real time infrasonic monitoring of the eruption at a remote island volcano using seismoacoustic cross correlation s u m m a r y on 2013 november 20 a submarine eruption started close to nishinoshima island which lies 1000 km south of tokyo real time monitoring of the eruption is crucial for understanding the formation processes of the new volcano island and related disaster prevention in situ monitoring however is difficult in practice because the closest inhabited island chichijima is 130 km away from nishinoshima this study presents an infrasonic monitoring method that uses cross correlating records at a pair of online stations on chichijima one is the horizontal ground velocity recorded at a permanent seismic station operated by the japan meteorological agency jma the seismic records were corrected for atmospheric pressure using an empirical ground response to infrasound the other is the air pressure recorded at the jma meteorological observatory for each station we divided the whole records into 3600 s segments to suppress outliers each segment was normalized by the envelope function we then calculated cross correlation functions between the pair of stations using the fast fourier transform they present clear successive arrivals of infrasound coming from nishinoshima we also conducted an offline tripartite array observation using three low frequency microphones with a station spacing of 50 m installed in 2013 may the array analysis supports the results obtained from the online stations the typical root mean squared amplitude is on the order of 0 01 pa and the typical duration is several days the amplitudes were primarily controlled by the effective sound velocity structure from nishinoshima to chichijima the infrasonic observations together with the meteorological observation at chichijima suggest that infrasonic activity was not present in the first two weeks in 2015 january with the help of a more quantitative estimation of the meteorological effect we could infer eruptive activity in real time now many online seismic stations are available worldwide this study shows that installation of another infrasonic sensor close to the existing seismic station 1 km is useful for monitoring a remote island volcano in real time

generation and evolution of siliceous high magnesium basaltic magmas in the formation of the permian huangshandong intrusion xinjiang nw china abstract numerous permian orthopyroxene rich mafic ultramafic intrusions in the southern margin of the central asian orogenic belt caob have been emplaced in a post orogenic environment the huangshandong mafic ultramafic intrusion is the largest in the eastern tianshan orogenic belt of the caob and consists of a layered unit intruded by a massive unit the layered unit consists of lherzolite troctolite olivine gabbro hornblende gabbro gabbrodiorite and diorite whereas the massive unit is made of gabbronorite and olivine gabbronorite olivine from the layered unit has fo values of 75 to 84 and contains low nio and mno rocks from this unit have initial 87sr 86sr ratios 0 7031 0 7043 and end values 3 4 7 1 while plagioclase has initial 87sr 86sr ratios ranging from 0 70010 to 0 71569 olivine from the massive unit has relatively low fo values of 59 to 70 and high nio and mno rocks from this unit have relatively low and uniform initial 87sr 86sr ratios 0 7030 and high end values 6 0 7 5 and contain plagioclase with relatively low initial 87sr 86sr ratios 0 70042 to 0 70520 olivines from both units have low cao and cr2o3 both units formed from siliceous high magnesium basaltic magmas were derived from a hydrous depleted mantle source magma forming the layered unit experienced earlier removal of sulfides before emplacement with the earlier sulfide saturation caused by the addition of crustal material the magma that formed the massive unit has undergone fractional crystallization of olivine cr spinel siliceous high magnesium basaltic magmatism produced by melting of a hydrous depleted mantle source may be an important feature of orogenic belts

infrasonic tremor in the diffraction zone 1 volcanic tremor signals recorded by an infrasound array 12 5 km from the active vent of k lauea volcano show clear diurnal amplitude variations and originate from a well defined direction pointing to the active pu u crater complex spectral amplitudes between 0 02 0 3 hz a proxy for wind speed increase when the wind speeds increase during the daytime spectral amplitudes between 0 5 3 hz where infrasonic tremor is concentrated increase when the wind speeds decrease at night power spectrum analysis shows that when ambient noise levels drop infrasonic tremor amplitudes rise array processing confirms this relationship and reveals tremor detections and amplitudes decrease during the day these changes in infrasonic tremor spectral amplitude and coherence are most likely due to diurnal variations in atmospheric boundary layers affecting infrasonic propagation within the diffraction zone recognition of these regional atmospheric patterns is necessary to permit robust infrasonic remote sensing of volcanic processes

estimates of plume height from infrasound for regional volcano monitoring abstract present efforts in volcano monitoring particularly in southeast asia rely on the combination of local data generally gathered at less than 100 km from the volcano and satellite remote sensing while this combination has its strengths there are still weaknesses that the use of ground based remote sensing data such as distant infrasound measurements could help alleviate infrasound offers tools for detecting and characterizing volcanic plumes independent of cloud cover and time of day larger volcanic eruptions generate infrasound that is related to the plume and offers a unique view into eruption dynamics within the context of monitoring past research has demonstrated that infrasound can be used to estimate source parameters such as the rate at which material is ejected from volcanic vents during eruptions these are key input parameters into empirical and numerical models to estimate the height of volcanic plumes atmospheric ash transport and dispersion here we demonstrate the use of remote infrasound in estimating the height of volcanic plumes including a case study on the may 30 2014 plume from the volcano sangeang api in indonesia we were able to determine the plume height using infrasound gathered from 2000 to over 5000 km distance from the volcano during the january 2020 eruption of taal volcano in the philippines this method was applied to remote infrasound recorded 1650 km to the east we show that our workflow can be implemented in near real time offering an effective tool for rapid plume height measurement including associated uncertainties when volcanic clouds are not visible from the ground or space

acoustic source inversion to estimate volume flux from volcanic explosions we present an acoustic waveform inversion technique for infrasound data to estimate volume fluxes from volcanic eruptions previous inversion techniques have been limited by the use of a 1 d green s function in a free space or half space which depends only on the source receiver distance and neglects volcanic topography our method exploits full 3 d green s functions computed by a numerical method that takes into account realistic topographic scattering we apply this method to vulcanian eruptions at sakurajima volcano japan our inversion results produce excellent waveform fits to field observations and demonstrate that full 3 d green s functions are necessary for accurate volume flux inversion conventional inversions without consideration of topographic propagation effects may lead to large errors in the source parameter estimate the presented inversion technique will substantially improve the accuracy of eruption source parameter estimation cf mass eruption rate during volcanic eruptions and provide critical constraints for volcanic eruption dynamics and ash dispersal forecasting for aviation safety application of this approach to chemical and nuclear explosions will also provide valuable source information e g the amount of energy released previously unavailable

evaluation of infrasound signals from the shuttle atlantis using a large seismic network inclement weather in florida forced the space shuttle atlantis to land at edwards air force base in southern california on june 22 2007 passing near three infrasound stations and several hundred seismic stations in northern mexico southern california and nevada the high signal to noise ratio broad receiver coverage and atlantis positional information allow for the testing of infrasound propagation modeling capabilities through the atmosphere to regional distances shadow zones and arrival times are predicted by tracing rays that are launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model the predictions and observations compare favorably over much of the study area for both atmospheric specifications to the east of the shuttle trajectory there were no detections beyond the primary acoustic carpet infrasound energy was detected hundreds of kilometers to the west and northwest nw of the shuttle trajectory consistent with the predictions of ducting due to the westward summer time stratospheric jet both atmospheric models predict alternating regions of high and low ensonifications to the nw however infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification possibly due to uncertainties in stratospheric wind speeds

observations of surf infrasound in hawai i 1 comparison of ocean buoy measurements with infrasonic array data collected during the epic winter of 2002 2003 shows a clear relationship between breaking ocean wave height and infrasonic signal levels in addition infrasonic arrays allow the identification of distinct breaking zones along the shoreline our observations suggest that infrasonic measurements can be used in conjunction with buoys to estimate wave heights identify regions of high wave action and validate surface wave propagation models

scaling nature of crustal susceptibilities scale invariant or self similar properties have been demonstrated for a wide range of geophysical processes and rock properties evidence from well logs and inferences from aeromagnetic field power spectra suggest that crustal susceptibility also shows this behaviour with a power spectrum proportional to the 4 power of the spatial frequency we examine two large susceptibility measurement data sets and find that they both support the scaling hypothesis

ash plume dynamics and eruption source parameters by infrasound and thermal imagery the 2010 eyjafjallajokull eruption during operational ash cloud forecasting prediction of ash concentration and total erupted mass directly depends on the determination of mass eruption rate mer which is typically inferred from plume height uncertainties for plume heights are large especially for bent over plumes in which the ascent dynamics are strongly affected by the surrounding wind field here we show how uncertainties can be reduced if mer is derived directly from geophysical observations of source dynamics the combination of infrasound measurements and thermal camera imagery allows for the infrasonic type of source to be constrained a dipole in this case and for the plume exit velocity to be calculated 54 142 m s based on the acoustic signal recorded during the 2010 eyjafjallajokull eruption from 4 to 21 may exit velocities are converted into mer using additional information on vent diameter 50 10 m and mixture density 5 4 1 1 kg m3 resulting in an average 9 105 kg s mer during the considered period of the eruption we validate our acoustic derived mer by using independent measurements of plume heights icelandic meteorological office radar observations acoustically derived mer are converted into plume heights using field based relationships and a 1d radially averaged buoyant plume theory model using a reconstructed total grain size distribution we conclude that the use of infrasonic monitoring may lead to important understanding of the plume dynamics and allows for real time determination of eruption source parameters this could improve substantially the forecasting of volcano related hazards with important implications for civil aviation safety

nd and sr isotopic systematics of central australian granulites chronology of crustal development and constraints on the evolution of lower continental crust nd and sr isotopic data are reported for a granulite terrain in the proterozoic arunta block of central australia sm nd data from a wide range of rock types define a crust formation age of 2 070 125 ma and provide further evidence for voluminous crustal growth in the proterozoic an nd value of 1 5 0 8 indicates a depleted mantle source for this crustal segment and there is no evidence for a large component of significantly older sialic crust field relationships geochemistry and rb sr data for mafic and felsic granulites indicate that intracrustal differentiation and polyphase deformation were followed by granulite facies metamorphism rb depletion at 1 800 ma rb sr data for strongly retrogressed granulites define an age of 1 700 ma which is interpreted as the time of retrograde biotite growth partial melting at the presently exposed crustal level and anatexis at deeper crustal levels were broadly coeval with the retrograde metamorphism sm nd and rb sr isotopic systematics of minerals indicate that the terrain cooled slowly did not experience significant uplift until 1 000 ma and remained at temperatures above 320 c until the late palaeozoic the mineral data are consistent with geological relationships and petrological evidence for a prolonged period of isobaric cooling followed by uplift late in the metamorphic evolution of the terrain the granulite protoliths appear to have formed in a rift which closed within 280 ma of initial separation deformation and granulite facies metamorphism at 1 800 ma are interpreted to be a consequence of collision between the continental blocks which defined the rift regional retrogression and granitoid magmatism at 1 700 ma are attributed to underthrusting of the granulites by lower grade rocks in the final stages of collision subsequent events in the cooling and uplift history appear to have been controlled by the presence of long lived major faults in the crust and a prolonged history of episodic compression in the continental lithosphere the results of this study suggest that granulite terrains in general cannot be equated with lower continental crust but instead represent assemblages of mainly supracrustal rocks which in some instances have been involved in major collision events

capturing the acoustic radiation pattern of strombolian eruptions using infrasound sensors aboard a tethered aerostat yasur volcano vanuatu we obtained an unprecedented view of the acoustic radiation from persistent strombolian volcanic explosions at yasur volcano vanuatu from the deployment of infrasound sensors attached to a tethered aerostat while traditional ground based infrasound arrays may sample only a small portion of the eruption pressure wavefield we were able to densely sample angular ranges of 200o in azimuth and 50o in take off angle by placing the aerostat at 38 tethered loiter positions around the active vent the airborne data joined contemporaneously collected ground based infrasound and video recordings over the period 29 july to 1 august 2016 we observe a persistent variation in the acoustic radiation pattern with average eastward directed root mean squared pressures more than 2 times larger than in other directions the observed radiation pattern may be related to both path effects from the crater walls and source directionality

finite difference synthesis of infrasound propagation through a windy viscous atmosphere application to a bolide explosion detected by seismic networks summary a finite difference time domain fdtd algorithm has been developed to model linear infrasound propagation through a windy viscous medium the algorithm has been used to model signals from a large bolide that burst above a dense seismic network in the us pacific northwest on 2008 february 19 we compare synthetics that have been computed using a g2s ecmwf atmospheric model to signals recorded at the seismic networks located along an azimuth of 210 from the source the results show that the timing and the range extent of the direct stratospherically ducted and thermospherically ducted acoustic branches are accurately predicted however estimates of absorption obtained from standard attenuation models sutherland bass predict much greater attenuation for thermospheric returns at frequencies greaterthan0 1hzthanisobserved weconcludethateitherthestandardabsorptionmodelfor the thermospheric is incorrect or that thermospheric returns undergo non linear propagation at very high altitude in the former case a better understanding of atmospheric absorption at high altitudes is required in the latter a fully non linear numerical method is needed to test our hypothesis that higher frequency arrivals from the thermosphere result from non linear propagation at thermospheric altitudes

energy histograms for the characterization of deep reflection seismic profiles summary we modified dohr s method and were able to establish trends of crustal reflectivity distribution four main types of crustal reflectivity depth histograms could be distinguished dohr s method was based on line drawings from which the total length of reflections was calculated for time distance frames along the profile in this paper we present a new method to derive such histograms automatically from the final stack tapes this allows an objective comparison of deep reflection seismograms from different crustal units and from different research groups it is shown that our energy histograms are consistent with earlier manually produced histograms and that the previous results can be reproduced first applications to dekorp and ktb data in germany are presented

world class ni cu pge deposits key factors in their genesis magmatic ni cu sulfide deposits form as the result of segregation and concentration of droplets of liquid sulfide from mafic or ultramafic magma and the partitioning of chalcophile elements into these from the silicate melt sulfide saturation of a magma is not enough in itself to produce an ore deposit the appropriate physical environment is required so that the sulfide liquid mixes with enough magma to become adequately enriched in chalcophile metals and then is concentrated in a restricted locality so that the resulting concentration is of ore grade the deposits of the noril sk region have developed within flat elongate bodies 15 2 0 2 km that intrude argillites evaporites and coal measures adjacent to a major trans crustal fault and immediately below the centre of a 3 5 km thick volcanic basin studies of the overlying basalts have shown that lavas forming a 500 m thick sequence within these have lost 75 of their cu and ni and more than 90 of their pge overlying basalts show a gradual recovery in their chalcophile element concentrations to reach normal values 500 m above the top of the highly depleted zone the ore bearing noril sk type intrusions correlate with those basalts above the depleted zone that contain normal levels of chalcophile elements the high proportion of sulfide 2 10 wt associated with the noril sk type intrusions the high pge content of the ores the extensive metamorphic aureole 100 400 m around the bodies and the heavy sulfur isotopic composition of the ores 8 12 34s are explicable if the ore bearing bodies are exit conduits from high level intrusions along which magma has flowed en route to extrude at surface the first magma to enter these intrusions reacted with much evaporitic sulfur at a low r value and thus gave rise to sulfides with low metal tenors successive flow of magma through the system progressively enriched the sulfides in the conduits losing progressively less of their chalcophile metals and thus accounting for the upward increase in metals in successive lava flows above the highly depleted flows the voisey s bay deposit lies partly within a 30 100 m thick sheet of troctolite interpreted as a feeder for the 1 334 ga voisey s bay intrusion and partly at the base of this intrusion where the feeder adjoins it studies of olivine compositions indicate that an early pulse of magma through the feeder and into the intrusion was ni depleted but that subsequent pulses were much less depleted trace element re os and s and o isotope data and mineralogical studies indicate that the magma pulses interacted with country gneiss probably principally in a deeper level intrusion extracting sio2 na2o k2o and possibly sulfur form the gneiss which accounts for the magma becoming sulfide saturated the jinchuan deposit of north central china occurs within a 6 km long dyke like body of peridotite the compositions of olivine within the dyke the igneous rocks themselves and the ore are all inconsistent with derivation of the body from ultramafic magma as originally supposed and indicate that the structure forms the keel of a much larger intrusion of magnesian basalt magma flow of magma into the intrusion has resulted in olivine and sulfide being retained where the keel was widening out into the intrusion the west australian komatiite related deposits occur in thermal erosional troughs which have developed due to the channelisation of magma flow and the resulting thermal erosion of underlying sediments and basalt by the hot komatiite magma the sediments are sulfide rich and may have contributed substantially to the sulfide of the ores the mineralisation in the duluth complex occurs in troctolitic intrusions along the western margin of the complex as a result of magma interacting with and extracting sulfur from the underlying graphite and sulfide bearing sediments no magma flow channels have been identified so far and the lack of magma flow subsequent to the development of sulfide immiscibility is regarded as the reason why these deposits are not of economic grade when most major ni cu sulfide deposits are compared they prove to have a number of features in common olivine rich magma proximity to a major crustal fault sulfide bearing country rocks chalcophile element depletion in related intrusive or extrusive rocks field and or geochemical evidence of interaction between the magma and the country rocks and the presence of or proximity to a magma conduit the features are thought to explain the three key requirements sulfide immiscibilty adequate mixing between sulfides and magma and localisation of the sulfides discussed and have important implications with respect to exploration

utilizing the solution of sound diffraction by a thin screen to evaluate infrasound waves attenuated around volcano topography abstract the observation of infrasound signals in the vicinity of volcanoes is a powerful tool to understand the source of explosive volcanic activity although the propagation of infrasound signals is affected by the local topography such effects are often ignored in the analysis leading to potential misinterpretation of the source parameters in this study we propose a simple low cost method of evaluating the attenuation of infrasound signals by topographical barriers in this method the first step approximates the elevation profile between the source and station into one thin screen like barrier then a mathematically exact solution of a sound diffraction problem is adopted to evaluate the attenuation of the infrasound amplitudes to assess the validity of this method the obtained estimates are compared with actual infrasound data observed at sakurajima volcano japan the results show that the estimates of relative amplitude to a reference station are more accurate than those considering only geometrical spreading suggesting that the proposed method provides a useful first order investigation of the attenuation of infrasound signals the spatial distribution of the attenuation in the entire area of the volcano was also estimated revealing a significant contrast between the eastern and western sides of the study area variations in signal attenuation also depend on the radial distance from the crater and were mainly attributed to variations of the relative screen height to the incident wavelength

ground coupled air waves and diffracted infrasound from the arequipa earthquake of june 23 2001 1 on june 23 2001 a strong earthquake measuring mw 8 4 occurred along the coast of south central peru coherent infrasonic waves were detected over a period of one hour by the is08 infrasound station in bolivia analysis of the ground coupled air waves shows that the rupture propagated from the northwestern to the southeastern part of the fault with a rupture velocity of 3 3 km s the azimuth variation of the infrasonic waves is attributed to a distribution of secondary sources along the highest mountain ranges which excite infrasonic waves that are diffracted to the ground the predominant source of infrasound is likely distributed along the andean cordillera using the azimuth and arrival time determination the horizontal scale size of the distant source regions of infrasonic waves is reconstructed over distances greater than 400 km

the adakite connection of the tuwu yandong copper porphyry belt eastern tianshan nw china trace element and sr nd pb isotope geochemistry the tuwu yandong porphyry copper belt lies in the eastern tianshan mountains eastern section of the central asian orogenic belt the copper mineralization is mainly hosted in plagiogranite porphyries intruded into early carboniferous volcanic rocks of the paleozoic dananhu island arc between the tarim and siberian plates the plagiogranite porphyries have contents of 65 73 wt sio2 14 17 wt al2o3 0 9 2 2 wt mgo 3 16 ppm y 0 4 1 40 ppm yb 347 920 ppm sr and positive eu anomalies the rocks also exhibit positive nd t values 5 0 to 9 4 and low initial 87sr 86sr values 0 70316 0 70378 such features are similar to those of adakites derived from partial melting of a subduction related oceanic slab the mineralization age is early carboniferous 350 320 ma which is close to that of the porphyries the close relationship between the cu mineralization and the porphyry is also indicated by their similar sr nd pb isotopic compositions we suggest that the copper porphyry magma system in the dananhu island arc was formed by direct melting of an obliquely subducting early carboniferous oceanic slab

a review of the cu ni sulphide deposits in the chinese tianshan and altay orogens xinjiang autonomous region nw china principal characteristics and ore forming processes abstract several cu ni sulphide deposits and occurrences have recently been discovered along parallel deep faults in the chinese tianshan and altay orogenic belts xinjiang province nw china the kalatongke and several other cu ni mineralized intrusions are located along the irtysh fault which separates the altay orogenic belt from the junggar basin the huangshan huangshandong xiangshan tudun erhongwa tula ergen and hongling deposits occur along the kanggurtag suture which separates the jueluotage orogenic belt from the turpan hami tuha basin the baishiquan tianyu and tianxiang deposits are located along the arqikekuduke fault which separates the jueluotage orogenic belt from the central tianshan precambrian terrane the poyi poshi and luodong deposits are located along the baidiwa fault which separates the central tianshan precambrian terrane from the beishan paleozoic rift re os dating of cu ni sulphide ores reveals that these cu ni ore belts formed in a narrow age range of 298 282 ma this age range is about the same as those of associated intrusions and dykes dated by the shrimp zircon u pb method tectonic and geochronological constraints suggest that the amalgamation of continental blocks mainly occurred during the late carboniferous in the central asian orogenic belt large scale hydrothermal and magmatic metallogenesis in the region occurred during post collisional stages of latest carboniferous to early permian age the cu ni sulphide deposits are part of this metallogenic event the cu ni orthomagmatic sulphide deposits in northern xinjiang are represented by 1 net textured type deposits by segregation of a cu ni metal sulphide melt and 2 magma conduit type some mafic ultramafic suites exhibit lithological zoning caused by strong differentiation stratiform orebodies are hosted by ultramafic rocks at the base of the magma chamber good examples are the kalatongke huangshandong and poshi deposits others such as the xiangshan baishiquan tianyu and tula ergen deposits are hosted by magma conduits consisting of peridotite troctolite and pyroxenite these ultramafic rocks either occur within faults or are surrounded by gabbroic and dioritic intrusions these two types of orthomagmatic cu ni sulphide deposits are also distributed along the same ore belts for instance the differentiated sill related huangshandong deposit co exists with the magma conduit type tula ergen deposit in the jueluotage orogenic belt orthomagmatic cu ni sulphide deposits in northern xinjiang formed during post collisional extension and are possibly related to a late carboniferous early permian mantle plume event the mafic ultramafic suites and associated cu ni deposits are commonly accompanied by dyke swarms and are characterized by elongated outcrops occurring along parallel e w trending regional faults these mafic ultramafic suites and accompanying dyke swarms are generally fractionated implying that they were feeders of presently eroded flood basalts

u pb ages and hf o isotopes of zircons from late paleozoic mafic ultramafic units in the southern central asian orogenic belt tectonic implications and evidence for an early permian mantle plume abstract u pb age and hf o isotope data of zircons from the mafic ultramafic complexes and their related rhyolites and granites in the eastern tianshan and beishan regions were obtained by sims and la icpms the hf o isotopic composition and hf model age of the zircons are closely related to their tectonic setting and formation age the zircons from the mafic ultramafic complexes in the bogeda haerlike and jueluotage belts have higher ehf t 8 17 and lower 18o 4 6 whereas most of the zircons in the gabbros granites and rhyolite from the middle tianshan massif and beishan rift display lower ehf t 0 8 and higher 18o 5 8 the positive ehf t and relatively lower 18o values suggest that these mafic ultramafic complexes were derived from depleted mantle which was subjected to subduction related modification processes the hf isotopic composition of zircons in the granites has revealed that the growth of juvenile crust was also very significant in the southern margin of the central asian orogenic belt during the paleozoic the hf model ages of the analyzed zircons together with the regional geology suggest that the beishan area had a northward subduction possibly from ca 900 ma to ca 400 ma whereas the eastern tianshan had a south directed subduction most likely from ca 600 ma to ca 310 ma additionally zircons with ca 280 ma u pb ages display wider and more scattered ehf t and 18o variations than the relatively older and younger ones which further support the early permian mantle plume model

the role of komatiitic and picritic magmatism and s saturation in the formation of ore deposits abstract the introduction of high temperature high magnesium komatiitic and picritic magmas into the earth s upper crust has given rise either directly or indirectly to many of the world s major ore deposits there is a direct association between komatiitic magmatism and kambalda style ni cu pge deposits the link between magma type and mineralization is not as clear cut in the case of the noril sk cu ni pge deposits but nevertheless there is an association between picritic magmatism and ore deposit development komatiitic and or picritic magmatism may also have contributed to the formation of many types of hydrothermal ore deposits recent nd isotope data generated by kent et al 1994 provide strong evidence for the hypothesis proposed by keays in 1983 that the au in archaean au deposits was derived either directly or indirectly from komatiites through the action of metamorphic fluids the importance of komatiitic and picritic magmas in ore forming processes arises from the fact that they are among the few mafic ultramafic magma types that are s undersaturated at the time of magma formation s saturation of magmas leads to marked depletion in the chalcophile metals for example czamanske and moore 1977 estimated that a third of the original cu and ni contents of morb were lost from the magmas due to extraction into magmatic sulphides the depletion in au and the pge is much greater due to their much larger partition coefficients keays and scott 1976 komatiitic and picritic magmas are s undersaturated because they are high temperature magmas produced by large degrees of partial melting of upper mantle sourc regions that were already depleted in s through earlier partial melting events most mafic magmas produced by less than 25 partial melting are s saturated and hence depleted in the ore forming chalcophile elements in contrast komatiitic and picritic magmas have their full complement of chalcophile metals when they do become s saturated they form sulphides that are strongly enriched in ni cu au pge and other strongly chalcophile metals these may accumulate to form ore deposits directly e g magmatic ni cu pge sulphides or be dispersed in komatiitic picritic rocks or their fractionation products making these source rocks for hydrothermal au or vms deposits

using infrasound waves to monitor tropospheric weather and crater morphology changes at volcan tungurahua ecuador abstract we use infrasound waves generated during eruptions of volcan tungurahua ecuador to study both changing atmospheric conditions and volcanic source characteristics analyzed infrasound data were recorded for a 32 month period by a five station network located within 6 5 km from the vent we use cross network correlation to quantify the recurrent eruptive behavior of tungurahua and results are corroborated by reports from the ecuadorian monitoring agency cross network lag times vary over short time periods minutes to days when vent location is stable and attribute these variations to changes in atmospheric structure assuming a fixed source location we invert for average air temperatures and winds in tungurahua s vicinity

observations of infrasound from surf in southern california 1 we observe 10 000 s of infrasound signals annually in the frequency range from 1 5 hz at the i57us infrasound array in southern california 75 of these signals arrive at i57us at azimuths between 260 and 320 degrees there is a good correlation between the amplitudes of signals from 260 320 and wave height measurements offshore southern california providing firm evidence that the signals from these azimuths are caused by surf action by modeling the propagation of infrasound for specific time periods using 3d ray tracing and up to date atmospheric models we show that amplitudes of signals recorded at i57us are also dependent upon atmospheric winds the modeled rays that return in the stratosphere fit observations more closely than modeled rays that return in the troposphere suggesting the signals are from stratospheric returns our findings are the first observations of surf infrasound at a long range from the source region this suggests that surf signals might serve as a probe of the atmosphere much like microbarom signals are used to probe the atmosphere at greater range

infrasound reveals transition to oscillatory discharge regime during lava fountaining implication for early warning 1 we present the analysis of 4 million infrasonic signals which include 39 episodes of lava fountains recorded at 5 5 km from the active vents we show that each eruptive episode is characterized by a distinctive trend in the amplitude waveform and frequency content of the acoustic signals reflecting different explosive levels lava fountain starts with an 93 min long violent phase of acoustic transients at 1 25 hz repeating every 2 5 s infrasound suddenly evolves into a persistent low frequency quasi monochromatic pressure oscillation at 0 4 hz we interpret this shift as induced by the transition from the slug discrete strombolian to churn flow sustained lava fountain regime that is reflecting an increase in the gas discharge rate we calculate that infrasonic transition can occur at a gas superficial velocity of 76 m s and it can be used to define infrasonic based thresholds for an efficient early warning system

empirical mode skeletonization of deep crustal seismic data theory and applications seismic skeletonization is a pattern recognition technique used to decompose reflection seismic data into events or reflectors and their seismic attributes and to store the results in an event file for an analysis toward seismic interpretation the extraction of instantaneous frequency from the event file for any statistical analysis of the seismic attribute analysis is currently not possible thus precluding the complete parameterization of the reflected seismic wave field in terms of its decomposition products empirical mode decomposition of reflection seismic data has uniquely addressed the question of computing the instantaneous frequency from its decomposition products using the hubert transform although the decomposition products of the seismic skeletonization and the empirical mode decomposition are conceptually different they share a common link to the primitive features of the seismic waveforms in this paper we introduce a new decomposition technique empirical mode skeletonization that combines the features of both seismic skeletonization and empirical mode decomposition by this process it is now possible to subject the reflection seismic data to an analysis that could include a parameterization of the reflected wave field we apply the new technique to a segment of seismic line 1 of the lithoprobe slave northern cordillera lithosphere evolution snorcle transect to extract event oriented instantaneous frequency attributes and also to analyze the decomposition products for any scaling behavior of the reflected wave field

in situ u pb hf and re os isotopic analyses of the xiangshan ni cu co deposit in eastern tianshan xinjiang central asia orogenic belt constraints on the timing and genesis of the mineralization abstract the timing and genesis of the major ni cu co sulfide deposit in the xiangshan intrusion have been studied based on newly obtained in situ u pb hf and re os isotopic analyses the sims u pb zircon ages of the gabbro hosting the ni cu co sulfide deposit indicate that the xiangshan intrusion was emplaced at 279 6 1 1 ma 95 confidence level mswd 1 30 n 15 on the basis of combined geological and geochronological evidence we suggest that the xiangshan and other adjacent ni cu deposits were formed in the same period sulphides have low common os concentrations and high re os ratios similar to sulphide ores from the duluth sally malay and voisey bay complexes the re os isotopic data from the disseminated and massive ores from the xiangshan intrusion do not form a single isochron as they have different initial os ratios the hf and os isotopic data suggest that the xiangshan intrusion and associated ni cu co mineralization were derived from crustally contaminated mantle melts the geochemical data show a tholeiitic affinity and a strong suprasubduction zone signature with negative nb sr and ti anomalies similar to n morb and e morb we suggest that the mafic ultramafic rocks and associated ni cu mineralization of the eastern tianshan orogen formed in an alaska type subduction zone arc setting some diagnostic features of ridge trench interaction are present in the chinese east tianshan orogen e g granites adakites high mg andesites near trench magmatism alaskan type mafic ultramafic complexes high temperature metamorphic belts that prograde rapidly from low grade belts and orogenic gold deposits the above distinctive rock groups are probably related to the same thermal event ridge subduction as in the cenozoic orogen of alaska we suggest that ridge subduction is the most plausible mechanism to provide the necessary heat ridge subduction provides an important promising model for understanding many aspects of the evolution of the chinese eastern tianshan orogen and by inference throughout much of central asia

pattern analysis of seismic records the three steps in automated analysis of seismic records are trace matching event detection and seismic zoning our algorithm matches traces by comparing sequences of peaks on neighboring traces and edits pairs of peaks identified as similar for consistency in trend across and down the record by combining connected pairs we obtain laterally coherent events of varying quality which divide a record into zones that may have lithologic significance these zones can be obtained automatically by applying cluster analysis to seismic attributes and other discriminating properties of these events on common shot gathers from a four fold survey in saskatchewan canada the coherent events which we detected this way are consistent with those recognized visually and are associated with clear formation boundaries strong reflections correspond to events detected with high confidence and the seismic zones show good correlation among shot records high detection confidence and good correlation indicate that the app

characterization of moderate ash and gas explosions at santiaguito volcano guatemala from infrasound waveform inversion and thermal infrared measurements the rapid discharge of gas and rock fragments during volcanic eruptions generates acoustic infrasound here we present results from the inversion of infrasound signals associated with small and moderate gas and ash explosions at santiaguito volcano guatemala to retrieve the time history of mass eruption rate at the vent acoustic waveform inversion is complemented by analyses of thermal infrared imagery to constrain the volume and rise dynamics of the eruption plume finally we combine results from the two methods in order to assess the bulk density of the erupted mixture constrain the timing of the transition from a momentum driven jet to a buoyant plume and to evaluate the relative volume fractions of ash and gas during the initial thrust phase our results demonstrate that eruptive plumes associated with small to moderate size explosions at santiaguito only carry minor fractions of ash suggesting that these events may not involve extensive magma fragmentation in the conduit

investigating spectral distortion of local volcano infrasound by nonlinear propagation at sakurajima volcano japan author s maher s p matoza r s de groot hedlin c d gee k l fee d yokoo a

sulfide saturation and magma emplacement in the formation of the permian huangshandong ni cu sulfide deposit xinjiang northwestern china the eastern tianshan orogenic belt northwestern china hosts 120 mafic ultramafic intrusions and at least six of them host significant ni cu sulfide mineralization of which the permian huangshandong intrusion is the largest the mafic ultramafic rocks of the huangshandong intrusion comprise lherzolite gabbronorite gabbro and diorite individual orebodies are composed of pyrrhotite pentlandite and chalcopyrite as disseminated to net textured or massive to semimassive sulfide mineralization oxide bearing sulfide mineralization contains 1 to 5 magmatic magnetite that has ilmenite and spinel exsolution lamellae silicate rocks and sulfide mineralization have variable whole rock platinum group elements pge 0 38 362 ppb cu 42 97 000 ppm and ni 26 33 000 ppm concentrations the mineralization is broken out into two types termed oxide rich and oxide poor the oxide rich sulfide mineralization has high pge concentrations with low 187re 188os ratios 38 9 151 whereas oxide poor sulfide mineralization has low pge concentrations with high 187re 188os 159 781 both oxide rich and poor sulfide mineralization have highly variable os values 49 189 and 30 278 respectively oxide rich sulfide mineralization contains magnetite with variable amounts of mgo tio2 al2o3 feototal cr v zn and sn indicating that they crystallized from different stages during magma differentiation we propose that the host intrusion and associated sulfide mineralization were derived from high mg basaltic magmas from a mantle source that was previously modified by subducted oceanic slab oxide poor sulfide mineralization of the huangshandong intrusion formed from a magma that underwent 0 03 sulfide removal before emplacement and was thus pge depleted oxide rich sulfide mineralization formed from magma that had much lower amounts of sulfide 0 003 removed in the early stage before entering the huangshandong magma chamber an early sulfide saturation event was likely associated with fractionation of silicate minerals in a deep staging magma chamber the second sulfide saturation event that formed the sulfide mineralization was probably triggered by selective crustal contamination and fractionation in the high level chamber where mixing of magmas and accumulation of immiscible sulfide occurred

the source of infrasound associated with long period events at mount st helens 1 during the early stages of the 2004 2008 mount st helens eruption the source process that produced a sustained sequence of repetitive long period lp seismic events also produced impulsive broadband infrasonic signals in the atmosphere to assess whether the signals could be generated simply by seismic acoustic coupling from the shallow lp events we perform finite difference simulation of the seismo acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere the effects of topography velocity structure wind and source configuration are considered the simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of p sv and rayleigh wave energy converted locally along the propagation path and acoustic energy originating from the source epicenter although the horizontal acoustic velocity of the latter is consistent with our data the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source the observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic lp events the observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated highly permeable material heating by magmatic activity causes pressure to rise periodically reaching the pressure threshold for rupture of the valve sealing the crack sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack initiating resonance of the remaining fluid subtle waveform and amplitude variability of the infrasonic signals as recorded at an array 13 4 km to the nw of the volcano are attributed primarily to atmospheric boundary layer propagation effects superimposed upon amplitude changes at the source

atmospheric boundary waves excited by the tsunami generation related to the 2011 great tohoku oki earthquake 1 atmospheric pressure changes caused by the 2011 off the pacific coast of tohoku japan earthquake mw 9 0 are investigated sensitive microbarographs in and around japan recorded unequivocal signals associated with the tsunami we identify them as atmospheric boundary waves excited by the uplift and subsidence of the ocean surface on the basis of the waveform characteristics as well as similarity with the data from ocean bottom pressure gauges potential usefulness of an observation network of atmospheric pressure is discussed regarding the improvement of the tsunami warning system

the permian huangshanxi cu ni deposit in western china intrusive extrusive association ore genesis and exploration implications the permian huangshanxi cu ni deposit is the second largest magmatic sulfide deposit discovered to date in a major ni cu province related to protracted basaltic magmatism in eastern xinjiang china it is hosted by a small mafic ultramafic intrusion comprised predominantly of lherzolites olivine websterites gabbronorites and gabbros the huangshanxi intrusion is coeval with permian basalts of tholeiitic and alkaline affinities in the tuha and tarim basins respectively to evaluate a possible genetic relationship between the huangshanxi intrusion and a specific type of coeval basalt in the region as well as ore genesis in the intrusion we have carried out an integrated mineralogical petrological and geochemical study our data reveal that the huangshanxi intrusive rocks are characterized by relatively flat chondrite normalized ree patterns depletion in nb and ta and elevated end values varying between 6 and 10 these features are similar to those of coeval tholeiitic basalts in the nearby tuha basin but are significantly different from those of coeval alkaline basalts in the relatively remote tarim basin the geochemical similarities and differences suggest that the huangshanxi intrusion is genetically related to the tholeiitic basalts in the tuha basin not to the alkaline basalts in the tarim basin as suggested previously by some researchers this implies that regional exploration for the huangshanxi type cu ni deposits should be centered in the tuha basin instead of the tarim basin more specifically the uplifted areas around the tuha basin where similar intrusions may have been brought close to the surface should be carefully examined for mineralization potential intrusive relations and mass balance constraints from incompatible trace elements and sulfide abundances suggest that the huangshanxi intrusion represents a dynamic magma conduit through which multiple pulses of magma ascended to higher levels or to the surface numerical simulation of magma evolution and mixing calculations using sr nd isotopes indicate that selective assimilation of s bearing crustal materials is important for sulfide saturation during the early stages of magma evolution when lherzolites formed fractional crystallization may have also played a role in the attainment of sulfide saturation during the later stages of magma evolution when olivine websterites and gabbronorites formed in both cases immiscible sulfide droplets were retained in the conduit to form disseminated sulfide lenses while the fractionated silicate liquids and buoyant phases such as plagioclase continued to ascend extremely low pge tenors in the sulfide ores of the huangshanxi deposit suggest that the parental magma was highly depleted in chalcophile elements possibly due to previous sulfide segregation at depth

lithoprobe crustal reflection cross section of the southern canadian cordillera 1 foreland thrust and fold belt to fraser river fault seismic reflection data from the south central canadian cordillera covering the interval from the easternmost metamorphic core complexes near arrow lakes to the fraser river fault system along the fraser river reveal a highly reflective and complex crust the base of the crustal reflectivity interpreted as the reflection moho is clearly delineated by a continuous sharp boundary that is essentially planar and slopes uniformly over a distance of 250 km from about 12 0 s in the east to about 10 5 s in the west this virtual lack of relief at the base of the crust contrasts sharply with surface structures that involve 25 km or more of structural relief some of these surface structures can be readily correlated to structures that are outlined by the reflection data and that can be followed into the middle and lower crust even though part of this area was subjected to large amounts of eocene extension the crust is not divisible into transparent upper and reflective lower layers as it is in parts of the u s cordillera three structural culminations the monashee complex the vernon antiform and the central nicola horst are interpreted on the basis of the reflection configuration and the surface geological relationships to have formed initially during jurassic to eocene compression and then to have been modified and exposed during early and middle eocene extension an example of a compressional structure observed on the profiles is the monashee decollement which can be traced from the surface westward into the lower crust extension is manifested along a variety of normal faults including the regionally extensive low angle okanagan valley eagle river fault system moderately dipping faults such as the columbia river and slocan lake faults and high angle faults such as the quilchena creek and coldwater faults both jurassic to eocene compressional shear zones and early to middle eocene extensional shear zones are listric into the lower crust or moho under the intermontane belt

infrasound tremor from bubble burst eruptions in the viscous shallow crater lake of white island new zealand and its implications for interpreting volcanic source processes abstract white island volcano new zealand produced two periods january february and july 2013 of episodic and persistent eruptions through a viscous shallow mud sulphur pool the eruptions included an initial hemispherical bubble burst which was intermittently followed by an up channel gas jet and finally a late stage heaving of a mud sulphur water suspension the late stage heave was systematically directed south eastward as far as 30 40 m from the vent the associated infrasound time series included harmonic tremor on permanent stations wiz and wsrz detailed inspection showed that the tremor was composed of numerous discrete double pulse events without a strong periodic event repetition the first pulse had highly similar waveforms event to event and a notable distortion of the waveform period between the two infrasound stations located on opposites sides from the directed eruption source the second pulse occurred about 1 5 2 5 s later and was weakly observed on station wsrz where the video can be rigorously linked to the double pulse infrasound signals we interpret aspects of the distinctive eruptive regimes for this case the regime dynamics are driven by the propagation of numerous discrete gas slugs though the shallow viscous muddy crater lake each generating a distinct bubble burst with subsequent eruption heave and associated double pulse infrasound events the double pulse events are the source of the persistent harmonic tremor having fundamental and overtone spectral frequencies but are not interpreted as related to cavity resonance or a repetitious comb function instead the activity is produced by a single event producing a specific two pulse source time function the observed distortion in the first pulse wave period at wiz and wsrz may be ascribed to a doppler shift associated with the directivity observed in the initial jet heave eruption process we surmise that double pulse source dynamics and directivity effects may be generically extended to some examples of subsurface seismic tremor or for tremor associated with geyser eruptions mud volcano eruptions fire fountains from lava lakes and strombolian eruptions

critical factors for the formation of a nickel copper deposit in an evolved magma system lessons from a comparison of the pants lake and voisey s bay sulfide occurrences in labrador canada the voisey s bay nickel copper deposit and the pants lake sulfide occurrences are the most important mineral systems discovered to date within the nain plutonic suite in northern labrador there are many intriguing similarities at both locations both are hosted by relatively small troctolite gabbro bodies that intrude the sulfide bearing paragneiss of the churchill province and these intrusions contain inclusions of the paragneiss similar chemical reactions of the gneissic inclusions with the host magmas are observed at both locations the reactions resulted in the addition of sio2 k2o na2o and sulfur to the magmas and are responsible for sulfide saturation and resultant segregation of immiscible sulfide liquids from the magmas the initial sulfide liquids in both cases were relatively poor in metals containing 2 5 wt ni and 2 wt cu the sulfides at pants lake remained poor in metals because of a lack of subsequent interaction with new chalcophile undepleted magma at voisey s bay the initial sulfides segregated in a dynamic conduit and were subsequently upgraded in metals to 6 wt ni and 3 wt cu by a new surge of undepleted magma using the same conduit these sulfides were then concentrated to form large sulfide bodies in the wider parts of the conduit and its entry to an upper chamber in response to a sudden change of liquid velocity in these environments this study confirms three of the most important factors for the formation of magmatic sulfide deposits in an evolved magma system 1 contamination of magma with sulfide bearing country rock to achieve sulfide saturation 2 a dynamic magmatic system such as a magma conduit to transport large volume of sulfide liquid and to concentrate them in limited localities and 3 upgrading of metals in the sulfide by new chalcophile undepleted magma

subduction induced mantle heterogeneity beneath eastern tianshan and beishan insights from nd sr hf o isotopic mapping of late paleozoic mafic ultramafic complexes abstract extensive late paleozoic mafic ultramafic complexes in the eastern tianshan and beishan regions in the southern central asian orogenic belt caob represent an ideal opportunity to assess the characteristics of the mantle in this area whole rock nd sr and zircon hf o isotopic data from the mafic ultramafic complexes of the jueluotage belt middle tianshan massif and beishan rift were compiled for isotopic mapping end t and 87sr 86sr i values range from 5 5 to 9 5 and 0 702 to 0 706 respectively in the jueluotage belt and from 2 to 11 and 0 703 to 0 710 respectively in the middle tianshan and beishan zircon ehf t and 18o values are in the range of 6 0 17 0 and 4 14 8 00 respectively in the jueluotage belt 1 8 and 5 17 6 30 respectively in the middle tianshan and show large variations of 1 17 and 4 12 respectively in the beishan spatially the 87sr 86sr i ratios of mafic ultramafic complexes increase from the jueluotage belt and beishan to the middle tianshan while the end t values show an opposite trend and reflect a mixing character between depleted mantle and em ii reservoirs zircon ehf t and 18o values exhibit an apparent southward decreasing and increasing trends respectively from the jueluotage belt through middle tianshan to beishan rift their corresponding hf model ages increase continuously from north to south these observations demonstrate that the mantle sources beneath the eastern tianshan and beishan are compositionally heterogeneous which presumably result from significant and variable degrees of subduction related modification we therefore suggest that the late paleozoic subcontinental lithospheric mantle beneath the jueluotage belt was modified by slab derived melts and fluids during the subduction of the junggar ocean whereas the mantle beneath the beishan rift was influenced mainly by slab derived fluids during the subduction of the south tianshan ocean the unique similarities of the middle tianshan mafic ultramafic complexes reflect a two stage modification of their mantle source namely the sequential subduction of the early south tianshan ocean followed by subduction of the junggar ocean thus the subduction induced mantle heterogeneity beneath the caob is probably regional in scope

acoustic multipole source model for volcanic explosions and inversion for source parameters summary volcanic explosions are accompanied by strong acoustic pressure disturbances in the atmosphere with a proper source model these acoustic signals provide invaluable information about volcanic explosion dynamics far field solutions to volcanic infrasound radiation have been derived above a rigid half space boundary and a simple inversion method was developed based on the half space model acoustic monopole and dipole sources were estimated simultaneously from infrasound waveforms stability of the inversion procedure was assessed in terms of variances of source parameters and the procedure was reliable with at least three stations around the infrasound source application of this method to infrasound observations recorded at tungurahua volcano in ecuador successfully produced a reasonable range of source parameters with acceptable variances observed strong directivity of infrasound radiation from explosions at tungurahua are successfully explained by the directivity of a dipole source model the resultant dipole axis in turn shows good agreement with the opening direction of the vent at tungurahua which is considered to be the origin of the dipole source the method is general and can be utilized to study any monopole dipole or combined sources generated by explosions

infrasound associated with 2004 2005 large sumatra earthquakes and tsunami 1 large earthquakes that occurred in the sumatra region in 2004 and 2005 generated acoustic waves recorded by the diego garcia infrasound array the progressive multi channel correlation pmcc analysis is performed to detect the seismic and infrasound signals associated with these events the study is completed by an inverse location procedure that permitted reconstruction of the source location of the infrasonic waves the results show that ground motion near the epicenter and vibrations of nearby land masses efficiently produced infrasound the analysis also reveals unique evidence of long period pressure waves from the tsunami earthquake m9 0 of december 26 2004

magma generation and sulfide saturation of permian mafic ultramafic intrusions from the western part of the northern tianshan in nw china implications for ni cu mineralization compared to permian magmatic ni cu sulfide deposits in the eastern part of the northern tianshan such as huangshan and huangshandong those in the western part e g baixintan and lubei are poorly documented zircon id tims u pb age data 279 7 0 2 ma of lherzolite and la icpms u pb age data 277 8 3 4 ma of a hornblende gabbro suggest the lubei intrusion was emplaced in the early permian the baixintan and lubei mafic ultramafic intrusive rocks are characterized by enrichments of large ion lithophile elements and th and u relative to the high field strength elements as well as depletion of nb and ta relative to mid ocean ridge basalt the 87sr 86sr t 0 70354 0 70713 end t 2 80 to 7 05 and ehf t 2 50 18 4 values for the intrusions indicate that they have assimilated tianshan basement rocks whereas the se s ratios 181 10 6 418 10 6 and 34scdt values 0 13 to 0 90 of the sulfides suggest that crustal sulfur has not been incorporated into the magma the decrease in pd zr with increasing th nb pm indicates that sulfide saturation accompanied crustal contamination the olivine compositions and whole rock chalcophile elements of the baixintan and lubei intrusions imply that the parental magma of the intrusive rocks in the west contains higher chalcophile elements than those in the east which suggests that the mafic ultramafic intrusions in the western part of the northern tianshan should be regarded as favorable ni cu sulfide exploration targets

comparing near regional and local measurements of infrasound from mount erebus antarctica implications for monitoring abstract local 100 s of metres from vent monitoring of volcanic infrasound is a common tool at volcanoes characterized by frequent low magnitude eruptions but it is generally not safe or practical to have sensors so close to the vent during more intense eruptions to investigate the potential and limitations of monitoring at near regional ranges 10 s of km we studied infrasound detection and propagation at mount erebus antarctica this site has both a good local monitoring network and an additional international monitoring system infrasound array is55 located 25 km away we compared data recorded at is55 with a set of 117 known strombolian events that were recorded with the local network in january 2006 75 of these events were identified at is55 by an analyst looking for a pressure transient coincident with an f statistic detection which identifies coherent infrasound signals with the data from january 2006 we developed and calibrated an automated signal detection algorithm based on threshold values of both the f statistic and the correlation coefficient application of the algorithm across is55 data for all of 2006 identified infrasonic signals expected to be strombolian explosions and proved reliable for indicating trends in eruption frequency however detectability at is55 of known strombolian events depended strongly on the local signal amplitude 90 of events with local amplitudes 25 pa were identified at is55 compared to only 26 of events with local amplitudes

genesis of permian granites along the kangguer shear zone jueluotage area northwest china geological and geochemical evidence abstract permian mafic and felsic intrusions occur along the kangguer shear zone ksz in the jueluotage area eastern tianshan northwest china this study focuses on the permian felsic intrusions 288 276 2 ma systematic geological and geochemical investigations show that granite plutons in the western ksz dikan guandao and hongshi have lower al and higher alkali contents than those in the eastern ksz longdong huangshan and baishandong the western granite plutons experienced higher degrees of crystal fractionation than the eastern granite plutons both of the western and eastern permian granite intrusions along ksz were derived from juvenile crust the nd pb isotopic characteristics of which exhibit mixed compositions of dm and emii type mantles both of the western and eastern permian granites along ksz were formed within post collision background the dikan guandao and hongshi plutons in the west ksz sector were formed in an extensional tectonic setting whereas the longdong huangshan and baishandong plutons in the east ksz formed in a compressional tectonic setting

middle cambrian to permian subduction related accretionary orogenesis of northern xinjiang nw china implications for the tectonic evolution of central asia abstract middle cambrian to permian subduction related records are widely distributed in northern xinjiang which can be grouped into the chinese altay east junggar eastern tien shan west junggar yili and tarim domains by integrating paleogeographic and geological data we suppose that the chinese altay east junggar eastern tien shan domain was more closely located to siberia while the west junggar and yili domains occupied an intermediate position near the kazakhstan block in the early paleozoic paleoasian ocean distribution of andean type magmatic arcs island arcs accretionary wedges ophiolitic slices and or microcontinents shows an archipelago paleogeography forming a huge accretionary active margin sequences the tarim domain was on the opposite side of the early paleozoic paleoasian ocean remaining passive margin these tectonic units drifted northwards and approached the southern active margin of the siberian craton in the late paleozoic leading to termination of the paleoasian ocean and formation of a complicated orogenic collage between siberian craton and the tarim block between the end permian and triassic these multiple accretion processes significantly contributed to the lateral growth of central asia

a modified genetic model for the huangshandong magmatic sulfide deposit in the central asian orogenic belt xinjiang western china the huangshandong ni cu deposit is the largest magmatic sulfide deposit discovered to date in the central asian orogenic belt in northern xinjiang western china the host intrusion is a 274 ma composite mafic ultramafic intrusion consisting of four separate intrusive units a large layered gabbroic sequence phase i a sheet like ultramafic body phase ii a dyke like gabbronorite body phase iii and an irregular ultramafic unit phase iv important sulfide mineralization is present in the last three intrusive units predominantly as disseminated and net textured sulfides pyrrhotite pentlandite and chalcopyrite the huangshandong mafic ultramafic intrusive rocks are characterized by arc like geochemical signatures such as low ca content in olivine and negative nb ta anomalies in whole rocks this together with a post subduction setting for the east tianshan in the permian suggests that the source mantle was modified previously by slab derived fluids in the carboniferous the mantle derived magma was ponded in a staging chamber in the lower part of the newly formed arc crust the first batch of magma to arrive at huangshandong was most fractionated and depleted in ni crystallizing fe rich and ni depleted olivine fo67 300 ppm ni the second batch of magma was more primitive crystallizing more primitive olivine fo81 84 the third batch of magma was also highly fractionated and depleted in ni crystallizing fe rich and ni depleted olivine fo72 600 ppm ni the final batch of magma became more primitive again crystallizing the most primitive olivine fo81 86 the occurrence of rounded sulfide inclusions in olivine primocrysts in the huangshandong ultramafic rocks indicates that immiscible sulfide liquid droplets were present during olivine crystallization the ni tenors of disseminated sulfide ores in the gabbronorite dyke vary mainly between 5 and 8 wt which are too high to have been produced by the parental magma of the dyke the ni cu and platinum group elements pge tenors of disseminated sulfide ores in the dyke phase iii and the ultramafic sheet phase ii are remarkably similar these observations together with the sequence of magma emplacement suggest that the sulfide liquids entrapped in the magma of the dyke formed at depth by a previous pulse of more primitive magma the estimated parental magma for the most primitive lherzolites in the huangshandong intrusion contains 10 wt mgo modeling shows that sulfide saturation in the parental magma of the huangshandong lherzolites could have resulted from fractional crystallization significant pge depletions relative to ni and cu in the disseminated sulfide ores of the huangshandong deposit may be due to sulfide retention in the source mantle

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

seismic and acoustic signatures of surficial mass movements at volcanoes abstract surficial mass movements such as debris avalanches rock falls lahars pyroclastic flows and outburst floods are a dominant hazard at many volcanoes worldwide understanding these processes cataloging their spatio temporal occurrence and detecting tracking and characterizing these events would advance the science of volcano monitoring and help mitigate hazards seismic and acoustic methods show promise for achieving these objectives many surficial mass movements generate observable seismic and acoustic signals and many volcanoes are already monitored significant progress has been made toward understanding modeling and extracting quantitative information from seismic and infrasonic signals generated by surficial mass movements however much work remains in this paper we review the state of the art of the topic covering a range of scales and event types from individual rock falls to sector collapses we consider a full variety of volcanic settings from submarine to subaerial shield volcano to stratovolcano finally we discuss future directions toward operational seismo acoustic monitoring of surficial mass movements at volcanoes

infrasound associated with the 2002 denali fault earthquake alaska 1 infrasonic waves associated with the november 3 2002 magnitude 7 9 earthquake in alaska were detected by the microphone array i53us in fairbanks alaska the epicenter of the earthquake lay some 150 km south of the fairbanks array both seismic and acoustic signals were recorded successively by the microphone array the fault rupture of the earthquake moved east southeast along the denali totschunda system fault for approximately 294 km the northern side of the fault moved to the east and vertically upward relative to the southern side displacements up to 8 8 meters were measured at various points along the fault eberhart phillps et al 2003 the seismic p wave signal arrived at the array approximately 27 seconds after initiation of the rupture with a trace velocity of 5 km sec this was followed some 12 minutes later by an infrasonic wavetrain that had an average trace velocity of 0 34 km sec and lasted about ten minutes the azimuth of arrival of the infrasonic waves steadily moved eastward throughout the wave train apparently following the rupture s leading edge along the fault the largest infrasonic signals reaching over 12 pa came from the azimuth of the regions of largest ground motion along the fault the source of the infrasound is taken to be the sudden local motion of the mountains in the alaska range along the denali fault as they responded to the eastward propagating fault rupture

erratum to a new style of ni cu mineralization related to magmatic breccia pipes in a transpressional magmatic arc aguablanca spain the aguablanca deposit represents a new style of magmatic ni cu mineralization in discordant sulfide rich pyroxenitic breccia pipes the orebody is hosted by variscan calc alkaline diorites and gabbros which intruded during an oblique subduction collision event transpressional transtensional left lateral structures facilitated the intrusion of primitive magmas to shallow depths in the crust a two stage genetic model is proposed in the first stage a transitional deep magma chamber formed the primitive magma interacted at depth with wall rocks resulting in extensive crustal contamination concomitant sulfide magma immiscibility and settling of orthopyroxene clinopyroxene and sulfide rich cumulates to form a layered magmatic complex geochemical and mineralogical evidence including the virtual disappearance of olivine heavy 34s values 7 4 distinctive nd sr and pb signatures high au contents and the presence of spinel and graphite indicate a major interaction with the upper crust probably with pyrite rich carbonaceous slates of late proterozoic age the second stage was related with the emplacement of residual calc alkaline gabbroic to noritic melts and the development of an intrusive breccia containing fragments of the consolidated layered complex rocks and associated disseminated to massive sulfides

petrogenesis and ore genesis of the permian huangshanxi sulfide ore bearing mafic ultramafic intrusion in the central asian orogenic belt western china abstract the permian huangshanxi mafic ultramafic intrusion hosts one of the two largest magmatic sulfide deposits in the eastern tianshan which is situated in the southern margin of the central asian orogenic belt in this paper we use mineral compositions and whole rock geochemical data to decipher the genetic relationship between magma evolution and sulfide mineralization the huangshanxi intrusion consists of three separate intrusive units important sulfide mineralization occurs in the base of the last intrusive unit an elongated layered ultramafic body composed of lherzolite at the bottom olivine websterite in the middle and websterite at the top based on olivine liquid equilibria and mass balance the mgo and feo contents in the parental magma for a lherzolite sample are estimated to be 8 71 and 8 36 wt respectively the huangshanxi mafic ultramafic intrusive rocks and the estimated trapped liquids for several olivine orthopyroxene cumulate rocks all show light rare earth element enrichments relative to heavy rare earth elements and significant nb depletions relative to th and la which are similar to the characteristics of coeval basalts in the region the arc like geochemical features are attributed to pre permian mantle metasomatism by slab derived fluids partial melting of the previously modified mantle is thought to have resulted from heating by upwelling asthenosphere associated with post subduction lithosphere delamination or by mantle plume activity the relationship between the fo and ni contents of olivine crystals from the huangshanxi sulfide poor ultramafic rocks in situ differentiation stage during which the sulfide droplets and olivine crystals settled to form the sulfide olivine cumulate zones at the base of the huangshanxi magmatic system

the effect of trapped liquid crystallization on cumulus mineral compositions in layered intrusions a series of calculations have been carried out to evaluate the effect on cumulus mineral compositions of solidification of trapped intercumulus liquid in orthocumulates the calculation assumes local equilibrium between phases and that the system remains chemically closed during crystallization of the trapped liquid the latter assumption is held to be valid on a scale of tens to hundreds of centimeters it is not necessary to know the composition of the trapped liquid as the calculation only requires an estimate of feo content and trapping temperature the change in composition of a mineral from that of the initially precipitated cumulus crystals to the final composition after complete solidification is termed the trapped liquid shift its magnitude depends on the modal proportions of cumulus phases and the initial porosity and is only weakly dependent on initial phase compositions trapped liquid shifts are significant when compared with mineral composition changes occurring during fractional crystallization crystallization of 30 trapped liquid gives rise to shifts of up to 10 mol percent in mg number of olivine or pyroxene the size of the shift becomes greater when the initial cumulus assemblage has a lower total feo mgo content and vice versa as a result of the relationship between trapped liquid shift and cumulus mode mineral composition variations and trends may be generated in sequences of cumulates which originally had constant compositions of cumulus minerals for example in a cyclic unit grading from a pyroxenitic base to an anorthositic top crystallization of a uniform proportion of trapped liquid will result in an apparent iron enrichment trend from bottom to top of the cycle as has been observed in the upper critical zone of the bushveld complex

influence of near source volcano topography on the acoustic wavefield and implication for source modeling in near source conditions 5 km the atmosphere is often assumed to be fully transparent to acoustic waves and to have a small effect on the acoustic wavefield as a consequence the propagation of the acoustic waves in the atmosphere near the source is often neglected and waveform is compensated only in amplitude by the inverse of the distance from the source however the amplitude distribution at five infrasonic stations deployed around the active craters of the stromboli volcano reveals anomalous decay up to 11 db larger than expected which cannot be explained in terms of energy loss for geometrical spreading the distribution of amplitude decay changes for different source positions suggesting a strong relationship with the source to receiver path geometry by using 2d fdtd modeling we show that the anomalous amplitude distribution of the acoustic waves at stromboli is not necessarily due to the source radiation pattern but it is strongly influenced by the topography of the ground atmosphere interface diffraction and reflection of topography contaminate the acoustic wavefield and have a strong effect in reducing the amplitude and altering the waveform our work demonstrates that line of sight conditions are quite difficult to be achieved in acoustic experiments and that a detailed knowledge of the topography along the crater receiver path is necessary whenever infrasound waveforms are used to invert for the source process

infrasonic precursors to a vulcanian eruption at sakurajima volcano japan the may 1998 eruption sequence of sakurajima volcano was monitored by ten infrasonic stations ten seismometers and a video camera during this seismo acoustic experiment we recorded hundreds of infrasonic tremor and long period events associated with seismic signals and observed a progression from relative quiescence to a vulcanian eruption the number of infrasonic events increased with escalating volcanic activity and the dominant character of the infrasonic signals changed from impulsive to emergent at 22 17 of may 19 sakurajima released ash and gases to a height of 2 km above the vent an event that was recorded continuously by one infrasonic and two seismic stations we present the experimental setup as well as a procedure through which infrasonic signals may be incorporated into future eruption monitoring and forecasting algorithms for open vent volcanic systems in addition our recordings suggest that infrasonic signals are more representative of processes occurring within the volcanic interior than are seismic signals which are strongly altered by diffraction and scattering in the volcanic edifice

volcano infrasound a review abstract exploding volcanoes which produce intense infrasound are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent as opposed to seismic signals which are generated by both surface and internal volcanic processes as with seismology infrasound can be recorded remotely during inclement weather or in the dark to provide a continuous record of a volcano s unrest moreover it can also be exploited at regional or global distances where seismic monitoring has limited efficacy this paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity many infrasound studies have focused on integration with other geophysical data including seismic thermal electromagnetic radiation and gas spectroscopy and they have generally improved our understanding of eruption dynamics other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk this paper aims to provide an overview of volcano airwave studies from analog microbarometer to modern pressure transducer and summarizes how infrasound is currently used to infer eruption dynamics it also outlines the relative merits of local and regional infrasound surveillance highlights differences between array and network sensor topologies and concludes with mention of sensor technologies appropriate for volcano infrasound study

melting reactions of gneissic inclusions with enclosing magma at voisey s bay labrador canada implications with respect to ore genesis the voisey s bay ni cu co sulfide deposit is associated with a 1 333 ga troctolitic gabbroic intrusion which transects the 1 85 ga collisional boundary between tasiuyak paragneiss of the proterozoic aged churchill province to the west and orthogneiss of the archean aged nain province to the east the intrusion comprises an upper chamber to the east the eastern deeps subchamber a lower chamber to the west the reid brook subchamber and a conduit connecting them sulfide mineralization is closely associated with a breccia which occurs close to the basal contact of the eastern deeps subchamber and within the conduit the breccia is composed of abundant tasiuyak paragneiss inclusions with a troctolitic gabbroic matrix the gneiss inclusions have reacted extensively with the enclosing magma in general the degree of reaction increases from the reid brook subchamber through the conduit to the eastern deeps subchamber in the course of this reaction garnet has been oxidized to form hercynite and magnetite with the release of sio2 to the magma cordierite has been dehydrated to form hercynite with the release of sio2 hypersthene and k feldspar have reacted together to produce hercynite with the release of sio2 and k2o plagioclase has broken down to produce corundum losing sio2 and na2o to the magma and itself becoming enriched in anorthite and the corundum has subsequently reacted with feo and mgo from magma to form hercynite the color of the hercynite changes progressively from beige in the reid brook subchamber through green within the conduit to black in the eastern deeps subchamber this color change reflects an increase in feal2o4 at the expense of the mgal2o4 in the hercynite the inclusions in the eastern deeps subchamber characteristically show a series of reaction rims ranging from labradorite through biotite to hypersthene it is seen that reaction with the gneiss inclusions results in the addition of sio2 k2o and na2o to the magma this felsification of magma has resulted in a decrease in its ability to dissolve sulfide and therefore has promoted sulfide immiscibility

heat flow and flexure at subduction zones 1 it is often suggested that heat flow in the incoming plate at subduction zones is lower than expected for crust of that age due to increased hydrothermal circulation from flexure extending about 300 km seaward of the trench and faulting observed starting about 50 75 seaward of the trench testing this suggestion using global heat flow data shows no significant difference between heat flow near the trench and the global means for the same age crust however on average heat flow in the overriding plate is about 60 of that in the incoming plate

geochemistry and petrogenesis of 270 ma ni cu pge sulfide bearing mafic intrusions in the huangshan district eastern xinjiang northwest china implications for the tectonic evolution of the central asian orogenic belt abstract the central asian orogenic belt caob is composed of remnants of microcontinents island arcs and ophiolites the presence of voluminous phanerozoic a type granites suggest that continental growth occurred through addition of juvenile crust and the presence of mafic ultramafic intrusions provides direct evidence for a mantle contribution the origin of the mafic ultramafic intrusions in the huangshan area eastern xinjiang has been debated because of the lack of precise age data or trace element and isotopic analyses we have studied the geology petrology geochemistry and geochronology of two of the intrusions the huangshanxi and huangshandong intrusions both are typical layered mafic ultramafic intrusions composed of diorite troctolite norite gabbronorite gabbro wehrlite websterite and lherzolite with systematic geochemical variations that are consistent with the following crystallization sequence ol chr ol pyx chr cpx pl and hbl bt igneous zircons separated from a diorite in the huangshanxi intrusion yield a 269 2 ma shrimp u pb age the rocks are enriched in rb ba u k sr relative to th and lree depleted in nb ta relative to th and exhibit positive end values 6 7 to 9 3 ni cu pge sulfide mineralization occurs in the lower parts of the intrusions primarily strata bound within wehrlite or lherzolite and locally stratiform along the margins of the intrusions the parental magmas appear to have been derived from a mantle source that was previously contaminated by subduction of oceanic crust and to have been variably contaminated by upper continental crustal components the intrusions appear to have formed by plume related activity within a continental setting likely related to post orogenic extension following carboniferous amalgamation of arc related terranes in the caob this plume activity was most likely also responsible for providing heat sources to generate large amounts of a type granites across the caob

skeletons and fractals a statistical approach to deep crustal seismic data processing and interpretation abstract coherent seismic reflection events are identified using seismic skeletonization an automatic pattern recognition technique in which waveforms are parameterized such that the attributes of each event are identified and stored in a relational database or event file this new approach to seismic interpretation allows statistical analyses of the attributes including estimation of scaling laws for reflectivity observed on deep seismic data and development of new filtering techniques based on characteristics such as dip and reflection event length applications of the technique to deep crustal reflection data sets from the alberta basement transect of the lithoprobe project assist interpretation in areas that lack surface outcrop or other means of relating reflections from the deep crust to the surface

reevaluation of the role of external sulfur addition in the genesis of ni cu pge deposits evidence from the nebo babel ni cu pge deposit west musgrave western australia the nebo babel ni cu pge sulfide deposit located in the west musgrave block western australia is hosted within a tube like concentrically zoned gabbronorite magma conduit emplaced at 1068 ma the nebo babel deposit is associated with the ca 1078 ma giles complex which is part of the warakurna large igneous province previous geologic and geochemical studies have shown that the nebo babel consists of chemically related but temporally distinct magma pulses the initial magma pulses which were the most primitive and the most contaminated formed the marginal units of the conduit the later pulses were emplaced into the core of the conduit the chilled margin rocks contain sulfide globules mineralization is confined to the early magma pulses and consists of massive sulfide breccias and stringers and disseminated gabbronorite hosted sulfides the ni tenor of the massive sulfides which have undergone sulfide liquid fractionation and the disseminated sulfides are almost the same indicating that both formed at similar r factors the whole rock massive and disseminated sulfides contain 650 ppb and 60 to 500 ppb total pge respectively all of the nebo babel rock units are slightly pge depleted with cu pd ratios higher than primitive mantle indicating early saturation and segregation of a sulfide and or pgm rocks with trace cumulus sulfides have the lowest cu zr and highest cu pd ratios and the most fractionated metal patterns indicating that these units have undergone the highest degrees of ni cu and pge depletion the average 34s value of all nebo babel disseminated and massive sulfides is 0 4 0 2 per mil which is consistent with the s originating in the mantle sulfur saturation did not occur in situ and is inferred to have been triggered by assimilation of felsic orthogneiss perhaps in the parental magma chamber this initial magma pulse with entrained sulfides formed marginal units of the nebo babel intrusion some of the entrained sulfides accumulated within physical traps on the way into the conduit and or at the exit from the chamber these sulfides were later emplaced along the footwall contact as massive and or marginal fragment laden sulfide liquid distribution of the disseminated sulfides was influenced by the conduit geometry and magma flow dynamics the final and volumetrically dominant barren magma pulse underwent crystal fractionation and oxide precipitation in the core of the nebo babel intrusion which in turn caused sulfide saturation and formed trace but pge depleted sulfides in these units the nebo babel deposit has a number of features in common with other ni cu pge deposits hosted in dynamic magma conduits e g voisey s bay such as multiple magma pulses and sulfide entrainment from depth rather than in situ sulfide segregation however si addition was the primary cause of sulfide saturation and external s addition did not play a role in the genesis of the nebo babel deposit

infrasound monitoring of volcanoes to probe high altitude winds 1 active volcanoes in the vanuatu archipelago permanently generate infrasonic waves their monitoring over 1 year exhibits clear seasonal trends in the direction of arrival of the detected signals from summer to winter the azimuth variation reaches 15 this deviation is essentially due to the reversibility of the zonal stratospheric wind with season which strongly affects the deflection of the ray direction a three dimensional 3 d ray tracing modeling roughly explains the observed seasonal trend in the azimuth variation but underestimates its amplitude the discrepancy between the measurements and the results of simulation is explained by undervalued wind speeds in the upper atmosphere infrasonic observations are used as input of an inversion scheme for adjusting the vertical structure of the wind in the upper stratosphere and mesosphere it is shown that the mesospheric zonal winds are underestimated by at least 20 m s throughout the year with differences reaching 50 m s

geochemistry of the kalatongke ni cu pge sulfide deposit nw china implications for the formation of magmatic sulfide mineralization in a postcollisional environment the kalatongke also spelt as karatungk ni cu platinum group element pge sulfide deposit containing 33 mt sulfide ore with a grade of 0 8 wt ni and 1 3 wt cu is located in the eastern junggar terrane northern xinjiang nw china the largest sulfide ore body which occupies more than 50 vol of the intrusion y1 is dominantly comprised of disseminated sulfide with a massive sulfide inner zone economic disseminated sulfides also occur at the base of the intrusions y2 and y3 the main host rock types are norite in the lower part and diorite in the upper part of each intrusion enrichment in large ion lithophile elements and depletion in heavy rare earth elements relative to mid ocean ridge basalt indicate that the mafic intrusions were produced from magmas derived from a metasomatized garnet lherzolite mantle the average grades of the disseminated ores are 0 6 wt ni and 1 1 wt cu whereas those of the massive ores are 2 wt ni and 8 wt cu the pge contents of the disseminated ores 14 69 ppb pt and 78 162 ppb pd are lower than those of the massive ores 120 505 ppb pt and 30 827 ppb pd however on the basis of 100 sulfide pge contents of the massive sulfides are lower than those of the disseminated sulfides very high cu pd ratios 4 5 104 indicate that the kalatongke sulfides segregated from pge depleted magma produced by prior sulfide saturation and separation a negative correlation between the cu pd ratio and the pd content in 100 sulfide indicates that the pge content of the sulfide is controlled by both the pge concentrations in the parental silicate magma and the ratio of the amount of silicate to sulfide magma the negative correlations between ir and pd indicate that the massive sulfides experienced fractionation

late paleozoic mafic ultramafic intrusions in southern central asian orogenic belt nw china insight into magmatic ni cu sulfide mineralization in orogenic setting abstract the mafic ultramafic intrusions hosting magmatic ni cu sulfide ore deposits usually present within the precambrian cratons and on their margin have been extensively studied whereas those occurring within the phanerozoic orogenic belts have received little attention the southern margin of the central asian orogenic belt is a region of late paleozoic mafic ultramafic intrusions emplaced during post orogenic stage in order to recognize the mineralization features this study compares barren or weakly mineralized mafic ultramafic intrusions in the beishan with those hosting ni cu sulfide ore deposit in the altay and eastern tianshan in petrology mineralogy and geochemistry aspects several mineralization features can be recognized with respects to petrology mineralogy and geochemistry from comprehensive comparisons among the mineralization indicators we highlight strong alteration accompanying sulfide emplacement post erosion exposure of magma conduit abundant primary hydrous minerals and potential transportation mechanism of ore forming elements other indicators are the presence of orthopyroxene and pyroxenite for potential sulfide formation through crystal fractionation restricted fo and ni ranges in olivines for sulfide segregation and some other special geochemical characteristics related to crustal contamination the variation in mineralization could be ascribed to different degrees of partial melting crustal assimilation and subduction related modification of a mantle source we suggest that the ni cu sulfide mineralization of mafic ultramafic intrusions within orogenic belts is remarkably different from that of cratonic and continental marginal settings in respects of petrogenesis and mineralizing mechanism magmatic conduit type ni cu sulfide ore deposit is a target for future prospecting and exploration for mafic ultramafic intrusions in the orogenic belts

finite difference time domain modeling of transient infrasonic wavefields excited by volcanic explosions 1 numerical modeling of waveform diffractions along the rim of a volcano vent shows high correlation to observed explosion signals at karymsky volcano kamchatka russia the finite difference modeling assumed a gaussian source time function and an axisymmetric geometry a clear demonstration of the significant distortion of infrasonic wavefronts was caused by diffraction at the vent rim edge data collected at karymsky in 1997 and 1998 were compared to synthetic waveforms and variations of vent geometry were determined via grid search karymsky exhibited a wide range of variation in infrasonic waveforms well explained by the diffraction and modeled as changing vent geometry rim diffraction of volcanic infrasound is shown to be significant and must be accounted for when interpreting source physics from acoustic observations

influence of atmospheric structure and topography on infrasonic wave propagation the effects of topography and atmospheric structures on infrasonic wave propagation from a volcanic source were investigated using observations and numerical modeling this paper presents the first long term observational data set showing spatiotemporal variations in patterns of infrasound propagation at distances of up to 60 km from a persistently active infrasound source sakurajima volcano japan the data show that the amplitudes of infrasonic waves received at distant stations relative to those received at a reference station close to the source can vary up to an order of magnitude over short time intervals and short distances and that they do not follow the theoretical geometric decay expected for homogeneous media moreover waveforms also change significantly in both time and space numerical simulations were performed using a two dimensional finite difference time domain 2 d fdtd method effects of atmospheric structure and topography are included in a vertical section parallel to the wave propagation direction the simulation successfully reproduced the variations of amplitudes and waveforms results are interpreted in terms of wave refraction due to sound and wind speed gradients and wave diffraction at topographic barriers our numerical results indicate that both atmospheric and topographic propagation effects are nonnegligible to evaluate the propagation effects and determine source processes in spatially and temporally varying infrasound data atmospheric data with a time resolution higher than is currently available are required if the data are available the present results suggest that the propagation effects could be evaluated using 2 d fdtd modeling at realistic calculation times

infrasound from tungurahua volcano 2006 2008 strombolian to plinian eruptive activity abstract strombolian to plinian activity from tungurahua volcano ecuador has been recorded by the autonomous infrasound arrays of the acoustic surveillance for hazardous eruptions ashe project since early 2006 our studies suggest that acoustic energy release during large eruptions does appear to broadly scale with eruption intensity this manuscript provides a detailed chronology and characterization of tungurahua s eruptive activity between 2006 and 2008 and demonstrates the ability to constrain source parameters of significant eruptions such as onset duration and escalation at regional distances by combining infrasound and remote sensing techniques the ashe system in ecuador automatically detected over 20 000 volcanic explosions at an array 37 km from tungurahua and was successful at notifying the onset escalation and cessation of a hazardous february 2008 eruption with a latency of 5 min elevated infrasonic energy from sustained and intense tungurahua eruptions correlates well with ash column heights and their lateral extent during the study period the spectra of these sustained explosive eruptions appear to be recurrent readily recognizable and indicative of volcanic jetting and significant atmospheric ash injection the paroxysmal plinian phase of the august 2006 eruption produced an ash cloud that extended well into the stratosphere 24 km coinciding with a shift of the dominant jetting frequency from 0 25 hz to below 0 1 hz and radiation of over 5 107 w of acoustic power transient explosions were often marked by minor or no ash release and are presumed to be more gas rich a change in the acoustic spectrum of volcanic jetting was also detected in the transition from a sustained to collapsed eruption column at the end of the july 14 2006 eruption the jetting spectrum at tungurahua during a period of sustained pyroclastic density current production changes from a typical double peaked to a single peaked spectrum suggesting remote acoustic monitoring can help ascertain the stability and dynamics of an eruptive column

late paleozoic post collisional magmatism in the eastern tianshan belt northwest china new insights from geochemistry geochronology and petrology of bimodal volcanic rocks abstract the late carboniferous to permian marks an important phase of terrane amalgamation through accretion collision in the central asian orogenic belt caob the tianshan belt forms part of this sequence where the post collisional event generated an e w trending bimodal volcanic zone that extends for ca 500 km from the southern bogda mt to the easternmost tianshan belt here we report the petrology geochemistry and geochronology of the bimodal volcanic rocks to characterize the post collisional tectonic evolution in late paleozoic the major element chemistry of the basalt and rhyolite samples indicates a bimodal high k calc alkaline affinity the basalts are characterized by high abundance in tio2 th u and pb and depletion in nb ta and p together with slight enrichment in lree contents and low hfse lree ratios the rhyolites show a close affinity to aluminous a type granites with enrichment in k na zr ce y and depletion in p nb ta and ti they also exhibit fractionated ree patterns with prominent negative eu anomalies the petrographic and geochemical data suggest that this bimodal rock series was generated in a post collisional setting the mafic rocks are likely derived from a metasomatized lithospheric mantle assimilation of different crustal components played a minor role in the genesis of these basaltic rocks the la icp ms analysis on zircons from four rhyolites and two basalts yielded similar ages ranging from 295 8 2 8 to 293 3 1 7 ma suggesting an early permian event zircons from the basalts show a wide ehf t range from 0 49 to 13 whereas those from the rhyolites show two groups of ehf t values from 5 to 3 and from 6 to 12 suggesting a mixing of crust mantle material the magmatic zircons from the bimodal volcanic rocks yielded two peaks of tdm2 between 600 820 ma and 1160 1360 ma probably representing two significant episodes of continental crust growth the bimodal volcanic rocks are correlated with the early stage of post collision our results suggest that vertical crustal growth through mantle derived magmas in post collisional setting also played a major role in the construction of the caob

skeletonization of aeromagnetic data skeletonization is a syntactic pattern recognition method that is applied to gridded data to produce an automatic line drawing with an associated event catalog previous implementations of skeletonization have been tailored for seismic data here we modify that technique to render it more suitable for other types of gridded data with particular emphasis on aeromagnetic maps a modification from previous schemes is the use of a two pass approach to reduce the effects of an otherwise problematic directional bias that discriminates against events oriented parallel to columns of the grid the method can be used effectively for filtering aeromagnetic data on the basis of strike direction event linearity event amplitude and polarity it is based on the delineation of peak trough pairs cycles which are traced throughout the grid to form contiguous events cycles and events are characterized by attributes that include amplitude polarity and pulse width events are further characterized by length average strike direction and linearity the event attributes are stored in a catalog thus enabling one to perform attribute based analysis and data filtering we illustrate our algorithm using two regional aeromagnetic examples from different parts of the canadian shield the first from the great slave lake shear zone is dominated by linear anomaly trends produced by faults and mafic dikes the second from the manicouagan region of northeastern quebec contains abundant subcircular and arcuate anomaly patterns caused by large intrusive complexes and a meteorite impact structure

origin of deccan trap lavas evidence from combined trace element and sr nd and pb isotope studies abstract geochemical and isotope results are presented from a new study of the most southern basalts in the deccan trap india three chemical formations are recognised two of which can be correlated with the established stratigraphy in mahabaleshwar and imply a regional southerly dip of 0 06 over a distance of 250 km in detail sr isotope variations within the ambenali and mahabaleshwar formations can be shown to reflect three distinct end members which provide new constraints for petrogenetic models pb isotope data for selected basalts exhibit a wide range with 206 pb 204 pb 16 87 22 45 and a linear correlation on a pb pb diagram the least contaminated ambenali basalts plot within the pb array and interaction with mantle lithosphere involves a shift to less radiogenic pb whereas contamination with crust is characterised by more radiogenic pb unlike the karoo and parana continental flood basalt provinces only four flow units within the southern deccan appear to contain a significant contribution from mantle lithosphere the mahabaleshwar and ambenali formation basalts exhibit a striking negative pb sr isotope trend which is presently regarded as one of the features of interaction with shallow level lithospheric mantle it further suggests that basalts from the walvis ridge kerguelen and ninetyeast ridge all remobilised such shallow level material and that the deccan basalts which were not affected by crustal contamination reflect interaction between asthenospheric material similar to t type morb but related to the reunion hotspot and continental mantle lithosphere of the indian plate

identification and interpretation of azimuthally varying crustal reflectivity with an example from the southern canadian cordillera a new approach to seismic interpretation seismic skeletonization is used to analyze crustal reflection data by identifying numbers of reflection events their lengths their energies and their dips with respect to azimuths of recorded profiles application of the method to crustal reflection data in the southern canadian cordillera demonstrates strong directional dependence of crustal reflectivity with persistent trends at 025 040 205 220 085 095 265 275 115 125 295 305 and 140 160 320 340 these trends are visible in both the upper and lower crust and may be related to regional structural trends further applications of the technique particularly in different tectonic regions may allow categorization of seismic patterns and cataloguing of signatures for complex reflection data in a manner similar to seismic stratigraphy and structural patterns in stratified rocks

volume flow rate estimation for small explosions at mt etna italy from acoustic waveform inversion this study was supported by nerc grant ne p00105x 1 and by european unions horizon 2020 research and innovation programme under the marie sklodowska curie grant agreement 798480

delineation of surfaces by skeletonization application to interpretation of 3d seismic reflection and georadar data volumes a new 3 d skeletonization technique based on a four cycle correlation allows automatic event detection and mapping of surfaces in any 3 d volume of reflection seismic data interpretation results are comparable to those derived using conventional 3 d interpretation packages furthermore a product of skeletonization is a surface file containing a variety of seismic attributes for each identified surface that can be accessed for detailed statistical analysis

fractals in deep crustal seismic reflection profiles application of a syntactic pattern recognition technique seismic skeletonization to deep crustal seismic reflection data allows attributes such as energies lengths and dips to be associated with individual reflection events some of these attributes exhibit fractal properties e g the relationship between seismic event lengths and their spatial distribution throughout the crust this approach provides a new technique to analyse complex geometry on seismic reflection data

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

a stochastic view of lower crustal fabric based on evidence from the ivrea zone despite its complicated history the ivrea zone is considered to be a representative surface exposure of extended continental crust we have digitized two standard 1 25 000 geological maps from this area and evaluated their structural statistics because of the subvertical orientation of the ivrea zone these maps can be considered as small scale cross sections through the lower continental crust the autocorrelation functions of the digitized lithologies measured from these maps show a clear self similar or fractal rather than a gaussian or deterministic trend we found that an anisotropic von karman correlation function with an aspect ratio around 4 and a hurst number of 0 3 corresponding to a fractal dimension of 2 7 matches the observed data our results represent an explicit confirmation of previous indirect evidence for the fractal nature of lithospheric heterogeneities and provide the means to construct realistic crustal scale seismic models of ivrea type lower continental crust

geochronology petrology and hf s isotope geochemistry of the newly discovered xiarihamu magmatic ni cu sulfide deposit in the qinghai tibet plateau western china this paper reports the first set of data for the newly discovered xiarihamu magmatic ni cu sulfide deposit in the eastern kunlun paleozoic arc terrane which is located in the northern part of the qinghai tibet plateau an on going drilling campaign reveals 100 million tons of sulfide mineralization with the average grade of 0 8 wt ni and 0 1 wt cu for the deposit this makes the xiarihamu deposit one of the 20 largest magmatic ni cu sulfide deposits in the world and the largest ever found in arc settings the deposit is hosted in a small ultramafic body intruding older gabbroic and metamorphic rocks new zircon u pb isotope age data reveal that the ultramafic body 411 6 2 4 ma is 20 ma younger than the host gabbroic intrusion 431 3 2 1 ma the ultramafic body is composed predominantly of lherzolite and olivine websterite with minor dunite websterite and orthopyroxenite mineralization mainly occurs as sub horizontal to gently dipping 30 disseminated sulfide zones that are generally concordant with the lithological structure of the ultramafic intrusion the lateral extension and thickness of individual mineralized zones are up to 200 m and 100 m respectively sulfide mineral assemblages are composed of pyrrhotite pentlandite and chalcopyrite the xiarihamu ultramafic rocks show light ree enrichments and pronounced negative nb anomalies plus significant ca depletion in olivine 700 ppm ca which are characteristic of many arc basalts in the world olivine crystals in the xiarihamu ultramafic rocks have relatively primitive compositions with fo contents up to 90 mol close to the mantle value the contrasting ni contents of olivine crystals with similar fo contents from different sulfide mineralized zones in a single drill core indicate that at least two pulses of sulfide laden magma with different ni compositions were involved in the development of the deposit estimated parental magma for the xiarihamu lherzolites contains 52 4 wt sio2 and 9 8 wt mgo which are within the ranges of boninites worldwide supporting the interpretation that the xiarihamu sulfide ore bearing ultramafic intrusion is the product of subduction related boninitic magmatism the ehf t values of zircon crystals from the xiarihamu ultramafic rocks vary from 1 to 5 indicating minor crustal contamination of the parent magma the involvement of external sulfur in the genesis of the xiarihamu magmatic sulfide deposit is evident from higher 34s values of sulfide ores 3 5 to 6 8 than typical mantle value 0 2 although the actual contaminants are yet to be identified

a global study of volcanic infrasound characteristics and the potential for long range monitoring abstract volcanic infrasound from explosive eruptions is detectable at distances up to 1000 s of km and is often recorded on the international monitoring system ims infrasound network though infrasound produced by individual volcanoes has previously been studied more general relationships between infrasound characteristics and eruption parameters remain unclear therefore using a dataset comprising 110 events at 39 globally distributed volcanoes we assess the ability of the ims to monitor remote volcanoes and investigate whether volcanic infrasound exhibits consistent trends across a range of eruption styles and intensities acoustic pressure amplitude and frequency content of the volcanic infrasound were measured and acoustic energy was also calculated these were compared along with the maximum distance of detection for each event to the maximum plume height reported for the event which was used as a proxy for event intensity of the events investigated 62 were detected by at least one infrasound station the maximum distance at which an event was detected generally increased with the plume height and infrasound produced during the eruption of manam png in january 2005 which produced a plume which rose over 20 km above the summit was detected at a distance of 10 671 km total acoustic energy and acoustic pressure amplitude corrected for geometrical spreading increased with plume height whilst the lowest frequency present in the volcanic infrasound decreased additionally relationships seen between infrasound characteristics and eruption plume height indicate that analyses of this data alone could constrain vital estimates of plume heights for otherwise un observed eruptions taken together these findings indicate that if made available for this purpose in the future the ims infrasound network could complement existing monitoring techniques by detecting and characterising eruptions at remote volcanoes which often have no local monitoring networks