study of eight of the more important intrusions the data indicate that these intrusions formed by the input of a series of magma pulses each of which produced rocks with distinctive petrology and chemical compositions these compositions are interpreted to have formed from mixtures of mantle derived magmas and different types of crustal rock which were encountered and assimilated during passage to the surface some of these variations may be superimposed on heterogeneities inherited from the mantle source the magmas that formed the lower talnakh type intrusions became contaminated with large amounts of crustal rock in a deep staging chamber the chemical and isotopic characteristics of the resultant hybrid magmas are broadly similar to those of basalts of the lower and middle nadezhdinsky lava subsuites nd 1 2 which are located about one third of the way through the overlying lava sequence these magmas became saturated in sulfur during contamination and segregation of sulfides resulted in the depletion of chalcophile elements recorded in the nd 1 2 lavas magmas feeding the ore bearing intrusions had trace element and isotopic compositions similar to those of the basalts in the upper two thirds of the volcanic sequence these magmas underwent lower degrees of contamination in a deep staging chamber and sulfur saturation was not reached these magmas therefore contained a full compliment of chalcophile elements when they encountered anhydrite rich sediments during passage toward the surface assimilation of these sediments led to the segregation of sulfides to form the ores two aspects of our data impose important constraints on the ore forming process the first is the os isotopic composition of the ore sulfides avg os 7 which is similar to that of mantle rocks and very different from those of sulfides that segregate from highly contaminated magma the second is the absence of ni depletion in olivine in rocks from the ore bearing intrusions most notably in the ore rich picritic gabbrodolerites the simplest explanation is that the sulfides segregated from magmas that were not highly contaminated and were transported into the intrusions by magmas different from those that yielded the sulfide if this explanation is correct it imposes some modifications to earlier models of sulfide ore deposition in the conduits of flood basalts

an investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the united states in the 0 5 4 hz band summary studies of teleseismic p and s wave amplitudes and spectra in the 0 5 4 hz band show large variations in the attenuative properties of the upper mantle under the united states the data indicate that attenuation is greatest under the south western united states including but not confined to the basin and range province the lowest attenuation prevails under the north central shield regions the north eastern part of the country consisting of new england and possibly including a larger area along the eastern seaboard is characterized by moderate attenuation in the mantle the level of the high frequency energy in short period seismic waves and the differences between q values derived from short and long period data indicate that q is frequency dependent the form of frequency dependence of t compatible with the data in the 0 5 4 hz range does not allow a rapid decrease of t with increasing frequency rather it supports a gradual decrease covering the broader 0 1 4 hz range the curves of t versus frequency for shield to shield and mixed shield to western united states type paths are parallel with an average difference of 0 2 s in t in the short period band but may diverge towards the long period band for both curves t p is below 1 s for shield to shield paths t p must be below 0 5 s at 1 hz

a minimum upb age for siberian flood basalt volcanism abstract establishing an accurate and precise age for siberian flood basalt volcanism is of great importance in evaluating causes for the unequaled mass extinction of flora and fauna at the permian triassic boundary we report a new minimum u pb age obtained from zircon and baddeleyite from the mineralized noril sk i intrusion that cuts the lower third of this rapidly deposited 3500 m thick volcanic sequence near noril sk this 251 2 0 3 2 ma age is within analytical error of the shrimp u pb age for zircon from the permian triassic boundary at meishan south china 251 1 3 6 ma 2 and confirms siberian basaltic volcanism as a possible contributor to the mass extinction

micro scale s isotope studies of the kharaelakh intrusion noril sk region siberia constraints on the genesis of coexisting anhydrite and sulfide minerals abstract the coexistence of magmatic anhydrite and sulfide minerals in non arc related mafic magmas has only rarely been documented likewise the s isotope fractionation between sulfate and sulfide in mafic rocks has infrequently been measured in the kharaelakh intrusion associated with the world famous noril sk ore district in siberia coexisting magmatic anhydrite and sulfide minerals have been identified sulfur isotope compositions of the anhydrite sulfide assemblages have been measured via both ion microprobe and conventional analyses to help elucidate the origin of the anhydrite sulfide pairs magmatic anhydrite and chalcopyrite are characterized by 34 s values between 18 8 and 22 8 and 9 3 and 13 2 respectfully coexisting anhydrite and chalcopyrite show values that fall between 8 5 and 11 9 anhydrite in the kharaelakh intrusion is most readily explained by the assimilation of sulfate from country rocks partial reduction to sulfide led to mixing between sulfate derived sulfide and sulfide of mantle origin the variable anhydrite and sulfide 34 s values are a function of differing degrees of sulfate reduction variable mixing of sulfate derived and mantle sulfide incomplete isotopic homogenization of the magma and a lack of uniform attainment of isotopic equilibrium during subsolidus cooling the 34 s values of sulfide minerals have changed much less with cooling than have anhydrite values due in large part to the high sulfide sulfate ratio variations in both sulfide and anhydrite 34 s values indicate that isotopically distinct domains existed on a centimeter scale late stage hydrothermal anhydrite and pyrite also occur associated with ca rich hydrous alteration assemblages e g thomsonite prehnite pectolite epidote xonotlite 34 s values of secondary hydrothermal anhydrite and pyrite determined by conventional analyses are in the same range as those of the magmatic minerals anhydrite pyrite values are in the 9 1 10 1 range and are smaller than anticipated for the low temperatures indicated by the silicate alteration assemblages the small values are suggestive of either sulfate sulfide isotopic disequilibrium or closure of the system to further exchange between 550 and 600 c our results confirm the importance of the assimilation of externally derived sulfur in the generation of the elevated 34 s values in the kharaelakh intrusion but highlight the sulfur isotopic variability that may occur in magmatic systems in addition our results confirm the need for more precise experimental determination of sulfate sulfide sulfur isotope fractionation factors in high t systems

siderophile and chalcophile metal variations in tertiary picrites and basalts from west greenland with implications for the sulphide saturation history of continental flood basalt magmas sixty five million year old continental flood basalts crop out on qeqertarssuaq island and the nuussuaq peninsula in west greenland and they include 1 000 m of picritic lavas and discrete 10 to 50 m thick members of highly contaminated basalts on qeqertarssuaq the lavas are allocated to the vaigat and malig t formations of which the former includes the naujanguit member which consists of picrites with 7 29 wt mgo 80 1 400 ppm ni 5 7 9 4 ppb pt and 4 2 12 9 ppb pd the naujanguit member contains two horizons of contaminated basalts the asuk and kuganguaq which have elevated sio2 52 58 wt and low to moderate mgo 7 5 12 8 wt these lavas are broadly characterized by low cu and ni abundances average 40 ppm ni and 45 ppm cu and very low pt 0 16 0 63 ppb and pd 0 13 0 68 ppb abundances and in the case of the asuk they contain shale xenoliths and droplets of native iron and troilite the contaminated basalts from nuussuaq the b0 to b4 members are also usually ni cu and platinum group elements pge depleted the geochemical signatures especially the ratios of incompatible trace elements such as th nb of all of the contaminated basalts from qeqertarssuaq and some of those from nuussuaq record what appears to be a chemical contribution from deltaic shales that lie immediately below the lavas this suggests that the contamination of the magmas occurred during the migration of the magmas through plumbing systems developed in sedimentary rocks and hence at a high crustal level nickel cu and pge depletion together with geochemical signatures produced by crustal contamination are also a feature of siberian trap basalts from the noril sk region these basalts belong to the 0 to 500 m thick 5 000 to 10 000 km3 nadezhdinsky formation which is centered in the noril sk region a major difference between siberia and west greenland is that pge depletion in the nadezhdinsky formation samples with the lowest cu and ni contents is much more severe than that of the west greenland contaminated basalts moreover the volumes of the contaminated and metal depleted volcanic rocks in west greenland pale is significant when compared to the nadezhdinsky formation local centers rarely contain more than 15 thin flows with a combined thickness of 50 m and more typically 10 20 m so the volume of the eruptive portions of each system is probably two orders of magnitude smaller than the nadezhdinsky edifice the west greenland centres are juxtaposed along fault zones that appear to be linked to the subsidence of the tertiary delta and so emplacement along n s structures appears to be a principal control on the distribution of lavas and feeder intrusions this leads us to suggest that the greenland system is small and segregation of sulphide took place at high levels in the crust whereas at noril sk the saturation event took place at depth with subsequent emplacement of sulphide bearing magmas into high levels of the crust as a consequence it may be unreasonable to expect that the west greenland flood basalts experienced mineralizing processes on the scale of the noril sk system

multiple frequency sh wave tomography of the western us upper mantle summary we estimate the sh wave velocity and attenuation structures of the western us upper mantle using the dense network of the usarray and new techniques we observe a multiple frequency data set of both traveltime and amplitude anomalies and interpret these with full 3 d finitefrequency sensitivity kernels amplitudes show stronger frequency dependence than traveltimes we perform a joint inversion on the measured traveltime and amplitude anomalies interpreting them in terms of velocity and attenuation heterogeneities aside from the expected clear division between the slow tectonically active region in the west and the fast craton in the east several interesting smaller velocity anomalies are observed the subduction along the cascades at 100 300 km depths shows lateral discontinuity with a slab hole absence of fast anomalies observed around 45 n the delaminated sierra nevada mountains root is observed to have sunk to 200 km depth the yellowstone plume seems to have an origin weak slow velocity anomalies near 1000 km depth but the plume conduit seems to be interrupted by a fast anomaly which is identified as a fragment of the farallon slab the s velocity model shows a trench perpendicular slab gap absence of fast anomalies at almost the same location as in the p model recently published by sigloch et al 2008 the methodological improvements described in the first paragraph have several benefits amplitude data help to sharpen the edges of narrow velocity heterogeneities in the shallow upper mantle the focusing effect from velocity heterogeneity dominates over that of attenuation and must be considered when interpreting amplitude anomalies in general velocity and attenuation heterogeneities correlate positively suggesting that temperature plays a major role in forming the anomalies

insights into ore genesis of ni cu pge sulfide deposits of the noril sk province russia evidence from copper and sulfur isotopes abstract combined cu s isotope data for ni cu pge sufides from the economic deposits hosted in the noril sk 1 talnakh and kharaelakh intrusions from the subeconomic deposits in the chernogorsk zub marksheider and vologochan intrusions and from the non economic occurrences in the nizhny talnakh intrusion in the noril sk province russia and the j m reef in the stillwater complex usa are presented for the first time most sulfide samples including the ores from the talnakh intrusion and the stillwater complex have a restricted range of 65 cu values from 1 1 to 0 whereas those from the kharaelakh and noril sk 1 intrusions have more variable 65 cu values of 2 3 to 1 0 samples from the three economic deposits in the noril sk province have distinct mean 65 cu values of 1 56 0 27 for kharaelakh 0 55 0 41 for talnakh and 0 23 0 28 for noril sk 1 consistent with those for carbonaceous chondrite and iron meteorites the variation of 65 cu values is interpreted to represent a primary signature of the ores although a magmatic fractionation of cu isotopes and or assimilation from an external source cannot be ruled out particularly in the case of the kharaelakh ores collectively the eight investigated intrusions have an overall sulfur 34 s range from 0 7 to 13 8 disseminated and massive ores of the same intrusion have similar 34 s values the disseminated and massive ores of the khraelakh intrusion have a mean 34 s value of 12 57 0 54 and 12 76 0 42 respectively which are distinctly different from those of the disseminated 10 97 0 44 and massive ores 10 88 0 77 of the talnakh intrusion the different 34 s values of the intrusions may be attributed to sulfur fractionation in deep seated magma chambers rather than at shallow levels or the present emplacement site the mean 34 s value of the disseminated ores from the subeconomic ni cu pge deposits and non economic occurrences spans over 10 5 averaging 0 39 with a standard deviation of 1 55 for the highly contaminated zub marksheider rocks 6 38 1 89 for nizhny talnakh 6 90 1 17 for vologochan and 10 86 0 43 for chernogorsk samples from the zub marksheider intrusion have mantle like s isotope signatures consistent with a deep seated origin although individual mineralized instrusions have a restricted range the overall trend they define of falling 34 s with rising 65 cu values might be a useful indicator of the economic potential of ni cu pge sulfide deposits

remobilisation of the continental lithosphere by a mantle plume major trace element and sr nd and pb isotope evidence from picritic and tholeiitic lavas of the noril sk district siberian trap russia the late permian to early triassic siberian traps have been sampled by drill core core sg 9 and from surface exposure section 1f in the noril sk region of the siberian platform russia combined major trace element and nd sr and pb isotope data on selected samples through the siberia trap offer new chemostratigraphic criteria for the identification and characterisation of two fundamentally different magma types and 9 of the 11 formations of lava developed near noril sk a lower sequence of sub alkalic basalts tholeiites and picritic basalts upwards these are the ivakinsky syverminsky and gudchichinsky formations are overlain by an upper sequence of picritic basalts and tholeiites interbedded with tuffs upwards these are the khakanchansky tuklonsky nadezhdinsky morongovsky mokulaevsky and kharayelakhsky formations the gudchichinsky and tuklonsky formations contain both picritic and tholeiitic lavas the tuklonsky formation tholeiites and picrites have moderate gd yb 1 6 1 8 low tio2 0 45 0 95 wt a significant negative ta and nb anomaly nb la 0 42 0 57 and unradiogenic nd nd chur to 4 6 in contrast both the gudchichinsky formation tholeiites and picrites have high gd yb 2 3 3 1 and tio2 1 2 2 3 wt no significant nb or ta anomaly nb la 0 8 1 1 and radiogenic nd nd chur to 7 3 the low ti and nb la high la sm and unradiogenic nd isotope signatures of the picritic tuklonsky formation lavas and the tholeiitic lavas of the upper sequence are characteristic of magmas strongly influenced by material from the continental lithosphere whereas the high ti and nb la low la sm and radiogenic nd isotope signatures of the lower sequence are more comparable to deeper asthenospheric mantle plume generated lavas similar to oceanic island basalts the lavas overlying the tuklonsky formation have mg numbers of 0 63 to 0 68 and are more evolved than the tuklonsky mg number 0 62 and have more radiogenic nd chur tuklonsky 0 03 to 4 66 mokulaevsky 0 60 to 1 61 but have many of the incompatible trace element features of the tuklonsky sky type magma these lavas show a progressive upwards decline in sio2 55 49 wt la sm 4 6 2 0 and ur sr 67 to 13 which has previously been attributed to a decrease in the proportion of crustal material contributed to the magma this paper explores and alternative model where a component of the crustal contribution might be derived from within an ancient region of the mantle lithosphere as recycled sediment rather than from the overlying continental crust

extremely reducing conditions reached during basaltic intrusion in organic matter bearing sediments redox conditions in magma are widely interpreted as internally buffered and closely related to that of their mantle source regions we use thermodynamic calculations to show that high temperature interaction between magma and organic matter can lead to a dramatic reduction of the magma redox state and significant departure from that of the original source field studies provide direct evidence of the process that we describe with reported occurrences of graphite and native iron in igneous mafic rocks implying very reducing conditions that are almost unknown in average terrestrial magmas we calculate that the addition of 0 6 wt organic matter in the form of ch or ch2 to a standard basalt triggers graphite and native iron crystallization at depths of few hundred meters interaction with organic matter also profoundly affects the abundance and the redox state of the gases in equilibrium with the magma which are co dominated with h2 as the second most abundant species on a molar basis h2o and co2 being minor constituents the assimilation of only 0 1 wt organic matter by a basalt causes a decrease in its oxygen fugacity of 2 orders of magnitude the assimilation of 0 6 wt organic matter at depths 500 m implies minimum co content in the magma of 1 wt other gas components being less than 0 1 wt in the light of our calculations we suggest that the production of native iron bearing lava flows and associated intrusions was most likely accompanied by degassing of co rich gases whose fluxes depended on the magma production rates

petrogenesis of the massive chromitite layer from the jacurici complex brazil evidence from inclusions in chromite the jacurici complex hosts the largest chromite deposit in brazil in an up to 8 m thick chromitite layer within a tectonically segmented 300 m thick intrusion the ore has been interpreted as the result of crustal contamination driven crystallization in a magma conduit this study addresses the stratigraphy mineralogical and textural relationships and mineral chemistry of the monte alegre sul segment focusing on chromite hosted inclusions from the main chromitite layer to understand the role of volatiles in the genesis of the massive chromitite silicate inclusions enstatite phlogopite magnesiohornblende diopside and olivine are commonly monomineralic and sub to euhedral and crystallized prior to or coeval with the chromite crystallization carbonate inclusions dolomite and magnesite are irregular or have negative crystal shapes suggesting entrapment as melt droplets sulfides pentlandite millerite heazlewoodite polydymite pyrite and chalcopyrite are often polymineralic irregular or hexagonal shaped indicating entrapment as sulfide melt and as monosulfide solid solution the inclusions indicate an h2o and s saturated resident magma with immiscible droplets of carbonate melt during chromite crystallization inclusion rich and inclusion free chromites that occur together have similar compositions and are considered to have formed from the same magma in response to variations in the degree of cr saturation hot primitive magma might have heated and mobilized co2 and probably water from devolatized and assimilated carbonate rich wall rocks increasing fo2 and triggering chromite crystallization we propose that the formation of the chromitite layer started as in situ crystallization with additional material added by slumping of locally remobilized chromite slurries facilitated by the presence of volatiles

some analyses of p and rayleigh wave amplitudes observed at north american stations summary p and rayleigh wave amplitudes observed by the long range seismic measurements network of stations in north america are analysed into source distance and station effects the main results of the p wave analyses are a there is a significant correlation of station effect and n the pn wave speed in the vicinity of the recording station b there are no contributions to the station effect from differences in the noise levels at the recording stations c the short period sp station effects are weakly dependent on period but the correlation may be partially masked by systematic errors in the measurement of period d the variation in crustal structure makes little or no contribution to the sp and long period lp station effects the main results of the rayleigh wave analyses are a the gradient h of the decay of amplitude with distance a is nearly unity this is in agreement with earlier estimates obtained assuming the decay has the form h log constant b the attenuation coefficient k as a function of period in the range 20 to 37 5 s in agreement with other estimates for paths across north america and for various paths from epicentres in china the study confirms that the surface wave decay across north america is much slower than that implied by the standard calibration functions used for computing surface wave magnitude combined with other published estimates the values of q 1 suggest that the average q 1 is lower q is higher for north america than on many other paths

flow velocity profiles in gravel bed rivers velocity measurements carried out in a rectangular laboratory flume having a gravel bed are presented the measurements are carried out for four different bed shapes characterized from different concentrations of coarser elements and for the two conditions of small and large scale roughness the analysis showed that the dean profile is usable to establish the velocity profile for both hydraulic conditions for small scale hydraulic condition an indirect estimate procedure of the coefficients of dean profile is proposed

mineralogy geochemistry and stratigraphy of the maslovsky pt cu ni sulfide deposit noril sk region russia implications for relationship of ore bearing intrusions and lavas we report new data on the stratigraphy mineralogy and geochemistry of the rocks and ores of the maslovsky pt cu ni sulfide deposit which is thought to be the southwestern extension of the noril sk 1 intrusion variations in the ta nb ratio of the gabbro dolerites hosting the sulfide mineralization and the compositions of their pyroxene and olivine indicate that these rocks were produced by two discrete magmatic pulses which gave rise to the northern and southern maslovsky intrusions that together host the maslovsky deposit the northern intrusion is located inside the tungusska sandstones and basalt of the ivakinsky formation the southern intrusion cuts through all of the lower units of the siberian trap tuff lavas including the lower nadezhdinsky formation demonstrating that the ore bearing intrusions of the noril sk complex post date that unit rocks in both intrusions have low tio2 and elevated mgo contents average mean tio2 1 and mgo 12 wt that are more primitive than the lavas of the upper formations of the siberian traps which suggests that the ore bearing intrusions result from a separate magmatic event unusually high concentrations of both hree dy yb er lu and y up to 1 2 and 2 1 ppm respectively occur in olivines fo79 5 and 0 25 nio from picritic and taxitic gabbro dolerites with disseminated sulfide mineralization thus accumulation of hree y and ni in the melts is correlated with the mineral potential of the intrusions the tio2 concentration in pyroxene has a strong negative correlation with the mg of both host mineral and mg of host rock sulfides from the northern maslovsky intrusion are predominantly chalcopyrite pyrrhotite pentlandite with subordinate and minor amounts of cubanite bornite and millerite and a diverse assemblage of rare precious metal minerals including native metals au ag and pd sn pd pt bi pb compounds and fe pt alloys sulfides from the southern maslovsky intrusion have 34s 5 6 up to 10 8 in two samples whereas the country rock basalt have 34s 3 4 implying there was no in situ assimilation of surrounding rocks by magmas

unique cu rich sulphide ores of the southern 2 orebody in the talnakh intrusion noril sk area russia geochemistry mineralogy and conditions of crystallization abstract we present new geochemical and mineralogical data from the southern 2 orebody located in the south western branch of the talnakh intrusion russia and composed of massive and disseminated sulphides the southern 2 orebody consists dominantly of chalcopyrite along with lesser pentlandite and subordinate cubanite bornite and pyrrhotite and differs from cu rich ores of the oktyabr sky deposit due to the absence of moikhukite talnakhite assemblages ores from the southern 2 orebody are highly enriched in copper nickel and platinum group elements pges cu up to 28 12 and 10 58 wt ni up to 6 29 and 2 45 wt and pt pd up to 220 and 173 ppm in the massive and disseminated ores respectively the ratios of cu ni 3 85 7 34 in massive and 2 64 6 58 in disseminated ores the ratios of the platinum to iridium group elements ppge ipge reaches more than 40000 these features indicate an extremely different degree of fractionation of the sulphide melt during the formation of ores the sequence of crystallization of the pge minerals pgms on the basis of textural information was as follows pt pd sn rustenburgite atokite pd cu sn stannopalladinite pt fe cu ni tetraferroplatinum pd ni as majakite pd as palladoarsenide pd pb bi zvyagintsevite polarite and pd5pb3 unnamed phase au cu pd tetra auricupride and auricupride au ag alloys this is consistent with experimental data on pge minerals the pgm assemblage was caused by the evolution of a significantly fractionated sulphide melt that was enriched in cu ni pt pd pb and au and as a result produced minerals with peculiar compositions e g cu rich stannopalladinite pb rich polarite ni rich palladoarsenide which do not occur in other ores furthermore pt fe cu ni alloys are abundant and sperrylite is absent which is a very common phase in all ores of the noril sk area the composition of pentlandite with ni ni fe ratios ranging from 0 48 to 0 68 indicates that it formed between 560 c ni poor to 500 c ni rich and 10 5 to 7 lgfs2 respectively the pgms and au minerals were formed at temperatures ranging from 550 to 225 c the specificity of sulphide with pgms association is due to the evolution of the cu rich and ni rich melt under elevated sulphur fugacity conditions the mechanism of filter pressing which precipitated sulphide drops at the bottom of the chamber and penetration of sulphide melts into the country rocks is supported by the same geochemical composition of disseminated and massive ores

theoretical background for continental and global scale full waveform inversion in the time frequency domain summary we propose a new approach to full seismic waveform inversion on continental and global scales this is based on the time frequency transform of both data and synthetic seismograms with the use of time and frequency dependent phase and envelope misfits these misfits allow us to provide a complete quantification of the differences between data and synthetics while separating phase and amplitude information the result is an efficient exploitation of waveform information that is robust and quasi linearly related to earth s structure thus the phase and envelope misfits are usable for continental and global scale tomography that is in a scenario where the seismic wavefield is spatially undersampled and where a 3 d reference model is usually unavailable body waves surface waves and interfering phases are naturally included in the analysis we discuss and illustrate technical details of phase measurements such as the treatment of phase jumps and instability in the case of small amplitudes the frechet kernels for phase and envelope misfits can be expressed in terms of their corresponding adjoint wavefields and the forward wavefield the adjoint wavefields are uniquely determined by their respective adjoint source time functions we derive the adjoint source time functions for phase and envelope misfits the adjoint sources can be expressed as inverse time frequency transforms of a weighted phase difference or a weighted envelope difference in a comparative study we establish connections between the phase and envelope misfits and the following widely used measures of seismic waveform differences 1 cross correlation time shifts 2 relative rms amplitude differences 3 generalized seismological data functionals and 4 the l2 distance between data and synthetics used in time domain full waveform inversion we illustrate the computation of frechet kernels for phase and envelope misfits with data from an event in the west irian region of indonesia recorded on the australian continent the synthetic seismograms are computed for a heterogeneous 3 d velocity model of the australian upper mantle with a spectral element method the examples include p body waves rayleigh waves and s waves interfering with higher mode surface waves all the kernels differ from the more familar kernels for cross correlation time shifts or relative rms amplitude differences the differences arise from interference effects 3 d earth s structure and waveform dissimilarities that are due to waveform dispersion in the heterogeneous earth

3 d electromagnetic imaging of a palaeozoic plate tectonic boundary segment in sw iberian variscides s alentejo portugal abstract in sw iberian variscides the boundary between the south portuguese zone spz and the ossa morena zone omz corresponds to a major tectonic suture that includes the beja acebuches ophiolite complex baoc and the pulo do lobo antiform terrane plat three sub parallel and approximately equidistant mt profiles were performed covering a critical area of this palaeozoic plate tectonic boundary in portugal the profiles running roughly along an ne sw direction are sub perpendicular to the main variscan tectonic features results of the three dimensional 3 d modelling of mt data allow to generate for the first time a 3 d electromagnetic imaging of the omz spz boundary which reveals different conductive and resistive domains that display morphological variations in depth and are intersected by two major sub vertical corridors these corridors coincide roughly with the ne sw messejana strike slip fault zone and with the wnw ese ferreira ficalho thrust fault zone the distribution of the shallow resistive domains is consistent with the lithological and structural features observed and mapped integrating the expected electrical features produced by igneous intrusions and metamorphic sequences of variable nature and age the development in depth of these resistive domains suggests that 1 a significant vertical displacement along an early tectonic structure subsequently re taken by the messejana fault zone in late variscan times has to be considered to explain differences in deepness of the base of the precambrian cambrian metamorphic pile 2 hidden syn to late collision igneous bodies intrude the meta sedimentary sequences of plat 3 the roots of baoc are inferred from 12 km depth onwards forming a moderate resistive band located between two middle crust conductive layers extended to the north in omz and to the south in spz these conductive layers overlap the iberian reflective body evidenced by the available seismic reflection data and are interpreted as part of an important middle crust decollement developed immediately above or coinciding with the top of a graphite bearing granulitic basement

turbulence characteristics in supercritical open channel flows effects of froude number and aspect ratio abstractan experimental investigation of supercritical uniform and gradually varied open channel flows is presented for a wide range of froude numbers and flume width to flow depth aspect ratios the instantaneous streamwise and vertical flow velocities were measured in a laboratory flume over the entire width using a two dimensional laser doppler anemometry 2d lda system to determine turbulence intensities and bed and reynolds shear stresses the mean velocity patterns show undulation across the flume indicating the presence of counterrotating secondary current cells these currents redistribute turbulence intensities and bed and reynolds shear stresses across the flume for aspect ratios 4 5 i e narrow open channel flow the velocity dip phenomenon is identified both in the streamwise velocity and the reynolds shear stress distributions for high aspect ratios i e wide open channel flow the strength of secondary currents diminish toward the flume center resulting in a 2d flow farther away

field measurements of secondary currents in straight rivers basic knowledge of turbulent structures in open channel flows are now available from accurate experimental data that were obtained using a laser doppler anemometer in laboratory flumes many of these experiments have however been conducted at moderate reynolds numbers therefore it is not yet clear whether such laboratory data of open channel turbulence can be applied to river turbulence at high reynolds numbers in this study velocity measurements of the biwako sosui river in kyoto and the aichi irrigation channel in nagoya have been conducted by making use of three component electromagnetic flow meters multicellular secondary currents were evident in a wide river whereas large scale free surface secondary currents associated with velocity dip phenomena were generated in a narrow river the features of such secondary currents in rivers could be explained by theory of turbulence and also they coincided well with the laboratory experiments and numerical calculations

an overview of chalcophile element contents of pyrrhotite pentlandite chalcopyrite and pyrite from magmatic ni cu pge sulfide deposits we have compiled the trace element concentrations in pyrrhotite pentlandite chalcopyrite and pyrite from magmatic ni cu pge ore deposits with the aim of understanding their petrogenesis and whether these minerals can be used as indicator minerals among the samples there are some of the most studied world class ni cu aguablanca duluth jinchuan noril sk talnakh kharaelakh sudbury voisey s bay and others and pge dominated bushveld lac des iles stillwater great dyke and penikat deposits crustal assimilation may be constrained using as se and sb se ratios in pentlandite the degree of interaction between the silicate and sulfide liquids r factor can be estimated by the content of highly chalcophile elements dsulf liq sil liq above 1000 in sulfide minerals the fractional crystallization of the sulfide liquid can be traced using se te ratios of pentlandite pyrite formed by exsolution from mss has higher rh ru ir and os than co existing pyrrhotite whereas pyrite formed by hydrothermal alteration of pyrrhotite inherits the rh ru ir and os contents of the pyrrhotite it replaced sulfide minerals are preserved in transported glacial cover and their trace element chemistry can be used to discriminate their source pentlandite from ni cu deposits has much lower rh and pd concentrations than those from pge dominated deposits pyrite from magmatic deposits has higher co sb and se as ratios relative to pyrite from hydrothermal deposits and chalcopyrite from magmatic deposits has much higher ni and lower cd concentrations than those from hydrothermal deposits

equilibrium and disequilibrium degassing of a phonolitic melt vesuvius ad 79 white pumice simulated by decompression experiments abstract equilibrium and disequilibrium degassing of a volatile phase from a magma of k phonolitic composition was investigated to assess its behavior upon ascent decompression experiments were conducted in ar pressurized externally heated pressure vessels at superliquidus temperature 1050 c in the pressure range 10 200 mpa using pure water as fluid phase all experiments were equilibrated at 200 mpa and then decompressed to lower pressures with rates varying from 0 0028 to 4 8 mpa s isobaric saturation experiments were performed at the same temperature and at 900 950 c to determine the equilibrium water solubility in the pressure range 30 250 mpa the glasses obtained from decompression experiments were analyzed for their dissolved water content vesicularity and bubble size distribution all decompressed samples presented a first event of bubble nucleation at the capsule melt interface homogeneous bubble nucleation in the melt only occurred in fast decompressed experiments 4 8 and 1 7 mpa s for p 100 mpa for these decompression rates high water over saturations were maintained until a rapid exsolution was triggered at p 150 mpa for slower rates 0 0028 0 024 0 17 mpa s the degassing of the melt took place by diffusive growth of the bubbles nucleating at the capsule melt interface this process sensibly reduced water over saturation in the melt preventing homogeneous nucleation to occur for decompression rates of 0 024 and 0 17 mpa s low water over saturations were attained in the melt gradually declining toward equilibrium concentrations at low pressures a near equilibrium degassing path was observed for a decompression rate of 0 0028 mpa s experimental data combined with natural pumice textures suggest that both homogeneous and heterogeneous bubble nucleations occurred in the phonolitic magma during the ad 79 vesuvius plinian event homogeneous bubble nucleation probably occurred at a depth of 3 km in response to a fast decompression of the magma during the ascent

sulfur isotope exchange and metal enrichment in the formation of magmatic cu ni pge deposits sulfur isotope measurements provide a useful means of evaluating the source of sulfur in magmatic cu ni pge deposits although low sulfur pge rich deposits e g j m reef of the stillwater complex merensky reef of the bushveld complex show little or no isotopic evidence for the involvement of crustally derived sulfur several high sulfur deposits e g noril sk duluth complex show strong evidence for contamination of mafic magmas by sulfur of crustal origin processes such as magma degassing or redox changes accompanying crystallization are ineffective in significantly modifying sulfur isotope signatures of sulfides that crystallize from immiscible liquids that exsolve from the mafic magmas for this reason 34s values are primarily dependent on sulfur source characteristics and variations can often be treated using a two component mixing approach however deposits such as those at noril sk and voisey s bay that appear to have formed in magma conduit systems present another possibility for modification of sulfur isotope signatures these deposits are thought to have been upgraded in metal tenor by reaction with uncontaminated mantle derived melts that traversed the accumulated sulfide on their way to the surface our calculations illustrate the efficiency of reactions that involve the exchange of fe for cu ni or pge in producing increases in the metal tenor of the accumulated sulfide sulfur isotope exchange between the crustally contaminated sulfide ore accumulation and sulfur of mantle origin may accompany chalcophile element exchange and is capable of masking or limiting the degree of isotopic evidence for the initial stage of ore genesis that involved crustal sulfur sulfur isotope exchange is distinct from the addition of sulfur in the form of immiscible sulfide droplets from a sulfide saturated magma to the accumulated sulfide although both additive mixing and exchange can lead to similar isotopic effects stable isotopic exchange provides a mechanism in addition to additive mixing that may lead to decoupling of different isotopic systems

assimilation of sulfate and carbonaceous rocks experimental study thermodynamic modeling and application to the noril sk talnakh region russia most of the intrusions in the noril sk talnakh region siberia are hosted in thick sedimentary sequences including abundant evaporitic and terrigenous sedimentary rocks three mafic ultramafic intrusions in this region contain unusually thick massive sulfide deposits which represent one of the world s largest economic concentrations of ni cu and pge the interaction of siberian magmas with sulfate and organic matter rich sedimentary rocks has been proposed as a possible mechanism for the origin of these exceptional sulfide deposits but the interaction process and the reaction paths have never been fully investigated here we clarify by both experimental petrology and thermodynamic modeling how sulfate and organic matter assimilation occur in mafic ultramafic magmas affecting magma composition crystallization and sulfide saturation interaction experiments were conducted at conditions relevant to the emplacement of noril sk type intrusions 1200 c 80 mpa to simulate the assimilation of sulfate and or organic compounds by ultramafic magmas we used a picrite from noril sk1 intrusion and coal and anhydrite from the area as starting materials the experimental results show that the incorporation of anhydrite into the magma occurs by chemical dissolution in the melt which increases the magma s sulfur content but suppresses sulfide saturation and reduces olivine crystallization extreme assimilation leads to sulfate saturation in the magma and high dissolved sulfur contents of 0 9 0 1 wt s conversely coal assimilation promotes sulfide segregation and magma crystallization while decreasing the dissolved h2o content of the melt and increasing the amount of coexisting fluid phase we also employed gas melt thermodynamic calculations to quantify the effect of these assimilations on the redox conditions and the s content of the magma and investigate the role of temperature pressure and initial gas content of the magma in the assimilation process we quantify how sulfate assimilation strongly oxidizes the magma and increases its s content both effects are intensified by increasing pressure from 50 to 100 mpa in this study decreasing temperature from 1350 to 1200 c in this study and decreasing amounts of fluid phase initially coexisting with the magma from 2 to 0 wt the interaction with organic matter ch in this study induces a strong reduction of the magma even for extremely low degrees of assimilation few tenths of wt and the dehydration of the melt we therefore suggest that in the noril sk talnakh district 1 additional s was supplied to mantle derived magmas by the assimilation of evaporitic rocks and was transported during magma ascent in the form of dissolved oxidized s 2 a substantial reduction of the magma inducing sulfide segregation and important crystallization then occurred due to the interaction with carbonaceous sediments this mechanism can potentially produce massive sulfide deposits by important sulfate assimilation locally higher than 3 wt caso4 and minor organic matter assimilation few tenths of wt ch however if one of the two steps does not occur or the assimilation in 1 is not large enough disseminated sub economic or no sulfide deposits are produced we conclude that exceptional conditions favoring substantial assimilation of sediments are needed to generate exceptional ore deposits like those of the noril sk talnakh district

p wave amplitudes in a 3 d earth summary evidence is presented here that p wave amplitudes contain additional information on the earth s heterogeneity and must be considered in future tomographic interpretations we analyse the reliability and the variance of teleseismic p wave amplitudes recorded at well calibrated broadband global seismic network gsn stations from intermediate to deep earthquakes depth 46 km the dataset contains 217 earthquakes with mb between 5 6 and 7 6 from 1993 january to 2000 may using pairs of closely located events with similar focal mechanisms as well as data recorded at the closely spaced moma seismic array we demonstrate the consistency of observations we deduce that the magnification of the gsn instruments generally drifts by at most 2 per cent per year and likely much less p wave amplitudes have variations due to focusing defocusing with a standard deviation of at least 38 per cent this reduces to 19 per cent if only periods in excess of 10 s are considered tomographic p wave models with mantle velocity anomalies of the order of 1 per cent are unable to reproduce such large variations

anhydrite solubility in differentiated arc magmas abstract the solubility of anhydrite in differentiated arc magmas was experimentally studied at 200 mpa and 800 1000 c over a range of oxygen fugacities from 0 5 log units above the ni nio buffer to the hematite magnetite buffer anhydrite is stable only at oxidizing conditions fo2 re reo2 whereas sulfides only form under reducing conditions the solubility of anhydrite in the melt ultimately regulates the amount of sulfur available to partition between melt and fluid phase during the eruption at oxidizing conditions the solubility product of anhydrite increases with temperature nbo t and melt water content we provide a new calibration of the anhydrite solubility product ksp xcao xso3 which reproduces all available experimental data with greatly improved accuracy ln k sp anhydrite 8 95 146 5 nbo t 2 696 10 4 t k 19 72 nbo t 10 4 t k 0 409 h 2 o wt in this equation the molar fractions xcao and xso3 in the melt as well as the number of non bridging oxygen atoms per tetrahedron nbo t are calculated on an anhydrous basis h2o refers to the melt water content t is temperature in kelvin we apply our model to estimate the sulfur yield of some recent volcanic eruptions and we show that the sulfur yield of the 1991 mt pinatubo dacite eruption was unusually large because only a small fraction of the sulfur was locked up in anhydrite in general high sulfur yields are expected when anhydrite solubility in the melt is high i e for somewhat depolymerized melts for rhyolitic systems most of the available sulfur will be locked up in anhydrite so that even very large eruptions may only have a small effect on global surface temperatures our model therefore allows improved predictions of the environmental impact of explosive volcanic eruptions

small scale changes of core mantle boundary reflectivity studied using core reflected pcp abstract short period pcp phases from earthquakes in the western aleutians recorded at the canadian yellowknife array yka sample the core mantle boundary cmb beneath the alaskan kenai peninsula and the cook inlet the pcp to p amplitude ratios for these events show large variability with some amplitude ratios more than an order of magnitude larger than predicted by radial earth models such as iasp91 or prem the amplitude ratios vary laterally with pcp core mantle boundary reflection points showing a 1 region with exceptionally large amplitude ratios it is likely that the variability in relative pcp amplitudes is due in large part to cmb topography other mechanisms such as radiation pattern mantle attenuation focusing and defocusing and core mantle boundary velocity and density perturbations could cause variations on scale lengths of less than a degree as found in this study but are unable to produce variations as large as those we observe

turbulent structure in compound open channel flows an investigation of three dimensional 3 d turbulent structure including turbulence driven secondary currents in compound open channel flows is a very important topic in hydraulic and river engineering as well as in fluid mechanics in this study accurate measurements in fully developed compound open channel flows are conducted by means of a fiber optic laser doppler anemometer flda secondary velocities can be measured very accurately with the present 3 d measurement system the characteristics of compound open channel flows are recognized in the junction region between the main channel and flood plain whereas the characteristics of rectangular open channel flows are observed in a region near the sidewall of the main channel strong inclined secondary currents which are associated with a pair of longitudinal vortices are generated in the junction region between the main channel and the flood plain the primary mean velocity field is directly influenced by these secondary currents turbulence i

shear wave splitting continental keels and patterns of mantle flow in this study we investigated the origin of seismic anisotropy in the mantle beneath north america in particular we evaluated whether shear wave splitting patterns in eastern north america are better explained by anisotropy caused by lithospheric deformation anisotropy due to mantle flow beneath the lithosphere or a combination of both we examined new measurements of shear wave splitting from the missouri to massachusetts broadband seismometer array moma the north american mantle anisotropy and discontinuity experiment nomad as well as splitting parameters from several previous studies we developed a simple finite difference model that approximates mantle flow around a complex three dimensional continental lithospheric keel to evaluate potential anisotropy from mantle flow beneath the lithosphere in eastern north america we compared shear wave splitting observations to predicted splitting parameters calculated using this mantle flow model our results indicate that a significant portion of observed shear wave splitting in eastern north america can be explained by mantle flow around the continental keel however shear wave splitting patterns in a few regions of eastern north america indicate that a component of lithospheric anisotropy must exist particularly in regions containing the largest keel thicknesses for eastern north america as well as for splitting observations in australia europe and south america we favor a model in which anisotropy is controlled by a combination of both lithospheric deformation and subcontinental mantle flow

incomplete self similarity and flow velocity in gravel bed channels velocity measurements previously carried out using both a miniature current flowmeter and an acoustic doppler velocimeter are used to verify the applicability of the incomplete self similarity theory to deduce the velocity profile in a gravel bed channel then for the velocity profiles having the maximum value below the free surface and for the s shaped profiles the power velocity distribution is corrected using a new divergence function for each value of the depth sediment ratio the nondimensional friction factor parameter is calculated by integration of the measured velocity distributions in the different verticals of the cross section finally a semilogarithmic flow resistance equation is empirically deduced

textural development in sulfide matrix ore breccias in the voisey s bay ni cu co deposit labrador canada abstract magmatic ni cu sulfide ores at voisey s bay contain complex assemblages of extremely heterogeneous rocks these range from polymict breccias with rock fragments in sulfide rich and or sulfide poor matrices to heterogeneous vari textured gabbros with rapid short range variations in grain size and content of hydrous phases rock fragment populations in the breccias include endogenous olivine gabbros cumulate and non cumulate and cumulate peridotites along with extensively depleted plagioclase hercynite gneisses interpreted as restites from extensive partial melting of country rock quartzo feldspathic paragneisses using a combination of desk top microbeam xrf mapping at cm scale and 3d x ray tomography we show that both sulfide poor and sulfide rich breccias comprise heterolithic assemblages of clasts within a matrix of olivine gabbro this matrix is characterised by an interconnected 3d framework of plagioclase crystals highly variable in grain size at mm to cm scale with interstitial olivine and poikilitic clinopyroxene and is texturally indistinguishable from clast free olivine gabbro sulfide forms interconnected networks at cm to dm scale and possibly larger much of the plagioclase developed by outgrowth from the margins of paragneiss xenoliths when the porosity was occupied by silicate melt the observed range of textures is explained by a model of percolation of molten sulfide through variably crystalline inter clast matrix displacing the silicate melt to leave the refractory plagioclase olivine or in some cases plagioclase only component now entirely within a sulfide matrix the process is analogous to that believed to have formed interspinifex ore in komatiite hosted deposits biotite rims on plagioclase enclosed in sulfide are interpreted as the result of reaction between plagioclase olivine and a hydrous component derived from the sulfide melt itself with a possible component of migrating residual silicate melt wicking along sulfide silicate contacts this sulfide infiltration model offers an alternative to the current model for upward emplacement of a slurry of silicate melt sulfide melt and breccia fragments as a late stage injection into the dyke sill complex the preserved range of textures is interpreted as being due to gravity driven percolation of sulfide liquid through a pre existing partially molten intrusion breccia in this model the breccia serves as a physical trap site accumulating downward migrating sulfide liquid however the invariable close mutual association of sulfide and rock fragments at voisey s bay implies a common derivation

flow structures in the vicinity of a submerged boulder within a boulder array abstractboulders are widely used in fish habitat enhancement structures or fish passes this study provides a detailed measurement of mean and turbulent flow around a boulder in a boulder array und

seismic properties of the inner core boundary from pkikp p amplitude ratios a recent study of pkikp pcp amplitude ratios found surprisingly low values for the change in density icb 0 3 g cm3 and shear velocity sicb 2 0 km s across the inner core boundary icb however because the data set was limited to small source receiver distances 50 there was a significant trade off between the two parameters with higher values in one parameter nearly compensated by higher values in the other in this study we augment the existing pkikp pcp data set with new observations of pkikp p amplitude ratios at larger distances 50 90 and jointly model the two data sets considering assumptions in the modeling and observational errors we estimate icb 0 52 0 24 g cm3 and sicb 2 82 0 32 km s these values can be reconciled with the slightly higher values obtained from normal mode analysis if the outermost inner core is either structurally or chemically distinct from the bulk of the inner core the new pkikp p amplitude ratios show dramatic variation but are geographically coherent this suggests that significant lateral heterogeneity is present at or just below the icb

sulfur isotopic studies of continental flood basalts in the noril sk region implications for the association between lavas and ore bearing intrusions previous studies of both ore and non ore bearing intrusives in the permo triassic flood basalts of the siberian platform in the noril sk area have shown that high grade ni cu platinum group elements pge mineralization is associated with anomalously high 34s values of 8 to 12 in addition several researchers have proposed that observed depletions in the cu ni and pge content of basaltic lavas of the nadezhdinsky nd formation are related to diffusional exchange with and upgrading in metal tenor of sulfides in the volcanic conduit system sulfur isotopic studies of the lavas at noril sk were initiated to determine if interaction with crustally derived sulfur in the conduit system was evident and if the nd lavas in particular were characterized by an anomalous isotopic signature 34s values of the lavas range from 4 5 to 8 7 vienna canon diablo troilite vcdt with s concentrations from 40 to 1373 ppm the majority of 34s values range from 0 to 4 and are similar to those from s poor intrusions in the noril sk area although textural data are not supportive of early sulfide saturation and the presence of immiscible sulfide droplets in the lavas recrystallization may have erased expected mineralogical and textural evidence mineralogical data indicate that hydrothermal alteration of the lavas has occurred but s redistribution has been restricted to localized areas and 34s values have not been affected the relatively low s concentrations of the lavas are thought to be due in large part to degassing of the lavas in the shallow conduit system and during eruption our calculations are consistent with the premise that degassing of basaltic magmas at temperatures in excess of 900 c at qfm leads to only minor 34s depletion of sulfur remaining in the melt and decreases in 34s values of less than 2 at 90 degassing for this reason all lavas with 34s values in excess of 2 require a contribution of 34s enriched country rock sulfur because of the high s content and 34s value 16 20 of evaporites in the country rocks at noril sk contamination of less than 0 5 is required to explain the most 34s enriched lavas the nd lavas have an average 34s of 2 9 but show no difference in s isotopic composition relative to the other lavas suggesting that metal depletion involved only limited s transfer or that exchange between mantle derived s and s of crustal origin buffered 34s values to less than 5 anomalously positive 34s values similar to those of the ore bearing intrusives in the noril sk region are not consistently found in low s rocks either lavas or intrusives although the mechanism for the derivation of sulfide in the ore bearing intrusions remain speculative it is clear that the formation of sulfide ores characterized by high metal tenors proceeded only in the presence of sulfur of crustal origin

droplets and bubbles solidification of sulphide rich vapour saturated orthocumulates in the norilsk talnakh ni cu pge ore bearing intrusions

magmatic anhydrite sulfide assemblages in the plumbing system of the siberian traps we report the first discovery of magmatic anhydrite sulfide assemblages in a subvolcanic intrusion associated with the siberian traps the 34s values of anhydrite and coexisting sulfide crystals analyzed by ion probe are 18 22 and 9 11 respectively more than 50 of the total sulfur in the intrusion is estimated to derive from marine evaporites in the footwall strata the contaminated magma was highly oxidized and able to dissolve up to one order of magnitude more sulfur than pure mantle derived basaltic magma such contaminated magma if erupted would have released far more so2 into the atmosphere than is generally appreciated

geology and geochemistry of intrusions and flood basalts of the noril sk region ussr with implications for the origin of the ni cu ores geochemical studies indicate that five principal magma types characterize the 3 8 km vertical thickness of flood basalt of the noril9sk region from base to top these are 1 a fractionated type with alkalic affiliations ivakinsky and syverminsky 2 an ni rich suite including picritic basalt gudchichinsky 3 a primitive but ni depleted suite with fiat rare earth element ree profiles and also including picritic basalts tuklonsky 4 a light ree enriched crustally contaminated suite lower nadezhdinsky nd 1 above 4 there is a transitional suite upper nadezhdinsky nd 2 and morongovsky mr 1 and mr 2 which is overlain by the fifth type a second primitive suite without picrites mokulaevsky similar but not identical in its chemistry to the tuklonsky type this is followed by tuffs and basalts of the kharayelakhsky kumginsky and samoyedsky suites which are largely composed of similar uncontaminated tholeiitic magma the latter three suites have not been studied by us intrusions of the region fall into five main groups 1 alkalic intrusions 2 ti rich dolerite dikes 3 dolerite sills and dikes 4 differentiated bodies not related to ore junctions and 5 differentiated bodies related to ore junctions the ni cu ores are associated with ni and cr rich type 5 olivine rich intrusions with flat ree profiles that are geochemicaly similar to the mokulaevsky magma light ree enriched ni and cr poor olivine rich type 5 intrusions with uneconomic mineralization occur closely associated with the strongly mineralized variants and resemble geochemically the basalts transitional between the lower nadezhdinsky and upper morongovsky they are cut by the strongly mineralized bodies indicating that the latter are of late morongovsky to mokulaevsky age the mineralized intrusions are associated with about 1 5 to 1 10 of their mass in sulfides this is a factor of 25 to 50 more than could have been carried in solution and deposited by in situ liquation from the magma of these intrusions the platinum group element pge concentrations in the ores require that the sulfides giving rise to them equilibrated with 15 to 200 times more magma than is represented by the intrusions much of the ore is very massive and crosscuts the host intrusions the sequence of igneous activity and mineralization in the immediate vicinity of noril9sk and talnakh from the base of the nadezhdinsky upward is thus interpreted to be 1 extrusion of highly crustally contaminated ni and cu poor basalt 2 extrusion of a series of basalt flows each progressively less contaminated and less ni and cu depleted than the preceding one accompanied by intrusion of contaminated ni depleted magma with weak mineralization 3 extrusion of uncontaminated ni and cu rich basalt accompanied by intrusion of uncontaminated ni rich magma with strong mineralization followed very closely by introduction of associated massive ore and 4 continued extrusion of ni and cu rich basalt it is proposed that crustal contamination of the original ni and cu rich magma occurred at the top of a vertically extensive fault controlled magma chamber and caused segregation of immiscible sulfides with a low r factor these depleted this magma in chalcophile elements and settled deeper in the chamber as they settled they reacted with less contaminated magma scavenging additional chalcophile elements they finally came to rest near the base of the chamber to form a zone of sulfide and thus chalcophile element enriched magma eruption and in some instances intrusion of progressively stratigraphically lower less contaminated and thus less depleted layers in the chamber gave rise to the observed sequence of basalts and intrusions the answer to the strong enrichment in ni cu and pge associated with the ore bearing intrusions is that these metals came from the magma that is now represented by the depleted basalts

an analysis of p wave amplitudes recorded by seismological stations in the ussr summary short period p wave amplitudes at soviet seismic stations are analysed to determine an amplitude distance curve in the range 0 180 from the ussr station amplitude terms corrected for crustal amplification effects are determined from seismic sources located between 30 and 90 a relationship between these station terms and regional p wave speed and regional heat flow is determined and is found to be in close agreement with similar observations in north america station amplitude terms were found to be reasonably uniform across the continental portion of the ussr but the baikal rift valley is characterized by very low p wave amplitudes and is the most significant feature discernible from the p wave amplitude terms

microearthquake seismicity at the intersection between the kazerun fault and the main recent fault zagros iran summary seismicity and fault plane solutions of earthquakes at the intersection between the main recent fault a right lateral strike slip fault that bounds the zagros to the ne and the kazerun fault system another right lateral zone that crosses the zagros show slip to be partitioned into nearly pure strike slip at shallow depths and nearly pure thrust slip below 12 km such slip partitioning is commonly observed where oblique convergence occurs but in general faults of different styles lie adjacent to one another not at different depths with one below the other we provide evidence for this partitioning in a microearthquake study in which we deployed a temporary network of 29 seismographs for 7 weeks we located no activity north of the main zagros reverse fault mzrf which separates the zagros fold belt from central iran most earthquakes occurred between the northern termination of the kazerun fault and the mzrf but not near to known major faults activity is limited to the upper crust between 2 and 16 km most of the focal mechanisms show strike slip faulting dextral if the ns striking plane is the active plane but a few for the deepest events show reverse faulting distributed between the kazerun fault and the mzrf with p axis trending consistently ns this partitioning of the deformation with depth suggests that the brittle upper crust deforms by slip on pre existing faults that strike obliquely but that the lower crust accommodates the shortening by reverse faulting we infer that the deformation in the upper part of the crust reflects a stiffer medium in which pre existing faults localize the deformation the largest event recorded during this experiment located at the same place as the destructive 1977 naghan earthquake mw 5 9 348 victims shows reverse faulting likely related to the dopolan high zagros fault the crustal thickness deduced from receiver function analysis does not show a marked difference across the kazerun fault which suggests a pure strike slip motion on the fault

a model for the ni cu pge ores of the noril sk region and its application to other areas of flood basalt five principal magma types characterize the 3 8 km vertical thickness of flood basalt of the noril9sk region from base to top these are 1 a high tio 2 type with alkalic affiliations ivakinsky and syverminsky suites 2 a tio 2 rich picrite bearing magma gudchichinsky suite 3 a picrite bearing tio 2 poor magma tuklonsky suite 4 a crustally contaminated tio 2 poor magma lower nadezhdinsky suite and 5 a picrite free magma mokulaevsky kharayelakhsky kumginsky and samoyedsky suites similar but not identical in its chemistry to the tuklonsky and separated from the lower nadezhdinsky by transitional suites upper nadezhdinsky and morongovsky the ni cu ores are associated with olivine rich intrusions that are geochemically similar to the mokulaevsky magma they are associated with about 1 15 to 1 10 of their mass in pge rich sulfides this requires that these sulfides equilibrated with 15 to 200 times more magma than is represented by the intrusions themselves following the model of naldrett et al 1992 it is proposed that crustal contamination of the original tuklonsky type magma occurred at the top of a vertically extensive fault controlled magma chamber and caused segregation of immiscible sulfides with a low r factor these depleted this magma in chalcophile elements and settled deeper in the chamber as they settled they reacted with less contaminated magma scavenging additional chalcophile elements they finally came to rest near the base of the chamber to form a zone of sulfide and thus chalcophile element enriched magma eruption and in some instances intrusion of progressively stratigraphically lower less contaminated and thus less depleted layers in the chamber gave rise to the observed sequence of basalts and intrusions the answer to the strong enrichment in ni cu and pge associated with the ore bearing intrusions is that these metals came from the magma that is now represented by the basalt magma with which the sulfides have come into contact and which shows chalcophile element depletion key metallogenic characteristics of the noril9sk region are 1 a hot region in the mantle giving rise to vast amounts of basalt 2 continental scale rifting 3 major faults serving as controls for extrusive and intrusive magmatism 4 crustal contamination of magma 5 chalcophile element depletion of contaminated magma 6 intrusion of magma that has inherited sulfide removed from the depleted magma and 7 the presence of evaporites in the sedimentary sequence underlying the basalts the simplest way to recognize chalcophile element depletion is to plot ni mgo vs mg number at mg mg 0 9fe total a strong indication that basalts have undergone crustal contamination is the correlation of high la sm ratios with high sio 2 contents the lake superior region shows many of the key metallogenetic characteristics of the noril9sk region including continental rifting a triple junction huge thicknesses of basalt and cu ni sulfide bearing intrusions duluth complex crystal lake gabbro some of the keweenawan basalts of the region show ni depletion correlated with chalcophile element depletion the region is an example of the potential application of the noril9sk model to exploration

upper mantle s velocity structure of north america we have inverted fundamental and higher mode rayleigh waveforms from 685 vertical component broadband seismograms with wave paths over north america to obtain an image of the upper mantle s velocity structure down to 660 km among the well resolved features of the new model are 1 a high velocity root beneath the north american craton which extends no deeper than 250 km except near the archean core of the craton where depths of 350 km are reached 2 a weak band of low velocity along the eastern margin of the north american craton which reaches into the transition zone 3 a low velocity slab window beneath the western united states down to a depth of 300 km 4 areas of low uppermost mantle velocity beneath the cascade volcanoes the yellowstone hotspot track the colorado plateau the sierra madre occidental and the grabens bordering the jalisco block and 5 a pronounced band of high velocities in the transition zone coinciding with the expected location of the subducted trailing fragments of the farallon plate we introduce several improvements to the method of partitioned waveform inversion which was used to compute the new model rather than to correct for an estimated depth to the mohorovicic discontinuity we leave the crustal thickness as a free though yet poorly resolved parameter in the inversion we also improve the windowing and filtering operator used to select uncontaminated waveforms

assessment of tomographic mantle models using spectral element seismograms summary we investigated the agreement between real seismograms and those predicted by long wavelength mantle models by looking at phase and amplitude differences we computed full synthetic seismograms using a spectral element method together with 3 d mantle models and the appropriate crustal model on top we selected differently damped mantle models to see the effect of regularization on the computed seismograms to check the phase agreement we measured time shifts between the real and synthetic surface waves and body wave phases such as p s and ss using a cross correlation technique we also compared the amplitudes of the real and synthetic seismograms to understand how well the models explain not only the phases but the whole waveforms 3 d mantle models improve the phase agreement of surface waves in particular the remaining misfit however is still so large that we cannot distinguish between different tomographic models we suggest that this is mainly due to an imperfect modelling of the crust and or source location if body waves are included which have to be addressed in future inversions amplitude mismatches are large regardless which 3 d mantle model is used we observe that 3 d scattering or focusing defocusing effects can only explain half of the surface wave amplitudes whereas body wave amplitudes are dominated by scattering effects 1 d q models particularly in the crust and upper mantle strongly affect surface wave amplitudes and have to be modelled properly

transport of metals and sulphur in magmas by flotation of sulphide melt on vapour bubbles emissions of sulphur 1 2 and transition metals 3 4 from magmas in the shallow crust have global impacts on human society by affecting climate after volcanic eruptions 5 6 and by forming giant copper and gold ore deposits which are massive anomalies of sulphur as well as of the ore metals themselves 3 4 7 8 these emissions vastly exceed the amounts that could have been derived from the associated magmas themselves 2 intrusion of denser hotter vapour and sulphide saturated magma beneath the cooler and more buoyant bodies that are finally erupted is the most probable source of the excess sulphur and metals in eruptive or hydrothermal systems 1 4 9 10 however the mechanism for the selective upward transfer of sulphur and metals remains poorly understood because their main carrier phase sulphide melt is dense and is generally assumed to settle to the bottoms of magma bodies here we show by experimental observation and by gas speciation and mass balance models that such transfers may be achieved by the flotation of compound drops 11 comprising droplets of sulphide melt attached to vapour bubbles by proposing and demonstrating the feasibility of a novel physical mechanism for upward mobility of sulphide liquids our work provides a mechanism for massive atmospheric releases of sulphur and contradicts widely held assumptions that dense sulphide liquids rich in sulphur copper and gold will remain sequestered in the crust

compositional variations of olivine and sulfur isotopes in the noril sk and talnakh intrusions siberia implications for ore forming processes in dynamic magma conduits olivine from the noril sk i main and northwestern talnakh ore bearing intrusions in the noril sk region occurs as inclusions discrete grains and poikilitic crystals the original compositions of olivine inclusions have been well preserved by their host oikocrysts from reaction with interstitial silicate and sulfide liquids in contrast the compositions of discrete and poikilitic olivine crystals have been variably modified by reequilibration with trapped silicate and sulfide liquids there are abrupt changes in the contents of nickel in olivine inclusions 500 1 500 ppm between different rock units in all three intrusions which indicates that the different rock units in these intrusions are not related to each other via in situ differentiation of a common parental magma but rather are consistent with separate pulses of magma with variable degrees of differentiation possibly involving olivine crystallization and assimilation of siliceous crustal material in a staging chamber the 34s values of the samples with high sulfur contents 800 ppm sulfur from all three ore bearing intrusions vary between 8 and 14 per mil two sulfur poor samples 600 ppm sulfur from the northwestern talnakh intrusion yield 34s values of 1 5 and 3 6 per mil these values are similar to the values of the sulfur poor rocks from the ore barren intrusions in the region and illustrate the fact that high sulfur contents couple with increasing 34s values such a relationship is consistent with the addition of crustally derived 34s enriched sulfur to the magma of the ore bearing intrusions in contrast to other models of sulfide segregation in closed systems we propose that sulfide segregation occurred in an open system and the magma involved was undersaturated in sulfur and undepleted in chalcophile elements we envision that the 34s enriched sulfur was introduced via circulating fluids that transported sulfur from evaporite in the underlying sedimentary sequence to the magma in a dynamic magma conduit the immiscible sulfide liquids that segregated during sulfur contamination settled down in the wider parts of the conduit as the magma continued to travel successive pulses of new magma entered the conduit reacted with the early sulfide and displaced much of the early magma in the conduit the ore bearing intrusions are thought to have crystallized within the wider parts of the conduits and their voluminous sulfide poor peripheral sills represent some if not all of the magma that flowed out of the conduits

analysis of seismicity and micro seismicity associated with the october november 2010 sampeyre swarm southwestern alps abstract the study presents a detailed analysis of the swarm that occurred in the area surrounding sampeyre piedmont italy during the period october november 2010 the crisis caught the attention of seismologists because of its intense seismic productivity that has never been observed in the past during the swarm 550 earthquakes were recorded and located by the regional seismic network of northwestern italy rsni http www distav unige it geofisica in the study area however including the micro seismicity mainly earthquakes of magnitude lower than 0 detected through an sta lta short term average long term average based algorithm the number of events goes up to approximately 3250 among all these events approximately two hundred exceeded a local magnitude m l of 1 0 but only two earthquakes exceeded m l 3 0 reaching up to m l 3 2 following a general description of the swarm evolution the study presents the results of a waveform similarity analysis and double difference relocation aimed at identifying groups of earthquakes belonging to common genetic sources a statistical analysis of the resulting earthquake families has revealed a variation of the scaling exponent b value of the gutenberg and richter size frequency model with depth in particular our results have evidenced a slightly higher b value at shallower depths where a distinct family of earthquakes was identified through seismogram cross correlation this may reflect variability in the distribution of fractures in the rock volume involved in the swarm

remote monitoring of volumetric discharge employing bathymetry determined from surface turbulence metrics current methods employed by the united states geological survey usgs to measure river discharge are manpower intensive expensive and during high flow events require field personnel to work in dangerous conditions indirect methods of estimating river discharge which involve the use of extrapolated rating curves can result in gross error during high flow conditions due to extrapolation error and or bathymetric change our goal is to develop a remote method of monitoring volumetric discharge that reduces costs at the same or improved accuracy compared with current methods while minimizing risk to field technicians we report the results of large scale particle image velocimetry lspiv and acoustic doppler velocimetry adv measurements conducted in a wide open channel under a range of flow conditions i e channel aspect ratio b h 6 6 31 9 reynolds number reh 4 950 73 800 and froude number fr 0 04 0 46 experiments were carried out for two different channel cross sections rectangular and asymmetric compound and two bathymetric roughness conditions smooth glass and rough gravel bed the results show that the mean surface velocity normalized by the depth averaged velocity the velocity index decreases with increasing h where is the boundary layer displacement thickness and that the integral length scales l11 1 and l22 1 calculated on the free surface vary predictably with the local flow depth remote determination of local depth averaged velocity and flow depth over a channel cross section yields an estimate of volumetric discharge

atmospheric oxygenation caused by a change in volcanic degassing pressure around two and a half billion years ago following the end of the archaean eon the atmosphere turned from anoxic to weakly oxic in what is known as the great oxidation event using a model of volcanic degassing gaillard et al demonstrate that a preceding period of continental crust formation may have been the trigger they propose that as continents emerged and volcanoes became increasingly subaerial rather than submarine magmatic volatiles were degassed at lower pressures leading to a progressive oxidation of the gases released this shift to a release of sulphur as sulphur dioxide rather than as hydrogen sulphide could then have fed marine sulphate reduction and the eventual oxygenation of earth s atmosphere the precambrian history of our planet is marked by two major events a pulse of continental crust formation at the end of the archaean eon and a weak oxygenation of the atmosphere the great oxidation event that followed at 2 45 billion years ago this oxygenation has been linked to the emergence of oxygenic cyanobacteria1 2 and to changes in the compositions of volcanic gases3 4 but not to the composition of erupting lavas geochemical constraints indicate that the oxidation state of basalts and their mantle sources has remained constant since 3 5 billion years ago5 6 here we propose that a decrease in the average pressure of volcanic degassing changed the oxidation state of sulphur in volcanic gases initiating the modern biogeochemical sulphur cycle and triggering atmospheric oxygenation using thermodynamic calculations simulating gas melt equilibria in erupting magmas we suggest that mostly submarine archaean volcanoes produced gases with so2 h2s 1 and low sulphur content emergence of the continents due to a global decrease in sea level and growth of the continental crust in the late archaean then led to widespread subaerial volcanism which in turn yielded gases much richer in sulphur and dominated by so2 dissolution of sulphur in sea water and the onset of sulphate reduction processes could then oxidize the atmosphere

role of degassing of the noril sk nickel deposits in the permian triassic mass extinction event the largest mass extinction event in earth9s history marks the boundary between the permian and triassic periods at circa 252 ma and has been linked with the eruption of the basaltic siberian traps large igneous province slip one of the kill mechanisms that has been suggested is a biogenic methane burst triggered by the release of vast amounts of nickel into the atmosphere a proposed ni source lies within the huge noril sk nickel ore deposits which formed in magmatic conduits widely believed to have fed the eruption of the slip basalts however nickel is a nonvolatile element assumed to be largely sequestered at depth in dense sulfide liquids that formed the orebodies preventing its release into the atmosphere and oceans flotation of sulfide liquid droplets by surface attachment to gas bubbles has been suggested as a mechanism to overcome this problem and allow introduction of ni into the atmosphere during eruption of the slip lavas here we use 2d and 3d x ray imagery on noril sk nickel sulfide combined with simple thermodynamic models to show that the noril sk ores were degassing while they were forming consequent bubble riding by sulfide droplets followed by degassing of the shallow sulfide saturated and exceptionally volatile and cl rich slip lavas permitted a massive release of nickel rich volcanic gas and subsequent global dispersal of nickel released from this gas as aerosol particles

characteristics of loose rough boundary streams at near threshold laboratory experimental results on the turbulent flow characteristics measured by an acoustic doppler velocimeter over loose rough boundaries at the near threshold of motion are reported the primary endeavor was to investigate the response of the turbulent flow field having zero pressure gradient to the uniform gravel beds at the near threshold of motion with reasonably wide range of relative roughness e h 0 02 e h 0 15 where e nikuradse s equivalent roughness and h flow depth five uniform gravel sizes ranging from 4 1 to 14 25 mm were used in the experiments the vertical distributions of time averaged velocity turbulence intensities and the reynolds stress were measured and analyzed the variation of the mixing length is considerably linear with the depth within the inner layer whose thickness is 0 23 times the boundary layer thickness and the von karman constant is obtained as 0 35 the boundary shear stresses were determined by three independent methods such as using the logarith

body wave amplitude patterns and upper mantle attenuation variations across north america summary a broad band amplitude study of p and sh waves from deep south american events recorded at wwssn stations in the united states provides constraints on upper mantle variations in attenuation the events were selected to minimize contamination due to source complexity radiation pattern and source structure the prevalent feature in the short and longperiod bands is that the sh amplitudes show the same regional variations as the p amplitudes with the regional variations of short periods being similar but enhanced relative to the variations at long periods the amplitudes show some systematic regional difference between the east coast and rocky mountain provinces and both short and long periods are enhanced at the gulf coast and midwestern stations probably due to thick sedimentary bed receiver structure since detailed receiver structures for individual stations are poorly known we used the working hypothesis that the regional amplitude patterns are caused by lateral variations in upper mantle attenuation both a constant q and a frequency dependent attenuation operator were considered with the relative amplitudes and waveforms in short and long period bands used to estimate the acceptable range of at in the constant q model or the acceptable range of the parameter r which describes the high frequency roll off of the absorption band in the frequency dependent model time domain modelling indicates that the short period p and sh amplitudes and waveforms in the 1 10s period range do not unambiguously demand frequency dependent attenuation allowing for the uncertainty in source frequency content and long period absorption band amplitude the short period p amplitudes can be fit with a range in at 0 5 s or a range in r from 0 001 to 0 25s with either single parameter variation consistent with the general short period sh amplitude behaviour a technique for determining the absolute value of t and possible r values appropriate for the 5 20s band was applied to selected data a value of t 0 8 s and small 7 were found for travel paths from the deep events to north america and lower t or large r values were found for paths to southern african stations longperiod amplitude variations cannot be explained by frequency dependent

geochemistry of the siberian trap of the noril sk area ussr with implications for the relative contributions of crust and mantle to flood basalt magmatism the sequence investigated of the siberian trap at noril sk ussr consists of at least 45 flows that have been divided into six lava suites the lower three suites consist of alkalic to subalkalic basalts the ivakinsky suite overlain by nonporphyritic basalts the syverminsky suite and porphyritic and picritic basalts the gudchikhinsky suite the upper three suites are tholeiitic the uppermost 750 m of dominantly non porphyritic basalt belong to the mokulaevsky suite and are characterized by a nearly constant mg number 0 54 0 56 sio2 48 2 49 1 wt ce 12 18 ppm and ce yb 5 8 the underlying 1100 m of dominantly porphyritic basalt belong to the morongovsky and nadezhdinsky suites there is a continuous increase in sio2 48 1 55 2 wt ce 12 41 ppm and ce yb 5 18 from the top of the mokulaevsky to the base of the nadezhdinsky with little change in the mg number 0 53 0 59 mokulaevsky magmas have trace element signatures similar to slightly contaminated transitional type mid ocean ridge basalts the change in major and trace element geochemistry in the upper three suites is consistent with a decline in the degree of anatexis and assimilation of tonalitic upper crust by mokulaevsky magma the nadezhdinsky and underlaying lavas thicken within and thus appear to be related to an elongate basin centred on the noril sk talnakh mining camp the mokulaevsky and morongovsky lavas thicken to the east and appear to be related to a basin centred more than 100 km to the east of the noril sk region these magmas may have risen up out of a different conduit system

surface sediment effects on teleseismic p wave amplitude 1 teleseismic p waves are dominated by relatively low frequency 1 hz signals due to the earth s attenuation because of this receiver site effects are usually assumed to be independent of frequency we investigate the site amplitude effects due to a surface sediment layer and show that teleseismic frequency dependent site effects can be important one dimensional modeling shows that the effects of amplification due to differences in impedance combined with amplitude losses to reverberations in the sediment layer can result in significantly frequency dependent site effects the extent of the frequency dependence depends upon the two way travel time of p waves in the sediments and the dominant period of the p waves using model crust2 0 we compute a 2 2 map of the reference period of p waves above which the dependency can be neglected we argue that the common practice of applying station corrections to magnitude determination will underestimate the magnitude of large earthquakes to show that these effects are observable in practice we analyze the amplitude ratios of seven teleseismic events at the station pair kurk and makz and six events at the station pair kmi and chto the amplitude ratios are relatively insensitive to other contributing effects and are in good agreement with the predicted frequency dependent effects of the surface sediment layer

velocity deformation model for unsteady open channel flows over smooth and rough beds abstracta one dimensional depth averaged velocity deformation model is developed to study the characteristics of the unsteady flows in open channels the vertical profile of the streamwise velocity is expressed in a power series and the coefficients of the velocity are evaluated by using the unsteady equation of motion a concise form of the friction velocity for unsteady nonuniform flow is then proposed by utilizing the coefficients of the power series the applicability of the model is validated with experimental data producing reasonably good agreement between the model results and the observed data finally the deformation of velocity at the surface is assured by comparing velocity distribution of numerical model with the computational results from a previous model

numerical morphological modeling of open check dams open check dams are built in mountain streams to control sediment transport during a flood sediment passes through them at the lowest discharges whereas deposition occurs during the highest discharges open check dams are currently designed based mainly on construction experience modeling of hydraulics and bed morphology in check dams involves mixed flows supercritical and subcritical as well as discontinuities such as hydraulic jumps in this paper an unsteady coupled numerical mobile bed model that can tackle rapid varying flows and discontinuities is applied the numerical technique is based on the classical staggered grids and implicit integration schemes together with a proper mass and momentum balance the 1d numerical model is successfully verified with experimental data of slit check dams the applicability of the model in the design of open check dams is also illustrated

the effect of large scale shear velocity heterogeneity on ss precursor amplitudes 1 precursors to the ss wave have been analyzed extensively to characterize seismic discontinuities in the upper mantle we examine the influence of shear velocity heterogeneity on the amplitude of underside shear wave reflections off the 410 i e s410s and 660 i e s660s discontinuities using waveform data from global seismic networks and spectral element method synthetics for four tomographic models of the crust and mantle on average the s660s ss amplitude ratio is smaller than values predicted for the preliminary reference earth model prem and tomographic models of shear velocity perturbations from prem the variation of s410s ss and s660s ss ratios determined for the 3 d models is significant its amplitude depends on the amplitude of shear velocty heterogeneity in the mantle and on the incorporated model for the crust the s410s ss and s660s ss amplitude variations are stronger in the data and do not correlate spatially with the simulated ratios it is therefore not certain that the spatial variation of s410s ss and s660s ss as expressed by cap averaging can be related to compositional heterogeneity in the mantle given the profound influence of the heterogeneous crust and mantle

estimating local bed shear stress from velocity observations replicate velocity observations using conventional equipment under typical field conditions are used to evaluate the precision of different methods for estimating local boundary shear stress from velocity measurements the bed shear velocity u can be estimated within 3 using the depth averaged velocity in the vertically averaged logarithmic velocity profile to be accurate this method is limited to relatively simple flow geometries which may be expected to have the appropriate velocity structure estimates of u made using a single near bed velocity observation are less precise by a factor of 3 because of the larger uncertainty associated with a single observation accuracy of this method requires appropriate flow conditions only near the bed so it may be applied in a wider range of flow conditions including spatially variable flow estimates of u from the slope of the near bed velocity profile are the least precise and require the most restrictive flow conditions for accuracy but offer the advantage that they may be made without independent knowledge of the bed roughness different methods for estimating roe should be useful in judging the precision of estimates made under similar conditions these estimates of precision together with considerations of convenience and model accuracy provide the basis for select ing the most appropriate or advantageous method for different conditions and purposes

high resolution image of uppermost mantle beneath ne iran continental collision zone we invert 3775 relative p wave arrival times using the ach damped least square method of aki et al 1977 to study upper mantle structure beneath the ne iran continental collision zone the data for this study were recorded by 17 three component broad band stations operated from august 2006 to february 2008 along a profile from the center of iranian plateau near yazd to the northeastern part of iran on the turan platform just north of the kopeh dagh mountains the results confirm the previously known low velocity upper mantle beneath central iran our tomographic model reveals a deep high velocity anomaly the surficial expressions of this anomaly are between the ashkabad and doruneh faults where the resolution and ray coverage are good a transition zone in uppermost mantle is recognized under the binalud foreland that we interpreted as suture zone between iran and turan platform our results indicate that atrak valley which is the boundary between the binalud and kopeh dagh mountains can be considered as the northeastern suture of the iranian plateau where eurasia and turan platform under thrust beneath the binalud range and central iran

phase relations and liquid lines of descent in hydrous ferrobasalt implications for the skaergaard intrusion and columbia river flood basalts crystallization experiments using a hydrous ferrobasalt as starting material conducted at 200mpa 940 12008c at a wide range of water activities 0 1 1 and redox conditions qfm 3 to qfm 4 where qfm is the quartz fayalite magnetite oxygen buffer show that h2o influences significantly the differentiation history of ferrobasaltic magmas a combination of our data with published experiments on dry ferrobasalt at 1atm provides an extensive experimental database for modeling and quantifying crystallization and differentiation processes within a typical fe rich tholeiitic system under both dry and hydrous conditions the addition of h2o decreases liquidus temperatures and changes significantly the proportions temperature range and sequence of crystallizing mineral phases the dry liquidus is at about 11708c whereas the liquidus for h2o saturated melts is at 10608c the main phases crystallizing from h2o bearing ferrobasalt at the investigated conditions are olivine ol clinopyroxene cpx plagioclase pl magnetite mt hematite hm ilmenite ilm and amphibole am the phase assemblage is similar to that of the dry system except for the presence of hm at extremely oxidizing conditions and am at low temperatures 59508c and h2o saturated conditions the important observation made in this study is that the stability of fe ti oxides and in particular mt as well as the simultaneous coprecipitation of mtand ilm are almost independent of the activity of h2o ah2o in the system whereas the liquidus temperatures of the silicate minerals are dramatically depressed by increasing ah2o the stabilities of oxides are controlled mainly by the redox conditions prevailing in the system the most pronounced effect of ah2o on the liquidus temperatures of silicates is observed for pl which shows a considerable delay in crystallization with progressive magma differentiation early crystallization of fe ti oxides in h2o bearing ferrobasaltic compositions precludes any significant fe enrichment during differentiation as fe enrichment is a characteristic feature of the skaergaard intrusion it implies that the skaergaard parental magma did not contain considerable amounts of water on the other hand our experiments indicate that the differentiation of some ferrobasaltic series from the columbia river flood basalt province might have occurred in magmatic systems containing significant amounts of volatiles 0 5 3 wt h2o

estimating bed shear stress from remotely measured surface turbulent dissipation fields in open channel flows synoptic information on bed shear stress is necessary in predicting the transport of sediments and environmental contaminants in rivers and open channels existing methods of estimating bed shear stress typically involve measuring vertical profiles of streamwise velocity or reynolds stress and taking advantage of the logarithmic or the constant stress region respectively to determine friction velocity and subsequently bed shear stress while effective these methods yield local measurements of bed shear stress only direct measurements of bed shear stress can also be obtained through measurements with a drag plate however this method yields average shear stress information over the area of the plate and is impractical for large scale implementation in the field here we present a method capable of providing continuous synoptic measurements of bed shear stress over a large field of view a series of large scale particle image velocimetry lspiv and acoustic doppler velocimetry adv measurements were made in a variety of flows generated in a wide open channel facility turbulent dissipation is calculated on the free surface from the 2 d lspiv results and is correlated with near surface adv measurements of turbulent dissipation in the water column the adv results are consistent with the nezu 1977 established relationship for the vertical variation of turbulent dissipation in the water column knowledge of the correlation between free surface and near surface dissipation values coupled with nezu s 1977 relationship allow a robust and accurate estimate of friction velocity to be made and subsequently shear stress at the bed can be estimated this article is protected by copyright all rights reserved

velocity profiles in steep open channel flows velocity measurements with a fiber optic laser doppler anemometer were conducted in steep open channel flows over smooth and imcompletely rough beds the channel slopes were changed from 1 500 and 1 25 by steps and as a result the froude number changed from 0 5 to 3 the law of the wall and the distributions of turbulence intensity were examined in more detail the von karman constant n in the log law was verified to be universally equal to 0 41 on the other hand the integral constant ia n in the log law coincided with the usual value of 5 29 in subcritical flows whereas it decreased with an increase of the bed slope in supercritical flows this decrease of ia n was explained by a decrease of the damping factor ib n in the van driest s mixing length formula the decrease of ib n was well correlated with an increase of the friction velocity and the roughness the streamwise turbulence intensity became smaller in the near wall region than the semiempirical universal formula as the friction velocity became larger

drag reduction in turbulent muddy seawater flows and some sedimentary consequences turbulent saline flows which contain low concentrations of suspended clay 10 g 1 1 have previously been reported to possess dramatically different boundary layer characteristics from clearwater flows and to exhibit the phenomenon of drag reduction drag reduction causes significantly lower friction factors and higher erosion thresholds in muddy saline flows than predicted by experimental data gained from fresh water flows using the law of the wall to estimate bed shear stress confirmation is given by experimental results on drag reduction using non intrusive laser doppler measurements in seawater flows with 2 2 g 1 1 maximum concentration of suspended clay increasing the concentration of clay caused progressively lower velocities near the wall due to a gradual thickening of the buffer region of the turbulent boundary layer several aspects of sediment transport deposition and bedform development in natural marine environments are thus considered to be significantly affected by the drag reduction process

geology of the western flanks of the oktyabr skoe deposit noril sk district russia evidence of a closed magmatic system the oktyabr skoe deposit in the northern siberian platform is one of the world s largest deposits in terms of platinum group elements and nickel reserves the genesis of this deposit has been inferred from the inner geological structure of its central portion and remains a matter of long lasting and heated discussions the current dominant hypothesis is that the ores were produced in an open magmatic system this study is devoted to only one aspect of the complicated problem of ore formation i e the geological structure of the kharaelakh intrusion to which the huge orebodies are related recently new data have been acquired on the structure and composition of the western flanks of the kharaelakh intrusion which pinches out in this direction and does not coincide with basalts as has been suggested in many publications a distinctive feature of this part of the deposit is that it is cut by numerous relatively thin intrusions of contrasting compositions from picritic gabbro dolerite to leucogabbro that are spatially separated in contrast with the central portion of the deposit where these rocks occur as discrete layers of a single intrusion these bodies taper off westward and are blind apophyses of the intrusion to which various ore types are related the inner structure of this part of the vertical section of the intrusion is analyzed based on detailed data on the core material recovered by a number of boreholes and on the chemical and mineralogical characteristics of the ores which differ from those in the main orebodies in that they possess lower cu and pge concentrations up to 3 5 wt and 9 ppm respectively and hence result in the dominance of pyrrhotite and limited amounts and smaller grain sizes of platinum group minerals peripheral sills of the kharaelakh intrusion were formed by portions of initial magma with different melt cumulus minerals proportions forming separate bodies of picritic and olivine bearing gabbro dolerite the last rock varieties comprise disseminated ore in contrast with the central parts of the intrusion where these ores are located in the picritic and taxitic horizons no peripheral sills or dikes connected with lava flows have been found inside the studied area these facts evidence ore formation in a closed magmatic system

closure to response of velocity and turbulence to sudden change of bed roughness in open channel flow by xingwei chen and yee meng chiew

velocity distributions in spatially varied flow with increasing discharge the experimental study presented in this paper explores the distribution of the mean velocities for a channel receiving spatially varied sv inflow from directly above the centerline of the channel via sets of nozzles the velocity components u v and w have been measured using a laser doppler velocimeter initially the validity of the law of the wall in the channel receiving sv inflow was investigated it was found that the measured velocity profile within the inertial sublayer region near the channel bed falls below the line representing the log law further if the sv inflow enters at the center of the channel the degree that the data depart from the log law increases from the sidewall toward the center of the channel the structures of the velocity distributions are also presented in detail the results include both near field that is the area close to where the flow enters the channel and far field measurements it was found that the influence of the sv inflow on velocity profiles is largely c

insights into the kinematics of a volcanic caldera drop probabilistic finite source inversion of the 1996 bardarbunga iceland earthquake article i nfo the accurate modelling and prediction of volcanic eruptions depends critically on information concerning the interaction between the caldera and the underlying magma chamber knowledge concerning the kinematics of a caldera in the course of an eruption is therefore essential here we provide detailed seismological constraints on the kinematics of a volcanic caldera drop and the geometry of a caldera ring fault for this we performed a finite source inversion of the september 29 1996 bardarbunga iceland earthquake that was caused by caldera subsidence our methodology is based on spectral element simulations of seismic wave propagation through a realistic model of the icelandic crust and upper mantle a particularly robust feature is the initiation of the rupture in the north western part of the ring fault that is about 10 km in diameter from there it spread to the other fault segments within about 3 s without invoking super shear propagation sensu stricto we can explain this unusually fast rupture propagation by the triggering of fault segments through p waves that propagated across the caldera our results favour outward dipping fault segments in the western half of the ring fault while the eastern half is preferentially inward dipping this variability may reflect structural heterogeneities or an irregular magma chamber geometry the individual segments of the caldera ring fault radiated approximately equal amounts of energy this indicates that the caldera dropped coherently as one single block the work presented here is intended to aid in the design of realistic models of magma chamber and caldera dynamics