surface wave tomography of the western united states from ambient seismic noise rayleigh and love wave phase velocity maps summary we present the results of rayleigh wave and love wave phase velocity tomography in the western united states using ambient seismic noise observed at over 250 broad band stations from the earthscope usarray transportable array and regional networks all available threecomponent time series for the 12 month span between 2005 november 1 and 2006 october 31 have been cross correlated to yield estimated empirical rayleigh and love wave green s functions the love wave signals were observed with higher average signal to noise ratio snr than rayleigh wave signals and hence cannot be fully explained by the scattering of rayleigh waves phase velocity dispersion curves for both rayleigh and love waves between 5 and 40 speriod were measured for each interstation path by applying frequency time analysis the average uncertainty and systematic bias of the measurements are estimated using a method based on analysing thousands of nearly linearly aligned station triplets we find that empirical green s functions can be estimated accurately from the negative time derivative of the symmetric component ambient noise cross correlation without explicit knowledge of the source distribution the average traveltime uncertainty is less than 1 s at periods shorter than 24 s we present rayleigh and love wave phase speed maps at periods of 8 12 16 and 20 s the maps show clear correlations with major geological structures and qualitative agreement with previous results based on rayleigh wave group speeds

a balanced section across the pyrenean orogenic belt evolutionary models that have been proposed for the pyrenean orogenic belt involve gravitational gliding of major thrust sheets to both the north and south of an uplifted central axial zone it has been suggested by previous workers that uplift is a result of alpine compression or long lived strike slip movement on the north pyrenean fault we critically assess these models and propose a new model based on the generation of a thin skinned linked thrust system due to alpine collision of iberia and europe pyrenean alpine tectonics is dominated by southward thrusting on a major sole fault dipping north at approximately 6 within hercynian basement northerly directed thrusts of the north pyrenean zone and northern folded foreland are backthrusts from this sole fault a total orogenic shortening of 106 km in the central pyrenees was achieved between the palaeocene and oligocene at a time averaged rate of 0 62 cm yr 1 a thin skinned model requires that the north pyrenean fault is truncated by both northward and southward moving thrusts and occurs in the footwall of the sole fault some 60km north of its present surface trace

co magmatic sulfides and sulfates in the udachnaya east pipe siberia a record of the redox state and isotopic composition of sulfur in kimberlites and their mantle sources kimberlites of the udachnaya east pipe siberia include a uniquely dry and serpentine free rock type with anomalously high contents of chlorine cl 6 1 wt alkalies na2o k2o 10 wt and sulfur s 0 50 wt referred to as a salty kimberlite the straightforward interpretation is that the na k cl and s rich components originate directly from a carbonate chloride kimberlitic magma that is anhydrous and alkali rich however because brines and evaporites are present on the siberian craton previous studies proposed that the kimberlitic magma was contaminated by the assimilation of salt rich crustal rocks to clarify the origin of high cl alkalies and s in this unusual kimberlite here we determine its sulfur speciation and isotopic composition and compare it to that of non salty kimberlites and kimberlitic breccia from the same pipe as well as potential contamination sources hydrothermal sulfides and sulfates country rock sediment and brine collected in the area the average 34s of sulfides is 1 4 2 2 in the salty kimberlite 2 1 2 7 in the non salty kimberlites and 14 2 5 8 in the breccia the average 34s of sulfates in the salty kimberlites is 11 1 1 8 and 27 3 1 6 in the breccia in contrast the 34s of potential contaminants range from 20 to 42 for hydrothermal sulfides from 16 to 34 for hydrothermal sulfates 34 for a country rock sediment chukuck suite and the regional brine aquifer our isotope analyses show that 1 in the salty kimberlites neither sulfates nor sulfides can be simply explained by brine infiltration hydrothermal alteration or the assimilation of known salt rich country rocks and instead we propose that they are late magmatic phases 2 in the non salty kimberlite and breccia brine infiltration lead to sulfate reduction and the formation of secondary sulfides this explains the removal of salts alkali carbonates and sulfates as well as the minor olivine serpentinization 3 hydrothermal sulfur was added to the kimberlitic breccia but not to the massive kimberlites in situ measurements of sulfides confirm this scenario clearly showing the addition of two sulfide populations in the breccia pyrite pyrrhotites with average 34s of 7 9 3 4 and chalcopyrites with average 34s of 38 0 0 4 whereas the salty and non salty kimberlites preserve a unique population of djerfisherites cl and k rich sulfides with 34s values within the mantle range this study provides the first direct evidence of alkaline igneous rocks in which magmatic sulfate is more abundant than sulfide although sulfates have been rarely reported in mantle materials sulfate rich melts may be more common in the mantle than previously thought and could balance the sulfur isotope budget of earth s mantle

bubble collapse as the source of tremor at old faithful geyser old faithful geyser yellowstone was used as a natural laboratory for fluid flow induced seismic activity pressure measurements within the geyser s water column obtained simultaneously with seismic measurements on the surface demonstrated that the tremor observed at old faithful results from impulsive events in the geyser tremor intensity is controlled by the rate of occurrence of these impulsive events there is no resonance observed within the water column the impulsive events are modeled by a collapse of a spherical bubble including the effects of residual non condensible gas and damping the pressure data can be explained by a collapse of a 5 cm radius bubble driven by a pressure difference of p 0 3 10 5 pa and effective viscosity e 0 04 m 2 s using a quasi static geyser model we treat the individual bubble collapses as cooling events that occur when the water column reaches a critical temperature their rate of occurrence is controlled by the heating rate dt dt of the water column as a result the intensity of the hydrothermal and seismic activities is determined by the heat and mass input rate into the geyser it is demonstrated that a sharp widening of the conduit can cause the number of events per unit time to drop as observed while the water level is still rising and heat is being input and thus the tremor intensity can be modulated by variations in the conduit shape

eruptions at lone star geyser yellowstone national park usa 1 energetics and eruption dynamics 1 geysers provide a natural laboratory to study multiphase eruptive processes we present results from a 4 day experiment at lone star geyser in yellowstone national park usa we simultaneously measured water discharge acoustic emissions infrared intensity and visible and infrared video to quantify the energetics and dynamics of eruptions occurring approximately every 3 h we define four phases in the eruption cycle 1 a 28 3 min phase with liquid and steam fountaining with maximum jet velocities of 16 28 m s 1 steam mass fraction of less than 0 01 intermittently choked flow and flow oscillations with periods increasing from 20 to 40 s are coincident with a decrease in jet velocity and an increase of steam fraction 2 a 26 8 min posteruption relaxation phase with no discharge from the vent infrared ir and acoustic power oscillations gliding between 30 and 40 s 3 a 59 13 min recharge period during which the geyser is quiescent and progressively refills and 4 a 69 14 min preplay period characterized by a series of 5 10 min long pulses of steam small volumes of liquid water discharge and 50

in situ observations of old faithful geyser in a series of experiments from 1983 to 1993 four probes were carefully lowered into old faithful geyser yellowstone national park wyoming at different times these probes variously recorded pressure temperature time conditions to nearly 22 m depth and video probes showed the conduit geometry and processes of recharge to 13 m depth temperatures recorded were within experimental error the same as those recorded in 1942 with a peak bottom temperature t of 118 c processes observed include fog formation in the upper levels of the conduit owing to wind and entrainment of cool air bank storage of hot water that splashes to high levels cools and recharges recharge of cooler ground water into the conduit superheated steam expansion into the conduit t 129 5 c periodic temperature fluctuations and exsolution of bubbles of noncondensable gas which we propose are co 2

dynamics within geyser conduits and sensitivity to environmental perturbations insights from a periodic geyser in the el tatio geyser field atacama desert chile abstract despite more than 200 years of scientific study the internal dynamics of geyser systems remain poorly characterized as a consequence there remain fundamental questions about what processes initiate and terminate eruptions and where eruptions begin over a one week period in october 2012 we collected down hole measurements of pressure and temperature in the conduit of an exceptionally regular geyser 132 s cycle located in the chilean desert we identified four stages in the geyser cycle 1 recharge of water into the conduit after an eruption driven by the pressure difference between water in the conduit and in a deeper reservoir 2 a pre eruptive stage that follows the recharge and is dominated by addition of steam from below 3 the eruption which occurs by rapid boiling of a large mass of water at the top of the water column and decompression that propagates boiling conditions downward and 4 a relaxation stage during which pressure and temperature decrease until conditions preceding the recharge stage are restored eruptions are triggered by the episodic addition of steam coming from depth suggesting that the dynamics of the eruptions are dominated by geometrical and thermodynamic complexities in the conduit and reservoir further evidence favoring the dominance of internal processes in controlling periodicity is also provided by the absence of responses of the geyser to environmental perturbations air pressure temperature and probably also earth tides

the origin of harmonic tremor at old faithful geyser volcanic tremor the seismic signal which is often associated with eruptions is among the least understood phenomena in seismology large variations in the physical properties of volcanic rocks and fluids along with the complex geological structure make it difficult to obtain reliable source models old faithful geyser yellowstone national park was chosen as a laboratory for studying fluid flow induced seismicity the geyser s cyclic behavior on an hourly time scale and its accessibility make it suitable for a detailed study of seismic behavior between eruptions simultaneously with underwater pressure measurements inside the geyser we observe that sharp pressure pulses inside the water column attributed to steam bubble collapse are followed by distinct seismic events with a sharp onset and a harmonic horizontal motion whose frequency varies spatially but not temporally a superposition of these events creates the appearance of continuous harmonic tremor since the pressure in the water column exhibits no sign of resonance the harmonic motion must be caused by elastic waves reverberating in the solid medium a near surface soft layer is demonstrated to be a possible elastic model the harmonic tremor observed at old faithful seems analogous to some examples of shallow volcanic tremor

gravity constraints on the deep structure of the pyrenean belt along the ecors profile abstract in order to furnish further constraints to modelling the ecors pyrenees deep seismic profile gravity data were collected along a stripe 20 km wide and 220 km long containing the seismic line a total of 4020 stations have been used to derive a bouguer anomaly map of the area a large and roughly symmetrical negative anomaly 100 mgal is centered on the axial zone a local positive anomaly over the north pyrenean zone disturbs the negative regional trend somewhat detailed densities were assigned to the sedimentary cover on the basis of borehole samples refraction data and a velocity density relationship were used to constrain the densities adopted for the deeper layers the results of the two dimensional gravity modelling confirm the asymmetrical shape of the crust mantle boundary beneath the pyrenean belt the downward deflection of the iberian moho from the ebro basin leads to a maximum depth of 65 km under the paleozoic axial zone whereas a depth of 35 km is found for the european moho under the north pyrenean zone two extreme models are proposed for the northern limit of the iberian crust a vertical contact in the downward continuity of the north pyrenean fault or a 70 northward sloping interface the positive anomalies beneath the north pyrenean zone may be explained by dense intracrustal mantle slices or lower crustal sheets the outcrop of granulitic basic gneiss within the labourd massif suggests that the anomaly results from lower crustal sheets

mushy magma beneath yellowstone a recent prospective on the yellowstone caldera discounts its explosive potential based on inferences from tomographic studies which suggests a high degree of crystallization of the underlying magma body in this study we show that many of the first teleseismic p wave arrivals observed at seismic stations on the edge of the caldera did not travel through the magma body but have taken longer but faster paths around the edge after applying a number of waveform modeling tools we obtain much lower seismic velocities than previous studies 2 3 km sec v p and 1 1 km sec v s we estimate the physical state of the magma body by assuming a fluid saturated porous material consisting of granite and a mixture of rhyolite melt and water and co 2 at a temperature of 800 c and pressure at 5 km 0 1 gpa we found that this relatively shallow magma body has a volume of over 4 300 km 3 and is about 32 melt saturated with about 8 water plus co 2 by volume

a model for internal oscillations in geysers with application to old faithful yellowstone usa abstract we present a mechanical model for internal oscillations in geysers with bubble trap configurations where ascending gas or vapor becomes trapped beneath the roof of a cavity that is laterally offset from the eruption conduit we consider two cases one in which the trapped gas behaves as an isothermal ideal gas and one where it is treated as isenthalpic steam in both cases the system behaves as a damped harmonic oscillator with a resonant frequency that is sensitive to the conduit geometries and fluid volumes we use the model to predict internal oscillation frequencies for old faithful geyser in yellowstone usa using conduit geometry constraints from the literature and find that the frequencies predicted by the model are consistent with observations 1 hz we show that systematic frequency increases during the recharge cycle when the fluid volume of the system is increasing due to recharge are consistent with either a decrease in the amount both volume and mass of trapped gas or vapor a decrease in the eruption conduit area or a combination of both

high resolution 3d shallow crustal structure in long beach california application of ambient noise tomography on a dense seismic array ambient noise tomography has proven to be effective in resolving shallow earth structure we applied ambient noise tomography on a dense seismic array in long beach california the array was composed of more than 5200 stations with an average spacing close to 100 m three weeks of passive ambient noise were crosscorrelated between each station pair which resulted in more than 13 5 million crosscorrelations within the area clear fundamental mode rayleigh waves were observed between 0 5 and 4 hz which were most sensitive to structure above 1 km depth for each station pair we applied frequency time analysis to determine the phase traveltime dispersion and for each frequency we applied eikonal tomography to determine the rayleigh wave phase velocity map the eikonal tomography accounted for ray bending by tracking the wavefront and allowed uncertainties to be estimated through statistical analysis the compilation of phase velocity maps was then used to invert for 3d shear velocity structure the inverted model showed clear correlation with the known geologic features such as the shallow south north velocity dichotomy and a deeper fast anomaly associated with the newport inglewood fault zone our results can potentially be used to complement traditional active source studies

editorial the role of intraplate magmas and their inclusions in earth s mantle evolution excerpt the differentiation of our planet into distinct geochemical reservoirs and the attendant heterogeneous distribution of the chemical components provides a challenge in constraining the composition of the earth with this challenge comes opportunity because the diverse probes of earth s interior yield critical insights into the dynamic processes that shape the planet

illuminating the voluminous subsurface structures of old faithful geyser yellowstone national park old faithful geyser in yellowstone national park has attracted scientific research for almost a century and a half temperature and pressure measurements and video recordings in the geyser s conduit led to proposals of many quantitative eruption models nevertheless information on the processes that initiate the geyser s eruption in the subsurface remained limited two new studies specifically wu et al 2017 and ward and lin 2017 take advantage of recent developments in seismic data acquisition technology and processing methods to illuminate subsurface structures using a dense array of three component nodal geophones these studies delineate subsurface structures on a scale larger than previously realized which exert control on the spectacular eruptions of old faithful geyser

geophysical constraints on the deep structure along the ecors pyrenees line the structure of the central part of the pyrenean range traversed by the ecors vertical reflection seismic line is further constrained by a joint interpretation of complementary and reprocessed data wide angle low frequency profiling of moho topography indicates an abrupt termination of the northern european moho at the north pyrenean fault and a range of possible geometries of a deeper iberian moho which does not seem to extend significantly to the north of this fault when reprocessing vertical reflection data to 25 s two way travel time strong clear straight reflections are discovered in the part of the section under the northern foreland long after the moho reflection their strong northward dip indicates that they originate in fact at reflectors at depth beneath the north pyrenean fault which may correspond to the connection between the two levels of moho the reflections then being from the northward inclined limit between the wedge of iberian crust underlying the southern edge of the european mantle a range of possible shapes is allowed by the conjunction of these seismic data which is compatible with the results of a detailed gravity profile this would indicate that the imbrication of european into iberian lithosphere has been of limited extent with respect to the surface trace of the north pyrenean fault provided no strong density contrast in the mantle part of the section contributes significantly to the gravity anomaly

3 d crustal structure of the western united states application of rayleigh wave ellipticity extracted from noise cross correlations we present a new 3 d seismic model of the western united states crust derived from a joint inversion of rayleigh wave phase velocity and ellipticity measurements using periods from 8 to 100 s improved constraints on upper crustal structure result from use of short period rayleigh wave ellipticity or rayleigh wave h v horizontal to vertical amplitude ratios measurements determined using multicomponent ambient noise cross correlations to retain the amplitude ratio information between vertical and horizontal components for each station we perform daily noise pre processing temporal normalization and spectrum whitening simultaneously for all three components for each station pair amplitude measurements between cross correlations of different components radial radial radial vertical vertical radial and vertical vertical are then used to determine the rayleigh wave h v ratios at the two station locations we use all earthscope usarray tranportable array data available between 2007 january and 2011 june to determine the rayleigh wave h v ratios and their uncertainties at all station locations and construct new rayleigh wave h v ratio maps in the western united states between periods of 8 and 24 s combined with previous longer period earthquake rayleigh wave h v ratio measurements and rayleigh wave phase velocity measurements from both ambient noise and earthquakes we invert for a new 3 d crustal and upper mantle model in the western united states correlation between the inverted model and known geological features at all depths suggests good resolution in five crustal layers use of short period rayleigh wave h v ratio measurements based on noise cross correlation enables resolution of distinct near surface features such as the columbia river basalt flows which overlie a thick sedimentary basin

the miaskitic to agpaitic transition in peralkaline nepheline syenite white foyaite from the pilanesberg complex south africa abstract the mesoproterozoic pilanesberg complex south africa is built up by several distinct ring shaped intrusions of syenite and peralkaline nepheline syenite a mildly peralkaline na k al 1 04 1 09 medium to coarse grained nepheline syenite makes up the outermost ring in the southwestern part of the complex matooster type white foyaite in this rock mafic silicate minerals amphibole biotite aegirine and ti bearing minerals ilmenite astrophyllite aenigmatite lorenzenite bafertisite jinshajiangite are interstitial to feldspar and nepheline and define a series of mineral assemblages reflecting a change from a miaskitic crystallization regime with na ca amphibole titanite and ilmenite to increasingly agpaitic conditions with arfvedsonite aegirine astrophyllite aenigmatite lorenzenite the main driving force behind the evolution was an increase in peralkalinity of the trapped liquid mainly by adcumulus growth of alkali feldspar and nepheline which in the later stages of evolution was combined with increases in oxygen fugacity and water activity unlike in most other agpaitic rock complexes zr remained compatible in aegirine and to some extent in amphibole almost to the end of the process when a hydrous zirconium silicate mineral hilairite crystallized as the only mineral in the rock having essential zirconium the presence of minerals such as hilairite bafertisite jinshajiangite and a na ree sr rich apatite group mineral fluorcaphite in the latest assemblages suggests that the last remaining interstitial melt or fluid approached a hyperagpaitic composition the isolated melt pockets in the pilanesberg white foyaite follow a pattern of evolution that can be seen as a miniature analogue of the fractional crystallization processes controlling magma evolution in large alkaline igneous rock complexes

geodynamics of the yellowstone hotspot and mantle plume seismic and gps imaging kinematics and mantle flow abstract integration of geophysical and geological data show that the yellowstone hotspot resulted from a mantle plume interacting with the overriding north america plate a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16 17 ma 700 km long yellowstone snake river plain ysrp silicic volcanic system accessibility of the ysrp allowed large scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements seismic tomography reveals a crustal magma reservoir of 8 to 15 melt 6 km to 16 km deep beneath the yellowstone caldera an upper mantle low p wave velocity body extends vertically from 80 km to 250 km beneath yellowstone but the anomalous body tilts 60 wnw and extends to 660 km depth into the mantle transition zone we interpret this conduit shaped low velocity body as a plume of up to 3 5 vp and 5 5 vs perturbation that corresponds to a 1 2 partial melt models of whole mantle convection reveal eastward upper mantle flow beneath yellowstone at relatively high rates of 5 cm yr that deflects the ascending plume into its west tilted geometry a geodynamic model of the yellowstone plume constrained by vp and vs velocities and attenuation parameters suggests low excess temperatures of up to 120 k corresponding to a maximum 2 5 melt and a small buoyancy flux of 0 25 mg s i e properties of a cool weak plume the buoyancy flux is many times smaller than for oceanic plumes nonetheless plume buoyancy has produced a 400 km wide 500 m high topographic swell centered on the yellowstone plateau contemporary deformation derived from gps measurements reveals sw extension of 2 3 mm yr across the yellowstone plateau one fourth of the total basin range opening rate which we consider to be part of basin range intraplate extension locally decadal episodes of subsidence and uplift averaging 2 cm yr characterize the 80 year yellowstone caldera monitored history and are modeled as hydrothermal magmatic sources moreover a recent episode 2004 2009 of accelerated uplift of the yellowstone caldera at rates up to 7 cm yr has been modeled as resulting from magmatic recharge of a 10 km deep sill at the top of the crustal magma reservoir regionally gravitational potential energy of the yellowstone swell drives the lithosphere southwest and downhill from the yellowstone plateau 400 km where it coalesces with basin range province wide westward extension based on the geometry and its assumed 660 km depth we extrapolate the plume source southwest to its original location at 17 ma and 600 km southwest and 200 km north of the ysrp importantly this location is beneath the southern part of the columbia plateau flood basalt field of the same age and implies that the yellowstone mantle plume may be the common source for both of these large volcanic fields our time progression model suggests that the original plume head rose vertically behind the juan de fuca plate but at 12 ma it lost the protection of the subducting plate from eastward mantle flow and encountered cooler thicker continental lithosphere becoming entrained in eastward upper mantle flow these results reveal that yellowstone plume plate processes have had a profound effect on late cenozoic geologic evolution and topography of a large part of the western u s

implications of the seismic structure for the orogenic evolution of the pyrenean range abstract the dynamic evolution of the pyrenees is discussed in the light of geophysical data recent deep seismic sounding have revealed the crustal structure of the pyrenees which is used to test the different evolutionary models proposed until now the crustal thickness of the paleozoic axial zone paz and the north pyrenean zone npz differ by more than 10 km ranging from about 30 km in the npz to 40 50 km in the paz the transition from paz to the npz identified at the surface as the north pyrenean fault npf is sharp at depth and marked by a vertical step at least in the eastern half of the range the npz is characterized by additional throws and dips of the moho in the east whereas in the west a heterogeneous middle to lower crust is encountered with high velocity anomalies the seismic results suggest that the paz and the npz belong to different plates the npf being the plate boundary these results are inconsistent with evolutionary models involving lithospheric subduction or crustal doubling and intracratonic rifting with the main tectonic lineations following nne ssw directions they rather suggest that after a period of extension two main orogenic events took place a phase involving shearing and thinning which affected mainly the present day npz and a later compressive phase which explains the building up of the chain the thickening of the crust and the enhancement of a pre existing difference in crustal thickness between the european and iberian plates

the plumbing of old faithful geyser revealed by hydrothermal tremor 1 old faithful geyser in yellowstone national park usa has attracted numerous scientific investigations for over two centuries to better understand its geological structure the physics of its eruptions and the controls of its intermittency using data acquired with a seismic array in 1992 we track the sources of hydrothermal tremor produced by boiling and cavitation inside the geyser the location of seismic sources identifies a previously unknown lateral cavity at 15 m below the surface on the sw side of the vent and connected to the conduit this reservoir is activated at the beginning of each geyser eruption cycle and plays a major role in the oscillatory behavior of the water level in the conduit before each eruption

the fascinating and complex dynamics of geyser eruptions geysers episodically erupt liquid and vapor despite two centuries of scientific study basic questions persist why do geysers exist what determines eruption intervals durations and heights what initiates eruptions through monitoring eruption intervals analyzing geophysical data taking measurements within geyser conduits performing numerical simulations and constructing laboratory models some of these questions have been addressed geysers are uncommon because they require a combination of abundant water recharge magmatism and rhyolite flows to supply heat and silica and large fractures and cavities overlain by low permeability materials to trap rising multiphase and multicomponent fluids eruptions are driven by the conversion of thermal to kinetic energy during decompression larger and deeper cavities permit larger eruptions and promote regularity by isolating water from weather variations the ejection velocity may be limited by the speed of sound of the liquid vapor mixture

petrographic and melt inclusion constraints on the petrogenesis of a magmaclast from the venetia kimberlite cluster south africa abstract kimberlitic magmaclasts are discrete ovoid magmatic fragments that formed prior to emplacement from disrupted kimberlite magma to provide new constraints on the origin and evolution of the kimberlite melts we document the mineralogy and petrography of a magmaclast recovered from one of the ca 520 ma venetia kimberlites south africa the sample bi9883 has a sub spherical shape and consists of a 10 mm diameter central olivine macrocryst surrounded by porphyritic kimberlite the kimberlitic material consists of concentrically aligned altered olivine phenocrysts set in a crystalline groundmass of calcite chromite perovskite phlogopite apatite ilmenite titanite sulphides rutile and magnetite along with abundant alteration phases i e serpentine talc and secondary calcite these features are typical of archetypal hypabyssal kimberlites we examined primary fluid melt inclusions in chromite perovskite and apatite containing a diversity of daughter phases chromite and perovskite host polycrystalline inclusions containing abundant alkali carbonates i e enriched in k na ba sr phosphates na k chlorides sulphides and equal to lesser quantities of olivine phlogopite and pleonaste in contrast apatite hosts polycrystalline assemblages with abundant alkali carbonates and na k chlorides and lesser amounts of olivine monticellite and phlogopite numerous solid inclusions of shortite na 2 ca 2 co 3 3 na sr carbonates and apatite occur in groundmass calcite along with fluid inclusions containing daughter crystals of na carbonates and na chlorides the primary inclusions in chromite perovskite and apatite are considered to represent remnants of fluid s melt s trapped during crystallisation of the host minerals whereas the fluid inclusions in calcite are probably secondary in origin the component proportions of these primary fluid melt inclusions were estimated in an effort to constrain the composition of the evolving kimberlite melt these estimates suggest melt evolution from a silicate carbonate kimberlite melt that became increasingly enriched in carbonates phosphates alkalis and chlorides in response to the fractional crystallisation of constituent minerals i e olivine to apatite the concentric alignment of crystals around the olivine kernel and ovoid shape of the magmaclast can be ascribed to the low viscosity of the kimberlite melt and rapid rotation whilst in a liquid or partial crystalline state or to progressive layer by layer growth of the magmaclast although the mineralogy of our sample is similar to hypabyssal kimberlites worldwide it differs from hypabyssal kimberlite units in the main venetia pipes which contain monticellite phlogopite rich assemblages and segregationary matrix textures therefore magmaclast bi9883 probably originated from a batch of magma distinct from those that produced known hypabyssal units within the venetia kimberlite cluster

seismic profiling the continental lithosphere deep seismic reflection profiling is successfully being used worldwide to study the structure of the continental crust1 7 the moist8 profile recorded by birps british institutions reflection profiling syndicate was the first to show that the structure of the upper mantle could also be imaged given a powerful source and long recording times birps has recently acquired an ultra deep seismic reflection line drum deep reflections from the upper mantle the drum line was designed specifically to investigate the reflectivity of the lower continental lithosphere and was therefore recorded to a two way time twt of 30 s giving a depth of penetration into the lithosphere of 110 km this profile has now revealed strong reflections which are unequivocally from the lower lithosphere well below the base of the crust and which are as far as we are aware the deepest and most continuous structures imaged in the upper mantle by multi channel seismic reflection profiling

constraints on crustal structure and complex moho topography beneath pinon flat california from teleseismic receiver functions abstract we use teleseismic p waves recorded at pinon flat observatory pfo to constrain the three dimensional crustal and upper mantle velocity structure beneath the station by forward modeling radial receiver function waveforms we construct a one dimensional crustal model that includes a significant shear velocity inversion at 9 km in depth arrivals on the tangential components indicate dip of at least the uppermost discontinuity complicated moho topography deepening to the northwest of pfo is suggested by azimuthal dependence of travel times and amplitudes of the receiver functions and travel times of crustal p wave reverberations although fine details cannot be resolved each of those sets of observations plus mislocation vectors provide strong indications of abrupt moho topography possibly including step offsets of several kilometers this is not only consistent with gravity data in implying airy isostasy with compensation at moho depth but extends that model to a much finer length scale than had been resolved

anatomy of old faithful from subsurface seismic imaging of the yellowstone upper geyser basin the upper geyser basin in yellowstone national park contains one of the highest concentrations of hydrothermal features on earth including the iconic old faithful geyser although this system has been the focus of many geological geochemical and geophysical studies for decades the shallow 200 m subsurface structure remains poorly characterized to investigate the detailed subsurface geologic structure including the hydrothermal plumbing of the upper geyser basin we deployed an array of densely spaced three component nodal seismographs in november of 2015 in this study we extract rayleigh wave seismic signals between 1 10 hz utilizing non diffusive seismic waves excited by nearby active hydrothermal features with the following results 1 imaging the shallow subsurface structure by utilizing stationary hydrothermal activity as a seismic source 2 characterizing how local geologic conditions control the formation and location of the old faithful hydrothermal system and 3 resolving a relatively shallow 10 60 m and large reservoir located 100 m southwest of old faithful geyser

mineralogy of the tk1 and tk4 kimberlites in the timmasamudram cluster wajrakarur kimberlite field india implications for lamproite magmatism in a field of kimberlites and ultramafic lamprophyres abstract a mineralogical study of the hypabyssal facies late cretaceous macrocrystic pulse of tk1 intrusion and the mesoproterozoic aphanitic pulse of tk4 intrusion in the wajrakarur kimberlite field of southern india shows that the rocks contain macrocrysts of forsteritic olivine phenocrysts and microphenocrysts of al na poor diopside and phlogopite set in a groundmass mainly of al na poor diopside and phlogopite other groundmass minerals are spinel perovskite and fluorapatite in tk1 and spinel titanite chlorite calcite and gittinsite in tk4 k richterite and perovskite occur only as inclusions in phlogopite and titanite respectively in tk4 late stage deuteric phases include pyrite and barite in tk1 and strontianite chalcopyrite galena and pentlandite in tk4 diopside microphenocrysts in tk4 exhibit oscillatory zoning with characteristics of diffusion controlled magmatic growth tk1 spinels show magmatic trend 2 that evolves from magnesiochromite and culminates in titaniferous magnetite whereas tk4 spinels are less evolved with magnesiochromite composition only tk1 phlogopites show a simple compositional trend that is typical of lamproite micas while four distinct growth zones are observed in tk4 phlogopites with the following compositional characteristics zone i high cr 2 o 3 and tio 2 and low bao zone ii low cr 2 o 3 zone iii low tio 2 and high bao zone iv low bao forsterite contents and trace element concentrations reveal two xenocrystic core populations and one magmatic rim population for tk1 olivines mineralogically both tk1 and tk4 are classified as diopside phlogopite lamproites rather than archetypal kimberlites the two lamproites are considered to have formed from the same parent magma but crystallised under distinct oxygen fugacity conditions with elevated content of fe 3 in phlogopite spinel and perovskite tk1 appears to have crystallised in a relatively high oxygen fugacity environment multiple growth generations of phlogopite spinel and fluorapatite in tk4 indicate a complex evolutionary history of the magma close spatial and temporal associations of mesoproterozoic kimberlites and lamproites in southern india can possibly be explained by a unifying model which accounts for the generation of diverse magmas from a range of geochemical resevoirs in a continental rift setting

melting and dynamic metasomatism of mixed harzburgite glimmerite mantle source implications for the genesis of orogenic potassic magmas abstract tectonically young orogenic settings are commonly the sites of post collisional silica rich ultrapotassic magmas with extreme k2o contents of up to 9 wt and k2o na2o 2 many experimental studies investigating the generation of these melts have concentrated on melting of homogenous phlogopite bearing peridotites whereas geochemical signatures indicate the involvement of at least two types of source rocks ultra depleted and k and trace elements enriched ones we report the results of melting experiments at 1 2 gpa of mixed glimmerite and harzburgite in which these rock types make up two halves each capsule melting begins in the glimmerite and its metasomatic effects on the harzburgite are apparent at 1100 c even before melt pools are visible the first melts are na rich seen in zoning of olivines and as growth of clinopyroxene in the harzburgite but change at higher degrees of melting to produce a typical lamproite like melt with k2o 10 wt a major advantage of this study is the preservation of distinct melts in different parts of the capsule which reflect a process of dynamic metasomatism within the harzburgite matrix the infiltrating melt derived from melting of the glimmerite changes consistently with the distance of travel through the harzburgite enabling quantification of the metasomatic effects as an increase in sio2 and k2o this results principally from assimilation of orthopyroxene which increases the ol opx ratio of the residual harzburgite the effects of quench olivine growth are recognizable and can be quantified due to a step change in composition at the glimmerite harzburgite border the large total surface area of olivine and small melt fraction mean that the amount of quench olivine is high within the harzburgite but negligible in the almost completely molten glimmerite melts of the glimmerite contain up to 8 10 wt k2o and 53 wt sio2 which increase to 55 56 wt after interaction with the harzburgite mediterranean lamproites resemble melts of glimmerite whereas melts that have interacted with harzburgite are more similar to less potassic but more sio2 rich shoshonites of the mediterranean region

underwater and drone based photogrammetry reveals structural control at geysir geothermal field in iceland abstract geysers are local hydrothermal vents with periodic gas bubble driven explosions at the surface little is known however on the control on distribution the dynamics and the geometry of the conduits of geysers to better understand the link between the deep and surface expression at the geysir geothermal field iceland a detailed analysis of the spatial distribution of the thermal expressions and their relationship to the tectonic framework was carried out by use of high resolution unmanned aerial vehicle uav based optical and radiometric infrared cameras we are able to identify 364 distinct thermal spots distributed over the area close analysis of their arrangement yields a clustered appearance following a preferred direction that is found to be consistent with the assumed tectonic trend in the area furthermore by using underwater cameras we are able to obtain for the first time detailed images from the two largest geysers at depths exceeding 20 m near to the surface the conduit of the geysers are near circular but at a depth of 9 12 m the shape changes into a crack like elongated fissure the elongation direction of these deep cracks is consistent with the identified thermal expression at the surface highlighting a structural or even tectonic control at the geysir geothermal field which may also explain the susceptibility for seismically triggered activity changes

the whisper of the hydrothermal seismic noise at ischia island abstract this work is devoted to the study of the background seismic noise at ischia island we highlight two persistent independent signals with dominant frequency peaks in the range 1 2 hz and 3 4 hz respectively the first signal is the most energetic and persistent and its polarization properties are well defined revealing a shallow propagation likely controlled by both tectonic volcanic structures and morphological features this signal is well correlated at all the stations in the casamicciola area and its group velocity is estimated as 500 600 m s the second signal shows similar polarization properties but the temporal pattern of its amplitude is strongly affected by anthropogenic noise revealing a modulation on a diurnal scale on the investigated spatial scales any clearly correlated signal is not evidenced we interpret the 1 2 hz correlated wave packets as the persistent whisper of the shallow circulation of fluids which are a mixing of sea and meteoric water and thermal fluids of the hydrothermal reservoir in the conceptual scheme of the self sustained musical instruments we hypothesize that the solid structure of the shallow hydrothermal system of ischia is formed by a network of channels continuously excited by the circulating hydrothermal fluids which produce a whispered sound i e the seismic noise this mechanism is able to produce persistent self sustained oscillations that we observe as the 1 2 hz seismic signal and eventually higher modes

the ecors deep reflection seismic survey across the pyrenees the pyrenees are an alpine age mountain belt located on the boundary between the iberian and european plates using the same geological and geophysical data earth scientists studying the structure of the pyrenees during the past ten years have not reached a consensus here we report the first results from a nearly continuous 255 km long reflection seismic survey across the pyrenean chain this first deep reflection profile of an entire erogenic belt will help to constrain possible models for the structure and formation of the pyrenean chain

seismicity at old faithful geyser an isolated source of geothermal noise and possible analogue of volcanic seismicity abstract old faithful geyser in yellowstone national park u s a is a relatively isolated source of seismic noise and exhibits seismic behavior similar to that observed at many volcanoes including bubblequakes that resemble b type earthquakes harmonic tremor before and during eruptions and periods of seismic quiet prior to eruptions although old faithful differs from volcanoes in that the conduit is continuously open that rock fracturing is not a process responsible for seismicity and that the erupting fluid is inviscid h2o rather than viscous magma there are also remarkable similarities in the problems of heat and mass recharge to the system in the eruption dynamics and in the seismicity water rises irregularly into the immediate reservoir of old faithful as recharge occurs a fact that suggests that there are two enlarged storage regions one between 18 and 22 m the base of the immediate reservoir and one between about 10 and 12 m depth transport of heat from hot water or steam entering at the base of the recharging water column into cooler overlying water occurs by migration of steam bubbles upward and their collapse in the cooler water and by episodes of convective overturn an eruption occurs when the temperature of the near surface water exceeds the boiling point if the entire water column is sufficiently close to the boiling curve that the propagation of pressure release waves rarefactions down the column can bring the liquid water onto the boiling curve the process of conversion of the liquid water in the conduit at the onset of an eruption into a two phase liquid vapor mixture takes on the order of 30 s the seismicity is directly related to the sequence of filling and heating during the recharge cycle and to the fluid mechanics of the eruption short 0 2 0 3 s monochromatic high frequency events 20 60 hz resembling unsustained harmonic tremor and in some instances b type volcanic earthquakes occur when exploding or imploding bubbles of steam cause transient vibrations of the fluid column the frequency of the events is determined by the length of the water column and the speed of sound of the fluid in the conduit when these events occur damping is controlled by the characteristic and hydraulic impedances which depend on the above parameters as well as on the recharge rate of the fluid two periods of reduced seismicity of a few tens of seconds to nearly a minute in duration occur during the recharge cycle apparently when the water rises rapidly through the narrow regions of the conduit causing a sudden pressure increase that temporarily suppresses steam bubble formation a period of decreased seismicity also precedes preplay or an eruption this appears to be the time when rising steam bubbles move into a zone of boiling that is acoustically decoupled from the wall of the conduit because of the acoustic impedance mismatch between boiling water c 10 3 g cm 2 s 1 and rock c 3 10 5 g cm 2 s 1 sustained harmonic tremor occurs during the first one to one and a half minutes of an eruption of old faithful but is not detectable in the succeeding minutes of the eruption the eruption tremor is caused by hydraulic transients propagating within a sublayer of unvesiculated water that underlies the erupting two phase liquid vapor mixture the resonant frequencies of the fluid column decrease to about 1 hz when all of the water in the conduit has been converted to a water steam mixture surges are observed in the flow at this frequency but the resonance has not been detected seismically possibly because the two phase erupting fluid is seismically decoupled from the rock on which seismometers are placed if old faithful is an analogue for volcanic seismicity this study shows that because the frequency of tremor depends on the acoustic properties of the fluid and on conduit dimensions both properties must be considered in analysis of tremor in volcanic regions because magma sound speed can vary over nearly two orders of magnitude as it changes from an undersaturated liquid into a saturated two phase mixture tremor frequency might vary by this magnitude and very broad band seismographs may be required if tremor is to be monitored as magma goes from an undersaturated liquid to a vesiculated froth cessation of fluid induced seismicity may indicate that the processes that drive the transients cease but it is also possible that the processes that drive the transients continue but the fluid properties change so that the fluid becomes acoustically decoupled from the rock on which seismometers are placed