crustal xenoliths in recent hawaiites from mount etna italy evidence for alkali exchanges during magma wall rock interaction abstract detailed mineralogical and geochemical systematics were carried out on crustal xenoliths the host hawaiite lavas erupted from mount etna sicily italy in 1892 1986 and 1989 as well as the flyschs from the volcano basement the xenoliths suffered morphological structural mineralogical and geochemical alteration induced by thermal and chemical exchange with the enclosing lava high temperature reactions and partial or complete melting as well as different mechanisms of elemental interdiffusion took place their exact nature depending on the type of xenolith an early and strong mobility of k rb and cs and their selective migration towards the anatectic melts the lava envelope was observed at both mineral phase and whole rock scales this is closely connected to a release of h 2 o cl s and co 2 associated with the dehydration and the decarbonation of the sediments thus the selective migration of the k rb and cs towards the enclosing lava as well as contamination of the host lava observed seems to be induced by a selective diffusion of alkalis away from the anatectic melts and especially by their selective transfer through the action of complex interstitial and chemically active fluids such processes might be connected to the strong enrichment in k rb and cs of the recent hawaiites from mount etna they might also substantiate the hypothesis that these enrichments result from selective contamination of the magma as a consequence of the percolation or circulation of a carrier fluid phase through the upper parts of the magmatic feeding system

medium term anomalies in groundwater temperature before 1991 1993 mt etna eruption abstract in 1991 a hydrogeochemical surveillance program was set up on mount etna involving periodic measurement of several chemico physical parameters in springs and wells along the eastern and southwestern flanks of the volcano significant increases in the temperature of these waters were observed some months before the 1991 1993 eruption the energy responsable for this heat anomaly represents less than 0 3 of the total thermal energy released by the following eruption the contribution from thermal conductivity of the rocks is negligible the ascent of the gases released from the magma determined the transfer of energy from the magma to the aquifers of etna the energy that produced the thermal anomaly in the groundwaters is one order of magnitude lesser than the minimum estimated energy transported by the gases released from the erupted magma continuous monitoring of groundwater temperatures and other parameters may not only predict eruptions in the future but also permit an estimate of the volume of magma involved

transmission to reflection transformation of teleseismic wavefields 1 in this paper we review the transformation of p and sv transmission green s functions into the corresponding reflection quantities for one dimensional elastic media at precritical slownesses to obtain estimates of the transmission green s functions from observed data we apply a recently developed approach that exploits the minimum phase nature of the direct waves and employs autospectra and cross spectra of raw component seismograms representing multiple sources recorded at a single station to accomplish transformation to reflection green s functions we outline a practical recipe that involves amplitude balancing energy normalization cross correlation and removal of free surface effects we assess its performance through application to both synthetic seismograms and data from station hyderabad in all cases we are able to identify the first order scattering contributions from the continental moho the transmission to reflection transformation has potential applications for imaging hitherto elusive shallow mantle discontinuities since interfering forward and back scattering contributions are effectively separated by component in the resulting reflection green s functions

new relationships between vs thickness of sediments and resonance frequency calculated by the h v ratio of seismic noise for the cologne area germany noise measurements were carried out in the cologne area germany and the resonance frequency of each site was estimated from the main peak in the spectral ratio between the horizontal and vertical component for 32 of these sites the thickness of the sedimentary cover was known from boreholes and a clear correlation between resonance frequency and sediment thickness was observed a formula that correlates cover thickness with frequency of the main peak in the horizontal to vertical spectral ratio was derived in addition a best fitting shear wave velocity distribution with depth vs z as well as a relationship between average shear wave velocity vs and thickness of the sedimentary cover was calculated by using all of the noise measurements and applying the derived relationships we obtained a subsoil classification for the cologne area

seismic interferometry of teleseicmic s wave coda for retrieval of body waves an application to the philippine sea slab underneath the japanese islands summary the reconstruction of surface waves from the cross correlation of random wavefields has recently been extensively inspected by theoretical and experimental approaches however the reconstruction of body waves has not been extensively studied in this study we present a method for extracting body waves that is direct p and s waves and reflected waves from the philippine sea slab we use the cross correlation of the wavefield generated by the teleseismic s waves observed by hi net tiltmeters with a passband of 0 07 0 5 hz to enhance the contribution of the s coda we reduced the source time function and the deterministic phases ss scs and ss and the surface wave in s coda the records of the processed s coda observed at every station pair are cross correlated for each teleseismic event the cross correlation functions ccfs of different earthquakes are stacked to retrieve wavefields propagating between the station pairs as a result direct p s and the reflected waves could be extracted when the stacked ccfs are aligned as a function of distance of separation between two stations the gradients of the traveltime curves for the direct p and s waves are approximately 5 7 and 3k m s 1 respectively these velocities correspond to the seismic velocities of the crust or the p wave velocity of the uppermost mantle in order to enhance the reflected waves we searched for the reflection points by assuming that the later phases in the ccfs are ss reflections and map the amplitudes onto the depth sections as a result the negative phases dipping to the north can be traced right below the region of hypocentre distribution these negative phases probably correspond to the oceanic moho within the philippine sea slab we also show that the oceanic moho can also be traced by assuming pp reflections these results indicate that the ccfs plausibly contain information regarding both p and s waves propagating between the two receivers and are capable of detecting reflected phases in addition to the direct waves

mobility of major minor and some redox sensitive trace elements and rare earth elements during weathering of four granitoids in central portugal abstract element mobility was studied in four different granitoids in central portugal samples of fresh and weathered rock parts were collected from each type of granitoid an increase in the degree of weathering is accompanied by reductions in na 2 o cao and sio 2 plagioclase p 2 o 5 apatite and in most cases also by reduction in k 2 o biotite potash feldspar losses as well as gains are observed for mgo relative changes in the al 2 o 3 contents are attributed to physical transport or accumulation of fine weathering products mass balance calculations indicate that kaolinite and in some cases also gibbsite are the dominant weathering products this is in agreement with x ray diffraction analyses manganese is found to decrease but not fe there is a high correlation between v and fe this is preserved during weathering there were both increases and decreases in the trace elements cr as and sb u had become slightly enriched in the weathered parts no systematic trends in ree behaviour were observed differences in the behaviour of these elements and in their ratios can be explained by a combination of factors such as differential dissolution of the host minerals redox conditions and redox kinetics complexation by organic and inorganic ligands and sorption the interpretation of the results is complicated by apparent inhomogeneities in the granites on the mesoscale of an outcrop

geochemical mapping of magmatic gas water rock interactions in the aquifer of mount etna volcano abstract systematic analysis of major and minor elements in groundwaters from springs and wells on the slopes of mt etna in 1995 1998 provides a detailed geochemical mapping of the aquifer of the volcano and of the interactions between magmatic gas water bodies and their host rocks strong spatial correlations between the largest anomalies in pco2 ph and alkalinity k rb mg ca and sr suggest a dominating control by magmatic gas co2 and consequent basalt leaching by acidified waters of the shallow meteoric etnean aquifer most groundwaters displaying this magmatic type interaction discharge within active faulted zones on the s sw and e lower flanks of the volcanic pile but also in a newly recognised area on the northern flank possibly tracking a main n s volcano tectonic structure in the same time the spatial distribution of t c tds na li cl and b allows us to identify the existence of a deeper thermal brine with high salinity high content of b cl and gases co2 h2s ch4 and low k na ratio which is likely hosted in the sedimentary basement this hot brine reaches the surface only at the periphery of the volcano near the village of paterno where it gives rise to mud volcanoes called salinelle di paterno however the contribution of similar brines to shallower groundwaters is also detected in other sectors to the w bronte maletto sw adrano and se acireale suggesting its possible widespread occurrence beneath etna this thermal brine is also closely associated with hydrocarbon fields all around the volcano and its rise generally masked by the high outflow of the shallow aquifer may be driven by the ascent of mixed sedimentary magmatic gases through the main faults cutting the sedimentary basement

chemical processes affecting the mobility of major minor and trace elements during weathering of granitic rocks abstract the behaviour of 38 major and trace elements as well as changes in the mineralogy have been examined in 10 weathering profiles developing on some portuguese granitic rocks element mobilities are calculated from geochemical data normalized with respect to ti in the fresh parent rock chemical elements are divided into two groups immobile and mobile on the basis of their geochemical distribution during weathering elements that are immobile during weathering are zr hf fe al th nb sc and the ree very mobile are ca na p k sr ba rb mg and si mobile elements are derived mainly from leachable minerals such as feldspars micas and apatites whereas immobile elements are either concentrated in resistate phases or strongly adsorbed by secondary minerals the geochemical behaviour of mn cr v fe and ce is very dependent on redox conditions redox transformations of these elements can be used to set limits on the oxidation state of a weathering suite the ree are mobilized or fractionated during late stages of weathering but not during moderate stages of weathering this fractionation is caused by selective leaching of rocks composed of both stable and unstable minerals containing ree

sulphur dioxide particle and elemental emissions from mount etna italy during july 1987 sulphur dioxide emission rates were measured at mount etna italy during july 1987 while the volcano was undergoing relatively quiet activity the so2 flux averaged 930 587 1 mg d excluding 19 july when the flux was 3200 1730 1 mg d rising magma and or an influx of less degassed magma could explain the increased so2 flux the high so2 flux did not correlate with changes in observed volcanic activity this suggests that so2 monitoring may be useful as an indicator of shallow magmatic activity but not as a predictor of future eruptions of mount etna

co2 output and δ13c co2 from mount etna as indicators of degassing of shallow asthenosphere an estimated average co2 output from etna s summit craters in the range of 13 3 mt a has recently been determined from the measured so2 output and measured co2 so2 molar ratios to this amount the co2 output emitted diffusely from the soil 1 mt a and the amount of co2 dissolved in etna s aquifers 0 25 mt a must be added data on the solubility of co2 in etnean magmas at high temperature and pressure allow the volume of magma involved in the release of such an amount of this gas to be estimated this volume of magma 0 7 km3 a is approximately 20 times greater than the volume of magma erupted annually during the period 1971 1995 on the basis of c isotopic data of co2 collected in the etna area and of new hypotheses on the source of mediterranean magmas significant contributions of co2 from non magmatic sources to the total output from etna are unlikely such large outputs of co2 and also of so2 from etna could be due to an anomalously shallow asthenosphere beneath the volcano that allows a continuous escape of gases toward the surface even without migration of magma

a shallow fault zone structure illuminated by trapped waves in the karadere duzce branch of the north anatolian fault western turkey summary we discuss the subsurface structure of the karadere duzce branch of the north anatolian fault based on analysis of a large seismic data set recorded by a local passcal network in the 6 months following the mw 7 4 1999 izmit earthquake seismograms observed at stations located in the immediate vicinity of the rupture zone show motion amplification and long period oscillations in both p and s wave trains that do not exist in nearby off fault stations examination of thousands of waveforms reveals that these characteristics are commonly generated by events that are well outside the fault zone the anomalous features in fault zone seismograms produced by events not necessarily in the fault may be referred to generally as fault zone related site effects the oscillatory shear wave trains after the direct s arrival in these seismograms are analysed as trapped waves propagating in a low velocity fault zone layer the time difference between the s arrival and trapped waves group does not grow systematically with increasing source receiver separation along the fault these observations imply that the trapping of seismic energy in the karadere duzce rupture zone is generated by a shallow fault zone layer traveltime analysis and synthetic waveform modelling indicate that the depth of the trapping structure is approximately 3 4 km the synthetic waveform modelling indicates further that the shallow trapping structure has effective waveguide properties consisting of thickness of the order of 100 m a velocity decrease relative to the surrounding rock of approximately 50 per cent and an s wave quality factor of 10 15 the results are supported by large 2 d and 3 d parameter space studies and are compatible with recent analyses of trapped waves in a number of other faults and rupture zones the inferred shallow trapping structure is likely to be a common structural element of fault zones and may correspond to the top part of a flower type structure the motion amplification associated with fault zone related site effects increases the seismic shaking hazard near fault zone structures the effect may be significant since the volume of sources capable of generating motion amplification in shallow trapping structures is large

crustal imaging across the north anatolian fault zone from the autocorrelation of ambient seismic noise seismic images of active fault zones can be used to examine the structure of faults throughout the crust and upper mantle and give clues as to whether the associated deformation occurs within a narrow shear zone or is broadly distributed through the lower crust limitations on seismic resolution within the crust and difficulties imaging shallow structures such as the crust mantle boundary moho place constraints on the interpretation of seismic images in this study we retrieve body wave reflections from autocorrelations of ambient seismic noise the instantaneous phase coherence autocorrelations allow unprecedented ambient noise images of the north anatolian fault zone nafz our reflection profiles show a moho reflected p wave and additional structure within the crust and upper mantle we image a distinct vertical offset of the moho associated with the northern branch of the nafz indicating that deformation related to the fault remains narrow in the upper mantle

mesoproterozoic chronostratigraphy of the southeastern llano uplift central texas the llano uplift of central texas exposes mesoproterozoic crystalline rocks affected by a grenvillian orogeny between 1 2 and 1 1 ga we report four new u pb zircon protolith ages of 1247 4 1257 3 1272 8 5 and 1366 3 ma for four quartzofeldspathic rocks from the regionally defined packsaddle schist and valley spring gneiss in the southeastern part of the uplift the 1366 3 ma gneiss also yields a metamorphic age of 1325 5 ma these new u pb ages in conjunction with previous u pb age data demonstrate that several regionally defined map units contain constituents with widely disparate ages we have identified four age suites for protoliths of metamorphic rocks in the southeastern part of the llano uplift that appear to represent rock packages of distinct tectonic origins 1 the northern 1366 1272 ma felsic gneisses of volcanic plutonic and continentally derived sedimentary origin valley spring gneiss and an older gneiss component 2 the geographically intermediate ca 1257 1247 ma and possibly older basinal sequence that formed along a continental shelf and slope near an arc packsaddle schist 3 the southern 1326 1275 ma remnant of an exotic ensimatic arc complex big branch gneiss and coal creek serpentinite and plutonic complex and 4 the 1239 1232 ma tectonized felsic rocks that intruded the first two suites the first three suites of rocks were structurally imbricated during grenville orogenesis and the fourth suite may either represent early synorogenic crustal melts or be related to the volcanic rocks in the packsaddle schist in addition these new data show that contrary to previous reports younger packsaddle schist lies in structural contact above older components of the valley spring gneiss moreover one of the dated meta igneous units is the oldest unit yet found in the uplift and records an early period of metamorphism prior to formation of most llano uplift rocks its 1366 3 ma protolith age is coeval with rocks of the western granite rhyolite terrane age and geochemical similarities link this unit of unknown regional extent with the western granite rhyolite terrane of known laurentian affinity thus this component of the llano uplift may be the basement on which the younger components of the valley spring gneiss and packsaddle schist formed in a tectonic setting proximal to laurentia and south of the western granite rhyolite terrane

mobility and fluxes of major minor and trace metals during basalt weathering and groundwater transport at mt etna volcano sicily abstract the concentrations and fluxes of major minor and trace metals were determined in 53 samples of groundwaters from around mt etna in order to evaluate the conditions and extent of alkali basalt weathering by waters enriched in magma derived co 2 and the contribution of aqueous transport to the overall metal discharge of the volcano we show that gaseous input of magmatic volatile metals into the etnean aquifer is small or negligible being limited by cooling of the rising fluids basalt leaching by weakly acidic co 2 charged water is the overwhelming source of metals and appears to be more extensive in two sectors of the s sw paterno and e zafferana volcano flanks where out flowing groundwaters are the richest in metals and bicarbonate of magmatic origin thermodynamic modeling of the results allows to evaluate the relative mobility and chemical speciation of various elements during their partitioning between solid and liquid phases through the weathering process the facts that rock forming minerals and groundmass dissolve at different rates and secondary minerals are formed are taken into account at mt etna poorly mobile elements al th fe are preferentially retained in the solid residue of weathering while alkalis alkaline earth and oxo anion forming elements as se sb mo are more mobile and released to the aqueous system transition metals display an intermediate behavior and are strongly dependent on either the redox conditions mn cr v or solid surface related processes v zn cu the fluxes of metals discharged by the volcanic aquifer of etna range from 7 0 10 3 t a th to 7 3 10 4 t a na they are comparable in magnitude to the summit crater plume emissions for a series of elements na k ca mg u v li with lithophile affinity but are minor for volatile elements basalt weathering at mt etna also consumes about 2 1 10 5 t a of magma derived carbon dioxide equivalent to ca 7 of contemporaneous crater plume emissions the considerable transport of some metals in etna s aquifer reflects a particularly high chemical erosion rate evaluated at 2 3 10 5 t a enhanced by the initial acidity of magmatic co 2 rich groundwater

retrieval of moho reflected shear wave arrivals from ambient seismic noise theoretical studies on ambient seismic noise asn predict that complete green s function between seismic stations can be retrieved from cross correlation however only fundamental mode surface waves emerge in most studies involving real data here we show that moho reflected body wave sms and its multiples can be identified with asn for station pairs near their critical distances in the short period band 1 5 s we also show that an uneven distribution of noise sources such as mining activity and wind topography interaction can cause surface wave precursors which mask weaker body wave phases

fault zone trapped seismic waves two instances of fault zone trapped seismic waves have been observed at an active normal fault in crystalline rock near oroville in northern california trapped waves were excited with a surface source and recorded at five near fault borehole depths with an oriented three component borehole seismic sonde at parkfield california a borehole seismometer at middle mountain recorded at least two instances of the fundamental and first higher mode seismic waves of the san andreas fault zone at oroville recorded particle motions indicate the presence of both love and rayleigh normal modes the love wave dispersion relation derived for an idealized wave guide with velocity structure determined by body wave travel time inversion yields seismograms of the fundamental mode that are consistent with the observed love wave amplitude and frequency applying a similar velocity model to the parkfield observations we obtain a good fit to the trapped wavefield amplitude frequency dispersion and mode time separation for an asymmetric san andreas fault zone structure a high velocity half space to the southwest a low velocity fault zone a transition zone containing the borehole seismometer and an intermediate velocity half space to the northeast in the parkfield borehole seismic data set the locations depth and offset normal to fault plane of natural seismic events which do or do not excite trapped waves are roughly consistent with our model of the low velocity zone we conclude that it is feasible to obtain near surface borehole records of fault zone trapped waves because trapped modes are excited only by events close to the fault zone proper thereby fixing these events in space relative to the fault a wider investigation of possible trapped mode waveforms recorded by a borehole seismic network could lead to a much refined body wave tomographic velocity model of the fault and to a weighting of events as a function of offset from the fault plane it is an open question whether near surface sensors exist in a stable enough seismic environment to use trapped modes as an earth monitoring device

dissolution of primary basaltic minerals in natural waters saturation state and kinetics abstract the state of saturation of olivine orthopyroxene and plagioclase of variable composition has been assessed in various types of natural waters in iceland including river waters groundwater and geothermal waters with temperatures up to 250 c the stability of olivine and orthopyroxene decreases with increasing mg content similarly the stability of plagioclase decreases with increasing anorthite content the river waters which are representative of the weathering environment are always undersaturated with both olivine and orthopyroxene the degree of undersaturation being dominated by the water ph all river waters tend to dissolve olivine of the composition encountered in basalts according to the linear rate law and orthopyroxene when the ph is 200 c are undersaturated with olivine orthopyroxene and plagioclase the first two particularly when fe rich and sufficient to cause olivine to dissolve according to the linear rate law at intermediate temperatures 50 150 c the geothermal waters are close to equilibrium with these minerals except for mg rich olivine it seems likely that dissolution of glass from basalt which is very reactive will favor stability of the igneous minerals

laser induced breakdown spectroscopy libs applied to terrestrial and extraterrestrial analogue geomaterials with emphasis to minerals and rocks thanks to its unique unprecedented and very appealing analytical capabilities and performances the laser induced breakdown spectroscopy libs technique has expanded rapidly in the last two decades in several fields of academic and applicative research including the study of geomaterials this review mainly consists of two parts the first one provides a general and brief summary and discussion of the basic theory and principles of libs the experimental set up of conventional laboratory bench top and portable remote and stand off configurations the main methodologies of qualitative and quantitative libs analysis with the support of chemometric approaches and the advantages and disadvantages of the technique the second part aims to provide a comprehensive detailed and adjourned at my best overview of the huge work done on libs applications to the study of geomaterials with focus on minerals and rocks in particular results obtained on element detection and quantification identification discrimination classification provenance weathering and alteration of minerals igneous sedimentary and metamorphic rocks gemstones mine ores archeological artifacts and speleothems are reviewed and briefly discussed the enormous efforts and remarkable progresses made in the last decade by several research groups on the potential and viable use of libs on robotic vehicles for studying meteorites and planetary analogue terrestrial rocks in simulated planetary conditions have also been reviewed

aseismic fault slip and block deformation in north china in north china the tectonic fault block system enables us to use the discontinuous deformation analysis dda method to simulate the long term cross fault survey and other geodetic data related to aseismic tectonic deformation by the simulation we have found that 1 slips on faults with different orientation are generally in agreement with the ene wsw tectonic stress field but the slip pattern of faulting can vary from nearly orthogonal to pure shear along the strike of the faults this pattern cannot be explained by simple geometric relation between the strike of the fault and the direction of the tectonic shortening this phenomenon has been observed at many sites of cross fault geodetic surveys and might be caused by the interactions between different blocks and faults 2 according to the dda model if the average aseismic slip rate along major active faults is at the order of several tenths of millimeter per year as observed by the cross fault geodetic surveys the typical strain rate inside a block is at the order of 10 8 year 1 or less so that the rate of 10 6 year 1 as reported by observations in smaller areas cannot be the representative deformation rate in this region 3 between the slips caused by regional compression and block rotation there is a possibility that the sense of slip caused by rigid body rotation in two adjacent blocks is opposite to the slip caused by the tectonic compression but the magnitude of slip resulting from the tectonic compression is much larger than that due to the block rotation thus in general the slip pattern on faults as a whole agrees with the sense of tectonic compression in this region that is to say the slip caused by regional compression dominates the entire slip budget 4 based on 3 some observed slips in contradiction to ene tectonic stress field may be caused by more localized sources and have no tectonic significance

the rare alkalies in hydrothermal alteration at wairakei and broadlands geothermal fields n z abstract drillcores and waters from wairakei and broadlands geothermal areas new zealand have been analyzed for li rb cs na k mg ca al ti mn and be the drillcores were altered to various degrees at temperatures below 300 c in slightly alkaline chloride water probably derived from rock water interaction in untapped horizons at higher temperature it changes its composition as it leaches ca and na from the rock and adds k rb cs and li evaluation of these changes in relation to the dimensions of the altered zone under observation suggests that a high mass ratio of water to rock e g 100 and a period of up to 1 million years are responsible for the present stage of alteration increase of k and rb in the altered rocks is a result of the formation of abundant adularia in addition to illite the k rb ratio of the rock decreases during alteration but remains higher than that of the fluid only clay materials and zeolites that preferentially absorb rb give slightly lower k rb ratios than the fluid the mineral phases responsible for the uptake of lithium during alteration are chlorite 300 ppm li and quartz up to 430 ppm li li uptake in quartz is considered to be the mechanism by which al rich quartz crystallises from alumino silicates li al atomic ratios of 0 3 0 57 and al concentrations up to 3000 ppm have been observed relatively small concentrations of cs are found in potassic minerals e g 10 ppm cs in adularia 44 ppm cs in illite however 240 ppm cs are found in wairakite from wairakei equilibrated at 235 c lower equilibration temperatures may lead to higher cesium concentrations this effect in conjunction with a more concentrated hydrothermal fluid could explain a content of 4500 ppm cs in wairakite extracted from a drillcore taken in the el tatio geothermal field in chile

analysis of rock samples collected from rock hewn churches of lalibela ethiopia using laser induced breakdown spectroscopy abstract with the aim to study alteration processes of the rock hewn churches from lalibela ethiopia we applied laser induced breakdown spectroscopy libs technique to measure the elemental composition both of the bulk rock materials and their external layers exposed to the environmental factors the analytical plasma was generated by nanosecond pulses of an nd yag laser emitting at 1064 nm different major and minor sample constituents were detected including ca mg na fe ti al and k the detected o emission originates both from air surrounding and the sample while the intensity of n lines coming exclusively from air was used for the libs signal normalization by depth profiling of the weathered basalt rock we observed a lower presence of k in the external layers corresponding to the first 5 laser shots the emission from this element is anti correlated with the line intensities from o and this was attributed to the variations in relative abundances of clay minerals and k feldspar the analogue measurements were performed on the tuff rock and compared to the spectra from powder samples containing only the external soft material scratched from the rocks these analyses show an abundance of h in the weathered wetted layers and suggest that cations are lost from the constituent primary minerals and replaced by h this process disrupts the lattice structure and causes a marked loss of strength the studies presented here demonstrate that libs is a useful technique for studying the alteration processes in the rocks caused by environmental factors

a global geochemical mass budget applied to the congo basin rivers erosion rates and continental crust composition rivers carry the products of continental denudation either in a dissolved form chemical erosion or in a solid form physical erosion we focus in this paper on the relationship between physical erosion and chemical erosion we establish the mass budget of the congo basin rivers using chemical complementarities between river suspended sediments sandy bedload and dissolved load of the congo basin rivers reported in a previous paper dupre et al 1995 a series of equations are presented assuming that the physical and chemical erosion processes are in a steady state during one year the total mass of river borne material dissolved and particulate transported in the river over a given period of time should balance the mass of upper continental crust eroded during this time we show that the local continental crust on each drainage basin can be estimated and solve our steady state weathering model using an inversion procedure the very good agreement between modelled and measured values of the river suspended sediment concentrations validates the steady state hypothesis in this wet tropical area consequently in this area the sediment yield provide a good estimate of the rates of mechanical denudation this result also validates the calculation of the chemical and isotopic composition of the local continental upper crust using the bulk river load erosion rates for the silicate upper crust and thus independent of the lithological variability silicates evaporites and carbonates of the drainage basins are calculated mechanical erosion rates and chemical erosion rates for the congo basin at brazzaville are 8 t km2 y and 5 t km2 y the corresponding consumption of atmospheric co2 by weathering process is estimated to 51 103 mol km2 an these weathering and consumption rates are low in spite of the severity of the weathering conditions of the high soil temperature and of the intensity of precipitations these conclusions indicate the limiting influence the dynamic equilibrium of soils for silicate weathering finally by estimating the local continental crust chemical composition before the onset of erosion processes especially for the most soluble elements we can test the model of taylor and mclennan

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

deep characterization of the santiago basin using hvsr and cross correlation of ambient seismic noise abstract continuously recorded seismic ambient noise is used to investigate the intermediate and deep structure of the santiago basin for seismic site response evaluation single station h v spectral ratios hvsr were used as a proxy to identify zones with high stiffness soils and low impedance contrast with the underlying bedrock as a complement of available surface geology information frequency domain cross correlation of the vertical components of ambient noise were calculated and used to estimate phase velocity dispersion curves associated to station pairs over different soil deposits in addition noise correlation functions ncfs calculated from time domain cross correlation of the vertical seismic noise records were used to estimate group velocity dispersion curves and to verify results from the spectral method data processing from both methods resolves a frequency band between 0 1 and 8 0 hz a critical band for civil infrastructure that is difficult to determine with traditional local scale passive surface wave methods station pairs with high signal correlation over stiff soils in the center south and east part of the basin mainly associated to flat hvsr response yielded robust phase velocity dispersion curves that vary approximately from 3 5 km s at 0 1 hz to 1 km s at 4 hz shear wave velocity profiles inverted from the dispersion curves show high average shear wave velocities that also have a pronounced increase rate with depth and a lack of clear soil bedrock interface at depths predicted by available gravimetric data

reconstruction of subsurface structure from ambient seismic noise an example from ketzin germany summary passive seismic interferometry is a new promising methodology for seismic exploration interferometry allows information about the subsurface structure to be extracted from ambient seismic noise in this study we apply the cross correlation technique to approximately 25 hr of recordings of ambient seismic noise at the ketzin experimental co2 storage site germany common source gathers were generated from the ambient noise for all available receivers along two seismic lines by cross correlation of noise records this methodology isolates the interstation green s functions that can be directly compared to active source gathers we show that the retrieved response includes surface waves refracted waves and reflected waves we use the dispersive behaviour of the retrieved surface waves to infer geological properties in the shallow subsurface and perform passive seismic imaging of the subsurface structure by processing the retrieved reflected waves

imaging the active faults with ambient noise passive seismics and its application to characterize the huangzhuang gaoliying fault in beijing area northern china abstract most serious geotechnical problems related to rock engineering are generated by the existence of faults detection of fault especially active faults is the first step to conduct any further in depth studies in faulted rock mass or rock blocks in this paper we investigated the plausibility to image fault zones by passive seismic surveys using recorded ambient noise the test site is in the north suburb of beijing northern china along the south bank of the northwest southeast running wenyuhe river where the nne striking huangzhuang gaoliying fault hgf active in the holocene is crossing in general the results are in good agreement with previous studies using active source seismics conducted in this area along the hgf and existing borehole drillings in the vicinity undoubtedly active source seismic reflection technique is the best technique to image fault in depth with high resolution the drawback is its high cost and the necessity of using explosives a practice usually prohibited in urban settings in contrast passive seismic surveys take the advantage of the ever existing ambient noise source and provide a low cost technique and fast deployment that can locate the fault effectively though the imaging resolution is lower compared to those obtained by active source seismic surveys our passive seismic experiment at the wenyuhe river site demonstrated that this approach is effective especially for those faults with significant normal faulting component and the stratigraphy is significantly different on the two sides crossing the fault line

metabasalts and metagabbros from the llano uplift texas petrologic and geochemical characterization with emphasis on tectonic setting the 1 0 1 2 b y old rocks of the southeastern llano uplift texas include a 7 km thick sequence of amphibolite grade stratified mafic metasedimentary rock packsaddle schist which is intruded by a varied suite of syntectonic and late kinematic intrusions the metasediments contain large blocks of serpentinized peridotite coal creek serpentinite and coarse hornblendite and metagabbro prior to the end of maximum deformation the sequence was intruded by low to medium k2o tholeiitic basalts 0 40 0 72 k2o late kinematic low k2o tholeiitic basalts 0 38 0 40 k2o were intruded as dikes into the folded rocks the coal creek serpentinite contains both syntectonic and late kinematic low k2o tholeiitic metabasalts 0 13 0 36 k2o the llano metabasalts and metagabbros are characterized by low cr 67 378 ppm and ni 36 170 ppm variable rb 1 5 14 7 ppm sr 140 1229 ppm tio2 0 40 2 20 p 568 2707 ppm and zr 18 230 ppm and y 16 45 ppm co 40 57 ppm and sc 36 49 ppm similar to modern morb the metabasalts have la abundances from 7 to 39 times chondritic and exhibit light ree enrichment with la sm n from 1 13 to 1 45 and la yb n from 1 12 to 2 99 the metabasalts show a strong correlation of increasing zr ti and y and decreasing eu eu 1 56 1 00 cao tio2 al2o3 tio2 and mgo mgo feo with increasing ree enrichment lan the llano metabasalts and metagabbros have initial 87sr 86sr 0 7029 0 0001 a likely petrogenetic model for these metabasalts is an island arc in which events from early arc development to final late kinematic intrusion were dominated by tholeiitic volcanism and intrusion the chemical systematics of the llano mafic metaigneous rocks suggest they are products of fractionation of olivine clinopyroxene and plagioclase from more primitive basaltic magmas generated beneath the island arc complex

depth profile investigations of surface modifications of limestone artifacts by laser induced breakdown spectroscopy the study of the degradation mechanisms of materials constituting historical buildings is very relevant in the context of cultural heritage preservation in this work a limestone sample collected from the masonry blocks of the entrance gate of historic castello svevo bari italy was subjected to depth profile elemental analysis of the ablated black crust and the underlying limestone by double pulse laser induced breakdown spectroscopy the specific elemental components were identified and their concentrations along the sample profile analyzed so allowing to identify the boundary between the weathered and unaltered rock the laser induced plasma stability i e the absence of parameter changes during ablation was verified to be constant and not to affect the elemental peak sizes during the entire depth analysis process when the plasma is confined in the ablation crater

characterization and tectonic evolution of a mesoproterozoic island arc in the southern grenville orogen llano uplift central texas abstract integrated field and u pb geochronologic data document the presence and tectonic evolution of a distinct lithotectonic terrane in the southeastern llano uplift here termed the coal creek domain ccd the ccd consists of tonalitic and amphibolitic gneisses foliated gabbroic tonalitic and granodioritic intrusions and the structurally emplaced coal creek serpentinite the oldest rocks in the ccd consist of tonalitic gneisses with protolith crystallization ages of 1326 ma and 1301 ma and pre 1292 ma amphibolitic gneisses all ages are u pb zircon they were intruded by dominantly mafic and intermediate with subordinate amounts of felsic low k plutonic rocks between 1286 ma and 1275 ma high temperature metamorphism and local anatexis that resulted in the formation of gneisses and migmatites occurred between 1301 ma and 1286 ma and is suggested to have occurred at 1292 ma metamorphism at 1256 ma resulted in the growth of zircons in mafic rocks the regional significance of this metamorphic event is unclear but it may be related to dynamothermal metamorphism of the ccd the contemporaneous emplacement of low k gabbro tonalite and granodiorite and their spatial association with serpentinite combined with published geochemical data strongly suggest that the ccd represents an ensimatic arc the coal creek serpentinite is interpreted as a fragment of oceanic crust that formed either basement to the arc or in a related back arc or intra arc setting combined field u pb geochronologic isotopic and geochemical data indicate that the magmatic metamorphic and structural history of the ccd differs from that of coeval rocks elsewhere in the llano uplift the boundary between the ccd and deformed and metamorphosed granitic and supracrustal rocks to the north is a zone of intense mylonitization and polyphase deformation this zone is interpreted as the structural boundary between the arc terrane and units to the north

geochemistry of gases and waters discharged by the mud volcanoes at paterno mt etna italy approximately 20 km south of mt etna craters at the contact between volcanic and sedimentary formations three mud volcanoes discharge co2 rich gases and na cl brines the compositions of gas and liquid phases indicate that they are fed by a hydrothermal system for which temperatures of 100 150 c were estimated by means of both gas and solute geothermometry the hydrothermal system may be associated with co2 rich groundwaters over a large area extending from the central part of etna to the mud volcanoes numerous data on the he ch4 co2 composition of the gases of the three manifestations sampled over the past 5 years indicate clearly that variations are due to separation processes of a co2 rich gas phase from the liquid the effects of these processes have to be taken into account in the interpretation of the monitoring data collected for the geochemical surveillance of etna volcano

roots of etna volcano in faults of great earthquakes abstract results from several seismic methods allow us to sketch the deep structure of etna and its ionian margin under etna a volume of high velocity material is found in a structurally high position the emplacement of this suggests spreading of the surrounding medium just offshore down to the east normal faults penetrate through the upper crust the deeper crustal structure beneath appears upwarped from the basin towards etna juxtaposed with the crust of sicily a thinner crust reaches from the ionian basin under etna and the mantle is upwarped in such a structure magma can then be viewed as a melted lens capping a mantle upwarp at shallow depth rather than in an intracrustal chamber this reduces the conflict between estimates of its volume from excess output of volatiles and short residence times a link in time is indicated between volcanic and seismic activity at a large scale over the millennium the reported ends of episodes of high output rates of magma are followed by the reported occurrences of magnitude 7 earthquakes which caused destruction in southeastern sicily several steep active normal fault have been imaged to a depth of 10 km the crust up to 30 km offshore of the cities of catania and augusta which may be fault planes for such large earthquakes they expand and prolongate the system of the timpe faults on the eastern flank of etna thus linking large scale tectonics offshore with the volcano etna developed together with normal faulting upwarp and spreading during the recent evolution of the former ionian subduction activation of the material at depth at the lateral edge of the slab by vertical motion with extension above could produce the peculiar type of etna magmatism

alteration in the irdp drill hole compared with other drill holes in iceland the overall alteration pattern in the drill hole at reydarfjordur is very similar to alteration patterns observed in icelandic geothermal areas and in low grade metamorphosed basalts in deep crustal sections elsewhere in iceland however more detail is obtained by the study of the irdp drill core than by study of drill cuttings sampled in previous drill holes in iceland a comparatively high fossil thermal gradient is obtained at reydarfjordur by a combination of mineral stability data and the observed occurence of secondary minerals this high gradient is consistent with the measured dike dilation at the drill site and the location of the drill site adjacent to a central volcano

body wave reconstruction from ambient seismic noise correlations in an underground mine abstractthe reconstruction of seismic green s functions from correlations of ambient seismic noise has recently developed as a promising approach for exploring the earth s interiors without the requirement of costly active seismic sources this approach is widely used for imaging the crust at a kilometer scale however few studies report noise based green s function reconstruction at smaller scales in industrial environments we have investigated the possibility of constructing seismic green s functions between sensors in an active underground mine garpenberg sweden by crosscorrelating seismic noise generated by mining activities we have determined with realistic numerical simulations that the mining excavations in an underground mine lead to a regime of strong scattering which is favorable for constructing seismic green s functions by crosscorrelating seismic noise one month of continuous data was recorded by 18 seismic sensors located more than 1 km below surface a variety of broadband 10 3000

meteoric water basalt interactions ii a field study in n e iceland the compositions of rain snow melt spring and geothermal waters from the rift zone of n e iceland can be explained by seaspray addition chemical fractionation at the seawater air interface burning of fossil fuel farming activities purification by partial melting of snow and ice dissolution of basalts and buffering by alteration minerals the dissolution of the rocks appears to be incongruent during solute acquisition spring compositions move through the stability fields of kaolinite and smectite to the laumontite and illite fields all but four of the springs are undersaturated with respect to calcite silica concentrations are compatible with the solubility of basaltic glass the reactions reflected in the spring waters appear to have taken place sealed off from atmospheric co2 after initial saturation the geothermal waters which are recharged by the spring waters are depleted in mg and ca but enriched in carbon and sulfur with respect to dissolution of primary rocks expressions are derived relating dissolution rates of rocks age of groundwaters physical properties of groundwaters and mass transfer the characteristic rock particle radii in the cold water aquifers range from 0 2 to 2 cm and the characteristic crack openings are of the order 0 04 to 0 4 cm using laboratory studies on the icelandic lavas as a guide the residence times of the cold waters in the aquifers can be estimated at 60 days to 4 years the average active surface area of the aquifers enclosing 1000 g of spring water is of the order of 0 6 to 6 m2 and these 1000 g of water have reacted with 0 1 to 1 g of basaltic rocks the same mass of thermal water has interacted with 100 to 300 g of unaltered rocks

reflection images from ambient seismic noise one application of seismic interferometry is to retrieve the impulse response green s function from crosscorrelation of ambient seismic noise various researchers show results for retrieving the surface wave part of the green s function however reflection retrieval has proven more challenging we crosscorrelate ambient seismic noise recorded along eight parallel lines in the sirte basin east of ajdabeya libya to obtain shot gathers that contain reflections we take advantage of geophone groups to suppress part of the undesired surface wave noise and apply frequency wavenumber filtering before crosscorrelation to suppress surface waves further after comparing the retrieved results with data from an active seismic exploration survey along the same lines we use the retrieved reflection data to obtain a migrated reflection image of the subsurface

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

a methodological approach towards high resolution surface wave imaging of the san jacinto fault zone using ambient noise recordings at a spatially dense array we present a new technique for deriving detailed information on seismic velocities of the subsurface material from continuous ambient noise recorded by spatially dense seismic arrays this method uses iterative double beamforming between various subarrays to extract surface wave contributions from the ambient noise data in complex environments with unfavourable noise source distributions the iterative double beamforming extraction makes it possible to retrieve large amounts of rayleigh wave traveltime information in a wide frequency band the method is applied to data recorded by a highly dense nodal array with 1108 vertical geophones centred on the damage zone of the clark branch of the san jacinto fault zone south of anza california the array covers a region of 650 700 m 2 with instrument spacing of 10 30 m and continuous recording at 500 samples s 1 over 30 d in 2014 using this iterative double beamforming on subarrays of 25 sensors and cross correlations between all of the station pairs we separate surface waves from body waves that are abundant in the raw cross correlation data focusing solely on surface waves maps of traveltimes are obtained at different frequencies with unprecedented accuracy at each point of a 15 m spacing grid group velocity inversions at 2 4 hz reveal depth and lateral variations in the structural properties within and around the san jacinto fault zone in the study area this method can be used over wider frequency ranges and can be combined with other imaging techniques such as eikonal tomography to provide unprecedented detailed structural images of the subsurface material

surface wave tomography from microseisms in southern california received 5 april 2005 revised 23 may 2005 accepted 9 june 2005 published 26 july 2005 1 since it has already been demonstrated that point topoint seismic propagation green functions can be extracted from seismic noise it should be possible to image earth structure using the ambient noise field seismic noise data from 148 broadband seismic stations in southern california were used to extract the surface wave arrival times between all station pairs in the network the seismic data were then used in a simple but densely sampled tomographic procedure to estimate the surface wave velocity structure within the frequency range of 0 1 0 2 hz for a region in southern california the result compares favorably with previous estimates obtained using more conventional and elaborate inversion procedures this demonstrates that coherent noise field between station pairs can be used for seismic imaging purposes citation sabra k g p gerstoft p roux w a kuperman and m c fehler 2005 surface wave tomography from microseisms in southern california geophys res lett 32 l14311 doi 10 1029 2005gl023155

3d s wave velocity imaging of a subsurface disturbed by mining using ambient seismic noise abstract seismic interferometry based on ambient seismic noise was used to image the 3d s wave velocity field of a subsurface disturbed by mining under the geological conditions at the kghm rudna copper mine in southwestern poland we recorded ambient seismic noise data for 3 months using 11 surface mounted broadband seismometers located across the mining area we used ambient noise cross correlation techniques to create a three dimensional s wave velocity model of the cenozoic and triassic formations up to a depth of 500 m cross correlation functions ccfs indicate the rayleigh and love waves however only the love waves in the 0 19 0 4 hz frequency range were reliable based on the symmetry of the ccfs in the positive and negative conditions imaging using the love waves indicated that the changes in the s wave velocity field in the model may be explained by the subsidence processes occurring above the mined area the s wave velocity decreased above the areas of the current mining operations however the s wave velocity increased above older mined areas probably due to suppression of the subsidence process and progressive consolidation of the geological medium over time we also observed low velocity anomalies in the intersection zones of the larger faults with high energy seismic events this could be caused by fault activation by current mining operations and a reduction in the stiffness of the layers in the fault intersection zone this study presents the possibility of imaging the subsurface layers in a mining area using ambient seismic noise it also has the potential to give a broader insight into how a geological medium responds to mining in terms of protecting the terrain surface and developing mining technologies

efficacy of laser cleaning in the removal of biological patina on the volcanic scoria of the rock hewn churches of lalibela ethiopia the lalibela rock hewn churches are one of the most important religious pilgrimage sites in ethiopia these churches are carved from the scoriaceous basalt rock substrate which has been exposed to attack by biological agents with significant loss of surface material particularly the widespread growth of lichens and other microorganisms on the carved surfaces of the churches has proven to represent a substantial threat for the preservation of the site in this study laboratory tests have been conducted to assess the feasibility of using laser technology as an efficient cleaning method of biological patina from polymineralic stone substrates multi analytical techniques were applied for the characterization of the stone samples collected from two of the lalibela churches bete giyorgis and bete amanuel stone samples artificially inoculated with bacteria yeast fungi isolates and lichen encrusted samples were laser cleaned using uv and ir laser wavelengths the high content of fe and ti oxides and the high porosity have made the stone surfaces easily susceptible to low energy laser treatment results indicate that laser cleaning can be applied to polymineralic lithotypes and uv irradiation can successfully remove lichen colonies further studies need to be conducted to optimize the laser procedure in polymineralic high porosity stones

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

the weathering of basalt and relative mobilities of the major elements at belbex france abstract a basalt and its weathered profile have been analysed for major elements graphical examination shows al fe and ti to have been essentially immobile determining mobility sequences for this deposit is complicated by the long pedogenetic history of the area three different sequences are presented two for different stages of weathering integrated over time and one that reflects the weathering regime of the present day

variability of alkali and heavy metal fluxes released by mt etna volcano sicily between 1991 and 1995 abstract we regularly collected volcanic gases and aerosols at mt etna volcano over a long period 1991 1995 and measured their chemical composition by icp ms based on these data we present new evidence on the high volatility of both alkali and some heavy metals in contrast both lanthanides and actinides are not produced as significant gaseous compounds at magmatic temperatures and can be used as tracers of spattered materials all metals of each chemical family maintained systematic trends during the study period at both summit craters and effusive vents located in the valle del bove during the 1991 1993 eruption during the eruption we observed high metal enrichments at effusive vents these enrichments seem to be characteristic of the secondary degassing of a magma previously degassed under the summit area lower metal enrichments are recorded in aerosols sampled in summit crater plumes according to the primary degassing type occurring at these vents while a primary degassing type still occurs at both bocca nuova and voragine during the post eruptive period sud est crater exhibits a transition from primary to secondary type according to the variations of the volcanic activity level we confirm that the alkali metals fractionate systematically within their family as they cross the melt vapour interface the heavier members being always more enriched than the lighter ones in aerosols we also show that this fractionation is not related to the volcanic activity and the degassing type but seems to be a significant feature of the alkali family itself estimation of new emanation coefficients for rubidium caesium tin and thallium 0 07 0 15 0 50 and 21 respectively yields annual outputs around 1000 t yr 60 t yr 240 t yr and 1600 t yr respectively mount etna is a very important source of metals injected into the atmosphere contributing to the global volcanic budget about 16 for heavy metals and 19 for alkali metals in eruptive periods and only 2 and 4 respectively in quiet periods

mesoproterozoic plate tectonics a collisional model for the grenville aged orogenic belt in the llano uplift central texas the llano uplift of central texas united states exposes the core of a mesoproterozoic orogenic belt that formed along the southern margin of laurentia during grenville time a new collisional model is proposed that reconciles differences in structural stacking apparent tectonic transport and deformation conditions between the eastern and western portions of the uplift and explains uplift and exhumation of high pressure eclogitic rocks emplacement of ophiolitic rocks and subsequent late stage to postcollisional plutonism our model proposes that subduction with southward polarity resulted in collision of an exotic arc with laurentia emplacement of ophiolitic rocks and telescoping of the intervening basinal sediments followed by overriding of the arc and margin of laurentia by a southern continent with transport toward laurentia the model further proposes that convergence led to subduction of the laurentian margin resulting in high pressure metamorphism but buoyancy forces due to subduction of continental crust under the southern continent resulted in uplift and retrotransport away from laurentia in a manner similar to that proposed for the alpine orogeny slab breakoff resulted in upwelling of the asthenosphere leading to intrusion of juvenile granitic plutons subduction along strike caused continued contraction that waned with time the eastern uplift records continent arc continent collision whereas the western uplift records continent continent collision the two regions also expose different crustal levels in the orogen the striking similarity with phanerozoic orogens including emplacement of ophiolites and formation of high pressure rocks implies that plate tectonic processes including subduction were active prior to the neoproterozoic

dissolution of primary minerals in natural waters abstract the saturation state of olivine plagioclase clinopyroxene orthopyroxene fe ti oxides and apatite of variable composition has been assessed in natural waters in iceland with temperature ranging from 0 c to 300 c and in situ ph from below 5 to above 10 cold waters are undersaturated with respect to olivine orthopyroxene clinopyroxene and plagioclases indicating that all these minerals tend to dissolve under weathering conditions with increasing ph and temperature the waters approach saturation with pyroxene olivine and plagioclases also the degree of undersaturation of olivine and orthopyroxene decreases with increasing fe content of the minerals and fe rich olivine and orthopyroxene are stable between 50 c and 150 c whereas mg rich ones tend to dissolve natural waters in iceland are saturated with respect to pure albite when above 50 c they are on the other hand undersaturated with ca rich plagioclase up to 250 c where the waters reach saturation pure magnetite and hematite are stable at all temperatures with increasing titanium content the minerals become unstable and the waters are undersaturated with respect to pure ulvospinel at temperatures up to 300 c pure ilmenite is however close to saturation under weathering conditions but undersaturated above 200 c f apatite is close to saturation at all temperatures on the other hand undersaturation with respect to oh apatite is observed at all temperatures the weathering susceptibilities of primary minerals of basalt in icelandic waters in increasing order are mg olivine fe olivine ti rich magnetite ca plagioclase mg orthopyroxene fe orthopyroxene clinopyroxene na plagioclase f apatite ti rich ilmenite ti poor magnetite ti poor hematite

quaternary tectonic faulting in the eastern united states abstract paleoseismological study of geologic features thought to result from quaternary tectonic faulting can characterize the frequencies and sizes of large prehistoric and historical earthquakes thereby improving the accuracy and precision of seismic hazard assessments greater accuracy and precision can reduce the likelihood of both underprotection and unnecessary design and construction costs published studies proposed quaternary tectonic faulting at 31 faults folds seismic zones and fields of earthquake induced liquefaction phenomena in the appalachian mountains and coastal plain of the 31 features seven are of known origin four of the seven have nontectonic origins and the other three features are liquefaction fields caused by moderate to large historical and holocene earthquakes in coastal south carolina including charleston the central virginia seismic zone and the newbury massachusetts area however the causal faults of the three liquefaction fields remain unclear charleston has the highest hazard because of large holocene earthquakes in that area but the hazard is highly uncertain because the earthquakes are uncertainly located of the 31 features the remaining 24 are of uncertain origin they require additional work before they can be clearly attributed either to quaternary tectonic faulting or to nontectonic causes of these 24 14 features most of them faults have little or no published geologic evidence of quaternary tectonic faulting that could indicate the likely occurrence of earthquakes larger than those observed historically three more features of the 24 were suggested to have had quaternary tectonic faulting but paleoseismological and other studies of them found no evidence of large prehistoric earthquakes the final seven features of uncertain origin require further examination because all seven are in or near urban areas they are the moodus seismic zone hartford connecticut dobbs ferry fault zone and mosholu fault new york city lancaster seismic zone and the epicenter of the shallow cacoosing valley earthquake lancaster and reading pennsylvania kingston fault central new jersey between new york and philadelphia and everona fault mountain run fault zone washington d c and arlington and alexandria virginia